Paroxysmal non-epileptic motor events in childhood: a clinical and video-EEG-polymyographic study.

The aim of this article was to describe the phenomenology and polymyographic features of paroxysmal non-epileptic motor events (PNMEs) observed in a series of typically developing and children with neurological impairment. We conducted a retrospective evaluation of 63 individuals (29 females; 34 males) affected by PNMEs at the National Neurological Institute 'C. Besta' between 2006 and 2008. Individuals were included in the study if they had PNMEs documented by a video-electroencephalography-polymyographic study and were aged between 1 month and 18 years (mean age at the time of video-electroencephalography-polymyography: 5y 10mo). In 45 of the 63 participants (71%), PNMEs were associated with other neurological conditions (secondary) including epilepsy, whereas in 18 participants PNME was the only neurological symptom (primary). Clinical features allowed classification of the motor disturbance into usual movement disorder categories in 31 individuals (49%); in the remaining 32 (51%), the movement disorder was characterized on the basis of polymyographic pattern of 'jerks' or 'sustained contraction'. The most frequent PNMEs were paroxysmal dyskinesias, followed by startle, stereotypies, shuddering, sleep myoclonus, psychogenic movement disorders, and benign myoclonus of early infancy; the last syndrome was also observed in children with neurological impairment. In eight participants, PNMEs remained unclassified. PNMEs may occur in both healthy and children with neurological impairment and are caused by a wide range of static and progressive conditions. In the majority of children with neurological impairment with associated epilepsy, the PNMEs do not fit into the usual movement disorders categories. A video-electroencephalography-polymyography is therefore useful for characterizing them.