[Diffusion-weighted MR imaging of meningeal involvement in Wegener's granulomatosis]

We report a 65-year-old female with meningeal involvement in Wegener's granulomatosis (WG). At 52 years of age, she was diagnosed as having WG by lung biopsy and elevated proteinase3 anti-neutrophil cytoplasmic antibody titer. She had been maintained on prednisolone. Three weeks before admission, she developed deterioration of mental status. On examination, neurological abnormalities included right hemiparesis, confusion, memory loss, psychomotor slowing and agraphia. CSF was normal. Diffusion-weighted images (DWI) showed high intensity lesions in the subarachnoid space over the left hemisphere. Fluid attenuated inversion recovery (FLAIR) images showed high intensity signal in the subarachnoid space with mild swelling of the cortex and abnormal meningeal enhancement corresponding to the high intensity area on DWI. She was treated with intravenous administration of methylprednisolone (1,000 mg/day for 3 days) and cyclophosphamide, and gradually improved in symptoms and abnormal hyperintensity on DWI. Involvement of the meninges in WG is rare. The dura mater is involved more frequently than the pia mater. Pathological findings of the meninges in WG has been reported to be granulomatous inflammation. Restricted diffusion in the subarachnoid space has been described to occur in a viscous mixture of proteins and inflammatory cells, similarly to the DWI hyperintensity in pyogenic abscesses. In our case, abnormal hyperintensity on DWI was interpreted as a dense inflammatory infiltrate in the leptomeninges. Therefore, DWI and FLAIR image have been shown to be useful for demonstration of leptomeningeal lesions in WG.