gms | German Medical Science

Objective: The resection of brainstem cerebral cavernous malformations (CCM) harbors the risk of damage to the corticospinal tract (CST). Hence, the visualization of the CST potentially supports the planning in patients who undergo resection. However, diffusion tensor imaging fiber tracking (DTI FT) at brainstem level suffers from distortion due to field inhomogeneity and eddy currents because of diffusion gradients within the brainstem but also bony structures. The study aims to detect differences of the CST tractography in brainstem CCM patients by cranial distortion correction (CDC), which applies a deformation algorithm to DTI sequences by semi-elastic fusion.

Methods: We included 25 patients (mean age 46±18 years) who underwent resection of brainstem CCM. We performed anatomy-based CST tractography (mean minimal fractional anisotropy of 0.22±0.04) before and after CDC using perioperative DTI sequences and the same region of interest for both methods.

Results: The application of CDC led to a more precise CST tractography regarding its true anatomical localization in all cases. As measured by the distances to the basilary artery and the clivus, the CST was located significantly more ventral by a mean of 1.5±0.5 mm (6.1±2.6 mm vs. 4.6±2.1 mm, p<.001) and 1.7±0.5 mm (8.9±2.6 mm vs. 7.2±2.1 mm, p<.001). Aberrant fibers could be reduced by CDC in 44% of patients. We could not detect surgery-related motor deficits after resection of distorted fibers.

Conclusion: The present results show that CDC improves tractography of the CST in brainstem CCM patients regarding its true anatomical localization. Artifacts of DTI sequences due to bony structures can be reduced by CDC, being clinically relevant for tractography at brainstem level.