IMG-13. Role of diffusion weighted imaging of spine in pediatric brain tumors showing diffusion restriction and CSF metastases

Abstract

INTRODUCTION: Early detection of leptomeningeal metastases (LM) with paediatric brain tumors cases can change the prognosis as well as course of treatment. Conventional MR imaging and CSF (cerebrospinal fluid) analysis plays a vital role in detection of metastases, however, due to certain limitations these can be missed. In our study, diffusion weighed imaging (DWI) of spine was able to bridge this gap and increased the detection rate in MRI equivocal cases in which CSF study was negative. AIMS: To evaluate the incremental value of DWI over the conventional sequences in detection of LM. MATERIALS & METHODS: Paediatric patients with primary brain tumors known to show restriction and propensity for CSF metastasis underwent MRI on 1.5T Philip’s machine. CSF analysis and radiological follow up were used to confirm the diagnosis. RESULTS: Of the 26 patients proven to have LM, linear leptomeningeal metastases (LLP) were seen in 7 patients and nodular leptomeningeal metastases (NLM) were seen in 6 patients and both were seen in 13 patients. Of the 20 patients with LLM, 18 were detected on contrast; however, these were not detected on T2W and DWI except one patient with thick LLP. In 19 patients with NLM, a total of 84 lesions were detected. All were appreciated on contrast with additional 6 lesions which were false positive (FP). Total 96 lesions were detected on T2W, of which 80 were true positive and 16 were FP. About 80 lesions were detected on DWI. Thus, on contrast sequence FP were 6 while on T2W 16 were FP. DISCUSSION: DWI showed a lower FP rate than conventional sequences. CONCLUSION: Contrast sequence remains most reliable sequence for the detection of LM. However, DWI is useful in equivocal cases. The role of DWI in Group 3 and 4 Medulloblastoma with non-enhancing metastases needs to be further explored.