Nerves From the Neck to the Arm (Brachial Plexus)

The brachial plexus is the network of nerves that carries signals between your neck and your arm. It starts as five nerve roots leaving the lower neck and top of the upper back (C5, C6, C7, C8 and T1). These roots join, split and rejoin as they pass between the neck muscles, over the first rib, under the collarbone and through the armpit. They end as the main nerves of the arm. Every movement and sensation from the shoulder down depends on this route.

Because the route is long and passes several tight spots, a nerve can be irritated in the neck, at the base of the neck, near the shoulder blade or further down the arm. Where along the route the problem sits changes the pattern of pain, tingling and weakness you notice.

Key takeaways

Five roots form the plexus: the C5, C6, C7, C8 and T1 nerve roots, leaving the spine from the lower neck and the first level of the upper back.
The route has several tight spots: the opening where each root leaves the spine, the gap between the scalene muscles, the space between the collarbone and first rib, and the area under the pectoralis minor.
Each root supplies a strip of skin: these strips are called dermatomes, and the pattern of tingling or numbness can point toward which root is involved.
Nerve problems feel different from joint or muscle pain: they more often cause burning, sharp, electric or tingling sensations that travel along a line.
Several shoulder blade nerves branch off early: so a nerve problem near the neck can cause pain or weakness around the shoulder blade.

The route, from neck to arm

Anatomists divide the plexus into five sections. You do not need the names to follow the route, but they appear on scan reports and in medical notes.

Roots (C5 to T1): leave the spine through small openings between the vertebrae (the intervertebral foramina), then pass between the front and middle scalene muscles at the side of the neck.
Trunks: the roots join into three trunks just above the collarbone. C5 and C6 form the upper trunk, C7 continues alone as the middle trunk, and C8 and T1 form the lower trunk.
Divisions: each trunk splits into a front and back part as it passes under the collarbone, over the first rib.
Cords: the divisions regroup into three cords in the armpit, named for where they lie around the main artery: lateral, posterior and medial.
Branches: the cords end as the main nerves of the arm. The axillary nerve supplies the deltoid and skin over the outer shoulder. The musculocutaneous nerve supplies the biceps. The radial, median and ulnar nerves continue past the elbow to the forearm, wrist and hand.

Along the way, smaller branches leave early to supply the shoulder blade and chest wall. These include the dorsal scapular nerve to the rhomboids and levator scapulae, the long thoracic nerve to the serratus anterior, and the suprascapular nerve to two of the rotator cuff muscles (supraspinatus and infraspinatus).

What each root supplies, in plain words

Each nerve root supplies a strip of skin (a dermatome) and a group of muscles (a myotome). The maps vary from person to person and overlap, so they are a guide rather than a rule.

C5: skin over the outer upper arm, around where a shoulder patch sits on a uniform. Helps lift the arm out to the side.
C6: skin along the thumb side of the forearm into the thumb and index finger. Helps bend the elbow and lift the back of the wrist.
C7: skin down the back of the forearm into the middle finger. Helps straighten the elbow. The most commonly affected root in the neck.
C8: skin along the little finger side of the forearm and hand. Helps grip.
T1: skin on the inner forearm toward the elbow. Helps spread the fingers.

The C4 root is not part of the plexus, but it supplies the skin over the top of the shoulder. That is one reason neck problems are so often felt there.

A nerve feels its trouble along its whole length, so the place you feel it is a clue, not an address.

Where nerves can be pinched along the way

In the neck: the nerve root

A disc bulge or age-related bony narrowing can press on a root as it leaves the spine. This is cervical radiculopathy. Arm pain is often worse than neck pain, follows one dermatome, and may come with tingling, numbness or weakness. Looking up or tilting the head toward the painful side often makes it worse. Resting the hand on top of the head sometimes eases it. Most cases settle without surgery, often over 6 to 12 weeks, and some take longer.

At the base of the neck: thoracic outlet

Between the scalene muscles, between the collarbone and first rib, and under the pectoralis minor, the plexus travels with the main artery and vein to the arm. Narrowing in these spaces is called thoracic outlet syndrome. The nerve type, the most common, usually affects the lower trunk (C8 and T1). It often causes aching and tingling toward the little finger side, worse with arms overhead or carrying weight. Forms involving the artery or vein are less common and can cause arm swelling, color change or coldness.

Around the shoulder and shoulder blade

Suprascapular nerve: can be compressed in a notch at the top of the shoulder blade or behind the socket. It causes a deep ache at the back of the shoulder with weakness turning the arm outward.
Long thoracic nerve: a long, thin nerve that can be stretched or injured, leaving the shoulder blade sticking out (winging) when pushing or reaching forward.
Axillary nerve: wraps around the back of the upper arm bone and can be stretched in a shoulder dislocation or a fracture of the upper arm, causing a numb patch on the outer shoulder and deltoid weakness.

Further down the arm

The radial, median and ulnar nerves can also be compressed at the elbow, wrist or hand. These problems can feel similar to a neck problem, because they produce tingling in parts of the same strips. A tingle that wakes you at night in the thumb side of the hand, for example, can come from the wrist rather than the neck. Some people have irritation at more than one point along the same nerve.

Stretch and inflammation

In contact sports, the head can be forced to one side while the shoulder is driven down. This stretches the upper plexus and causes a burning, electric pain down the arm (a stinger or burner), which usually fades within minutes. Separately, brachial neuritis (Parsonage-Turner syndrome) is an inflammation of the plexus. It typically begins with sudden, severe shoulder pain, followed days to weeks later by weakness around the shoulder as the pain eases. Recovery is often slow, over many months.

How the nerves connect to the neck, shoulder and upper back

The plexus is the clearest example of why this region works as one. It begins in the neck, passes between neck muscles that attach to the ribs, runs under the collarbone, supplies the muscles that move the shoulder blade and the rotator cuff, and then serves the whole arm. Neck position, shoulder blade position and upper back posture can all change the space the nerves travel through. A forward head and rounded shoulders, for example, narrow the gap between the collarbone and the first rib.

What it means for you: tingling or burning that travels down the arm usually involves a nerve somewhere along this route. The pattern of the symptoms, which movements bring them on, and whether there is weakness help a physical therapist or doctor work out where along the route the problem sits. Nerves heal slowly. After a nerve injury, regrowth is often quoted at about 1 mm a day, roughly an inch a month.

Get it checked if

Arm weakness is getting worse: or you are dropping things, see a doctor today.
Symptoms are in both arms: or come with clumsy hands, unsteady walking, or a change in bladder or bowel control, get urgent medical assessment.
Your arm swells, turns blue or pale, or goes cold: go to the emergency department.
Numbness or weakness follows an injury: such as a fall, dislocation or collision, get it checked the same day.
A stinger lasts more than a few minutes: or keeps recurring, or affects both arms, stop the sport and get assessed before returning.
Sudden severe shoulder pain is followed by weakness: see a doctor soon.