OBJECTIVE: Carpal tunnel syndrome (CTS) is a common median nerve entrapment 
neuropathy characterized by pain, paresthesias, diminished peripheral nerve 
conduction velocity (NCV) and maladaptive functional brain neuroplasticity. We 
evaluated structural reorganization in brain gray (GM) and white (WM) matter and 
whether such plasticity is linked to altered median nerve function in CTS.
METHODS: We performed NCV testing, T1-weighted structural MRI, and diffusion 
tensor imaging (DTI) in 28 CTS and 28 age-matched healthy controls (HC). 
Voxel-based morphometry (VBM) contrasted regional GM volume for CTS versus HC. 
Significant clusters were correlated with clinical metrics and served as seeds 
to define associated WM tracts using DTI data and probabilistic tractography. 
Within these WM tracts, fractional anisotropy (FA), axial (AD) and radial (RD) 
diffusivity were evaluated for group differences and correlations with clinical 
metrics.
RESULTS: For CTS subjects, GM volume was significantly reduced in contralesional 
S1 (hand-area), pulvinar and frontal pole. GM volume in contralesional S1 
correlated with median NCV. NCV was also correlated with RD and was negatively 
correlated with FA within U-fiber cortico-cortical association tracts identified 
from the contralesional S1 VBM seed.
CONCLUSIONS: Our study identified clear morphometric changes in the CTS brain. 
This central morphometric change is likely secondary to peripheral nerve 
pathology and altered somatosensory afference. Enhanced axonal coherence and 
myelination within cortico-cortical tracts connecting primary somatosensory and 
motor areas may accompany peripheral nerve deafferentation. As structural 
plasticity was correlated with NCV and not symptomatology, the former may be a 
better determinant of appropriate clinical intervention for CTS, including 
surgery.