Hyperekplexia in a patient with a brainstem vascular anomaly

Objectives - To describe a patient with a clinical picture suggestive of idiopathic hyperekplexia (IH), who was later found to harbour a subtle brainstem vascular anomaly. Patient - A 35-year-old man, 4 years earlier, developed sudden jumping and falling in response to unexpected sensory stimuli. Results - Neurological examination was normal. Electromyography showed an excessively large and non-habituating motor startle response. There were no mutations of the a, subunit of the inhibitory glycine receptor which cause hereditary hyperekplexia. Although all these findings were consistent with a diagnosis of IH, a blink reflex study showed an enhanced recovery curve suggestive of a brainstem lesion. A detailed MRI study revealed a subtle vascular anomaly involving the lower brainstem. Conclusion - This is the first report of sporadic hyperekplexia related to a brainstem vascular anomaly. Subtle damage to the brainstem should always be excluded in patients with sporadic hyperekplexia, regardless of the coexistence of additional clear-cut neurological symptoms.