Somewhat Interesting Case of the Month: Infrascapular Neuropathy with Paralabral Cyst
This is a 50 something year old, left handed, otherwise healthy man who builds houses for a living. He came to see me complaining of a "dent" in his left shoulder, which seemed to have developed fairly suddenly. He had not noticed any pain, numbness, weakness or recent injury. I hadn't ever seen this before, but my initial impression would have been an acute rotator cuff tear, except that there was no pain or tenderness and he had full range of motion. On exam, he did not have any sensory deficit but he did have some weakness with external rotation of the arm. I felt that this might be atrophy of the infraspinatus muscle due nerve damage, but had to get a book to review the anatomy for the most likely location of the lesion. Meanwhile I also obtained a chest x-ray (PA, Lateral, and Apical Lordotic views) which did not reveal any tumors. After review I felt his diagnosis was infraspinatus syndrome, which apparently most commonly seen in volleyball players (it is sometimes called volleyball shoulder) due to damage to the suprascapular nerve from overhand serving, blocking and spiking. This made sense to me because his job involves doing a lot of overhead work. I sent him to a physiatrist thinking he may need nerve conduction studies in addition to an MRI, however the MRI was all that was needed for the diagnosis. I could not get the actual MRI to show, because it has been archived electronically, and is now unavailable to me, but here is part of the report: This patient has a large cyst in the spinoglenoid notch, up to 5 cm in length and up to 1.9 cm in height and width. Some infraspinatus atrophy and abnormal signal intensity is present. This appears to communicate with a cyst in the posterior labrum. This is evidently due to chronic tear in this location. The rotator cuff showed some abnormal signal intensity consistent with some impingement.
Here is some information on infraspinatus syndrome from emedicine.com:
Infraspinatus syndrome is defined as a condition of frequently painless atrophy of the infraspinatus muscle caused by suprascapular neuropathy. The syndrome typically causes symptoms that mimic those of rotator cuff tendinopathy, and the diagnosis may be overlooked until the symptomatic athlete fails to respond to a traditional rotator cuff treatment program..The prevalence of infraspinatus syndrome appears to be highest among volleyball players. Studies have reported that 13-45% of elite volleyball athletes have signs of suprascapular neuropathy. This observation lends credence to the term "volleyball shoulder."
Here is an excellent outlined breakdown of suprascapular neuropathy with a diagram:
Here is an MRI of a paralabral cyst which is similar to the one in my case (see case #5)
The last time I heard about my patient, the physiatrist was going to send him either to a local orthopedist or a shoulder specialist for surgical intervention.
Here is a link to some good information on paralabral cysts associated with posterior labral tears. This author refers to the suprascapular nerve as the the infrascapular nerve once it passes through the spinoglenoid notch, which seems to make sense.