Exploring Psychological Factors and Brain Alterations in Functional Anorectal Pain Patients: Insights From Multimodal Magnetic Resonance Imaging Investigations

BACKGROUND: Functional anorectal pain (FAP) is classified as one of the disorders of gut-brain interaction (DGBI). It involves the impairments of anorectal afferents and disrupted gut-brain communication. However, neuroimaging studies focused on FAP are lacking. METHODS: A total of 25 FAP patients and 18 healthy controls (HC) underwent structural magnetic resonance imaging (MRI), diffusion tensor imaging (DTI), resting-state functional MRI (rs-fMRI) scans, and collection of demographic data, mental health assessment scales and pain assessment questionnaires. Voxel-based morphometry (VBM), tract-based spatial statistics (TBSS), regional homogeneity (ReHo), and amplitude of low-frequency fluctuations (ALFF) were utilized to analyze the imaging data. Correlation analyses were conducted to explore the relationships between the neuroimaging findings and clinical symptoms. KEY RESULTS: Functional anorectal pain (FAP) patients exhibited higher levels of anxiety, depression scores and lower sleep quality compared to HC. VBM analysis revealed increased gray matter volume (GMV) in the bilateral fusiform, right parahippocampal, bilateral inferior temporal gyrus (ITG), and decreased GMV in the right superior frontal gyrus (SFG), left middle frontal gyrus (MFG), bilateral inferior frontal gyrus (IFG), left Calcarine, bilateral middle occipital gyrus (MOG), left middle temporal gyrus (MTG) in FAP patients. TBSS analysis showed decreased fractional anisotropy (FA) in the superior longitudinal fasciculus (SLF), anterior thalamic radiation (ATR), and forceps minor in the FAP patients. Additionally, increased ALFF in the right cerebellum and increased ReHo in the right MFG were observed in the FAP patients. CONCLUSIONS AND INFERENCES: These findings showed a worse psychological condition and suggested neuroanatomical and neurofunctional alterations associated with pain processing, emotion regulation, and cognitive control in FAP patients.