The hand is supplied by three main nerves, the radial, median and ulnar nerves. Each one takes a different path from the neck down into the arm and hand. They pass through a series of tunnels that can be points of compression, which in turn can cause numbness and tingling.
The superficial radial nerve travels down towards the back of the hand underneath the brachoradialis muscle just before the wrist. It supplies sensation to the dorsum of the thumb, index and middle fingers.
If you tap over the distal forearm and wrist on the thumb side, you can often feeling tingling down towards the numb and back of hand, this is the radial nerve. Because it is so close to the skin surface it can become compressed with anything tight around the wrist such as a watch.
The Ulnar Nerve
The ulnar nerve passes down the inner side of the upper arm and travels between the olecranon and medial epicondyle through a tunnel. This is commonly referred to as the ‘funny bone.’ When you knock it, it is NOT funny and it’s NOT a bone!
The nerve can become compressed here from prolonged elbow flexion like talking on the phone or from leaning on the elbow. The ulnar nerve then continues down the little finger side of the arm towards the hand where it passes through Guyon’s Canal.
If you find your pisiform bone (prominent bone at base of the wrist on little finger side) and put your thumb on a 45 degree angle towards your palm form there, you might feel a bony prominence in the palm. This is the hook of hamate which forms part of the Guyon’s Canal that the ulnar nerve passes through. The nerve can become compressed here from direct pressure, such as holding onto tools or riding a bike.
The Median Nerve
The median nerve, comes down the front of the arm near the biceps muscle. It passes through the two heads of Pronator Teres, a muscle which turns your palm down towards the ground.
Compression here elicits numbness in the base of the thumb and pain with repetitive forearm motion. It is rare in comparison to the more common Carpal Tunnel Syndrome, which is compression of the median nerve at the wrist.
Carpal Tunnel Syndrome can cause weakness in thumb abduction and numbness/tingling into the thumb, index, middle and half of the ring fingers. It is caused by repetitive strong gripping, or prolonged wrist flexion, which often happens when sleeping at night.
A Hand Therapist can assess your arm and determine if one of the nerves is being compressed. Hand therapy treatment may include nerve gliding exercises, splinting, avoiding positions of compression, activity modification, reducing pain and swelling.