Altered white matter architecture in patients with isolated congenital anosmia.

Isolated Congenital Anosmia (ICA) is a rare condition characterized by the absence of the sense of smell due to the underdevelopment of the olfactory bulbs and a corresponding lifelong lack of olfactory input to the brain. Previous studies have reported that ICA patients exhibit structural and volumetric alterations in both gray and white matter regions as well as slightly elevated fractional anisotropy (FA) in the orbitofrontal cortex. This study expanded on these findings by utilizing whole-brain diffusion tensor imaging (DTI) with a 3T MR scanner to investigate microstructural changes in the white matter of 8 ICA patients and 14 age- and gender-matched healthy controls (HCs). Tract-based spatial statistics revealed significantly lower FA values in the right superior corona radiata (SCR) of ICA patients compared to HCs (p = 0.001), indicating compromised white matter integrity in this region. Elevated mean diffusivity and radial diffusivity values in the right SCR (p = 0.009 and p = 0.002, respectively) suggest underlying demyelination. In the HC group, FA values in the SCR cluster were positively correlated with odor identification scores (rho = 0.59, p = 0.026), highlighting the functional relevance of SCR in processing olfactory information and semantic formation of odor perception. These findings underscore the critical role of early sensory input in shaping the architecture of white matter, and illustrate the impact of congenital olfactory deprivation on the structural integrity and functional organization of neural pathways.