Mu rhythm status and clinical correlates

Rolandic mu rhythm is usually limited to brief stretches of 0.5 to 2 sec duration. Two observations of status-like enhancement of mu rhythm have prompted this report. In both cases, 4-hour EEG-Video-Monitoring was used. Clinically, the reported cases differed considerably. Case 1 showed nearly continuous mu activity associated with general motionlessness: akinesia/amimia but without rigidity, caused by frontal lobe impairment due to multiple sclerosis. In Case 2, an impressive mu-status started in drowsiness and was presumably attributable to levitiracetam (which had rendered seizure-free the patient's formerly severe case of temporal lobe epilepsy). Mu rhythm status, thus far, is an unknown EEG entity. It can be caused by impaired fronto-motor input and may also constitute a medication-effect (levitiracetam). INTRODUCTION The term "mu status" denotes a Rolandic mu rhythm of highly unusual persistence and continuous character for long periods. Usually, mu rhythm tends to occur in short runs of 0.5 to 2 sec duration, longer stretches being exceptional. For this reason, the observation of two patients with very prolonged and nearly continuous Rolandic mu activity is quite unique. Such a status-like mu rhythm raises the question of associated clinical findings and possibly existing meaningful clinical-electrophysiological correlations.