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Complications of Lumbar Sympathetic Block

E. Alp Yentür MD, FIPP

Manisa Celal Bayar University, Manisa, Turkey

Introduction

Lumbar sympathetic block (LSB) is a commonly performed procedure for the diagnosis and treatment of various clinical conditions. It can be performed by local anesthetics, neurolytic agents or a radiofrequency (RF) lesion generator, and the procedure can be applied according to the experience and education of the clinician by using fluoroscopy, computed tomography (CT), and ultrasound (US).

Anatomy

Lumbar Sympathetic Ganglia

The lumbar sympathetic chain is located on the anterolateral surface of the lumbar vertebral bodies and medial to the psoas muscle. The aorta and inferior vena cava are anteriorly located to the lumbar sympathetic ganglia. Its boundaries are the vertebral bodies and fascia of the psoas muscle posteriorly and the big vessels anteriorly. Additionally, the lumbar sympathetic chain lies anterior to the lumbar segmental vessels, whereas the kidney and ureter are postero-laterally located.

In general, the L1 and L2 ganglia tend to be fused and, in most cases, there are four ganglia on each side. The most dense portion of lumbar sympathetic ganglia are found in L2 and L3, therefore, LSBs are most commonly performed along the lower third of L2 or the upper third of L3.

Genitofemoral Nerve, Lateral Femoral Cutaneous Nerve

The genitofemoral nerve is the sensory nerve most at risk at LSB. It arises from the L1 and L2 spinal nerves, passing the psoas muscle and arrives the ventral surface around L3 body. At this point, the nerve perforates the psoas fascia and splits into the femoral and genital branches.

A second nerve that might cause problems is the lateral femoral cutaneous nerve. This nerve arises from the spinal nerves of L2 and L3 and runs between the superficial and deep portion of the psoas muscle.

Indications

There are mainly three clinical group of indications for LSB:

Pain syndromes
- – CRPS I and II
- – phantom limb pain
- – acute herpes zoster and postherpetic neuralgia
- – renal colic or urogenital pain
- – peripheral neuropathic pain and diabetic polyneuropathy
- – cancer pain with sympathetic component.
Circulatory insufficiency in the lower limbs
- –peripheric vascular diseases
- –embolic occlusions
- –frostbite
- –diabetic gangrene or ulcers.
Hyperhidrosis.

Contraindications

Local or systemic infection
Coagulation abnormalities
Patient’s refusal.

Technique

Currently LSB can be performed by using fluoroscopy, ultrasound (US) or CT and, during this procedure, neurolytic agents or an RF lesion generator have been used.

Fluoroscopy Guided Technique

The paravertebral approach under fluoroscopic guidance is the most commonly used technique.

Chemical Neurolysis

Under fluoroscopic guidance, the patient is placed prone, with a pillow under the lower abdomen to straighten the lumbar lordosis. First, the targeted L2 and L3 vertebrae are identified by AP imaging and the fluoroscope’s C-arm should be repositioned such that the end plates of vertebra bodies are aligned. Then, the C-arm is placed in the lateral oblique plane, approximately 15–20^o from the sagittal plane, until the lateral edge of the transverse process is aligned with the lateral aspect of the vertebral body to avoid the transverse process during insertion of the needle. At this position, a 15 cm needle is advanced toward the anterolateral edge of the vertebra, via a tunnel vision technique (Figure 35.1a). Once the route of the needle has been confirmed, the C-arm should be returned to an AP position. At this view, the needle tip should be at the pedicle level (Figure 35.1b). Then, at lateral image, the needle tip should lie at the anterior margin of the vertebral body. Once in the correct position, contrast material should be injected.

**Figure 35.1** **(a)** and **(b)** Oblique view. Tunneled vision technique.

(b) For successful LSB, the contrast should spread along the longitudinal axis without any lateral or posterior extension, or any psoas muscle shadow (Figures 35.2a,b and 35.33a–f). At this point, be careful that transient patterns may suggest vascular uptake [1]. Also, for neurolytic injections, a smaller volume (1–2 ml) is recommended to decrease the possibility of posterior spread. This may reduce the likelihood of neuralgia.

**Figure 35.2** Correct positioning of the needle tip and contrast spread at AP (a) and lateral view (b).

**Figure 35.3** **(a–f)** Incorrect positionings of the needle tip and spread of contrast.

Radiofrequency Thermocoagulation

For radiofrequency thermocoagulation (RFT), the technique is similar to chemical neurolysis, however, a specialized 15 mm RF cannula with a 10 mm active tip is used for thermocoagulation. The only difference is that ablations should be performed at least at two or three successive levels. Once the needle-tip position is confirmed, sensory and motor testing should be done. If paresthesia is elicited in the groin at levels L2 and L3 during sensory stimulation (due to its proximity to the genitofemoral nerve) or motor response in the lower extremity, the electrode must be repositioned. If no response is obtained, RF ablation can be done at 80^oC for 90 seconds [2].