(412) Limbic Encephalitis Presenting with Faciobrachial Dystonic Seizures After History of Successfully Treated Thymoma Type B-3 with Excellent Neurocognitive Outcome with Early Immunotherapy

Rationale: Fasciobrachial dystonic seizures (FBDS) present with unilateral, intermittent dystonic posturing of the upper limb and face, often preceding a course of limbic encephalitis and are associated with Anti-LGI1 antibodies. We present a case of limbic encephalitis in a patient with a remote history of resected thymoma type B-3 who presented with convulsive seizures and FBDS raising clinical suspicion for limbic encephalitis. The early clinical diagnosis and timely treatment with immunotherapy resulted in excellent outcomes with remarkable recovery.

Methods: A 44-year-old male with a remote history of confirmed resected thymoma type B-3 presented with generalized convulsive tonic-clonic status epilepticus. EEG demonstrated a right temporal focus with secondary generalization. CT head and extensive infectious, metabolic, and toxic workup were unrevealing. The patient was discharged on levetiracetam and phenytoin with unclear etiology of seizures. A month later, he was admitted to the epilepsy monitoring unit with memory loss, cognitive changes, and jerking episodes of the left arm and face occurring up to sixty times daily. The patient noted to have multiple independent bi-temporal foci of seizures without any EEG correlate to the dystonic movements. MRI brain revealed generalized volume loss and CSF analysis with glucose 75, protein 27, WBC 11.8. The clinical suspicion for FBDS raised concern for limbic encephalitis and swift treatment with high dose steroids followed by intravenous immunoglobulin was initiated.

Results: Whole-body PET scan demonstrated hypermetabolic activity in bilateral basal ganglia and extensive autoimmune and paraneoplastic workup was obtained. The patient had rapid improvement of seizures and dystonic episodes with immunotherapy. He was discharged on levetiracetam, topiramate, and clonazepam. The antibody panel later returned positive for both Anti-LGI1 antibody and Anti-GAD antibody establishing a diagnosis of FBDS in the setting of limbic encephalitis though no neoplasm was identified. He was treated with monthly IVIG for a year with successful down titration to topiramate monotherapy. A repeat whole-body PET scan at one year was normal and patient despite continued surveillance has remained tumor-free for seven years.

Conclusions: Autoimmune encephalitides present with a vastly complex constellation of neurological symptoms rendering a diagnostic and management challenge that can have lasting consequences including seizures and cognitive deficits if not recognized early. Though antibody markers allow confirmation of autoimmune encephalitis, early clinical suspicion is paramount for prompt treatment with immunotherapy which can improve outcomes. In our patient, clinical suspicion for limbic encephalitis with FBDS was rapidly treated with IVIG and he has remained seizure-free for seven years with no residual cognitive deficits on repeat neuropsychiatric testing.

Funding: Please list any funding that was received in support of this abstract.: No Funding