プラトウ波出現時における脳機能—脳波パワースペクトル解析による検討

BRAIN FUNCTION IN PATIENTS WITH PLATEAU WAVES STUDIED BY COMPRESSED SPECTRAL ARRAY IN LONG-TERM EEG MONITORING

　抄録　頭蓋内圧の連続記録において典型的なプラトウ波を認めた3例について頭蓋内圧，全身血圧，脳波解析の同時記録を行ない，その相互関係を検索した。3例ともに，プラトウ波出現時，頭蓋内圧の著しい上昇にもかかわらず全身血圧は変化をみず，結果としてこの時期に全身血圧と頭蓋内圧の差である脳灌流圧の著しい低下をみた。脳波の周波数スペクトル解析では徐波成分の出現は間歇的で，わずかであり，α波帯域，あるいは速波を主体とした成分の増加が著しくみられた。この脳波解析の所見はプラトウ波出現時，患者が多くの場合，著しい脳灌流圧の低下にもかかわらず意識は清明であり，脳幹の乏血に由来するCushing現象をともなわない事実を説明すると思われたが，従来報告されている脳灌流圧の低下によってひきおこされる脳血流の低下を反映する所見に乏しいものであった。今回のえられた知見からプラトウ波の発現に関与する脳部位として橋脳の重要性を推定した。

The intracranial pressure, systemic blood pres-sure and compressed spectral array in EEG mo-nitoring 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 in-cluded. 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 dor-salis pedis artery. To obtain continuous and com-pressed spectral array in the EEG, Berg-Fourier Analyzer by the OET-Biomedica Company of Italy was used. Simultaneous recordings of the intracra-nial 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 va-sopressor response and impairment of conscious-ness, but complained only headache. The spect-rograms in these patients were characterized by a constant and predominant activity in the alpha or high frequencies. This structual aspect was re-tained throughout the continuation of plateau wa-ves. The power of low frequencies only appeared transiently. The results suggest that some mecha-nisms producing and maintaining the fast and/or alpha wave activity may participate in the recur-rent appearance of plateau waves.