Intensified Hypnic Jerks

Abstract

To analyze the nature and propagation of muscle bursts in patients presenting with intensified hypnic jerks and sleep onset insomnia. We obtained polymyographic recordings from cranially and spinally innervated muscles during polysomnographic study in 10 subjects presenting with repeated jerking movements at sleep onset, anxiety and sleep onset insomnia. One subject also had daytime polymyography during relaxed wakefulness and drowsiness as well as back-averaging of the EEG preceding the muscle bursts. We observed 4 patterns of muscle propagation: synchronous and symmetrical patterned muscle bursts between the two sides and agonist-antagonist muscles similar to those noted in audiogenic startle reflex, reticular reflex myoclonus, dystonic myoclonus, and pyramidal myoclonus with rostrocaudal propagation of muscle bursts. Hypnic jerks are physiological phenomena which may be accentuated and repeated and may be of several physiological subtypes.