Our eight-year-old sliced his hand on a broken drainage pipe. The surgeon thinks the nerve that got cut might recover. For now, our son in in a special splint but surgery might be needed in the future. How are these things decided anyway? We are on pins and needles worrying about what’s going to happen.

There are three major nerves to the muscles of the arm: the radial nerve, ulnar nerve, and median nerve. There can be a high nerve injury (above the elbow) or low nerve injury (below the elbow).

An injury to any of these nerves produces a predictable loss of hand and/or arm function depending on which muscles have been affected. Whether it is a high or low nerve injury also determines what muscle function has been lost or altered.

If the nerve has not been completely cut and if the damage done is not too severe, it can regenerate. This process of reinnervation and recovery is very slow. Often, it is a wait-and-see proposition. By watching for signs of muscle function, surgeons can gauge how long the patient must wait for complete recovery and whether or not surgery is needed.

Electrodiagnostic testing can be done. The two main tests available are electromyography (EMG) and nerve conduction velocity (NCV). The EMG test measures the electrical impulses to the muscle (that’s what makes them contract). The NCV shows where the signal is moving (or stopping) along the nerves.

With repeated tests over time, it’s possible to see progress as the signal moves farther down the nerve and/or creates a stronger muscle contraction. If no change is registered over time, then surgery is considered to repair the nerve or possibly transfer a working tendon to replace the tendon/muscle unit no longer working because of nerve damage.