Up to 20% of people with carpal tunnel syndrome will have normal nerve
conduction tests. That being said, in the labor
& industries world, the nerve conduction studies are taken as the only "objective" measure and they will not authorize surgery if they are normal--even with motor and sensory loss
on exam. Normal conduction can occur if only a few fibers of the nerve are not affected, even if the rest are severely affected.
That being said, there is no standard definition of carpal tunnel syndrome and no "gold standard" test. That is, it is a complex pattern of symptoms and exam findings that varies between patients. There is a group in canada working on a scoring system, combining symptoms and physical exam findings, but it has not yet been validated.
Textbook carpal tunnel syndrome involves numbness and tingling
in the thumb, index, middle, and half the ring fingers. Symptoms tend to be worse at night and with activities such as driving and holding a phone. Pressure on the nerve or tapping on the nerve reproduces the symptoms.
However, many people have atypical presentations, such as predominantly wrist pain
or numbness involving the whole hand. Here is where a good physical exam can be helpful. If i'm really not sure, i sometimes use an injection in the carpal tunnel to see if the symptoms improve. A good response to an injection usually indicates a good response to surgery.
As the other surgeons have alluded, carpal tunnel syndrome is primarily a surgical condition. Studies have shown surgery to be more cost-effective than therapy and injections. 80% of people who get relief from injections will go on to need surgery. Only early, mild cases respond to bracing
A thorough examination of the nerves in the forearm and hand can help establish the diagnosis and differentiate carpal tunnel syndrome from other nerve compressions or other causes of numbness and tingling. This is where a hand surgeon
is often better than a general orthopaedic surgeon or other type of clinician. A good neurologist can also help with the diagnosis.