Nerves are like communication wires in your body. They carry signals to and from your brain. If they are damaged – by physical pressure, stretching, disease, cutting or other injury – the signals between the brain and the nerves stop, which can result in muscle paralysis.
The three primary nerves in the hand are the radial, median and ulnar. When one or all of these are damaged or destroyed, particular palsies develop. Palsy refers to part of the body that has paralysis and loss of feeling. Some palsies also create uncontrollable movement. Because each nerve serves a different part of the hand, the damage will result in a specific type of palsy.
Radial nerve palsy
The radial nerve starts at the shoulder and courses down the arm to supply movement to the triceps muscle at the back of the upper arm. It then continues through the forearm and into your hand. This is the nerve that lets you extend your wrist and fingers. It also provides feeling in the wrist, to much of the back of the hand and to part of the thumb.
Compression or damage to the radial nerve can cause weakness in the wrist and fingers and affect your ability to open your hand to grasp objects. In severe cases, the hand droops downward from the wrist and the fingers are curved. The back of the hand might lose feeling.
Median nerve palsy
The median nerve travels the length of the arm, through the forearm and into the hand. It supplies sensation to the thumb, index and middle fingers as well as the thumb side of the fourth finger. When the median nerve is damaged, the thumb and first two fingers may be numb or have a burning sensation or tingling. Median nerve palsy impedes your ability to use your thumb to pinch. It adversely affects your ability to grip items.
Ulnar nerve palsy
This nerve travels along the medial (closer to mid-body) side of the arm, passing close to the skin’s surface at the inner elbow. The nerve crosses the elbow’s cubital tunnel – the “funny bone” area that yields a brief tingling sensation when struck.
The ulnar nerve then runs down the inside of the forearm and into your wrist before branching across the palm into the little and ring fingers.
The ulnar nerve controls almost all of the little muscles that manage fine movements. It also controls some of the larger forearm muscles needed to create a strong grip. Ulnar nerve damage results in a pins-and-needles feeling and hand weakness. Severe ulnar nerve palsy can result in muscle wasting (atrophy) and a deformity called “claw hand.” This is caused from muscles tightening to the point where the fingers are frozen in a bent position.
Palsies of the hand nerves can be so severe that acts of daily living are difficult or impossible. Hand surgeons can restore muscle functions via tendon transfers