Parsonage-Turner syndrome

Parsonage Turner syndrome is an acute idiopathic brachial neuritis.

Epidemiology

There is male predominance (M:F 2:1 to 11.5:1) ¹. Patients from 3 months to 85 years old has been reported but majority are between 3rd to 7th decade of life.

Clinical presentation

Presentation is typically quite sudden with onset of painful shoulder girdle and gradual weakness. Symptoms are however non specific, and can mimic numerous other much more common conditions such as cervical spondylosis, labral tear with paralabral cyst and other suprascapular notch masses, rotator cuff deficiency, shoulder impingement, calcific tendonitis and adhesive capsulitis ^1-2.

The findings are unilateral in two thirds of cases.

Diagnosis is made with a combination of history, EMG (which demonstrates denervation changes, especially of the suprascapular nerve) and imaging. 

Pathology

The aetiology is uncertain, although localised infectious (viral) or immunological process is suspected. In almost all cases (97%) the suprascapular nerve is involved, and is the only nerve involved in 50% of cases ². The axillary nerve, and subscapular nerve are also sometimes involved, either in combination or alone. 

As a result the most frequently involved muscles are supraspinatus and infraspinatus (innervated by suprascapular nerve) followed by deltoid (innervated by axillary nerve). 

Bilateral involvement is reported .

Radiographic features

MRI

The most striking feature on MRI are denervation changes in muscles. Initially the muscle appears normal. Over the next few weeks high T2 signal develops. Gradually, especially in patients with a protracted course, atrophy and fatty infiltration will develop with increase in T1 signal and decreased muscle bulk. 

Treatment and prognosis

The condition is typically self limiting with supportive therapy only being required. Weakness may persist for many years, although 90% of patients will have noted an excellent recovery by 3 years ².

History and etymology

This syndrome was first described in 1943 by Spillane ⁴, but popularised with a larger series in 1948 by Parsonage and Turner ³.

• Maurice John Parsonage (?), Neurologist: UK
• John W. Aldren Aldren Turner (?), Neurologist: London, UK  (not the same Turner as Turner syndrome)

Differential diagnosis

Differential diagnosis on MR findings includes ^1-2:

• disuse atrophy of shoulder girdle muscles
• quadrilateral space syndrome
• other entrapment syndromes around shoulder
  • mass in the suprascapular notch (e.g. ganglion)
• trauma