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Published on: June 11, 2020
Excessive fragmentary hypnic myoclonus: clinical and neurophysiological findings
Roberto Vetrugno1, Giuseppe Plazzi, Federica Provini
1Institute of Clinical Neurology, University of Bologna, Via Ugo Foscolo 7, 40123 Bologna, Italy. pmontagn@neuro.unibo.it
Background:
Brief involuntary sleep-related twitches occurring asymmetrically throughout the body define physiologic hypnic fragmentary myoclonus. An abnormal intensification of this entity identifies excessive fragmentary hypnic myoclonus (EFHM), a 'proposed sleep disorder' in the International Sleep Disorders Classification.
Methods:
We describe two patients with EFHM, one associated with a REM behaviour disorder.
Results:
EFHM activity was restricted to sleep prevailing during NREM sleep stages and the second part of the night. EMG was normal and EEG-EMG back-averaging did not show any cortical potentials related to the twitches.
Conclusions:
EFHM represents a pathological phenomenon which may or may not be associated with other sleep disorders. A brainstem generator explains its distribution throughout the body and the sleep stages.
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