Lennard Funk, 2011
Paralabral cysts are swellings that arise around the socket of the shoulder joint (glenoid). They are pockets of joint fluid that develop outside of the joint under tears of the labrum. These are also known as ganglia (or a ganglion). These may occur anywhere around the glenoid.
The cysts can be diagnosed on an MRI scan, or MR Arthrogram. An MR Arthrogram is more sensitive in detecting the associated labral tear also.
Posterior paralabral cyst with labral tear on MR Arthrogram:
Often the cysts themselves don't cause any pain, but the labral tears can cause pain. Treatment will involve repair of the labral tear and drainage of the cyst. This is usually done by arthroscopy (Keyhole). For more details on the labral repair click here.
The cysts may become very large and can press on some of the important nerves around the shoulder. This can cause pain and also weakness of the muscles supplied by the nerve. The commonest nerve affected is the suprascapular nerve. The suprascapular nerve can be compressed at the spinoglenoid notch with a posterior labral tear (reverse Bankar tear) or at the suprascapular notch with a SLAP tear. This can lead to a suprascapular nerve palsy.
Posterior paralabral cyst pressing on the suprascapular nerve at the spinoglenoid notch, under the spinoglenoid ligament:
Posterior paralabral cyst causing compression of suprascapular nerve with wasting and fluid oedema in the infraspinatus muscle (within green circle):
Treatment for paralabral cysts causing nerve compression involves arthroscopic repair of the labral tear, as well as decompression of the nerve and drainage of the cyst.
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- Sanders, T. G. and P. F. Tirman (1999). "Paralabral cyst: an unusual cause of quadrilateral space syndrome." Arthroscopy : the journal of arthroscopic & related surgery : official publication of the Arthroscopy Association of North America and the International Arthroscopy Association 15(6): 632-637.
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