A Retrospective Study of Patients with GABA(B)R Encephalitis: Therapy, Disease Activity and Prognostic Factors

PURPOSE: To explore the effects of immunotherapy and tumour treatment on patients with GABA(B)R encephalitis, evaluate the correlation between immune cell subsets and disease activity, and investigate effective prognostic factors. PATIENTS AND METHODS: Twenty patients with γ-aminobutyric acid B receptor (GABA(B)R) encephalitis were enrolled from December 2015 to April 2020. The clinical data, modified Rankin Scale (mRS) score, prognosis and percentage of serum lymphocytes were recorded. RESULTS: All patients received first-line immunotherapy. The median mRS scores were 4 and 3 before and after first-line immunotherapy (P<0.01). Seven patients received second-line immunotherapy and had median mRS scores of 3 and 2 before and after second-line immunotherapy (P=0.015). Small-cell lung cancer was detected in twelve patients. Among the patients who died because of tumours, patients who received tumour treatment lived longer than patients who did not receive tumour treatment (P=0.025). All four surviving patients who received tumour treatment had good outcomes (mRS≤2). The median serum CD19(+)B cell percentage in sixteen patients were 20.00% and 13.42% prior first-line immunotherapy and at the last follow-up (P<0.01). After a maximum follow-up of 54 months (median: 12; range: 3–54), eleven patients (55%) had a poor prognosis (mRS>2). Predictors of a poor prognosis were older age (P=0.031), delayed initial improvement after immunotherapy (>4 weeks) (P=0.038) and respiratory failure (P=0.038). CONCLUSION: Aggressive immunotherapy and tumour treatment contribute to improvements in neurological function and a better prognosis of patients with GABA(B)R encephalitis. The serum CD19(+)B cell percentage may be an indicator of disease activity. Older age, delayed initial improvement after immunotherapy, and respiratory failure may be associated with poor outcomes.