Lumbar Sympathetic Block

Introduction

• The autonomic nervous system consists of two primary divisions: the sympathetic and parasympathetic systems. The sympathetic trunk comprises paravertebral ganglia that run from the base of the skull to the coccyx. The sympathetic trunk plays a major role in maintaining homeostasis in conjunction with the parasympathetic trunk.^1,2
• The sympathetic trunk is located along the anterolateral aspect of L1-L4 vertebral bodies. The preganglionic neurons exit the spinal cord via the white rami of the ventral roots of L1-L4 spinal nerves, and the postganglionic neurons extend distally to innervate specific sites along the lower extremities. The inferior vena cava lies anterior and to the right of the sympathetic trunk; the abdominal aorta lies anterior and to the left of the sympathetic trunk.^1,2
• The lumbar sympathetic block targets the sympathetic chain between L1 and L4 by disrupting the nerve supply to the lower extremities. The block is most commonly performed in the lower third of L2 or the upper third of L3, as the densest portion of the lumbar sympathetic ganglia is located at these levels. This procedure helps treat lower extremity neuropathic pain conditions and sympathetic-mediated causes of pain.^1,2

Indications

• The primary indication for lumbar sympathetic blocks is for the treatment of neuropathic and sympathetic-mediated pain disorders refractory to conservative management. Such conditions include:
  • CRPS
    • CRPS involves dysregulation of the central and autonomic nervous systems in patients with sustained injury to soft tissue or peripheral nerves. Clinical features include allodynia, hyperalgesia, vasomotor dysfunction, swelling, edema, and trophic changes. Optimal treatment involves early diagnosis and time-dependent interdisciplinary treatment, so a lumbar sympathetic block should be considered sooner rather than later, especially in a patient who has reached a plateau following intensive rehabilitation and pharmacotherapy.^1-3
  • Chronic occlusive arterial disease (COAD) (including critical limb ischemia)
    • COAD involves a reduction in blood flow to the lower extremities, which often manifests as intermittent claudication and progresses to severe, persistent pain at rest. Lumbar sympathetic blockade can be a viable option in patients for whom revascularization may not be feasible secondary to medical comorbidities. In addition to reducing pain, lumbar sympathetic blocks may improve wound healing and blood flow and potentially delay limb amputation.^2,4
  • Diabetic neuropathy
    • Diabetic neuropathy involves microvascular dysfunction secondary to chronic hyperglycemia, contributing to the perpetuation of neuropathic pain. Lumbar sympathetic blocks can decrease the patient’s pain by reducing sympathetic outflow and improving vascular circulation.²
  • Phantom limb pain
    • This is a phenomenon where pain is perceived from an amputated limb. Although the exact mechanism is poorly understood, multiple case reports have indicated that lumbar sympathetic blocks can offer pain relief in amputee patients.^2,5
  • Vasospastic disorders (including Raynaud’s phenomenon)
    • Lumbar sympathectomy can offer pain relief, reduce vasoconstrictor tone, and improve circulation to the ischemic region.^1,2
  • Hyperhidrosis
    • Plantar hyperhidrosis is a condition characterized by excessive sweating of the feet due to an overactive sympathetic nervous system. In patients who fail to respond to conservative measures, lumbar sympathectomy has shown a high success rate in achieving anhidrosis.²
  • Postherpetic neuralgia secondary to zoster
    • Several case reports have shown improvement in pain, quality of life, and function following lumbar sympathetic block in patients with postherpetic neuralgia secondary to zoster.¹
  • Cancer pain⁶

Contraindications

Lumbar sympathetic blockade is contraindicated in the following scenarios:

• Conditions with altered coagulopathy or chronic anticoagulation that cannot be stopped
• Allergic reactions to injected medication
• Poorly controlled diabetes
• Poorly controlled heart disease
• Patient refusal

Techniques

• Prior to positioning, standard American Society of Anesthesiologists monitors are recommended. This includes continuous oxygen saturation, electrocardiogram, and intermittent blood pressure monitoring, along with intravenous access. Baseline temperatures of bilateral lower extremities should be obtained and recorded.²
• The patient should be positioned prone, with the fluoroscopic imaging projector adjusted so that the superior end plates of L2-L3 are aligned. From here, the fluoroscope’s C-arm imaging projector should be rotated ipsilaterally in the oblique plane until the transverse process is superimposed with the lateral border of the L2-L3 vertebral body.^1,2
• The needle entry point is along the inferior third of the anterolateral border of the L2 vertebral body or superior to the mid-third of the anterolateral border of the L3 vertebral body. The needle should be advanced towards the anterior aspect of the vertebral body in the oblique view and “walked along” until contact is made with the anterolateral border of the vertebral body.^1,2,6
• The fluoroscopic C-arm should then be repositioned laterally to verify the needle depth and confirm that the tip is at the anterior vertebral line.^1,2
• Following negative aspiration for air, blood, or cerebrospinal fluid, approximately 1-2 mL of contrast should be injected to ensure proper positioning and adequate flow with minimal resistance. Contrast should be visualized anterior to the vertebral body as a “cloudy” craniocaudal spread between L1-L3.^1,2
• Upon confirmation of proper superior and inferior spread of the contrast, the medication (which may consist of local anesthetic, ethanol, or botulinum toxin) can be injected to complete the lumbar sympathetic blockade. The needle can then be removed, pressure applied to the entry point, and covered with a dressing.^1,2
• The patient will likely experience increased flushing or warmth through the lower extremity on the injected side secondary to vasodilation. Temperature monitoring will indicate a two-to three-degree Celsius increase in temperature following successful blockade.^1,2

Adverse Effects and Complications

• The most common complications can include bruising, bleeding, swelling, and soreness at the site of injection. This is generally self-limited and resolves within hours to days of the procedure. Some patients may report dizziness, headache, and transient numbness and weakness in the leg on the injected side.^1,7,8
• More serious complications may include infection, allergic reaction, intravascular injection, visceral injury, or intralymphatic injection, although these occurrences are rare.^1,7,8
• Anterior thigh pain secondary to genitofemoral nerve and lateral femoral cutaneous nerve damage may occur in some patients, though it is also rare.^1,7,8