Neurocutaneous Melanosis Associated with Dandy-Walker Malformation

Abstract

Neurocutaneous melanosis is a rare dysmorphogenesis associated with single or multiple giant pigmented cutaneous nevi and diffuse involvement of the leptomeninges anywhere in the central nervous system (CNS). It is interesting that almost 8–10% of patients had associated Dandy-Walker malformation in the literature, suggesting a common origin of the developmental abnormalities. In this article, we present a 2-year-old patient with neurocutaneous melanosis associated with Dandy-Walker malformation. We reviewed the literature and discuss the pathogenesis based on the preferred hypotheses so far.

Dandy-Walker Malformation Associated with Neurocutaneous Melanosis

“…A few more than 100 cases have been published so far [1][2][3][4][5]10,11,[13][14][15][16]18,19) . This disease is characterized by one or multiple large congenital melanocytic nevi and diffuse or nodular leptomeningeal involvement of melanocytes.…”

“…According to above criteria, our case was compatible to diagnosis for neurocutaneous melanosis (large nevus greater than 6 cm in and hemispheric dysgenesis, compression and rotation of the cerebellum and brain stem, retrocerebellar cysts, and extra-axial anomalies of the posterior fossa. In addition, the T1 shortening of the involved structures (hyperintensity on T1-weighted images) is due to the presence of pathologic involvement of the brain and leptomeninges by melanin pigment deposition 2,4,5,11,[14][15][16] . Calcium, blood, and fat are the other causes of T1 shortening on MRI, but these can be eliminated by CT 2) .…”

“…Although the pathogenesis of neurocutaneous melanosis has not been elucidated, theories focus on defective morphogenesis of the neural ectoderm in the developing embryo [1][2][3][4][5]8,[10][11][12][13][14][15] . Melanocytes of the skin and pia mater are believed to be derived from multipotential precursor cells of the neural crest.…”

“…Whether the ventricular outlet is obstructed or not, the dysgenesis of the cerebellum and fourth ventricle may result in the gradual accumulation of CSF in the posterior fossa, but still allow absorption in a critical equilibrium because of the relatively high-pressure gradient between the CSF pathway and the venous compartment. The physiological increase in systemic blood pressure after birth results in a decreased pressure gradient and a disruption of the absorption of CSF, leading to hydrocephalus [1][2][3][4][5]7,[10][11][12][13][14]18,19) . At least 100 cases of neurocutaneous melanosis have been reported; in 15 cases, there were associations between DandyWalker malformation and neurocutaneous melanosis [1][2][3][4][10][11][12][13][14][15][16]18,19) .…”

“…Neurocutaneous melanosis is a rare dysmorphogenesis that is associated with single and multiple giant pigmented cutaneous nevi and the involvement of benign and/or malignant melanocytic tumors of the leptomeninges. After the first description by Rokitansky 17) , around 100 cases of neurocutaneous melanosis have been reported in the literature [1][2][3]5,10,11,[13][14][15][16]18,19) . Eight to 10% of these were associated with Dandy-Walker malformation, indicating a common origin of these developmental abnormalities [1][2][3]7,10,11,13,14,18,19) .…”