起立性頭痛を呈さなかった特発性低髄液圧症候群に伴う両側性慢性硬膜下血腫の1例

A Case of Bilateral Chronic Subdural Hematoma due to Spontaneous Intracranial Hypotension without Orthostatic Headache

Ⅰ．はじめに

　低髄液圧症候群は，腰椎穿刺や脊髄手術・外傷後などの髄液の漏出により生じる病態であり，特に，軽微な外傷や何の誘因もなく生じるものは特発性低髄液圧症候群（spontaneous intracranial hypotension：SIH）と称される¹²⁾．多くの症例で起立性頭痛を呈することが臨床的特徴である⁵⁾．

　SIHの10～25%に慢性硬膜下血腫（chronic subdural hematoma：CSDH）を合併する^1,3,8,11)．低髄液圧や脳脊髄液の減少に伴い，脳実質が下方に牽引され二次的に架橋静脈の損傷が起きるためと考えられている^1,11)．若年者で両側性が多く，薄い血腫に比し高度の脳下垂を認め，意識障害が強く出現することがある^4,13)．

　今回，SIHに合併した両側性CSDHの1例を経験した．画像的にはSIHに伴う両側性CSDHの特徴を有したが，比較的高齢の患者で頭部打撲の既往があり，起立性頭痛を呈さなかったため，通常のCSDHとして手術治療を行ったところ，再発を繰り返し，経過中にSIHと診断された．この経験をもとに，CSDHにおいて初診時にSIHを鑑別に挙げる重要性と治療における留意点について論じる．

　We herein present a case of bilateral chronic subdural hematoma（bilateral CSDH）caused by spontaneous intracranial hypotension（SIH）without orthostatic headache. A 67-year-old male patient with mild head injury suffered from a chronic, non-postural headache. Computed tomography of the brain showed bilateral CSDH. The hematomas were surgically evacuated using a closed drainage method. His headache immediately disappeared, but it recurred after 2 weeks. We further performed hematoma irrigation；however, his neurological status deteriorated with the development of pneumocephalus. Magnetic resonance imaging with gadolinium-DTPA showed diffuse pachymeningeal enhancement. His cerebrospinal fluid pressure was 3cmH₂O, and radioisotope cisternography revealed cerebrospinal fluid leakage at the level of the cervicothoracic transition. No recurrence was found after 6 weeks of horizontal bed rest. The possibility of SIH should be considered in patients with CSDH, especially bilateral CSDH, even in elderly patients with a history of mild head trauma, and absence of orthostatic headache. Closed drainage method may be preferable in cases where surgical treatment is used.