AIM To establish the prevalence of central nervous system (CNS) abnormalities on magnetic resonance imaging (MRI) in a population of children with congenital melanocytic naevi (CMN) over the head and/or spine, and to compare this with clinical findings.

RESULTS Nine patients had abnormal clinical neurology, seven had abnormal findings on MRI, and six had both abnormal clinical and radiological findings. Only three of the abnormal MRIs showed features of intracranial melanosis. Three others showed structural brain abnormalities: one choroid plexus papilloma, one cerebellar astrocytoma, and one posterior fossa arachnoid cyst; the first two of these have not previously been described in association with CMN. The last abnormal MRI showed equivocal changes requiring reimaging.

CONCLUSIONS The prevalence of radiological CNS abnormality in this group of children was 7/43. Six of these developed abnormal clinical neurological signs within the first 18 months of life, but two did not do so until after the MRI. Two of the CNS lesions were operable; for this reason we support the routine use of early MRI in this group.