Sharp, penetrating injuries to the extremities, particularly the hands run a risk of damaging the underlying nerves. This will result in loss of the nerve function to the rest of the limb. In the hand this usually means loss of sensation in the fingers or thumb. Higher injuries in the arm can also result in muscle paralysis. In general most nerve injuries should be repaired. In some cases of major nerve injury tendon transfer is an alternative to reconstruct the lost function.
Simple kitchen injuries are a common cause of simple nerve injuries in the hand. More major nerve injuries are seen in motor vehicle accidents, falling through glass or after assault.
From the point of injury down, there is no function in the distribution of the affected nerve. This will usually manifest as a predicable area of loss of sensation and specific muscle weakness. There is sometimes an area of severe tenderness at the site of the nerve injury itself.
Usually the diagnosis is obvious at the time of injury, but in unusual or delayed cases, MRI or nerve conduction testing can be helpful.
A history of a penetrating injury and clinical examination showing loss of function in a specific nerve distribution is usually sufficient for a diagnosis of nerve injury.