Neuroleptic intolerance in the context of anti-N-methyl-D-aspartate receptor encephalitis: A systematic review and synthesis of global case reports

Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis presents commonly with psychiatric symptoms. One cohort of these patients reported that antipsychotic administration led to neuroleptic intolerance (NI) in 19% of them, which was preventable by a prompt encephalitis diagnosis. To date, there is no clear description of the "neuroleptic intolerance" spectrum in general or during anti-NMDAR encephalitis. We aimed to synthesize epidemiological and clinical characteristics of patients with NI and confirmed anti-NMDAR encephalitis, the time to the encephalitis diagnosis, the disease course, outcomes at discharge, and associated factors. We systematically searched three databases, to include clinical cases, case series, and observational studies. Additionally, we reported one clinical case. Results were summarized using narrative synthesis and the quality of the included studies was assessed. We included 22 records representing 40 patients (28 females; mean age, 24.6). Overall, the evidence quality was low. Initially, most cases were admitted in psychiatric wards (70%) with purely psychiatric symptoms (37.5%). However, most of them developed subtle concomitant neurological symptoms. The mean time to anti-NMDAR encephalitis diagnosis was 26.7 days, which was triggered by the NI in six patients. We found no association between clinical variables as delayed diagnosis, admission to psychiatric wards or the presence of malignancy with outcome variables as unfavorable outcomes at discharge, ICU, or mechanical ventilation requirement. A thorough neurological examination in young patients with new-onset psychiatric symptoms could help emergency physicians, neurologists, and psychiatrists suspect anti-NMDAR encephalitis earlier. Awareness of NI as a potential side effect during suspected or confirmed anti-NMDAR encephalitis is encouraged.