Role of bilateral corticobulbar tracts in dysphagia after middle cerebral artery stroke

Abstract

Background and purpose: The corticobulbar tract is a potential neural pathway involved in swallowing. The frontal operculum, insular cortex, corona radiata and internal capsule, which are frequently involved in middle cerebral artery (MCA) strokes, are locations in which lesions cause dysphagia. However, it is unclear whether the locations are linked to the corticobulbar tract or whether corticobulbar tract integrity is associated with dysphagia severity. This study aimed to assess the association between corticobulbar tract integrity and dysphagia severity after MCA stroke. Methods: Thirty dysphagic patients after MCA stroke and 27 healthy controls were examined. Diffusion tensor imaging (DTI)-derived parameters of the corticobulbar tract were compared between patient and control groups. Next, patients were divided into mild and moderate-to-severe dysphagia groups, and DTI-derived parameters of the corticobulbar tract were compared between the subgroups. Logistic regression analysis was used to determine the association between corticobulbar tract integrity and dysphagia severity. Results: The tract volume (TV) of the affected corticobulbar tract was lower in dysphagic patients than in healthy controls (P < 0.001). According to dysphagia severity, TV of the unaffected corticobulbar tract was higher in the mild dysphagia group than in the moderate-to-severe dysphagia group (P = 0.012). TV of the unaffected corticobulbar tract was independently associated with dysphagia severity according to the logistic regression model (adjusted odds ratio 0.817, 95% confidence interval 0.683-0.976). Conclusions: The corticobulbar tract was affected after MCA stroke and may be associated with dysphagia. A higher corticobulbar TV in the unaffected hemisphere was indicative of better swallowing function in dysphagic patients after MCA stroke.

Neural correlates in the development of and recovery from dysphagia after supratentorial stroke: A prospective tractography study

“…A two-region of interest (ROI) approach was used to reconstruct the corticobulbar tract. The seed ROI was set on the frontal operculum and the caudal part of the premotor and primary motor cortex ( Hazzaa et al, 2019 , Im et al, 2020 , Jang et al, 2021 ). The way ROI was placed at the mid-pontine level, where the corticobulbar/corticospinal tract is represented by the blue fibers of the anterior pons on the color fractional anisotropy (FA) map.…”

“…The FA and tract volume (TV) of the corticobulbar tract in each hemisphere were determined ( Jang and Seo, 2015 , Jenabi et al, 2015 ). FA values were measured on the seed ROIs from the frontal operculum ( Im et al, 2020 ). The TV values of the corticobulbar tract were calculated by multiplying the voxel volume by the number of traced voxels during fiber tracking performed based on a robust minimum intensity threshold of 1 ( Im et al, 2020 ).…”

“…FA values were measured on the seed ROIs from the frontal operculum ( Im et al, 2020 ). The TV values of the corticobulbar tract were calculated by multiplying the voxel volume by the number of traced voxels during fiber tracking performed based on a robust minimum intensity threshold of 1 ( Im et al, 2020 ). The DTI of all participants was analyzed by an expert with 5 years of experience in tractography analysis, who was blinded to swallowing assessments.…”

“…However, strokes show highly variable lesion locations, lesion extents, and degrees of neural tract injury. Recently, the importance of analyzing neural pathways and their integrity related to swallowing has been highlighted ( Im et al, 2020 , Jang et al, 2020 , Jang et al, 2021 ).…”

“…Diffusion tensor imaging (DTI) can provide an assessment of the whole structural integrity of the corticobulbar tract ( Jang and Seo, 2015 ). A recent study has shown that the tract integrity of the unaffected corticobulbar tract may indicate the severity of poststroke dysphagia ( Im et al, 2020 ). However, the retrospective study primarily compared tractography findings between patients with dysphagic stroke and age-matched healthy subjects, without direct comparison with nondysphagic stroke patients.…”