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  • Updated 05.10.2023
  • Released 02.14.1994
  • Expires For CME 05.10.2026

Startle epilepsy



Reflex seizures are epileptic events provoked by a specific afferent stimulus or by an activity of the patient. They include idiopathic photosensitive occipital lobe epilepsy, other visual sensitive epilepsies, primary reading epilepsy, and startle epilepsy (21).

Startle seizures are evoked by a sudden and unexpected sensory stimuli that is typically auditory, although somatosensory and visual stimuli may also be a trigger (40).

Most of patients with startle epilepsy present static neurologic and intellectual impairment due to pre- or perinatal insults, with infantile hemiplegia predominating (10). They also occur in the setting of metabolic diseases or genetic conditions such as trisomy 21. However, some neurologically normal individuals with startle epilepsy have also been reported (33).

Startle seizures are typically characterized by an initial startle response followed by axial unilateral or bilateral tonic posturing, frequently causing the patient to fall. Autonomic manifestations, automatisms, laughter, and jerks may occur. Less commonly, startle-induced seizures may be atonic or myoclonic, particularly in patients with cerebral anoxia (51).

Seizures are frequent and sometimes progress to status epilepticus.

Startle epilepsy should be distinguished from other nonepileptic disorders with abnormal responses to startling events, such as hyperekplexia (43).

Startle epilepsy is often resistant to the most common antiseizures medications (24). Epilepsy surgery may be beneficial to those with focal etiology of seizures (26).

Clinical manifestations, etiology (including inborn errors of metabolism), investigative procedures, pathophysiology, and management issues (including neurosurgery) of startle-induced epileptic seizures are included in this chapter.

Key points

• Startle epilepsy includes seizures evoked by sudden and unexpected stimuli, usually auditory.

• Typically, most patients have severe neurologic deficits.

• Typically, it affects children with severe neurologic deficits, brain anoxia, infantile hemiparesis, and Down syndrome.

• Startle-induced seizures mainly consist of axial tonic posturing, frequently causing falls.

• Startle epilepsy should be differentiated from nonepileptic startle-induced movement disorders (such as hyperekplexia).

• A total control of seizures is rarely achievable; neurosurgery in some patients with focal lesions may be therapeutic.

Historical note and terminology

The 1989 International Classification of Epilepsies and Epileptic Syndromes defines startle-induced epileptic seizures as follows: “Epileptic seizures may also be precipitated by sudden arousal (startle epilepsy); the stimulus is unexpected in nature. The seizures are usually generalized tonic but may be partial and are usually symptomatic” (08).

Startle-induced seizures are not considered in the position reports of the ILAE Commission for Classification and Terminology published in 2017 (16; 45). However, in the ILAE online diagnostic manual of the epilepsies, startle epilepsy is recognized and is detailed as shown below (07).

Clinical overview. Seizures are exclusively induced by startle with a sudden brief tonic seizure, typically affecting the trunk and causing a fall. Other seizure types may occur, including atonic and myoclonic seizures. Seizures are typically frequent.

Interictal EEG. Interictal EEG findings reflect the underlying etiology (eg, structural brain abnormality).

Interictal EEG. Interictal EEG findings reflect the underlying etiology (eg, structural brain abnormality).

Ictal EEG. Ictal EEG shows an initial midline vertex discharge followed by diffuse attenuation or low voltage fast activity (which may have onset or emphasis in areas of structural brain abnormality, and then spread). Ictal EEG may be obscured by myogenic artifact.

Neuroimaging. Neuroimaging is usually abnormal, with acquired or developmental structural brain abnormality, typically involving lateral sensorimotor cortex.

Genetics. Startle epilepsy is usually due to acquired structural brain abnormality and is not inherited; it may occur in children with Down syndrome.

Differential diagnosis.

• Hyperekplexia

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