[Case of idiopathic hypertrophic pachymeningitis presenting with hyperostosis].

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.