Late-Onset Anti-GABA(B) Receptor Encephalitis: Clinical Characteristics and Outcomes Differing From Early-Onset Patients

BACKGROUND AND OBJECTIVES: Existing evidence indicates anti-GABA(B) receptor encephalitis (GABA(B)R-E) seems to occur more commonly later in life, yet the age-associated differences in clinical features and outcomes are not well determined. This study aims to explore the demographic, clinical characteristics, and prognostic differences between late-onset and early-onset GABA(B)R-E and identify predictors of favorable long-term outcomes. METHODS: This is an observational retrospective study conducted in 19 centers from China. Data from 62 patients with GABA(B)R-E were compared between late-onset (aged 50 years or older) and early-onset (younger than 50 years) groups and between groups with favorable outcomes (modified Rankin scale (mRS) ≤ 2) and poor outcomes (mRS >2). Logistic regression analyses were applied to identify factors affecting long-term outcomes. RESULTS: Forty-one (66.1%) patients experienced late-onset GABA(B)R-E. A greater proportion of males, a higher mRS score at onset, higher frequencies of ICU admission and tumors, and a higher risk of death were demonstrated in the late-onset group than in the early-onset group. Compared with poor outcomes, patients with favorable outcomes had a younger onset age, a lower mRS score at onset, lower frequencies of ICU admission and tumors, and a greater proportion with immunotherapy maintenance for at least 6 months. On multivariate regression analysis, age at onset (OR, 0.849, 95% CI 0.739−0.974, p = 0.020) and the presence of underlying tumors (OR, 0.095, 95% CI 0.015−0.613, p = 0.013) were associated with poorer long-term outcomes, whereas immunotherapy maintenance for at least 6 months was associated with favorable outcomes (OR, 10.958, 95% CI 1.469−81.742, p = 0.020). DISCUSSION: These results demonstrate the importance of risk stratification of GABA(B)R-E according to age at onset. More attention should be paid to older patients especially with underlying tumors, and immunotherapy maintenance for at least 6 months is recommended to achieve a favorable outcome.