Chief Complaint: Intense Left Shoulder Pain

Parsonage-Turner syndrome (PTS), or neuralgia amyotrophy, is a rare condition that affects mainly the lower motor neurons of the brachial plexus or individual nerves or nerve branches.^1,2 The cause is unknown. The typical presentation is sudden, often excruciating neck and arm pain followed by marked muscle weakness and wasting of the shoulder girdle and upper arm. In this article, we describe the case of a 38-year-old white woman who presented with a complaint of acute left shoulder and neck pain.

CASE PRESENTATION
History of present illness
The woman stated that her symptoms had begun suddenly while she was hospitalized during the delivery of her fourth child. Her prenatal course had been uneventful, and she had had an uncomplicated labor with a vaginal delivery.

During active labor, the woman began noticing pain in her neck and left shoulder. The pain was intense, rating 9/10 on a numerical pain intensity scale. An orthopedic consultation was not immediately available in the hospital. The patient had a history of intermittent left-sided neck and shoulder pain, which historically responded well to rest and oral corticosteroids. The working diagnosis was recurrent cervical radiculitis. Oral corticosteroids were prescribed.

The patient presented to the clinic 1 week postpartum with a 75% reduction in pain. She described the discomfort as a deep ache in the left side of her neck, anterior chest wall, and proximal left arm. The patient then described functional weakness in her left upper extremity, with difficulty in holding her baby and performing other routine activities of daily living, including washing her hair and holding kitchen utensils.

Medical history
The patient's past medical history included well-controlled hypothyroidism. Her past surgical history involved a partial thyroidectomy 1 1/2 years earlier. The patient's family history was noncontributory. Her social history was as follows: 38-year-old active woman, stay-at-home mother, with 4 previous successful and uncomplicated pregnancies.

Physical examinationNeck. The patient had limited range of motion on the left side compared with the right. Her Spurling sign-cervical rotation and extension in an attempt to narrow the foraminal outlet and reproduce pain from a cervical root lesion-was equivocal on the left, producing local pain only, and negative on the right. She had full flexion and extension. No palpable tenderness in the cervical spinous processes or paraspinal muscles was noted.

Left upper extremity. Examination of the patient's arm and shoulder demonstrated considerable weakness to forward flexion and external rotation with the elbow at her side (strength 3/5, compared with 5/5 on the contralateral side). Internal rotation strength, abduction, and flexion and extension of the wrist were normal. Biceps strength was normal bilaterally.

In a neurosensory examination, the patient's sensation was intact to light touch and temperature, with the exception of a mild decreased appreciation of light touch roughly in the distribution of the musculocutaneous nerve. She had good distal pulses and no unusual skin changes. No significant atrophy was noted.

Differential diagnosis
The differential diagnosis includes cervical radiculopathy, rotator cuff disease, thoracic outlet syndrome, and neoplastic brachial plexopathy. Other conditions to be considered in the differential are impingement syndrome, PTS, and mononeuritis multiplex.

Plan
An MRI scan of the patient's cervical spine was obtained to rule out herniated nucleus pulposus with resultant cervical radiculopathy. Because of the resolution of her pain symptoms and her wish to breastfeed, analgesics were discontinued.

The MRI scan of the patient's cervical spine demonstrated moderate multilevel degenerative disk changes at C3-4 through C6-7, with broad-based disk protrusions and uncovertebral osteophytes that resulted in mild effacement of the ventral thecal sac without high-grade central spinal canal stenosis or spinal cord compression. There was no foraminal stenosis or disk herniation.

Working diagnosis
Given the patient's pain and weakness pattern without evidence of cervical neural compression, the diagnosis of PTS was rendered. A prescription for physical therapy was given with the goal of restoring strength and function. An electromyograph was obtained 4 weeks after symptom onset.

Electrodiagnostic study
Membrane instability and neuropathic motor unit recruitment were noted in the left infraspinatus, biceps brachii, triceps brachii, and pronator teres. The deltoid, brachioradialis, and extensor digitorum muscles were normal, displaying a “hit and skip” pattern to the neuropathy that did not follow a myotome pattern or specific brachial plexus pattern. The final diagnosis was left neuralgia amyotrophy, or PTS.

OUTCOME
The patient continued physical therapy for 6 weeks. At week 3, her pain had improved greatly, but weakness in her left upper extremity persisted and atrophy of the involved muscles was becoming more apparent.

The pain waxed and waned, and at one point a return to analgesic therapy was needed. Secondary soft tissue dysfunctions developed, including a myofascial pain pattern and rotator cuff tendinitis caused by compensatory movement patterns. An MRI scan of the brachial plexus was recommended but was deferred by the patient. Symptoms were tolerable at week 9 and never returned to the original levels.

At 12 weeks after the onset of symptoms, the patient regained about 80% of her strength. She had minimal to no pain and was showing steady improvement.

COMMENT
Of interest in this case, there is a correlation with onset during the perinatal period. The prognosis for patients with PTS is generally good. Recovery of strength and sensation usually begins spontaneously, as early as 1 month after the onset of symptoms; about 75% of patients have complete recovery within 2 years.³

References:

References

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Sathasivam S, Lecky B, Manohar R, Selvan A. Neuralgic amyotrophy.

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2008;90B:550-553.

2.

Park P, Lewandrowski KU, Ramnath S, Benzel EC. Brachial neuritis: an under-recognized cause of upper extremity paresis after cervical decompression surgery.

Spine (Phila Pa 1976).

2007;32:E640-E644.

3.

McCarty EC, Tsairis P, Warren RF. Brachial neuritis.

Clin Orthop Relat Res.

1999;368:37-43.