LEPTOMENINGEAL FIBROSIS AND THE DELAYED DIAGNOSIS OF A CENTRAL-NERVOUS-SYSTEM NEOPLASM (PRIMITIVE NEUROECTODERMAL TUMOR)

We report a unique case of histologically confirmed meningeal fibrosis in a child who had progressive ischemic neurologic symptoms before th e delayed diagnosis of an intracranial primitive neuroectodermal tumor (PNET) was made >1 year after initial presentation. This pathology ha s previously been described after neurosurgical procedures, subarachno id hemorrhage, cranial irradiation, and with no known etiology, but ha s never been reported in association with a central nervous system neo plasm. In a 6-year-old boy with headaches of several months' duration MRI demonstrated hydrocephalus, a right cerebellopontine angle cyst, a nd dural enhancement. Biopsies of the thickened meninges taken when th e cyst was surgically fenestrated demonstrated only fibrosis with no e vidence of infection, hemorrhage, or neoplasm. In the next 6 months, t he child had two acute stroke-like episodes with alternating hemipares is that gradually improved. There were ischemic changes in the diencep halon on MRI. Repeat dural biopsies were unchanged. One year after the initial operation, a left hemiparesis recurred and MRI demonstrated m ultiple intracranial masses in the cerebral cortex, cerebellum, supras ellar area, and cauda equina. After surgical resection, the cortical m ass was found to be a PNET. All the lesions regressed after treatment with radiation and chemotherapy. We hypothesize that the meningeal fib rosis represented a ''desmoplastic'' reaction to an occult PNET, simil ar to the fibrous proliferation with cerebellar desmoplastic medullobl astoma except for the extent of the meningeal involvement and the long undetected parenchymal tumor. The mechanism of the ischemic brain inj ury was most likely vascular involvement by the fibrotic process, eith er directly or by predisposition to vasoconstriction. (C) 1997 by Else vier Science Inc.