Extremely sustained startle-induced clonus: Non epileptic motor attacks mimicking clonic seizures in children with encephalopathy

Clonus is a pathological motor pattern characterised by involuntary, rhythmic and brisk muscular contractions in response to peripheral stimuli producing muscle stretching. It indicates pathological involvement of the corticospinal tract and can be considered as a functional spastic movement disorder of variable clinical presentation and duration. We documented severe and prolonged episodes of startle-induced clonic attacks associated with severe apnoea, occurring in three infants with severe encephalopathy. The clinical characteristics of such episodes are very similar to those of clonic epileptic seizures. Video-EEG recordings confirmed the non epileptic origin of the episodes. Previous anti-epileptic drug treatment was unsuccessful but myorelaxing drugs produced a dramatic improvement.