Beyond the Typical Atypical Imaging Features of Leptomeningeal Enhancement: A Case Series

Background and Purpose: Contrast-enhanced MRI findings of leptomeningeal enhancement (LME) indicate dysfunction of the blood–brain barrier and can be seen in various neoplastic, infectious, and inflammatory conditions. To the best of our knowledge, systematic evaluation of different patterns of LME remains limited. This case series aims to describe and compare MRI patterns of leptomeningeal enhancement across diverse etiologies. Materials and Methods: We retrospectively evaluated six patients with known or suspected leptomeningeal disease on contrast-enhanced MRI studies of the brain and/or spine with regard to pattern, distribution, localization, and thickness of LME. Results: The patterns of neoplastic causes (glioblastoma, lymphoma, and adenocarcinoma) were characterized by diffuse, thick, and nodular LME, as well as frequently affected cranial nerve and nerve-root involvement. The infections caused various patterns: in cases of tuberculous meningitis, LME was focal and basal in nature, accompanied by parenchymal lesions; whereas in cases of HIV-related meningitis, LME was diffuse and exhibited a pseudocisternogram pattern. The inflammation (suspected neurosarcoidosis) revealed smooth-to-nodular LME with spinal and suprasellar involvement. Conclusions: Although LME patterns are not specific, systematic evaluation of enhancement characteristics may provide useful diagnostic clues and assist in narrowing the differential diagnosis.