Leptomeningeal metastases in pediatrics: magnetic resonance image manifestations and correlation with cerebral spinal fluid cytology

Background: Detection of leptomeningeal metastases is fundamental to a complete evaluation of central nervous system (CNS) or non‐CNS tumor with suspected involvement of the neuroaxis. Our purpose was to assess the appearances of different magnetic resonance (MR) sequences in the diagnosis of leptomeningeal metastases and correlate those positive findings with the cerebral spinal fluid (CSF) cytology results. Methods: The authors reviewed the medical records and MR image manifestations of leptomeningeal metastases from 18 children who had positive MR findings and retrospectively correlated them with CSF cytologic results. There was a uniform MR protocol and the patients were examined with the same sequences. Results: The abnormalities included pial‐arachnoid disease (n= 16), disease coating the nerves (n= 12), hydrocephalus (n= 3) and subependymal metastases (n= 2). Enhanced T1 images were better than unenhanced fluid attenuated inversion recovery (FLAIR) and T2 to delineate cranial and spinal leptomeningeal metastases. In our sample, seven out of 18 cases were cytologically negative on a single lumbar puncture. Conclusions: Contrast‐enhanced MR imaging can be invaluable, detecting the false‐negative lumbar punctures. FLAIR and diffusion images can be helpful in diagnosing leptomeningeal metastases of non‐enhancing primary tumors. Prognosis was more related to the primary tumor type than to the leptomeningeal enhancement MR pattern.