Clinical features of anti-γ-aminobutyric acid B receptor encephalitis

Objective To analyze the clinical characteristics, imaging manifestations and prognoses of anti-GABAB receptor antibodies encephalitis. Methods The clinical manifestations, laboratory findings and radiological data of 13 patients with anti-GABAB receptor encephalitis, admitted to our hospital from September 2015 to March 2017, were retrospectively analyzed. Modified Rankin scale (mRs) was performed to evaluate the prognoses (good prognosis: mRs scores ≤2; poor prognosis mRs scores≥3). Results These 13 patients had an average age of 58 years (ranged 49-76 years) with a male to female ratio of 12:1. The major clinical features, including epileptic seizure, were found in 12 patients, psychiatric symptoms in 11 patients, cognitive disorder in 7 patients, and disturbance of consciousness in 4 patients. Brain MR imaging showed abnormal signal in 5 patients: 4 were located in the hippocampus and amygdaloid, and one in the pons and left temporal lobe. Five patients showed abnormalities in PET-CT, including 4 with temporal hypermetabolism and 1 with cortical hypometabolism. Chest CT showed lung occupying lesions in 4 patients, of which 2 patients were diagnosed as having small cell lung cancer (SCLC) by pathological examination. Ten patients received immunomodulatory therapy, and three were with supportive care. After the average of 8 months of follow-up, 7 patients had good prognosis, 5 patients had poor prognosis and one patient lost of follow up. Conclusions Anti-GABAB receptor encephalitis frequently occurs in elderly male subjects and the main characteristic includes prominent refractory epilepsy and shows neurological improvement on immunotherapy. It can accompany by SCLC and have a relatively poor prognosis. Key words: Gamma-aminobutyric acid; Encephalitis; Epilepsy; Small cell lung cancer