ICS Staff | Nov 4, 2020 | 0
Suprascapular Neuropathy: An overlooked cause of superior shoulder pain and weakness
This article highlights a commonly missed diagnosis: suprascapular neuropathy. The condition accounts for approximately 2-4% of all shoulder pain but is present in up to 8% of patients with a full-thickness rotator cuff tear. Check out the following quick synopsis for up-to-date assessment and management considerations.
Introduction & Etiology
The suprascapular nerve arises from branches of the C5 and C6 spinal nerve roots, with a variable contribution from C4. (1) The suprascapular nerve innervates the supraspinatus and infraspinatus muscles, providing shoulder abduction and external rotation, respectively. The suprascapular nerve supplies sensation to several shoulder structures, including the coracohumeral ligament, coracoacromial ligament, subacromial bursa, acromioclavicular joint, and glenohumeral joint. (1) While early anatomical studies did not recognize a cutaneous branch, more recent dissections have identified sensory innervation to the lateral deltoid region. (2,3)
Suprascapular nerve injury typically occurs via compression or traction. (4) Suprascapular nerve dysfunction and rotator cuff pathology are frequent co-morbidities, in that rotator cuff pathology leads to suprascapular nerve dysfunction and vice versa. (4) The most common cause of suprascapular neuropathy is traction ischemia at the suprascapular notch or spinoglenoid notch from retracted rotator cuff tears. (4-8) Although suprascapular nerve dysfunction is relatively uncommon, accounting for 2-4% of all shoulder pain, the condition is present in up to 8% of patients with a full thickness rotator cuff tear. (5,8,12)
Suprascapular neuropathy is typically unilateral and affects the dominant side more frequently. (9) The clinical presentation includes posterior superior shoulder pain and weakness. (4) Patients may complain of increased symptoms upon cross body adduction or internal rotation. (10) Overhead motions may exacerbate symptoms. (11) Pathoanatomically, more proximal lesions tend to produce both sensory and motor complaints, while more distal lesions (i.e. spinoglenoid notch) may result in a relatively painless denervation of the infraspinatus. (9)
Clinical evaluation may demonstrate tenderness to palpation over the suprascapular notch, i.e., deep and posterior to the AC joint, between the spine of the scapula and clavicle. (13) Range of motion testing may demonstrate weakness upon resisted shoulder abduction (supraspinatus) and/or external rotation (infraspinatus). Chronic cases may demonstrate palpable atrophy of the supraspinatus or infraspinatus muscles. Check out this demonstration of isolated strength testing for each rotator cuff muscle.
Diagnostics & Differential
EMG provides a definitive diagnosis. (14) Differential diagnostic considerations include: rotator cuff pathology, cervical radiculopathy, Parsonage Turner Syndrome (acute brachial neuritis), upper thoracic or costovertebral dysfunction, neoplasm, and myofascial pain.
Plain film radiographs, including suprascapular notch and Stryker notch views (hand on top of head, fingers pointing backward), may be used to rule out bony pathology. (10,15) MRI is more definitive, and positive findings include edema in acute cases, with atrophy and fatty replacement becoming more apparent as the condition progresses. (17) MRI also has the ability to rule out compressive pathology, including ganglion or paralabral cysts. (18,19) Ultrasonography is an alternative imaging option for suprascapular neuropathy. (17)
Treatment typically includes rest with avoidance of activities that place sustained or repetitive stress on the nerve. Patients should avoid excessive scapular protraction, cross body adduction and overhead movements. (14) Conservative management can provide benefit. (4) However, exercises that cause sustained stretch of the suprascapular nerve are contraindicated. (14) Physiotherapy modalities may help to relieve pain. Oral anti-inflammatories may decrease inflammation.
Medical alternatives include steroid injections and surgical decompression in cases of persistent symptomatology or muscle atrophy. (20,21) Suprascapular nerve decompression typically relieves pain; however, return of normal muscle bulk and strength is less predictable. (4)
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