Neuro-Ophthalmology & Neuro-Otology

Color-flow imaging (triplex ultrasound) ultrasound examination after balloon angioplasty of the right subclavian artery shows normal, antegrade flow in the right vertebral artery.

Abbreviations: RVA=right vertebral artery.

(Source: Bajko Z, Motataianu A, Stoian A, et al. Prevalence and clinical characteristics of subclavian steal phenomenon/syndrome in patients with acute ischemic stroke. J Clin Med 2021;10[22]:5237. Creative Commons Attribution [CC BY] License, https://creativecommons.org/licenses/by/4.0.)

Color-flow imaging (triplex ultrasound) ultrasound examination after balloon angioplasty of the right subclavian artery shows a normal triphasic subclavian waveform.

Abbreviations: RSCA=right subclavian artery.

(Source: Bajko Z, Motataianu A, Stoian A, et al. Prevalence and clinical characteristics of subclavian steal phenomenon/syndrome in patients with acute ischemic stroke. J Clin Med 2021;10[22]:5237. Creative Commons Attribution [CC BY] License, https://creativecommons.org/licenses/by/4.0.)

B-mode (brightness mode) ultrasound examination after balloon angioplasty of the right subclavian artery reveals significantly reduced stenosis.

Abbreviations: RSCA=right subclavian artery.

(Source: Bajko Z, Motataianu A, Stoian A, et al. Prevalence and clinical characteristics of subclavian steal phenomenon/syndrome in patients with acute ischemic stroke. J Clin Med 2021;10[22]:5237. Creative Commons Attribution [CC BY] License, https://creativecommons.org/licenses/by/4.0.)

Color-flow imaging (triplex ultrasound) of the right vertebral artery after release of a blood pressure cuff shows complete flow inversion for the entire cardiac cycle during reactive hyperemia of the arm in a 43-year-old man evaluated for repeated transient ischemic attacks in the vertebrobasilar territory.

Abbreviations: RVA=right vertebral artery.

(Source: Bajko Z, Motataianu A, Stoian A, et al. Prevalence and clinical characteristics of subclavian steal phenomenon/syndrome in patients with acute ischemic stroke. J Clin Med 2021;10[22]:5237. Creative Commons Attribution [CC BY] License, https://creativecommons.org/licenses/by/4.0.)

Color-flow imaging (triplex ultrasound) of the right vertebral artery during compression of the right arm with a blood pressure cuff (a "cuff test") shows the appearance of a minimal positive diastolic flow in a 43-year-old man evaluated for repeated transient ischemic attacks in the vertebrobasilar territory.

Abbreviations: RVA=right vertebral artery.

(Source: Bajko Z, Motataianu A, Stoian A, et al. Prevalence and clinical characteristics of subclavian steal phenomenon/syndrome in patients with acute ischemic stroke. J Clin Med 2021;10[22]:5237. Creative Commons Attribution [CC BY] License, https://creativecommons.org/licenses/by/4.0.)

Color-flow imaging (triplex ultrasound) of the right vertebral artery reveals retrograde midsystolic and no diastolic flow in a 43-year-old man evaluated for repeated transient ischemic attacks in the vertebrobasilar territory.

Abbreviations: RVA=right vertebral artery.

(Source: Bajko Z, Motataianu A, Stoian A, et al. Prevalence and clinical characteristics of subclavian steal phenomenon/syndrome in patients with acute ischemic stroke. J Clin Med 2021;10[22]:5237. Creative Commons Attribution [CC BY] License, https://creativecommons.org/licenses/by/4.0.)

Color-flow imaging (triplex ultrasound) shows severely elevated peak systolic flow velocities in the right subclavian artery of a 43-year-old man evaluated for repeated transient ischemic attacks in the vertebrobasilar territory.

Abbreviations: RSCA=right subclavian artery, BRA=brachiocephalic artery.

(Source: Bajko Z, Motataianu A, Stoian A, et al. Prevalence and clinical characteristics of subclavian steal phenomenon/syndrome in patients with acute ischemic stroke. J Clin Med 2021;10[22]:5237. Creative Commons Attribution [CC BY] License, https://creativecommons.org/licenses/by/4.0.)

Duplex scan (color mode) shows a hypoechoic atherosclerotic plaque at the origin of the right subclavian artery causing severe stenosis with turbulent flow in a 43-year-old man evaluated for repeated transient ischemic attacks in the vertebrobasilar territory.

Abbreviations: RCCA=right common carotid artery, RSCA=right subclavian artery, BRA=brachiocephalic artery.

(Source: Bajko Z, Motataianu A, Stoian A, et al. Prevalence and clinical characteristics of subclavian steal phenomenon/syndrome in patients with acute ischemic stroke. J Clin Med 2021;10[22]:5237. Creative Commons Attribution [CC BY] License, https://creativecommons.org/licenses/by/4.0.)

B-mode (brightness mode) ultrasound examination shows a hypoechoic atherosclerotic plaque at the origin of the right subclavian artery causing severe stenosis in a 43-year-old man evaluated for repeated transient ischemic attacks in the vertebrobasilar territory.

Abbreviations: RCCA=right common carotid artery, RSCA=right subclavian artery, BRA=brachiocephalic artery.

(Source: Bajko Z, Motataianu A, Stoian A, et al. Prevalence and clinical characteristics of subclavian steal phenomenon/syndrome in patients with acute ischemic stroke. J Clin Med 2021;10[22]:5237. Creative Commons Attribution [CC BY] License, https://creativecommons.org/licenses/by/4.0.)

The proximal part of left subclavian is blocked on the left side. Blood flow is antegrade in the right vertebral artery but retrograde in the left vertebral artery, which supplies the distal left subclavian artery. (Courtesy of Wikimedia Commons. Illustration by User:Rajtheja on July 5, 2013. Creative Commons Attribution-Share Alike 3.0 Unported License, https://creativecommons.org/licenses/by-sa/3.0/deed.en.)

Chest CT with subclavian artery plaque (red circle) and no contrast in left vertebral artery suggests reversal of flow. (Courtesy of Jason Robert Young MD. Creative Commons Attribution 4.0 International [CC BY 4.0] License, https://creativecommons.org/licenses/by/4.0.)

Left subclavian artery stent placed (green circle) with improved distal blood flow (red arrow) and contrast extending into the left vertebral artery (green arrow). (Courtesy of Jason Robert Young MD. Creative Commons Attribution 4.0 International [CC BY 4.0] License, https://creativecommons.org/licenses/by/4.0.)

Angiogram of the aortic arch shows plaque in the left subclavian artery (red circle) with decreased blood flow distally (purple arrow) and no contrast extending into the left vertebral artery. (Courtesy of Jason Robert Young MD. Creative Commons Attribution 4.0 International [CC BY 4.0] License, https://creativecommons.org/licenses/by/4.0.)

Postoperative follow-up duplex imaging of the right vertebral artery shows oscillation of flow after bypass with stenting in a 72-year-old woman with innominate artery occlusion and subclavian steal syndrome. (Source: George JM, Cooke PV, Ilonzo N, Tadros RO, Grossi RJ. Management of innominate artery occlusion with severe left common carotid artery stenosis. Cureus 2021;13[11]:e19592. Creative Commons Attribution 4.0 International [CC BY 4.0] License, https://creativecommons.org/licenses/by/4.0.)

Postoperative follow-up duplex imaging shows a patent left carotid to right carotid artery bypass graft in a 72-year-old woman with innominate artery occlusion and subclavian steal syndrome. (Source: George JM, Cooke PV, Ilonzo N, Tadros RO, Grossi RJ. Management of innominate artery occlusion with severe left common carotid artery stenosis. Cureus 2021;13[11]:e19592. Creative Commons Attribution 4.0 International [CC BY 4.0] License, https://creativecommons.org/licenses/by/4.0.)

Carotid angiogram after stenting in a 72-year-old woman with innominate artery occlusion and subclavian steal syndrome demonstrates resolution of the left carotid stenosis. The sheath is within the left common carotid artery in a retrograde fashion after carotid cutdown. (Source: George JM, Cooke PV, Ilonzo N, Tadros RO, Grossi RJ. Management of innominate artery occlusion with severe left common carotid artery stenosis. Cureus 2021;13[11]:e19592. Creative Commons Attribution 4.0 International [CC BY 4.0] License, https://creativecommons.org/licenses/by/4.0.)

Arch aortogram in a 72-year-old woman reveals complete occlusion of the innominate artery (black arrow) with delayed filling and severe stenosis of the left common carotid artery (white arrow). (Source: George JM, Cooke PV, Ilonzo N, Tadros RO, Grossi RJ. Management of innominate artery occlusion with severe left common carotid artery stenosis. Cureus 2021;13[11]:e19592. Creative Commons Attribution 4.0 International [CC BY 4.0] License, https://creativecommons.org/licenses/by/4.0.)

Right transradial angiogram in a 72-year-old woman demonstrates innominate occlusion with filling of the right subclavian (black arrow) and the right common carotid (white arrow) arteries. (Source: George JM, Cooke PV, Ilonzo N, Tadros RO, Grossi RJ. Management of innominate artery occlusion with severe left common carotid artery stenosis. Cureus 2021;13[11]:e19592. Creative Commons Attribution 4.0 International [CC BY 4.0] License, https://creativecommons.org/licenses/by/4.0.)

Right transradial angiogram in a 72-year-old woman demonstrates innominate occlusion with filling of the right subclavian (black arrow) and the right common carotid (white arrow) arteries. (Source: George JM, Cooke PV, Ilonzo N, Tadros RO, Grossi RJ. Management of innominate artery occlusion with severe left common carotid artery stenosis. Cureus 2021;13[11]:e19592. Creative Commons Attribution 4.0 International [CC BY 4.0] License, https://creativecommons.org/licenses/by/4.0.)

Carotid duplex imaging shows sustained reversed flow in the right vertebral artery in a 72-year-old woman with innominate artery occlusion and subclavian steal syndrome. (Source: George JM, Cooke PV, Ilonzo N, Tadros RO, Grossi RJ. Management of innominate artery occlusion with severe left common carotid artery stenosis. Cureus 2021;13[11]:e19592. Creative Commons Attribution 4.0 International [CC BY 4.0] License, https://creativecommons.org/licenses/by/4.0.)

CT reconstruction shows almost complete occlusion at the origin of the subclavian artery in an 82-year-old man with left subclavian artery stenosis and subclavian steal phenomenon. (Source: Amano Y, Watari T. "Asymptomatic" subclavian steal syndrome. Cureus 2021;13[10]:e19109. Creative Commons Attribution 4.0 International [CC BY 4.0] License, https://creativecommons.org/licenses/by/4.0.)

Audiogram showing a low-frequency trough pattern of sensorineural hearing loss, commonly seen in Meniere disease. The left ear is shown. (Contributed by James Lanska.)

Air travels in a retrograde fashion due to severe tricuspid regurgitation forcing air back into the superior vena cava where it ascends into the jugular veins and intracranial venous structures. (Source: Santucci J, Mullaguri N, Battineni A, Guddeti RR, Newey CR. Paradoxical and retrograde air embolism from pressurized peripheral bolus. Case Rep Neurol Med 2021;2021:1063264. Copyright 2020 Cleveland Clinic Foundation. Creative Commons Attribution 4.0 International License [CC BY 4.0], https://creativecommons.org/licenses/by/4.0.)

Pathway of air emboli paradoxically traveling from the right atrium across an intracardiac shunt (eg, patent foramen ovale) into the left atrium and subsequently into the left ventricle and aorta before entering the carotid and then intracranial arteries. (Source: Santucci J, Mullaguri N, Battineni A, Guddeti RR, Newey CR. Paradoxical and retrograde air embolism from pressurized peripheral bolus. Case Rep Neurol Med 2021;2021:1063264. Copyright 2020 Cleveland Clinic Foundation. Creative Commons Attribution 4.0 International License [CC BY 4.0], https://creativecommons.org/licenses/by/4.0.)

CT angiography of the head and neck shows a small right apical pneumothorax (solid arrow) and pneumomediastinum (nonsolid arrows). (Source: Morales G, Fiero M, Albert J, Di Gennaro J, Gerbino A. Cerebral arterial gas embolism due to helium inhalation from a high-pressure gas cylinder. Case Rep Emerg Med 2022;2022. Creative Commons Attribution 4.0 International License [CC BY 4.0].)

Chest x-ray upon admission to the emergency department demonstrates pneumomediastinum without pneumothorax (solid arrows). (Source: Morales G, Fiero M, Albert J, Di Gennaro J, Gerbino A. Cerebral arterial gas embolism due to helium inhalation from a high-pressure gas cylinder. Case Rep Emerg Med 2022;2022. Creative Commons Attribution 4.0 International License [CC BY 4.0].)

EEG showing focal spikes and diffuse slow waves in a patient with lung cancer and spontaneous cerebral gas emboli. (Source: Inatomi S, Izumi T, Eura N, et al. Electroencephalographic findings after convulsive seizures due to cerebral arterial air embolism secondary to lung cancer: a case report. J Med Case Rep 2022;16[1]:137. Creative Commons Attribution 4.0 International License [CC BY 4.0], https://creativecommons.org/licenses/by/4.0.)

Findings on susceptibility-weighted imaging from a head MRI in a patient with lung cancer and spontaneous cerebral gas emboli. Small dot-like low signal (circles) in the right frontal cortex (left image) and the left parietal subcortex (right image) on susceptibility-weighted imaging. (TR/TE). (Source: Inatomi S, Izumi T, Eura N, et al. Electroencephalographic findings after convulsive seizures due to cerebral arterial air embolism secondary to lung cancer: a case report. J Med Case Rep 2022;16[1]:137. Creative Commons Attribution 4.0 International License [CC BY 4.0], https://creativecommons.org/licenses/by/4.0.)

Findings on diffusion-weighted images from a head MRI in a patient with lung cancer and spontaneous cerebral gas emboli. Head MRI showing faint hyperintensity (circle) along the right parietal cortex and subcortex and the left frontal cortex on diffusion-weighted images. (Source: Inatomi S, Izumi T, Eura N, et al. Electroencephalographic findings after convulsive seizures due to cerebral arterial air embolism secondary to lung cancer: a case report. J Med Case Rep 2022;16[1]:137. Creative Commons Attribution 4.0 International License [CC BY 4.0], https://creativecommons.org/licenses/by/4.0.)

Findings on head CT in a patient with lung cancer and spontaneous cerebral gas emboli. Head CT image taken on day 1 showing multiple air-densities (circles) in the right cortex and the subcortex bilaterally. (Source: Inatomi S, Izumi T, Eura N, et al. Electroencephalographic findings after convulsive seizures due to cerebral arterial air embolism secondary to lung cancer: a case report. J Med Case Rep 2022;16[1]:137. Creative Commons Attribution 4.0 International License [CC BY 4.0], https://creativecommons.org/licenses/by/4.0.)

Findings on chest and abdominal CT in a patient with lung cancer and spontaneous cerebral gas emboli. (A) Chest CT image showing a left pulmonary hilar mass invading the left atrium and the left main bronchus. (B) Air densities (arrow) inside the tumor. (C) Abdominal CT image showing air densities (arrow) around the intestinal wall. (Source: Inatomi S, Izumi T, Eura N, et al. Electroencephalographic findings after convulsive seizures due to cerebral arterial air embolism secondary to lung cancer: a case report. J Med Case Rep 2022;16[1]:137. Creative Commons Attribution 4.0 International License [CC BY 4.0], https://creativecommons.org/licenses/by/4.0.)

Diffusion-weighted sequence of a brain MRI showing findings consistent with diffuse bilateral cortical anoxic injury. (Source: Santucci J, Mullaguri N, Battineni A, Guddeti RR, Newey CR. Paradoxical and retrograde air embolism from pressurized peripheral bolus. Case Rep Neurol Med 2021;2021:1063264. Creative Commons Attribution 4.0 International License [CC BY 4.0], https://creativecommons.org/licenses/by/4.0.)

(Source: Santucci J, Mullaguri N, Battineni A, Guddeti RR, Newey CR. Paradoxical and retrograde air embolism from pressurized peripheral bolus. Case Rep Neurol Med 2021;2021:1063264. Creative Commons Attribution 4.0 International License [CC BY 4.0], https://creativecommons.org/licenses/by/4.0.)

Axial brain CT showing air emboli in the cortical branches of the posterior cerebral, middle, and anterior cerebral arteries (left and center, white arrows), and air in the superior sagittal sinus and cortical veins (right, black arrow). (Source: Santucci J, Mullaguri N, Battineni A, Guddeti RR, Newey CR. Paradoxical and retrograde air embolism from pressurized peripheral bolus. Case Rep Neurol Med 2021;2021:1063264. Creative Commons Attribution 4.0 International license [CC BY 4.0], https://creativecommons.org/licenses/by/4.0.)

Transthoracic echocardiography showing tricuspid valve vegetation (left, white arrow) and location of interatrial septum and patent foramen ovale (right, white arrowhead). There was a large right-to-left shunt through the patent foramen ovale on bubble study with spontaneous opacification of the left atrium and ventricle (right). (Source: Santucci J, Mullaguri N, Battineni A, Guddeti RR, Newey CR. Paradoxical and retrograde air embolism from pressurized peripheral bolus. Case Rep Neurol Med 2021;2021:1063264. Creative Commons Attribution 4.0 International license [CC BY 4.0], https://creativecommons.org/licenses/by/4.0.)

Brain CT without contrast showed multiple low densities in the right occipital lobe (red arrow). (Source: Chen Y, Zheng C, Zeng Q, Zhang F, Tu S, Wu Z. Cerebral air embolism after pigtail catheter drainage for pneumothorax: a case report and review of the literature. Front Surg 2021;8:743051. Creative Commons Attribution 4.0 International License [CC BY 4.0], https://creativecommons.org/licenses/by/4.0.)

A pigtail catheter (small-bore chest tube) was inserted into chest for relief of a pneumothorax (red arrow). (Source: Chen Y, Zheng C, Zeng Q, Zhang F, Tu S, Wu Z. Cerebral air embolism after pigtail catheter drainage for pneumothorax: a case report and review of the literature. Front Surg 2021;8:743051. Creative Commons Attribution 4.0 International License [CC BY 4.0], https://creativecommons.org/licenses/by/4.0.)

Chest x-ray shows evidence of a pneumothorax after removal of a chest tube (red arrows). (Source: Chen Y, Zheng C, Zeng Q, Zhang F, Tu S, Wu Z. Cerebral air embolism after pigtail catheter drainage for pneumothorax: a case report and review of the literature. Front Surg 2021;8:743051. Creative Commons Attribution 4.0 International License [CC BY 4.0], https://creativecommons.org/licenses/by/4.0.)

A chest CT scan showed a 3.7 × 3.0 cm mass in the right lower lung (red arrow). (Source: Chen Y, Zheng C, Zeng Q, Zhang F, Tu S, Wu Z. Cerebral air embolism after pigtail catheter drainage for pneumothorax: a case report and review of the literature. Front Surg 2021;8:743051. Creative Commons Attribution 4.0 International License [CC BY 4.0], https://creativecommons.org/licenses/by/4.0.)

Follow-up brain CT 2 days after percutaneous transhepatic biliary drainage shows a marked increase in the extent of cerebral edema in the right cerebral hemisphere with a midline shift to the left. (Source: Lee JH, Lee HY, Lim MK, Kang YH. Massive cerebral air embolism following percutaneous transhepatic biliary drainage: a case report. Medicine [Baltimore]. 2021;100[52]:e28389. Creative Commons Attribution 4.0 International License [CC BY 4.0], https://creativecommons.org/licenses/by/4.0.)

Magnetic resonance angiography shows no demonstrable steno-occlusive lesions. (Source: Lee JH, Lee HY, Lim MK, Kang YH. Massive cerebral air embolism following percutaneous transhepatic biliary drainage: a case report. Medicine [Baltimore]. 2021;100[52]:e28389. Creative Commons Attribution 4.0 International License [CC BY 4.0], https://creativecommons.org/licenses/by/4.0.)

Arterial spin-labeling perfusion imaging shows that the cerebral blood flow is markedly decreased in the right cerebral hemisphere and mildly decreased in the left frontal lobe. (Source: Lee JH, Lee HY, Lim MK, Kang YH. Massive cerebral air embolism following percutaneous transhepatic biliary drainage: a case report. Medicine [Baltimore]. 2021;100[52]:e28389. Creative Commons Attribution 4.0 International License [CC BY 4.0], https://creativecommons.org/licenses/by/4.0.)

Gradient-echo sequence shows multifocal hypointense "blooming dots" (arrows) in the right frontal and temporal lobes, consistent with residual air bubbles. (Source: Lee JH, Lee HY, Lim MK, Kang YH. Massive cerebral air embolism following percutaneous transhepatic biliary drainage: a case report. Medicine [Baltimore]. 2021;100[52]:e28389. Creative Commons Attribution 4.0 International License [CC BY 4.0], https://creativecommons.org/licenses/by/4.0.)

Fluid-attenuated inversion recovery shows areas of increased signal intensity and cortical swelling, suggestive of acute infarctions. (Source: Lee JH, Lee HY, Lim MK, Kang YH. Massive cerebral air embolism following percutaneous transhepatic biliary drainage: a case report. Medicine [Baltimore]. 2021;100[52]:e28389. Creative Commons Attribution 4.0 International License [CC BY 4.0], https://creativecommons.org/licenses/by/4.0.)

Apparent diffusion coefficient map shows the corresponding low-signal-intensity areas. (Source: Lee JH, Lee HY, Lim MK, Kang YH. Massive cerebral air embolism following percutaneous transhepatic biliary drainage: a case report. Medicine [Baltimore]. 2021;100[52]:e28389. Creative Commons Attribution 4.0 International License [CC BY 4.0], https://creativecommons.org/licenses/by/4.0.)

Brain diffusion-weighted MRI revealed multiple high signal intensities in the right frontal, right parietal, and left frontal (ie, superior frontal gyrus) lobes. (Source: Lee JH, Lee HY, Lim MK, Kang YH. Massive cerebral air embolism following percutaneous transhepatic biliary drainage: a case report. Medicine [Baltimore]. 2021;100[52]:e28389. Creative Commons Attribution 4.0 International License [CC BY 4.0], https://creativecommons.org/licenses/by/4.0.)

Axial abdominopelvic CT shows air bubbles around the biliary stent and percutaneous transhepatic biliary drainage tube (small white arrows). (Source: Lee JH, Lee HY, Lim MK, Kang YH. Massive cerebral air embolism following percutaneous transhepatic biliary drainage: a case report. Medicine [Baltimore]. 2021;100[52]:e28389. Creative Commons Attribution 4.0 International License [CC BY 4.0], https://creativecommons.org/licenses/by/4.0.)

Coronal abdominopelvic CT shows a ruptured hepatic mass with free air and fluid in the perihepatic space (white arrow in upper left). (Source: Lee JH, Lee HY, Lim MK, Kang YH. Massive cerebral air embolism following percutaneous transhepatic biliary drainage: a case report. Medicine [Baltimore]. 2021;100[52]:e28389. Creative Commons Attribution 4.0 International License [CC BY 4.0], https://creativecommons.org/licenses/by/4.0.)

Pulmonary CT angiography reveals large filling defects in the left main and left lobar (upper and lower) pulmonary arteries (arrows), consistent with pulmonary thromboembolism. (Source: Lee JH, Lee HY, Lim MK, Kang YH. Massive cerebral air embolism following percutaneous transhepatic biliary drainage: a case report. Medicine [Baltimore]. 2021;100[52]:e28389. Creative Commons Attribution 4.0 International License [CC BY 4.0], https://creativecommons.org/licenses/by/4.0.)

Initial noncontrast brain CT in a in a 50-year-old woman with recurrent gall bladder cancer shows extensive pneumocephali in the sulci of the right cerebral hemisphere with air densities in the superior frontal sulcus of the left frontal lobe. (Source: Lee JH, Lee HY, Lim MK, Kang YH. Massive cerebral air embolism following percutaneous transhepatic biliary drainage: a case report. Medicine [Baltimore]. 2021;100[52]:e28389. Creative Commons Attribution 4.0 International License [CC BY 4.0], https://creativecommons.org/licenses/by/4.0.)

(July 12, 2019) At the Cosmonaut Hotel crew quarters in Baikonur, Kazakhstan, Expedition 60 crewmembers Luca Parmitano (b 1976), an Italian astronaut of the European Space Agency (foreground), and Andrew ("Drew") Morgan (b 1976) of NASA test out their vestibular systems on tilt tables as part of prelaunch activities. Along with cosmonaut Alexander Aleksandrovich Skvortsov (b 1966) of Roscosmos, they launched July 20, 2019, on a Soyuz MS-13 spacecraft from the Baikonur Cosmodrome in Kazakhstan for a mission to the International Space Station. (Photo credit: Andrey Shelepin/GCTC. Source: NASA/Johnson Space Center [Houston]. NASA ID: jsc2019e039266. Public domain.)

(March 15, 2018) At the Cosmonaut Hotel crew quarters in Baikonur, Kazakhstan, Expedition 55 crewmembers Andrew ("Drew") Feustel (b 1965) of NASA (top) and Richard ("Ricky") Arnold (b 1963) of NASA (bottom) conduct tests of their vestibular systems on tilt tables as part of prelaunch activities. Along with cosmonaut Oleg Germanovich Artemyev (b 1970) of Roscosmos, they launched March 21, 2018, on the Soyuz MS-08 spacecraft from the Baikonur Cosmodrome for a 5-month mission to the International Space Station. (Photo credit: NASA/Victor Zelentsov. Source: NASA/Johnson Space Center [Houston]. NASA ID: jsc2018e025556. Public domain.)

(May 29, 2018) At the Cosmonaut Hotel crew quarters in Baikonur, Kazakhstan, Expedition 56 prime crewmember Alexander Gerst (b 1976), a German astronaut of the European Space Agency, "takes a spin" in a rotating chair to test his vestibular system as part of prelaunch activities. Gerst, astronaut and physician Serena Auñón-Chancellor (b 1976) of NASA, and cosmonaut Sergey Prokopyev (b 1975) of Roscosmos launched June 6, 2018, from the Baikonur Cosmodrome in Kazakhstan on a Soyuz MS-09 spacecraft for a 6-month mission on the International Space Station. (Photo credit: NASA/Victor Zelentsov. Source: NASA/Johnson Space Center [Houston]. NASA ID: jsc2018e050828. Public domain.)

(December 11, 2017) At the Cosmonaut Hotel crew quarters in Baikonur, Kazakhstan, Expedition 54-55 prime crewmember Scott Tingle (b 1965) of NASA tests his vestibular skills on a rotating chair as part of his prelaunch training. Tingle, astronaut and physician Norishige Kanai (b 1976) of the Japan Aerospace Exploration Agency (JAXA), and cosmonaut Anton Nikolaevich Shkaplerov (b 1976) of the Russian Federal Space Agency (Roscosmos) launched December 17, 2017, on a Soyuz MS-07 spacecraft from the Baikonur Cosmodrome for a 5-month mission on the International Space Station. Photo credit: Andrey Shelepin/Gagarin Cosmonaut Training Center. (Source: NASA/Johnson Space Center [Houston]. NASA ID: jsc2017e137339. Public domain.)

(May 24, 2017) European Space Agency astronaut and French aerospace engineer Thomas Pesquet (b 1978) performs the commissioning of the Gravitational References for Sensorimotor Performance (GRASP) experiment. (Source: NASA/Johnson Space Center [Houston]. NASA ID: ISS051e049152. Public domain.)

(May 24, 2017) European Space Agency astronaut and French aerospace engineer Thomas Pesquet (b 1978) performs the commissioning of the Gravitational References for Sensorimotor Performance (GRASP) experiment on the International Space Station to better understand how the central nervous system integrates information from different sensations. The objective is to better understand the human vestibular system and how it connects to the other sensory organs. (Source: NASA/Johnson Space Center [Houston]. NASA ID: ISS051e049147. Public domain.)

(January 12, 2003) The short-arm centrifuge subjects an astronaut to conflicting sensory input and is used to study the astronaut's perception of motion. It was part of the Spatial Reorientation Following Space Flight investigation conducted on crewmembers. During space flight, the vestibular organs no longer respond in a familiar way. In particular, when astronauts undergo a linear acceleration (eg, bending their heads forward) while in space, their otoliths are not properly stimulated. This creates a sensory conflict, which must be resolved by the brain to maintain orientation. When they first return to Earth, astronauts are again disoriented because of sensory conflict. They undergo a period of spatial reorientation as their brains reconcile what their eyes see and what their vestibular system senses. Recovery can take anywhere from hours to days depending on the length of the mission. (Source: NASA/Marshall Space Flight Center [Redstone Arsenal, Alabama]. NASA ID: 0300115. Public domain.)

(November 1, 1993) Astronaut and surgeon Rhea Seddon (b 1947), STS-58 Payload Commander, spins the Spacelab Life Sciences (SLS-2) rotating chair as Payload Specialist and pathologist Martin J Fettman (b 1956) serves as test subject. The two joined five NASA astronauts for 14 days of medical research aboard the Earth-orbiting Space Shuttle Columbia. (Source: NASA/Johnson Space Center [Houston]. NASA ID: sts058-202-002. Public domain.)

(November 1, 1993) In the Spacelab onboard the Space Shuttle Columbia, STS-58 Commander John Blaha (b 1942) is positioned at the rotating dome vestibular experiment as Payload Commander, and surgeon Rhea Seddon (b 1947) sets up the experiment. (Source: NASA/Johnson Space Center [Houston]. NASA ID: STS058-03-020. Public domain.)

(September 29, 1993) Astronaut and surgeon Rhea Seddon (b 1947), STS-58 Payload Commander, is in a piloting simulator as part of a preflight data collection project concerning neurovestibular function. The seven Spacelab Life Sciences (SLS-2) crew members devoted a full day to miscellaneous biomedical data collection in preparation for a 2-week mission aboard Space Shuttle Columbia. (Source: NASA/Johnson Space Center [Houston]. NASA ID: S93-45373. Public domain.)

(May 6, 1993) Terence T (Tom) Henricks (b 1952), STS-55 pilot, wears a special collar for a space adaptation experiment in the science module onboard the Earth-orbiting Space Shuttle Columbia
(OV-102). The Baroreflex experiment was designed to investigate the theory that lightheadedness and a reduction in blood pressures on standing after landing may arise because the normal reflex system regulating blood pressure behaves differently after having adapted to a microgravity environment. These space-based measurements of the baroreflex were compared to ground measurements to determine how microgravity affects the reflex. (Source: NASA/Johnson Space Center [Houston]. NASA ID: STS055-233-019. Public domain.)

(Jan 30, 1992) Astronaut and physician David C Hilmers (b 1950), STS-42 mission specialist, wearing a helmet assembly, sits in the Microgravity Vestibular Investigation (MVI) rotating chair. The scene is in the International Microgravity Laboratory (IML-1) science module aboard Space Shuttle Discovery. Hilmers, a mission specialist, and six other crewmembers spent more than 8 days in Earth’s orbit conducting experiments. Hilmer's helmet assembly is outfitted with accelerometers to measure head movements and with visors that fit over each eye independently to provide visual stimuli. The chair system has three movement patterns: (1) "sinusoidal," or traveling predictably back and forth over the same distance at a constant speed; (2) "pseudorandom," or moving back and forth over varying distances; and (3) "stepped," or varying speeds beginning and stopping suddenly. (Source: NASA/Johnson Space Center [Houston]. NASA ID: STS042-27-037. Public domain.)

(Jan 30, 1992) Canadian astronaut and neurologist Roberta L Bondar (b 1945), STS-42 Payload Specialist, gets into the Microgravity Vestibular Investigations (MVI) rotator chair to begin an experiment. The chair is mounted in the center aisle of the International Microgravity Laboratory 1 (IML-1) Spacelab module. Just above Bondar's head is the helmet assembly, which is outfitted with accelerometers to measure head movements, and with visors that fit over each eye independently to provide visual stimuli. The chair system has three movement patterns: (1) "sinusoidal" or traveling predictably back and forth over the same distance at a constant speed; (2) "pseudorandom" or moving back and forth over varying distances; and (3) "stepped" or varying speeds beginning and stopping suddenly. (Source: NASA/Johnson Space Center [Houston]. NASA ID: STS042-06-031. Public domain.)

(June 14, 1991) Vestibular experiment activities were captured onboard Columbia's Spacelab Life Sciences (SLS-1) module in this 35 mm scene. Astronaut and physician-engineer James P Bagian (b 1952), STS-40 mission specialist, is in a rotating chair while wearing an accelerometer and electrodes to record head motion and horizontal and vertical eye movements during the rotations. Payload Specialist and molecular biologist Millie Hughes-Fulford (1945-2021), lower left, assisted with the test. She also has electronystagmography contacts on her head, so she was also a participant in some of the experiments. (Source: NASA/Johnson Space Center [Houston]. NASA ID: STS040-211-020. Public domain.)

(June 5, 1991) The laboratory module in the cargo bay of the Space Shuttle Orbiter Columbia was photographed during the Spacelab Life Science-1 (SLS-1) mission. SLS-1 was the first Spacelab mission dedicated solely to life sciences. The main purposes of the SLS-1 mission were (1) to study the mechanisms, magnitudes, and time courses of certain physiological changes that occur during space flight and (2) to investigate the consequences of the body's adaptation to microgravity and readjustment to Earth's gravity. The mission was designed to study the neurovestibular system (ie, involving the interactions of the vestibular system, eyes, and brain) and, particularly, to examine the causes of space motion sickness. The SLS-1 was launched aboard the Space Shuttle Orbiter Columbia
(STS-40) on June 5, 1991. (Source: NASA/Marshall Space Flight Center [Redstone Arsenal, Alabama]. NASA ID: 9135505. Public domain.)

(June 17, 1985) Saudi astronaut and Payload Specialist Sultan Salman Abdelazize Al-Saud (b 1956) participates in the French Postural Experiment on the mid-deck of the Earth-orbiting Space Shuttle Discovery. (Source: NASA/Johnson Space Center [Houston]. NASA ID: 51g-105-030. Public domain.)

(June 17, 1985) The two Payload Specialists for the week-long flight share a mid-deck scene on the Earth-orbiting Space Shuttle Discovery. On the left, Saudi astronaut Sultan Salman Abdelazize Al-Saud (b 1956) is eating a meal, while on the right, French astronaut Patrick Baudry (b 1946) conducts a phase of the French Postural Experiment on himself. Note the electronystagmography electrodes attached at both temples and above and below his right eye. Sleep restraints are in the background. (Source: NASA/Johnson Space Center [Houston]. NASA ID: 51G-102-035. Public domain. Note: based on the NASA description of this image, it was inadvertently inverted by a NASA technician. This has been corrected.)

(November 1, 1983) In this Spacelab-1 mission onboard photograph, astronaut, fighter pilot, and engineer Byron Lichtenberg (b 1948) performs a drop experiment, one of the Vestibular Experiments in Space investigations. The experiment examined spinal reflexes to determine whether they changed in microgravity. In Earth's environment, the otoliths signal the muscles to prepare for jolts associated with falling. During the flight, the normal reflex between the otoliths and the muscles was partially inhibited early in flight, declined further as the flight progressed, and returned to normal after landing, suggesting that the brain ignored or reinterpreted otolith signals during space flight. Crewmembers reported a lack of awareness of position and location of feet, difficulty in maintaining balance, and a perception that falls were more sudden, faster, and harder than similar drops experienced in preflight. Crewmembers experienced illusions as they performed prescribed movement tests. When crew members viewed various targets and then pointed at them while blindfolded, their perception of target location and position of their own limbs was inaccurate in flight compared with similar tests on the ground. Spacelab-1 was launched aboard the Space Shuttle Orbiter Columbia for the STS-9 mission on November 28, 1983. The Marshall Space Flight Center had management responsibilities for the mission. (Source: NASA/Marshall Space Flight Center [Redstone Arsenal, Alabama]. NASA ID: 8440350. Public domain.)

(November 1, 1983) In this photograph, scientist-astronaut and electrical engineer Owen K Garriott (1930-2019) on the body restraint system and astronaut, fighter pilot, and engineer Byron Lichtenberg (b 1948) prepare for a vestibular experiment during the Spacelab-1 mission. The Vestibular Experiments in Space studied the interaction among the otoliths, semicircular canals, vision, and spinal reflexes in humans. The main objective was to determine how the body, which receives redundant information for several sensory sources, interprets this information in microgravity. Another objective was to record and characterize the symptoms of space sickness experienced by crewmembers. The body restraint system was a rotating chair with a harness to hold the test subject in place. The crewmember wore an accelerometer and electrodes to record head motion and horizontal and vertical eye movement as the body rotated. The first Spacelab mission, Spacelab-1, was sponsored jointly and shared equally by NASA and the European Space Agency. Spacelab-1 was launched aboard the Space Shuttle Orbiter Columbia for the STS-9 mission on November 28, 1983. The Marshall Space Flight Center had management responsibilities for the mission. (Source: NASA/Marshall Space Flight Center [Redstone Arsenal, Alabama]. NASA ID: 8440005. Public domain.)

(November 16, 1982) Astronaut Joseph P Allen IV (b 1937), one of two mission specialist astronauts for STS-5, participates in a biomedical test in the middeck area of the Earth-orbiting space shuttle Columbia. A series of electrodes have been connected to his face to monitor his responses in zero-g. He was assisted in the test by astronaut William B Lenoir, the flight’s other mission specialist. Dr. Allen is wearing the multi-pieced constant wear garment for space shuttle astronauts. This frame was exposed with a 35 mm camera. (Source: NASA/Johnson Space Center [Houston]. NASA ID: s05-04-141. Public domain.)

(August 9, 1973) Scientist-astronaut and electrical engineer Owen K Garriott (1930-2019), Skylab 3 science pilot, serves as a test subject for the Skylab Human Vestibular Function M131 experiment, as seen in this image from a television transmission made by a color TV camera aboard the Skylab space station in Earth’s orbit. (Source: NASA/Johnson Space Center [Houston]. NASA ID: S73-32113. Public domain.)

(August 9, 1973) Scientist-astronaut and electrical engineer Owen K Garriott (1930-2019), Skylab 3 science pilot, serves as a test subject for the Skylab Human Vestibular Function M131 experiment in this image from a television transmission made by a color TV camera aboard the Skylab space station in Earth’s orbit. The objectives of the M131 experiment were: (1) assess specific behavioral or physiological responses influenced by vestibular activity under 1-g and zero-g conditions; (2) determine man's adaptability to unusual vestibular conditions and predict habitability of future spacecraft conditions involving reduced gravity and Coriollis forces; and (3) measure the accuracy and variability in man's judgment of spatial coordinates based on atypical gravity receptor cues and inadequate visual cues. Dr. Garriott is seated in the experiment's "litter chair," which can rotate the test subject at predetermined rotational velocity or a programmed acceleration/deceleration profile. (Source: NASA/Johnson Space Center [Houston]. NASA ID: S73-34171. Public domain.)

(March 1,1973) Astronaut Charles Conrad Jr (1930-1999), commander of the first manned Skylab mission, serves as a subject in Human Vestibular Function Experiment M131 during Skylab training at Johnson Space Center. Conrad is in the work-and-experiments compartment of the crew quarters of the Skylab Orbital Workshop (OWS) trainer at Johnson Space Center in Houston. The reference sphere with a magnetic rod is used by the astronaut to indicate body orientation non-visually. The "litter chair" in which he is seated can be rotated by a motor at its base or, when not being rotated, can tilt forward, backward, or to either side. (Source: NASA/Johnson Space Center [Houston]. NASA ID: S73-20695. Public domain.)

(March 1, 1973) Astronaut Charles Conrad Jr (1930-1999), commander of the first manned Skylab mission, serves as a subject in Human Vestibular Function Experiment M131 during Skylab training at Johnson Space Center. Scientist-astronaut and physician Joseph P Kerwin (b 1932), science pilot of the mission, goes over a checklist. The two men are in the work-and-experiments compartment of the crew quarters of the Skylab Orbital Workshop (OWS) trainer at Johnson Space Center in Houston. (Source: NASA/Johnson Space Center [Houston]. NASA ID: S73-20678. Public domain.)

(January 1,1972) The base houses the motor for the rotary chair. Skylab's Human Vestibular Function experiment (M131) was a set of medical studies designed to determine the effect of long-duration space missions on astronauts' coordination abilities. This experiment tested the astronauts' susceptibility to motion sickness in the Skylab environment, acquired data fundamental to an understanding of the functions of human gravity reception under prolonged absence of gravity, and tested for changes in the sensitivity of the semicircular canals. Data from this experiment were collected before, during, and after flight. The Marshall Space Flight Center in Redstone Arsenal, Alabama, had program management responsibility for the development of Skylab experiments. (Source: NASA/Marshall Space Flight Center [Redstone Arsenal, Alabama]. NASA ID: 0102036b. Public domain.)

(January 1, 1972) The control panel is at the upper left. The base houses the motor for the rotary chair. Skylab's Human Vestibular Function experiment (M131) was a set of medical studies designed to determine the effect of long-duration space missions on astronauts' coordination abilities. This experiment tested the astronauts' susceptibility to motion sickness in the Skylab environment, acquired data fundamental to an understanding of the functions of human gravity reception under prolonged absence of gravity, and tested for changes in the sensitivity of the semicircular canals. Data from this experiment were collected before, during, and after flight. The Marshall Space Flight Center in Redstone Arsenal, Alabama, had program management responsibility for the development of Skylab experiments. (Source: NASA/Marshall Space Flight Center [Redstone Arsenal, Alabama]. NASA ID: 0102036b. Public domain.)

(January 1, 1972) Skylab's Human Vestibular Function experiment (M131) was a set of medical studies designed to determine the effect of long-duration space missions on astronauts' coordination abilities. This experiment tested the astronauts' susceptibility to motion sickness in the Skylab environment, acquired data fundamental to an understanding of the functions of human gravity reception under prolonged absence of gravity, and tested for changes in the sensitivity of the semicircular canals. Data from this experiment were collected before, during, and after flight. The Marshall Space Flight Center in Redstone Arsenal, Alabama, had program management responsibility for the development of Skylab experiments. (Source: NASA/Marshall Space Flight Center [Redstone Arsenal, Alabama]. NASA ID: 0102036a. Public domain.)

(January 1, 1970) The Rotating "Litter Chair" was a major component of Skylab's Human Vestibular Function experiment (M131). The experiment was a set of medical studies designed to determine the effect of long-duration space missions on astronauts' coordination abilities. The M131 experiment tested the astronauts' susceptibility to motion sickness in the Skylab environment, acquired data fundamental to an understanding of the functions of human gravity reception under prolonged absence of gravity, and tested for changes in the sensitivity of the semicircular canals. Data from this experiment were collected before, during, and after flight. The Marshall Space Flight Center had program management responsibility for the development of Skylab hardware and experiments. (Source: NASA/Marshall Space Flight Center [Redstone Arsenal, Alabama]. NASA ID: 7026007. Public domain.)

Astronauts and Canadian space medicine researcher and physiologist Douglas Watt (top left) acclimating themselves to space adaptation syndrome in a KC-135 airplane that flies parabolic arcs to create short periods of weightlessness. In 2001 and 2002, Watt of McGill University in Montreal studied how the human body adapts to weightlessness through his H-Reflex experiment. This was the first medical experiment completed on the International Space Station (ISS). (Source: NASA's Marshall Space Flight Center. Public domain.)

Garn did acceptably well in training, including his stint on the KC-135 "Vomit Comet." However, while one of the crew (in green flight suit) is moving about in the zero-g environment and clearly enjoying himself, Garn (at left in orange flight suit) is holding on tensely with both hands and appearing apprehensive. (Source: NASA/Johnson Space Center [Houston]. NASA ID: S85-25619. Public domain. Cropped by Dr. Douglas J Lanska.)

Beginning in 1981, United States Senator Edwin Jacob "Jake" Garn (b 1932), from Utah, pressured NASA to let him fly on a Space Shuttle mission, and in 1985 he was included on the STS-51-D mission of Space Shuttle Discovery. Garn's role was as a congressional observer and as a subject for medical experiments on space motion sickness. Despite having flown more than 10,000 hours as a Navy combat pilot, the space sickness Garn experienced was so severe that a scale for space sickness was jokingly based on him, where "1 Garn" is the highest possible level of sickness. (Source: NASA. Public domain.)

(Source: Post of Moldova. Not subject to copyright.)

Cosmonaut German Titov (right) appears with NASA astronaut John Glenn (left) and President John Kennedy (center) at the White House on May 3, 1962. Titov was in Washington to give his account of the Vostok 2 spaceflight to the Committee on Space Research (COSPAR). (Credit: NASA image from the files of Asif Siddiqi. Source: Siddiqi AA. Challenge to Apollo: The Soviet Union and the Space Race, 1945-1974 [NASA SP-2000-4408]. Washington, DC: NASA History Division, National Aeronautics and Space Administration, 2000. Public domain.)

From left to right: Soviet cosmonaut Gherman Stepanovich Titov (1935-2000); Nikita Sergeyevich Khrushchev (1894-1971), First Secretary of the Communist Party of the Soviet Union; and Soviet cosmonaut Yuri Alekseyevich Gagarin (1934-1968). Gagarin had been the first human to journey into outer space: traveling in the Vostok 1 capsule, Gagarin completed one orbit of Earth on April 12, 1961. Titov became the second human to orbit Earth on August 6, 1961, aboard Vostok 2. Titov is also remembered as the first person to suffer significant space sickness (space orientation syndrome). (Source: Dutch National Archives, The Hague, Fotocollectie Algemeen Nederlands Persbureau (ANEFO), 1945-1989. Creative Commons Attribution-Share Alike 3.0 Netherlands License, https://creativecommons.org/licenses/by-sa/3.0/nl/deed.en.)

Space shuttle “Teacher in Space” astronaut Christa McAuliffe (at top), her backup crew member, Barbara Morgan (bottom), and Payload Specialist Greg Jarvis (top right) training on the KC-135 zero-g aircraft. STS-51-L was the 25th mission of the NASA Space Shuttle program and the final flight of Space Shuttle Challenger. Planned as the first "Teacher in Space" Project, in addition to observing Halley's Comet for 6 days, the mission never achieved orbit; a structural failure during ascent 73 seconds after launch from Kennedy Space Center on January 28, 1986, killed all seven crew members and destroyed the orbiter. Morgan was not onboard the ill-fated STS-51-L mission of the Space Shuttle Challenger; she later trained as a Mission Specialist and flew on the STS-118 mission of Space Shuttle Endeavor in August 2007, more than 20 years after the Challenger disaster. (Source: NASA [S85-44833]. Public domain.)

This August 1995 photo aboard a KC-135 zero-g aircraft carrying that year's class of NASA astronaut candidates depicts the kind of training required to prepare astronauts for flights on assigned missions in space. Those pictured are (from the left, top row) Frederick W Sturckow, Rick D Husband, Dafydd R (Dave) Williams Jr, Stephen K Robinson, Kalpana C Chawla, and Takao Doi and (bottom row, left to right) Michel Tognini, Carlos I Noriega, Susan L Still, Janet L Kavandi, Michael P Anderson, and Joe F Edwards. Doi is representing the National Space Development Agency (NASDA) of Japan; Williams, the Canadian Space Agency (CSA); and Tognini, France's Centre National d'Etudes Spatiales (CNES). Williams joined four other first-time fliers (not pictured) on Space Shuttle Columbia for the April 1998 Neurolab mission. (Source: NASA [S95-09698]. Public domain.)

In this photo from 1978, six astronauts who had been in training at the Johnson Space Center for almost a year are experiencing weightlessness. They are onboard the NASA KC-135, which uses a special parabolic pattern to create brief periods of microgravity, affording astronauts and astronaut candidates a preview of spaceflight. The photo should be viewed with feet at the top. The three astronauts in the foreground are (left to right): Richard O Covey, Steven R Nagal, and George D Nelson. In the center background is Robert L Stewart. Obscured in the background are Norman E Thagard and Ellison S Onizuka. (Source: NASA. Public domain.)

Note the approximate 45-degree angle of ascent. (Source: NASA Image and Video Library [GRC-2001-C-00614]. Public domain.)

Parabolic flight trajectory of the NASA KC-135A 9 from the aircraft nose of "Weightless Wonder IV," Johnson Space Center. (Source: NASA/Glenn Research Center. The present image was created from a photograph of the aircraft nose by Dr. Douglas J Lanska.)

NASA/U.S. Air Force KC-135 aircrew below the aircraft nose, 1995: "Weightless Wonder IV," Johnson Space Center. Note the parabolic flight trajectory painted on the aircraft's nose. (Source: NASA/Glenn Research Center [C-1995-716]. Public domain.)

The KC-135 provided NASA's Reduced Gravity Program with a zero-g environment for testing and training of human reactions (1968). (Source: NASA [NAS-9-9-59279-163125]. Public domain.)

Mercury astronauts in simulated weightless flight in C-131 aircraft flying zero-g trajectory (the "vomit comet") at Wright Air Development Center, 1959. Weightless flights were a new form of training for the Mercury astronauts. These flights were nicknamed the "vomit comet" because of the nausea that is often induced. (Source: NASA. Public domain.)

NASA's Reduced Gravity Research Program made it possible for scientists to study human responses to simulated weightlessness. The reduced-gravity aircraft flies an up-and-down parabolic pattern. This provides about 30 seconds of hypergravity (1.8 to 2.0 g) as the plane climbs to the top of the parabola. Once the aircraft starts to tip over the top of the parabola to descend toward Earth, the aircraft experiences about 25 seconds of microgravity (zero-g). A typical flight conducted 30 to 40 parabolic maneuvers over the Gulf of Mexico. KIAS = knots indicated air speed. (Source: NASA Reduced Gravity Research Program. Because of the poor quality of the original, the figure has been recreated with modified labeling by Dr. Douglas J Lanska.)

Harry Larson, one of the “Gallaudet Eleven" research subjects in the 1950s, inside a 20-foot slow rotation room, rotating at 10 revolutions per minute. (Credits: Gallaudet University Archives/Harry Larson Collection and NASA. Source: Hotovy/NASA 2017.)

John Zakutney, one of the “Gallaudet Eleven" research subjects in the 1950s, being lowered into a centrifuge pool. (Credits: NASA/U.S. Navy/Personal collection of David Myers. Source: Hotovy/NASA 2017.)

The central auditory deficits shown in orange constitute an ensemble of indirect effects presumably common to all forms of congenital peripheral deafness. Other central deficits in blue denote deficits that may be combined in specific genetic forms of congenital deafness. Except for genes playing intrinsic roles in both the central and peripheral auditory systems, all central auditory deficits shown here are indirect consequences of peripheral hearing impairment. The time scale is based on the development of the human auditory system. (Source: Michalski N, Petit C. Central auditory deficits associated with genetic forms of peripheral deafness. Hum Genet 2022;141(3-4):335-45. Creative Commons Attribution 4.0 International License. http://creativecommons.org/licenses/by/4.0.)

Atrioventricular block 10 seconds after swallowing cold water. (Source: Malone K, Modi M, Koripalli S, Amorn A, Stevens CM. Swallow syncope associated with intermittent sinus pause and high-degree atrioventricular block: a case report. Cureus 2022;14(3):e22915. Creative Commons Attribution License [CC-BY 4.0].)

Sinus arrest 5 seconds after the initiation of drinking cold water. (Source: Malone K, Modi M, Koripalli S, Amorn A, Stevens CM. Swallow syncope associated with intermittent sinus pause and high-degree atrioventricular block: a case report. Cureus 2022;14(3):e22915. Creative Commons Attribution License [CC-BY 4.0].)

Overnight ECG showing transient high-grade, second-degree atrioventricular block on a background of 2:1 second-degree atrioventricular block. (Source: Malone K, Modi M, Koripalli S, Amorn A, Stevens CM. Swallow syncope associated with intermittent sinus pause and high-degree atrioventricular block: a case report. Cureus 2022;14(3):e22915. Creative Commons Attribution License [CC-BY 4.0].)

Initial 12-lead ECG on presentation while the patient was at rest. New bifascicular block compared with previous ECG 7 months earlier, which showed only a right bundle branch block. (Source: Malone K, Modi M, Koripalli S, Amorn A, Stevens CM. Swallow syncope associated with intermittent sinus pause and high-degree atrioventricular block: a case report. Cureus 2022;14[3]:e22915. Creative Commons Attribution License [CC-BY 4.0].)

Pendred syndrome is characterized by severe-to-profound congenital deafness and is associated with a large vestibular aqueduct. There may also be a cochlear malformation (Mondini displasia). (Figure prepared by the National Institutes of Health. Public domain. Figure edited by Dr. Douglas J Lanska.)

(Illustration by C Burnett, March 25, 2007. Creative Commons Attribution-Share Alike 3.0 Unported License, https://creativecommons.org/licenses/by-sa/3.0/deed.en. Figure edited by Dr. Douglas J Lanska.)

C-shaped halo of disc edema with normal temporal disc margin and disrupted radial nerve fiber layer striation. (Contributed by Dr. Yue Li.)

Circumferential halo with nasal elevation. No major vessel obscuration. (Contributed by Dr. Yue Li.)

Circumferential halo with general elevation of the optic nerve head. Obscuration of at least one segment of major vessels leaving the disc. (Contributed by Dr. Yue Li.)

Circumferential obscuration of the disc margin with complete elevation of the optic nerve head. Obscuration of more than one major vessel on the disc. (Contributed by Dr. Yue Li.)

The optic disc is elevated with circumferential halo. But all the vessels are not obscured. The disc has a mild refractile appearance. (Contributed by Dr. Yue Li.)

High swelling of the optic nerve head with partial or total obscuration of all vessels on the disc and leaving the disc. (Contributed by Dr. Yue Li.)

(A, C) Enhanced depth imaging OCT scan of the optic nerve with green line corresponding to the cross-sections in (B) and (D), which are showing the visible optic disc drusen (blue arrow). The drusen always has a signal-poor, hyporeflective core and fragments of hyperreflective margins. (Contributed by Dr. Yue Li.)

A 59-year-old woman had severe bilateral vision loss as well as altered sensorium, headaches, and seizures. The blood pressure was 203/180 mmHg. MRI revealed signal abnormality in the bilateral parieto-occipital areas, predominantly in the white matter, without infarction, which is consistent with posterior reversible encephalopathic syndrome. Visual acuity improved following treatment of hypertension. (Contributed by Dr. Sangeeta Khanna.)

A 49-year-old female developed sudden bilateral vision loss after an interventional procedure for embolization for uterine leiomyoma due to thromboembolism. CT revealed hypoattenuating ill-defined areas of low attenuation seen in the occipital lobes bilaterally, more extensive on the right side than the left. MRI showed areas of restricted diffusion with loss of gray-white matter differentiation seen predominantly involving the bilateral occipital lobes. She slowly improved to 20/100 in both eyes with conservative measures. (Contributed by Dr. Sangeeta Khanna.)

MRI demonstrates cerebral edema in affected areas, typically the posterior hemispheres best seen in T2-FLAIR sequence, generally in the absence of restricted diffusion, a sign that would be more characteristic of ischemic infarction. (Contributed by Dr. Sangeeta Khanna.)

Coronal T2-weighted MRI image of a left inferior occipital stroke in a patient with pure alexia and right hemianopia. (Contributed by Dr. Jason J S Barton.)

(Contributed by Dr. Jason J S Barton.)

(Contributed by Dr. Jason J S Barton.)

Cookie Theft Picture from the Boston Diagnostic Aphasia Examination. For the task, the examiner asks subjects to describe the picture by saying, "Tell me everything you see going on in this picture". Then subjects might say, "there is a mother who is drying dishes next to the sink in the kitchen. She is not paying attention and has left the tap on. As a result, water is overflowing from the sink. Meanwhile, two children are attempting to make cookies from a jar when their mother is not looking. One of the children, a boy, has climbed onto a stool to get up to the cupboard where the cookie jar is stored. The stool is rocking precariously. The other child, a girl, is standing next to the stool and has her hand outstretched ready to be given cookies. (Creative Commons Attribution 4.0 International.)

Medieval carving of Saint David, sea-sick during his journey to the holy land, as depicted on a misericord in Saint David's Cathedral in the county of Pembrokeshire, near the most westerly point of Wales. A misericord (or mercy seat) is a small wooden structure on the underside of a folding seat in a church which, when the seat is folded up, is intended to support a person in a partially standing position during long periods of prayer. (Courtesy of the Wellcome Collection, London. Creative Commons 4.0 International license. Image edited by Dr. Douglas Lanska to correct perspective distortion and to repair small areas of damage to the image.)

Audiogram showing a “4 kHz notch” (or colloquially, a “4K notch”) pattern of sensorineural hearing loss, commonly seen in noise-induced hearing loss. Both ears are shown. (Contributed by James Lanska.)

Audiogram showing symmetric, gradually sloping, high-frequency sensorineural hearing loss. (Contributed by James Lanska.)

Audiogram showing a low-frequency trough pattern of sensorineural hearing loss, commonly seen in Meniere disease. The left ear is shown. (Contributed by James Lanska.)

(Contributed by Dr. Rosa Ana Tang.)

(Contributed by Dr. Rosa Ana Tang.)

Comparing ERG responses in dark (scotopic) and light (photopic) conditions. (Contributed by Dr. Rosa Ana Tang.)

Comparison of A- and B-wave ratios in a normal ERG versus abnormal ERG under scotopic (dark) conditions. (Contributed by Dr. Rosa Ana Tang.)

Normal electroretinogram showing the anatomical correlates of the B-wave, oscillatory potential (OP) and A-wave. (Contributed by Dr. Rosa ana Tang.)

(A) Multifocal visual evoked potential stimulus contains 60 sectors of black and white checks (one sector shown in red). (B) Multifocal visual evoked potential responses from the right eye (blue) and the left eye (red) of a normal subject are very similar. (C) The multifocal visual evoked potential responses from the right eye with a history of optic neuritis are delayed in some sectors compared to those from the left eye (red). (D) An interocular latency probability plot marks the locations with significantly delayed latencies in the right eye with an optic neuritis history (dark blue for p < 0.01, light blue for p < 0.05) compared to the left eye. Black symbols denote no significant differences compared to a normative database; small gray symbols denote responses too small for comparisons. (Contributed by Dr. Han Cheng.)

Pattern-reversal visual evoked potential stimulus (A) and waveform (B). (Contributed by Dr. Han Cheng.)

(Contributed by Dr. Rosa Ana Tang.)

A-scan ultrasonogram showing a medial rectus muscle measuring greater than 5.4 mm, suggesting it is minimally enlarged (top figure) as compared to lateral rectus muscle (bottom figure) measuring 7.05 mm, indicative of serious enlargement. (Contributed by Dr. Rosa Ana Tang.)

(Contributed by Dr. Rosa Ana Tang.)

A-scan of optic nerve that shows a change of 28% with 30-degree test, consistent with presence of perioptic fluid (disc edema). (Contributed by Dr. Rosa Ana Tang.)

B-scan of sclera that shows acute scleritis in a patient with eye pain. (Contributed by Dr. Rosa Ana Tang.)

USG B-scan of optic nerve that shows elevated optic nerve head without drusen (Contributed by Dr. Rosa Ana Tang.)

OCT of optic nerve that shows resolution of papilledema 4 months after diagnosis of pseudotumor cerebri and treatment with acetazolamide. (Contributed by Dr. Rosa Ana Tang.)

OCT of right eye shows edema of optic disc after nonarteritic anterior ischemic optic neuropathy. To be noticed is a small cup-to-disc ratio of the contralateral eye, which translates into an increased risk of nonarteritic anterior ischemic optic neuropathy in that eye. (Contributed by Dr. Rosa Ana Tang.)

(Contributed by Dr. Rosa Ana Tang.)

(Contributed by Dr. Rosa Ana Tang.)

(A) Retinal OCT centered on the fovea shows the foveal depression and multiple retinal layers seen. (B) Optic nerve OCT shows a cross-section. (Contributed by Dr. Rosa Ana Tang.)

This 20-year-old man had developmental delay but did well until recently, with some memory decline, dysarthria, and imbalance since his late teens. The video begins with intact horizontal saccades, then vertical saccades that are slow and limited in range, followed by intact horizontal pursuit and then limited vertical pursuit. (Courtesy of www.neuroophthalmology.ca. Contributed by Dr. Jason Barton.)

Cross section of the temporal bone through the external auditory meatus, the tympanic cavity surrounding the bones of the middle ear, the superior and horizontal semicircular canals, and the cochlea. Illustration from Tabula 45 of Bartolomeo Eustachi’s Tabulae Anatomicae (Eustachii 1714).

Woodcut frontispiece portrait of Flemish anatomist, physician, and surgeon Andreas Vesalius (1514-1564) from the Fabrica (1543). (Courtesy of the U.S. National Library of Medicine.)

This photo was taken approximately 2 weeks after several weeks of orbital radiation in daily fractions. The lid is less boggy, and ocular motility and alignment have improved. The patient now has no diplopia in the central 20 degrees of visual field. (Contributed by Dr. Mark Duffy.)

In this axial CT, orbital mass has the appearance of an intraconal tumor. Note the homogeneous appearance of the intraconal tumor and its characteristic molding to the space it occupies. It molds at the globe instead of indenting it, and it molds along the posterior lateral orbital wall without expanding the orbital space, resulting in bony erosion. It extends to the inferior orbital fissure posteriorly. (Contributed by Dr. Mark Duffy.)

Coronal CT shows an inferior orbital mass that displaces the optic nerve. It is in the exact location of the inferior rectus muscle and seems to completely replace it. The other rectus extraocular muscles appear normal bilaterally. Biopsy is indicated to rule out lymphoma versus a primary myositis or vasculitis. (Contributed by Dr. Mark Duffy.)

This 76-year-old man presented with diplopia in all directions of gaze. The right periorbital tissues showed diffuse boggy edema concentrated in the inferior lid. There was significant clear chemosis of the right bulbar conjunctiva. The globe was relatively immobile and displaced superiorly by several millimeters. The differential diagnosis included unilateral thyroid-related orbitopathy, lymphoma, and vasculitis. (Contributed by Dr. Mark Duffy.)

This 8-year-old girl presented with slow progressive ptosis of the left upper lid and fullness to the left periorbital tissues. There was a dense, nonmobile palpable mass over the lacrimal gland area. By imaging, the mass was separate from the lacrimal gland. The dense presumed fibrosis of the orbit had severely limited the movement of the levator palpebrae superioris without affecting the superior or lateral rectus. The patient underwent an orbital biopsy through a lid crease incision. (Contributed by Dr. Mark Duffy.)

After the diagnosis of limited granulomatosis polyangiitis was made, the patient was treated by a pediatric rheumatologist. This photograph was taken 6 weeks after initiation of oral prednisone treatment (note the facial fullness). The ptosis is spontaneously resolving, and the levator excursion has returned to near normal. The orbital mass is no longer palpable. (Contributed by Dr. Mark Duffy.)

This patient underwent urgent apical and orbital decompression. In this axial CT, note the increased space at the orbital apices bilaterally. This relief of optic nerve compression was associated with return of significant visual acuity and color vision. (Contributed by Dr. Mark Duffy.)

Coronal sections identify the classic enlargement of extraocular muscle bellies. The most common muscles involved (in order and degree) are the inferior rectus, medial rectus, superior rectus, and lateral rectus, in that order. In this case, it appears the superior oblique muscles may even be slightly enlarged. The lateral rectus is rarely enlarged to a significant degree. This is a classic presentation of extreme diffuse muscle enlargement resulting in compressive optic neuropathy. (Contributed by Dr. Mark Duffy.)

(A) Visual field testing of the left eye at presentation. In the visual field of the left eye, defects include an inferior nasal step and an inferior altitudinal defect to less visible stimuli. The right eye shows similar defects. (B) Following 1 week of treatment with prednisone 100 mg/day, repeat examination shows progression of visual field loss in the left eye. There is now a dense paracentral scotoma (likely an evolving cecocentral scotoma) and increased definition of the inferior nasal step. Also of note is the increasing constriction of isopters to the larger or brighter stimuli. (Contributed by Dr. Mark Duffy.)

This 72-year-old man with a history of hypothyroidism presented with complaints of blurred vision and chronic swelling of the eyes. He had been treated for 2 months with vasoconstrictors and antibiotic ointment for a presumed chronic conjunctivitis before referral to an eye center. (Contributed by Dr. Mark Duffy.)

On this axial CT, the apex is seen to be completely crowded out by the rectus muscle bellies. Proptosis, increased orbital fat, and extraocular muscular enlargement are present. (Contributed by Dr. Mark Duffy.)

A 54-year-old female presented with a history of progressive proptosis, ptosis, diplopia, and periocular pain over a 6-week interval, despite prednisone treatment. CT scan revealed a mass that indented the globe. Orbital biopsy revealed a dense fibrotic mass consistent with sclerosing orbital pseudotumor. A debulking procedure and release of the superior and medial rectus muscles resulted in return of full motility. High-dose corticosteroid treatment prevented further progression. The ptosis was complete and permanent, requiring a silicone frontalis sling procedure. (Contributed by Dr. Mark Duffy.)

Bone marrow biopsy showing a “foam cell,” cholesterol-laden macrophage, from the patient with Niemann Pick type C from mutation in the NPC1 gene. (Courtesy of www.neuroophthalmology.ca. Contributed by Dr. Jason Barton.)

The optic disc is swollen, and there is subretinal fluid extending to the macula. Extensive patches of retinal edema (white) extend along the upper and lower vascular arcades. (Contributed by Dr. James Goodwin.)

Persons with retinal manifestations of toxoplasmosis may have from three to seven reactivations of the retinochoroiditis during a lifetime. This picture shows an active lesion with the typical cellular deposits in the vitreous. This appearance gives rise to the label of “a headlight in the fog.” (Contributed by Dr. Rosa Tang.)

Central retinal artery occlusion usually presents as a sudden onset of painless and profound visual loss. The condition may be preceded by episodes of transient visual loss. The cause of central retinal artery occlusion is most commonly emboli from the carotid artery or the heart. This patient is showing an unusual sparing of the papillomacular nerve fiber bundle due to a patent cilioretinal artery. Approximately one in four patients with central retinal artery occlusion have significant carotid artery disease, cardiac valvular disease, or diabetes. (Contributed by Dr. Rosa Tang.)

Purtscher retinopathy in a patient with shaken baby syndrome. (Contributed by Dr. Rosa Tang.)

Dutch physician Fredrik Ruysch (1638-1731). (Courtesy of the U.S. National Library of Medicine.)

Italian anatomist Bartolomeo Eustachi (1524-1574). (Courtesy of the U.S. National Library of Medicine.)

The ERG is recorded at the cornea and referenced to the back of the eye. It is a graphic representation of the change in voltage as a function of time following the introduction of a stroboscopic flash presented in a Ganzfield (uniform featureless visual field). Clinical electroretinography is usually done in accordance with standards set forth by the International Society for Clinical Electrophysiology of Vision (ISCEV). The top three ERG records in this figure are normal. 1-R is produced by a bright white flash on a dark field and is both photopic and scotopic in origin. 2-R is produced by the same bright field on a lighted background and is photopic in origin. 3-R is a dim flash on a dark background in a dark-adapted eye. It is purely scotopic in origin. Record 4-R is the response to a scotopic stimulus in a patient with retinitis pigmentosa. (Contributed by Dr. James Walters.)

Although the disc margins appear blurred, the cause is congenital myelination of the nerve fiber layer, which must be distinguished from papilledema. (Contributed by Dr. Sashank Prasad.)

Brain MRI showing a tiny acute infarction in the left parahippocampal gyrus. (From: Liqun Z, Park KH, Kim HJ, Lee SU, Choi JY, Kim JS. Acute unilateral audiovestibulopathy due to embolic labyrinthine infarction. Front Neurol 2018;9:311. Creative Commons Attribution License; CC BY.) (Contributed by Dr. Douglas Lanska.)

Pure-tone audiometry shows symmetric responses between the ears . There is evidence of bilateral symmetric sloping high-frequency sensorineural hearing loss. Lt = left; Rt = right; O= air conduction, unmasked, right ear; < = bone conduction, unmasked, right ear; X = air conduction, unmasked, left ear; > = bone conduction, unmasked, left ear. (From: Liqun Z, Park KH, Kim HJ, Lee SU, Choi JY, Kim JS. Acute unilateral audiovestibulopathy due to embolic labyrinthine infarction. Front Neurol 2018;9:311. Creative Commons Attribution License; CC BY.) (Contributed by Dr. Douglas Lanska.)

Bithermal caloric tests documented complete right canal paralysis. SPV = slow phase velocity, PSPV = peak SPV. (From: Liqun Z, Park KH, Kim HJ, Lee SU, Choi JY, Kim JS. Acute unilateral audiovestibulopathy due to embolic labyrinthine infarction. Front Neurol 2018;9:311. Creative Commons Attribution License; CC BY.) (Contributed by Dr. Douglas Lanska.)

Ocular vestibular-evoked myogenic potentials show no wave formation during right ear stimulation. (From: Liqun Z, Park KH, Kim HJ, Lee SU, Choi JY, Kim JS. Acute unilateral audiovestibulopathy due to embolic labyrinthine infarction. Front Neurol 2018;9:311. Creative Commons Attribution License; CC BY.) (Contributed by Dr. Douglas Lanska.)

Video-oculography shows spontaneous nystagmus beating leftward, upward, and counterclockwise without fixation. H = horizontal position of the left eye, V = vertical position of the left eye, T = torsional position of the left eye. In each recording, upward deflection indicates rightward, upward, and clockwise eye motion. (From: Liqun Z, Park KH, Kim HJ, Lee SU, Choi JY, Kim JS. Acute unilateral audiovestibulopathy due to embolic labyrinthine infarction. Front Neurol 2018;9:311. Creative Commons Attribution License; CC BY.) (Contributed by Dr. Douglas Lanska.)

Rightward ocular torsion is observed on fundus photos (normal range = 0–12.6°; positive values indicate an extorsion). (From: Liqun Z, Park KH, Kim HJ, Lee SU, Choi JY, Kim JS. Acute unilateral audiovestibulopathy due to embolic labyrinthine infarction. Front Neurol 2018;9:311. Creative Commons Attribution License; CC BY.) (Contributed by Dr. Douglas Lanska.)

MRI showing infarcts involving the left inferior frontal lobe (borderzone territory of the middle and anterior cerebral arteries) and the right occipital lobe (territory of the posterior inferior cerebellar artery). (From: Liqun Z, Park KH, Kim HJ, Lee SU, Choi JY, Kim JS. Acute unilateral audiovestibulopathy due to embolic labyrinthine infarction. Front Neurol 2018;9:311. Creative Commons Attribution License; CC BY.) (Contributed by Dr. Douglas Lanska.)

MRI with gadolinium showing contrast enhancement of the vestibule, cochlea, and semicircular canals. (From: Liqun Z, Park KH, Kim HJ, Lee SU, Choi JY, Kim JS. Acute unilateral audiovestibulopathy due to embolic labyrinthine infarction. Front Neurol 2018;9:311. Creative Commons Attribution License; CC BY.) (Contributed by Dr. Douglas Lanska.)

Bithermal caloric testing showed a right caloric paresis of 81%. SPV = slow phase velocity. (From: Liqun Z, Park KH, Kim HJ, Lee SU, Choi JY, Kim JS. Acute unilateral audiovestibulopathy due to embolic labyrinthine infarction. Front Neurol 2018;9:311. Creative Commons Attribution License; CC BY.) (Contributed by Dr. Douglas Lanska.)

Pure-tone audiometry showed moderate to profound hearing loss in the right ear. Lt = left; Rt = right; Δ = air conduction, masked, right ear; [ = bone conduction, masked, right ear; X = air conduction, unmasked, left ear; > = bone conduction, unmasked, left ear. Note: for the right ear above 1 kHz, there are tiny downward-pointing arrows attached to symbols on the left lower corner for bone- and air-conducted sound; these arrows indicate “no response.” (From: Liqun Z, Park KH, Kim HJ, Lee SU, Choi JY, Kim JS. Acute unilateral audiovestibulopathy due to embolic labyrinthine infarction. Front Neurol 2018;9:311. Creative Commons Attribution License; CC BY.) (Contributed by Dr. Douglas Lanska.)

Left-beating nystagmus after horizontal head-shaking. H = horizontal position of the left eye, V = vertical position of the left eye, T = torsional position of the left eye. In each recording, upward deflection indicates rightward, upward, and clockwise eye motion. (From: Liqun Z, Park KH, Kim HJ, Lee SU, Choi JY, Kim JS. Acute unilateral audiovestibulopathy due to embolic labyrinthine infarction. Front Neurol 2018;9:311. Creative Commons Attribution License; CC BY.) (Contributed by Dr. Douglas Lanska.)

Tender maculopapular rash on both feet consistent with Janeway lesions. (From: Liqun Z, Park KH, Kim HJ, Lee SU, Choi JY, Kim JS. Acute unilateral audiovestibulopathy due to embolic labyrinthine infarction. Front Neurol 2018;9:311. Creative Commons Attribution License; CC BY.) (Contributed by Dr. Douglas Lanska.)

Multiple scattered retinal hemorrhages with a white center consistent with Roth spots (arrow heads) in both eyes. (From: Liqun Z, Park KH, Kim HJ, Lee SU, Choi JY, Kim JS. Acute unilateral audiovestibulopathy due to embolic labyrinthine infarction. Front Neurol 2018;9:311. Creative Commons Attribution License; CC BY.) (Contributed by Dr. Douglas Lanska.)

(Courtesy of the U.S. Library of Congress.)

A large meningioma arising from the posterior falx cerebri in this patient caused severe bilateral visual loss. The post-contrast MRI demonstrates a homogenously enhancing lesion with a dural tail, characteristic of meningioma. (Contributed by Dr. Sashank Prasad.)

This MRI was obtained at the age of 14 months in a boy who had severe visual loss from birth. On the third day of life, he experienced profound hypoglycemia. The examination revealed no blink to threat but intact pupillary light reactions. (Contributed by Dr. Sashank Prasad.)