Excessive fragmentary hypnic myoclonus: clinical and neurophysiological findings.
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.
Institute of Clinical Neurology, University of Bologna, Via Ugo Foscolo 7, 40123 Bologna, Italy. pmontagn@neuro.unibo.it
Roberto
R
Vetrugno
Giuseppe
G
Plazzi
Federica
F
Provini
Rocco
R
Liguori
Elio
E
Lugaresi
Pasquale
P
Montagna