QUIZ: No. 13, 12/04/2026

Diagnosis: Spino-glenoid notch cyst with suprascapular nerve compression causing infraspinatus denervation myoedema.

Findings: Well-defined multilobulated T2 hyperintense cystic lesion located at the spinoglenoid notch. The lesion shows fluid signal intensity without solid components. It is seen along the expected course of the suprascapular nerve (distal branch). There is T2 hyperintense signal change noted involving the infraspinatus muscle. No aggressive features, bone erosion, or soft tissue mass noted.

Discussion

Ø  Spinoglenoid notch cysts are typically paralabral cysts that arise secondary to labral tears, most commonly involving the posterior labrum.

Ø  They occur due to a one-way valve mechanism, where synovial fluid extravasates through the labral defect and accumulates, forming a cyst.

Ø  The spinoglenoid notch transmits the distal branch of the suprascapular nerve, which supplies the infraspinatus muscle. Compression at this location results in isolated infraspinatus involvement, distinguishing it from suprascapular notch lesions.

Ø  MRI is the modality of choice and typically shows a well-defined fluid signal lesion adjacent to the labrum, often multiloculated. Identification of an associated labral tear is crucial.

Ø  Denervation changes, if present, follow a sequence:

Early: muscle edema (T2 hyperintensity)

Late: fatty atrophy (T1 hyperintensity, volume loss)

Teaching pearl:

Spinoglenoid notch lesion → isolated infraspinatus involvement