Physiologic events initiating REM sleep in patients with the postpolio syndrome

Background: We previously studied the occurrence of muscle tone reduction ( MTR), sawtooth waves (STW), and REM in sleep, and found a stereotypical seq uence of these events in normal subjects. Patients with the postpolio syndr ome may have involvement of the reticular formation in the brainstem, an ar ea known to mediate initiation of REM sleep. We hypothesized that such brai nstem pathology might affect the stereotyped sequence of events initiating REM sleep. Methods: We measured the latencies to the onsets of the first MT R, the first STW, and the first REM in 13 patients with postpolio syndrome, 7 of whom had bulbar involvement. All latencies were calculated from the l ast body movement before the onset of REM sleep. Results: Using analysis of variance, we found highly significant differences among the overall mean l atencies of the three types of onset (MTR, STW, REM) and also between the m ean latencies of the two subgroups of patients (bulbar, nonbulbar). Althoug h the latencies for the entire group were longer than those of the normal v olunteers, the differences were not significant. However, when the bulbar a nd nonbulbar groups were compared, analysis of variance showed significantl y longer latencies for the bulbar group than for the nonbulbar group (p < 0 .0001). The values for the nonbulbar patients closely resembled those for t he normal controls. Although the latencies differed, the slopes of the regr essions of REM on STW, STW on MTR, and REM on MTR resembled each other clos ely (p = 0.924). Conclusion: Prolongation of these latencies may be due to prolonged recruitment time for neurons in the pontine tegmentum, following damage from polio. This may be a sensitive marker of a brainstem lesion, an d may also represent a type of sleep pathology not previously explored.