Associated symptoms
Since the most common causes of a drop hand are a shoulder dislocation and an upper arm fracture, there is naturally considerable pain in the shoulder and upper arm in these cases. In addition, nerve damage in the shoulder and upper upper arm area leads to impaired elbow extension and numbness in parts of the back of the hand and the back of the forearm. On the other hand, damage to the middle to lower upper arm usually causes no accompanying symptoms apart from possible pain.
The drop hand itself or the responsible damage to the radial nerve usually does not cause pain. Some affected persons only report somewhat unpleasant sensations in the skin areas supplied by the nerve, i.e. the back of the hand and the back of the forearm. However, since the nerve damage is in most cases the result of a fracture of the upper arm or a shoulder dislocation, the drop hand can of course be accompanied by considerable pain in the upper arm or shoulder.
If the patient is able to localize this pain, this is an important first step towards diagnostic and therapeutic measures. If the palm results from nerve damage near the shoulder – as may be the case with a shoulder dislocation or a fracture of the humerus near the shoulder – this may be accompanied by numbness or even complete loss of sensation in certain areas of the skin. The latter include the thumb-side half of the back of the hand, the central back of the forearm and a small area on the lateral lower upper arm.
Which muscles are affected by a drop hand?
The drop hand is the result of damage to the nerve that transmits the “movement commands” to the hand and finger extensors. Each of these muscles is called the Musculus extensor, with the name of the part of the body it is stretching being added as a third name component for each muscle. Accordingly, there is a Musculus extensor indicis (extensor of the index finger), a Musculus extensor digiti minimi (extensor of the little finger), an inner and an outer Musculus extensor carpi (extensor of the wrist), a broad and a long Musculus extensor pollicis (thumb extensor) and a Musculus extensor digitorum (extensor of all fingers except the thumb).In addition to these finger and hand extensors, the radial nerve also supplies the supinator muscle and the brachioradialis muscle, which primarily perform the outward rotation of the forearm.
It follows that a drop hand can sometimes be accompanied by an inward rotation of the forearm. In addition, the abductor pollicis longus muscle, which is responsible for spreading the thumb, is also under the control of the radial nerve. And finally, the triceps brachii (“triceps”) muscle also receives its impulses from the radial nerve, which is why damage to the nerve in the shoulder region often manifests itself as paralysis of the elbow extension in addition to the drop hand.
