Over a 12-year period, the authors encountered 2 patients with spinal axis/basimeningeal primitive neuroectodermal tumor (PNET) involving the spinal axis extramedullary, intradural compartment and the basimeninges. In neither patient was an intraaxial focus demonstrated. A 48-year-old woman had computed tomography (CT) findings of hydrocephalus and later abnormal basimeningeal enhancement. Cervical myelography revealed a low cervical intradural block. A 10-year-old boy was evaluated initially with non-contrast-enhanced CT of the brain, which revealed hydrocephalus. Contrast-enhanced CT revealed abnormal basimeningeal enhancement implicating cisternal obstruction. Subsequent magnetic resonance examination of the entire spine with and without gadolinium enhancement revealed diffuse abnormal enhancement of the spinal axis intradural, extramedullary compartment. While intraaxial PNETs are well recognized, the patients described here represent a distinctly unusual pattern of intradural spinal meningeal and basimeningeal infiltration by PNET in the absence of a demonstrable intraaxial lesion.

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