Peripheral nerves are responsible for conducting impulses to and from end organs. They can be purely sensory, purely motor or mixed. These injuries may occur as a result of external compression, stretching or complete transection. The usual period of recovery is about 6–8 weeks. However, some nerves may never recover due to permanent damage.

Classifications

Nerve injuries can be classified on the basis of the residual function, pathology and according to the severity of injury.

Complete or incomplete

A nerve injury is said to be complete when all neurones traversing the injured segments are disrupted, leading to complete loss of motor and sensory functions. On the other hand, in incomplete injuries, some neurones remain intact and retain their function resulting in a partial motor or sensory loss.

Pathological classification

Seddon classified nerve injuries into three types: neuropraxia, axonotmesis and neurotmesis.

Neuropraxia: This mild injury is often described as ‘nerve concussion’. It is characterized by a temporary conduction block due to segmental demyelination of the neurones following stretching or compression. Because there is no structural damage to the neurones, function is restored in days or weeks soon after remyelination of the injured segment. A common example of such an injury is ‘Saturday Night Palsy’ which occurs as a result of prolonged pressure on the medial side of the arm against a sharp edge such as the back of a chair.