MRI of Sports-Related Peripheral Nerve Injuries

Common etiologies of acute traumatic peripheral nerve injury (TPNI) include penetrating injury, crush, stretch, and ischemia. Management of TPNI requires familiarity with the relevant anatomy, pathology, pathophysiology, and the surgical principles, approaches and concerns. Surgical repair of TPNI is done at varying time intervals after the injury, and there are a number of considerations in deciding whether and when to operate. In neurapraxia, the compound muscle and nerve action potentials on stimulating distal to the lesion are maintained indefinitely; stimulation above the lesion reveals partial or complete conduction block. The picture in axonotmesis and neurotmesis depends on the time since injury. The optimal timing for an electrodiagnostic study depends upon the clinical question being asked. Although conventional teaching usually holds that an electrodiagnostic study should not be done until about 3 weeks after the injury, in fact a great deal of important information can be obtained by studies done in the first week. Proximal nerve injuries are problematic because the long distance makes it difficult to reinnervate distal muscles before irreversible changes occur. Decision making regarding exploration must occur more quickly, and exploration using intraoperative nerve action potential recording to guide the choice of surgical procedure is often useful. Show more

MR neurography (MRN) has increasingly been used in clinical practice for the evaluation of peripheral nerve disease. This article reviews the historic perspective of MRN, the current imaging trends of this modality, and the future directions and applications that have shown potential for improved imaging and diagnostic capabilities. Show more

Currently, the evaluation of peripheral nerve disorders depends on clinical examination, supplemented by electrophysiological studies. These approaches provide general information on the distribution and classification of nerve lesions-for example, axonal versus demyelinative-but nerve biopsies are still required to obtain morphological and pathophysiological details. In this article, we review recent progress in the imaging of peripheral nerve injury by magnetic resonance (MR) neurography. Axonal nerve injury leads to Wallerian degeneration, resulting in a hyperintense nerve signal on T2-weighted MR images of the distal nerve segment. This signal is lost following successful regeneration. Concomitant denervation-induced signal alterations in muscles can further help us to determine whether nerve trunks or roots are affected. These signal changes are caused by various combinations of nonspecific tissue alterations, however, and are not related to particular pathoanatomical findings, such as inflammation, demyelination or axonal injury. New experimental MR contrast agents, such as gadofluorine M and superparamagnetic iron oxide particles, allow visualization of the dynamics of peripheral nerve injury and repair. Further clinical development of these MR contrast agents should allow these functional aspects of nerve injury and repair to be assessed in humans, thereby aiding the differential diagnosis of peripheral nerve disorders. Show more