Startle response: epileptic or non-epileptic? The case for "flash" SMA reflex seizures

A 19-year-old woman complained of long-standing, frequent, debilatating bru sque movements triggered by unexpected stimuli. She was neurologically norm al and neuroimaging was also normal. Conspicuous startle reactions were eas ily reproduced under EEG and video monitoring: the interictal EEG was norma l, the ictal recordings doubtful; clinically, the startle reaction was asym metric, with elevation of the left limbs. The diagnosis of hyperekplexia an d startle epilepsy were discussed. We learned that she had been evaluated a t age 3-4 months for spontaneous, generalised tonic-clonic seizures and "in fantile spasms", in fact for early-onset startle reactions triggered by noi se or contact, in association with prominent EEG changes. A full remission had been achieved under ACTH therapy, but the startle reactions had reappea red at around age six. The patient was successfully treated with carbamazep ine. The history, clinical and neurophysiological data led us to discuss th e diagnosis of hyperekplexia and startle epilepsy. We concluded that the pa tient had an unusual form of cryptogenic focal epilepsy originating from th e supplementary motor area, presenting as strictly stimulus-triggered "flas h" seizures.