Clinical
Presentation: Patient is a 46-year-old female with known malignant melanoma who had brain metastasis.
Imaging Findings: An oval-shaped lesion measuring 24x28 mm is seen in the cervical spinal cord at the level of C5-C6 vertebrae, causing mild expansion of the cord. The lesion has well defined margin and has large perilesional edema extending from cervicomedullary junction to T11 level. In post-contrast images, strong and inhomogeneous enhancement of the lesion is present. Degenerative changes are seen at C5-C6 level with moderate canal narrowing.
Figure 1: Sagittal T1W image shows mild cord expansion at C5-C6 level. The lesion is isointense to cord. Edema is seen as subtle hypointensity in the cord.
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Figures 2A-C: The lesion is isointense to cord in T2W images and has well-defined margin. Large perilesional edema is seen in cervical spinal cord (Fig. 2b), extending from cervicomedullary junction. The edema is disproportionate for the lesion.
Figures 3A-B: The lesion shows strong, inhomogeneous enhancement in post-contrast T1W images.
Diagnosis: Intramedullary metastases from malignant melanoma to cervical spinal cord
Discussion: Intramedullary spinal metastases are rare, occurring in only 0.9%—2.1% of autopsied cancer patients. They are most commonly located in the cervical cord (45% of cases), followed by the thoracic cord (35%) and the lumbar region (8%). Most metastases are solitary, with an average length of two to three vertebral segments. Lung carcinoma (40%—85% of cases) is the most common primary site, followed by breast carcinoma (11%), melanoma (5%), renal cell carcinoma (4%), colorectal carcinoma (3%), and lymphoma (3%); 5% of the primary sites are unknown. Documented routes of spread include hematogenous (via the arterial supply) and direct extension from the leptomeninges. Extension along the Batson venous plexus for retroperitoneal primary tumors or extension along perineural lymphatic ducts is also a theoretic possibility [1].
Virtually all patients have motor weakness. Pain (70% of cases), bowel or bladder dysfunction (60%), and paresthesia (50%) are other common clinical manifestations. A rapid decline in neurologic status in an elderly patient is typical. In contrast to the long duration of symptoms that accompany primary intramedullary spinal neoplasms, most patients with a spinal cord metastasis (75%) have symptoms for less than one month before diagnosis [1].
Radiographs are usually normal in patients with intramedullary spinal metastases. Even with myelography, up to 40% of cases are undetected. MR imaging is superior to other modalities. Lesions typically produce mild cord expansion over several segments. Cysts are rare, in contrast to primary intramedullary neoplasms. Cord metastases often have generous amounts of surrounding edema, often disproportionately increased for the size of the lesion [1].
Spinal cord melanoma usually shows slightly increased signal intensity on T1-weighted images relative to that of the spinal cord. On T2-weighted images, it can demonstrate the same or low signal intensity compared with that of the normal cord. After the intravenous administration of a gadolinium-based contrast agent, the lesion most often shows mild and homogeneous enhancement [2].
Generally, hyperintensity on T1-weighted images may be due to the presence of melanin, as well as hemorrhage or fat. The signal intensity features of melanoma on T1- and T2-weighted images are thought to be caused by the paramagnetic stable free radicals that exist within melanin or the paramagnetic products of hemorrhage. Foci of hemorrhage also may occur in malignant melanoma and can modify the signal intensity features on MR images. Moreover, a subacute or chronic hemorrhage in the tumor may influence the MR imaging pattern to a greater extent than does melanin, resulting in variable signal intensity in the tumor. The distinction between melanin and methemoglobin based on MR images is difficult, because both have similar relaxation characteristics. Foci of hemorrhage may occur not only in melanoma but also in other malignant tumors of the spinal cord; thus, the differentiation of such a tumor from other types of intramedullary malignant lesions is difficult, and the MR pattern easily can suggest an erroneous diagnosis [2].
The prognosis for patients with intramedullary metastases is dismal: Two-thirds of these patients die within six months. Until recently, radiation therapy was advocated as the only treatment for these patients with systemic disease. Some investigators, however, have recommended microsurgical resection for discrete, well-defined lesions to improve the quality of remaining life. Radiation therapy and corticosteroid therapy are still the treatments of choice for metastasis from a radiosensitive primary tumor or in the setting of diffuse and widespread disease [1].
References:
Koeller KK, Rosenblum RS, Morrison AL. Neoplasms of the spinal cord and filum terminale: radiologic-pathologic correlation. Radiographics. 2000 Nov-Dec;20(6):1721-49. PMID: 11112826 [PubMed]
Farrokh D, Fransen P, Faverly D. MR findings of a primary intramedullary malignant melanoma: case report and literature review. AJNR Am J Neuroradiol. 2001 Nov-Dec;22(10):1864-6. PMID: 11733317 [PubMed]
