Autonomic disturbances in narcolepsy

Narcolepsy is a clinical condition characterized mainly by excessive sleepiness and cataplexy. Hypnagogic hallucinations and sleep paralysis complete the narcoleptic tetrad; disrupted night sleep, automatic behaviors and weight gain are also usual complaints. Different studies focus on autonomic changes or dysfunctions among narcoleptic patients, such as pupillary abnormalities, fainting spells, erectile dysfunction, night sweats, gastric problems, low body temperature, systemic hypotension, dry mouth, heart palpitations, headache and extremities dysthermia. Even if many studies lack sufficient standardization or their results have not been replicated, a non-secondary involvement of the autonomic nervous system in narcolepsy is strongly suggested, mainly by metabolic and cardiovascular findings. Furthermore, the recent discovery of a high risk for overweight and for metabolic syndrome in narcoleptic patients represents an important warning for clinicians in order to monitor and follow them up for their autonomic functions. We review here studies on autonomic functions and clinical disturbances in narcoleptic patients, trying to shed light on the possible contribute of alterations of the hypocretin system in autonomic pathophysiology.