Isolated Dysarthria due to Immune-mediated Brainstem Encephalitis Associated with Anti-Glutamate Acid Decarboxylase 65 antibodies (P2.2-038)

Objective: We describe a unique case of severe isolated dysarthria as the presenting sign of GAD65-Ab associated brainstem encephalitis. Background: Antibodies directed against GAD65 (anti-GAD65-Abs) are seen in a variety of neurologic autoimmune syndromes including stiff-man syndrome, cerebellitis, brainstem encephalitis, autoimmune epilepsies, limbic encephalitis, and dysautonomia. While there are case reports of isolated dysarthria have been previously reported as the presenting symptom of neurologic conditions such as Creutzfeldt-Jakob disease, clinically-isolated syndrome, and HIV infection to our knowledge, it has not been previously described in association with anti-GAD65 antibodies. Design/Methods: This patient case was seen at a tertiary referral setting in Phoenix, Arizona. Results: Myriad laboratory studies including paraneoplastic antibody panel were unremarkable, but serum anti-GAD65-Ab was markedly elevated at 2680. Modest elevation of other autoimmune markers, ANA (strongly positive, 6.4) and antiphospholipid IgM antibodies (weakly positive, 21.9), was noted. Epstein-Barr virus profile was abnormal with elevated anti-VCA IgM and IgG and anti-EBNA all positive, consistent with recovery or reactivation (previously reported as negative). CSF studies were unremarkable, with no pleocytosis and no elevation in protein. Brain MRI with contrast and thin slices through the brainstem was normal. Brainstem auditory evoked potentials were unremarkable. Electromyography/nerve conduction study was normal with no electrodiagnostic evidence of facial, trigeminal, or hypogloassal neuropathies and no evidence of muscle hyperexcitability. She was treated initially with steroids with no benefit; immunotherapy was escalated to IVIg and plasma exchange with modest improvement/stabilization in symptoms. Conclusions: We present a novel case of anti-GAD65-Ab associated brainstem encephalitis with primary manifestation of severe dysarthria. We hypothesize an immune-mediated mechanism of pathology, likely post-infectious in etiology noting evidence for recent Epstein-Barr virus infection. Disclosure: Dr. Dawit has nothing to disclose. Dr. Okazaki has nothing to disclose. Dr. Grill has nothing to disclose.