Idiopathic Hypertrophic Pachymeningitis Mimicking Meningioma with Occlusion of Superior Sagittal Sinus: Case Report and Review of Literature.

BACKGROUND: Idiopathic hypertrophic pachymeningitis is a rare inflammatory condition with diffuse thickening of the dura mater, which may cause a compressive effect or vascular compromise. CASE DESCRIPTION: A 40-year-old Chinese man presented with persistent headache for 5 months and a sudden epileptic seizure 2 days ago. Magnetic resonance imaging demonstrated a large (71 x 34 x 27 mm) extra-axial mass at the right frontal convexity with severe edema mimicking meningioma. The lesion and peripheral dura mater showed contrast enhancement. Additionally, the skull near the lesion was eroded. Meningioma was diagnosed, and the patient underwent surgery. During the operation, we found the lesion texture was very tough, and the superior sagittal sinus was occluded. Histopathologic findings revealed a large number of infiltrated lymphocytes with fibrosis and microabscess formation; intracranial idiopathic hypertrophic pachymeningitis was diagnosed. Follow-up magnetic resonance imaging performed 3 months after surgery demonstrated the enhancement was notably alleviated. CONCLUSIONS: Idiopathic hypertrophic pachymeningitis should be part of the differential diagnosis of some cases of meningioma.