Neurocutaneous melanosis associated with inferior vermian hypoplasia: MR findings.

Objective: We describe the MR findings of two cases of neurocutaneous melanosis (NCM) associated with inferior vermian hypoplasia (IVH).

Methods: Two cases of NCM associated with IVH are presented. Both patients had congenital giant hairy nevi and multiple satellite lesions.

Results: Magnetic resonance imaging revealed IVH as well as hyperintensities in the pons and the cerebellar leptomeninges on T1-weighted images. The hyperintensities may be ascribed to the T1-shortening effect of melanin. A right parietal tumor in one patient and unilateral ventriculomegaly in another patient were also depicted.

Conclusions: Magnetic resonance demonstration of the T1-shortening leptomeningeal infiltrations adds weight to the diagnosis of NCM. The implication of the concurrence of NCM and IVH is discussed.