After a nerve is cut, you will notice numbness on an area of skin if it is a sensory nerve or be unable to move some muscles if it is a motor nerve. Some nerves e.g. the median, ulnar or radial nerves in the hand, have both motor and sensory function, so an injury to these nerves can produce more than one effect in your hand. When a nerve is cut, the cut end starts to sprout and try to bridge the gap between the two cut ends. If these cut ends are not realigned, there will not be a recovery of the original function of the nerve and a painful swelling called a neuroma can develop.
The nerve can be repaired. To do this, the cut ends are matched up together under magnification and very fine sutures are placed around the outer surface to hold them together. If the repair is in an area where if stretched the stitches could break, a protective splint is placed for two to three weeks afterwards.
Repairing the nerve will not restore sensation or muscle function immediately. Not only do the two ends have to heal together, the nerve fibres that carry electrical impulses to and from the brain also have to regenerate. This is a very gradual process (about 1mm per day from two to three weeks after the injury) so there is a very gradual return of function. Muscle power or skin sensation may not return to pre-injury levels. In the begining, sensation can be a tingling sensation or overly sensitive rather than normal sensation. The younger you are, the quicker and the better the recovery time. Also the higher up your arm the injury occurs, the slower the recovery time for your hand as the nerve recovery has a longer distance to travel to the target muscle or skin. Having the nerve repaired reduces the risk of a neuroma forming and allows the nerve a chance to recover and restore function. If nerve recovery is not satisfactory, procedures such as nerve grafting or tendon transfers may be necessary to restore function to your hand.