A 46-year-old man presented with a 3-month history of transient diplopia and generalized weakness that worsened through the day. He was found to have seropositive MG and started on pyridostigmine; associated with malignant thymoma and underwent surgical resection next month 

Five months later, he developed new onset seizures and following his surgery, he developed agitation and confusion. Seizures were difficult to control. He underwent serial magnetic resonance imaging (MRI) of the brain, which showed multiple evolving subcortical/cortical T2 hyperintense lesions over the next 2 months, none of them with contrast enhancement. The lesions were bilateral, mainly affecting the left temporal lobe, but also affecting the right occipital, and bilateral frontal lobes. The electroencephalogram showed epileptogenicity from the left temporo-occipital region and right frontal area. Cerebrospinal fluid (CSF) did not reveal evidence of infection. Levetiracetam failed to control the seizures, and was later switched to brivaracetam and phenytoin. 

Due to concern of autoimmune encephalitis, patient was started on high-dose steroids followed by cyclophosphamide. Serum and CSF autoimmune encephalitis panel yielded a positive result for anti-GAD65. The addition of steroids and anti-epileptic drugs finally controlled the seizure