In vivo Diffusion Tensor Imaging, Diffusion Kurtosis Imaging, and Tractography of a Sciatic Nerve Injury Model in Rat at 9.4T

Abstract

Peripheral nerve injuries result in severe loss of sensory and motor functions in the afflicted limb. There is a lack of standardised models to non-invasively study degeneration, regeneration, and normalisation of neuronal microstructure in peripheral nerves. This study aimed to develop a non-invasive evaluation of peripheral nerve injuries, using diffusion tensor imaging (DTI), diffusion kurtosis imaging (DKI), and tractography on a rat model of sciatic nerve injury. 10 female Sprague Dawley rats were exposed to sciatic nerve neurotmesis and studied using a 9.4 T magnet, by performing DTI and DKI of the sciatic nerve before and 4 weeks after injury. The distal nerve stump showed a decrease in fractional anisotropy (FA), mean kurtosis (MK), axonal water fraction (AWF), and radial and axonal kurtosis (RK, AK) after injury. The proximal stump showed a significant decrease in axial diffusivity (AD) and increase of MK and AK as compared with the uninjured nerve. Both mean diffusivity (MD) and radial diffusivity (RD) increased in the distal stump after injury. Tractography visualised the sciatic nerve and the site of injury, as well as local variations of the diffusion parameters following injury. In summary, the described method detects changes both proximal and distal to the nerve injury.

Diffusion tensor imaging of the roots of the brachial plexus: a systematic review and meta-analysis of normative values

“…Consequently, there has been a surge of research into diffusion tensor imaging (DTI) which may provide additional valuable information. DTI characterises tissue microstructure and provides reproducible [10][11][12][13] proxy measures of nerve health which are sensitive to myelination, axon diameter, fibre density and organisation [14,15]. The parameters typically derived from DTI include the fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD).…”

Diffusion Tensor Imaging for Diagnosing Root Avulsions in Traumatic Adult Brachial Plexus Injuries: A Proof-of-Concept Study

“…We imaged patients years after their injury whereas clinicians need this information is in the weeks/months after injury. DTI parameters reflect changes in the proximal and distal stumps of peripheral nerves in animals within days of injury (14,15,20). DTI is sensitive to Wallerian degeneration in the injured spinal cord of animals (31)(32)(33)(34) and humans (35)(36)(37)(38) within 3 days and for up to 1 year, respectively.…”

“…Diffusion tensor imaging (DTI) characterizes tissue microstructure and provides reproducible proxy measures of nerve health that are sensitive to myelination, axon diameter, fiber density, and organization (14)(15)(16)(17)(18)(19). DTI is sensitive to the diffusion of water, which is anisotropic in the presence of tissue microstructure.…”

“…Diffusivity parameters describe the molecular diffusion rate: the MD is the average rate, AD describes the rate of diffusion in the long axis of the tensor (e.g., up and down the nerves) and RD describes diffusion perpendicular to the long axis of the tensor (e.g., across the cross-section of the nerves). In animal models, healthy peripheral nerves have a higher FA and lower MD than injured nerves (14,15) and DTI based tractography can identify partial and completely divided nerves 7 days after injury (20). Furthermore, DTI may be useful to surgeons in diagnosing root avulsions by examining tractograms.…”

Probabilistic Assessment of Nerve Regeneration with Diffusion MRI: Validation in Rat Models of Peripheral Nerve Trauma

“…DKI indices may offer improved specificity to changes in nerve microstructure; however, the rela-tionship between DKI parameters and peripheral nerve regeneration has yet to be validated. Nevertheless, recent work has indicated that nerve DKI is both feasible and sensitive to nerve injury 31 .…”