GAD65 Antibody Encephalitis Presenting as Treatment Resistant Temporal Lobe Epilepsy and Peripheral Neuropathy in a Pediatric Patient (1451)

Objective: To review the clinical presentation, EEG abnormalities, MRI features and treatment response in a child presenting with treatment resistant temporal lobe epilepsy (TLE) and peripheral neuropathy associated with high titers of anti-glutamic acid decarboxylase (anti-GAD65).

Background: Anti-GAD65 is associated with multiple neurological symptoms such as stiff-person syndrome, cerebellar ataxia and intractable epilepsy. However, TLE and peripheral demyelinating polyneuropathy in the absence of diabetes is rare. This combination has not been previously reported in a pediatric patient with anti-GAD65.

Design/Methods: Case report

Results: This is a previously healthy and developmentally normal 15-year-old male who presented with a two-month history of recurrent spells of tachycardia, chest tightness and confusion in the context of severe anorexia. These spells were captured on EEG and were consistent with left temporal lobe seizures. Brain MRI revealed T2 hyperintensity in the hippocampus bilaterally. CSF was remarkable for elevated CSF proteins (0.69g/L) and high levels of anti-GAD65 (>25000units/mL). Multiple anti-seizure medications provided only transient improvement. First and second line immunotherapy (IV methylprednisolone and IVIG) followed by rituximab, mycophenolate mofetil and cyclophosphamide failed to control his seizures. With disease progression, he developed symptoms of peripheral neuropathy. His nerve conduction study (NCS) indicated demyelinating sensorimotor polyneuropathy. During his treatment course, his MRI normalized but no change was observed in CSF anti-GAD65 levels. He was started on plasmapheresis for dual treatment of his seizures and neuropathy with minimal response.

Conclusions: This case broadens the phenotypic variability of GAD65 antibody in the pediatric population with demonstration of both central and peripheral nervous system involvement. Despite early initiation of immunotherapies, our patient did not respond favourably to conventional treatments. Questions still remain about early biomarkers of treatment response and underlying mechanisms of GAD autoimmunity.

Disclosure: Dr. Nabavi Nouri has nothing to disclose. Dr. Chiu has nothing to disclose. Dr. Schrader has nothing to disclose. Dr. Al-Jawadi has nothing to disclose.