The patient lies in the prone position on the operating table with a pillow under the abdomen to flatten the lumbar lordosis. With the C-arm, level L2-L4 is identified in AP view. The C-arm is positioned in a cranial caudal direction until the vertebral end plates are aligned. Then the C-arm is rotated laterally until the distal end of the transverse process projects in line with the lateral border of the corresponding vertebral bodies of L2, L3 and L4. After local disinfection, the skin is anaesthetised using 1% lidocaine.
A needle is inserted in tunnel vision until the front of the vertebral bodies has been reached (Figures 1 and 2). The lateral view is used to ensure that the needle does not pass the anterior border of the corpus vertebrae. Moreover, an AP view is used to ensure that the tip of the needle projects over the facet joint of the spinal column.
Figure 1. Lumbar sympathetic diagnostic block injection point: oblique view.
The sympathetic trunk can be reached by a single needle approach at the vertebral body of L3 or by a multiple needle approach towards the vertebral bodies of L2, L3 and L4. If there is a good outline of the contrast at the start of the single needle approach at L3, there is no need for a multiple needle approach. In both approaches, a small amount (0.5-1 ml) of contrast should be injected. Injection of too much contrast makes repositioning of the needle more difficult. In the AP view, the contrast should be visible as a cloud in front of the vertebral body, but not laterally. In the case of a streaky lateral spread of the contrast, the needle could be in the psoas muscle compartment and should be inserted more deeply.
Figure 2. Lumbar sympathetic trunk diagnostic block injection point: oblique view with needle in tunnel vision.
Using a lateral view, a string will be seen running along the anterior lateral aspect of the vertebral body (Figure 3). A 20-G, 150 mm needle at the level of L3 is used for a test block. For RF treatment, a 20-G 150 mm RF needle with a 10-mm non-insulated tip is used, combined with a thermocouple probe for thermometry and RF treatment. Consideration can be given to blocking at only two levels, L3 and L4. After confirmation of the correct position by means of fluoroscopy, electrical stimulation is carried out using, consecutively, 50 Hz (sensory stimulation) and 2 Hz (motor stimulation) to 1 mA, to ensure that there is no contact with a segmental nerve root (patient should not feel anything, apart from a faint feeling in the abdomen). At each level, 0.7 ml 1% lidocaine is injected, after which a thermal lesion is carried out for one minute at 80°C. This procedure can be repeated if necessary.
Figure 3. Lumbar sympathetic trunk diagnostic block injection point: lateral view with needle in tunnel vision.
- Due to inhibition of the sympathetic system, vasodilatation and/or oedema of a leg can occur.
- Orthostatic hypotension.
- Neuropathic pain due to damage to the ilioinguinal or genitofemoral nerve.
- In bilateral lumbar sympathetic (in two treatment sessions), male impotency can occur.