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 following blockade of the regional sympathetic ganglia. Lumbar sympathetic block is an established method for the diagnosis and treatment of sympathetically maintained pain of the lower extremities.

The lumbar sympathetic chain consists of four to five paired ganglia that lie over the anterolateral surface of the second through fourth lumbar vertebrae (Figs. 12-1 and 12-2). The cell bodies of the neurons that travel to the lumbar sympathetic ganglia lie in the anterolateral region of the spinal cord from T11 to L2, with variable contributions from T10 and L3. The preganglionic fibers leave the spinal canal with the corresponding spinal nerve, join the sympathetic chain as white communicating rami, and then synapse within the appropriate ganglion. Postganglionic fibers exit the chain to join the diffuse perivascular plexus around the iliac and femoral arteries, or via the gray communicating rami to join the spinal nerves that form the lumbar and lumbosacral plexuses. Sympathetic fibers accompany all the major nerves to the lower extremities. The majority of the sympathetic innervation to the lower extremities passes through the second and third lumbar sympathetic ganglia, and blockade of these ganglia results in near complete sympathetic denervation of the lower extremities.

Lumbar sympathetic blockade has been used extensively in the treatment of sympathetically maintained pain syndromes involving the lower extremities. The most common of these are CRPS, type 1 (reflex sympathetic dystrophy) and type 2 (causalgia) (see Chapter 10 for an overview of CRPS). The local anesthetic block can produce marked pain relief of long duration, and this block is used as part of a comprehensive treatment plan to provide analgesia and facilitate functional restoration.

Patients with peripheral vascular insufficiency due to small vessel occlusion may also be treated effectively with lumbar sympathetic blockade. Proximal fixed lesions are best treated with surgical intervention using bypass grafting or intra-arterial stent placement to restore blood flow. In those patients with diffuse, small vessel occlusion, lumbar sympathetic block can improve microvascular circulation and reduce ischemic pain. If local anesthetic block improves blood flow and reduces pain, these patients will often benefit from surgical or chemical sympathectomy.

Other patients with neuropathic pain involving the lower extremities have shown variable response to lumbar sympathetic block. In those with acute herpes zoster and early postherpetic neuralgia, sympathetic block may reduce pain. However, once postherpetic neuralgia is well established (beyond 3 to 6 months from onset), sympathetic blockade is rarely helpful. Likewise, deafferentation syndromes such as phantom limb pain and neuropathic lower extremity pain following spinal cord injury have shown variable and largely disappointing responses to sympathetic blockade.

The use of sympathetic blocks in the diagnosis and management of a number of chronic pain conditions, including CRPS, has been common for decades despite the lack of scientific validation for this approach. Indeed, the very origins of the field of pain medicine grew from the anesthesiologists’ use of regional anesthesia including regional blockade of the sympathetic chain. Yet, the usefulness of sympathetic blocks in either the diagnostic evaluation or the long-term management of pain syndromes remains in question.

The American Society of Anesthesiologists (ASA) Task Force on Chronic Pain Management published a 2010 Practice
Guideline, offering the following recommendation regarding the use of sympathetic blocks for the diagnosis of pain: “The use of sympathetic blocks may be considered to support the diagnosis of sympathetically maintained pain. They should not be used to predict the outcome of surgical, chemical, or radiofrequency sympathectomy.” The ASA Guideline made the following recommendations regarding the use of sympathetic blocks as a component of pain treatment: “Lumbar sympathetic blocks or stellate ganglion blocks may be used as components of the multimodal treatment of CRPS if used in the presence of consistent improvement and increasing duration of pain relief. Sympathetic nerve blocks should not be used for long-term treatment of non-CRPS neuropathic pain.”

CRPS is uncommon and conducting randomized trials in this heterogeneous group of patients with neuropathic pain has been limited to a small number of small studies. Clear benefits have not been reported with sympathetic blocks based on the limited available data, yet the use of sympathetic blocks remains a component of the treatment algorithms put forth by contemporary experts. If the use of sympathetic blocks produces pain relief of sufficient magnitude and duration in an individual patient such that efforts to restore normal function are improved, then they should be incorporated into the treatment algorithm. If they produce pain relief of limited magnitude and duration for an individual patient, then the risks involved in using sympathetic blocks outweigh the benefits and their use for that patient should be abandoned.

The patient lies prone with the head turned to one side (Fig. 12-3). The C-arm is centered over the midlumbar region. The final needle position for lumbar sympathetic block is over the anterolateral surface of the lumbar vertebral body (see Fig. 12-2