*2.5.2.1 Suprascapular nerve compression syndrome*

**Anatomy:** The suprascapular nerve is a peripheral nerve with motor and sensory fibers that originates from the C5-C6 nerve roots and leaves the upper trunk of the brachial plexus. After passing through the posterior cervical triangle, it runs laterally, deep to trapezius and omohyoid, and enters the supraspinous fossa through the suprascapular notch, which is a fibro-osseous tunnel bridged by the transverse scapular ligament. The suprascapular nerve gives off two branches in the suprascapular fossa. One of these branches is distributed to the supraspinatus muscle, the other to the upper aspect of the shoulder joint. The nerve passes through the lateral part of the scapular spine and reaches the spino-glenoid notch. It reaches the infraspinatus fossa by passing through this notch. It supplies the infraspinatus muscle and posterior aspect of the glenohumeral joint (**Figure 4**) [8, 16, 26].

**Description:** This clinical condition is characterized by the suprascapular nerve compression at the suprascapular notch or at the spino-glenoid notch [26].

**Causes:** Different pathologies play a role in the compression of the suprascapular nerve at the suprascapular notch and/or spino-glenoid notch. The reasons causing compression are grouped in 2 subgroups, primary and secondary. Primary reason is dynamic entrapment of the nerve. Causes such as space occupying lesions (neoplasm, ganglion cyst, ossified scapular ligament), traumatic conditions (scapula fractures, shoulder dislocation, massive cuff tear, distractive trauma, penetrating trauma), post traumatic disorders (hematomas, heterotopic ossification, hypertiroidisim) and systematic disorder are classified as secondary. In addition, hormonal alterations or iatrogenic conditions (arthroscopic tear cuff repair, Latarjet procedure) can also cause suprascapular neuropathy [8, 26, 27]. If suprascapular nerve entrapment occurs around the suprascapular notch, both supraspinatus and infraspinatus muscles; if the spino-glenoid occurs around the notch, only the infraspinatus muscle is affected [8]. Shoulder pain associated with suprascapular neuropathy is seen as secondary to trauma in people involved in sports, and repetitive stretching of the nerve, especially in overhead volleyball players, baseball players, basketball players and dancers, is shown as an etiological factor [26].

**Clinical features:** When the suprascapular nerve is entrapped at the suprascapular notch, both supraspinatus and infraspinatus muscles may undergo denervation. When the nerve is compressed at the spino-glenoid notch, denervation is limited to the infraspinatus muscle [8, 26]. Suprascapular neuropathy presents with

#### **Figure 4.**

*The schematic drawing of entrapment sites in suprascapular nerve compression syndrome (entrapment sites are shown with a black arrow. A: The suprascapular notch, B: The spino-glenoid notch. SSN: Suprascapular nerve, SS: Supraspinatus muscle, IS: Infraspinatus muscle).*

dull and poorly localized pain, often localized lateral and posterior to the shoulder. Patients have difficulty in raising the arm. Particularly the shoulder external rotation and abduction is weakened on the affected side and is often confused with cervical disc pathologies. If the impingement is in the suprascapular notch, the pain is more pronounced and the clinical noisier. Pain can spread to the neck and anterior rib cage wall. In addition, the suprascapular nerve is a purely motor nerve. So, no sensory loss is observed [8, 26–28].
