Nerve injury Overview

Classification of nerve injury

Seddon 1943

  1. Neurapraxias -  in motor nerves involve dyesthesias and/or paralysis without loss of nerve sheath continuity and peripheral Wallerian degeneration. Recovery may take months but usually is complete.
  2. Axonotmesis -  involves internal nerve fiber damage with complete Wallerian degeneration. The neural tube (endoneurium) remains intact and can guide the regenerating nerve fibers to their target. Spontaneous functional recovery is expected.
  3. Neurotmesis describes the division of the nerve. Functional recovery without surgical intervention is not possible.

Sunderland 1951

Expanded Seddons description to include three subsets of neurotmesis. Involves five degrees of nerve injury where the first two degrees correspond to neurapraxia and axonotmesis.

  • First degree -  neurapraxia, segmental demylination without loss of nerve continuity or Wallerian degeneration.
  • Second degree - axonotmesis,  injury to the axon, but intact endoneurial tissue and Schwann cell tubes.
  • Third degree - involves axon discontinuity with loss of the endoneurial tubes and incomplete spontaneous recovery
  • Fourth degree -  complete disorganization of nerve structure but preservation of nerve sheath continuity eg neuroma
  • Fifth degree -   complete division of the nerve trunk, neurotmesis


These classifications are useful in that they allow a prediction of spontaneous nerve recovery. Patients with Sunderland Grade 1 (neurapraxia) and Grade 2 (axonotmesis) injuries would be expected to recover fully whereas patients with Grades 3 to 5 (neurotomesis) would require surgery.
Diagnosis always begins with a careful examination and documentation. Evolution of nerve injuries is important in indicating the need for open treatment. Nerve conduction velocities after neurapraxic injuries initially may be normal but slowing usually occurs at 1 to 3 weeks. Conduction velocities may stay within normal limits as many as 7 days after axonotmesis. Denervation changes are seen at approximately 1 month with rein-nervation potentials seen at 6 to 8 weeks. It is recommended that nerve conduction studies be delayed until 3 to 4 weeks after injury. One major disadvantage of electrodiagnostic studies is that although Wallerian degeneration can be detected, the status of the connective tissue component of the nerve cannot be assessed without direct exploration.

References

Ristic, Sasha MD. Strauch, Robert J. MD. Rosenwasser, Melvin P. MD. The Assessment and Treatment of Nerve Dysfunction After Trauma Around the Elbow. Clinical Orthopaedics & Related Research. (370):138-153, January 2000.

Last updated 11/09/2015