Purpose or Case Report: Leptomeningeal melanocytosis is a rare proliferation of melanocytes in the arachnoid and pia mater that presents as diffuse leptomeningeal enhancement. Findings in a rare case of this disorder are discussed along with differential considerations and diagnostic implications.
Methods & Materials: A 9-year-old male presented to the emergency department after hitting his head on the door of a car. CT of the head performed at that time showed minimal high attenuation material throughout the right parietal cortical reported as a small amount of subarachnoid hemorrhage. After it became clear that the patient was having uncontrolled seizures that may have contributed to the original trauma, he was placed on anti-epileptic medication and referred for MRI.
Results: Multiple MRI's were performed with and without contrast over the next 6 months. The findings on the CT were found to be due to thickening of the leptomeninges which exhibited robust contrast enhancement, greatest in the right parietal lobe. Multifocal hemorrhages were observed in the left cerebral hemisphere over the course of the exams. A diagnosis of Sturge-Weber Syndrome was assigned. Since the leptomeningeal enhancement showed progression over 5 months, a surgical biopsy was performed. Upon entry into the calvarium, the surface of the brain was found to be dark brown in color. Biopsy revealed the diagnosis of leptomeningeal melanocytosis.
Conclusions: Leptomeningeal melanocytosis is a rare disorder that can be confused with infectious, inflammatory, and/or vascular abnormalities. The disease is typically fatal with a short life expectancy following diagnosis. Careful attention on follow-up of leptomeningeal enhancement is essential to exclude a proliferative or neoplastic process.