Stellate Ganglion Block
The sympathetic nervous system is involved in the pathophysiology that leads to a number of different chronic pain conditions, including complex regional pain syndrome (CRPS) and ischemic pain. These chronic pain states are often referred to as sympathetically maintained pain because they share the characteristic of pain relief that follows blockade of the regional sympathetic ganglia. Stellate ganglion block is an established method for the diagnosis and treatment of sympathetically maintained pain of the head, neck, and upper extremity.
Sympathetic fibers to and from the head, neck, and upper extremities pass through the stellate ganglion. In many individuals, the stellate ganglion is formed by fusion of the inferior cervical and first thoracic sympathetic ganglia. The ganglion is commonly found just lateral to the lateral border of the longus colli muscle, and anterior to the neck of the first rib and the transverse process of the seventh cervical vertebra (Figs. 10-1 and 10-2). In this position, the ganglion lies posterior to the superior border of the first part of the subclavian artery and the origin of the vertebral artery and posterior to the cupola of the lung. Although several approaches to stellate ganglion block have been described, the most common is the anterior paratracheal approach at C6 using surface landmarks. Performing the block at C6 reduces the likelihood of pneumothorax, which is more likely when the block is carried out close to the cupola of the lung at C7. The anterior tubercle of the transverse process of C6 (Chassaignac’s tubercle) is readily palpable in most individuals. To perform the block without radiographic guidance, the operator palpates the cricoid cartilage and then slides a finger laterally into the groove between the trachea and the sternocleidomastoid muscle, retracting the muscle and adjacent carotid and jugular vessels laterally. Chassaignac’s tubercle is typically palpable in this groove at the C6 level. Once the tubercle has been identified, a needle is advanced through the skin and seated on the tubercle, where local anesthetic is injected. The local anesthetic spreads along the prevertebral fascia in a caudal direction to anesthetize the stellate ganglion, which lies just inferior to the point of injection in the same plane. In practice, there is marked variation in the size and shape of Chassaignac’s tubercle that reduces the rate of successful block. The adjacent vertebral artery and C6 spinal nerve must be avoided to safely conduct this block (Figs. 10-1, 10-2 and 10-3). A simple modification of technique in which the needle is directed medially toward the base of the transverse process using radiographic guidance is a safe and simple means of improving the reliability of stellate ganglion block and is described in the following sections. The use of ultrasound to guide needle placement has revolutionized the conduct of regional anesthesia for surgical anesthesia, but its use in pain treatment has been more limited. The majority of pain treatment techniques are now carried out with radiographic guidance and the bony elements of the spine prevent effective visualization of many structures within the spinal canal. However, stellate ganglion block is a notable exception to this rule. The critical soft tissue and vascular structures relevant to safely perform stellate ganglion block cannot be seen with fluoroscopy but are readily visualized with ultrasound (Fig. 10-4). Description of ultrasound-guided stellate ganglion block is beyond the scope of this text, but this technique may well supplant the use of radio-graphic guidance as more practitioners gain expertise with ultrasound.
Stellate ganglion block has long been the standard approach to diagnosis and treatment of sympathetically maintained pain syndromes involving the upper extremity, such as CRPS. Other neuropathic pain syndromes, including ischemic neuropathies, herpes zoster (shingles), early postherpetic neuralgia, and postradiation neuritis, may respond to stellate ganglion block. Blockade of the stellate ganglion has also proven successful in reducing pain and improving blood flow in vascular insufficiency conditions such as intractable angina pectoris, Raynaud’s disease, frostbite, vasospasm, and occlusive and embolic vascular disease. Finally, the sympathetic fibers control sweating; thus, stellate ganglion block can be quite effective in controlling hyperhidrosis (recurrent and uncontrollable sweating of the hands).
Causalgia (CRPS, type 2) was first described during the American Civil War. Soon thereafter, it was recognized that blockade of the sympathetic chain with local anesthetic could produce significant pain relief in patients with causalgia. Patients with CRPS have a history of trauma to the affected area: Those with a major nerve trunk injury, such as a gunshot wound to the brachial plexus, are classified as CRPS, type 2 (causalgia), and those with no major nerve trunk injury are classified as CRPS, type 1 (reflex sympathetic dystrophy). Both types of CRPS share the same signs and symptoms. Patients with CRPS report pain that has characteristics of neuropathic pain, including spontaneous burning pain and allodynia (pain produced by stimulation that usually does not cause pain, such as light touch). Patients with CRPS also report symptoms or have signs on physical examination of sympathetic dysfunction. These include temperature and color asymmetries between the affected and unaffected limbs, edema, and asymmetries in sweating of the limbs. Dystrophic changes may appear late in the course of CRPS, including thinning of the skin, hair loss, and pitting of the nail beds.
Patients with signs and symptoms of CRPS may gain significant pain relief from stellate ganglion block. Unfortunately, the duration and magnitude of the pain relief are unpredictable. This led to the use of repeated sympathetic blocks, sometimes as often as daily or weekly blocks over an extended period of time in an attempt to improve the duration of pain relief. Experts widely agree that repeated sympathetic blocks alone rarely eliminate the pain and disability associated with CRPS. A coordinated, multidisciplinary rehabilitation plan is essential for effective treatment of patients with CRPS. This treatment plan typically includes physical therapy, oral neuropathic pain medications, and supportive psychotherapy. Neuroablation has been used to destroy the sympathetic chain in those patients who attain excellent pain relief of temporary duration with local anesthetic blocks. There are few data available to evaluate the success of sympathetic ablation, and expert opinion is varied regarding the usefulness of this approach in the longterm treatment of CRPS.
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