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Age / Sex : /
Age / Sex : 42 /male
Chief complaint : Shoulder weakness
1) What is your impression?
Two weeks later, you can see the final diagnosis with a brief discussion of this case.
* Send Application Answers to Ja-Young Choi, MD (drchoi01@radiol.snu.ac.kr).
Courtesy : Min Hee Lee, MD. Kangbuk Samsung Hospital, Sungkyunkwan university School of medicine
Diagnosis: suprascapular entrapment by ganglion cyst
Discussion
Findings:
A large cyst is in superior glenoid extending posteriorly into the spinoglenoid notch (from 12 to 9 o’clock direction). Diffuse increased signal is seen in the infraspinatus muscle without volume atrophy.
Diagnosis:
Suprascapular nerve entrapment (infraspinatus muscle denervation on EMG) Discussion: Suprascapular nerve originated from upper trunk of brachial plexus (from C5, 6) traverses the suprascapular notch beneath the superior transverse scapular ligament, sending off some braches including one to the supraspinatus muscle. And it continues to pass spinoglenoid notch to enter the infraspinatus fossa, under the inferior transverse scapular ligament (present in 15-85%). Typical causes of suprascapular nerve palsy include acute direct injury, iatrogenic insults, mass lesions, and repetitive compressive traction or friction forces. Large paraglenoid cysts may compress the suprascapular or axillary nerve and cause shoulder weakness through denervation of external rotator muscles. On MR imaging, muscle denervation is indiated by diffuse abnormal signal intensity in the affected muscle with or without muscle atrophy. With clinical recovery of motor function, signal intensity returns to normal.
References:
1. Internal derangement of joints. 2nd ed. Resnick , Kang and Pretterklieder
2. Tung GA, Entizian D, Stern JB, Green A. MR imaging and MR arthrography of paraglenoid labral cysts. AJR 2000;174:1707-1715
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