Carpal tunnel syndrome is the most common nerve compression in the arm. It causes the fingers of the hand to fall asleep, become numb, burn or tingle. But that doesn’t mean that everything that causes numbness about the hand is carpal tunnel syndrome.
If the small and ring fingers are the only digits involved, then the numbness is probably caused by cubital tunnel syndrome, ie. compression of the ulnar (funny bone) nerve about the elbow.
Sometimes elbow or shoulder pain, from tennis elbow, rotator cuff disease, etc. can cause pain to radiate down the arm as far as the hand. But these referred pains don’t go all the way down to the fingers and make them numb.
The median nerve, the same nerve that is pinched by carpal tunnel syndrome at the wrist, can also be pinched further ‘upstream’ about the elbow. This is known as pronator syndrome. Often times, pronator syndrome can occur at the same time with carpal tunnel syndrome; this is known as a ‘double crush’, because the nerve is compressed in two places at once.
Pinched nerves at the neck can also cause numbness in the fingers. These usually affect the thumb, but any fingers can be involved, depending on the nerve root that is being pinched.
Of course, the opposite also happens. People often think that they have a pinched nerve in their neck when they’ve really got carpal tunnel syndrome. This happens fairly often because carpal tunnel syndrome is so common and nerve studies fail to diagnose carpal tunnel syndrome in approximately 20-33% of patients.
So how do you know where the problem is?
First, you should see a hand surgeon, who should be an expert in diagnosing conditions affecting the hand. General orthopaedic surgeons, plastic surgeons, and other types of physicians may have some knowledge about hand disorders, but don’t have the subspecialty training and experience to predictably diagnose some of the less common conditions, especially when the signs are subtle. You know what they say about jacks of all trades. You want to see a specialist to give you the best chance of getting the correct diagnosis. The physical examination that a specialist does can usually determine the real source of the problem.
For some ‘quick and dirty’ rules, that aren’t 100% accurate, but can point you in the right direction: carpal tunnel syndrome usually bothers people more at night and when gripping things: a book, a steering wheel, etc. It can affect the thumb, index, middle and ring fingers in any combination. It can also affect the small finger, but not the small finger alone; if the small finger (and maybe the ring finger) are the only fingers involved, then it’s not carpal tunnel syndrome. It may be cubital tunnel syndrome, thoracic outlet syndrome or a pinched nerve in the neck.
Numbness that is worse with activities and is associated with an ache in the forearm near the front of the elbow is often pronator syndrome. Numbness that is worse when the neck is moved all the way to one side is often due to a pinched nerve at the neck. Numbness on the back of the hand is often referred from the elbow or shoulder, and not due to carpal tunnel syndrome.
However, for the best chance of an accurate diagnosis, go see a hand surgeon specialist who has the extra training and experience to best diagnose conditions of the hand.