| A rare brain inflammatory disease with characteristics of thickening of the dura mater of the cranium or spine with at least two histopathological features of IgG4 (immunoglobulin G4) related disease: dense lymphoplasmacytic infiltrate, storiform fibrosis, and/or obliterative phlebitis. Patients typically have non-specific cerebrospinal fluid findings, and might be without systemic involvement or serum IgG4 elevation. Clinical manifestations are caused by mechanical compression of nerve or vascular structure, leading to functional deficit, most commonly headache, cranial nerve palsies, vision problems and motor weakness. |