潜在性肺性脳症のP300—肺結核後遺症による軽度呼吸不全例において

P300 Latency in Patients with Respiratory Insufficiency due to Sequelae of Pulmonary Tuberculosis

　潜在性（軽症）肺性脳症の特徴と，その評価法としてのP300の有用性の検討を目的とし，肺結核後遺症による軽度で慢性化した14例の呼吸不全症例を検索した。

　対象患者として，年齢は49〜62歳（平均57.9歳）とし，見かけ上は意識清明で，頭部CTで異常を認めない例を抽出した。初めに聴覚刺激によるP300成分の検出を行い，直後に動脈血PCO₂，PO₂，pHを測定した。次に長谷川式痴呆スケール，mini-mental state，かなひろいテスト，Zungのうつスケール，数唱問題を行った。一方で対照として7例のage-matchedのvolunteerのP300潜時を測定した。

　患者群（平均PCO₂：44.2mmHg，平均PO₂：73.0mmHg，平均pH：7.40）の平均P300潜時（403.6±25.4ms）は対照（357.4±25.4ms）に比して有意（p＜0.01）に延長していた。P300潜時とPCO₂，PO₂，pHの値との間に明らかな相関関係（各r：0.66，−0.59，−0.73）を認め，かなひろいテストとPCO₂，PO₂，pHの値との間にも相関関係を認めた。

　肺結核後遺症による軽度の呼吸不全症例では，しばしば潜在性（軽症）肺性脳症が存在しP300とかなひろいテストはそのような潜在性肺性脳症の検出と評価に有用であることが示唆された。特にP300潜時は血液ガス異常に鋭敏な反応を示した。

We studied latent (mild) pulmonary ence-phalopathy in 14 patients with mild chronic respira-tory insufficiency due to the sequelae of pulmonary tuberculosis. All of the patients were between 49 and 62 (mean age : 57.9). None of them had any impairment of daily activities and apparently had a clear consciousness.

First, the P300 component evoked by auditory stimuli was examined. Immediately after that, the P0₂, PCO₂, pH were measured. Then the Hasegawa's dementia scale, the mini-mental state, the "Kanahiroi" test, Zung's depression score, digit span test were also assessed in the 14 patients. P300 components in 7 age-matched normal volunteerswere also examined and compared with those in the 14 patients.

The mean P300 latency in the patients were significantly prolonged compared with that in the normal volunteers (p＜0.01).

The P300 latency was well correlated with the PCO2, P02, pH. The results of the "Kanahiroi" test also correlated with these parameters.

We suggest that patients with mild respiratory insufficiency due to the sequelae of pulmonary tuber-culosis often have latent (mild) pulmonary ence-phalopathy, and that P300 latency and the "Kanahir-oi" test are very useful to detect and evaluate such latent pulmonary encephalopathy.