Suprascapular Nerve Palsy

By admin Last updated Nov 9, 2023

Ovid: 5-Minute Sports Medicine Consult, The

Philip H. Cohen

James C. Puffer

Basics

Epidemiology

Relatively uncommon; true incidence unknown
May occur in up to 45% of international-level volleyball players
Ganglion cyst found at spinoglenoid notch in 1% of cadavers in one study
Spinoglenoid ligament present in 50–60% of shoulders
Suprascapular neuropathy in 7% of athletes with peripheral nerve injuries

Risk Factors

More common in volleyball players and overhead throwing athletes, possibly owing to traction injury or scar formation from overuse
May be particularly associated with “floating serve” in volleyball, which requires intense eccentric contraction of infraspinatus to decelerate the arm and stabilize the shoulder; this can stretch the suprascapular nerve across the lateral edges of the scapular spine.
Sudden downward depression of shoulder (traction injury to nerve near plexus origin)
Compression by ganglion cyst, tumor, posttraumatic calcification, vascular malformation, or ligament at scapular or spinoglenoid notch
Direct trauma, eg, scapular fracture

Etiology

Suprascapular nerve arises from the upper trunk of the brachial plexus at Erb's point, carrying fibers from the C5 and C6 nerve roots with variable contributions from C4.
It crosses the posterior triangle of the neck, runs deep to the trapezius, and passes under the transverse scapular ligament via the scapular notch.
Crossing the supraspinatus fossa, it sends 2 branches to the supraspinatus and sensory branches to the acromioclavicular and glenohumeral joints.
The nerve makes a sharp turn around the spinoglenoid notch and passes into the infraspinatus fossa, where its branches terminate.
3 main sites of injury:
- Scapular notch
- Spinoglenoid notch
- Near the origin from the upper trunk of brachial plexus

Diagnosis

History

Traumatic versus atraumatic? May yield clues to mechanism of injury; traction injury caused by blunt trauma has a good prognosis.
Painful versus painless? Painless weakness suggests distal lesion.
Overhead-throwing athlete? If yes, this may increase risk of suprascapular nerve lesion.

Physical Exam

Signs and symptoms depend on level of injury.
If proximal, may have posterior/lateral shoulder pain along with weakness and atrophy of supraspinatus and infraspinatus
If lesion is distal to sensory branches at spinoglenoid notch, painless, isolated infraspinatus atrophy and weakness of external rotation may be seen.
Inspection is key. Look for supraspinatus or (especially) infraspinatus atrophy.
Rule out cervical radiculopathy and other C-spine pathology (complete neck exam, including the Spurling maneuver)
External rotation testing against resistance to evaluate infraspinatus strength
Jobe test to evaluate supraspinatus strength
Complete neurologic examination to determine type, origin, and extent of injury; note that deep tendon reflexes should not be affected in isolated suprascapular neuropathy.
Thorough shoulder examination to evaluate for associated injury
Tenderness to palpation at scapular notch present in up to 77% patients
Cross-body adduction test (forward flexed arm externally rotated and adducted across body) puts tension on suprascapular nerve at spinoglenoid notch; may help to differentiate from rotator cuff lesion
Injection into scapular notch may help to determine source of pain but is rarely necessary.

P.565

Diagnostic Tests & Interpretation

Imaging

Plain films of the neck and shoulder evaluate for bony abnormalities.
30-degree cephalic tilt view helps to visualize the scapular notch; obtain especially if scapular fracture.
MRI may be used to detect ganglion cysts and tumors affecting the suprascapular nerve, as well as other shoulder pathology (rotator cuff injury, labral tears, etc.).
US can be similarly useful in detecting lesions affecting the suprascapular nerve; it also can be quickly used to evaluate the rest of the shoulder girdle during the same exam. However, it is extremely operator-dependent.

Diagnostic Procedures/Surgery

Electromyography of entire shoulder girdle
Nerve conduction velocity studies from Erb's point to the supraspinatus, with comparison to unaffected side
Wait minimum 3–4 wks after onset of complaint before neurodiagnostics because false-negative results may occur if done earlier.

Differential Diagnosis

Cervical radiculopathy
Brachial plexopathy/“stinger”
Rotator cuff tendonitis/tear
Labral pathology
Turner-Parsonage syndrome/neuritis

Treatment

Unless there is a well-defined lesion causing suprascapular nerve compression, nonoperative therapy is recommended. This includes:

Rest from overhead movements/throwing/exacerbating activities
Physical therapy to strengthen external rotation and stabilize scapula
NSAIDs or analgesics if needed

Surgery/Other Procedures

If labral tear with associated ganglion cyst causes symptoms, repair/débridement of Labral tear may allow cyst to resolve, thereby relieving pressure on the suprascapular nerve.
If conservative management not beneficial after 3–6 mos, refer for surgical exploration.

Ongoing Care

Complications

Ganglion cysts at the spinoglenoid notch may be secondary to labral injuries, especially superior labrum anterior and posterior lesions.
Secondary impingement may develop owing to loss of supraspinatus/infraspinatus function.

Additional Reading

Butters KP. Nerve lesions of the shoulder. In: DeLee JC, Drez D, eds. Orthopaedic sports medicine: principles and practice. Philadelphia: WB Saunders, 1994:657–663.

Chochole MH, Senker W, Meznik C, et al. Glenoid-labral cyst entrapping the suprascapular nerve: dissolution after arthroscopic debridement of an extended SLAP lesion. Arthroscopy. 1997;13:753–755.

Toth C. Peripheral nerve injuries attributable to sport and recreation. Neurol Clin. 2008;26:89–113.

Codes

ICD9

354.8 Other mononeuritis of upper limb