Intracranial leptomeningeal metastases: comparison of depiction at FLAIR and contrast-enhanced MR imaging

PURPOSE: To compare contrast material-enhanced T1-weighted and fluid-attenuated inversion-recovery (FLAIR) magnetic resonance (MR) images in depicting leptomeningeal metastases. MATERIALS AND METHODS: Malignant lesions detected at cytologic examination of cerebrospinal fluid in 70 patients were reviewed. There were 58 studies in which both FLAIR and contrast-enhanced T1-weighted spin-echo MR images were available. A senior neuroradiologist reviewed the images from each sequence individually and separately for signs of leptomeningeal metastases and assigned a diagnostic rating of positive, indeterminate, or negative. RESULTS: Leptomeningeal metastases were depicted in 38 cases on contrast-enhanced T1-weighted spin-echo images and in 20 cases on FLAIR images. In three cases, leptomeningeal metastases were detected by using only FLAIR images. In 20 cases, leptomeningeal metastases were detected by using only contrast-enhanced T1-weighted spin-echo images. FLAIR imaging has a sensitivity of 34% for cytologically proved leptomeningeal metastases. Gadolinium-enhanced MR imaging has a sensitivity of 66%. CONCLUSION: Used alone, contrast-enhanced T1-weighted images are better than FLAIR images for detecting leptomeningeal metastases. This is particularly true for cases in which leptomeningeal metastases manifest primarily or solely as cranial nerve involvement.