Glutamate Antagonists in Catatonia Due to Anti-NMDA Receptor Encephalitis

Background/Significance: Catatonia is common in anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis (Espinola-Nadurille, 2019). The glutamate NMDAR antagonists amantadine and memantine are effective in catatonia (Beach, 2017), but data on their use in anti-NMDAR encephalitis is limited. We describe three patients with catatonia due to anti-NMDAR encephalitis treated with NMDAR antagonists and propose a possible mechanism underlying differential outcomes.



Case 1: A 20-year-old woman presented with catatonic symptoms after successful treatment of anti-NMDAR encephalitis with immunotherapy and salpingo-oopherectomy for ovarian teratoma. Initial Bush-Francis Catatonia Rating Scale (BFCRS) score was 22. Lorazepam 2.5 mg three times daily was partially effective, but increased doses caused sedation. Memantine was titrated to 10 mg twice daily with complete resolution of catatonia over two weeks.



Case 2: A 26-year-old woman presented with catatonic with BFCRS score of 25, after successful immunotherapy for anti-NMDAR encephalitis. Lorazepam 2 mg four times daily was partially effective, but further increase caused respiratory depression. Memantine 10 mg daily resulted in further improvement. Lorazepam titration to 4 mg four times daily was then possible, with complete resolution of catatonia over two weeks.



Case 3: A 31-year-old woman with anti-NMDAR encephalitis presented with catatonic symptoms with BFCRS score of 22, after a hospital course significant for limited response to immunotherapy with persistently elevated serum anti-NMDAR antibody titers. Lorazepam 2 mg three times daily was partially effective, but further increase caused sedation. Both amantadine 100 mg twice daily and memantine 10 mg were trialed but were discontinued due to agitation. Mutism and negativism persisted, with a discharge BFCRS score of 12.



Discussion: Memantine was effective for catatonia and well tolerated in two patients with successfully treated anti-NMDAR encephalitis, but both amantadine and memantine caused agitation in a third patient with active disease. NMDARs are reversibly internalized in the presence of anti-NMDAR antibodies, leading to a compensatory increase in downstream glutamatergic tone. We hypothesize that NMDAR reemergence after successful treatment, in the context of excess extracellular glutamate, creates a state of excitotoxicity contributing to catatonic signs for which NMDAR blockade can be effective. In the third case, where NMDARs presumably remained internalized in the presence of persistent anti-NMDAR antibodies and a state of NMDAR hypofunction persisted, further NMDAR blockade caused clinical worsening.



Conclusion/Implications: NMDAR antagonists can be safe and effective in patients with residual catatonia following successful treatment of anti-NMDAR encephalitis but may be less useful during active disease. More work is needed to clarify best practices for patients with catatonia due to anti-NMDAR encephalitis.



References



Espinola-Nadurille M, Flores-Rivera J, Rivas-Alonso V, et al. Catatonia in patients with anti-NMDA receptor encephalitis. Psychiatry Clin Neurosci. 2019;73(9):574-580.



Beach SR, Gomez-Bernal F, Huffman JC, Fricchione GL. Alternative treatment strategies for catatonia: A systematic review. Gen Hosp Psychiatry. 2017;48(June):1-19.