What is peripheral neuropathy?
Peripheral neuropathy refers to the conditions that result when nerves that connect to the brain and spinal cord from the rest of the body are damaged or diseased.
The peripheral nerves make up an intricate network that connects the brain and spinal cord to the muscles, skin and internal organs. Peripheral nerves come out of the spinal cord and are arranged so that they supply a similar area of the body called dermatomes. Typically, damage to a nerve will affect one or more dermatomes. Damage to these nerves interrupts communication between the brain and other parts of the body and can impair muscle movement, prevent normal sensation in the arms and legs and cause pain.
Types of peripheral neuropathy
There are many different kinds of peripheral neuropathy with many different causes. They range from carpal tunnel syndrome (an injury common after chronic repetitive use of the hands and wrists, such as computer use, to Guillain-Barre syndrome (a rare sudden paralysis).
Peripheral neuropathies are common, especially among people over the age of 55. In fact, the conditions affect 3% to 4% of people in this age group.
Neuropathies are typically classified according to the problems they cause or what is at the root of the damage. There also are terms that express how extensively the nerves have been damaged.
Damage to a single peripheral nerve is called mononeuropathy. Physical injury or trauma, such as from an accident, is the most common cause. Prolonged pressure on a nerve, caused by extended periods of being sedentary such as in a wheelchair or bed, can trigger mononeuropathy as can continuous repetitive motions. If the fibrous shock-absorbing discs that lie between the bones in the back are damaged, they could press on a nerve and cause this type of neuropathy.
Carpal tunnel syndrome is a common type of mononeuropathy. It is called an overuse strain injury, which occurs when the nerve that extends through the wrist is compressed. People whose work requires repeated motions with the wrist extended (such as assembly-line workers, physical labourers and those who use computer keyboards for prolonged periods) are at greater risk.
The damage to the nerve can result in numbness, tingling, unusual sensations and pain in the first three fingers on the thumb side of the hand. This particularly happens while you are sleeping. In time, carpal tunnel injuries can weaken the muscles in the hand. You may also feel pain, tingling or burning in your arm and shoulder.
Here are examples of other mononeuropathies that can cause weakness in the affected parts of the body, such as your hands and feet:
- Ulnar nerve palsy occurs when the nerve that passes close to the surface of the skin at the elbow is damaged.
- Radial nerve palsy is caused by injury to the nerve that runs along the underside of the arm.
- Peroneal nerve palsy results when the nerve at the top of the calf behind the knee is compressed. This leads to a condition called "foot drop".
Neuropathy can affect nerves that control muscle movement (motor nerves) and those that detect sensations such as coldness or pain (sensory nerves). In some cases, it can affect internal organs such as the heart, blood vessels, bladder or intestines. Neuropathy that affects internal organs is called an autonomic neuropathy.
Mononeuropathy multiplex is when several isolated nerves are involved.