Considerations of psychotic symptomatology in anti‐NMDA encephalitis: Similarity to cycloid psychosis

Most patients with anti‐NMDA receptor (NMDAR) encephalitis present with acute psychosis which is difficult to differentiate from psychotic episodes related to a primarily psychiatric disease. A precise description of the psychiatric phenotype of this disease would greatly facilitate the early diagnosis of these patients. We provide here a detailed description of three of these patients and the similarity of the clinical features with cycloid psychosis. All three patients met Perris and Brockington's criteria for cycloid psychosis in the initial phase of the autoimmune process, including among other an acute and polysymptomatic onset, polymorphous psychotic symptomatology, mood swings, and changes in psychomotricity. In addition, none of the patients had experienced an extended psychiatric prodromal phase. External stress factors preceded symptom onset in the three patients, who also showed common base personality traits and intolerance to a range of antipsychotic treatments. Complementary studies disclosed that the three patients had ovarian teratoma as well as abnormal EEG, and CSF antibodies against NMDAR. Patients with anti‐NMDAR encephalitis may present with clinical features that resemble cycloid psychosis. In addition, our patients did not have prodromal history of psychiatric symptoms and showed intolerance to antipsychotic medication, which all should raise concern for anti‐NMDAR encephalitis, prompting CSF antibody testing.