[Brain function in patients with plateau waves studied by compressed spectral array in long-term EEG monitoring].

The intracranial pressure, systemic blood pressure and compressed spectral array in EEG monitoring were studied in three patients with typical plateau waves in continuous intracranial pressure recordings. Two patients with brain-tumor and one patient with aqueductal stenosis were included. The intracranial pressure was recorded through an indwelling ventricular catheter attached to a pressure transducer. The systemic blood pressure was recorded through an intraarterial catheter placed in the femoral artery or the dorsalis pedis artery. To obtain continuous and compressed spectral array in the EEG, Berg-Fourier Analyzer by the OET-Biomedica Company of Italy was used. Simultaneous recordings of the intracranial pressure, systemic blood pressure and EEG spectral analysis were made for 180 minutes in each patient. During the plateau waves, the systemic blood pressure did not rise in spite of a marked increase in intracranial pressure, resulting in a marked decrease in the cerebral perfusion pressure. The patients, however, showed no clinical symptoms resulting from ischemia of the brain, such as vasopressor response and impairment of consciousness, but complained only headache. The spectrograms in these patients were characterized by a constant and predominant activity in the alpha or high frequencies. This structural aspect was retained throughout the continuation of plateau waves. The power of low frequencies only appeared transiently. The results suggest that some mechanisms producing and maintaining the fast and/or alpha wave activity may participate in the recurrent appearance of plateau waves.