Suprascapular Nerve

Normal Anatomy

The suprascapular nerve originates from the upper trunk of the brachial plexus, receiving fibers from C5 and C6 nerve roots. The nerve innervates the supraspinatus and infraspinatus muscles and provides sensation to the gle-nohumeral and acromioclavicular joints. After traversing the supraclavicular fossa, the suprascapular nerve, with its accompanying vein and artery, enters the suprascapular notch, making a sharp turn around the scapular spine. There the nerve travels within scapular notch or scapular incisura—a fibro-osseous tunnel bridged superiorly by the scapular ligament. The suprascapular vessels travel above the notch. At the scapular notch, the suprascapular nerve divides into the supraspinatus and infraspinatus nerves. In about 50% of the population, the infraspinatus nerve travels within a second more inferior and posterior tunnel roofed by the spinoglenoid ligament [1,11].

MRI Anatomy

The suprascapular nerve and its accompanying vessels, well-outlined by fat, are initially best identified on oblique coronal T1-weighted images within the suprascapular notch, at the junction of the glenoid with the scapular neck, just medial to the superior glenoid rim (Fig. 1A). As the suprascapular neuro-vascular bundle enters the spinoglenoid notch, it is better seen on axial MR images (Fig. 1B). A prominent suprascapular vein, which in some instances is responsible for compressive neuropathy, is not infrequently noted in the vicinity of the nerve.

Pathology: Suprascapular Nerve Syndrome

The clinical and imaging manifestations of entrapment neuropathies of the suprascapular nerve and its branches vary depending on the location of compression. Entrapment of the suprascapular nerve at the scapular incisura results in supraspinatus and infraspinatus muscle denervation, whereas distal entrapment at the spinoglenoid notch may depict isolated involvement of the infraspi-natus muscle [12].

Overhead activities with repetitive scapular motion, performed during sports such as volleyball and tennis, may produce stretching and compression of the suprascapular nerve and its branches under the suprascapular ligament. Repetitive adduction and internal rotation of the shoulder can stretch the nerve underneath the spinoglenoid ligament [11]. Direct trauma, scapular fractures, or post-traumatic calcification of the suprascapular ligament may also produce compression of the nerve. Peripheral nerve injury, including suprascapular neuropathy, was noted in 28% of patients who had full-thickness tears of the rotator cuff [13]. Iatrogenic injury to the suprascapular nerve can also occur during rotator cuff repair.

Suprascapular Nerve EntrapmentSuprascapular Notch Anatomy

Fig. 1. Normal MR anatomy of the suprascapular nerve. (A) Oblique coronal T1-weighted image shows the suprascapular neurovascular bundle (arrow) within the suprascapular notch. (B) Axial proton density image at the level of the spinoglenoid notch demonstrates the suprascapular nerve (arrow) highlighted by fat.

Fig. 1. Normal MR anatomy of the suprascapular nerve. (A) Oblique coronal T1-weighted image shows the suprascapular neurovascular bundle (arrow) within the suprascapular notch. (B) Axial proton density image at the level of the spinoglenoid notch demonstrates the suprascapular nerve (arrow) highlighted by fat.

Ganglion cysts at the scapular incisura, typically associated with superior and posterior labral tears, are other causes for suprascapular nerve entrapment [14,15]. Soft tissue masses, osseous tumors, and vascular malformations can also compress the nerve along its course.

MRI is a useful diagnostic modality in patients who have suprascapular nerve entrapment. Acute entrapment is depicted on water-sensitive sequences as hyperintensity involving the affected supraspinatus or infraspinatus muscles (Fig. 2), whereas chronic compression is noted as decreased bulk and fatty infiltration of the involved muscles. The extent of denervation muscle injury [16] can imply the exact site for the entrapment. Involvement of both the supraspi-natus and infraspinatus muscles reflects compression at the suprascapular notch, whereas isolated denervation of the infraspinatus muscle is compatible with compression at the spinoglenoid notch.

Was this article helpful?

+1 0
Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

Get My Free Ebook


Responses

Post a comment