Adult male patients who have partial seizures, normal MRI results, and no clear etiology should be tested for NMDAr-Abs to avoid any delays in treatment initiation. Adult female patients who had a seizure as the first symptom are infrequent when NMDAr-Abs encephalitis is diagnosed; additionally, their clinical pattern is different from male patients, with more generalized seizures and rapid development of behavioral and psychiatric symptoms. The differences in hormonal influence could contribute to this difference in clinical pattern.

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ObjectiveTo report the induction of anti–Ma2 antibody–associated paraneoplastic neurologic syndrome (Ma2-PNS) in 6 patients after treatment with immune checkpoint inhibitors (ICIs). We also analyzed (1) patient clinical features compared with a cohort of 44 patients who developed Ma2-PNS without receiving ICI treatment and (2) the frequency of neuronal antibody detection before and after ICI implementation.MethodsRetrospective nationwide study of all patients with Ma2-PNS developed during ICI treatment between 2017 and 2018.ResultsOur series of patients included 5 men and 1 woman (median age, 63 years). The patients were receiving nivolumab (n = 3), pembrolizumab (n = 2), or a combination of nivolumab and ipilimumab (n = 1) for treatment of neoplasms that included lung (n = 4) and kidney (n = 1) cancers and pleural mesothelioma (n = 1). Clinical syndromes comprised a combination of limbic encephalitis and diencephalitis (n = 3), isolated limbic encephalitis (n = 2), and a syndrome characterized by ophthalmoplegia and head drop (n = 1). No significant clinical difference was observed between our 6 patients and the overall cohort of Ma2-PNS cases. Post-ICI Ma2-PNS accounted for 35% of the total 17 Ma2-PNS diagnosed in our center over the 2017–2018 biennium. Eight cases had been detected in the preceding biennium 2015–2016, corresponding to a 112% increase of Ma2-PNS frequency since the implementation of ICIs in France. Despite ICI withdrawal and immunotherapy, 4/6 patients died, and the remaining 2 showed a moderate to severe disability.ConclusionsWe show a clear association between ICI use and increased diagnosis of Ma2-PNS. Physicians need to be aware that ICIs can trigger Ma2-PNS because clinical presentation can be challenging.