Management of Nerve Injuries

Kiran Panesar, BPharmS (Hons), MRPharmS, RPh, CPh

Disclosures

US Pharmacist. 2012;37(10):HS-12-HS-16. 

In This Article

Grades of Nerve Injury

Classification of nerve injury depends upon the nerve components affected, loss of functionality, and the ability to recover spontaneously.[2] Two grading systems are used to stage the extent of nerve injury: Seddon's system and, more recently, Sunderland's system.[2]

Seddon proposed a three-tiered model for nerve injury: neurapraxia, axonotmesis, and neurotmesis, in order of increasing severity. According to this system, the neurapraxial stage involves a reversible conduction block characterized by local ischemia and selective demyelination of the axon sheath.[3] The axon's continuity is retained, and although conduction across the nerve injury is inhibited, conduction within the nerve both proximal and distal to the lesion remains intact.[4] The prognosis for an injured nerve at this stage is good, and recovery occurs within weeks to months.[4] Wrist drop secondary to prolonged external pressure that compresses the radial nerve at the spiral groove of the humerus is a clinical example of neurapraxia.[5]

Axonotmesis is a more severe stage of injury, with disruption of not only the myelin sheath, but the axon as well. The epineurium and perineurium remain intact, meaning that there is still some continuity within the nerve.[3,4] Axonotmesis leads to Wallerian degeneration, a process whereby the part of the axon that is separated from the neuronal cell body disintegrates distal to the injury.[2] The prognosis for nerves at this stage is fair, and recovery may require months.[4] Axonotmesis is commonly seen in crush injuries and displaced bone fractures.[5]

Neurotmesis, the most severe form of nerve injury, is associated with complete nerve division and disruption of the endoneurium.[3] In neurotmesis, the axon, myelin sheath, and connective-tissue components are damaged, disrupted, or transected.[2] As with axonotmesis, neurotmesis initiates Wallerian degeneration, but the prognosis for nerves is poor. Neurotmesis is commonly seen after lacerations or ischemic injuries.

Sunderland's classification, which builds upon Seddon's system, divides Seddon's last stage—neurotmesis—into three subcategories.[5] There are, therefore, five grades of nerve injury according to Sunderland's system (Table 1).

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