[A Case of Hypertrophic Pachymeningitis with Symptomatic Venous Congestion due to Sinus Stenosis].

We report a patient with hypertrophic pachymeningitis and symptomatic stenosis of the superior sagittal sinus. A 71-year-old man presented with right hemiparesis, sensory-dominant aphasia, and right hemispatial neglect that had been worsening over 2 weeks. Computed tomography showed isodense crescent-shaped lesions deforming the surface of the left cerebral hemisphere, mimicking a subdural hematoma with atypical perifocal edema in the left parietal lobe. Magnetic resonance imaging showed diffuse thickening of the dura mater with contrast enhancement of his left cerebral hemisphere. Histopathological examination of the dural specimen obtained by burr-hole surgery revealed mononuclear inflammatory cell infiltration, and he was diagnosed with hypertrophic pachymeningitis. Dynamic cerebral angiography showed superior sagittal sinus stenosis with reduced venous flow through the left parietal lobe. Administration of high-dose steroid therapy led to neurological improvement. In the case of a subdural mass with atypical parenchymal edema such as a chronic subdural hematoma, other etiology should be taken into consideration.