Diffusion MRI as A Biomarker for Monitoring Recovery After Surgical Repair of Traumatic Peripheral Nerve Injuries: A Longitudinal Case Series.

After transection, peripheral nerve regeneration requires repair surgery in a timely manner. Unfortunately, up to 40% of peripheral nerve repairs fail to achieve functional recovery. Patients with failed peripheral nerve repairs require additional surgical interventions, but current methods detecting clinical failure offer limited information, resulting in delayed management and suboptimal outcomes. Diffusion tensor imaging can serve as a biomarker of nerve regeneration; however, the complex spatial and temporal changes along the distal segment of the nerve remains challenging to interpret. To address this, we applied the Gompertz function to automatically characterize these changes and capture the nonlinear dynamics of recovery following nerve trauma. Severe peripheral nerve injuries of the ulnar or median nerve were analyzed in this study. Medical Research Council sensory grades representing absent to normal sensation, motor grades representing visible muscle contraction to normal strength and diffusion tensor imaging scans were performed longitudinally over twelve months postoperatively. Values of fractional anisotropy closely matched clinical evaluations and levels of nerve recovery. We provided an automated, noninvasive approach for characterizing recovery and reducing user-dependent variability in interpretation. These results support Fractional Anisotropy as a potential biomarker to monitor nerve recovery after surgical repair, potentially guiding clinical decisions for additional interventions.