Introduction: Some brain tumors cause compression of the optic chiasm and lead to visual failure. These tumors account for up to 10% of all intracranial tumors. No previous study has investigated the downstream changes in the visual pathway from optic chiasm compression. The MRI technique of diffusion tensor imaging (DTI) tractography allows in-vivo, non-invasive investigation of the white matter tracts in the human brain. This study uses DTI tractography biomarkers to investigate changes in the optic radiation (OR) of patients with tumors causing optic chiasm compression.
Methods: Patients recruited to the study were divided into groups based on visual function forming a normal vision group (n=10) and an abnormal vision group (n=7). Patients from both groups underwent a single additional MRI at least one year post surgery. DTI tractography of bilateral ORs for each patient was performed and OR tractography images were analysed for anatomical and DTI parameters.
Results: The OR DTI tractography data from this study correlated well with previously published dissection and DTI tractography studies. Significant differences in the OR DTI tractography were observed in a number of anatomical measurements and DTI biomarkers between patients with normal and abnormal vision. Patients with abnormal vision had decreased area at the midpoint of the OR (p=0.001), decreased OR volume (p=0.003), decreased fractional anisotropy (p=0.01), increased radial diffusivity (p=0.02) and increased apparent diffusion coefficient (p=0.04) compared to patients with normal vision.
Conclusions: Using DTI tractography biomarkers, this study demonstrates decreased OR integrity and OR atrophy in patients with persistent visual deficit following surgery for tumors causing optic chiasm compression and is the first study to demonstrate downstream changes in the visual pathway in these patients. Further studies utilizing DTI biomarkers may lead to improved visual outcomes in patients undergoing surgery for tumors causing optic chiasm compression.
Patient Care: This research will improve patient care by allowing clinicians to provide their patients with better information pre-operatively regarding the chances of visual recovery following surgery for optic chiasm compression. This research will also improve the timing of surgical intervention to optimize visual outcomes in patients with tumors causing optic chiasm compression.
Learning Objectives: By the conclusion of this session, participants should be able to: 1) Understand the visual consequences of tumors causing optic chiasm compression, 2) Describe the use of DTI tractography in the visual pathway, 3) Identify the utility of DTI tractography in optic chiasm compression, 4) Discuss the need for further studies to improve visual outcomes in optic chiasm compression