Hyperekplexia, an underdiagnosed motor paroxysm of infancy, mimics epilepsy closely. It is hallmarked by episodic and excessive startle response, brief episodes of intense, generalized hypertonia, or stiffness in response to unexpected auditory and/or tactile stimuli right from birth. Though a seemingly benign entity with an excellent prognosis, hyperekplexia has been occasionally associated with recurrent apneas, feeding difficulties, and sudden infant death syndrome (SIDS). We describe three unrelated children with hyperekplexia (two SLC6A5; one GLRA1). All three children had the onset of motor paroxysms from the neonatal period and were initially labeled as drug-resistant epilepsy leading to a variable diagnostic delay, the longest being 2.5 years. An excellent response to oral clonazepam with a good neurodevelopmental outcome was observed. The lack of habituation on the nose-tapping test is a simple clinical clue to the diagnosis. Early differentiation from epilepsy minimizes treatment cost, allays caregiver anxiety, and empowers them with abortive measures.
Keywords: Exaggerated startle reflex; Vigevano maneuver; glycine receptor encephalopathy; hyperekplexia; nose-tapping test.