Electroencephalographic findings in experimentally induced intracranial hypertension

Abstract

Unilateral cerebral cortical lesions were made in twenty-six cats by the extradural application of a cold probe to produce cerebral oedema, resulting in increased cerebro-spinal fluid pressure. During these experiments the CSF pressure in one of the lateral ventricles, the arterial and venous blood pressures, respiration, ECG and EEG were recorded continuously. Increased CSF pressure was obtained in 16 of 22 experiments to such a degree that herniation of the brain-stem followed. Four control experiments were performed. This study especially concerns the relationship between the EEG and the changes in CSF pressure. 1. 1. There were no obvious correlations between alterations in the intraventricular pressure and the EEG. 2. 2. We did not find a clear relationship between the extent of the cerebral oedema and EEG changes. 3. 3. Cooling caused the following EEG abnormalities: (a) Slow wave activity largely disappeared during local extradural cooling. The faster rhythmic beta and alpha activities increased, especially from 16 to 20 c/sec, relatively as well as absolutely. (b) On both sides, in frontooccipital derivations, voltage reduction occurred. This was more pronounced on the cooled side, which had a 50% reduction in voltage. This difference continued in most cases after cooling and was probably caused by the local cortical lesion. 4. 4. At the beginning of cerebral herniation the EEG showed gross abnormalities; about 5 min before the respiratory arrest, general slowing of the EEG and reduction of voltage were observed. In most cases the EEG became isoelectric as soon as respiration stopped. After starting artificial respiration electrical activity reappeared after 5–150 sec.