The Association of Chiari Type I Malformation and Neurofibromatosis Type 1

The association of neurofibromatosis type 1 (NF1) with Chiari malformations of the cerebellum and brain stem has been reported on only two previous occasions.1,2 The pathogenesis of both conditions has remained unclear, although the Chiari type I malformation is most likely due to hypoplasia of the posterior fossa with subsequent extension of the cerebellum through the foramen magnum.3 NF1 is also associated with a variety of cerebral dysplasias.4 We present a patient with both of these dysplastic lesions whose Chiari malformation was asymptomatic.