Central deafness

Douglas J Lanska MD FAAN MS MSPH (Dr. Lanska of the Great Lakes VA Healthcare System and the University of Wisconsin School of Medicine and Public Health has no relevant financial relationships to disclose.)
Originally released January 12, 2015; last updated July 14, 2017; expires July 14, 2020

Overview

Central auditory disorders involve dysfunctional processing of auditory sensory information within the central nervous system, particularly within the brainstem and cerebrum. Central hearing loss may occur with lesions of the ascending auditory pathways from the cochlear nuclei (on the dorsolateral surface of the brainstem at the junction of the medulla with the pons) to the auditory cortex in the temporal lobe. Of the central disorders of hearing, unilateral hearing impairment can occur with focal lesions of the brainstem that involve the cochlear nucleus and its connections, whereas lesions at higher levels generally produce bilateral central hearing impairment. Cortical auditory disorders form a continuum that includes cortical deafness, word deafness, and auditory agnosia.

Key points

 

• Disorders of the special senses, and particularly for the sense of hearing, can be conveniently divided into conductive, sensorineural, and central disorders, where (1) conductive disorders involve transmission of the sensory stimuli to the sensory receptors (usually but not always by impeding transmission); (2) sensorineural disorders involve dysfunction of the sensory receptors (ie, sensory) or the transmission of signals from the sensory receptors to the brain (ie, neural); and (3) central disorders involve dysfunction of the processing of sensory information within the central nervous system, particularly within the brainstem and cerebrum.

 

• Central hearing loss may occur with lesions of the ascending auditory pathways from the cochlear nuclei (on the dorsolateral surface of the brainstem at the junction of the medulla with the pons) to the auditory cortex in the temporal lobe.

 

• Of the central disorders of hearing, unilateral hearing impairment can occur with focal lesions of the brainstem that involve the cochlear nucleus and its connections whereas lesions at higher levels general produce bilateral central hearing impairment.

 

• Central hearing loss may be associated with other central auditory disorders, including dysacusis (ie, the experience of sound as distorted or disagreeable), impaired sound localization, and auditory hallucinations.

 

• Because common features can be delineated in reported cases of pure word deafness, auditory agnosia, and cortical deafness, these disorders form a continuum rather than being 3 distinct syndromes.

Historical note and terminology

Austrian anatomist Richard Ladislaus Heschl (1824-1881) described the transverse temporal gyrus or "Heschl's gyrus" in 1855.

Image: Richard Ladislaus Heschl (1824-1881)
Cortical deafness in a woman with bitemporal infarctions was described by German neuropsychiatrist Carl Wernicke (1848-1905) and Carl Friedlander (1847-1887) (Wernicke and Friedlander 1883).
Image: Carl Wernicke (1848-1905)
German physician Adolph Kussmaul (1822-1902) described a patient with pure word deafness in 1877, and Austrian neurologist and psychiatrist Sigmund Freud (1856-1939) first used the term auditory agnosia in 1891 (Kussmaul 1877; Freud 1891).
Image: Adolph Kussmal (1822-1902)
Image: Sigmund Freud (1856-1939)
German neurologist and anatomist August Knoblauch (1863-1919) described a detailed cognitive model of music processing, classified disorders of music production and perception, and coined the term "amusia" (Johnson and Graziano 2003).
Image: August Knoblauch (1863-1919)

Disorders of the special senses, and particularly for the sense of hearing, can be conveniently divided into conductive, sensorineural, and central disorders, where (1) conductive disorders involve transmission of the sensory stimuli to the sensory receptors (usually but not always by impeding transmission); (2) sensorineural disorders involve dysfunction of the sensory receptors (ie, sensory) or the transmission of signals from the sensory receptors to the brain (ie, neural); and (3) central disorders involve dysfunction of the processing of sensory information within the central nervous system, particularly within the brainstem and cerebrum (Lanska 2014). Thus, for the auditory system, conductive disorders typically involve the obstruction of sound conduction within the external and middle ear, sensorineural disorders involve dysfunction of the cochlea and eighth cranial nerve, and central disorders involve dysfunction of the auditory pathways in the brainstem and cerebrum. In some cases, mixed auditory dysfunction may have synergistic adverse effects on hearing; in particular, adults with conductive hearing loss may have reduced auditory temporal processing ability compared to normal hearing subjects (Bayat et al 2017).

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