A 45-year-old female patient presented with pain, numbness and weakness involving the right shoulder and arm for the past 6 months. The left upper and bilateral lower limbs were normal. No history of trauma or antecedent history of infection was elicited.
The supraspinatus, infraspinatus, subscapularis, teres minor and deltoid muscles show reduced muscle bulk and abnormal T1W hyperintense signal suggestive of fatty replacement. The tendons of these muscles retain their normal hypointense signal. The pectoralis muscles and the muscles of the upper arm show normal muscle bulk and signal. No definite rotator cuff tendon tears nor features of impingement were seen. No abnormality was noted in the suprascapular notch, spinoglenoid notch and the quadrilateral space (not shown) where possible compression of the suprascapular nerve and axillary nerve may occur. Imaging of the cervical spine revealed no significant spinal cord compression or neural foraminal narrowing.
Parsonage Turner syndrome (PTS) is characterised by severe pain and weakness involving at least one muscle in the shoulder. This condition has also been otherwise described including ‘acute brachial neuritis’ and neuralgic amyotrophy [1, 2]. It often mimics other common conditions like cervical spondylosis, rotator cuff pathology and shoulder impingement, which may result in delayed diagnosis and inappropriate treatment [1]. Infectious and immunologic processes including prior viral infections and vaccination are thought to play a role in the pathogenesis of brachial neuritis [1, 2].
The common clinical features in PTS include severe sudden-onset pain and weakness. Sensory symptoms like hypaesthesia and paraesthesia and rarely autonomic symptoms like skin changes, nail changes and increased sweating in affected areas have also been described [3]. The disorder is usually self-limiting with most patients showing varying degrees of improvement months to years after onset [1].
MRI is the ideal imaging modality for visualising the muscle changes secondary to denervation caused by brachial neuritis. Undesrstanding of the innervation of the various muscles around the shoulder is essential in assessing patterns of involvement on MRI. The supraspinatus and infraspinatus muscles are supplied by the suprascapular nerve, the subscapularis muscle by the subscapular nerve and the deltoid and teres minor muscles by the axillary nerve. The commonest nerve involved is the suprascapular nerve with the supraspinatus and infraspinatus muscles being the most commonly-affected muscles [1, 2]. The signal changes occurring within muscles on MRI vary based on the phase of the disease [2]. A diffuse increase in T2W signal within muscles is seen in the acute phase of denervation. In the subacute and chronic phases changes of atrophy and fatty infiltration occur, visualised as increased signal on T1W images.
Our case showed reduced muscle bulk and significant fatty replacement of the supraspinatus, infraspinatus, subscapularis, teres minor and deltoid muscles corresponding to involvement of the suprascapular, subscapular and axillary nerves. Involvement of these three nerves was described in one case in the study by Gaskin and Helms [1]. Our case showed no abnormality in the region of the suprascapular/ spinoglenoid notch or quadrilateral space (not shown) where possible compression of the suprascapular and axillary nerve may occur. The cervical spine showed no significant abnormality. No history of chronic disuse of right shoulder prior to onset of symptoms was elicited. The chronic nature of the patient’s symptoms coupled with the characteristic imaging findings favoured the diagnosis of chronic phase of PTS.
Chronic phase of Parsonage Turner syndrome
The patient is a 45-year-old female complaining of right shoulder and upper arm pain, numbness, and weakness for 6 months. Imaging (shoulder MRI) primarily shows:
Based on the sudden onset of severe shoulder pain followed by muscle weakness and atrophy, together with the imaging findings, possible diagnoses or differential diagnoses include:
Based on the patient’s symptoms (acute onset of pain followed by muscle weakness, atrophy, and sensory disturbances), imaging characteristics (neurogenic atrophy of multiple shoulder muscles, fatty infiltration, no evident local compression or cervical radiculopathy), and history (around six months of persistent course, not due to trauma or chronic disuse), the most likely diagnosis is:
Chronic phase Parsonage-Turner Syndrome (late stage of acute brachial neuritis).
After confirming the diagnosis, the following treatment and rehabilitation plan may be considered:
Disclaimer: This report is for medical analysis reference only and does not replace in-person clinical consultation or professional medical advice. Specific treatment plans should be based on the patient’s actual situation and be determined by qualified clinical physicians.
Chronic phase of Parsonage Turner syndrome
