Testing for carpal tunnel syndrome involves clinical testing and diagnosis as well as specific physiologic tests that are performed by a neurologist. At its core, Carpal tunnel syndrome is a clinical diagnosis. That means that the testing to confirm that carpal tunnel syndrome is responsible are based on history, what the patient tells us about their symptoms, and a physical examination confirming that carpal tunnel syndrome is likely to be the cause. The physiologic tests are done by a neurologist and they are actually tests that can measure the function of the nerves in the upper extremity. That will tell us if the nerve traveling through the carpal tunnel which is called the median nerve is the only nerve affected and if it's affected in the carpal tunnel. That helps to confirm that in fact, carpal tunnel syndrome is the cause of a patient's symptoms. The clinical tests for carpal tunnel syndrome involve examining the nerve and its surrounding environment to see if the nerve is behaving in an irritable fashion. A normal healthy nerve is not easily stimulated externally. If you tap on a nerve over its course through the wrist, nothing should happen. If you tap on a nerve that's irritated by compression, which is what happens in carpal tunnel syndrome, that nerve will be stimulated more easily and patients will experience numbness and tingling in their fingertips. That numbness and tingling is in the distribution of that nerve. So in the carpal tunnel, which is the median nerve tapping on the wrist forcefully such as this will cause numbness and tingling in the thumb through ring fingers. That's called a tunnel sign and it's one of the things we use to confirm that patients have carpal tunnel syndrome. The other way we can test for carpal tunnel syndrome externally is by reproducing that position that increases pressure in the carpal tunnel with the wrist flexed for any length of time. We ask the patient to flex the wrist and then we add a little external compression with our thumb over the carpal tunnel and in patients whose nerve is irritated from carpal tunnel syndrome, that will start to produce numbness and tingling in the thumb through ring fingers, the distribution of the median nerve. That's called a Phalen's test, and it's another test that we use to confirm carpal tunnel syndrome.
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