Abstract
BACKGROUND: The spectrum of autoimmune encephalitis (AIE) is evolving due to heterogeneity of clinical syndromes associated with autoantibodies. While majority of patients present within 3 months, little is known about chronic presentations of AIE. This study aims to characterise the neurobehavioural profile and assess the long-term outcomes of patients with chronic presentations of AIE. METHODS: Patients with serum or cerebrospinal fluid AIE antibody positivity were included in the study. We reviewed their clinical, cognitive, imaging and treatment characteristics as well as their long-term outcomes. Addenbrooke's Cognitive Examination-III and Clinical Dementia Rating score were used to evaluate global cognition and the severity of dementia, respectively. RESULTS: Of 306 patients diagnosed with dementia in a cognitive disorders' clinic, 28 had chronic presentations of AIE. The mean age of 28 patients was 55 years (range: 50-60), and mean duration of illness was 12 months (range: 3-84). Of the 28 patients, 9 (32%) were positive for leucine-rich glioma inactivated 1 antibody, 7 (25%) anti-thyroid peroxidase, 5 (18%) N-Methyl D-Aspartate receptor, 5 (18%) glutamic acid decarboxylase 65 and 2 (7%) had contactin-associated protein antibodies. Memory, language and behavioural disturbances with prominent neuropsychiatric symptoms were characteristic clinical manifestations. The course was chronic progressive, relapsing and rapidly progressive in 18 (64%), 8 (28%) and 2 (7%) patients, respectively. On immunomodulator therapy, the majority (21/28) improved, while 7/28 patients remained unchanged or experienced an exacerbation of symptoms. CONCLUSIONS: Chronic presentations of AIE are less known, and often misdiagnosed due to insidious progressive course and resemble degenerative dementias. A high index of suspicion in patients with chronic atypical cognitive syndromes and a low threshold for antibody testing will allow for prompt diagnosis, appropriate immunotherapy and improvement in clinical outcome.