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Part II : Clinical investigations in manB. Patients with brain lesionsThe structural analysis of the human EEG suffers from a major handicap: the impossibility of producing experimental lesions. However, in certain cases, diseases or trauma may bring about systematic nervous changes comparable to those of an experiment. For this reason, we have studied patients in a state of prolonged coma (from 6 months to 5 years). Polygraphic recordings (EEG, EMG, eye movements, EKG and respiration) were carried out both day and night in order to analyse the different patterns of sleep. The results of this study (Pellin 1960; Jouvet et al. 1960, 1961a), which are almost similar to the results of animal experiments, may be summarized as follows: (i) Syndrome of chronic decortication. Five adult patients had a prolonged altered state of consciousness due to white matter degeneration. After a severe head trauma, these patients were bed-ridden for several months to several years. They had no visual or auditory perception and could not obey simple commands. They opened their eyes and stared aimlessly for long periods during the day. Strong nociceptive stimuli would nevertheless induce a true painful countenance with midriasis and polypnea. All patients were very spastic and exhibited a characteristic rigidity. The findings at autopsy were remarkably similar in all cases and have been described elsewhere in detail (Pellin 1960; Trillet 1961). There were no focal lesions in the brain stem. Microscopically, there was a severe diffuse degeneration and often a necrosis of the cerebral white matter, associated with a degeneration of descending tracts ( Fig. 16). Such a traumatic encephalopathy is very similar to the cases reported by Strich (1957). Thus, in all these cases, the corticopetal and corticofugal fibers were almost all destroyed at the level of the cerebral white matter and the final physiological result may be considered as a decortication. In these patients, the polygraphic patterns of the sleep-wakefulness rhythm were similar ( Fig. 17 and 18). During wakefulness, with eyes open, there was a large amount of EMG activity at the level of the flexor muscles of the upper extremities (biceps) due to the hypertony of decortication. There were also many muscle artifacts in the EEG due to incessant chewing movements. The respiration had a periodic pattern. The EEG was characterized by a low voltage theta rhythm which was not altered by sensory stimuli. When the patients were left undisturbed in a silent and dark room, this pattern of wakefulness was periodically interrupted (2-3 times per h) by short periods of behavioral sleep whose polygraphic patterns were very similar to the RPS observed in decorticate cats. During this behavioral sleep, the EMG activity totally disappeared, while synchronous rapid bilateral eye movements occurred. Respiratory variations were quite clear cut. The periodic breathing observed during wakefulness gave way to deep and steady breathing. There were also cardiac rhythm alterations ( Fig. 18). During sleep, there were never slow waves or spindles in the EEG. The electrical activity remained with the same frequency as during wakefulness but with some decrease of amplitude. During these periods of sleep, which lasted for 7-10 min (their total duration was about 25 per cent of the recorded time), the thresholds of arousal were strongly enhanced. It was almost impossible to arouse the patients by auditory stimuli capable of inducing some primitive orientating reaction during wakefulness. Only nociceptive stimuli were effective. (ii) Syndrome of chronic decerebration. Two patients had a decerebrate state during 3 months after head trauma with decerebrate rigidity, "unconsciousness", and an almost permanent waking state. In such cases, there were short periods of behavioral sleep with slow waves. But an intense EMG activity ( Fig. 19) persisted through these periods in the extensor muscles of the upper and the lower extremities (triceps brachialis and quadriceps cruralis). Only extremely short periods (2 min) of disappearance of EMG activity associated with REM were observed. Their total duration did not exceed 2 per cent of the recording time. The autopsy showed localized infarction at the level of the reticular formation of the pons, the brachium conjunctivum and the inferior part of the mesencephalon. |
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