Review Question - QID 216790

This pitcher likely has a SLAP tear of his labrum which has lead to a paralabral cyst extending into the spinoglenoid notch and is compressing the suprascapular nerve, affecting the infraspinatus muscle.

The suprascapular nerve is formed by the C5/C6 nerve roots and innervates the supraspinatus and infraspinatus muscles. It first crosses under the transverse scapular ligament and impingement at this location leads to denervation of both the supraspinatus and infraspinatus. As the nerve progresses through its course, it traverses the spinoglenoid notch to innervate the infraspinatus muscle. Therefore, compression at the spinoglenoid notch only affects the infraspinatus. The most common etiology of spinoglenoid notch compression is a paralabral cyst associated with a labral tear. Patients describe posterior shoulder pain and will have weakness with external rotation with the arm by the side when the infraspinatus is affected. MRI is useful in identification of these lesions and surgical decompression is usually required in cases of mechanical impingement.

Aval et al. review different neurovascular conditions sustained in the shoulders of athletes. They mention a differential diagnosis of thoracic outlet syndrome, quadrilateral space syndrome, complex regional pain syndrome and suprascapular nerve palsy. They expand on these by describing the history, physical examination and treatment of these different conditions.

Piasecki et al review suprascapular neuropathies, including their presentation and management. They note both intrinsic and extrinsic causes of compression are possible along the nerve’s path and diagnosis is based on history, examination, imaging and electrodiagnostic studies. Arthroscopic or open methods of decompression both tend to provide benefits in pain relief and functional improvement, with arthroscopic management having the benefit of concomitantly addressing other intra-articular pathology.

Safran et al reviewed injuries to the suprascapular and axillary nerves, noting that they are becoming increasingly recognized. They emphasize efficiency in diagnosis and treatment to prevent any long-term complications. They further detail the potential nonoperative and surgical options regarding nerve decompression.

Figure A demonstrates a coronal PD MRI sequence demonstrating a paralabral cyst causing compression in the spinoglenoid notch.

Incorrect Answers:
Answer 1: The supraspinatus would not be affected in the case of a spinoglenoid notch cyst, as the innervation of the supraspinatus is proximal to the spinoglenoid notch.
Answers 3,4: Despite potentially contributing to external rotation weakness, the teres minor and deltoid innervations would be affected by injury or compression to the axillary nerve. One example would be quadrilateral space syndrome.
Answer 5: The serratus anterior would be affected by damage to the long thoracic nerve which is not compressed in the case of a spinoglenoid notch cyst.