Startle epilepsy

Startle epilepsy is a rare form of reflex epilepsy in which seizures are consistently triggered by sudden, unexpected stimuli — most commonly loud sounds, but also unexpected touch or visual stimuli. The condition is classified under ICD-10 code G40.5 (special epileptic syndromes). Startle epilepsy predominantly affects the central nervous system and is characterized by brief tonic seizures that occur in response to startle-provoking stimuli. These seizures typically involve a sudden tonic contraction, often asymmetric, that may lead to falls. The episodes are usually brief, lasting seconds, but can sometimes evolve into more prolonged tonic or tonic-clonic seizures. Startle epilepsy most commonly occurs in individuals who have pre-existing brain damage or structural brain abnormalities, particularly those with infantile hemiplegia, periventricular leukomalacia, or cortical dysplasia. It is frequently seen in patients who also have other seizure types and neurological deficits, including intellectual disability and motor impairments such as spastic hemiparesis or tetraparesis. The seizures are thought to originate from or near the supplementary motor area of the frontal lobe, which plays a role in motor planning and startle responses. Treatment of startle epilepsy can be challenging, as seizures are often resistant to conventional antiepileptic medications. However, some patients may respond to drugs such as clobazam, clonazepam, or other benzodiazepines, as well as broader-spectrum antiepileptic drugs like valproate or levetiracetam. In medically refractory cases, surgical evaluation may be considered, particularly if a focal structural lesion is identified. Avoidance of known startle triggers, when possible, is also an important component of management. Callosotomy has been reported to reduce seizure frequency in some refractory cases.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

Common questions about Startle epilepsy