Brachial plexus

The brachial plexus is the network of nerves that supplies the skin and muscles of the arm and hand. It is formed from the front branches of five spinal nerves, C5, C6, C7, C8 and T1, which leave the lower cervical spine and the top of the chest, and it runs from the root of the neck down into the armpit (TeachMeAnatomy).

How is the brachial plexus built?

Anatomists describe five stages, from the neck outwards (TeachMeAnatomy; Polcaro et al., 2023):

• Roots. The five nerve roots pass between two neck muscles, the anterior and middle scalenes.
• Trunks. At the base of the neck they join into three trunks: C5 and C6 form the upper trunk, C7 continues as the middle trunk, and C8 and T1 form the lower trunk. These cross the side of the neck.
• Divisions. Each trunk splits into a front and a back division, which pass into the armpit.
• Cords. There they regroup into three cords, named after their position around the main artery of the arm. Nerves and artery travel together as one large bundle.
• Branches. The cords give rise to five major nerves: the musculocutaneous, the axillary (which supplies the deltoid), the median, the radial and the ulnar.

Why does the brachial plexus matter at a desk?

Tingling or numbness in an arm is unsettling, especially when it comes on at the keyboard. The nerves of the arm travel a long way, and they can be irritated at several points along it:

• In the neck. A nerve root can be compressed as it leaves the spine. This is cervical radiculopathy: pain that spreads into the arm, chest, upper back or shoulder, sometimes with weakness or reduced reflexes. Its natural course is generally favourable (Margetis et al., 2025).
• At the base of the neck. The space bounded by the first rib, the scalene muscles and the collarbone is called the thoracic outlet. Thoracic outlet syndrome is a broad label for compression of nerves or blood vessels there, and one of its recognised types is described as a disputed nerve form. Most people who are treated appropriately do well (Kaplan & Kanwal, 2023).
• Below the collarbone. The plexus can also be squeezed under the pectoralis minor muscle. That diagnosis rests on a careful history and examination; nerve tests can confirm compression but cannot establish the diagnosis on their own (Sanders & Annest, 2017).
• Further down the arm. The median nerve can be compressed at the wrist, which is carpal tunnel syndrome (NHS), and the ulnar nerve supplies the little-finger side of the hand (TeachMeAnatomy).

Brief pins and needles after sitting or lying on an arm is normal and passes within minutes. The NHS lists a trapped nerve in the neck among the causes of pins and needles that last (NHS).

What helps, and what is uncertain?

That depends on where the problem is, which is why assessment comes first. Physiotherapists sometimes use nerve-gliding movements, known as neural mobilisation. A review of 40 trials found benefits for back and neck pain, but the effect on other conditions remained unclear, and the authors cautioned that conclusions may change as better studies arrive (Basson et al., 2017). For the shoulder and neck side of desk work, see shoulder pain from computer work and neck pain from desk work.

When to see a doctor

See a GP if pins and needles are constant or keep coming back (NHS). Get an urgent GP appointment or call 111 for heaviness or weakness in your arms or legs, or pins and needles in an arm together with neck or arm pain. Call 999 for new problems walking, loss of bladder or bowel control, or sudden clumsiness with tasks such as buttoning a shirt (NHS). An arm that has no feeling or is hot or cold to the touch also needs urgent advice (NHS).