Chronic neck pain after whiplash injury is caused by trauma to the cervical zygapophyseal (facet) joints in about 50% of patients. Using ultrasound guidance in 14 volunteers, Eichenberger and coworkers ²¹ were able to visualize and inject adjacent to the third occipital nerve when attempting to block the nervous supply of the C2-3 facet joint. Fluoroscopy, however, demonstrates only the bony adjacent structures, not soft tissue structures such as nerves. Finally, Gruber and associates²² performed neurosclerosis in 82 patients with residual limb neuroma using ultrasound guidance and reported that these patients appeared to have better outcomes than those who received injections without ultrasound guidance.

In addition, ultrasound guidance helps to verify correct needle placement and to rule out subcutaneous injection of potent opioid doses when an intrathecal drug delivery device (pain pump) needs to be refilled. Finally, pain practitioners use ultrasound when investigating the presence of septic pockets at sites of implanted devices such as the spinal cord stimulation generators or intrathecal drug reservoirs.

Epidural and Selective Nerve Root Injections

ESIs have been described as the “bread and butter” of injection treatment for neck, back, and radiculopathic extremity pain. Published studies and commentaries have emphasized the safety of ESIs but questioned the efficacy of the technique and highlighted the ubiquitous, nondiscriminant application of ESIs.²³ Between 1996 and mid-2006, 69 ESI–related papers were published in the English-speaking medical literature. Prospective outcome studies are a small minority of these publications, whereas more than 50% are letters and reports of adverse events involving ESIs.²⁴

No conclusive prospective, randomized outcome studies have demonstrated long-term benefit, and multiple studies have demonstrated an outcome similar to placebo after 2 weeks.²⁴ The Wessex Epidural Steroids Trial (WEST)²⁵ study group found that neither single nor multiple ESIs improved on placebo when pain outcomes were measured 35 days after injection. Despite these controversies, ESIs probably have an important role to play in selected patients, particularly those with radicular pain.²⁶ The success of this important therapeutic procedure depends on attention to patient selection, technique, and concomitant therapies.

Rationale for Epidural Steroid Injections

It is well known that a herniated disk pressing on a nerve root can produce radicular pain. Inflammation may play a role in symptomatic nerve root irritation that is associated with herniated intervertebral disks.²⁷ Proinflammatory substances are contained in extruded nucleus pulposus material and may produce an inflammatory response in the epidural space and in the underlying nerve roots.²⁸^–³¹ It is likely that pain and other symptoms are produced by a combination of this inflammatory response, edema, and the mechanical pressure on nerve roots.

Steroids can decrease neurogenic inflammation and produce membrane stabilization that results in pain relief, but the effect may take several days. In individuals who have symptoms, the epidural space can be very sensitive to any pressure or injection. Because of the delayed onset of this steroid effect, a rationale can be made for including a local anesthetic in the injection, decreasing the pain of the initial injection. The local anesthetic can also prognosticate the expected pain relief that may later derive from the steroid based on the patient’s experience of early relief of pain after the precise delivery of the local anesthetic–steroid mixture.

Indications, Contraindications, and Limitations

Radicular extremity pain that has not responded to more conservative treatment is the primary indication for ESI (Table 158-2). ESI is not indicated for the treatment of mechanical or muscular axial back pain. Outcome studies do not clearly support the use of ESIs in spinal stenosis patients,³² but many clinicians feel that they can be helpful in this population, particularly in patients with radicular symptoms. Benefit in patients with prior back surgery is less clear, but many believe a subset of these patients benefits from ESI as well.²⁶

TABLE 158-2 Selection for Epidural Steroid Injection

INDICATIONS	CONTRAINDICATIONS	FACTORS ASSOCIATED WITH FAILURE
Herniated nucleus pulposus with extremity pain in a radicular pattern	Anticoagulation Infection at the site	Smoking Unemployed
Foraminal stenosis with radicular symptoms	Other pain that is more intense	Long duration
Spinal stenosis with extremity symptoms Imaging studies with concordant findings	Lack of consent Allergy to intended injectate

Unvarying pain despite activity or treatment Pain present for weeks to months Relative contraindications include primarily back pain, failed prior epidural steroid injections, untreated anxiety or depression Psychological distress
Nonradicular pain

Adapted from Hopwood MB, Abram SE. Factors associated with failure of lumbar epidural steroids. Reg Anesth. 1993;18:238-243; and Jamison RN, VandeBoncouer T, Ferrante FM. Low back pain patients unresponsive to an epidural steroid injection: Identifying predictive factors. Clin J Pain. 1991;7:311-317.

Hwang and colleagues ³³ reported in a prospective, nonrandomized study that ESI is helpful in treating the pain of acute herpes zoster virus (HZV) infection. Manabe and associates³⁴ demonstrated that in addition to systemic antiviral treatment, an epidural infusion with local anesthetic was superior to saline in a prospective randomized trial at reducing pain and allodynia. ESIs administered during the acute stage can be used for the prevention of postherpetic neuralgia (PHN) and shorten the duration of pain.

Interlaminar versus Transforaminal

In a small study, Thomas and colleagues ³⁵ compared loss-of-resistance interlaminar ESI with fluoroscopically guided transforaminal ESI and found improved pain relief, functional, and quality-of-life indicators 6 months after injection in the transforaminal group. In addition, Ackerman and Ahmad³⁶ studied 90 patients with L5-S1 disk herniation and found that the transforaminal route of administration was superior to the caudal and interlaminar routes.

Injection Technique

The goal of the injection is to deliver steroid as a single agent or combined with local anesthetic to the presumed source of pain and symptoms. Delivery techniques vary widely, and a variety of solutions and volumes are commonly used.³⁷ Two very common techniques in widespread use are the parasagittal or midline interlaminar and the transforaminal approaches.

Interlaminar and Caudal Injection Techniques

For labor analgesia and perioperative anesthesia and analgesia, the epidural space is typically accessed using the loss-of-resistance technique with an interlaminar approach as the patient assumes a sitting or lateral decubitus position. The disadvantage is that the medication is delivered into the center of the posterior epidural space instead of being directed at the level and laterality of the suspected pathology. However, when combined with the use of contrast injection and multiplanar fluoroscopy, the technique has diagnostic value (the patency of foraminal openings, level of scarring, and spread of injectate are all seen with fluoroscopy) and the ability to ensure that the injectate has been delivered to the epidural space.

Without the use of fluoroscopic guidance, failure to achieve injection into the epidural space has been reported to be as high as 12% to 38%.³⁷^,³⁸ A prospective study of patients with previous back operations demonstrated a failure rate of 53% in placing an epidural needle at the desired level based on surface anatomy alone and only a 26% success rate in delivering injectate to the level of pathology.³⁷ In a retrospective study, Johnson and colleagues³⁹ demonstrated that combining epidurography with ESI permitted safe and accurate therapeutic injections with an exceedingly low incidence of complications.

Commonly, a specialized epidural needle such as a 17- to 22-gauge Tuohy or a Crawford needle, coupled with the loss-of-resistance technique, is employed to locate the epidural space. Sometimes, an epidural catheter inserted through the needle is used to direct the medication delivery to a more cephalad target, such as a cervical nerve root through a T1-2 interspace. Finally, the lumbar epidural space may also be accessed caudally through the sacral hiatus using a catheter (e.g., Racz) that is cannulated through the needle and advanced cephalad.

Transforaminal Injection Technique

With the transforaminal technique, the epidural space is accessed at the neuroforamen yielding the index spinal nerve. This approach describes contrast spread that is intended to be more medial to ascend and descend in the epidural lateral gutter. However, the selective nerve root ESI represents an injection through a similar approach but with contrast outlining the nerve root and spreading laterally along its shaft. Nonetheless, correct application of the technique requires the use of fluoroscopy because surface landmarks and tactile sensations are unreliable in ensuring appropriate final needle position.

With the patient in a prone position, the primary lumbar landmarks for performing this injection are the transverse process above the desired nerve root representing the superior aspect of the neuroforamen. The target area is referred to as the safe triangle because it does not contain neural structures and therefore limits the opportunity for direct nerve damage from the needle ⁴⁰ (see “Fluoroscopy” earlier).

Typically, a 3- to 6-inch, 22- to 25-gauge needle is used with or without an introducer needle. We use a curved needle technique, in which the distal aspect of the needle is curved away from the bevel opening. This technique provides improved steering to the needle for arriving at the target and navigating around sensitive structures such as the nerve root. Needle position is confirmed using radiographic contrast injection; then, a combination of local anesthetic and steroid is injected.

The transforaminal approach to the epidural space has become the standard approach for many practitioners. The ability to deliver concentrated, small volumes precisely to the suspected site of pain generation is the main reason for this popularity, but there are several additional advantages. A small-caliber needle (e.g., 25 gauge) can be used at a location remote from the intrathecal space and nerve root, minimizing the risk for damage to sensitive structures and cerebrospinal fluid fistula formation. Diagnostically, the pressure of injection on the nerve root may reproduce the patient’s radicular symptoms, confirming the likely source of the pain. Careful examination of contrast flow under pulsed or continuous fluoroscopy allows the clinician to visualize the patency of the neuroforamen and confirm the spread medially to the epidural space for a transforaminal injection as opposed to laterally for a selective nerve root injection.

Outcomes and Adverse Events

Dunbar and coworkers ⁴¹ performed a sophisticated study in which they measured inline epidural infusion pressure in patients with degenerative spinal disease in a group of patients who had undergone an ESI. Initially, these patients had significantly increased infusion pressures compared with unaffected patients, which reflects outflow resistance or obstruction. There was a significant decrease in inline epidural infusion pressure when it was measured 3 weeks after an ESI. This led the investigators to suggest that ESIs are helpful in decreasing epidural space encroachment by likely inflamed and edematous neural structures.

Carette and associates ⁴² published a randomized, double-blind trial of 158 subjects who received up to three injections of methylprednisolone acetate and saline, compared with a smaller volume of saline alone for patients with sciatica due to herniated nucleus pulposus. The steroid group had short-term improvements in leg pain, mobility, and sensory deficits and no long-term benefit or change in eventual surgical intervention rate. This study has been widely referenced by non–pain specialists as evidence that epidural steroids have little role in managing radicular pain, whereas pain physicians have noticed the ESI technique deficiencies.

Along the line that ESIs provide short-term relief most predominantly, there are other such studies. Buchner and coworkers ⁴³ studied the effect of an ESI injection containing 100 mg methylprednisolone in 10 mL of bupivacaine compared with no treatment in 36 patients. They found that after 2 weeks, patients receiving the ESI showed a significant improvement in straight leg raise testing and that the treatment may be valuable in the acute phase. However, after 6 weeks and 6 months, pain relief and improvement of straight leg raising and functional status showed no statistical significance.

Potential complications of ESIs include dural puncture headache, increased pain, vasovagal response, elevated blood glucose levels, systemic local anesthetic toxicity from an intravenous injection, adhesive arachnoiditis, hematoma, bleeding, infection, and nerve damage.

Hooten and colleagues ⁴⁴ reported on an epidural abscess and meningitis after ESI, which occurred in an elderly patient with neutropenia who suffered an inadvertent dural puncture. They thought that antibiotic prophylaxis for Staphylococcus aureus should be considered for immunocompromised patients undergoing such injections.

Facet Joint and Medial Branch Nerve Procedures

During the past 25 years, the lumbar, cervical, and thoracic facet (zygapophyseal) joints have been a topic of considerable interest as they pertain to axial spinal pain and its minimally invasive treatment. The technique of using selective denervation of the facet joints to reduce pain caused by facet joint arthropathy has gained much support because of an increasingly positive body of evidence in the medical literature.

Intra-articular Facet Joint Injections

Injections into the lumbar facet joint are a popular, if somewhat understudied, modality of treating lumbar spinal pain. Advances in technology, specifically in the area of radiographic visualization, have made fluoroscopic identification of the facet joint and subsequent cannulation possible. However, because of extravasation of injectate into the epidural space or surrounding musculature, the lack of specificity of this technique led to its discredit as a diagnostic tool.⁴⁵^,⁴⁶ Further investigation into the utility of these injections as a therapy for acute back pain also diminished enthusiasm because intra-articular injections of local anesthetic and corticosteroid were found to be similar to placebo injections several months after injections.⁴⁷

Despite some of these outcome studies, facet joint injection is frequently performed because of the ease of injection into the facet joint. To improve the ease and accuracy of the injections, ultrasound has been studied as an imaging modality in placing the injections.⁴⁸ The efficacy of facet joint injections alone for axial back pain and improved function has been questioned. Some suggest that facet joint injections along with physical therapy may be helpful in improving pain and range of motion.⁴⁹

Lumbar Medial Branch Denervation

Bogduk and Long ⁵⁰ clarified the neuroanatomy of the facet joint in the late 1970s. This improved understanding, along with improvements in technology, allowed for development of radiofrequency neurodestructive procedures, including radiofrequency energy to disrupt the nervous supply (medial branch nerves) of the facet joints. Some studies have indicated that this treatment improves pain, but perhaps not over placebo.⁵¹^,⁵² A recent analysis found that psychological variables played a large role in long-term outcomes from denervations.⁵³

Cervical and Thoracic Medial Branch Denervation

The same principles and techniques used in diagnosing and treating lumbar pain from facet arthropathy have been applied to the cervical spine. One recent study also called the efficacy of cervical medial branch denervation into question.⁵⁴ However, radiofrequency cervical medial branch denervation demonstrated prolonged benefits in other studies.⁵⁵^,⁵⁶ McDonald and associates⁵⁷ reported significant pain relief after radiofrequency cervical medial branch denervation in 71% of treated patients. The patients with success had a median duration of relief of 422 days. Also, repeating the denervation procedure potentially could treat recurrent pain.

Neuroanatomy

Facet joints begin at C1-2 and are present down to the L5-S1 levels. They are synovial joints, with the capsule and synovium extensively innervated with sensory fibers. Innervation includes mechanoreceptors ⁵⁸ and involves multiple neurotransmitters such as substance P,⁵⁹ which are linked to nociception.⁶⁰^,⁶¹ Their innervation is thought to be segmental and based primarily on the medial branch of the primary posterior ramus of each segmental spinal nerve (Fig. 158-3).³⁷

FIGURE 158-3 Thoracic space anatomy.

(Courtesy of Brett Stacey, Oregon Health & Science University School of Medicine, Portland, OR.)

The medial branch innervates the multifidus muscle segmentally in addition to the facet joint capsule and its contents. This muscle, itself a significant pain generator, may account for some of the analgesia associated with lumbar medial branch blocks and denervations.⁶²^,⁶³ Except for this muscle, there is no other significant structure for which the medial branch is the sole innervation. The anatomy of the cervical, thoracic, and lumbar medial branches is demonstrated in Figure 158-4.

FIGURE 158-4 Lumbar vertebral body anatomy with medial branch.

(Courtesy of Brett Stacey, Oregon Health & Science University School of Medicine, Portland, OR.)

Diagnosis

Diagnosis of pain due to facet arthropathy is based on an accurate history and physical examination. Several physical examination characteristics are used to select patients for diagnostic lumbar medial branch blocks; classic signs include localized low back pain exacerbated by rotation and extension ⁶⁴ with referral in a stereotypical distribution (Fig. 158-5). Incorporating facet-loading maneuvers into the physical examination of the lumbar spine is recommended. Physical evaluation of the lumbar spine for facet arthropathy includes characteristics such as localized unilateral low back pain, pain on unilateral palpation of the facet joint or transverse process, lack of radicular features, pain eased by flexion, and pain, if referred, located above the knee.⁶⁵ A sequence of diagnostic injections of the medial branches is performed to help secure the diagnosis.

FIGURE 158-5 Referral patterns for cervical (A), thoracic (B), and lumbar facets (C).

(A, Adapted from Lord SM, Barnsley L, Wallis BJ, Bogduk N. Chronic cervical zygapophysial joint pain after whiplash. Spine. 1996;21:1737-1745. B, Adapted from Dreyfuss P, Tibiletti C, Dreyer SJ. Thoracic zygapophyseal joint pain patterns. Spine. 1994;19:807-811. C, Adapted from Fukui S, Ohseto K, Shiotani M, et al. Distribution of referred pain from the lumbar zygapophyseal joints and dorsal rami. Clin J Pain 1997;13:303-307.)

There was originally much speculation about the appropriate diagnostic regimen, but most clinicians use the so-called two-block paradigm. With this method, the patient is subjected to two sets of diagnostic, fluoroscopically guided medial branch injections.⁶⁶ These injections are usually single blinded (i.e., the clinician knows the contents of the injection; the patient does not) and contain a long-acting (e.g., 0.5% bupivacaine) or short-acting (2% lidocaine) local anesthetic. The patient is not sedated during the procedure. After the procedure, the patient is asked to complete a pain diary, recording numeric rating scale values representing the pain.

Pain relief in each of the two blocks that is concordant with the expected duration of the local anesthetic is required before the clinician makes a decision to perform radiofrequency denervation. One important consideration when using this model to guide further treatment is that it has fairly high false-positive rates, ranging from 15% to 67%, with one large retrospective study finding about 40% for cervical, thoracic, and lumbar blocks.⁶⁷ No other single model has emerged as a validated model to replace it.

Radiofrequency Denervation Treatment

Procedure

Neurolysis can be achieved using many techniques.⁶⁸ Various technical considerations have led to the use of radiofrequency energy as the method of choice for denervation of the medial branch (Table 158-3). Equipment improvements include small-diameter (22-gauge) and curved probes, which minimize tissue trauma and improve navigation. The lesion generator, which is also used for intracranial functional neurosurgery, allows multiple settings, depending on the procedure. Of greater importance is the ability to stimulate the adjacent structures with a harmless neurostimulating electrical field (motor and sensory testing) before denervation to rule out contact with the nerve roots. Although not universally used, this is a potentially significant safety advantage of this technique.

TABLE 158-3 Evaluation of Neurotomy Techniques

The medial branches of two segmental spinal nerves innervate each facet joint ipsilaterally (see Fig. 158-4). To effect anesthesia of the lumbar medial branch, the radiofrequency cannula has to be positioned precisely slightly inferior to the junction of the transverse process and the pedicle at each lumbar level. At the sacrum, the dorsal ramus of L5 is denervated in the sacral alar notch.⁶⁹ Also commonly denervated is the S1 contribution to the L5-S1 joint, the dorsal ramus that exits the superior aspect of the ipsilateral S1 neural foramen.⁷⁰

At the cervical levels inferior to C3, the active tip must be positioned in the concave aspect of the lateral articular pillar of the transverse process at each segment. At C3, the anatomy is similar to the inferior segments, except that it has a superficial branch that runs immediately posterior to the C2-3 facet joint and becomes the third occipital nerve, which is partially responsible for the sensory innervation of the posterior skull and scalp. In denervating this nerve as it passes posterior to the C2 lateral articular pillar, the C2 component of the C2-3 joint and the third occipital nerve are lesioned.⁶⁵

The thoracic anatomy can be more involved, but facet-related pain is less common in this distribution. Successful medial branch denervations have, however, been performed in the thoracic spine after the discovery that, at several levels, the medial branch exists in a plane not adjacent to the transverse process. The course of the medial branches of the thoracic dorsal rami is lumbar in character at T11 and T12 only. The other thoracic levels assume a different anatomic distribution. A two-needle technique has been advocated for this region.⁷¹ With the two-needle technique, one needle is inserted to contact the lateral third of the transverse process, and a second is positioned at the identical depth (as verified by lateral fluoroscopy) but cephalad, to be near the medial branch without puncturing the lung.

Outcomes

The prolonged effects of radiofrequency medial branch denervation have been demonstrated in numerous studies. The cervical region is the most thoroughly studied of these procedures. In this area, 75% of the treatment group had at least 50% analgesia for a median duration of 263 days.⁶⁶ With radiofrequency denervation, the neuronal contents are selectively coagulated, and neuronal function is interrupted. However, the neuronal substrate remains.^68,⁷⁰ This allows regrowth of the nerve about 8 to 12 months after the procedure but prevents neuroma formation.

The pain relief from the procedure is sufficient to allow many of the patients to improve their activity tolerance and reduce other therapies for pain; however, various investigators have questioned the value of a “permanent” procedure that “wears off.” There is no contraindication to repeating the denervation if the symptoms recur, nor is there an additional technical disadvantage presented by repeat denervation. Compared with surgical therapy, these considerations favor the minimally invasive route.

Sympathetic Nerve Blocks

Anatomy of the Sympathetic Nervous System

The sympathetic nervous system is commonly described as the “fight-or-flight” part of the autonomic nervous system. It causes multiple effects, including vasoconstriction, increased heart rate, decreased intestinal motility, and piloerection. The sympathetic nervous system efferent fibers begin in the intermediolateral column of the spinal cord and exit along the ventral roots from T1 to L2. These fibers then exit the ventral root as white rami communicantes and enter the sympathetic chains, which lie on the anterolateral aspect of the vertebral bodies.

These preganglionic fibers, as the name implies, eventually synapse in one of the sympathetic ganglia. After synapsing, the postganglionic fibers then travel to their site of action.⁷² Afferent fibers carrying pain and visceral sensation travel along the somatic nerves (carrying somatic pain) or travel as hitchhikers with the sympathetic nerves (carrying visceral pain and sensation). Those afferent fibers pass through the sympathetic ganglia but do not synapse there. They are thin, unmyelinated nerves, commonly classified as C fibers, which transmit burning, aching pain. These fibers enter the spinal cord through the dorsal roots, and they have their cell bodies in the dorsal root ganglia. Because these visceral sensory nerves travel beside the sympathetic nerves, sympathetic nerve blocks inevitably anesthetize these nerves as well.

Indications for Sympathetic Nerve Blocks

For years, sympathetic blocks were used to diagnose reflex sympathetic dystrophy, now known as complex regional pain syndrome type I (CRPS I), if the pain and autonomic dysfunction were relieved. However, even if the blocks are no longer the diagnostic tool for CRPS I (soft tissue injury) or II (discrete nerve injury) they were once thought to be, they can still provide useful information for other conditions.

Sympathetic blockade with local anesthetic can predict the effectiveness of a neurolytic sympathetic block, as in celiac plexus neurolysis for the pain of pancreatic carcinoma. The simultaneous blockade of the C fibers can often yield tremendous pain relief even if the disorder is unrelated to the sympathetic nervous system. Sympathetic nerve blocks, if properly done, do not cause somatic numbness or motor blockade, unlike blockade of the somatic nerves. This can be an especially useful technique for patients who are unable to obtain acceptable pain relief from other methods. Some patients accept significant risk for morbidity or mortality from sympathetic blockade because it is such an effective treatment of their pain, especially when they are confronted with terminal illnesses.

The vasodilation caused by a sympathetic block can also be helpful in treating certain vasculopathic disorders. Any condition that produces a significant amount of vasoconstriction and ischemic pain may be relieved or moderated by sympathetic blockade. In these conditions, the sympathetic efferent fibers, rather than the afferent C fibers that are responsible for transmission of pain stimuli, are the targets of the therapy. Ischemic pain, tissue breakdown, and slow healing can be reasons for performing sympathetic blocks. Diseases such as scleroderma that manifest with vasospasm and tissue ischemia may respond to sympathetic blockade. Extreme cases may warrant sympathetic neurolysis to give the patient pain relief and allow the tissues to heal.

Peripheral vascular surgery is a special case in which temporary sympathetic blockade may make the difference between success and failure. After the anastomosis of small arteries for repair of traumatic amputation or replantation surgery, there may be vasospasm and loss of circulation. In many cases, a sympathetic block can significantly reduce the degree of vasospasm and maintain blood flow through the repaired or damaged vessels.

Sphenopalatine Ganglion Block

The sphenopalatine or Meckel’s ganglion usually is the most rostral of the sympathetic ganglia that are commonly blocked. The sphenopalatine block was rarely done until recently, but it is now thought to be effective in treating and preventing cluster headaches. The ganglion is a small triangular mass in the pterygopalatine fossa, medial and inferior to the maxillary nerve and lateral to the sphenopalatine foramen. The sphenopalatine ganglion is not made up of only sympathetic nerves; it receives two (or three) sensory fibers from the maxillary nerve and receives parasympathetic fibers from the nervus intermedius of the facial nerve through the greater superficial petrosal nerve. The sympathetic fibers arise from the carotid plexus and arrive through the deep petrosal nerve. Although this is a mixed ganglion, its sympathetic nerves supply the nose, orbit, and part of the face, making it a useful ganglion to block. The sensory components involve the mucosa of parts of the nose, palate, uvula, and tonsils.

In performing the block, the sphenopalatine ganglion can be approached extraorally, in the same way as the maxillary nerve, or it can be approached intranasally. It may also be blocked by insertion of a needle through the greater palatine foramen and by advancement of the needle along the pterygopalatine canal.

Stellate Ganglion Block

Moving caudally, the next major sympathetic block is the stellate ganglion block. The stellate ganglion supplies sympathetic fibers to the ipsilateral upper extremity and one half of the head. It is often used when vasodilation of the arm or face is desired or for treating certain painful conditions (e.g., CRPS I) of the hand or arm.

The efficacy of stellate ganglion blockade for the management of CRPS I was studied by Ackerman and Zhang ⁷³ using three blocks performed at weekly intervals. Laser Doppler fluxmetric hand perfusion studies were performed on normal and treated subjects. The investigators concluded that an inverse relationship existed between hand perfusion and the duration of symptoms of CRPS I. In addition, they concluded that there was a positive correlation between stellate ganglion block efficacy and how soon the therapy was initiated. They found that if symptoms existed for longer than 16 weeks before therapy or if the skin perfusion had decreased 22% or greater compared with the unaffected hand, the efficacy of the blocks was reduced.

There are many adverse effects and complications from performance of a stellate ganglion block. For example, Horner’s syndrome (i.e., ptosis, miosis, and anhidrosis) is commonly seen and has often been taken as a sign of an effective block (it is not). The most serious complications are injection of local anesthetic into the carotid or vertebral arteries; either mistake leads to an almost immediate seizure. Another serious potential complication is high spinal anesthesia, which can occur if the local anesthetic is injected into a dural cuff. Potentially, a high-level epidural anesthesia could also occur if the local anesthetic went through the neural foramina.

A brief review of the anatomy of the sympathetic nervous system in the cervical region helps our understanding of this block. The neck has three sympathetic ganglia: the superior, middle, and inferior cervical ganglia. The inferior cervical ganglion is usually fused to the first thoracic ganglion, and together, they are called the stellate ganglion. The stellate ganglion is 1 to 3 cm long and lies anterior to the transverse process of C7 and the first rib. Anterior to this ganglion is the vertebral artery, and anteromedial to it lies the carotid artery. Immediately inferior to the stellate ganglion is the dome of the pleura. The dural cuffs of the seventh and eighth cervical nerve roots are also in the immediate vicinity. Therefore, the stellate ganglion is truly in a hazardous zone.

The classic approach to the stellate ganglion block is to pierce the skin over the anterior tubercle of the C6 transverse process (i.e., Chassaignac’s tubercle) and advance the needle to contact the anterior tubercle. After withdrawing the needle 2 or 3 mm to clear the periosteum, local anesthetic is injected. Because the sympathetic chain lies in a fascial space between the longus coli muscle and the scalene muscle group, any liquid injected at the stellate and middle ganglion level will likely travel along this narrow space and end up surrounding the two structures as well as the inferior portion of the superior cervical ganglion.

Thoracic Sympathetic Block

The thoracic sympathetic chain, unlike the cervical sympathetic chain, is close to the spinal (segmental) nerves, and there is no muscle or fascial layer separating the two. This proximity limits the utility of the thoracic sympathetic block somewhat because of the higher probability of also having a somatic block. However, sensory and motor blockade in the thoracic dermatomes is extremely well tolerated by most patients, even when it is permanent.

Most often done for painful conditions of the chest wall, thoracic sympathetic blocks may also be effective for pain involving the heart and lungs. Intractable angina can often be effectively treated with this block, although the loss of the “cardiac accelerator” fibers can be a serious problem in this patient population. Pain due to primary or metastatic tumors of the lungs may also be relieved by a thoracic sympathetic block.

Thoracic sympathetic block is usually accomplished by inserting a long needle over the tip of the transverse process. The needle is then advanced to contact the tip of the transverse process and redirected to pass inferior to the rib while also directed slightly medially. The needle is then advanced to contact the vertebral body. There is a risk for damaging the spinal roots when performing a neurolytic sympathetic block.

Celiac Plexus and Splanchnic Nerve Blocks

The viscera of the upper abdomen obtain their innervation from sympathetic rami of T5 to T12. These fibers course along the lateral aspect of the thoracic vertebral bodies and the greater, lesser, and least splanchnic nerves. These nerves pass through the diaphragm at the thoracolumbar junction and enter the abdominal cavity, where they finally form the celiac plexus. From this plexus, sympathetic nerves travel to the organs of the upper abdomen, and C-fiber afferent nerves carry impulses from those organs.

All the sensation from the upper abdominal viscera passes through the celiac plexus, so the celiac plexus block can be a powerful tool for controlling abdominal pain. Because there are few or no somatic sensory or motor nerves that pass through the celiac plexus, neurolysis carries little liability. The celiac plexus may be the most common site of neurolytic nerve block. Almost every practitioner performs a local anesthetic block before neurolysis to ensure that the preprocedural assessment is correct. Patients with mysterious abdominal pain may also undergo celiac plexus blockade to differentiate among psychogenic, visceral, and somatic pain.

To block the splanchnic nerves, the needles are directed toward the body of T12. To approach the celiac plexus, needles are inserted bilaterally at the L1 level, starting over the tips of the 12th ribs. The needles are then advanced to the anterolateral aspect of the vertebral body. Because the celiac plexus projects anteriorly much farther than the splanchnic nerves, the needle tips should end up between 1 and 2 cm anterior to the anterior margin of the L1 vertebral body.

Lumbar Sympathetic Block

The lumbar sympathetic chains carry preganglionic fibers from the lower thoracic sympathetic nerves and enter the abdomen posterior to the medial arcuate ligament and anterior to the psoas muscle. They then travel along the psoas fascia to reach the anterolateral aspect of the vertebral bodies, eventually running along the medial border of the psoas muscle. The left sympathetic chain lies posterior and lateral to the aorta, and the right sympathetic chain lies posterior to the vena cava. The lumbar sympathetic chains synapse within the lumbar sympathetic plexus and then send rami communicantes to the first and second lumbar spinal nerve roots. The separation of the spinal roots and the sympathetic ganglia allows the sympathetic nerves to be blocked or destroyed by neurolysis with less risk to the somatic nerves.

There have not been many prospective studies regarding outcomes of lumbar sympathetic blocks as a treatment for lower extremity disorders. Of interest is a study by Tran and coworkers,⁷⁴ who performed 28 lumbar sympathetic blocks in an attempt to correlate cutaneous toe temperature change with relief of allodynia. They found that a successful lumbar sympathetic block was realized when ipsilateral toe temperatures increased to within 3° C of core temperature. They suggest that cutaneous toe temperatures approaching core temperature may predict relief of sympathetically maintained pain.

Two approaches to the lumbar sympathetic chains are commonly in use: the paramedian approach and the lateral approach. In the paramedian approach, the needles enter the skin at about the level of the transverse process and 5 to 6 cm lateral to the midline. The lateral approach begins 9 to 10 cm lateral to the midline. These two different approaches have their own advantages and disadvantages, but they are essentially identical in their ease and risks.⁷⁵

Another variation in the approach to the lumbar sympathetic chain is in the number of injections. Early descriptions of the procedure recommended three to four injections on each side, usually at the level of L1, L2, and L3 (and occasionally L4). These injections now are performed at a single level, L1 or L2. With the multiple-injection techniques, smaller injection volumes (2 to 3 mL) are used, and the single-injection technique uses volumes of 10 to 20 mL and relies on spread of the local anesthetic along fascial planes. Surprisingly, the incidence of spillover onto the spinal nerve roots is fairly low with the bilateral single-injection technique. When using a neurolytic agent such as phenol, however, the extra margin of safety of the multiple-injection technique is invaluable.