Paralabral cyst in spinoglenoid notch causing infraspinatus denervation
Presentation
Ultrasound found a complex ganglion cyst. Patient having pain on posterior aspect of shoulder. ?related.
Patient Data
A posterior labral tear.
A paralabral cyst extending medially into spinoglenoid notch and further superiorly into the suprascapular notch.
Moderate atrophy and bright PD signal in infraspinatus muscle. No signal abnormality in supraspinatus muscle.
Annotated images demonstrating suprascapular and spinoglenoid notches, signal and volume changes in infraspinatus muscle consistent with subacute atrophy, and posterior labral tear as the source of ganglion cyst.
Case Discussion
Supraspinatus and infraspinatus muscles are supplied by suprascapular nerve. The branch to supraspinatus nerve takes off at the level of suprascapular notch. In this case, isolated denervation changes in infraspinatus muscle suggest that the suprascapular nerve compression has distal to the nerve supply to supraspinatus muscle, probably at the level of spinoglenoid notch. Although the cyst extends to the suprascapular notch, there is no evidence of neural impingement at that site yet.
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