Investigations
As with most nerve entrapment neuropathies, the diagnosis is normally clinical.
MRI images display a high signal intensity in the affected nerve segment at the site of the compression because of the presence of oedema in the myelin sheath and perineurium.
MRI is also very good at detecting masses causing compression, and can detect muscle atrophy.
Electromyographic (EMG) studies may show signs of denervation of supraspinatus and infraspinatus, but are invasive and technique dependant.