from using magnetization transfer ratio imaging. My name is Stephen Wilden. I'm a third year medical student at the University of Arizona College of Medicine in Tucson, Arizona. I also worked with Dr. Richard Dorch and Dr. Rory Murphy from the departments of translational neuroscience and neurosurgery at Barrow Neurological Institute in Phoenix, Arizona. So an introduction to carpal tunnel syndrome. It is compression of the median nerve, which presents as numbness, tingling, burning, and or pain, primarily in the thumb, index, middle, and ring fingers. Carpal tunnel affects about one in 20 adults worldwide and is commonly treated via surgical release. The current options for post-surgical monitoring are limited, but they include physical exam, electromyography, and other nerve conduction studies. However, due to the slow regeneration rate of peripheral nerves and some imperfections in the physical exam or nerve conduction studies, surgeons usually rely on a watch and wait approach, which can delay decision-making and increase the likelihood of permanent deficits. Therefore, a biomarker, which monitors regeneration throughout the recovery process, would improve decision-making and treatment outcomes. So magnetization transfer ratio is an MRI modality, which assays myelin content changes and is usually used to report degeneration and disability in inherited neuropathies. However, our goal is to evaluate the feasibility of using MTR in carpal tunnel syndrome, with the long-term goal of applying this method to more severe nerve transactions and repairs. For methods, we used a 3T-MTR, we used a 3T MRI scanner on eight patients between the ages of 40 and 73 years old, five females and three males, all of which had unilateral carpal tunnel syndrome and carpal tunnel release procedure. We excluded any patients with a history of other neuropathies or wrist trauma. And these MRI scans were performed in the wrist one to five months after surgery. The data was collected in both the affected and unaffected arms so that each subject was able to serve as its own control. The median and ulnar nerves were manually identified on proton density scans and then co-registered into the MTR space. And the MTR values were estimated across all slices and compared via Wilcoxon rank sum tests. Here we have some example images. On the left, we can see a proton density scan of an affected wrist. Here's the same proton density scan with the manually labeled ulnar and median nerves, and then its corresponding magnetization transfer ratio map. When we analyzed our data, we found that the MTR values were significantly reduced in the affected median nerves with an MT ratio of 27 plus or minus 2% compared to the unaffected median nerve, which had an MT ratio of about 30 plus or minus 1%, as you can see here. The gray box is the affected median nerve with red being unaffected. Of note, the MTR of the ulnar nerves in both wrists were comparable to the unaffected median nerve. In conclusion, we found that MTR is sensitive enough to detect changes in myelin content after carpal tunnel release procedures. Therefore, MTR may be a viable biomarker of degeneration and regeneration of peripheral nerves. Ongoing work is being focused on larger longitudinal studies to determine if MTR is responsive to regeneration and predictive of outcomes, as well as developing multi-contrast MRI methods to improve the specificity of MTR scans. I would like to acknowledge the Dortch Lab as well as Barrow Neurosurgery and Neuroimaging, and the funding for this research is listed below. Thank you very much again for watching my presentation on the assessment of carpal tunnel syndrome using magnetization transfer ratio imaging.

Stephen Wilden

magnetization transfer ratio

MTR imaging

carpal tunnel syndrome

nerve regeneration