Uncommon findings in idiopathic hypertrophic cranial pachymeningitis.

BACKGROUND: Idiopathic hypertrophic cranial pachymeningitis (IHCP) is a rare, poorly understood, inflammatory disease, usually involving the dura mater of skull base, tentorium, and falx, and presenting with headache, progressive cranial nerve palsies, and cerebellar dysfunction. PATIENTS AND METHODS: In four patients, the diagnosis of IHCP has been made on the basis of extensive clinical, and radiological investigation, and confirmed by dural biopsy in three patients. The clinical follow-up ranges from 24 to 120 months. RESULTS: At diagnosis, all the patients complained of severe, progressively increasing headache, two had simple or complex partial seizures, but none had cranial nerve palsies. Two patients had electrophysiological evidence of axonal peripheral neuropathy, biopsy-proved in one of them. In all the patients, MRI showed linear or focal thickening of the dura mater of the tentorium and/or of the convexity, sparing the skull base. In one patient, MRI findings resembled chronic subdural hematoma. Dural biopsy demonstrated fibrosis and prominent CD4+ T-cells inflammatory infiltrate. Pachymeningitis was highly responsive to steroid therapy, as was the peripheral neuropathy. In three patients, temporary steroids withdrawal led to dramatic clinical worsening including status epilepticus in one. CONCLUSIONS: In the patients here reported, absence of cranial nerve impairment, seizures, MRI findings resembling chronic subdural hematoma, and association with polineuropathy were unusual findings of IHCP. Moreover, the type of inflammatory infiltrate, lacking in previous reported cases, suggests a probable pathogenetic role for cell-mediated immunity of unknown origin.