Stellate ganglion block (SGB) is used for the treatment of many medical conditions including complex regional pain syndrome and peripheral vascular disease. Historically, the anesthetic has been injected at the C6 or C7 vertebral level with the Chassignac’s tubercle, the cricoid cartilage, and the carotid artery serving as the anatomic landmarks to the procedure. Due to a high risk of side effects, for example, pneumothorax and vascular puncture, an image-guided approach is strongly suggested, even with the "safer" C6 approach.
The sympathetic fibers for the head, neck, heart, and superior limbs arise from the first thoracic segments, ascend through the sympathetic chain, and synapse in the superior, middle, and inferior cervical ganglions. The stellate ganglion is present in 80% of the general population and is composed of the inferior cervical ganglion and the first thoracic ganglion fusion. It lies anterior to the neck of the first rib and extends to the inferior aspect of the transverse process of C7. Usually, it is located medial or posterior to the vertebral artery close to the dome of pleura.
The pain relieved by sympathetic block is classified as sympathetically mediated pain (SMP) that consists abnormal connection between sympathetic and sensory nervous systems.
The therapeutic effects of SGB are due to the block in neural connections in its region of innervation, the improvement in the blood supply of the region, the reduction of adrenal hormones plasma concentration. SGB can be used in medical conditions like post-traumatic stress disorder or a cluster headache based on its sedative effect. SGB can be used as diagnostic tool to confirm an SMP.
SGB requires a trained pain physician as it is a procedure of intermediate difficulty. A nurse is required to assist the patient during the injection for positioning. If the fluoroscopic technique is used, the assistance of a radiology technician is needed.
The patient's vital signs should be monitored before and immediately following the procedure. A peripheral venous catheter should be placed in all patients. It is important to obtain a detailed medical history before the procedure to rule out any contraindications and evaluate risk/benefits ratio.
The patient is supine with the neck slightly extended and the head slightly rotated contralateral to the approached side. The site is cleaned and draped, and the transducer is placed perpendicular to the tracheal axis at the cricoid cartilage and is moved inferiorly until the superior aspect of the thyroid gland is visualized. Later, the transducer should be relocated laterally to visualize the anterior aspect of the Chassaignac’s tubercle on the C6 transverse process. The carotid artery, internal jugular vein, thyroid gland, trachea, Longus colli and Longus capitis muscle, prevertebral fascia, the root of C6 spinal nerve, and transverse process of C6 can be identified (see Figure 1). Color Doppler should be used to detect the position of the vessels. With an in-plane approach, the needle is placed beside the trachea with a lateral to medial direction. The tip must reach the prevertebral fascia of the Longus colli muscle located between the posterior aspect of the carotid artery and the tip of C6 anterior tubercle. Injury to vessels and nerves should be avoided. An aspiration test must be done to avoid the suction of blood or cerebrospinal fluid, then a local anesthetic is injected, and the diffusion of the injectate is seen in real time. The injection is suggested not inferior to the C6 level because the vertebral artery is left unprotected at the C7 level due to its absent or rudimentary anterior tubercle. Five milliliters of a local anesthetic such as lidocaine 2% is injected until the fluid spread along the paravertebral fascia to the stellate ganglion.
The patient is placed in a supine position, and an anteroposterior view is obtained with the C-arm to identify C6 by counting up from T1. Then the C-arm is tilted to line up the superior aspect of the C6 vertebral body and is rotated obliquely at approximatively 25 to 30 degrees ipsilaterally to obtain a foraminal view. The target is the junction of the vertebral body and the uncinate process (of C6). Under an oblique view, the needle is inserted laterally with a lateral to medial trajectory and remains over the vertebral body or slightly medial to avoid injury to vessels, spinal nerves, and disc. The position needs to be checked through the anteroposterior and lateral views. A small amount of contrast media (0.5 to 1 ml) can be injected first to localize the needle. A tiny test dose of local anesthetic is then administered to reduce the risk of intravascular injection further. Then 10 ml of a local anesthetic such as lidocaine 1% is injected. The same procedure can be performed at the C7 level if needed, but the physicians must be aware of higher risks of vascular puncture at the C7 level.
A sympathetic block as SGB can be useful in the diagnosis and treatment of SMP in the upper limb, head and neck regions; it can also be used in the treatment of medical conditions as post-traumatic stress disorder, cluster headache or intractable angina.