Sudden onset of intense shoulder pain followed by muscle weakness a few weeks later.
The patient complained of sudden onset of intense shoulder pain, with no previous history of shoulder pain or trauma. The patient was otherwise healthy.
The first MR study was performed shortly thereafter in a 1.5-T magnet with a dedicated shoulder coil. We performed the routine protocol for shoulder pain, that included T1-weighted (T1W) and fat-saturated T2-weighted sequences (T2W-FatSat) in the coronal plane, T2W in the sagittal plane, and T1W and gradient echo T2*-weighted sequences in the axial plane. No significant abnormalities were found on this first MR study.
Three months later, the patient presented with less pain, but with increased muscle weakness and unable to abduct the right upper limb. We performed a second MR study with the same protocol. This time, MR showed diffuse oedema in the infraspinatus and supraspinatus muscles, with no loss of volume and no oedema in the remaining shoulder girdle muscles, particularly, there was no oedema in the subscapularis and teres minor muscles. No mass or cyst could be found in the spinoglenoid notch or, for that matter, any lesion that could compress the suprascapular nerve.
Parsonage-Turner syndrome, also known as “acute idiopathic brachial neuritis,” is a painful non-traumatic disorder involving the shoulder girdle. It is relatively rare and it appears to affect males more than females, with two incidence peaks in patients in their third and seventh decades [1]. The exact aetiology has not been established, but viral and immunological causes have been considered [2]. The long thoracic, suprascapular, and axillary nerves - individually or combined - reportedly have been the most commonly affected nerves [3].
Patients with Parsonage-Turner syndrome (PTS) typically present with sudden onset of shoulder pain or weakness (or both) of the shoulder girdle musculature. Typically, the pain subsides over a period of weeks to months, but the weakness may worsen during this time. The long-term prognosis is good. The disorder is self-limited, with gradual recovery usually occurring within months.
Clinically, establishing the diagnosis may be challenging because symptoms are nonspecific and may mimic other shoulder girdle disorders, such as labral tear with associated paralabral cyst, rotator cuff tear, impingement and adhesive capsulitis.
MR is the imaging technique of choice in patients with shoulder pain and weakness and provides the most comprehensive evaluation of the shoulder girdle because of its multiplanar imaging capability and superior soft-tissue contrast. Familiarity with the MR features of Parsonage-Turner syndrome is critical for radiologists because they may be the first to suggest the diagnosis [4].
MR imaging excludes other shoulder disorders such as impingement syndrome, rotator cuff tears, and ganglions impinging on the suprascapular nerve, many of which may need surgical treatment [5]. Cervical spine sources of brachial plexus compression often must be excluded by inspecting plain radiographs or MR images. It is distinctly unusual, however, for cervical spine foraminal stenosis to cause selective suprascapular nerve involvement [4] as in our patient.
MR imaging plays a valuable role in demonstrating what is probably neurogenic oedema and atrophy that involve the musculature of the shoulder [5]. The diagnosis in our case report was made by identifying, in the second MR examination, a pattern of muscular high signal intensity on fluid-sensitive sequences that was consistent with involvement of the suprascapular nerve. There were no findings sugesting nerve entrapments or compression on any of the two MR studies performed on this patient.
In the first MR all shoulder muscle appeared normal. We speculate that MR findings might be negative when the examinations are performed too early following acute denervation [4].
Parsonage–Turner syndrome.
In this patient’s shoulder MRI, mild abnormal signals can be observed in the region innervated by the suprascapular nerve (mainly including the supraspinatus and infraspinatus muscles). Specifically, in the second MRI examination, high signal changes are shown on T2 or other fluid-sensitive sequences, suggesting neurogenic edema or early muscle atrophy. The first shoulder MRI did not reveal any significant abnormalities, possibly because it was performed too early, before imaging changes had appeared. No obvious rotator cuff tear, degenerative injuries, or clear nerve entrapment/compressive lesion were detected on the images. Additionally, an atypical cervical foraminal stenosis is unlikely to selectively affect only the suprascapular nerve. Overall, the MRI findings are consistent with neurogenic damage.
Considering the sudden onset of non-traumatic shoulder pain and weakness in the shoulder girdle muscles, along with neurogenic edema indicated on the second MRI and the exclusion of other significant shoulder or cervical spinal structural pathologies, the most likely diagnosis is:
Parsonage-Turner Syndrome (Acute Idiopathic Brachial Plexus Neuritis).
Treatment Strategy:
Rehabilitation/Exercise Prescription Recommendations (FITT-VP Principle):
Throughout rehabilitation, closely monitor the patient’s pain level and joint range of motion. If intolerance to treatment or worsening of symptoms occurs, promptly reassess and adjust the plan.
Disclaimer: This report is provided for reference only and cannot replace in-person medical consultations or professional opinions. If you have any questions or if your condition changes, please seek medical attention promptly.
Parsonage–Turner syndrome.
