[EEG changes associated with cranial tumours, bone defects and cranioplasties (author's transl)].

Eighteen patients with skull defects after neurosurgical operations underwent electroencephalographic investigations. Six patients in whom skull tumours had been removed did not show any postoperative changes, when compared with the pre-operative EEG. Twelve patients in whom bone defects had been closed with alloplastic materials showed no changes in the basic frequency, and no focus or signs of general slowing. In three cases only, the amplitudes were decreased in the postoperative EEG follow-up. For routine clinical practice one may conclude that in the region of bone defects higher amplitudes can be seen and, in addition, brain pulsations may present as a biological artefact. Non-space-occupying lesions of the skull and alloplastic materials do not, as a rule, produce any EEG disturbances.