Lumbar Sympatholysis

Anatomy and Physiology

The sympathetic chain (also called the sympathetic trunk) consists of a bilaterally paired set of paravertebral nerves extending from the neck to the coccyx. These nerves play an essential role in the autonomic nervous system and subdivide into cervical, thoracic, lumbar, and sacral sections.

Most of the sympathetic output to the lower extremity is in the upper lumbar region. The presynaptic efferent nerve roots emerge from the anteromedial spinal cord via white rami of the ventral roots of the spinal nerves, which then synapse at the appropriate lumbar sympathetic ganglion. These ganglia provide the sympathetic output to the lower extremity. The postganglionic neurons continue to innervate their target sites. 

The lumbar sympathetic chain of ganglia innervating the lower extremity is located anterolaterally along the lumbar spine, usually at the levels of L2 through L4, lying at the medial margin of the psoas muscle. The aorta is anterior and medial to the left lumbar sympathetic chain, while the inferior vena cava is anterior to the right lumbar sympathetic chain.[1] Significant variation has been reported in ganglia's location, size, and quantity. The number of ganglia varies between 2 and 5, with an average of 3. The ganglia may appear as up to 6 individual ganglia or fused into a single tissue mass. Frequently, there are no ganglia corresponding to the L1 level.[2] 

Neurolysis can be performed to disrupt the sympathetic ganglia at the levels of L2-L4, leading to decreased vasomotor tone and decreased afferent pain signals. This phenomenon explains the symptomatic relief patients experience and the findings of hyperemia of the foot, which often occurs following successful lumbar sympathetic neurolysis due to increased vasodilation and arteriovenous shunting of cutaneous capillary beds.[1] 

Indications

Numerous disorders affecting the lower extremities are treatable with lumbar sympathetic neurolysis, such as complex regional pain syndrome (CRPS), postherpetic neuralgia, and phantom limb pain. From a vascular standpoint, lumbar sympathetic neurolysis has also been useful for patients with severe ischemic rest pain and peripheral arterial disease that is considered non-reconstructable. Patients considered for this procedure often demonstrate significant interruption in quality of life as a result of their symptoms and likely have failed medical management as well as other modalities of treatment.[1] 

Cases of chronic visceral pain (eg, inoperable malignancy) associated with the descending colon and upper portion of the sigmoid colon, kidney, and parts of bladder and ovaries may also benefit from this procedure; more specifically, the hypogastric plexus and ganglion impar are usually the targets.[3][4] Lumbar sympathetic neurolysis has also been used in the treatment of plantar hyperhidrosis.[5] In today's practice, spinal cord stimulation has largely replaced lumbar sympatholysis for many chronic pain indications. 

Contraindications

Strong contraindications include a lack of informed consent and an infection at the procedure site. Relative contraindications include coagulation abnormalities, bleeding dyscrasias such as various platelet dysfunctions, malignancy near the treatment site, systemic infection, bacteremia, and severe cardiac or pulmonary disease.[6]

Equipment

Typically, fluoroscopic guidance requires including a C-arm, fluoroscopy-compatible table, and the required needles and medications.

Technique or Treatment

Lumbar sympatholysis can be performed using radiofrequency ablation (RF), chemical neurolytic agents, and rarely surgery. A plethora of techniques and recommendations have been described for each option. This topic provides an overview of basic techniques, focusing on RF and chemical methods. Fluoroscopy frequently aids sympathectomy procedures, allowing the provider to navigate the bony landmarks and visualize the injected contrast material.

The patient is prone to the fluoroscopy bed in its various modalities for this procedure. Monitors are attached. Anxiolytic agents are an option. Prophylactic antibiotics are not indicated in usual circumstances. Routine surgical time-out is necessary to verify patient identity, procedure, and site. The lumbar region of the patient is prepped in a sterile fashion. Fluoroscopy is used in a posterolateral oblique projection to identify the targeted region(s) in L2-L4. Local anesthesia is administered into the skin and subcutaneous tissue at the needle entry site at the discretion of the provider. Cutaneous temperature is usually monitored before and after at bilateral lower extremities to determine the efficacy of successful sympathetic blockade.[1][7][8]

Chemical Neurolysis

A 15 cm, 20 to 22 gauge needle is entered immediately below the transverse process to target the anterolateral aspect of the vertebral body. The needle is advanced until it reaches the targeted anterior margin of the vertebral body using intermittent biplane fluoroscopy. The needle entry site is estimated at 7 cm lateral from the midline. The proceduralist often “walks” the needle anteriorly and medially into the perivertebral space when they contact the vertebral body as the needle advances. Contrast material is injected after aspiration, looking for a craniocaudal longitudinal spread of the contrast agent in the perivertebral space. Once the correct injection site is confirmed, 3 to 5 mL bupivacaine 0.5% is injected to anesthetize the nerve root before injection of the neurolytic agent (approximately 5 mL of absolute alcohol).[1] Other injectates depending on the patient, situation, and availability, as well as depending on practitioner preference, include lidocaine for the local anesthetic and phenol for the neurolytic.

Numerous techniques for the specifications of chemical neurolysis exist, and it has been shown that a 3-needle approach has superior efficacy while using less volume of the neurolytic agent.[9] If using a multi-needle method, confirming all levels and performing aspiration before injecting the neurolytic agent is critical.

Radiofrequency Thermocoagulation

Denervation is also possible with a percutaneous approach using radiofrequency(RF) thermocoagulation, referred to as RF ablation. The initial setup is comparable to chemical neurolysis, as described above. The anatomical targets are also largely similar; however, specialized needles and radiofrequency probes perform thermocoagulation at the targets.[8] A radiofrequency lesion generator in the closed circuit produces a high-frequency current that produces neurolysis on application to the neural tissue. Important variables that affect the RF ablation technique include electrode size, duration of the lesion, and tissue temperature.[6]

Surgical Sympathectomy

Various surgical approaches usually involve cutting or clipping the sympathetic chain. This procedure is typically at or below L2 to minimize sexual dysfunction side effects and complications that more often occur when performed at higher levels, such as the thoracic region. It is essential to point out that lumbar sympatholysis is not a permanent effect. Interventional radiofrequency or neurolytic approaches typically last up to six months before the nerves can regenerate, while surgical lumbar sympatholysis can have effects lasting up to a few years.

Complications

Complications of performing lumbar sympatholytic can include bleeding, infection, neuraxial injection, intravascular injection, genitofemoral neuralgia, injury to nerve roots, and rarely injury to pelviureteric structures.[1] Genitofemoral neuralgia is the most common complication, with a 5 to 7% incidence following chemical lumbar sympathectomy. Some data suggest a higher incidence when using alcohol instead of phenol. The groin dysesthesia symptoms of genitofemoral neuralgia are usually transient and often resolve within 4 to 6 weeks.[10][11] The risk of genitofemoral neuralgia is reducible by avoiding injection of medications into the psoas muscle, especially at levels L3 and L4, where the intramuscular injection is more common.[9] There are also reports of post-sympathectomy neuralgia, which presents more as a dull ache, and its mechanism remains unclear.

An inadvertent neuraxial injection can have devastating consequences such as total spinal and even death.[12][13] Intrathecal injection of chemical neurolytic medications reportedly causes transient weakness and paralysis, with reports of permanent cases as well.[14][15] 

Unintentional intravascular injection of neurolytic agents can occur, given the proximity of the lumbar sympathetic chain to major vessels such as the aorta and inferior vena cava, as described in the anatomy section. Variations in lumbar vessel anatomy, such as the artery of Adamkiewicz, may also be a factor in inadvertent intravascular injection, resulting in direct toxic or ischemic injury to the spinal cord.[16] These risks highlight the importance of aspiration before injection to avoid accidental intravascular injection of medication.

Clinical Significance

Lumbar sympatholysis can be an effective treatment option for patients suffering from chronic, intractable pain in the lower extremity as a result of various causes such as complex regional pain syndrome, post-herpetic neuralgia, inoperable peripheral arterial disease, phantom limb pain, erythromelalgia, or hyperhidrosis. The relief and symptom improvement from destroying the lumbar sympathetic chain can last several years. It can be performed by chemical neurolysis, radiofrequency thermocoagulation, and surgical sympathectomy approaches. To help provide effective and safe care for patients suffering from these often debilitating conditions, healthcare providers need to understand these techniques and the indications for, contraindications for, potential side effects of, and potential complications of lumbar sympatholysis. 

Enhancing Healthcare Team Outcomes

Lumbar sympatholysis is an invasive procedure and can be associated with serious complications such as paralysis or even death.[12][13] Thus, determining if a patient would be an ideal candidate is critical. Interdisciplinary communication between different medical specialties is often needed to evaluate the patient properly pre-procedure. It is also imperative for the performing provider to understand the anatomy, physiology, and various approaches of the technique to produce improved outcomes and minimize complications and for these ideas to be clearly explained to the patient as well.