Electrophysiological brain stem investigations in idiopathic narcolepsy

Narcolepsy is associated with various rapid eye movement (REM) sleep abnormalities. Distinct brain stem areas seem to play a prominent role in REM sleep regulation. Recent magnetic resonance imaging (MRI) studies have led to conflicting findings concerning the presence of structural brain stem lesions in patients with idiopathic narcoleptic syndrome. However, multimodal electrophysiological brain stem investigations may reveal functional brain stem abnormalities even in the absence of MRI abnormality. Therefore we investigated brain stem function in 12 idiopathic narcoleptic patients by systematically studying tegmental brain stem pathways. All of the patients met the diagnostic criteria of the International Classification of Sleep Disorders, with typical changes in polysomnography and the multiple sleep latency test. Electrophysiological investigations comprised masseter reflex, blink reflex, masseter inhibitory reflex, early auditory evoked potentials and electrooculography with vestibular testing. In no patient were electrophysiological brain stem abnormalities observed. Our findings do not support the existence of a relevant brain stem lesion in narcoleptic patients with normal neurological status.