Abstract
Purpose
Glutamic acid decarboxylase (GAD65) has been implicated in a number of autoimmune-associated neurologic syndromes, including autoimmune epilepsy. This study categorizes the spectrum of MRI findings in patients with a clinical diagnosis of autoimmune epilepsy and elevated serum GAD65 autoantibodies.
Methods
An institutional database search identified patients with elevated serum GAD65 antibodies and a clinical diagnosis of autoimmune epilepsy who had undergone brain MRI. Imaging studies were reviewed by three board-certified neuroradiologists and one neuroradiology fellow. Studies were evaluated for cortical/subcortical and hippocampal signal abnormality, cerebellar and cerebral volume loss, mesial temporal sclerosis, and parenchymal/leptomeningeal enhancement. The electronic medical record was reviewed for relevant clinical information and laboratory markers.
Results
A study cohort of 19 patients was identified. The majority of patients were female (84%), with a mean age of onset of 27 years. Serum GAD65 titers ranged from 33 to 4415 nmol/L (normal < 0.02 nmol/L). The most common presentation was medically intractable, complex partial seizures with temporal lobe onset. Parenchymal atrophy was the most common imaging finding (47%), with a subset of patients demonstrating cortical/subcortical parenchymal T2 hyperintensity (37%) or abnormal hippocampal signal (26%). No patients demonstrated abnormal parenchymal/leptomeningeal enhancement.
Conclusion
The most common MRI finding in GAD65-associated autoimmune epilepsy is disproportionate parenchymal atrophy for age, often associated with abnormal cortical/subcortical T2 hyperintensities. Hippocampal abnormalities are seen in a minority of patients. This constellation of findings in a patient with medically intractable epilepsy should raise the possibility of GAD65 autoimmunity.
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Abbreviations
- GAD65:
-
Glutamic acid decarboxylase
- GABA:
-
Gamma-aminobutyric acid
- GAD65 Ab:
-
Serum anti-GAD65 antibodies
- SMS:
-
Stiff-man syndrome
- MTS:
-
Mesial temporal sclerosis
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The authors acknowledge the assistance of Sonia Watson, PhD, and Andrea Moran in preparation and formatting of the manuscript.
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No funding was received for this study.
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SJP has consulted for Alexion Pharmaceuticals, MedImmune and Chugai Pharma USA, but received no personal fees or personal compensation for consultations. SJP has received research support from Alexion Pharmaceuticals, MedImmune and Grifols, with all compensation paid directly to the Mayo Clinic.
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All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
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Fredriksen, J.R., Carr, C.M., Koeller, K.K. et al. MRI findings in glutamic acid decarboxylase associated autoimmune epilepsy. Neuroradiology 60, 239–245 (2018). https://doi.org/10.1007/s00234-018-1976-6
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DOI: https://doi.org/10.1007/s00234-018-1976-6