Peripheral Nerve Disorders
Many of us have experienced severe burning, numbness, and tingling after hitting our “funny bone.” This is caused by trauma to the ulnar nerve at the elbow. Similar discomfort may be brought on by sleeping on an arm or leg in a funny position.
The brain and spinal cord are considered the central nervous system. Incoming and outgoing information travel in the nerves of the arm similar to a telephone wire. These nerves are considered the peripheral nervous system. Information regarding the environment such as hot, cold, and the position of our pen are carried on sensory nerves. Motor nerves carry bioelectrical information to muscle, resulting in contraction and movement. The other components of this peripheral system are the neuromuscular junction where the nerve meets the muscle and the muscle itself.
Neuropathy is a disorder that prevents nerves from functioning properly. It can cause paralysis if a nerve is completely lacerated, although total paralysis is rare in people with neuropathy. Rather, the disease causes varying degrees of weakness, depending on the type and severity of the neuropathy.
Peripheral neuropathy involves damage to the peripheral nerves that transmit pain and temperature sensations, and can prevent people from sensing that they have been injured from a cut or that a wound is becoming infected. Pain receptors in the skin can also become over-sensitized, so that people may feel severe pain from stimuli that are normally painless (for example, some may experience pain from bed sheets draped lightly over the body).
Examples of peripheral nerve disorders include:
- Guillain-Barre´ Strohl Syndrome: Since the polio vaccine came into widespread use, GBS has become the most common remaining cause of acute neuromuscular paralysis. An acute, ascending, and progressive neuropathy characterized by weakness, paresthesias, and hyporeflexia. In the early 1900s, Guillain, Barre´, and Strohl first described the syndrome in 2 patients who spontaneously recovered from a progressive ascending motor weakness with areflexia, paresthesias, sensory loss, and an elevated level of cerebrospinal fluid (CSF) protein.
- Chronic inflammatory demyelinating polyneuropathy (CIPD)
- Diabetic neuropathies: Tingling in the feet may be caused by a peripheral neuropathy. Early evaluation with laboratory studies may uncover potentially treatable disease such as diabetes and vitamin B12 deficiency.
- Mononeuropathies: Isolated numbness of the hands brought on by excessive keyboard work may be identified as carpal tunnel syndrome, also a treatable problem. Ulnar neuropathies are also included as a type of mononeuropathy.
- Peripheral nerve injuries
- Amyotrophic lateral sclerosis (ALS): Gehrig’s disease, a disorder of the motor nerves resulting in progressive weakness of the limbs, facial and respiratory muscles, is the most serious of the neuromuscular disorders.
- Small fiber neuropathies
- Occupational neuropathies: Industrial and athletic injuries to nerves such as the stinger in football result in arm weakness and tingling.
Peripheral neuropathy produces symptoms such as weakness, muscle cramps, twitching, pain, numbness, burning, and tingling (often in the feet and hands). Symptoms are related to the type of affected nerve and may be seen over a period of days, weeks, or years. Neuropathic pain is difficult to control and can seriously affect emotional well-being and overall quality of life. Neuropathic pain is often worse at night, seriously disrupting sleep and adding to the emotional burden of sensory nerve damage.
Motor nerve damage causes muscle weakness, and symptoms may include painful cramps and muscle twitching, muscle loss, bone degeneration, and changes in the skin, hair, and nails.
Sensory nerve damage may result in a general sense of numbness, especially in the hands and feet. People may feel as if they are wearing gloves and stockings even when they are not. Damage to these fibers may cause people to become insensitive to injury from a cut or that a wound is becoming infected. Others may not detect pains that warn of impending heart attack or other acute conditions. Pain receptors in the skin can also become oversensitized, so that people may feel severe pain from stimuli that are normally painless (for example, some may experience pain from bed sheets draped lightly over the body).
Neuropathy can be a difficult condition to diagnose. To begin, your doctor will take a full medical history and perform a physical and neurologic exam that may include checking your
- Tendon reflexes
- Muscle strength and tone
- Ability to feel certain sensations, and
- Posture and coordination
Your doctor also may request one or more of the following:
- Blood tests to check your level of vitamin B-12
- A urinalysis
- Thyroid function tests and, often
- Electromyography (EMG) a test that measures the electrical discharges produced in your muscles
- A nerve conduction study, which measures how quickly your nerves carry electrical signals. A nerve conduction study is often used to diagnose carpal tunnel syndrome and other peripheral nerve disorders
- Your doctor may recommend a nerve biopsy, a procedure in which a small portion of a nerve is removed and examined for abnormalities. But even a nerve biopsy may not always reveal what’s damaging your nerves.
Returning to the example of hitting your elbow, tingling in your hands is caused by injury to the sensory nerve. If the blow is severe, we may also experience weakness, implying injury to the motor portion of the nerve. In spite of the discomfort, we take solace in the fact that the symptoms are transient and we will soon be back to normal. In some individuals, their motor and sensory problems persist and even progress.
Peripheral neuropathy can result from:
- Nerve compression or entrapment
- Penetrating injuries
- Fracture or dislocated bones
- Intraneural hemorrhage
- Exposure to cold or radiation
- Rarely, certain medicines or toxic substances
- Vascular or collagen disorders such as atherosclerosis, lupus, scleroderma, sarcoidosis, and rheumatoid arthritis.
In some cases, neuropathy is caused by heredity, vitamin deficiency, infection, and kidney disease.
Neuropathy does not usually clear up unless the underlying problem is relieved or removed. Controlling a chronic condition may not eliminate your neuropathy, but it can play a key role in managing it.
Depending on the cause, neuropathy may be relieved by medications, vitamin supplements, physical or occupational therapy, splinting, or surgery. Here’s what your doctor may recommend for treating various underlying conditions:
- Diabetes. If you have diabetes, you and your doctor can work together to keep your blood sugar level as close to normal as possible. Maintaining normal blood sugar levels helps protect your nerves.
- Vitamin deficiency. If your neuropathy is the result of a vitamin deficiency, your doctor may recommend injections of vitamin B-12 daily for a few days, then once a month. If you have pernicious anemia, you’ll need regular injections for the rest of your life, and possibly additional vitamin supplements.
- Autoimmune disorder. If caused by an inflammatory or autoimmune process, your neuropathy treatment will be aimed at modulating your immune response.
- Nerve pressure. Treatment will likely focus on adding ergonomic chairs, desks or keyboards to your home or office, changing the way you hold tools or instruments, or taking a break from certain hobbies or sports. Only in extreme cases of nerve compression will you need surgery to correct the problem.
- Toxic substances or medications. If toxins or medications are responsible for the neuropathy, it’s critical that you avoid further exposure to the toxin.
Peripheral nerve disorders caused by tumors and traumatic and compressive conditions can sometimes be treated surgically. With regards to diabetic neuropathy, surgeons may consider placing a spinal cord stimulator if a patient has medically refractory pain.