[Central sleep apnea syndrome as a cause of impaired wakefulness in multiple myeloma].

Progressive day-time sleepiness developed in a 73-year-old man for 3 years known to have kappa-light-chain myeloma, treated with radio- and chemotherapy. His powers of concentration and intellectual performance were diminished. Neither clinical nor biochemically was there any indication of abnormal water and electrolyte metabolism or hyperviscosity syndrome. The neurological examination was unremarkable. His wife's observation of nocturnal breathing pauses suggested sleep-related abnormal breathing. Polysomnography showed severe central sleep apnoea: an apnoea index of 60/h and blood oxygen saturations as low as 78%. On biphasic positive airway pressure (BIPAP) ventilation by nasal mask at night the apnoea index fell to 6/h and the symptoms improved. During a break in treatment the day-time sleepiness again increased and regressed once again with BIPAP ventilation. There is a 1-5% prevalence of sleep-related impaired breathing among adults. This condition should thus be considered in the differential diagnosis of characteristic day-time sleepiness.