Classification of neurological abnormalities in children with congenital melanocytic naevus syndrome identifies magnetic resonance imaging as the best predictor of clinical outcome

Summary

Background

The spectrum of central nervous system ( CNS) abnormalities described in association with congenital melanocytic naevi ( CMN) includes congenital, acquired, melanotic and nonmelanotic pathology. Historically, symptomatic CNS abnormalities were considered to carry a poor prognosis, although studies from large centres have suggested a much wider variation in outcome.

Objectives

To establish whether routine MRI of the CNS is a clinically relevant investigation in children with multiple CMN (more than one at birth), and to subclassify radiological abnormalities.

Methods

Of 376 patients seen between 1991 and 2013, 289 fulfilled our criterion for a single screening CNS MRI, which since 2008 has been more than one CMN at birth, independent of size and site of the largest naevus. Cutaneous phenotyping and radiological variables were combined in a multiple regression model of long‐term outcome measures (abnormal neurodevelopment, seizures, requirement for neurosurgery).

Results

Twenty‐one per cent of children with multiple CMN had an abnormal MRI. Abnormal MRI was the most significant predictor of all outcome measures. Abnormalities were subclassified into group 1 ‘intraparenchymal melanosis alone’ ( n = 28) and group 2 ‘all other pathology’ ( n = 18). Group 1 was not associated with malignancy or death during the study period, even when symptomatic with seizures or developmental delay, whereas group 2 showed a much more complex picture, requiring individual assessment.

Conclusions

For screening for congenital neurological lesions a single MRI in multiple CMN is a clinically relevant strategy. Any child with a stepwise change in neurological/developmental symptoms or signs should have an MRI with contrast of the brain and spine to look for new CNS melanoma.

Abstract

What's already known about this topic?

• Multiple congenital melanocytic naevi (CMN; more than one lesion at birth) can be associated with abnormalities of the central nervous system (CNS). The spectrum of these abnormalities includes congenital and acquired pathologies, melanotic and nonmelanotic lesions, rendering the term ‘CMN syndrome’ more appropriate than ‘neurocutaneous melanosis’.

• Symptomatic CNS abnormalities were previously thought to carry a universally poor prognosis, although cohort data in the last decade have argued against this.

What does this study add?

• A single CNS magnetic resonance imaging scan in multiple CMN, independent of projected adult size or site of the largest naevus, and ideally in the first 6 months of life, is currently an appropriate screening strategy.

• An abnormal result is a better statistical predictor of clinical outcome than cutaneous phenotype.

• Clinical management is altered as a result of the radiological result.