腰椎後方除圧手術後に生じる硬膜外血腫と神経症状悪化との関連

Relationship between Postoperative Epidural Hematoma and Neurological Deterioration after Surgical Decompression of the Lumbar Spine

　腰椎後方除圧術後の硬膜外血腫について，どの程度の血腫が術後神経症状の悪化に影響するかを，術後2日目に撮像したMRIを用いて23例で前向きに調査検討した．脊柱管内硬膜外血腫は67.6％，脊柱管外血腫は91.1％に認められ，脊柱管に占める硬膜外血腫の平均面積比は22.1％であった．術後一過性の症状増悪を認めた群の脊柱管内硬膜外血腫面積比は51.4％であり，症状改善が速やかに得られた症例では17.7％であった．硬膜外血腫の症状発症のリスクとなるカットオフ値を41.5％と設定すると，感度100％，特異度93.1％となり，陽性尤度比は14.4と算出された．

　We investigated how much extent of postoperative epidural hematoma resulted in postoperative morbidity. Twenty-three patients, who underwent lumbar decompressive surgery, were prospectively evaluated. A closed suction drainage system was used for postoperative 48 hours in every patients. MRI was obtained after removing the suction drain. The area of the dural sac (AD), intraspinal epidural hematoma (AIH) and extraspinal hematoma (AEH) was measured on axial MRI images with an image-analysis system. The AIH ratio (AIHR)；｛AIH/(AD＋AIH)×100｝was also calculated. Postoperative morbidity and neurological status were evaluated in postoperative two days. Intraspinal and extraspinal hematomas were recognized in 67.6％ and 91.1％. Mean AIHR was made up 22.1％ of the spinal canal after immediate removal of the suction-drain. When the cutoff value of AIHR is assumed to be 41.5％, sensitivity, specificity and positive likelihood ratio become 100％, 93.1％, 14.4.