Ultrasound-Guided Injection Technique for Suprascapular Nerve Block
CLINICAL PERSPECTIVES
Ultrasound-guided suprascapular nerve block is useful in the management of the scapular and acromioclavicular joint pain as well as shoulder pain subserved by the suprascapular nerve and in the palliation of pain of malignant origin emanating from tumors of the scapula, acromioclavicular joint, and the superior and posterior shoulder. This technique serves as an excellent adjunct to general anesthesia when performing surgery on the abovementioned areas. Suprascapular nerve block with local anesthetic may be used to palliate acute pain emergencies, including postoperative pain, pain secondary to traumatic injuries of the shoulder joint and girdle, and cancer pain, while waiting for pharmacologic, surgical, and antiblastic methods to become effective. Suprascapular nerve block is also useful as an adjunctive therapy when treating the decreased range of motion of the shoulder secondary to reflex sympathetic dystrophy or adhesive capsulitis. Suprascapular nerve block can also be used to allow more aggressive physical therapy after shoulder reconstruction surgery. Ultrasound-guided suprascapular nerve block can also be used in a prognostic manner to determine the degree of neurologic impairment that the patient will suffer when destruction of the suprascapular nerve is being considered or when there is a possibility that the nerve may be sacrificed during surgeries in the anatomic region of the suprascapular nerve. This technique may also be useful in those patients suffering from symptoms secondary to compression of the suprascapular nerve by ganglion cysts or tumors which may present clinically as wasting of the infraspinatus muscle (Fig. 42.1). Ultrasound-guided suprascapular nerve block may also be used to palliate the pain and dysesthesias associated with stretch injuries to the suprascapular nerve such as backpack neuropathy.
Plain radiographs are indicated in all patients who present with shoulder pain. Based on the patient’s clinical presentation, additional testing may be indicated, including complete blood cell count, sedimentation rate, and antinuclear antibody testing. Magnetic resonance imaging or ultrasound evaluation of the affected area may also help delineate the presence of ganglion cysts or other masses compressing the suprascapular nerve as it passes through the suprascapular notch (Fig. 42.2).
CLINICALLY RELEVANT ANATOMY
The key landmark when performing suprascapular nerve block is the suprascapular notch. Arising from fibers from the C5 and C6 nerve roots of the upper trunk of the brachial plexus with some contribution of fibers from the C4 root, the suprascapular nerve travels in an inferior and posterior path from the brachial plexus to pass underneath the coracoclavicular ligament through the suprascapular notch. The suprascapular artery and vein accompany the nerve through the suprascapular notch (Figs. 42.3 and 42.4). The suprascapular nerve provides much of the sensory innervation to the shoulder and acromioclavicular joint and provides innervation to the supraspinatus and infraspinatus muscles of the rotator cuff.
FIGURE 42.2. Patient presenting with pain and weakness of the infraspinatus muscle. A,B: Axial T2-weighted image, TR/TE 2500/70, and coronal oblique fast spin echo T2-weighted sequence with fat suppression. A large paralabral cyst is identified (shorter arrows). It is arising in relation to a posterosuperior labral tear (longer arrows) and extends into the spinoglenoid notch region. Axial T1-weighted image (C); axial and coronal oblique STIR images (D,E). A type 2 SLAP lesion is seen (longer arrows). A paralabral cyst is arising from the posterosuperior portion (arrowheads). There is denervation edema/atrophy in the infraspinatus muscle (shorter arrows). (Reused from Zlatkin MB. MRI of the Shoulder. 2nd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2003, with permission.)
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