Abstracts

Rationale: Autoimmune encephalitis is a neurological disorder caused by autoantibodies that target specific brain structures. The disease frequently manifests with psychiatric symptoms, memory problems, and seizures. The diagnosis can be challenging when psychiatric manifestations and memory deficits are mild or absent. To increase the awareness of atypical presentations, we report a case of Glutamic Acid Decarboxylase 65 (GAD 65) autoimmune encephalitis which manifested as primarily intractable epilepsy and stiff person syndrome.      Methods: A case report of a patient with GAD 65 encephalitis. Results: A 19-year-old female with no significant past medical history presented to our Center with a two-year history of persistent seizures despite trials of multiple antiepileptic medications. She had no complaints of memory loss or confusion. Mild behavioral changes of agitation and apathy were ascribed to social stressors and not given prominent consideration at the time of initial evaluation.Upon arrival at our Center, she was experiencing greater than 10 seizures per day. The seizures had clinical characteristics of a sensation of déjà vu, automatisms and language difficulty. Additionally, she experienced intermittent whole body tensing and muscle spasms. The latter symptoms were likely manifestations of stiff person syndrome. Continuous video EEG monitoring demonstrated frequent bilateral temporal lobe seizures. Although initial brain MRI at outside hospital was non-lesional, repeat MRI at our Center revealed increased T2/FLAIR signal in hippocampus and amygdala bilaterally. CSF studies demonstrated elevated protein and oligoclonal bands but no pleocytosis. CSF autoimmune panel was positive for GAD65 autoantibody. The patient was started on treatment with a 5-day course of IV methylprednisolone which led to significantly improved seizure control and resolution of agitation and apathy as well.The patient’s disease course was marked by intermittent breakthrough seizures and limb spasms for which she required hospitalizations for intravenous immunoglobulin infusion and a course of plasma exchange therapy. She responded appropriately to the immunomodulatory therapies. Follow-up MRI study revealed normal hippocampi and only residual T2/FLAIR hyperintensity signal in right amygdala. Search for the source of the GAD 65 autoantibody with extensive imaging including PET-CT whole body scan, ultrasound and MRI of pelvis was unrevealing. Conclusions: The case emphasizes the importance of early recognition of autoimmune encephalitis in patients with new onset of seizures even in the setting of only mild behavioral changes. The case also demonstrates that even intractable seizures in this disorder can be quite responsive to immunoregulatory therapy. Funding: none