Postoperative evaluation for disseminated medulloblastoma involving the spine: contrast-enhanced MR findings, CSF cytologic analysis, timing of disease occurrence, and patient outcomes.

BACKGROUND AND
PURPOSE: Postoperative MR imaging is routinely performed for staging of medulloblastoma because of frequent tumor dissemination along CSF pathways. The goals of this study were to: 1) determine the timing of disease occurrence and contrast-enhanced MR imaging features of disseminated medulloblastoma involving the spine and their relationship to patient outcomes; and 2) compare the diagnostic accuracy of MR imaging findings with CSF cytologic analysis.
METHODS: Medical records, pathologic reports, and unenhanced and contrast-enhanced postoperative MR images of the spine and head from 112 patients who had resection of medulloblastoma were retrospectively reviewed. MR images of the spine were evaluated for abnormal contrast enhancement in the meninges and vertebral bone marrow. MR images of the head were evaluated for recurrent or residual intracranial tumor. Imaging data were correlated with available CSF cytologic results and patient outcomes.
RESULTS: Twelve patients (11%) had tumor within the spinal leptomeninges depicted on MR images at the time of diagnosis. Twenty-five patients (22%) had disseminated disease in the spine (leptomeninges, n = 22; vertebral marrow, n = 1; or both locations, n = 2) on MR images 2 months to 5.5 years (mean, 2 years) after initial surgery and earlier negative imaging examinations. Eleven other patients (10%) had recurrent intracranial medulloblastoma without spinal involvement seen with MR imaging. Spinal MR imaging had a sensitivity of 83% in the detection of disseminated tumor, whereas contemporaneous CSF cytologic analysis had a sensitivity of 60%. The sensitivity of CSF cytologic analysis increased to 78% with acquisition of multiple subsequent samples, although diagnosis would have been delayed by more than 6 months compared with diagnosis by spinal MR imaging in six patients. Spinal MR imaging was found to have greater overall diagnostic accuracy than CSF cytologic analysis in the early detection of disseminated tumor (P = .03). Spinal MR imaging confirmed disseminated tumor when contemporaneous CSF cytologic findings were negative in 13 patients, whereas the opposite situation occurred in only two patients. False-positive results for spinal MR imaging and CSF cytologic analysis occurred when these examinations were obtained earlier than 2 weeks after surgery. The 5-year survival probability for patients with spinal tumor was 0.24 +/- 0.08 versus 0.68 +/- 0.05 for the entire study group.
CONCLUSION: Spinal MR imaging was found to have greater diagnostic accuracy than CSF cytologic analysis in the early detection of disseminated medulloblastoma. CSF cytologic analysis infrequently confirmed disseminated tumor when spinal MR imaging results were negative. Delaying spinal MR imaging and CSF cytologic analysis by more than 2 weeks after surgery can reduce false-positive results for both methods. The presence of disseminated medulloblastoma in the spine seen with MR imaging is associated with a poor prognosis.