To lower the threshold for suspicion of GABA B receptor antibody related encephalitis in patients with history of cancer and presenting with new onset seizures since this can be easily misdiagnosed or overlooked thus prolonging the initiation of immunotherapy. 

Patients with autoimmune encephalitis are often young, less frequently have malignancies, and they respond better to immunotherapy. Many of these patients have limbic encephalitis with amnesia, disorientation, seizures, and psychiatric symptoms. However, GABA B receptor encephalitis is better known to be paraneoplastic and is characterized by an epilepsy phase before an encephalitic phase with dysautonomia and multifocal cortical-subcortical MRI abnormalities. The functional prognosis is poor.

Case report and literature review: 74 year old female with a history of colon cancer (2011 s/p resection) and a 30 day history of seizures, ataxia and rapidly developing dementia. MRI brain showed DWI restriction in the R hippocampus without FLAIR hyper intensity or contrast enhancement. cEEG showed multiple discharges originating in the left mid-to-posterior temporal and parietal region, spreading to the left fronto-temporal region. CSF studies revealed elevated total tau, and positive 14-3-3 proteins but negative RT-QuIC. Serum GABA-B receptor antibodies were significantly elevated. Other autoimmune antibody panel such as anti-NMDA receptor antibody were negative. Patient started showing cognitive improvement with steroid therapy and has been seizure free with levetiracetam and divalproex. Rituximab infusion was started

GABA-B receptor antibodies causing encephalitis is relatively rare and it is very important to recognize as the symptoms and complications can be fatal when not treated in time. Immunotherapy is probably too weak if initiated after the onset of a substantial neuronal injury. Earlier diagnosis and treatment are necessary to improve the functional prognosis of paraneoplastic GABA- B receptor antiobody encephalitis