Abstracts

Rationale: The determination of neural antibodies gained an increasing importance in epilepsy diagnostics. Contrarily to pathogenic surface antibodies, the meaning of intracellular GAD65-antibodies remains unclear. The aim of this study was to uncover typical syndromic profiles in patients with GAD65-antibodies-related chronic temporal lobe epilepsy (TLE) and to assess outcome-data.     Methods: We selected patients who fulfilled the clinical criteria of potential subacute limbic encephalitis or chronic autoimmune TLE and determined neural antibodies using a broad panel of surface and intracellular antigens. We identified the GAD65-positive cases and characterized them clinically. All patients underwent video-EEG-monitoring, brain imaging and neuropsychological work-up.  After the establishment of drug-treatment, seizure-outcome, psychiatric and neurocognitive data were assessed yearly. Results: Out of 169 adult patients, 9 patients had positive GAD65-antibodies. Common characteristics of all patients were female gender, late epilepsy onset, mood disturbances, slight memory decline and electroclinically proven temporal lobe seizures. Structural mesio-temporal abnormalities were found in 3 patients. Five patients had endocrinological and 4 had psychiatric co-morbidities. Five patients had seizures induced by their favorite music, 4 others by strong emotional stimuli. Three of the five patients with exclusively music-triggered seizures were completely seizure-free by avoidance of the specific musical stimulus (follow-up 1-4 years after diagnosis, one patient without antiepileptic-drugs). The other 2 patients still had rare spontaneous seizures but also could avoid seizures triggered by music. The 4 patients with mainly emotionally triggered seizures had a 25-75 % seizure reduction at the last observation. Immunomodulatory treatment was established in only 2 patients without any success. The other patients renounced to immunotherapy, after they had been informed about the missing proof of efficacy in intracellular antibodies. While severity of psychiatric symptoms in predisposed patients was fluctuant, the neurocognitive capabilities remained stable.    Conclusions: Regarding our data, we postulate that there might be a clinical syndrome of autoimmune modulated chronic TLE with GAD65- antibodies with variable outcomes. Strikingly our complete series of patients with seizures induced by music has positive GAD-antibodies. There might be a link between intracellular neural antibodies, considered as markers of immunopathological processes of limbic structures and a predisposition in some patients with autoimmune-mediated TLE to develop music-induced seizures, since music processing strongly implicates the limbic system. In our series, emotional stimuli also played an important role in seizure induction that underlines the importance of limbic involvement in this kind of epilepsy.     Funding: No funding was received in support of this abstract.