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Electroencephalogram in Hydrocephalus

Previous reports regarding electroencephalograms in hydrocephalus have been based almost exclusively on awake recordings. The chief exception is an article published by Fois, Gibbs and Gibbs’, in which they reported that a high percentage (66%) of these patients showed bilaterally independent or asynchronous sleep patterns. In previous reports of the waking activity Kreezer2 reported high voltage alpha waves and the Gibbs3 mixed fast and slow activity. Pampiglione and Laurence4 found no correlation between the size of the head, thinness of the pallium and any particular electroencephalographic pattern. In two patients they found no marked changes in the electroencephalogram when the intraventricular pressure had been lowered to one-half of its original value by ventricular drainage. They noted marked asymmetry in the activity of the two cerebral hemispheres, especially in cases of cisternal block. Other references to the literature prior to 1964 are cited in Vol. 3 of the Gibbs‘ Atlas5. Three recent studies were not published in full but only as abstracts. Sternberg et a1.6 studied 50 cases of hydrocephalus and reported four different types of abnormality: (1) increased voltage production, (2) slow waves or spike and wave discharges, either asymmetrical or focal, (3) diffuse abnormality, (4) unilateral depression of amplitude. Only the last mentioned correlated with particular clinical features of the case. Of eighteen patients with shunts, Law and Niedermeyer’ found only one who had a normal EEG. Seizure discharges were present in twenty-five patients without shunts; three were normal. Forster and Pornpino8 studied thirty-one hydrocephalics; eighteen were normal and thirteen were abnormal. In several cases after shunting the EEG showed changes whichwere of some prognostic value. Because of the increased interest in the neurosurgical treatment of hydrocephalus, we decided to re-evaluate the electroencephalogram in this condition, with particular emphasis on the information contributed by sleep recordings, largely disregarded by other investigators.