Axonotmesis
Injury to the peripheral nerve of one of the extremities of the body
- 3 min read
- 5 chapters
Related on Lably
Through Nerve, Myelin and Skeletal muscle
Axonotmesis mainly follows a stretch injury. These stretch injuries can either dislocate joints or fracture a limb, due to which peripheral nerves are severed. If the sharp pain from the exposed axon of the nerve is not observed, one can identify a nerve injury from abnormal sensations in their limb. A nerve conduction velocity (NCV) is done to diagnose the issue. Electromyography is performed after 3 to 4 weeks of injury shows signs of denervations and fibrillations, or irregular connections and contractions of muscles.
Injury classification
There are two kinds of nerve injury classifications:
Sign in to keep reading
4 more chapters are free with a Lably account.
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.
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:
- Fibrillation potentials (FP)
- 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.