A 55-YEAR-OLD WOMAN with a unique form of chronic hypertrophic pachymeningitis involving the posterior fossa and upper cervical spine is reported. Unlike other cases previously described, the clinical picture was dominated by signs of increased intracranial pressure, lower cranial nerve disorders, and a progressive cervical radiculomyelopathy. The diagnosis was made by means of a contrast-enhanced magnetic resonance imaging scan and confirmed by histological examination of the excised dura. Surgical treatment with removal of the hypertrophic dura provided temporary relief, although the natural history of the disease was not modified. Exhaustive bacteriological and histopathological studies failed to identify a specific cause for this diffuse hypertrophy of the cranial and cervical dura. The literature is reviewed, and other histologically documented cases are discussed.