CARDIAC AUTONOMIC FUNCTION DURING SLEEP AND WAKEFULNESS IN MULTIPLE-SCLEROSIS

Some studies in multiple sclerosis (MS) patients have shown evidence o f autonomic dysfunction involving the cardiovascular system. However, the findings in these studies have not been completely consistent. The discrepancy may be related to the limits of the traditional autonomic tests during wakefulness. In our study, after the investigation of th e cardiovascular reflexes during wakefulness, heart rate (HR) variatio ns were considered during sleep in order to avoid the limits of cooper ation and the emotional state of the patient. We evaluated tonic (vaga l activity) HR modifications in relation to the deepening of sleep, as well as phasic (sympathetic activity) HR modifications in relation to spontaneous body movements during sleep, in 25 MS patients and 25 age -matched controls. No difference was found between the two groups in a utonomic function during wakefulness. A reduced parasympathetic activi ty was observed in MS subjects during both rapid eye movement (REM) an d non-REM sleep, while no difference was found in sympathetic function between patients and controls. No significant correlation was found b etween cardiac autonomic data during sleep and MRI lesion load in the infratentorial areas and, in particular, of the brain stem. The findin gs of our study suggest that autonomic nervous system evaluation durin g sleep could show impairment earlier than the traditional autonomic t ests during wakefulness.