neurocutaneous melanosis

Toddler with
multiple congenital cutaneous nevi on their back. Axial T1 MRI without contrast of the brain shows asymmetrically increased signal intensity in the right mesial temporal lobe (left) and in the right cerebellar hemisphere (right).The diagnosis was neurocutaneous melanosis.
pediatricimaging.org • CC-by-nc-sa 4.0
Toddler with
unusual pigmentation on the back. Clinical image shows a giant nevus covering the entire back.The diagnosis was neurocutaneous melanosis.
pediatricimaging.org • CC-by-nc-sa 4.0
Radiopaedia • CC-by-nc-sa 3.0 • de

Neurocutaneous melanosis or neurocutaneous melanomatosis, is a rare sporadic phakomatosis characterized by multiple congenital cutaneous nevi and meningeal melanocytosis / meningeal melanomatosis.

Epidemiology

Neurocutaneous melanosis tends to be diagnosed in the first few years of life with no gender predilection reported . The condition is most frequently reported in Caucasians .

Clinical presentation

The disease is characterized by multiple melanotic nevi in the skin. Approximately two-thirds of patients have a giant nevus covering the back, known as a "bathing trunk" congenital nevus .

The diagnosis is often made when the child presents with hydrocephalus due to meningeal melanocytosis / meningeal melanomatosis (a.k.a. diffuse melanosis) . Occasionally a delayed presentation occurs towards the end of the second decade, in which case neuropsychiatric presentation is more common .

Diagnostic features have been proposed :

  • unduly large or unusually numerous pigmented nevi in association with leptomeningeal melanosis or melanoma
  • no evidence of malignant change in any of the cutaneous lesions
  • no evidence of malignant melanoma in any organ apart from the meninges

    • Pathology

    It is believed that neurocutaneous melanosis is the result of congenital dysplasia of melanoblasts (melanocyte precursors) which are of neural crest cell origin . These are located in the leptomeninges, optic globes, inner ear, sinonasal cavity, and skin .

    Associations

    Radiographic features

    For leptomeningeal imaging features, please refer to meningeal melanocytosis.

    In addition to or instead of leptomeningeal involvement, parenchymal changes are seen in some individuals characterized by T1 signal hyperintensity involving the mesial temporal lobes (particularly the amygdala), ventral pons and medulla, cerebellum, and inferior frontal lobes . It is believed this is due to melanocytes tracking along perivascular spaces .

    Treatment and prognosis

    Prognosis in symptomatic cases is extremely poor, even in the absence of malignant transformations, particularly when associated with a Dandy-Walker malformation . Hydrocephalus is the most common complication. Involvement of the cord also may result in myelopathy, syringomyelia, and arachnoiditis.

    Malignant transformation of cutaneous nevi is variably reported from 2-13% .

    Malignant transformation of CNS melanosis occurs very frequently, in up to 50% .

    Siehe auch:
    und weiter:
    Assoziationen und Differentialdiagnosen zu neurocutaneous melanosis:
    Subarachnoidalblutung
     
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