Musicogenic epilepsy: Expanding the spectrum of glutamic acid decarboxylase 65 neurological autoimmunity.

The objective of this study was to describe serological association of musicogenic epilepsy and to evaluate clinical features and outcomes of seropositive cases. Through retrospective chart review, musicogenic epilepsy patients were identified. Among 16 musicogenic epilepsy patients, nine underwent autoantibody evaluations and all had high-titer glutamic acid decarboxylase 65-immunoglobulin G (GAD65-IgG; >20 nmol·L-1 , serum, normal ≤ .02 nmol·L-1 , eight women). Median GAD65-IgG serum titer was 294 nmol·L-1 (20.3-3005 nmol·L-1 ), and median cerebrospinal fluid titer (n = 4) was 14.7 nmol·L-1 . All patients had temporal lobe epilepsy, and bitemporal epileptiform abnormalities were common. Right temporal lobe seizures were most frequently captured when seizures were induced by music on electroencephalogram (3/4; 75%). Intravenous (IV) methylprednisolone and/or IV Ig (IVIG) was utilized in four patients, with one having greater than 50% reduction. Rituximab (n = 2) and mycophenolate (n = 1) were ineffective. Two patients underwent right temporal lobe resections but continued to have seizures. Vagus nerve stimulation was effective at reducing seizures in one patient by 50%, and an additional patient was seizure-free by avoiding provoking music. Right temporal lobe epilepsy was more common among patients with musicogenic epilepsy when compared to nonmusicogenic GAD65 epilepsies (n = 71, 89% vs. 47%, p = .03). GAD65-IgG should be tested in patients with musicogenic epilepsy, given implications for management and screening for comorbid autoimmune conditions.

Neurological Syndromes Associated with Anti-GAD Antibodies.

Glutamic acid decarboxylase (GAD) is an intracellular enzyme whose physiologic function is the decarboxylation of glutamate to gamma-aminobutyric acid (GABA), the main inhibitory neurotransmitter within the central nervous system. GAD antibodies (Ab) have been associated with multiple neurological syndromes, including stiff-person syndrome, cerebellar ataxia, and limbic encephalitis, which are all considered to result from reduced GABAergic transmission. The pathogenic role of GAD Ab is still debated, and some evidence suggests that GAD autoimmunity might primarily be cell-mediated. Diagnosis relies on the detection of high titers of GAD Ab in serum and/or in the detection of GAD Ab in the cerebrospinal fluid. Due to the relative rarity of these syndromes, treatment schemes and predictors of response are poorly defined, highlighting the unmet need for multicentric prospective trials in this population. Here, we reviewed the main clinical characteristics of neurological syndromes associated with GAD Ab, focusing on pathophysiologic mechanisms.

Quantitative brain imaging analysis of neurological syndromes associated with anti-GAD antibodies.

Neurological disorders associated with anti-glutamic acid decarboxylase (GAD) autoimmunity are rare and include a variety of neurological syndromes: stiff-person syndrome, cerebellar ataxia or limbic encephalitis. The diagnosis remains challenging due to the variety of symptoms and normal brain imaging. The morphological MRI of 26 patients (T1-weighted and Fluid-attenuated inversion recovery (FLAIR)-weighted images) was analyzed at the initial stage of diagnosis, matched by age and sex to 26 healthy subjects. We performed a vertex-wise analysis using a generalized linear model, adjusting by age, to compare the brain cortical thickness of both populations. In addition, we used a voxel-based morphometry of cerebellum thickness obtained by CEREbellum Segmentation (CERES), as well as the hippocampus volumetry comparison using HIPpocampus subfield Segmentation (HIPS). Finally, we extracted 62 radiomics features using LifeX to assess the classification performance using a random forest model to identify an anti-GAD related MRI. The results suggest a peculiar profile of atrophy in patients with anti-GAD, with a significant atrophy in the temporal and frontal lobes (adjusted p-value < 0.05), and a focal cerebellar atrophy of the V-lobule, independently of the anti-GAD phenotype. Finally, the MRIs from anti-GAD patients were correctly classified when compared to the control group, with an area under the curve (AUC) of 0.98. This study suggests a particular pattern of cortical atrophy throughout all anti-GAD phenotypes. These results reinforce the notion that the different neurological anti-GAD phenotypes should be considered as a continuum due to their similar cortical thickness profiles.