Peripheral Nerve Injury.

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Abstract

Conflict of interest statement: Disclosure: Mustafa Nadi declares no relevant financial relationships with ineligible companies. Disclosure: Waleed Dabbas declares no relevant financial relationships with ineligible companies. Disclosure: Joe Das declares no relevant financial relationships with ineligible companies. 2. Axonotmesis. Hall WA(1), Munakomi S(2), Nadi M(3). In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2026 Jan–. 2026 Jun 12. Author information: (1)SUNY Upstate Medical University (2)Kathmandu University (3)Al-Balqa Applied University-Dalhousie University Peripheral nerve injuries (PNIs) are a relatively uncommon but potentially devastating health concern. These injuries can occur during common procedures such as spine, foot, and ankle surgeries and arthroplasty, and often lead to litigation. PNI may be traumatic or nontraumatic in nature and can often be iatrogenic. Early identification of injury is of paramount importance because prompt intervention is associated with the best neurological outcomes.   Axonotmesis is a term that describes a range of PNI injuries more severe than a minor insult resulting in neurapraxia but less severe than nerve transection (neurotmesis). Ultimately, these terms describe the various grades of nerve trunk involvement based on an underlying molecular process. However, the descriptive terms used to categorize the degree of nerve damage allow the clinician to determine the mechanism of injury and formulate a therapeutic strategy that sets appropriate expectations for functional outcomes. Familiarity with the basic anatomy of peripheral nerves is essential for understanding each grade of nerve injury. From the most superficial to the very deepest structures, the peripheral nerve contains epineurium (epifascicular epineurium intervening between fascicles), perineurium covering individual fascicles, and endoneurium that envelops axons, wrapped by a myelin sheath and Schwann cells. Seddon first classified nerve injuries into neuropraxia, axonotmesis, and neurotmesis. Sunderland later elaborated on the classification based on histological findings: Grade I: Neurapraxia, wherein only focal segmental demyelination is present; this most often results from entrapment neuropathies or pressure palsies. . Grade II: The axons are damaged, but all the protective perineural sheaths are intact. . Grade III: Damage involves the axons and the endoneurium.  . Grade IV: Damage involves the axons, endoneurium, and the perineurium; this occurs most often following crush and stretch injuries. Grade V: Neurotmesis, wherein even the epineurium is disrupted following massive trauma, sharp injuries, traction, or avulsion injuries.    . Grade VI: This includes multifocal and mixed patterns of injury within the same nerve (most common subtype). Copyright © 2026, StatPearls Publishing LLC.