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.

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.

(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.

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].