Idiopathic hypertrophic pachymeningitis: spectrum of the disease.

Hypertrophic pachymeningitis is extremely rare. It is a fibrosing inflammatory process which involves the dura mater, including the tentorium. Numerous pathological entities produce thickening of the pachymeninges, so that idiopathic hypertrophic pachymeningitis is a diagnosis of exclusion. We describe four patients with idiopathic hypertrophic pachymeningitis who had varied clinical presentation. Imaging studies revealed diffuse thickening of the pachymeninges; in one patient there was extensive dural sinus thrombosis. Since no identifiable cause was found, the cases were labelled as idiopathic.