The Anatomy of the Suprascapular Nerve

The suprascapular nerve is a peripheral nerve of the shoulder and arm. It arises from the upper portion of the brachial plexus, which is a network of nerves that stretches across your check from your neck down to your armpit.

The suprascapular nerve’s roots emerge from the fifth and sixth cervical vertebrae (C5 and C6) in your neck. It’s a mixed nerve, meaning that it is made up of fibers for both motor function (movement) and sensory function (feeling).

Anatomy

All of your nerves emerge from either the brain (cranial nerves) or the spinal cord (spinal nerves) in generally symmetrical pairs, so you have one on each side of your body. (They’re most often referred to as a single nerve unless it’s necessary to designate the left or right nerve.)

After they leave their point of origin, nerves then travel toward their destinations, branching out tree-like to supply nerve function to various tissues. The medical term for supplying nerve function is “innervating.”

Once the suprascapular nerve’s roots leave the neck, they come together to form the nerve inside the brachial plexus, then move on to the shoulder.

The suprascapular nerve has four main branches, two motor and two sensory.

The motor branches innervate the:

• Supraspinatus muscle
• Infraspinatus muscle

The sensory branches innervate the:

• Acromioclavicular (AC) joint
• Glenohumeral joint

Structure and Location

After branching from the upper portion of the brachial plexus, the suprascapular nerve travels down and at an outward angle toward the shoulder, passing behind the clavicle (collarbone).

After it reaches the top of the scapula, the nerve passes under the transverse scapular ligament and through the suprascapular notch. It then enters the supraspinous fossa, which is a concave area on the scapula. There, the nerve sends branches inward (toward the spine) to the supraspinatus muscle, which sits high on the scapula.

The nerve then travels through the spinoglenoid notch around the outer edge of the scapula and into the infraspinous fossa and sends terminal branches to the infraspinatus muscle, which is below the supraspinatus muscle.

Branches also travel the other direction, to the:

• AC joint, which connects the clavicle to the scapula (shoulder blade)
• Glenohumeral joint, which is the ball-and-socket joint of the shoulder

The glenohumeral is also innervated by two other nerves: the axillary nerve and the lateral pectoral nerve.

Anatomical Variations

While nerves and other structures in our body have a typical structure, they’re not exactly the same in everyone. In the case of nerves, they also may not be the same on both sides of your body.

It’s important for doctors to know what anatomical variations are possible so they can diagnose and treat nerve problems in people who have these variations. Knowing any alternate nerve routes is especially crucial during surgery, so the surgeon can avoid accidentally damaging the nerve.

The suprascapular nerve has some minor known variations the occur in a small percentage of people:

• Only containing fibers from C5
• Nerve fibers from C4 (the fourth cervical nerve root) in addition to the usual C5 and C6
• A sensory branch that’s cutaneous (serves the skin) over a portion of the shoulder

Function

While it has both motor and sensory roles, the suprascapular nerve’s most important job is providing motor innervation to muscles that are essential for shoulder function.

Motor Function

The supraspinatus muscle is considered the most important muscle of the rotator cuff, which supports the arm at the shoulder joint. It:

• Provides joint stability, which is especially important because the ball-and-socket design sacrifices stability in favor of an especially large range of motion
• Works with the deltoid muscle to pull the arm in toward the shoulder and body

The infraspinatus muscle:

• Also helps provide stability to the glenohumeral joint
• Works with other muscles to rotate the shoulder joint away from the body, raise the arm out straight, and rotate the upper arm away from the body

Sensory Function

The suprascapular nerve, through its sensory branches, provides sensation (i.e., touch, pain, temperature) to the glenohumeral and AC joints.

Associated Conditions

Damage to the suprascapular nerve, depending on its location, can impair the movement of one or both of the muscles it innervates and can reduce sensation to the AC and glenohumeral joints.

Nerve damage can be caused by trauma, disease, or physical abnormalities. Because of the suprascapular nerve’s location, it’s relatively exposed and vulnerable to injury. It’s frequently injured by athletes.

The suprascapular nerve can become entrapped or compressed at either the suprascapular notch (which impacts both muscles it innervates) or the spinoglenoid notch (which impacts only the infraspinatus muscle). A known but rare anatomical variation of the suprascapular notch, called a stenotic foramen, can be the cause of this, as can:

• Repetitive use, especially in athletes who perform a lot of overhead movements
• Trauma, especially rotator cuff tears, glenohumeral joint dislocation, or shoulder fracture
• Lesions, cysts, or other growths
• Disease, especially those that cause inflammation
• Accidents during surgery

The resulting symptoms include neuropathy (nerve pain), which is generally worst at the shoulder blade but extends beyond that area, and reduced function and wasting of the supraspinatus and infraspinatus muscles.

A diagnosis of suprascapular nerve entrapment may involve some combination of a physical exam, magnetic resonance imaging (MRI), and nerve conduction studies.

Rehabilitation

Treatment of suprascapular neuropathy typically starts with conservative measures, such as:

• Rest
• Protection
• Possibly immobilization of the joint
• Anti-inflammatory medications
• Minor lifestyle changes, such as not carrying a backpack on that shoulder
• Physical therapy aimed at strengthening the muscles
• In some cases, corticosteroid injections to help lessen inflammation

Depending on the case, rehabilitation may last for six months to a year. When those approaches don’t have the desired result, pressure on the nerve can be relieved by surgery. Surgery is especially likely in cases of anatomical abnormality.