Abstract
INTRODUCTION: In NMDA-R encephalitis, which is typically accompanied by psychotic symptoms, conventional magnetic resonance imaging (MRI) is often normal, despite widespread alterations in functional connectivity. This is the first functional connectivity study in psychiatric patients with suspected autoimmune psychosis (AP) spectrum syndromes. METHODS: Twenty-eight patients with suspected AP spectrum syndromes who were selected according to the concept of autoimmune psychiatric syndromes (APS) and 28 matched healthy controls (HCs) were examined with ultrafast functional MRI using magnetic resonance encephalography (MREG). Patients were positive for either well-characterized or novel central nervous system antibodies or well-characterized systemic antibodies with autoimmune brain involvement. MREG data were processed using "Analysis of Functional NeuroImages" (AFNI) with the "Functional And Tractographic Connectivity Analysis AFNI toolbox" to analyze connectivity across 170 regions, yielding an analysis of 5995 evaluable connectivities. RESULTS: After correction for multiple testing, functional connectivity between the left middle cingulate/paracingulate gyri and the right insula (p(adj) = 0.025) was significantly reduced in the patient group compared to HCs. Exploratory analyses revealed widespread global functional connectivity alterations in 226 of all connections (corresponding to 3.8 %). Notably, of these altered connections, 99 % showed reduced connectivity, while 1 % showed hyperconnectivity. The medial pulvinar of the left thalamus emerged as the most disconnected hub with altered connectivity to 33 other regions. Overall, 46 % of all analyzed regions exhibited at least one altered functional connectivity, with 19 % of hubs located in the cerebellum, 11 % in the frontal brain, and 9 % in the thalami. After correction for multiple comparisons, increased connectivity between the left insula and the left superior temporal gyrus correlated with the Beck Depression Inventory scores (p(adj) = 0.043). DISCUSSION: Patients with suspected AP spectrum syndromes exhibit altered insular functional connectivity associated with the severity of depressive symptoms. Broader changes identified via hypothesis-generating analyses highlighted major hubs in the cerebellum, frontal brain, and thalamus. These findings suggest that functional MRI may serve as an additional tool for detecting patients with AP/APS. Future studies in more homogeneous autoimmune-mediated patient groups may help delineate specific connectivity signatures in functional networks.