Cognitive Impairment in Autoimmune Encephalitis: Characterization and Predicting Long-term Outcomes

Autoimmune encephalitis (AE) is now emerging as an important cause of reversible cognitive impairment.

We aimed to study cognitive domains affected in various subtypes of AE, assess the changes in cognitive profile, and factors that predict residual cognitive impairment.

Cognitive assessment was conducted based on their age at presentation (≤12 years: Vineland Social Maturity Scale, 13-18 years: Montreal Cognitive Assessment and >18 years: Addenbrooke's Cognitive Examination-III). They were screened for psychiatric manifestations by Neuropsychiatric Inventory questionnaire. The assessment was repeated after 6 months.

Mean age was 21.8 (21.8 ± 17.0) years. Among 74 (M:F: 29:45) patients, 38 (51%) were less than 18 years of age, 22 (37%) adults and 9 (12%) patients belonged to late onset (more than 45 years). Cognitive impairment was seen in 100% of late onset, 85% adults and 58% children. At follow-up, Cognitive impairment was present in 27 out of 45 (60%) patients. Cognitive impairment was common in patients with late-onset AE and in patients with anti-Leucine-rich glioma inactivated-1 (LGI-1) positivity. Age more than 45 years, mutism, hallucinations, incontinence, altered consciousness, psychiatric manifestations, and modified Rankin Scale (mRS) scores more than three, abnormal EEG were shown to be significantly associated with poor cognitive scores. The cognitive domains affected were attention, fluency, memory as residual deficits. The pattern of cognitive recovery during follow-up showed significant improvement in all domains except for new learning, memory, and fluency.

Cognitive Impairment is common in autoimmune encephalitis with new learning, memory and fluency domains severely affected. Late-onset, abnormal EEG, high mRS scores and coexistent psychiatric disturbances predict poor cognitive outcomes.