Neurological and EEG findings in the monkey after total body x-irradiation

Abstract

Serial neurological and EEG examinations have been made in monkeys subjected to lethal and near-lethal doses of total body X-irradiation. With the onset of symptoms of radiation sickness, behavioral alterations consisting of anorexia, listlessness and hypokinesia appeared and, in severely ill animals, progressed to prostration and coma before death. Depression of iridal and tendon reflexes was encountered in such severely ill monkeys and, in one case, tic-like jerks of the neck and upper extremities were displayed terminally. In convalescent and surviving cases, no behavioral or neurological abnormalities were exhibited. Preliminary study of the normal monkey's EEG revealed low voltage fast discharge associated with alertness or excitement, an alpha rhythm of 7–9.5/sec. in relaxed wakefulness and large 1–2/sec. humps or waves with drowsiness or sleep. The induction of Nembutal anesthesia in the normal animal was associated with a period of low fast discharge before regular, high amplitude 1/sec. waves appeared. The overall EEG picture after irradiation was that of no significant change from normal. However, a slight slowing and greater irregularity of the alpha rhythm was present in several animals from the day of radiation. In pre-terminal stages, when the animal was severely ill, the EEG was greatly altered and consisted of high voltage, slow waves which gave way to an almost iso-electric tracing before death. These terminal alterations appeared secondary to general breakdown of the body's homeostasis, and the present findings are considered to be in accord with those of others which point to a high degree of resistance or protection of the nervous system to irradiation.