Neurocutaneous melanosis

Neurocutaneous melanosis, or neurocutaneous melanomatosis, is a rare sporadic phakomatosis.

The disease is characterised by melanoytic naevi in skin and brain (40-60%). Melanoblasts from neural crest cells are present in the leptomeninges, eye globes, inner ear, sinonasal cavity and skin 

Usually the disease is discovered in childhood due to intracranial haemorrhage, or hydrocephalous from blocked arachnoid villi. 

Giant cutaneous naevi are present. Malignant transformation of cutaneous naevi is uncommon. Malignant transformation of CNS melanosis occurs in up to 50%.

Prognosis in symptomatic cases is extremely poor, even in the absence of malignant transformations.

Features for diagnosis have been proposed 2:

  1. unduly large or unusually numerous pigmented nevi in association with leptomeningeal melanosis or melanoma
  2. no evidence of malignant change in any of the cutaneous lesions
  3. no evidence of malignant melanoma in any organ apart from the meninges
  • hyperdensity (due to melanin) outlining sulci
  • melanin may be seen on unenhanced T1W MRI as hyperintensity
  • diffuse enhancement of meninges in brain and spine (20%)
  • hydrocephalous
  • syringomyelia

Hyperdense outline of sulci on CT can mimic subarachnoid haemorrhage.

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Article Information

rID: 25472
Synonyms or Alternate Spellings:
  • Neurocutaneous melanomatosis

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