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Numbness and Weakness Aren't Always Due to Stroke

Dec. 1, 1999 (Atlanta) -- People complaining of numbness and weakness in the extremities -- the legs and arms -- often associate these symptoms with stroke and seek emergency care. But frequently these symptoms are caused by nerve compression injuries, according to an article in the October issue of the journal IM: Internal Medicine. Neurologists say knowing which nerves are commonly affected can help prevent expensive and unnecessary diagnostic imaging.

"Compression injuries occur when bones and ligaments [constrict] nerves in the arms and legs," says Robert Schwendimann, MD. "In the upper extremities, an injury to the medial nerve occurs most often at the wrist and affects the hands. Of course, this is known as carpal tunnel syndrome. In the lower extremities, injury to the peroneal nerve occurs most often at the knee and affects the feet. This is commonly known as footdrop." Schwendimann is the study author and assistant professor of neurology at Louisiana State University Medical Center in Shreveport.

The peroneal nerve passes over the bony structure on the outside of the knee. Affected individuals tend to have their affected foot pointing toward the ground when they lift it up (hence the term "footdrop") and usually lift that foot up higher when walking.

Schwendimann says there are many causes of nerve compression. "Carpal tunnel syndrome is associated with repetitive activities and frequent use of power tools. It's also more common in patients with diabetes and hypothyroidism," he says. "Footdrop is associated with habitual leg crossing, prolonged squatting, and bedrest. In either case, patients almost always report weakness, numbness, tingling, and pain."

Other common nerve compression injuries are compression of nerves in the forearm or more commonly at the elbow. The nerve compressed at the elbow -- the ulnar nerve -- produces symptoms of tingling and numbness in the ring and little fingers. Most people have experienced these symptoms after resting the elbow on a table or desk for a while. Ulnar compression can also temporarily lead to a weakened grip. But patient history alone is inconclusive.

"Electrodiagnostic studies help determine the extent of the injury so that a plan of treatment can be developed, " Schwendimann tells WebMD. Electrodiagnostic studies measure sensory and motor function by stimulating affected nerves and muscles with electrical impulses. "The tests are uncomfortable but certainly not excruciating," he says. "Kind of like accidentally touching a spark plug wire." Physicians say these studies have other important uses as well.

"Other neurological causes can be ruled out with electrodiagnostic studies," Joseph Brundy, MD, a physiatrist and associate professor of rehabilitation medicine at New York University School of Medicine, tells WebMD. "And that's why they should always be ordered prior to surgery." Physicians also say that conservative treatment should precede surgical intervention for most compression injuries.