Encephalitis with antibodies against the GABA B receptor: seizures as the most common presentation at admission.

OBJECTIVE: Autoimmune encephalitis associated with antibodies against gamma-aminobutyric-acid B receptor (GABAB R) has not been described in detail in Chinese patients.

METHODS: Patients with anti-GABAB R encephalitis treated between January 2013 and December 2015 were analyzed in terms of clinical characteristics, laboratory findings, tumor presence, autoantibody patterns, treatment response and outcomes.

RESULTS: Eleven patients were identified (male, N = 8; female, N = 3), with the median age of 51 years. All patients presented with seizures (N = 11; 100%), and they were given anti-epileptic drugs and first-line immunotherapy to address the disease. Seizures always accompanied by limbic manifestations (N = 10; 90.9%). Extralimbic manifestations were present in 4 patients (N = 4; 36.4%). MRI Brain abnormality with increased medio-temporal lobe T2/FLAIR signal were present in 2 patients (N = 2; 18.2%), and epileptiform epileptiform activity on electroencephalography were observed in 2 patients (N = 2; 18.2%). Small-cell lung cancer was histologically confirmed in 3 patients (N = 3; 27.3%). Seven patients showed good outcomes (mRS 1-2; N = 7; 63.6%), one patient showed poor neurological status with minimal changes (mRS 4; N = 1; 9.1%), and three patients died during follow-up (mRS = 6; N = 3; 27.3%). Outcomes were correlated with age-of-onset, and were worse among older patients (P = 0.0112).

CONCLUSION: Anti-GABAB R encephalitis is a potentially treatable disorder involving seizures as the most predominant presentation at admission. It should be considered as a possible diagnosis in middle-aged and older patients with refractory new-onset epilepsy.