Peripheral nerve injuries require the coordinated management of neurologists and surgeons to fully appreciate the indications for and timing of surgical intervention. The author thoroughly addresses the presentation, epidemiology, and surgical and nonsurgical outcomes of commonly encountered brachial plexus and peripheral nerve injuries. In this update, the author discusses the potential role of stem cells in peripheral nerve regeneration.
• Nerve injury can range from minor and transient alteration in sensation to severe and permanent interruption of sensory and motor function.
• Timing of nerve injury repair depends on the mechanism of injury, the presence of recovery, and the anatomical location of the injury.
• Nerve grafting techniques and augmentation strategies promise to improve rates of functional recovery in the future.
Historical note and terminology
Historically, classification of nerve injuries was developed and used primarily for the assessment of war-related injuries. In 1943, Seddon introduced a classification system based on 3 types of nerve injury (Seddon 1943). Later, Sunderland expanded on this system by creating a classification based on 5 degrees of injury severity (Sunderland 1978). Both systems base themselves on peripheral nerve anatomy with particular emphasis on the endoneurium, perineurium, and epineurium, which are the key connective tissue elements within a peripheral nerve. Both systems also attempt to correlate the severity of the injury with the patient's clinical manifestations.
Seddon's simple classification yielded 3 terms that have become widely accepted as descriptors of the different types of nerve injury. Neurapraxia, the mildest form, is often incomplete and produces a transient loss of function. Its key feature is spontaneous recovery that occurs within hours to several months of injury and corresponds with Sunderland grade 1 injury. Axonotmesis, or Sunderland grade 2 injury, refers to a complete interruption of the axon and myelin sheath while preserving the endoneurial core connective tissue structure of the nerve. Often described as a “neuroma-in-continuity,” this type of injury results in an immediate loss of motor, sensory, and autonomic function distal to the lesion. Spontaneous recovery can occur but requires more time than a neurapraxic injury and depends on a number of factors that affect the rate of nerve regeneration. The final type of injury, neurotmesis, implies a complete disruption of both the neural and connective tissue elements of a peripheral nerve. This type of injury is incompatible with spontaneous recovery and will ultimately require surgical intervention if any function is to be regained (Seddon 1943; Gentili and Hudson 1996). Sunderland grade 3 injury describes transection of the nerve axon and sheath with preservation of the perineurium, and thus, includes elements of both axonotmesis and neurotmesis. The distinction between Sunderland grade 4 and 5 has to do with preservation of the epineurium in the former.
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