Phasic activities of rapid eye movement sleep in Vegetative State patients

Study objectives: To assess the phasic components of rapid eye movement (RE M) sleep in patients in vegetative state and to evaluate the possible relat ionship of these activities to patient outcome. Setting: Sleep disorders unit at a major rehabilitation hospital. Design: Comparative control study. Patients: Eleven patients in vegetative state (10 males and 1 female) aged 17-53 years. Interventions: Continuous 24-hour polysomnographic recording. Measurements and Results: All the patients had REM sleep periods during the 24-hr recording session. Mean total REM sleep time for the whole session w as 66.5+/-34.9 min, and for the nocturnal hours only, 37.3+/-19.7 min. Comp arison with the control group (792.+/-11.5 min) yielded a significant diffe rence only for nocturnal REM sleep time (p<0.0003). The duration of the REM sleep periods was significantly shorter in the patients than the controls for the whole 24-hr session (10.9+/-6.0 vs. 19.6+/-4.9 min, p<0.008), but n ot for the nocturnal period alone. Compared to controls, the density of rap id eye movements (REMs) (p=0.001), chin twitches (p=0.002), and leg muscle twitches (p=0.023) was significantly lower in the patient group. The densit y of the sawtooth waves was also lower in the patients, but the difference did not reach significance (p=0.069). Similar results were obtained when th e comparison was done only for the nocturnal period. There was no significa nt difference for any of the REM sleep characteristics or REM sleep phasic activities (24-hr, nocturnal and diurnal periods) between the patients who recovered consciousness and those who did not. Conclusions: The present study shows that patients in vegetative state have a significant reduction in the phasic activities of REM sleep. However, th e amount of these activities is unrelated to recovery from the clinical con dition. These findings may reflect possible damage to the pedunculopontine tegmentum cholinergic mechanisms in vegetative state.