[-A successful case of hypertrophic cranial pachymeningitis treated by optic nerve decompression].

A successful direct operation in a case of hypertrophic cranial pachymeningitis (HCP) is described. A 51-year-old male was admitted with right visual disturbance. CT scanning revealed a mass lesion in the right middle cranial fossa extending into the right orbita. From MRI it was ascertained that this mass lesion consisted of thickening of the skull base dura. The effect of steroids was transient and his visual disturbance was rapidly increasing. A direct operation was performed consisting of partial dissection of the thickening dura and decompression of the right optic nerve. Histological diagnosis showed HCP. After surgery his symptoms dramatically improved. The etiology, natural course and treatment of HCP are well reported in the literature. in the present case the etiology was not clear, but there was a possible relationship with intraorbital pseudotumor or multifocal fibrosclerosis. The reported occasional transitory effect of steroids on HCP and a poor prognosis for visual acuity are common traits in these patients. The authors thus feel that a direct operation should be immediately carried out when the effect of steroids on visual disturbances associated with HCP is judged transient.