All that glitters is not gold: The importance of ruling out other causes of leptomeningeal enhancement on MRI that may resemble leptomeningeal disease (LMD).

e14018 Background: Leptomeningeal metastatic disease (LMD) is increasingly common entity which at times, in the proper clinical context, can be diagnosed based on MRI imaging findings without CSF confirmation of positive CSF cytology, CSF genomics or CSF Circulating Tumor Cells (CTCs). CSF studies remain very insensitive, LMD treatments are very invasive (e.g. cranial spinal RT, intra-thecal therapy, Ommaya reservoir placement etc.) and therefore it is critical to carefully consider non-LMD causes of meningeal enhancement. The imaging findings may include linear or nodular enhancement of the sub arachnoid space, hydrocephalus, or cranial nerve enhancement. As these findings are non-specific and appear with other disease processes, we studied these in a single institutional case series at the Moffitt Cancer Center. Methods: In this single institution retrospective analysis, Neuro-oncology Tumor Board records from 2021-2025 at Moffitt Cancer Center were reviewed for cases in which LMD was initially considered by imaging, but whose imaging findings were subsequently shown to be from an alternative and often reversible diagnosis. Results: We identified a total of 13 patients whose leptomeningeal enhancement were due to causes other than LMD. Three (23%) had acute ischemia and with accompanying luxury perfusion, three (23%) had acute venous occlusion or compression, two (15%) were due to posterior reversible encephalopathy syndrome (PRES), two (15%) were caused by status epilepticus (including one with non-convulsive status epilepticus), and one each (7%) due cryptococcal meningitis, laminar necrosis from remote ischemia and intracranial hypotension. In 12 (92%) patients had improvement/resolution of the radiographic abnormalities on subsequent examinations and other relevant studies (e.g. CSF microbiological studies showing cryptococcus with institution of anti-biotics). The one (8%) patient that didn’t improve radiographically had chronic infarction with laminar necrosis which was unchanged. Conclusions: Leptomeningeal enhancement in cancer patients has other often treatable causes other than LMD. In addition to CSF cytology & genomics we routinely order infectious and cytokine panels to rule out infectious or inflammatory causes and EEGs. Other etiologies besides LMD should be considered when investigating possible LMD on MRI. Follow up imaging and Neurology consultations are essential. In our patient population and the small sample size we did not encounter other inflammatory diseases such as MS, other autoimmune diseases or other CNS infections such as HIV, etc.