Intramedullary Spinal Cord Metastasis as Initial Presentation of Malignant Melanoma: A Unique Case Report and Role of Contrast vs Non-contrast MRI in Its Diagnosis.

Intramedullary spinal cord metastasis (ISCM) is a diagnostically challenging and dreadful complication of cancer. Twenty-seven cases of ISCM exclusively related to malignant melanoma have been reported so far in a recent study.On review of literature, we could not find any reported case with ISCM secondary to malignant melanoma as initial presentation. To the best of our knowledge, we are reporting the first such case. We report a case of a 71-year-old lady presenting with gradual onset of bilateral leg weakness "off legs" and lower limb paresthesias. On examination she had an upper motor neuron pattern lower limb weakness with reduced sensations to all modalities and brisk reflexes with extensor plantar responses. She was evaluated with non-contrast MRI (magnetic resonance imaging) spine which showed focal myelopathic cord signal at the conus and at the level of T10 and T11 vertebrae (radiological differential diagnosis given on MRI were B12 deficiency/inflammatory/infection). Thorough radiological scans were ordered which revealed a disseminated malignancy. A biopsy sample from gastric lesion revealed diagnosis of malignant melanoma. A repeat MRI whole spine with gadolinium contrast was done later with suspicion of spinal metastasis which has led to lower limb weakness. MRI with contrast showed an enhancing soft tissue metastatic mass lesion within conus in comparison with plain MRI done one week earlier. At present, diagnostic modalities available for diagnosing ISCM particularly secondary to melanoma do not have high specificity. Contrast MRI is the diagnostic modality of choice at present. Non-contrast MRI has low sensitivity in diagnosis of ISCM compared to contrast MRI and could potentially delay the management, especially in highly aggressive malignancies like malignant melanoma where an early diagnosis and treatment is critical for better outcome.