BACKGROUND - Late-life depression is associated with white matter hyperintense lesions (WMLs) occurring in specific fiber tracts. In this study, we sought to determine if greater WML severity in the cingulum bundle or uncinate fasciculus was associated with poor short-term antidepressant response.
METHODS - Eleven depressed elders completed a baseline cranial 3T MRI and received antidepressant treatment following a medication algorithm. MRIs were analyzed to measure the fraction of each fiber tract׳s volume occupied by WMLs. Statistical analyses examined the effect of dichotomized fiber tract WML severity on three- and six-month depression severity after controlling for age and baseline depression severity.
RESULTS - Greater WML severity in the left hemispheric cingulum bundle adjacent to the hippocampus was associated with greater post-treatment depression severity at three- (F1,7=6.42, p=0.0390) and six-month assessments (F1,5=9.62, p=0.0268). Other fiber tract WML measures were not significantly associated with outcomes.
LIMITATIONS - The study had a small sample size and analyses were limited to only a priori fiber tracts.
CONCLUSIONS - This pilot study supports the hypothesis that focal damage to the cingulum bundle may contribute to poor short-term antidepressant response. These findings warrant further investigation with a larger, more definitive study.
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