MRI Characteristics of Autoimmune Encephalitis With Autoantibodies to GABAA Receptor: A Case Series

BACKGROUND AND OBJECTIVES: To characterize the clinical and neuroimaging phenotypes of patients with autoantibodies to γ-aminobutyric acid type A receptor (GABA(A)R). METHODS: Ten patients with autoantibodies against GABA(A)R from Huashan Hospital Autoimmune Encephalitis cohort were identified. We used MRI assessments and clinical examinations to summarize major clinical profile and visualize and quantify lesion distribution features. The relationship between clinical features, neuroimaging phenotypes, and topology of GABA(A)R expression were further investigated. RESULTS: The median age at onset of 10 patients (8 male patients and 2 female patients) with anti-GABA(A)R encephalitis was 41.5 years (range: 17–73 years). All patients had prominent seizures and multifocal spotted or confluent lesions involved in limbic, frontal, and temporal lobes on brain MRI. Bilateral but asymmetric lesions in cingulate gyri were observed in all patients. These involved lesions could change dynamically with immunotherapies and relapse. Distribution of patients' brain MRI lesions was positively correlated with gene expression level of β3 subunit–containing GABA(A)R (Spearman ρ = 0.864, p = 0.001), the main target of autoantibodies. According to topology of lesions, patients with anti-GABA(A)R encephalitis could be classified into 2 clinical-radiological types: confluent type with bilateral confluent lesions involved in almost all limbic, frontal, and temporal lobes and spotted type with multiple scattered small-to-medium patchy lesions. Patients with confluent type exhibited worse clinical presentations and outcomes when compared with those with spotted type (maximum modified Rankin scale [mRS]: 5 [5–5] vs 3.5 [3–4], respectively, p = 0.008; follow-up mRS: 4 [2–6] vs 0.5 [0–1], respectively, p = 0.016). DISCUSSION: Anti-GABA(A)R encephalitis has distinctive neuroimaging phenotype. Cingulate gyri were frequently involved in this disorder. The topology of lesions might be associated with the distribution of β3 subunit–containing GABA(A)R and reflected patients' disease severity and outcomes.