Arm Weakness

WHEN TO SEE YOUR DOCTOR

* You experience a loss of sensation or a feeling of numbness lasting more than a few minutes.

* If your arm simply doesn't work, treat it as a medical emergency.

* You've recently had an accident and your arm looks deformed or misshapen, or you hear a popping, clicking or grinding noise from the joints.

What Your Symptom Is Telling You

While the arm is generally designed to take a lot of abuse, certain parts are vulnerable to injury. Quite often, weakness in the upper arm results from a kind of internal squeeze play. At some point between the neck and fingertips, a nerve or blood vessel may be compressed, perhaps between the muscles of the neck and shoulder. Blood flow to the affected area may be slowed to a trickle, and the nerve endings of the arm may not be able to transmit signals to the brain at full strength, creating a sensation of numbness or weakness.

These nerve injuries go by many names—thoracic outlet syndrome (if the compression is somewhere between the shoulder and neck), ulnar nerve entrapment (specifically from the elbow down) and carpal tunnel syndrome (in the wrist and hand)—but they all have one thing in common. They involve the nerves (and sometimes the arteries) that run the length of the arm from the neck down.

Another compression injury, often overlooked, is an ulnar neuropathy, which can occur where the ulnar nerve that passes under the elbow—the so-called funny bone—is injured, causing numbness and tingling in the hand as well as pain in the elbow. People who lean on hard surfaces sometimes develop this problem. Bicyclists report a similar loss of feeling in their fingers. In this case, leaning on the handlebars with their hands puts undue pressure on the ulnar nerve, a hazard known as ulnar tunnel syndrome.

These injuries are usually triggered by repetitive motions of the arm over many weeks or months, says David Rempel, M.D., an assistant professor of medicine at the University of California, San Francisco, and a biomedical engineer specializing in work-related musculoskeletal disorders. For example, electricians, who use a constant twisting motion to turn screwdrivers and wire strippers, are vulnerable to injury in the tendons of the elbow.

All of these abused tendons, ligaments and muscles have a tendency to get good and angry. They puff up and crowd in on the nearby nerve. Although these injuries occur in the elbow, wrist and shoulder, they often cause a sensation of weakness in the forearm or upper arm, says Steven Bogard, lead physical therapist for the Mayo Clinic Hand Center in Rochester, Minnesota.

Symptom Relief

The treatment depends on the diagnosis. Restoring strength to a bum arm can be as benign as rest and as serious as surgery. Here's what to do.

Call in the experts. "If there's a nerve entrapment, the first thing is to determine how severe it is," says Dr. Rempel. "Doctors send some people to surgery right away, especially if the symptoms are persistent. But we start with conservative management: Rest until the symptoms subside, use splints, and perhaps inject cortisone to reduce the inflammation."

Put it to the test. Your doctor may order a battery of electrodiagnostic tests to determine where the nerve is compromised; other tests may measure the arm's sensitivity to pressure or temperature. Your doctor may also assess your grip strength or have you move the affected joint or limb, to determine how weak it is.

Go back to school. You may benefit from some retraining by an occupational or physical therapist to teach you ways of performing your job—or your favorite sport—with less strain on your arm. For example, sitting lower on your bike seat and wearing padded gloves may prevent ulnar tunnel syndrome. Getting special padded armrests may relieve pressure on your elbows, preventing ulnar neuropathy. But the earlier the problem is treated, the better. These injuries are nothing to fool around with. In time, an injured nerve could become damaged beyond repair, causing permanent weakness. "Even if you were to attempt to correct it with surgery later on, the recovery is frequently limited," explains Dr. Rempel. "What doctors really prefer to do is keep the problem from becoming disabling."