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Physiologic studies suggest that the startle response originates in the brain stem, but its exact location in the reticular formation is unclear. Startle syndromes are a heterogenous group of disorders involving abnormal responses to startling events. In this review, the authors consider the clinical features, electrophysiology, genetics, and treatment of these uncommon disorders. They are divided into three groups: hyperekplexia, neuropsychiatric startle syndromes, and stimulus-induced disorders.
Hyperekplexia means “exaggerated startle.” The major form is inherited as an autosomal dominant entity and is due to various mutations in the glycine receptor gene (GLRA1) on chromosome 5q33-35. (Glycine receptors in the brain stem and spinal cord …