Admission diagnoses of patients later diagnosed with autoimmune encephalitis

Background: Since the detection of autoantibodies against neuronal surface antigens, autoimmune encephalitis (AE) has been more frequently diagnosed, especially in patients with symptoms typical of limbic encephalitis, such as seizures, short-term memory deficits, or psychosis. However, the clinical spectrum of AE may be much wider, making correct clinical diagnosis difficult. Methods: We retrospectively analysed symptoms and admission diagnoses at first clinical presentation in 50 AE patients. We included patients with a clinical diagnosis of AE for whom a FDG-PET imaging was available. Final diagnoses were re-evaluated by a blinded investigator according to the most recent consensus suggestions published in 2016 for AE diagnostic criteria. We additionally describe two patients with Morvan syndrome who showed CASPR2 antibodies. Results: In 40 patients (80.0%), the clinical presentation at first admission was typical for AE. Ten patients (20.0%) initially suffered from atypical symptoms; among these patients, isolated headache and cerebellar dysfunction were most frequent (three patients each). However, an initial diagnosis of suspected encephalitis was only reached in 16 patients (32.0%), nine (18.0) of which were suspected to have infectious encephalitis, and seven (14.0%) patients were suspected to have AE. In 34 patients (68.0%), a diagnosis other than encephalitis was considered, (e.g., epilepsy, psychiatric diseases, transient ischemic attack, dementia, meningitis, and cerebellitis). Conclusions: These data show the broad spectrum of initial symptoms of AE; the correct initial diagnosis of AE is often missed or delayed. Hence, clinicians in neurological and psychiatric hospitals should consider AE in the differential diagnosis of cases with atypical clinical presentations.