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Neuroradiology Case of the Week

Case 459

November 2009

Hisao Nakamura, MD

Clinical Presentation: The patient is a 46-year-old female with developing brain weakness for the past 2 months.

Imaging Findings: Leptomeningeal metastases of melanoma (multiple bone metastases and epidural metastasis).

Diagnosis: Leptomeningeal metastases

Discussion: The patient is known to have a melanoma. We can find the high-signal intensity on unenhanced T1-weighted image. After administration of contrast media, we can see the diffuse enhancement. Considering the clinical history and other findings (bone metastases and epidural mass and so on), leptomeningeal metastases is more likely. From this case, we would like to score the importance of findings on unenhanced T1-weighted images. Hyper-signal on T1-weighted image is caused by the paramagnetic stable free radicals within the melanin or the paramagnetic hemorrhage. This finding makes inflammatory disease less likely. We have to not only consider the metastasis of melanoma but also to consider the melanin-containing disease, such as primary leptomeningeal melanomatosis, diffuse melanosis or neurocutaneous melanosis, meningeal melanocytoma, and so on.

References:

1. Demir MK, Aker FV, Akinci O, Ozgültekin A. Case 134: primary leptomeningeal melanomatosis. Radiology. 2008 Jun;247(3):905-9. PMID: 18487543 [PubMed]