Findings: Multiple rounded foci of abnormally bright signal are seen in the lentiform nuclei bilaterally, the thalami bilaterally, mesencephalon, and dentate nuclei bilaterally (left greater than right), on FLAIR and T2 weighted images. No abnormal enhancement is seen.

Diagnosis: Neurofibromatosis, Type I.

Discussion: Neurofibromatosis, one of the phakomatoses, is a neurocutaneous disorder inherited in an autosomal dominant pattern. The two most common forms NF-1 and NF-2 have been localized to defects within chromosome 17 and 22, respectively. NF-1 has an incidence of roughly 1:3000 live births. Clinically, NF-1 is diagnosed by the presence of at least two of the following:

1) six or more café-au-lait spots, 2) two or more hemartomas of the iris (Lisch nodules), 3) two or more neurofibromas, 4) one or more plexiform neurofibromas, 5) axillary freckling, 6) one or more bone dysplasias, 7) psuedoarthrosis of a long bone, 8) optic glioma, or 9) a first-degree relative with the diagnosis of NF-1.

Radiologically, cerebellar, brain stem, and cerebral astrocytomas are seen with NF-1. On MR T2 weighted images, patients may have high signal intensity foci in the peduncles or deep gray matter of the cerebellum, brain stem or basal ganglia, as is the case for this patient. These features are believed to represent hamartomas, focal areas of gliosis, wallerian degeneration, neuronal migrational disorders, or possibly neoplasms.

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3. Griffiths PD, Blaser S, Mukonoweshuro W, Armstrong D, Milo-Mason G, Cheung S.
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