Association of increased cortical thickness and cognitive impairment in patients with Kallmann syndrome

To characterize whole-brain cortical thickness alteration in Kallmann syndrome (KS), assess its correlation with cognitive impairment, and explore the genetic association and extrapolated transcriptional underpinning.

We prospectively recruited 100 patients with KS and 100 age- and sex-matched healthy controls. All participants underwent high-resolution structural MRI and a comprehensive neuropsychological assessment targeting global cognition (Montreal Cognitive Assessment, MoCA), executive function and inhibitory control (Stroop Color and Word Test, SCWT), cognitive flexibility (Trail Making Test, TMT), working memory (Digit Span Test, DST), and visuospatial memory (Visual Reproduction task, VR). Cortical thickness and subcortical volumes were quantified using FreeSurfer. In the KS cohort, we examined brain-cognition correlations, performed exploratory genetic association analysis using whole-exome sequencing, and conducted extrapolated neuroimaging-transcription analysis using the Allen Human Brain Atlas (http://human.brain-map.org/) to identify underlying biological pathways.

Compared to the healthy controls, patients with KS exhibited significant cognitive deficits, with 36% MoCA scoring below the clinical cutoff for cognitive impairment. Domain-specific analysis revealed impairments in SCWT-C, DST-Backward, TMT-B, and VR (all P-value < .05). Structurally, patients showed bilateral increased cortical thickness predominantly in the fronto-limbic circuit (orbitofrontal and subgenual cingulate cortices) and default mode network (voxel P-value < .001, cluster random field theory corrected P-value < .05), alongside bilateral hippocampal enlargement (P-FDR = .048). Crucially, the cortical thickness in these fronto-limbic regions was negatively correlated with SCWT-C and DST. Exploratory genetic analysis linked variants in genes such as OTUD4 and FGFR1 to cognitive variability (TMT-A and VR). Furthermore, the spatial pattern of cortical thickening was significantly associated with extrapolated gene expression profiles enriched for neurodevelopment, neuronal migration, and synaptic function.

This study identified cortical thickening involved in fronto-limbic and default mode network as key neuroanatomical signatures of the patients with KS, which was associated with cognitive impairment. Specific genetic variants may further modulate the structural alterations and cognitive functioning in patients with KS.