Electroencephalography and clinical neurophysiology
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Electroencephalogr Clin Neurophysiol · Jan 1987
Prognostic value of early cortical somatosensory evoked potentials after resuscitation from cardiac arrest.
Short-latency somatosensory evoked potentials (SEPs) were evaluated in patients after cardiorespiratory arrest to study their pattern of recovery in the acute stage of anoxic-ischaemic coma. Fifty consecutive comatose patients were investigated within 8 h after cardiorespiratory resuscitation. In 30 patients no cortical SEPs were recorded and none of the patients recovered cognition. ⋯ The different susceptibility of frontal and parietal cortical structures to anoxia was reflected by the dissociated loss of parietal or frontal potentials in 6 patients. Post-mortem pathology in 15 patients confirmed extensive anoxic-ischaemic damage of cerebral and cerebellar cortex and thalamus in patients without cortical SEPs whereas the histological lesions were restricted to Sommer's sector and Purkinje cells in those with preserved SEPs. SEPs thus reflect the extent of brain damage after cardiorespiratory resuscitation.
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Electroencephalogr Clin Neurophysiol · Sep 1986
Neural generators of the brain-stem auditory evoked potentials (BAEPs) in the rhesus monkey.
Brain-stem auditory evoked potentials (BAEPs) were recorded from rhesus monkeys in response to click stimuli. The BAEPs in the monkey have only 4 major peaks, while 5 major peaks can be identified in the human BAEP. The responses from electrodes placed at the vertex and the mastoid recorded either differentially or separately using non-cephalic references were compared to concomitant recordings from the auditory nerve, the cochlear nucleus, and the inferior colliculus, including the lateral lemniscus and the brachium of the inferior colliculus. ⋯ Deafferentation of the inferior colliculus resulted in only small changes in the BAEP, indicating that the contributions to the BAEP from the inferior colliculus and more central structures of the ascending auditory pathway are insignificant. It is concluded that the main reason for the difference between the human BAEP and the BAEP in the rhesus monkey is the smaller size of the monkey's head and the resulting shorter auditory nerve. The result is that the auditory nerve in the monkey only generates one peak in the far-field response, while in man the auditory nerve gives rise to both of the two earliest peaks in the BAEP; thus, the BAEP in man has 5 peaks while that in the monkey has only 4 peaks.
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Electroencephalogr Clin Neurophysiol · Mar 1986
Cortical potentials evoked by epidural stimulation of the cervical and thoracic spinal cord in man.
Scalp somatosensory evoked potentials (SEPs) were recorded after electrical stimulation of the spinal cord in humans. Stimulating electrodes were placed at different vertebral levels of the epidural space over the midline of the posterior aspect of the spinal cord. The wave form of the response differed according to the level of the stimulating epidural electrodes. ⋯ In 4 patients the CV along the spinal cord was calculated from the difference in latencies of the cortical responses to stimulation at two different vertebral levels. The CVs were in the range of 45-65 m/sec. The method was shown to be promising for future study of spinal cord dysfunctions.
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Electroencephalogr Clin Neurophysiol · Sep 1985
Case ReportsUnusual pattern of somatosensory and brain-stem auditory evoked potentials after cardio-respiratory arrest.
Two patients in coma after cardio-pulmonary arrest showed bilateral absence of all brain-stem auditory evoked potentials contrasting with normal brain-stem reflexes and normal somatosensory cortical evoked potentials. In both patients pre-existing dysfunction of peripheral auditory structures could be ruled out. Subsequent neuropathological analysis showed that the anoxic-ischaemic lesions were restricted to Sommer's sector and the Purkinje cells. These unusual data suggest the hypothesis that a severe hypoxic-ischaemic insult may impair cochlear function and interfere with the activation of the intact auditory pathways.
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Electroencephalogr Clin Neurophysiol · Mar 1985
Ambulatory monitoring of the electroencephalogram in high altitude mountaineers.
Twenty-nine 24 h ambulatory EEG recordings were obtained from 9 British Army mountaineers at heights ranging from 4115 to 6220 m during the period of acclimatization. Three individuals also had ambulatory sea-level EEGs. Sea-level clinical recordings were made on all the mountaineers. ⋯ There was a lesser reduction of REM sleep. These findings are consistent with complaints of poor quality sleep at high altitude, despite ample opportunity for sleep and the maintenance of health. The latter was attributed to careful acclimatization.