Have you noticed that when you accidentally touch something scalding hot, your hand retracts almost instantaneously? In those few milliseconds, sensory nerves in your hand carry messages from the body to the central nervous system (CNS). Then, motor nerves convey signals relayed back from the CNS to the muscles so that your hand pulls away from the hot object. In that way, nerves have been likened to telephone cables that transmit information to and from the brain.
Major nerves of the hand and wrist
Five major nerve roots arise from the neck to form a complex network and produce three major nerves running down the upper limb, called median, ulnar and radial nerves.
- The median nerve provides sensation to the palm, thumb, the index, middle and part of the ring fingers. It supplies muscles that allow the wrist, thumb and other fingers to flex.
- The ulnar nerve provides sensation to the inner border of the hand, the other part of the ring and little fingers. It supplies the smaller muscles in the hand needed for fine movements such as writing.
- The radial nerve provides sensation to the back of the hand. It supplies muscles that extend (straighten) the wrist, fingers and thumb.
When nerves are injured
Peripheral nerves may contain three components. The sensory component carries sensation back to the CNS. The motor component relays nerve impulses from the CNS to muscles for movement, and the autonomic component is responsible for regulating body processes such as sweating and blood flow. Nerve injury will affect the function of one or all components. Excessive pressure, stretching, cuts by knives or broken glass, or fractures can damage nerves. Nerve injuries are classified into:
This is due to a conduction block of the nerve impulses; the nerve is otherwise structurally intact. This usually occurs after a direct blow to an area. People usually experience a tingling sensation or weakness. Rapid and full recovery is expected, although it may take a while. Surgery is usually not needed. The numbness experienced after a local anaesthetic injection during tooth extraction is another example.
In this type of injury, the tiny nerve fibres are stretched so much that they break. However, the covering of the nerve fibre remains intact. It often occurs after a severe crush or stretch injury that may involve a fracture or dislocation of bones and joints. Recovery is slow and variable, and dependent on the extent of the nerve damage. Surgery may be necessary for recovery.
This is the most severe type of injury because the nerve is cut or disrupted. Surgery is required for nerve recovery.
If a nerve is injured, signals to and from the brain will either transmit slowly or not at all. We may experience numbness, loss of sensation, loss of muscle power or neuropathic pain in the affected area, all of which cause difficulty in movement, clumsiness or weakness. These symptoms will vary depending on the nature of the injury, its severity and the nerves affected.
Diagnosis and treatment
Your doctor will take a thorough history and do a detailed neurological examination. X-rays may be prescribed to look for bony injuries or foreign objects after an injury. Scans may also be recommended. Your doctor may send you for neurophysiological tests to assess the function of the affected nerves.
If there is an open wound with signs of injury affecting the underlying nerve, surgery is the best option to examine and repair the damaged nerve using an operating microscope. It is important to remember that the best chance for nerve recovery is during the first surgery. Delay in treatment may affect nerve recovery.
In closed nerve injury, your doctor may decide to observe and wait for nerve recovery as these may be either neurapraxia or axonotmesis types of injuries. Progress of nerve recovery will be monitored. Generally, as nerve fibres grow at the rate of one inch a month, healing is a slow process. If there is no progress or if the progress stalls after initial recovery on follow up, surgery may be required.
Things to note while healing
After a nerve injury, patients can do several things to aid healing:
- Keep joints flexible through therapy so that they do not stiffen
- If the injury involves a sensory nerve, take extra care to avoid burning or cutting the fingers because there is no sensation to protect the affected area.
- If you experience burning pain or unusual sensation in the affected nerve, tell your doctor; it may be neuropathic pain, which should be treated early.
The extent of recovery following nerve injury is related to the patient’s age, the nerve affected, and the location and type of injury. With timely and proper treatment, there’s a higher chance of the hand regaining normal function.