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Neurological Surgery No Shinkei Geka Volume 41, Issue 1 （January 2013）

Neurological Surgery 脳神経外科 41巻1号（2013年1月発行）

Japanese English

研究

Evans indexが0.3以下であったが，iNPHと考え髄液シャント術を施行した14例 Post-operative Improvement of 14 Cases who were Considered iNPH despite Evans' Index of 0.3 or Less 成瀬裕恒 ¹ , 松岡好美 ¹ Hirotsune NARUSE ¹ , Yoshimi MATSUOKA ¹ ¹和泉市立病院脳神経外科 ¹Department of Neurosurgery, Izumi Municipal Hospital キーワード： idiopathic normal pressure hydrocephalus , Evans' index , Sylvian index , coronal ventricular index Keyword: idiopathic normal pressure hydrocephalus , Evans' index , Sylvian index , coronal ventricular index pp.25-30

発行日 2013年1月10日 Published Date 2013/1/10

DOI https://doi.org/10.11477/mf.1436101905

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参考文献 Reference

Ⅰ．はじめに

　「特発性正常圧水頭症（idiopathic normal pressure hydrocephalus：iNPH）診療ガイドライン」（第2版）によれば，iNPHの特徴的な画像所見として脳室拡大，シルビウス裂拡大，高位円蓋部のくも膜下腔狭小化，後交連を通る冠状断において脳梁角が急峻であることが挙げられている^4,5,9)．実際の臨床場面では，画像所見において脳室拡大は明らかではないが，症状・病歴からiNPHが疑われる例を経験することがある．今回われわれは，術前にEvans indexが0.3以下であったが，タップテスト後に症状の改善が認められ，髄液シャント術を施行した14症例について検討を行った．

　Background and Purpose:The diagnosis of idiopathic normal pressure hydrocephalus (iNPH) is based on ventricular enlargement with the Evans' index (＞0.3). Cerebrospinal fluid (CSF) shunt surgery was performed for 14 patients (5 men and 9 women;mean age, 73.8 years;range, 61-80 years) who showed improvement after CSF tap test despite Evans' index of 0.3 or less. We evaluated Evans' index, sylvian fissure, and cerebral ventricular size on the coronal sections obtained perpendicularly to the antero-posterior commissure line before and 3 months after surgery.

　Results:Of the 14 patients, 9 (64%) had marked improvement and 5 (36%) showed mild improvement. Evans' index remained unchanged in patients with marked improvement. The sizes of Sylvian fissures and lateral cerebral ventricles on the coronal sectional imaging were markedly reduced.

　Discussion and Conclusion:Some patients with Evans' index of 0.3 or less might show improvements in symptoms after the surgery;thus, the CSF tap test should be performed when iNPH is suspected based on the symptoms and medical history. Characteristic imaging findings of iNPH include enlarged Sylvian fissure, tight high-convexity, and small callosal angle on the coronal section passing through the posterior commissure, indicating that the lateral cerebral ventricle is located disproportionately in the upper medial part. Cerebral ventricles might enlarge in the direction of the long axis instead of externally in iNPH. In iNPH, Evans' index, which indicates external enlargement, is not appropriate for evaluating ventricular enlargement;alternatively, the size of cerebral ventricles estimated by coronal sections can be used.