Ultrasound-guided interscalene brachial plexus block is useful as a diagnostic maneuver to help identify if the brachial plexus is subserving pain from tumor, plexopathy, plexitis, abscess, or other pathology. Interscalene brachial plexus nerve block with local anesthetic may be used to palliate acute pain emergencies, including acute herpes zoster, brachial neuritis, brachial plexopathy including Parsonage-Turner syndrome, shoulder and upper extremity trauma, and cancer pain, while waiting for pharmacologic, surgical, and antiblastic methods to become effective. Interscalene brachial plexus nerve block is also useful as an alternative to stellate ganglion block when treating reflex sympathetic dystrophy of the shoulder and upper extremity. The use of ultrasound imaging can identify the exact location and course of the brachial plexus when surgical procedures of the neck are being contemplated. For surgery of the shoulder and upper extremity, interscalene brachial plexus block is the preferred approach for blockade of the brachial plexus.

The fibers that comprise the brachial plexus arise primarily from the fusion of the anterior rami of the C5, C6, C7, C8, and T1 spinal nerves (Fig. 30.1). In some patients, there may also be a contribution of fibers from C4 to T2 spinal nerves. The nerves that make up the plexus exit the lateral aspect of the cervical spine and pass downward and laterally in conjunction with the subclavian artery. The nerves and artery run between the anterior scalene and middle scalene muscles, passing inferiorly behind the middle of the clavicle and above the top of the first rib to reach the axilla (see Figs. 30.1 and 30.2). The scalene muscles are enclosed in an extension of prevertebral fascia, which helps contain drugs injected into this region and provide the theoretical and anatomic basis for this technique (Fig. 30.3).

To perform ultrasound-guided injection technique for interscalene brachial plexus block, place the patient in the supine position with the head turned away from the side to be blocked. The posterior border of the sternocleidomastoid muscle is identified by having the patient raise his or her head against the resistance of the clinician’s hand (Fig. 30.4). In most patients, a groove between the posterior border of the sternocleidomastoid muscle and the anterior scalene muscle can be palpated (Fig. 30.5). Identification of the interscalene groove can be facilitated by having the patient inhale strongly against a closed glottis. Once the interscalene groove is identified, the C6 level is identified by palpation of the cricothyroid notch. If the interscalene groove cannot be identified, the needle is placed just slightly behind the posterior border of the sternocleidomastoid muscle at the C6 level.

After preliminary identification of the approximate location of the brachial plexus utilizing surface landmarks, the skin is prepped with antiseptic solution, and 15 mL of local anesthetic is drawn up in a 20-mL sterile syringe, with 40 to 80 mg of depot steroid added if the condition being treated is thought to have an inflammatory component.

A linear ultrasound transducer is then placed over the previously identified location in the transverse plane, and a survey scan is taken (Fig. 30.6).