Association between corpus callosum microstructure and upper limb motor outcome in moderate-to-severe ischemic stroke patients at 3-6 months post-stroke.
Koo J, Lee A, et al. • Frontiers in neurology • 2026
CC-FA corrected of the genu showed a consistent nominal association with upper limb motor outcome beyond CST integrity in moderate-to-severe stroke, suggesting a complementary role of callosal microstructure alongside CST integrity, with an exploratory association also observed for the magnitude of motor improvement over time.
Key Findings
Results
CST FA laterality index, lesion volume, and corrected corpus callosum FA were all significantly associated with upper limb motor scores at 3 and 6 months post-stroke.
Study population: 38 patients with moderate-to-severe middle cerebral artery stroke who underwent diffusion tensor imaging during the early subacute phase
Upper limb motor function was assessed using the Shoulder Abduction and Finger Extension (SAFE) score
Simple linear regression analyses identified CST FALI, lesion volume, and CC-FA corrected as significant predictors
Associations were examined at both 3-month and 6-month post-stroke timepoints
Results
Corrected FA of the corpus callosum genu showed a consistent nominal incremental contribution to predicting upper limb motor outcome beyond CST FA laterality index, age, and lesion volume at both 3 and 6 months.
At 3 months: ΔR² = 0.061, adjusted R² = 0.600
At 6 months: ΔR² = 0.065, adjusted R² = 0.646
These findings were described as 'nominal incremental contribution' requiring confirmation in larger prospective cohorts
The body and splenium of the corpus callosum did not reach statistical significance after accounting for covariates
Results
In exploratory analysis, corrected genu FA was the only variable significantly associated with the magnitude of motor recovery (ΔSAFE) over the follow-up period.
ΔSAFE represents the change in SAFE score from baseline to 6 months
CC-FA corrected of the genu: R = 0.396, p = 0.041
CST FALI was not significantly associated with ΔSAFE (p = 0.097)
This was characterized as an 'exploratory analysis'
Results
The corpus callosum genu showed regionally specific associations with motor outcome, while the body and splenium did not.
Three subregions of the corpus callosum were examined: genu, body, and splenium
Only the genu reached nominal statistical significance in hierarchical regression models after accounting for CST FALI, age, and lesion volume
The body and splenium 'did not reach statistical significance after accounting for these covariates'
The genu was also the only CC subregion associated with motor recovery (ΔSAFE)
Methods
The study used a corrected corpus callosum FA measure (CC-FA corrected) to account for potential confounding from stroke-related white matter changes.
FA values of both the CST and CC were obtained from diffusion tensor imaging
A correction was applied to the CC FA values, denoted as CC-FA corrected
Imaging was performed during the early subacute phase post-stroke
The retrospective study analyzed 38 patients with moderate-to-severe middle cerebral artery stroke
Conclusions
Early combined assessment of corpus callosum and CST integrity during the subacute phase may provide preliminary information regarding post-stroke motor outcomes.
CST integrity is described as 'a well-established imaging correlate of post-stroke motor outcome' that 'does not fully explain interindividual variability, particularly in moderate-to-severe impairment'
Results were noted to require 'confirmation in larger prospective cohorts'
The findings are framed as providing 'preliminary information' rather than definitive clinical guidance
What This Means
This research suggests that the structure of a brain region called the corpus callosum — specifically its front portion, called the genu — may help predict how well stroke patients recover arm and hand movement, even after accounting for damage to the main motor pathway (the corticospinal tract). The study looked at 38 patients who had moderate-to-severe strokes affecting the middle cerebral artery and used a type of brain scan called diffusion tensor imaging to measure the microscopic structure of these white matter pathways in the early weeks after stroke. Arm and hand function were assessed using a simple clinical score measuring shoulder and finger movement at 3 and 6 months after stroke.
The findings showed that the integrity of the genu of the corpus callosum added meaningful information for predicting motor outcomes at both 3 and 6 months, beyond what could be predicted from the corticospinal tract damage, age, and stroke size alone. Notably, in an exploratory analysis, the genu was the only brain structure measure significantly linked to how much patients actually improved over time — the corticospinal tract measure did not reach significance for predicting recovery magnitude. The other parts of the corpus callosum (the body and splenium) did not show significant independent associations.
This research suggests that the corpus callosum, which connects the two halves of the brain, may play a role in motor recovery after stroke that is distinct from the direct motor pathway. If confirmed in larger studies, scanning both the corpus callosum and the corticospinal tract in the early weeks after stroke could give clinicians a more complete picture of a patient's likely recovery trajectory. The authors caution that these are preliminary findings from a small, retrospective study, and that larger prospective studies are needed before these measures could be considered for routine clinical use.
Koo J, Lee A, Lee E, Chang S, Kim Y. (2026). Association between corpus callosum microstructure and upper limb motor outcome in moderate-to-severe ischemic stroke patients at 3-6 months post-stroke.. Frontiers in neurology. https://doi.org/10.3389/fneur.2026.1852619