The patient was referred for subtle weakness of the left arm, with no pain nor sensory impairment.
The patient presented with a subtle weakness of the left arm, impossibility for the active abduction. No sensory impairment and no pain were present at the moment of the admission. He had had recent flu vaccination. He was first evaluated with cranial and cervical MRI. The cranial exam was normal and the cervical study only showed spondylosis with no medullar lesion. We performed a shoulder MRI exam, with axial spin-echo T1-weighted sequence, coronal and sagital fast spin-echo T2-weighted sequences with fat saturation. The study showed an increased signal intensity of the supraspinatus, infraspinatus and teres minor muscles related to neurogenic edema due to acute/subacute denervation. The MRI findings were consistent with PTS. It was confirmed with electrophysiologic exam.
PTS, also known as idiopathic inflammatory brachial plexitis or neuralgic amyotrophy, is an uncommonly diagnosed disorder of the shoulder girdle and brachial plexus; it usually causes intense acute pain and progressive neuromuscular weakness. The incidence has been estimated at approximately 1.64 in 100.000, with a peak rate between the third and the fifth decades and a slight male predominance. Although different precipitating factors, such as infection, trauma, surgery, immunization, and autoimmune mechanisms, have been suspected in the occurrence of PTS, the etiology remains unknown. Prognosis is generally favorable, with about 75% of complete recovery within 2 years. Although lack of pain is extremely uncommon in PTS, it has been reported in the original series of Parsonage and Turner. Potential causes of denervation are numerous, including: (1)discogenic nerve root compression, (2)spinal cord injury, (3)infiltrative tumor of the nerve root or brachial plexus such as Pancoast-Tobias syndrome, (4)poliomyelitis, (5)amyotrophic lateral sclerosis, (6)peripheral nerve injury or compression and (7)idiophatic. In our case, MRI didn’t show any cyst or soft tissue mass at the spinoglenoid notch that compresses the suprascapular nerve. No spinal cord lesion was found. There was no evidence of infection. No tumoral disease was found. In this way, the diagnosis of PTS was suggested prior to electromyography. MR imaging is useful in detecting and characterizing denervation atrophy and neurogenic edema in shoulder muscles. MR imaging can provide additional information to electrophysiologic studies by identifying morphologic causes for shoulder pain and atrophy. Some authors have described the utility of whole body MRI in the diagnosis of PTS.
Parsonage-Turner Syndrome.
Based on the provided shoulder MRI images, certain muscles around the left shoulder joint (including the supraspinatus and infraspinatus) show increased signal on T2-weighted sequences, suggesting possible neurogenic edema or muscle degeneration. No obvious tumor lesions, cystic changes, or noticeable compressive lesions are observed. There is also no clear evidence of spinal cord or nerve root lesions on the images. No significant soft tissue mass or localized bone destruction is noted within the surrounding soft tissue.
Combining the imaging findings with the patient’s clinical presentation—no significant pain but weakness in the left upper limb—the possible diagnoses or differential diagnoses include:
Considering the patient’s age (50 years), clinical presentation (mild weakness in the left upper limb without significant pain or sensory disturbance), MRI findings indicating neurogenic muscle abnormalities, and the exclusion of cervical spine or tumorous lesions, the most likely diagnosis is:
Parsonage-Turner Syndrome (PTS with minimal or no pain).
Further confirmation can be achieved through electrophysiological tests (EMG and nerve conduction studies) to determine the degree of nerve involvement. If unexplained symptoms worsen or suspicious imaging findings arise, additional full-body or localized contrast-enhanced MRI could be considered for further evaluation.
Treatment Strategies:
Rehabilitation and Exercise Prescription Example (FITT-VP Principle):
Daily activities should avoid excessive stretching or sudden force to prevent secondary injuries. If the patient experiences marked pain or worsening weakness, exercises should be stopped, and medical advice sought promptly.
Disclaimer:
This report is provided solely as a reference based on the current medical history and imaging data. It does not replace an in-person evaluation or professional medical opinion. Specific diagnostic and treatment plans should be determined by a professional medical team, in conjunction with clinical exams, laboratory findings, and electrophysiological results.
Parsonage-Turner Syndrome.
