Spinoglenoid notch cyst (SGNC)

Diagnosis
View images Images Click to Scroll Stacks
  • A spinoglenoid notch cyst (SGNC) is a ganglion cyst located in the spinoglenoid notch (between the lateral aspect of the scapular spine and the infraspinous fossa) that most commonly results from a superior labral tear
  • It typically occurs in 1) athletic adolescents with traumatic labral tears and 2) adults with chronic degenerative labral tears
  • The anatomy of the suprascapular nerve, anchored below the spinoglenoid ligament, renders it susceptible to compression by even small cysts in the vicinity
  • SGNCs range in size from small and unilocular to large and multiloculated
  • They are typically hypointense on T1 and hyperintense on T2-weighted MR images
  • Associated acute and subacute compressive suprascapular neuropathy manifests on MRI as hyperintensity of the infraspinatus muscle on T2-weighted images due to denervation myoedema
  • Chronic compressive suprascapular neuropathy manifests as infraspinatus atrophy and hyperintense fatty infiltration on T1-weighted images
  • Proton density fat saturated or T2 fat saturated sequences maximize conspicuity, detection and characterization of paralabral cysts
  • Paralabral cysts are indicative of a labral tear until proven otherwise
  • SGNCs cause suprascapular neuropathy affecting only the infraspinatus muscle, while supraspinatus notch cysts cause more proximal suprascapular neuropathy affecting both the supraspinatus and infraspinatus muscles
  • Labral tear with paralabral cysts may clinically mimic a rotator cuff tear
  1. Pomeranz SJ. Suprascapular Nerve Syndrome. In: Orthopaedic and Sports Medicine MRI: MRI of entrapment neuropathies. MRI-EFI Publications; 2011:14-17
  2. Stoller DW, Tirman PFJ et al. Labral Cyst, Shoulder. In: Diagnostic Imaging: Orthopedics. Amirsys; 2004:46-49
  3. Yanny S, Toms AP. MRI Patterns of Denervation Around the Shoulder. AJR 2010; 195:157-163