Microstructural white matter brain abnormalities in patients with idiopathic fecal incontinence

Abnormal central nervous system processing of visceral sensation may be a part of the pathogenesis behind idiopathic fecal incontinence (IFI). Our aim was to characterize brain differences in patients with IFI and healthy controls by means of structural magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI).

In 21 female patients with IFI and 15 female healthy controls, whole-brain structural differences in gray matter volume (GMV), cortical thickness, and white matter tracts fractional anisotropy (FA) were quantified. For this purpose, we used voxel-based morphometry, surface based morphometry and tract-based spatial statistic, respectively. Furthermore, associations between structural brain characteristics and latencies of rectal sensory evoked electroencephalography potentials were determined.

Compared to healthy controls, IFI patients had significantly reduced FA values, reflecting reduced white matter tract integrity, in the left hemisphere superior longitudinal fasciculus (SLF), posterior thalamic radiation, and middle frontal gyrus (MFG), all P<.05. No differences were observed in GMV or in cortical thickness. The reduced FA values in the SLF and MFG were correlated with prolonged latencies of cortical potentials evoked by rectal stimuli (all P<.05).

This explorative study suggests that IFI patients have no macrostructural brain changes, but exhibit microstructural changes in white matter tracts relevant for sensory processing. The clinical relevance of this finding is supported by its correlations with prolonged latencies of cortical potentials evoked by rectal stimulation. This supports the theories of central nervous system changes as part of the pathogenesis in IFI patients.