Peripheral nerve function in patients with excessive fragmentary myoclonus during sleep

Objectives: Excessive fragmentary myoclonus is a frequent incidental finding in patients undergoing polysomnography for other reasons. The aim of this study was to evaluate whether electrophysiological examination in patients with excessive fragmentary myoclonus during sleep according to American Academy of Sleep Medicine (AASM) criteria shows findings of peripheral nerve dysfunction.

Methods: Ninety-eight of 100 patients with excessive fragmentary myoclonus detected as an incidental finding during routine polysomnography underwent electrophysiological workup. Motor nerve conduction studies of the right peroneal and tibial nerves, F-wave recordings of the tibial nerve, antidromic sensory nerve conduction studies of the left sural nerve and needle electromyography of the right tibialis anterior muscle were performed and classified as normal, peripheral neuropathy, lumbar 5 (L5) nerve root lesion, or benign fasciculations.

Results: Fifty percent (49 out of 98) presented with electrophysiological abnormalities, most frequently polyneuropathy (32 out of 49, 65.3%), followed by L5 nerve root lesions (13 out of 49, 26.5%) and benign fasciculations (4 out of 49, 8.2%). Patients with electrophysiological abnormalities were older than those without.

Conclusions: The high prevalence of abnormal neurophysiological findings in patients with excessive fragmentary myoclonus during polysomnography suggests that excessive fragmentary myoclonus during sleep according to AASM criteria is not primarily a sleep-related phenomenon, but only persists during sleep and points to peripheral nerve pathology at least in part of the cases. Patients with incidental EFM during polysomnography should undergo electrophysiological workup for peripheral nerve pathology.