John Libbey Eurotext

Startle response: epileptic or non-epileptic? The case for "flash" SMA reflex seizures Volume 3, issue 1, Mars 2001


  • Startle response: epileptic or non-epileptic? the case for « lfash » SMA reflex seizures


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Centre Saint-Paul, 13258 Marseille 09, France.

A 19-year-old woman complained of long-standing, frequent, debilatating brusque movements triggered by unexpected stimuli. She was neurologically normal and neuroimaging was also normal. Conspicuous startle reactions were easily reproduced under EEG and video monitoring: the interictal EEG was normal, the ictal recordings doubtful; clinically, the startle reaction was asymmetric, with elevation of the left limbs. The diagnosis of hyperekplexia and startle epilepsy were discussed. We learned that she had been evaluated at age 3-4 months for spontaneous, generalised tonic-clonic seizures and "infantile spasms", in fact for early-onset startle reactions triggered by noise or contact, in association with prominent EEG changes. A full remission had been achieved under ACTH therapy, but the startle reactions had reappeared at around age six. The patient was successfully treated with carbamazepine. The history, clinical and neurophysiological data led us to discuss the diagnosis of hyperekplexia and startle epilepsy. We concluded that the patient had an unusual form of cryptogenic focal epilepsy originating from the supplementary motor area, presenting as strictly stimulus-triggered "flash" seizures.The startle reaction following an unexpected stimulus is a physiological response. A stereotyped motor pattern consists of a brief flexion response, most marked in the upper half of the body with facial grimacing, head movement, elevation of the shoulders, abduction of the upper arms and flexion of the elbows, trunk and knees. This response is heightened by anxiety, fatigue or following sleep deprivation and can reach such a degree in frequency and intensity or become so extensive in distribution that it can become pathological [1-3]. Excessive startle responses are described as epileptic and non-epileptic attacks. When faced with a striking startle reaction, the clinician may wonder whether its nature is epileptic or not: a precise diagnosis may have therapeutic consequences, and is not always easy. The purpose of this paper is to report a young woman who presented with an excessive startle response, in order to discuss the elements of diagnosis.