A 53-yr-old right hand dominant woman presents to clinic with right posterolateral shoulder pain. The pain started 6 mos ago and has been progressive for the past few weeks. She does not recall any traumatic or inciting events. It is described as “dull and aching” and is rated an 8/10 at its worst. Overhead activity and forward reaching aggravate her pain, whereas rest alleviates it. She reports numbness that extends from her right shoulder to all five fingers. This occurs only intermittently. She notes weakness in her shoulder but is unable to report whether this is pain limited. She denies any previous surgeries to her shoulder or neck pain. She is currently taking Tylenol 500 mg three times a day, which is somewhat helpful.
She denies any recent illness, fevers, headaches, weight loss, joint pains, chest pain, shortness of breath, abdominal pain, or any other weakness or numbness.
WHAT ARE THE DIFFERENTIAL DIAGNOSES FOR HER SHOULDER PAIN?
The differential diagnosis includes rotator cuff tendinitis, rotator cuff tear, shoulder impingement syndrome, subacromial bursitis, glenoid labral tear, adhesive capsulitis, humeral fracture, shoulder dislocation, glenohumeral osteoarthritis, thoracic outlet syndrome, brachial plexopathy, suprascapular mononeuropathy, brachial plexitis, and cervical radiculopathy.
Based on her history, it is unlikely that she has a humeral fracture because she did not sustain a traumatic event. There is no report of recent viral illness or nerve stretch injury that would cause a brachial plexopathy or Parsonage-Turner syndrome.
Physical examination reveals:
- - Vitals: Blood Pressure 127/80 mmHg; Heart Rate 71 beats/min; Temperature 97.9°F; Body Mass Index 22 kg/m2
- - She has normal general, cardiac, and pulmonary examinations and 3+ bilateral radial artery pulses.
- - Musculoskeletal: Cervical spine range of motion is full. There is no tenderness to palpation of the cervical paraspinal muscles. There is marked atrophy of the right infraspinatus muscle with associated periscapular tenderness. Right shoulder active range of motion is limited in abduction (160 degrees). There is 4/5 strength in right shoulder abduction and external rotation. There is concordant pain with resisted right shoulder external rotation. Sensation is intact to light touch in the bilateral upper limbs. Reflexes are 2+ in bilateral biceps, triceps, and brachioradialis. O’brien’s and Empty can tests were positive secondary to pain. Drop arm, Neer’s, Hawkin’s, Apley’s Scarf, Speed’s, Anterior Apprehension, Adson’s and Spurling’s tests are negative.
CAN WE NARROW DOWN THE DIFFERENTIAL DIAGNOSIS?
Negative impingement signs put impingement syndrome and subacromial bursitis lower on the differential. Negative apprehension testing and lack of shoulder injury make shoulder dislocation unlikely. Upper limb pulses are intact and Adson’s test is negative, making vascular thoracic outlet syndrome improbable. Limitation of internal rotation range of motion is commonly seen in rotator cuff disease, impingement syndrome, and adhesive capsulitis.
Shoulder pathology including rotator cuff tendinitis, rotator cuff tear, labral tear, suprascapular neuropathy, and glenohumeral osteoarthritis remain on our differential. Neurogenic thoracic outlet syndrome and cervical pathology including radiculopathy (particularly at the C5/6 level) are also possible.
WHAT IMAGING OR LABORATORY STUDIES WOULD YOU ORDER?
- Shoulder x-ray: to identify bony abnormalities/malalignment
- Shoulder magnetic resonance imaging (MRI): can help evaluate muscle bulk and identify soft tissue injuries including rotator cuff pathology.
- Shoulder magnetic resonance arthrogram: this is the best study to look for labral tears.
- Right upper limb electrodiagnostic testing: to assess for neurogenic causes of pain. In this case, particular focus on evaluating the C5/6 root levels and the suprascapular nerve would be necessary
- Ultrasound of the shoulder: to assess the integrity of the rotator cuff and look for bursitis or paralabral cysts
- Cervical spine x-ray: to evaluate for cervical spondylosis that may cause a radiculopathy
Right shoulder x-ray revealed no acute fracture or dislocation; there is mild narrowing of the subacromial space, which could be seen in the setting of rotator cuff arthropathy.1
Cervical spine x-ray showed mild endplate spondylosis and facet arthrosis of C5-6 and C6-7 levels. There is mild C5-6 and C6-7 disc space narrowing.
Nerve conduction studies/electromyography (NCS/EMG) of the right upper limb was also performed with results shown in Table 1. A NCS/EMG study was ordered before an MRI because of the severe atrophy in her shoulder and concern for a neurogenic cause of her symptoms.
HOW WOULD YOU INTERPRET THIS NERVE CONDUCTION STUDY/ELECTROMYOGRAPHY?
Motor nerve conduction studies of the right median and ulnar nerves demonstrated normal distal latencies, compound muscle action potential amplitudes, and conduction velocities. Sensory nerve conduction studies of the right median, ulnar, medial antebrachial cutaneous, and lateral antebrachial cutaneous nerves demonstrated normal distal latencies and sensory nerve action potential amplitudes. Monopolar needle examination of the right infraspinatus demonstrated signs of active denervation with chronic neurogenic changes. All other muscles tested were normal.
- There is electrophysiologic evidence of a right suprascapular mononeuropathy, proximal to the take-off of the infraspinatus.
- There is no electrodiagnostic evidence of right C5-T1 radiculopathy, brachial plexopathy, median mononeuropathy, or ulnar mononeuropathy.
BASED ON THE HISTORY, EXAMINATION, AND TEST RESULTS, WHAT IS THE MOST LIKELY DIAGNOSIS?
Suprascapular neuropathy causing infraspinatus atrophy.
Magnetic resonance imaging of the right shoulder without contrast supported this diagnosis with a report of: A large complex paralabral cyst extending predominantly into the spinoglenoid notch causing severe atrophy of the infraspinatus muscle with fatty infiltration. The cyst is seen to arise from the posterior superior labrum related to a probable underlying labral tear. The tendons of the rotator cuff are intact (Fig. 1).
Infraspinatus atrophy is best evaluated on T1-weighted sagittal oblique MRI views. Findings include decreased muscle bulk compared with the other rotator cuff muscles and fatty infiltration. In this case, an MRI was ordered instead of a magnetic resonance arthrogram because the clinical picture was not highly convincing of a labral tear.
WHAT TREATMENT OPTIONS ARE AVAILABLE?
There is a lack of robust evidence-based data regarding clinical treatment guidelines for symptomatic paralabral cysts; however, there have been smaller studies supporting surgical management of paralabral cysts. A study by Moore et al.2reported that of 6 patients with symptomatic compressive lesions at the spinoglenoid notch who were treated nonoperatively, only 2 showed clinical improvement. By contrast, 15 of 16 patients treated with surgery had decrease in pain and improved strength. Similar results have been reproduced in other studies of symptomatic paralabral cysts.3–6Therefore, orthopedic referral and surgical management to repair the underlying cause of cyst development is warranted in most cases. The specific type of surgical intervention remains controversial. Options include cyst decompression, isolated labral repair, or labral repair with cyst decompression. There have been studies showing good outcomes with each of these surgical options.6
Ultrasound-guided cyst aspiration is another available treatment option. Some studies showed improvement in pain after aspiration; however, these studies were small and had limited long-term follow-up. Recurrence rates after cyst aspiration can be as high as 75%–100%.7–9
For situations of suprascapular neuropathy caused by etiologies other than direct compression and without significant weakness or muscle atrophy, conservative treatment with physical therapy, activity modification, and medication management may be sufficient for symptom resolution.6
The suprascapular nerve arises from the upper trunk (C5, C6 levels) of the brachial plexus and courses along the spine of the scapula. It then passes through the suprascapular notch and continues through the spinoglenoid notch of the scapula. It supplies sensory fibers to the acromioclavicular and glenohumeral joints, as well as motor fibers to the supraspinatus and infraspinatus muscles. Suprascapular nerve injury can occur as a result of traction injury, direct trauma, or from a compression injury from a thickened transverse scapular ligament at the suprascapular notch or a paralabral ganglion cyst. If the injury occurs at the level of the suprascapular notch, both the supraspinatus and infraspinatus muscles will be affected. The suprascapular nerve can also become injured at the spinoglenoid notch resulting in only the infraspinatus muscle being affected.
Paralabral ganglion cysts of the shoulder are fluid filled pockets located around the glenohumeral joint. The mechanism behind cyst formation is from development of a one-way valve system as a result of underlying glenohumeral pathology. This is similar to the mechanism behind a Baker’s cyst or ganglion cyst of the hand. There is a high correlation of paralabral cysts with labral tears.10These cysts can grow large enough to cause compression of the suprascapular nerve at the suprascapular or spinoglenoid notch. Patients with suprascapular neuropathy from a paralabral ganglion cyst usually present with nonspecific shoulder pain that is worsened with overhead activities, along with weakness. Significant findings on examination include pain in the posterior shoulder, weakness with shoulder abduction and external rotation, and supraspinatus and/or infraspinatus atrophy. Most paralabral ganglion cysts do not become clinically apparent until significant compression of the suprascapular nerve occurs, causing pain and muscle atrophy. Diagnostic testing including electrodiagnostics and shoulder MRIs are helpful to localize nerve injury, identify paralabral cysts, or view secondary signs of muscle denervation (muscle atrophy, fatty infiltration, etc).
Treatment of paralabral ganglion cysts causing suprascapular neuropathy usually requires surgical management. Although ultrasound-guided aspiration is possible, high recurrence rates and limited data regarding long-term pain improvement suggest avoidance of aspiration as a sole treatment for paralabral cysts.
Although a relatively rare cause of shoulder pathology, suprascapular neuropathy from a paralabral cyst presents with signs and symptoms that can mimic rotator cuff or labral pathology, making it an important differential diagnosis for shoulder pain and weakness.
This study conforms to all American Journal of Physical Medicine & Rehabilitation Residents and Fellows Section Case Report Guidelines (CARE) guidelines and reports the required information accordingly (see Supplemental Checklist, Supplemental Digital Content 1, http://links.lww.com/PHM/A864).
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