ZCYA.htm

NR ZCYA

AU Gibbs,F.A.; Davis,H.; Lennox,W.G.

TI The electro-encephalogram in epilepsy and in conditons of impaired consciousness

QU Archives of Neurology and Psychiatry 1935; 34: 1134-1148

PT journal article

AB The fluctuations in electric potential that originate in the brains of human subjects have been studied with special reference to the manner in which they are altered in epileptic seizures and other conditions characterized by disturbances of consciousness, notably sleep, unconsciousness from breathing nitrogen, unconsciousness from failure of the cerebral blood supply and clouding of consciousness from overventilation. Standard leads were: a needle thrust into the scalp at the vertex of the head as a grid lead and, except in studies on grand mal seizures, a similar needle in the lobe of the ear as a ground. for studies on grand mal epilepsy, a diffuse electrode in the form of a crown was used. The most constant and pronounced fluctuations observable in the resting subject with these leads have frequencies of from 10 to 20 per second and attain a maximum of 60 microvolts. In sleep the frequency of these predominant waves decreases to between 1 and 5 per second. Their amplitude also may decrease as the subject falls asleep, if the subject is one who when awake shows waves of large amplitude; but this change is only temporary, for during deep sleep waves of large amplitude and slow frequency appear,often in rhythmic bursts. These may have a voltage of 200 microvolts (chart 2). In patients suffering from frequent attacks of petit mal epilepsy, groups of large, slow waves appear associated with the seizures. They attain a voltage of from 100 to 300 microvolts at a frequency of 3 per second, showing in all cases a characteristic form (chart 3). They are approximately sinusiodal but usually include a sharp negative spike near the positive crest so that the record at times forms a perfect 'egg and dart' design. The spike often appears late in the seizure and tends to disappear before the seizure is over. Grand mal epileptic seizures are preceded by the gradual appearance of waves having a somewhat higher frequency than those which have been previously dominant. These waves increase in amplitude, and the convulsion begins. The waves continue to increase in amplitude, the frequency remaining about the same. As the clonic phase sets in the fast waves tend to clump together into slower waves at about 5 per second. As the convulsive movements die down, the amplitude and also the frequency of the waves decrease, so that during the postconvulsive stupor the record is nearly flat (chart 4). If a subject becomes unconscious from breathing nitrogen, the frequency of his predominant waves decreases to between 1 and 5 per second, and the amplitude increases to about 200 microvolts (chart 5). This change occurs rather gradually, beginning definitely before the subject loses consciousness. The same change occurs if a subject becomes unconscious from failure of the cerebral blood supply (chart 6). A similar, but less marked, change occurs if a subject overventilates his lungs in room air (chart 7). The frequency drops to about 5 per second, and the amplitude increases to about 100m microvolts. Those procedures which tend to produce large, slow waves in the normal subject also tend to produce seizures in patients with epilepsy.

SP englisch

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