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Spinal Cord Metastases: Unique Findings on Post-gadolinium MRI 2012

General Spine

Jeffrey, B, Rykken, M.D.
Felix, E, Diehn, MD, Non ASSR Member
Christopher, H, Hunt, MD, Non ASSR Member
Laurence, J, Eckel, MD, Non ASSR Member
Kara, M, Schwartz, MD, Non ASSR Member
Christopher, P, Wood, MD, Non ASSR Member

Paper/Mentor

Purpose

Intramedullary metastases to the spinal cord are rare. Our goal was to retrospectively evaluate specific enhancement characteristics on post-gadolinium MRI of a large series of intramedullary spinal cord metastases from a single institution, and to comparatively assess for these features in the more common primary cord neoplasms.

Methods & Materials

Our radiology and clinical databases were used to identify patients with potential intramedullary spinal cord metastases. Exclusion criteria were: lack of confirmed diagnosis (e.g., patients where the clinical differential diagnosis was radiation myelitis/necrosis) and lack of available initial pre-treatment MRI. The initial MRI examinations of the remaining patients underwent consensus review by two neuroradiologists. MRI features that were evaluated included the presence of cystic change/necrosis with surrounding ring enhancement. Additionally, post gadolinium T1-weighted MR images were assessed for the presence of a "capsule" sign (a complete or partial rim of enhancement more intense than the central enhancement of a non-cystic/necrotic lesion), and a "flame" sign (an ill-defined flame-shaped region of enhancement at the superior and/or inferior aspect of an otherwise well-defined lesion). Because these findings were found to be relatively prevalent in these lesions, we sought to comparatively analyze these features in primary cord neoplasms. The radiology and neurosurgery databases were utilized to retrieve patients with pathologically proven primary cord neoplasms in whom pre-operative contrast-enhanced MRI was available. The same MRI features were evaluated in these tumors.

Results

Among 54 total patients with possible cord metastases, 9 were excluded (4 for lack of firm diagnosis, 5 for lack of available initial pre-treatment MRI). The remaining 45 patients (mean age 58.3 +/- 13.5 years) had 65 spinal cord metastases. 36 of 45 (80%) patients presented with a solitary cord metastasis. Lung carcinoma was the most common primary tumor (21 of 45 (47%) patients). For those lesions which received gadolinium, almost all enhanced (58 of 59 (98 %)). There was only one ring enhancing, centrally necrotic/cystic lesion (1 of 58 (2 %)). The "capsule" sign was present in 19 of 58 (33%) of lesions. The "capsule" sign was near-complete-to-completely surrounding the lesion in 13 of 19 (68%), and partially present in 6 of 19 (32%). The "flame" sign was observed in 18 of 58 (31%). The "flame" sign was present at both superior and inferior aspects in 13 of 18 (72%), the inferior aspect only in 4 of 18 (22%), and the superior aspect only in 1 of 18 (6%). 12 of 58 (21%) metastases exhibited both the "capsule" and "flame" signs. 25 of 58 lesions (43%) had either the "capsule" or "flame" sign; on a per-patient basis, at least one sign was present in 24 of the 41 (59%) patients in whom gadolinium was administered. As for the comparison group, this consisted of 32 patients with the following tumors: 19 ependymomas (59%), 8 astrocytomas (25%), and 5 (16%) hemangioblastomas. Intratumoral cystic/necrotic changes with ring enhancement were seen in 17 of 32 (53%) tumors: 15 of 19 (79%) ependymomas, 2 of 8 (25%) astrocytomas, and none of the hemangioblastomas. None of these primary tumors demonstrated either the capsule or flame sign.

Conclusion

In this large series, spinal cord metastases often demonstrated a "capsule" and/or "flame" sign on T1-weighted post-gadolinium MRI. Neither sign was seen in any primary cord tumor in a comparative group of 32 pathologically proven primary spinal cord neoplasms. These signs have not been reported to our knowledge, and among neoplastic cord lesions, appear to be represent specific findings for spinal cord metastases.

References/Financial Disclosures

None.

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