Gamma-Aminobutyric Acid Type A Receptor Encephalitis Primarily Manifesting as Cognitive Dysfunction and Subclinical Epilepsy: A Case Report and Literature Review

Background: Anti-γ-aminobutyric acid type A receptor (anti-GABA A R) encephalitis is a neurological disorder that primarily manifests as cognitive dysfunction and seizures. Affected patients rarely present with subclinical epilepsy; thus, they are prone to misdiagnosis and underdiagnosis due to a lack of available tests during early disease stages. Case presentation: An 83-year-old male presented with a 20-day history of progressively worsening hypomnesis. On admission, cognitive dysfunction was indicated based on a Simple Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) scores of 8 and 4, respectively. Electroencephalography (EEG) showed paroxysmal spike-slow complex wave bursts in all regions, and cerebrospinal fluid was positive for anti-GABA A R β3 antibodies (titer 1:3.2). The patient was diagnosed with anti-GABA A acid A encephalitis and treated with methylprednisolone sodium succinate, gamma globulin, and mycophenolate mofetil capsules. After treatment, hypomnesis gradually improved, and EEG findings transitioned from paroxysmal spike-slow complex wave bursts in various regions to clusters of predominantly theta and delta waves. Thereafter, the patient was discharged from the hospital. After discharge, the patient continued taking oral methylprednisolone and mycophenolate mofetil capsules, but self-discontinued methylprednisolone after one month. At the five-month follow-up, the hypomnesis was significantly improved, and MMSE and MoCA scores were 18 and 14, respectively, revealing moderate cognitive impairment. Conclusions: : Anti-GABA A R encephalitis manifesting clinically as cognitive dysfunction and subclinical epilepsy is rare. Therefore, early, comprehensive, and meticulous ancillary examinations with timely and effective treatment planning are crucial for improving the duration of recovery and prognosis of the disease.