Elsevier

World Neurosurgery

Volume 122, February 2019, Pages 648-655
World Neurosurgery

Case Report
Primary Diffuse Leptomeningeal Melanomatosis: Case Report and Review of the Literature

https://doi.org/10.1016/j.wneu.2018.11.163Get rights and content

Background

Primary diffuse leptomeningeal melanomatosis (PDLM) is an extremely rare pathologic condition that can mimic several other neurologic disease states.

Methods

We report a rare case of PDLM without evidence of a primary focus. In addition, we performed a comprehensive review of the literature to describe all previously reported cases of PDLM.

Results

In the reported case, making the diagnosis of PDLM was difficult. A brain and frontal dural biopsy was nondiagnostic. Computed tomography of the chest, abdomen, and pelvis did not show any distinct solitary mass. After a positron emission tomography scan was performed that showed lumbar sacral enhancement, lumbar dorsal rootlet biopsy was initiated, which was diagnostic of PDLM. Our literature review found 32 previously reported cases of PDLM. Sixteen cases (48.5%) had a distinct focus or mass discovered on imaging workup. The reported case was the seventeenth reported case of PDLM without a distinct focus or mass found on imaging workup.

Conclusions

PDLM is an extremely rare disease, and diagnosis is difficult because of nonspecific clinical, radiographic, and laboratory findings. In approximately half of cases, no distinct mass is shown on imaging workup, which may further complicate diagnosis. PDLM should be on the differential diagnosis for cases of diffuse dural enhancement. Neurosurgical intervention is often limited to ventriculoperitoneal shunting for increased intracranial pressure and dural and cranial biopsy to obtain diagnosis. If the initial biopsy is nondiagnostic, hypermetabolic activity as seen on positron emission tomography may be helpful to find an alternative biopsy site.

Introduction

Primary melanocytic neoplasms originate from the native melanocytes of the leptomeninges.1 When benign neoplastic transformation of these melanocytes occurs, these lesions are known as melanocytomas.2, 3 When malignant, they known as leptomeningeal melanomatoses.2, 3 Clinical manifestations are nonspecific and can mimic a myriad of autoimmune, infectious, and neoplastic causes, complicating diagnosis. We report a rare case of a patient with primary diffuse leptomeningeal melanomatosis (PDLM) without evidence of a primary focus. In addition, we performed a comprehensive review of the literature. Thirty-two cases of PDLM, in addition to the current case, have been previously described in the literature.

Section snippets

Case Description

A 44-year-old white woman with no significant past medical history presented to the emergency department of an outside hospital with confusion, left facial droop, slurred speech, hemiplegia, and hemiparesthesia. A stroke alert was initiated and she was treated with tissue plasminogen activator, although subsequent magnetic resonance imaging (MRI) was negative for stroke. The patient was discharged with a diagnosis of complex migraine headache. Three months later, she was referred to our

Discussion

Melanocytes are embryologically of neural crest origin, and during development, migrate to the leptomeninges, and in particular, the ventral medulla.4 Rarely, leptomeningeal melanocytes may undergo malignant transformation, which is termed leptomeningeal melanomatosis.1 The transformation may diffusely affect the meninges of the entire neuroaxis. The incidence of PDLM is unknown, but extremely uncommon. PDLM may be associated with neurocutaneous syndromes such as neurocutaneous melanosis

Conclusions

PDLM is an extremely rare disease with vague presenting symptoms, radiologic findings, and laboratory results. Diagnosis is therefore elusive, and PET/CT may be a useful diagnostic adjunct. Neurosurgical intervention is limited to CSF diversion for hydrocephalus and biopsy to obtain diagnosis. If PDLM is suspected and initial biopsy is nondiagnostic, a PET scan may localize an additional hypermetabolic site that may be appropriate for a second biopsy with potentially higher yield.

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      Due to the paramagnetic effects of melanin, the typical imaging appearance of primary diffuse leptomeningeal melanomatosis is iso- to hyperintense on T1-weighted images, hypointense on T2-weighted images, and intensely enhanced on gadolinium contrast images [1,4,12,13]. However, signal intensity differs if lesions are amelanotic, which manifests as hypo- to isointense on T1 and iso- to hyperintense on T2 [4,12,13]. Signal patterns also vary depending on melanin content [2,14].

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    Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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