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RFS – Clinical Vignette

Acute Shoulder Pain and Weakness in a Young Female Dancer

A Clinical Vignette

Chokshi, Krupali MD; Kiprovski, Kiril MD

Author Information
American Journal of Physical Medicine & Rehabilitation: August 2022 - Volume 101 - Issue 8 - p e125-e127
doi: 10.1097/PHM.0000000000002018


A 28-yr-old previously healthy woman presented with 8 wks of left anterior shoulder and neck pain and weakness with shoulder abduction. She described the pain as constant, severity 4/10, with radiation to the left cervical spine. The symptoms started immediately postoperatively and remained persistent after a right shoulder arthroscopy for rotator cuff repair and subacromial decompression. The patient also described occasional paresthesias in all fingers of the left hand. She was a professional aerial dancer. Review of system was otherwise negative. The patient had the COVID-19 vaccine in the left deltoid days after the onset of her current symptoms. Medical history was unremarkable. Surgical history included bilateral hip labral repairs—the left 6 yrs prior and the right 1 yr prior. The patient has no history of connective tissue disorders in her or her family. She was only taking occasional nonsteroidal anti-inflammatories for pain.

Neurologic examination was notable for decreased bulk and atrophy of the left sternocleidomastoid and trapezius muscle. Strength examination was notable for 4/5 cervical rotation to the left and 4/5 on left shoulder abduction and shoulder flexion. She had full strength in her bilateral lower limbs and right upper limb. Left scapular lateral winging was noted during left shoulder abduction. Sensory examination was normal to light touch and pinprick in her bilateral upper and lower limbs. Biceps, triceps, and brachioradialis muscle stretch reflexes were 2+ in bilateral upper and lower extremities. Initial electrodiagnostic studies were obtained 8 wks after onset of symptoms. Electromyography (EMG) results are in Table 1. There were no abnormalities noted in the nerve conduction studies (Supplemental Tables 1–3, Supplemental Digital Content 1,

TABLE 1 - The left trapezius showed mild to moderate membrane instability and no motor unit action potentials could be elicited on volitional effort
Needle EMG Examination
Spontaneous Volitional MUAPs Recruitment
Muscle Insertional Fib PSW Fasc Dur Amp Poly Pattern Effort
L. Deltoid Normal None None None Normal Normal Few Full Max
L. Triceps brachii Normal None None None Normal Normal Few Full Max
L. Biceps brachii Normal None None None Normal Normal Few Full Max
L. Extensor digitorum communis Normal None None None Normal Normal Few Full Max
L. First dorsal interosseous Normal None None None Normal Normal Few Full Max
L. Flexor carpi radialis Normal None None None Normal Normal Few Full Max
L. Infraspinatus Normal None None None Normal Normal Few Full Max
L. Serratus posterior inferior Normal None None None Normal Normal Few Full Max
L. Supraspinatus Normal None None None Normal Normal Few Full Max
L. Trapezius (upper) Normal 1+ 2+ None No activity Max
L. Sternocleidomastoid Normal None 1+ None Normal Normal Few Reduced Max
The left SCM showed mild membrane instability, normal motor unit action potentials, and reduced recruitment. The other tested muscles were normal.
MUAP, motor unit action potentials; PSW, positive sharp waves; SCM, sternocleidomastoid.

Previous investigations include an magnetic resonance imaging cervical spine completed 7 wks after initial injury, which showed small central disc protrusion at C6-C7, which minimally indented the ventral thecal sac but did not cause any significant central canal or foraminal stenosis. Magnetic resonance imaging left shoulder also completed 7 wks after initial injury showed minimal edematous changes at the distal clavicle, compatible with her recent COVID vaccination.

Transitional Questions

What would be on your differential for shoulder weakness and pain? What about her physical examination seems significant? What follow-up tests, if any, would you order?


The differential diagnoses for shoulder weakness and pain includes brachial plexopathy, cervical radiculopathy, other proximal neuropathies, Parsonage-Turner syndrome, cervical facet or glenohumeral arthopathy, labral tear, rotator cuff tear, or shoulder instability.1 The trapezius elevates and retracts the scapula and rotates its lateral angle upward. Therefore, weakness can cause the scapula to be pulled downward and laterally due to unopposed action of the serratus anterior causing lateral winging. This results in poor articulation of the humeral head into the glenoid causing weakness in various shoulder movements, especially abduction and shoulder flexion. This misaligned shoulder may further worsen traction on the brachial plexus, thus causing secondary pain or paresthesias, which may delay diagnosis.2 In contrast, the serratus anterior is responsible for protracting and stabilizing the lower aspect of the scapula. Weakness of the serratus anterior results in the inferior border of the scapula moving closer to the spine resulting in medial winging.

Based on the physical examination and electrodiagnostic findings, the patient was diagnosed with partial severe spinal accessory nerve (SAN) palsy proximal to the branch for the sternocleidomastoid muscle. After her diagnosis, she was referred for an ultrasound of her left shoulder, which demonstrated a thickened SAN. Magnetic resonance imaging of soft tissue of the neck with and without contrast showed atrophy of the left trapezius and sternocleidomastoid and ruled out any compressive mass lesion (Fig. 1).

Amagnetic resonance imaging of the neck showing atrophy of the left versus right trapezius muscle and corresponding change in signal intensity.

Transitional Question

What would be your next step in treatment? What other nerves would you consider testing on EMG examination? What do you think is the etiology of this patient’s symptoms? What treatment options would you consider?

This study conforms to all Case Report guidelines and reports the required information accordingly (see Supplementary Checklist, Supplemental Digital Content 2,


During the EMG examination, studies of the lateral and medial antebrachial cutaneous, radial, and median nerves can help exclude brachial plexopathy or cervical radiculopathy. In addition, when conducting an EMG of an atrophied trapezius the examiner must be cautious not to pass through the muscle and accidently check a deeper muscle. Thus, during the EMG examination, it is important localize the muscle.2 Lastly, it is important to test the other shoulder stabilizing muscles to rule out other causes of shoulder weakness. In our patient, the supraspinatus, infraspinatus, deltoid, and serratus anterior muscle helped exclude other neuropathies.3,4

The etiology of this patient’s SAN nerve injury is unclear. Given her history of multiple orthopedic injuries requiring surgical intervention and her occupation as an aerial dancer, we hypothesize traction from cervical spine lateral flexion during dancing could have caused her SAN injury. Aerial dance involves yoga-inspired vertical and horizontal movements performed in a suspended state. Another possibility is injury during her right shoulder arthroscopy. During the procedure, the patient was placed in beach chair position with the right arm in a spider arm positioner for a duration of 2 hrs; however, the left arm and neck were placed in a neutral position. One limitation is we do not have the preoperative physical examination or EMG to confirm that this was not a previously preexisting condition. Lastly, an inflammatory etiology can be considered, however, less likely given the immediate onset of symptoms postoperatively.

Treatment options and prognosis for SAN palsy vary based on time from injury, severity, and etiology. Conservative treatment includes anti-inflammatories, physical therapy, and observation. The physical therapy prescription for SAN palsy should focus on scapular stabilization exercises, shoulder passive and active range of motion, and upper limb strengthening. Nonsteroidal anti-inflammatory drugs are preferred to control pain and inflammation. A short course of oral prednisone can also help reduce inflammation from nerve injury; however, they are not first line because of their adverse effect profile. Surgical referral should be considered if conservative measures fail or in cases of acute injury after surgical exploration. Surgical options include neurolysis, surgical repair with a graft or the Eden-Lange muscle transfer in which the trapezius is reconstructed from levator scapulae and rhomboid muscles.5

After the diagnosis, the patient was prescribed a short course of oral prednisone and physical therapy for scapular and upper limb strengthening for 6–8 wks. A follow-up EMG and nerve conduction study obtained 16 wks after initial injury revealed partial reinnervation of the trapezius and almost complete reinnervation of the sternocleidomastoid (Supplemental Table 4, Supplemental Digital Content 1, She tolerated physical therapy well and strength improved with only mild shoulder shrug weakness noted after 8 wks.


The spinal accessory nerve (cranial nerve XI) is a pure motor nerve derived from the C1-C4 cervical segments. The nerve ascends through the foramen magnum and exits the skull through the jugular foramen. It then innervates the sternocleidomastoid and transverses superficially across the posterior cervical triangle to innervate the trapezius.6

Intracranial causes of accessory nerve injury include primary tumors, such as schwannoma or metastases to the skull bases. Most commonly, the nerve is damaged in the area of the posterior cervical triangle of the neck, often due to a surgical procedure, such as a lymph node biopsy or radical neck dissection. Less common causes include compression, traction, lymph nodes, or blunt trauma. In our case, the sternocleidomastoid muscle was involved and thus injury was proximal to the posterior cervical triangle, which is rare, especially in this previously healthy female. Idiopathic accessory neuropathy can be associated with other mononeuropathies: it may be analogous to postoperative inflammatory brachial plexus neuropathy (acute brachial neuropathy) without evidence of direct surgical trauma.7,8

This case highlights the importance of a thorough neurological examination and timely electrodiagnostic studies in evaluating for possible SAN palsy in the setting of vague neurologic symptoms, shoulder weakness, and pain. A clinician’s focused examination should include close examination of the neck musculature, trapezius, sternocleidomastoid, and lateral scapular winging. Manual muscle testing may be unreliable in these cases as trapezius weakness can be masked by contributions from the levator scapulae and rhomboid. Proper timing of electrodiagnostic testing is vital in these patients—a test scheduled too early from symptom onset may lead to false negatives.2,9 Proximal SAN nerve palsies are rare but can be painful, disabling, and frustrating for the patient. Physicians should be aware of this phenomenon to ensure timely diagnosis and treatment for this injury.


1. Rosenthal MD: Differential diagnosis of shoulder pain followed by progressive weakness: a case report. J Spec Oper Med 2009;9:16–9
2. Preston DC, Shapiro BE: Electromyography and Neuromuscular Disorders: Clinical-Electrophysiologic-Ultrasound Correlations, 4th ed. China, Elsevier, 2021:494–7
3. Logigian EL, McInnes JM, Berger AR, et al.: Stretch-induced spinal accessory nerve palsy. Muscle Nerve 1988;11:146–50
4. Sergides NN, Nikolopoulos DD, Polyzois IG: Idiopathic spinal accessory nerve palsy. A case report. Orthop Traumatol Surg Res 2010;96:589–92
5. Teboul F, Bizot P, Kakkar R, et al.: Surgical management of trapezius palsy. J Bone Joint Surg Am 2005;87:1884–90
6. AlShareef S, Newton BW: Accessory Nerve Injury. StatPearls, 2021. Available at:
7. Stewart JD: Focal Peripheral Neuropathies, 2nd ed. New York, NY, Raven Press, 1993:86–9
8. Wiater JM, Bigliani LU: Spinal accessory nerve injury. Clin Orthop Relat Res 1999;368:5–16
9. Stino AM, Smith BE: Electrophysiology of cranial nerve testing: spinal accessory and hypoglossal nerves. J Clin Neurophysiol 2018;35:59–64

Accessory Nerve; Electrodiagnostic Studies; Palsy; Winging Scapula; Trapezius

Supplemental Digital Content

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