Imaging diagnosis in peripheral nerve injury

Carpal tunnel syndrome is the most common peripheral nerve entrapment syndrome worldwide. The clinical symptoms and physical examination findings in patients with this syndrome are recognised widely and various treatments exist, including non-surgical and surgical options. Despite these advantages, there is a paucity of evidence about the best approaches for assessment of carpal tunnel syndrome and to guide treatment decisions. More objective methods for assessment, including electrodiagnostic testing and nerve imaging, provide additional information about the extent of axonal involvement and structural change, but their exact benefit to patients is unknown. Although the best means of integrating clinical, functional, and anatomical information for selecting treatment choices has not yet been identified, patients can be diagnosed quickly and respond well to treatment. The high prevalence of carpal tunnel syndrome, its effects on quality of life, and the cost that disease burden generates to health systems make it important to identify the research priorities that will be resolved in clinical trials.

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.