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.