Suprascapular Nerve Anatomy and Function

Suprascapular Nerve Anatomy

• Purely motor nerve, branch of upper brachial plexus
• Passes under trapezius, through suprascapular notch (bridged by superior transverse scapular ligament)
• Supplies supraspinatus and infraspinatus muscles, and shoulder joint capsule
• Rare cutaneous branches have been documented

Suprascapular Nerve Function

• Supraspinatus: primarily responsible for first 15 degrees of arm abduction
• Infraspinatus: primarily responsible for external rotation of the upper arm

Suprascapular Nerve Lesions

• Can be injured in proximal upper brachial plexopathies or supraclavicular region (e.g., shoulder depression, dislocation)
• Fractures/excessive callus at suprascapular notch can compress the nerve
• Rotator cuff repair can cause injury
• Repetitive motions (e.g., cross-body adduction, overhead sports, phone use) are risk factors
• Occupational overuse, sports injuries (tennis, weightlifting, canoeing, volleyball), direct trauma, and ganglion cysts can damage the nerve
• Baseball pitchers and quarterbacks may experience suprascapular entrapment

Suprascapular Nerve Entrapment

• Entrapment can occur at suprascapular foramen (e.g., by ganglia, spinoglenoid cyst)
• Results in characteristic shoulder pain (aggravated by shoulder girdle movements), weakness, and atrophy of spinati muscles.
• Pain is deep, along superior scapula border, possibly radiating to arm
• Pain worsened by scapular adduction or head rotation away from affected shoulder
• Supraspinatus paresis causes abduction weakness; infraspinatus paresis impairs external rotation.
• Entrapment can also affect the infraspinatus muscle directly at the spinoglenoid notch (by hypertrophied inferior transverse scapular ligament or ganglion)
• Isolated infraspinatus weakness/paresis can result from lesions at the suprascapular notch or glenoid notch

Clinical Cases and Specificities

• Cases involving suprascapular nerve entrapment at the suprascapular notch, present with shoulder pain, atrophy, and weakness of supra/infraspinatus muscles
• Case of numbness in the lateral upper shoulder, despite the usually lack of sensory branches
• Isolated infraspinatus paresis is noted in volleyball players and bodybuilders.
• A patient's shoulder pain caused by entrapment, worsened by shoulder girdle movements often radiating to arm, associated with weakness and eventual atrophy of affected muscles
• Trauma and neuralgic amyotrophy are common causes of suprascapular neuropathy, often concurrent or associated with additional nerve involvements.