Characteristic magnetic resonance imaging of leptomeningeal metastases of lung adenocarcinoma: Fluid‐attenuated inversion recovery and diffusion‐weighted imaging hyperintensity on brainstem surfaces

Cytology of cerebrospinal fluid is the gold standard for diagnosing leptomeningeal carcinomatosis, despite its low sensitivity. Herein, we report a case of leptomeningeal carcinomatosis in a patient with relapsed lung adenocarcinoma who presented with tinnitus and hearing loss for 3 months. Magnetic resonance imaging revealed characteristic fluid‐attenuated inversion recovery and diffusion‐weighted imaging hyperintensities along the leptomeningeal surfaces of the brainstem. The ratio of the concentration of carcinoembryonic antigen in the serum and cerebrospinal fluid was 1.2:1. The cerebrospinal fluid cytology obtained at the fourth lumbar puncture revealed suspected malignancy, and a definitive diagnosis of metastatic adenocarcinoma was confirmed via brain biopsy. This case supports the utility of characteristic magnetic resonance imaging appearance and repeated lumber punctures as an evaluation for leptomeningeal carcinomatosis.