Nerve compression is the restriction in the space around a nerve that can occur due to several reasons. Functioning of the nerve is compromised.
There are a variety of circumstances that cause nerve compression. Despite this variety, the resulting damage to the nerve produces a similar diminished functioning of the nerve.
The incidence of brachial plexus palsy, usually a result of birth injury to the nerves that conduct signals from the spine to the shoulder and resulting in a limp or paralyzed arm, is low, on the order of one to two births out of every 1,000. Brachial plexus palsy is associated with a difficult labor, especially compression on the baby's shoulders. Intervention or assistance during labor can lessen the chance of the physical trauma that causes the nerve damage. However, the condition cannot be totally eliminated, especially in times where an emergency response is needed to speed the birth of a fetus in distress.
Meralgia parasthetica, a condition involving compression of the lateral femoral cutaneous nerve, results in paresthesia, or tingling, numbness, and burning pain in the outer side of the thigh. Meraglia paresthetica has traditionally affected men more than women. The condition is not rare, but its overall prevalence is unknown. Meralgia paresthetica may occur after abdominal surgery or significant weight gain, in military members who often march, soccer players, or for no apparent reason in the general population. Other nerve compression maladies such as carpal tunnel syndrome can be quite common.
Causes and symptoms
There are a variety of conditions that lead to nerve compression, according to the affected nerve.
Carpal tunnel syndrome
In carpal tunnel syndrome, the nerves that pass through the wrist are pinched due to the enlargement of local tendons and ligaments. The enlargement occurs due to inflammation, which can be associated with the strain of performing a repetitive task such as typing. Carpal tunnel syndrome is also associated with maladies like diabetes, and with the restricted space that can develop in the wrist as weight is gained during pregnancy or in someone who is obese. The enlargement of the tendons and ligaments restricts the space available for the nerves that reach to the finger and also for the muscle that connects to the base of the thumb. As a consequence, the ability of the nerve to properly transmit impulses to the muscles in the fingers and thumb is affected.
The initial symptoms of carpal tunnel syndrome tend to be felt at night because the hand is at rest. The symptoms can be a burning or a tingling numbness in the fingers, in particular the thumb, along with the index and middle fingers. As well, the reduced transmission of nerve impulses to the muscles decrease muscle strength. It can become difficult to grip an object or make a fist.
In thoracic outlet syndrome , nerve compression can occur as a result of stresses on the neck and shoulders that cause these areas to impinge on local nerves. While the underlying cause of the syndrome is not clear, there seems to be an association between thoracic outlet syndrome and physical labor, in particular the repeated lifting of heavy objects onto the shoulders, causing the shoulders to pull back and down. Reaching for objects that are positioned above shoulder level can also be irritating to muscles in the shoulders and the upper arms. Swelling and inflammation of the muscles can compress nerves between the neck and shoulders.
The symptoms of thoracic outlet syndrome include weakness of the arms, pain, and numbness of the arms and fingers. In more extreme cases, the sense of touch and ability to sense temperature changes can be lost in the fingers.
Brachial plexus palsy
Palsy is a term meaning the inability to purposely move a body part. Brachial plexus palsy refers to paralysis that is associated with compression and tearing of a group of nerves called the brachial plexus. These nerves are a connection between the spinal cord and the nerves that run into the arms neck, and shoulders. The nerves can become compressed and even torn when the neck is stretched. This can occur in an infant born following a difficult delivery, which can occur if the baby is large, in a breech position, or if the period of labor is long. In these situations, the baby's neck can be abnormally flexed. The abnormal position damages the brachial plexus nerves.
The brachial plexus affects certain segments of the spinal cord. When viewed in a x ray, the spinal cord is reminiscent of Lego blocks stacked on each other. Each 'block' represents a segment. Typically, brachial nerves that originate from upper segments of the spinal column (segments C5 and C6) are affected. This condition is also called Erb's palsy. Less commonly, nerves associated with lower segments (C7 and T1) can be deranged. This condition is called Klumke's paralysis. In some cases, all the nerves of the brachial plexus can be affected.
The causes of nerve damage can also involve injuries to the shoulder, arm, and the collarbone (clavicle). The main symptom of brachial plexus palsy, paralysis in an arm, is evident immediately after birth. A newborn will lie with the affected arm by its side, with the elbow extended. While the other arm will be capable of a normal range of motion, the affected arm will be immobile.
This painful condition is due to the pinching of the lateral femoral cutaneous nerve as the nerve exits the pelvis. The nerve can become pinched as the position of the pelvic region changes due to weight gain, injury, pregnancy, or extended periods of standing of walking (i.e., military marching). The affected nerve becomes compressed as it crosses a region of the pelvis called the iliac crest. As well, the nerve can be rubbed during the pelvic motions that occur with walking. This friction increases the nerve damage.
A person with meralgia paresthetica experiences an ache, numbness, tingling, or burning sensations in their thigh. The ache can be mild or severe, and generally eases during rest and returns with resumption of activity.
Cubital tunnel syndrome
This syndrome results from pressure that compresses the ulnar nerve. The ulnar nerve is one of the main nerves of the hand, which connects the muscles of the forearm and hand with the spinal cord. The nerve passes across the back of the elbow behind a bump called the medial epicondyle. The sensation that is described as the funny bone is actually the transient sensation that occurs when the ulnar nerve is compressed in a bump.
Cubital tunnel syndrome is a more protracted from of the nerve compression. It results from the stretching or pushing of the nerve against the medial epicondyle when the elbow is bent. The condition is aggravated over time by the bending of the elbow. Symptoms of cubital tunnel syndrome are typically a numb feeling in the ring finger and small finger, weakness in muscles of the hand and forearm, and elbow pain. Without intervention, more serious nerve damage can occur.
Carpal tunnel syndrome is diagnosed based on the pattern of the symptoms, the location of the symptoms, and a history of repetitive activity that might predispose to the syndrome. Similarly, thoracic outlet syndrome is diagnosed by the location of the symptoms and a person's work history (i.e., a job involving a lot of lifting).
The diagnosis of brachial plexus palsy is prominently based on the visual observation of the motion difficulties experienced by the newborn. X rays may be taken to discount any other injuries such as fractures of the spine, clavicle (collarbone), humerus (the large bone in the upper arm), or a dislocation of the shoulder.
Meralgia paresthetica is diagnosed by the nature of the symptoms and the occupation of the person. For example, hip and thigh pain in a soldier can alert a clinician to the possibility of this malady. As well, people usually experience tenderness in a specific spot over a ligament in the hip, and symptoms can be made worse by extending the hip in the Nachlas test.
Diagnosis of meralgia paresthetica needs to rule out other maladies to the pelvis and spine, as well as diabetes mellitus. For example, damage to spinal discs will impair reflexes, while reflexes are normal in meralgia paresthetica.
Cubital tunnel syndrome is diagnosed by the type and location of the symptoms.
Treatment often involves the family physician, family members, and physical and occupational therapists. In severe cases, a surgeon may be consulted for many types of nerve compression.
Carpal tunnel syndrome responds to immobilization of the affected area. Often, a person will wear a splint that keeps the wrist from flexing. This reduces the strain and pressure on the nerves. Another option is to administer anti-inflammatory drugs or injections of cortisone. These compounds help reduce the swelling in the wrist. In a small number of cases of carpal tunnel syndrome, surgery can be a useful option. The ligament that connects to the bottom of the wrist is cut.
Persons with thoracic outlet syndrome are put on a planned program of exercise therapy designed to relieve the inflammation. Avoiding the repetitive activities that caused the muscle inflammation, at least temporarily, is a must. Re-design of the workplace so that heavy objects do not have to be placed above shoulder level can be a wise strategy. Anti-inflammatory drugs may be prescribed. Finally, if these efforts have not produced a satisfactory response, surgery may be an option.
Treatment for brachial plexus palsy consists of physical therapy that relieves the strain on the affected nerves. The therapy usually involves a gentle range of motions and the use of electrical stimulation of the muscles that are associated with the damaged nerves. Keeping the muscles supple and strong is an important part of the treatment. When a nerve has been more seriously damaged, surgery may be necessary to repair the tear or other damage. This is usually evident within three months of birth. Surgery can involve the grafting of a new section of nerve to replace the damaged and now-defective region of the original nerve.
Treatment for meralgia paresthetica can involve relief of the stress on the pelvis through weight loss or modifying the activity that causes the stress. Treatment for cubital tunnel syndrome can involve the use of medications that reduce inflammation. These include non-steroidal anti-inflammatory medications such as aspirin and ibuprofen. Some people gain relief by wearing a special brace while sleeping that prevents the elbow from bending.
Recovery and rehabilitation
Rehabilitation and recovery from carpal tunnel syndrome can be complete for some people. Avoiding the activity that inflamed the wrist can help ensure that the inflammation and nerve injury does not reoccur. Other people do recover, but more slowly. For others, the syndrome becomes a chronic concern.
Recovery from brachial plexus palsy ranges from limited to complete. Most recovery occurs by two years of age. The Erb's type of palsy is a milder form, and recovery can occur in three to four months. With the more serious Klumke's paralysis, 18–24 months of physical therapy can be required to achieve significant improvement.
Rather than specific clinical trials , research is ongoing to try to better understand the triggers for the various nerve compression syndromes, and to find better and more efficient rehabilitation techniques. In the United States, organizations including the National Institute of Arthritis and Musculoskeletal and Skin Diseases fund such research.
For carpal tunnel syndrome, the outlook for many people is quite good. Once the inflammation has been dealt with, avoiding the cause of the irritation can prevent a reoccurrence of the trouble. However, for about 1% of those with carpal tunnel syndrome, permanent injury develops.
The prognosis for brachial plexus palsy varies upon the nature of the nerve damage. Some cases resolve quickly and completely without intervention, others require extended time and therapy, and in the worst-cases, impaired use of an arm can be permanent.
Meralgia paresthetica due to pregnancy, obesity, and diabetes may resolve completely when the condition is properly treated. Other mechanically-related causes of the malady can be less successfully treated. In the latter case, modification of life-style may be needed.
Most people with cubital tunnel syndrome respond well to conservative treatment, although surgery is necessary for some. For those resulting to surgery, permanent elbow numbness may result.
"Cubital Tunnel Syndrome." (May 4, 2004). e-hand.com. eMedicine.com. Carpal Tunnel Syndrome Information Page." (May 6, 2004). National Institute of Neurological Diseases and Stroke. Canadian Centre for Occupational Health and Safety. (May 6, 2004). <http://www.ccohs.ca/oshanswers/diseases/thoracic.html>.
National Institute for Neurological Diseases and Stroke (NINDS). P.O. Box 5801, Bethesda, MD 20824. (301) 496-5751 or (800) 352-9424. <http://www.ninds/nih.gov>.
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). 31 Centre Dr., Rm. 4Co2 MSC 2350, Bethesda, MD 20892-2350. (301) 496-8190 or (877) 226-4267. [email protected] <http://www.niams.nih.gov>.
Brian Douglas Hoyle, PhD