Cervical Sympathetic (Stellate Ganglion) Block
Stellate ganglion block (SGB) was originally introduced by René Leriche for the treatment of angina pectoris. Findley and Patzer eventually modified the technique, which has remained largely unchanged since then and was named the anterior approach. This method is the most popular technique in North America. In addition, lateral, superolateral, and posterior approaches were introduced in the first half of the 20th century. All techniques are based on bony landmarks, such as the transverse process of C6, the spinous process of C7, and the first rib. Eventually, these techniques were empirically validated with fluoroscopy and computed tomography (CT) and later with ultrasonography.
Clinically Relevant Anatomy
The stellate ganglion, also known as the cervicothoracic ganglion, represents a fusion of the inferior cervical and first thoracic ganglia of the sympathetic trunk. It can be found in about 80% of the population. The anatomy and position of the stellate ganglion have been investigated by dissection, magnetic resonance imaging (MRI), and CT. It is usually situated at the lateral border of the longus colli muscle (LCM) anterior to the neck of the first rib ( Fig. 56.1 ). It lies posterior to the vertebral vessels and is separated from the cervical pleura by the suprapleural membrane inferiorly. The stellate ganglion measures 1 to 2.5 cm in length, is about 1 cm wide and 0.5 cm thick, and may be fusiform, triangular, or globular in shape.
Indications
SGB is commonly used for the diagnosis and management of sympathetically mediated pain and vascular insufficiency of the upper extremity. In addition, more esoteric indications that have been advocated include the treatment of a variety of medical conditions, such as phantom pain, post-herpetic neuralgia, cancer pain, cardiac arrhythmias, orofacial pain, and vascular headache. Recently, cervical sympathetic blockade has been suggested as an effective method for prevention and treatment of cerebral vasospasm, hot facial flushes, and post-traumatic stress disorder.
Evidence for Stellate Ganglion Block
Clinical effectiveness of SGB can be defined as undetermined. The majority of publications are case reports and case series. Neurolytic SGB is currently rarely practiced because the evidence is anecdotal. Malmqvist and colleagues assessed 54 SGBs performed blindly with bupivacaine. Their criteria for effective sympathetic blockade included Horner’s syndrome in combination with increased skin temperature, increased skin blood flow, and a completely abolished skin resistance response on both the radial and ulnar sides of the blocked hand. Only 15 of 54 blocks met four of the five criteria for an effective block. Another study examined the efficacy of SGB in patients with complex regional pain syndrome (CRPS) type 1. Pain relief and improved skin perfusion were observed in 40% of patients who had CRPS symptoms for 12 or fewer weeks, but no improvement occurred in the group with more protracted disease (35.8 ± 27 weeks). Two small pilot studies suggested that SGB can provide relief from hot flushes and sleep dysfunction with few or no side effects in survivors of breast cancer and post-traumatic stress disorder.
No clinical studies have compared a “blind” with fluoroscopy-guided SGB or fluoroscopy-guided with ultrasound-guided SGB. According to a study that evaluated the oblique and anterior paratracheal fluoroscopic approaches, both techniques were equally effective. However, improved safety and better satisfaction were reported with the former approach. Comparison of an ultrasound-guided with a surface landmark–based technique showed that less volume of local anesthetic was used with ultrasound-guided injection (5 vs. 8 mL). Hematoma did not develop in the ultrasound group, but it did develop after the procedure in three patients in the blind injection group. Ultrasound guidance resulted in more rapid onset of Horner’s syndrome.
Available Techniques
Although a C7 approach to the stellate ganglion has been described, SGB is still routinely performed at the C6 level by using the following anatomic landmarks: prominent anterior tubercle of the transverse process (Chassaignac’s tubercle) and cricoid cartilage, both of which facilitate identification of the level and finally the location of the carotid artery. Given that only traversing sympathetic fibers or middle cervical ganglia can be found at the C6 level, the procedure should more accurately be called a cervical sympathetic block. The middle cervical ganglion or traversing sympathetic fibers are located anterolateral to the belly of the LCM. Conceivably, such a “convenient” location makes it easy to access the sympathetic chain for either diagnostic or therapeutic blockade.
Cervical sympathetic block is traditionally performed as a “blind” injection via the anterior approach. It is accomplished by positioning the patient supine with the head rotated to the opposite side. Following palpation of the anterior tubercle of the C6 transverse process (Chassaignac’s tubercle), the carotid artery is gently retracted laterally. The needle is then inserted paratracheally until it contacts bone, presumably the lateral part of the vertebral body ( Fig. 56.2 ). The needle is then withdrawn 1 to 5 mm, and the medication is injected. This maneuver was presumed to be sufficient to position the needle outside the LCM, where the sympathetic ganglion is likely to be situated.
Fluoroscopic guidance reduces the overall risks associated with the “blind” technique. It has the advantage of identifying the bony anatomy, although the anatomic position of the cervical sympathetic trunk (CST) is confined to the soft tissues (LCM, thyroid, and esophagus) rather than to the cervical vertebrae. Injection of a contrast dye helps to confirm the procedural accuracy, although it may show aberrant and inconsistent spread. Such injection will, however, significantly decrease, if not eliminate the risk for intravascular injection. Typically, fluoroscopically guided SGB is performed similar to the blind technique just described. A coaxial anteroposterior view is used to direct the block needle toward the anterior base of either the C6 or C7 transverse process. Alternatively, the injection can be performed via an oblique fluoroscopic view ( Fig. 56.3 ). Most likely, neither “blind” nor fluoroscopically guided injection can ensure reliable results. Since the ultimate thickness of the LCM remains unknown, the contrast dye and subsequently the local anesthetic are injected into the muscle and then reach the sympathetic trunk by overflow or diffusion.
Several clinical and cadaver trials have been conducted in an attempt to elucidate the pattern of spread when solutions are injected at the C6 level. The results of these studies have been conflicting, probably because of differences in study design: cadavers or live subjects, low or high volume of injectant, and CT or fluoroscopy control. The results of one cadaver study suggested that deposition of a solution only into the prevertebral “interlaminar space” provides reliable spread to the stellate ganglion. The cervical prevertebral fascia is attached to the base of the skull and extends over the prevertebral muscles (longus capitis, rectus capitis, and longus colli) to the T4 vertebra, just beyond the LCM. This positioning of the fascia forms a plane along which the injected fluid can flow.
Although some anatomic and imaging studies indicate a subfascial position, textbooks allocate the path of the CST to the suprafascial plane. Two recently published studies have hopefully resolved this issue. The first used cadaver dissection and human MRI and showed a subfascial position of the stellate ganglion. This study found the thickness of the LCM to be highly variable, which may lead to negative block results. The second study was designed as a step-by-step methodology to validate a new ultrasound-guided approach (described below); a subfascial position of the sympathetic trunk was detected by three-dimensional ultrasonography and confirmed by cadaver dissection. In addition, this study measured the thickness of the LCM at the C6 level and proved that the muscle is 2 to 10 times thicker than was previously suggested in the regional anesthesia literature. Accordingly, routine injection by the traditional method would have resulted in an intramuscular injection, and the CST would be anesthetized only by overflow or diffusion of the injectant.
Ultrasound guidance is a logical solution to ensure accurate injection when soft tissues are involved. Clear imaging of the muscles, fasciae, blood vessels, viscera, and bone surface makes ultrasonography superior to fluoroscopy for image-guided CST blockade. In 1995 Kapral and coworkers described an ultrasound-guided anterior technique and published the results of a case series.
The patient is placed in the supine position. A pillow can be placed under the lower part of the neck to achieve some extension. The head may be rotated slightly contralateral to the injection side to increase the distance between the carotid artery and the trachea and improve the sonographic view. Ultrasonography of the anterior part of the neck is performed by initially placing the transducer at the level of the cricoid cartilage, anterior to the sternocleidomastoid muscle. Short-axis ultrasonography reveals the typical appearance of the C6 transverse process: a prominent anterior tubercle, a short posterior tubercle, and the exiting C6 nerve root ( Fig. 56.4 ). Scanning caudally and dorsally brings the C7 transverse process into view. The C7 transverse process has no anterior tubercle. The C7 nerve root is situated just anterior to the posterior tubercle ( Fig. 56.5 ). At the C6 level, the LCM is seen as an oval structure adjacent to the base of the transverse process and vertebral body. Sometimes the caudal portion of the longus capitis muscle can be seen as well. The CST is visualized as a spindle-shaped structure (the midcervical ganglion) and is typically situated on the posterolateral surface of the LCM. If the CST cannot be identified, some widening of the tissue plane below the prevertebral fascia can usually be seen. Once the correct level for injection is localized, the surrounding anatomic structures should be identified and the feasibility of the “anterior” approach determined. Frequently, the distance between the carotid artery and the trachea is wide enough, and therefore only thyroid tissue and superficial neck muscles are seen between the needle entry point and the surface of the LCM. Gentle pressure may actually decrease the skin-to-target distance and further separate the carotid artery from the trachea. Additional scanning should be performed to confirm that the inferior thyroid artery is not seen immediately caudad. The injection is performed in a short-axis, out-of-plane approach ( Fig. 56.6 ). The skin is anesthetized immediately caudad or cephalad to the transducer. The injection is performed with a spinal needle (22 to 25 gauge and 2 to 3.5 inches long), three-way stopcock, and extension tubing connecting two syringes, one with 0.9% NaCl and the other with local anesthetic. The needle is inserted under continuous ultrasound guidance and directed to the anterior surface of the LCM via a short-axis, out-of-plane approach. When the tip of the needle is visualized, either directly or indirectly (tissue movement) as the target is approached, 1 to 2 mL of saline is injected to confirm placement of the needle under the prevertebral fascia and facilitate clear separation of the tissue planes ( Fig. 56.7 ). If the injectant is observed above the fascia or within the muscle, the needle must be carefully repositioned. If the spread is appropriate, 5 mL of local anesthetic is injected and the needle is withdrawn.
