Axonotmesis

Injury classification

There are two kinds of nerve injury classifications:

Assessment

A nerve contains sensory fibers, motor fibers, or both. Sensory fibers lesions cause the sensory problems below to the site of injury. Motor fibers injuries may involve lower motor neurons, sympathetic fibers, and or both.

Assessment items include:

• Sensory fibers that send sensory information to the central nervous system.
• Motor fibers that allow movement of skeletal muscle.
• Sympathetic fibers that innervate the skin and blood vessels of the four extremities.

In assessment, sensory-motor defects may be mild, moderate, or severe. Damage to motor fibers results in paralysis of the muscles. Nervous plexus injuries create more signs and symptoms from sensory-motor problems (such as brachial plexus injuries). In these cases, the prognosis depends on the amount of damage and the degree of functional impairment.

EMG and NCV findings

Changes in EMG

Electromyography (EMG) is a medical test performed to evaluate and record the electrical activity (electromyogram) produced by skeletal muscles using an instrument called electromyograph. In axonotmesis, EMG changes (2 to 3 weeks after injury) in the denervated muscles include:

1. Fibrillation potentials (FP)
2. Positive sharp waves

Changes in NCV (nerve conduction velocity)

EMG test is often performed together with another test called nerve conduction study, which measures the conducting function of nerves. NCV study shows loss of nerve conduction in the distal segment (3 to 4 days after injury). According to NCV study, in axonotmesis there is an absence of distal sensory-motor responses.

Treatment

Schwann cells provide the nerve with protection through the production of nerve growth factors. Because these cells are intact, this kind of nerve injury can be cured and normal feeling and sensations can be restored. Surgery can be done in order to help the nerve heal. The surgery will help with nerve regeneration, providing guidance to the nerve sprouts on where to attach on the proximal side of the injury. Damaged nerve axons can reattach themselves after surgery. Treatment of axonotmesis also consists of:

• Physical therapy or occupational therapy. The aims include:
  • Pain relief
  • Maintain range of motion
  • Reducing muscular atrophy
  • Patient education
• Use of assistive devices (orthotic needs)

Prognosis

The prognosis is usually good in terms of recovery. Rate of recovery depends on the distance from the site of injury, and axonal regeneration can go up to 1 inch per month. Complete recovery can take anywhere from 6 months to a year.

References

References

1. (2002). "Critical Pathways in Therapeutic Intervention.". Mosby Inc..
2. (23 May 2011). "Nerve Injury (Neuropraxia, Axonotmesis, Neurotmesis) and Healing {{!}} Healthhype.com".
3. (2017-05-05). "Peripheral Nerve Trauma: Mechanisms of Injury and Recovery". Hand Clinics.
4. Prince, Jim McMorran, Damian Crowther, Stew McMorran, Steve Youngmin, Ian Wacogne, Jon Pleat, Clive. "Sunderland classification of nerve injuries - General Practice Notebook".
5. Goubier, Jean-Noel. (2015). "Nerve and Nerve Injuries, 1st Edition. Vol 2: Pain, Treatment, Injury, Disease and Future Directions". Academic Press.
6. Otto D. Payton & Richard P. Di Fabio et al. Manual of physical therapy. Churchill Livingstone Inc. Page 24. {{ISBN. 0-443-08499-8