Abstracts

Rationale: Inflammatory and autoimmune mechanisms are now known to play an important role in epilepsy. Standard clinical imaging methodologies such as MRI provide only limited information about epilepsy-associated inflammation. Positron Emission Tomography (PET) using C11-PK11195, a marker of activated microglia, allows noninvasive visualization of neuroinflammation in vivo in humans. C11-PK11195 PET (PK PET) has been used to investigate neuroinflammation in neurological disorders including multiple sclerosis and Alzheimer s Disease, but has been performed in only a small number of patients with epilepsy.Methods: A young woman with intractable bi-hippocampal epilepsy, depression and severe memory impairment underwent PK11195 PET as part of an IRB-approved research protocol. PK PET images were analyzed using a reference tissue model implemented in PMOD to generate binding potential images, which were co-registered to MRI. Results: PK PET identified focal regions of inflammation in bilateral hippocampi, as well as in brainstem and thalamus (see Figure.) PK PET results in hippocampus corresponded to regions of increased hippocampal FLAIR signal seen on MRI. Following PK PET scanning, clinical evaluation revealed high titer anti-GAD65 antibodies in the patient's serum and CSF, with evidence of intrathecal antibody synthesis.Conclusions: This is the first report of PK PET applied to epilepsy associated with anti-GAD antibodies, a form of non-paraneoplastic limbic encephalitis. Visualization of inflammation using PK PET can aid diagnosis and assessment of this and other autoantibody mediated neuropsychiatric disorders, and may prove useful for monitoring response to immunomodulatory treatment.