骨肥厚を伴う肥厚性硬膜炎の1例

A Case of Idiopathic Hypertrophic Pachymeningitis Presenting with Hyperostosis

Ⅰ．はじめに

　特発性肥厚性硬膜炎（idiopathic hypertrophic pachymeningitis：IHP）は，原因不明で硬膜が局所的またはびまん性に肥厚し，頭痛・多発性脳神経障害・失調などを呈する比較的稀な疾患である．一方，何らかの基礎疾患（梅毒，結核，真菌症，HTLV-1，関節リウマチ，Wegener肉芽腫，sarcoidosisなど）を有する続発性肥厚性硬膜炎も存在し，硬膜が肥厚し造影剤で増強される病態として，その他にもさまざまな疾患があり鑑別を要する．今回われわれは，頭痛で発症し，蝶形骨の肥厚とその周辺硬膜の肥厚がみられ，手術，病理組織で骨変化を伴うIHPと診断した症例を経験した．骨変化を伴ったIHPの報告は，渉猟し得た範囲で自験例を含めこれまでに4例しか見あたらず，文献的考察を加え報告する．

　We report a case of idiopathic hypertrophic pachymeningitis presenting with cranial hyperostosis. A 64-year-old man had suffered from pulsating headache during the last 3 months. CT showed bony thickening of the sphenoid ridge, and MRI with Gd-DTPA revealed a linear or nodular enhanced mass along the left sphenoid ridge, extending to the anterior and middle cranial fossae and cavernous sinus. Preoperative steroid therapy resulted in improved clinical symptoms and shrinkage of the enhanced lesion. To clarify the nature of the lesion, biopsy was performed. Granulation tissue infiltrated by lymphocytes and plasma cells was identified, suggesting inflammatory changes. Histologic examination of the cranial bone showed fibrosis in the bone marrow. We considered the hyperostosis to have resulted from a long-term nonspecific inflammatory reaction. Idiopathic hypertrophic pachymeningitis associated with skull changes is rare. There are only 4 reported cases including ours. This rare condition is important in the differential diagnosis of cranial hyperostosis.