Physiology | Radial nerve

Physiology

The radial nerve is responsible for controlling some muscles of the upper arm, forearm and hand and thus for extension in the elbow joint, pulling the arm towards the upper body (adduction in the shoulder joint), overstretching the wrist in the direction of the back of the hand (dorsal extension), spreading the fingers, outward rotation (supination) of the forearm. The most important muscles supplied are: Other muscles supplied by the radial nerve:

  • Three-headed upper arm muscle (M. triceps brachii): Extension of the elbow joint;
  • Upper arm spoke muscle (brachioradialis muscle): Outward rotation (supination) of the forearm, flexion in the elbow joint;
  • Finger extensor (M. extensor digitorum): Extension of wrists and finger joints;
  • Outward twisting muscle (M. supinator): Outward twisting of the foramen;
  • Long thumb spreader (M. abductor pollicis longus): Spreading of the thumb
  • Small finger extensor (M. extensor digiti minimi)
  • Thumb extensor (M. extensor pollicis)
  • Index finger extensor (M. extensor indicis).

The skin of the lateral upper arm and back forearm is sensitively supplied by the radialis/spoked nerve. Half of the back of the hand (thumb, index finger, half of the middle finger) also belongs to the sensitive supply area of the nerve. This does not include the end phalanges of the index and middle finger, which are supplied by the sibling nerve, the median nerve, the middle arm nerve.

Damage

“Crutch paralysis”: the radial nerve (spoke nerve) is pressed in the armpit, for example when using crutches. In this case, the extension in the elbow joint and the extension in the wrist (“drop hand“) is omitted. The feeling on upper and lower arm is missing.

If the upper arm is fractured, the nerve can be injured on its way around the upper arm (lesion of the nerve).The elbow can then still be stretched, but otherwise all functions are missing, as in “crutch paralysis”. If there is only pressure on the nerves in the pit of the spoked nerve on the upper arm, this is called “park bench paralysis”. In most cases, this paralysis will disappear again.

If the passage through the outward twisting muscle (supinator canal) is narrowed, a “drop hand” and impairment of sensory perception on the forearm also occurs. This damage is called supinatorlogen syndrome. If other nerves in addition to the radial nerve are also damaged, complete brachial plexus paralysis can also occur.