On our clinical service, we recently encountered an infant with generalized stiffness and considered the diagnosis of hyperekplexia. Hyperekplexia is a disorder characerized by generalized stiffness in the neonatal period which improves over time, an overactive startle reflex, and a period of generalized stiffness following the startle response. We found that this diagnosis can be difficult to make, and in particular can be mistaken for seizures. Some diagnostic clues that were useful to usÂ included an exaggerated head-retraction reflex,Â and a clinical response to clonazepam. 5 genes are known to be associated with hyperekplexia, the most common being GLRA1. A good literature review of this rare disorder was recently published by Mineyko, Can J Neurol Sci. 2011 May;38(3):411-6.
Hilary Vernon, MD PhD