Position and anatomical landmarks
The patient is placed in a supine position with the head slightly hyper-extended. The level of C6-C7 is determined by means of fluoroscopy with the C-arm in the anterior-posterior position. The C-arm is adjusted in a cranial-caudal direction until the vertebral end plates of C6/C7 are aligned.
Procedure
After local disinfection, the skin is anaesthetised using 1% lidocaine, and a needle is inserted at the junction of the transverse process and the corresponding vertebral body of C6 or C7 (Figure 1). After contact with the bone, oblique projection is used to check whether the needle is anterior to the intervertebral foramen.
Figure 1. Stellate ganglion test block AP view: needle position.
If the needle is above this level, contact has been made too early with the vertebral body. The needle has to be replaced more laterally. If the needle is past this level, no contact has been made with the base of the transverse process, and it must be repositioned. Once the needle is in the correct position, a small amount (0.5-1 ml) of contrast dye is injected in order to prevent intravascular injection. The contrast dye must spread cranial-caudally. (Figures 2 and 3)
Figure 2. Stellate ganglion test block AP view: needle position with contrast solution.
Figure 3. Stellate ganglion test block oblique view: needle position with contrast solution.
For a definitive block using RF, a 60-mm, 20-gauge RF needle is combined with a thermocouple probe for thermometry and thermal lesions. After confirmation of the correct needle position by means of fluoroscopy, electrical stimulation is performed at 50 Hz (sensory stimulation) and 2 Hz (motor stimulation) to 1 mA, to ensure that there is no contact with a segmental nerve root (the patient should not feel anything, apart from a faint feeling in the shoulder and/or arm). Then 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.
Complications
- Subarachnoid injection or injection into the vertebral artery. This makes ECG monitoring and placement of an intravenous line prior to performing the procedure mandatory.
- Injection into the thoracic pleural cavity.
- Occurrence of Horner's syndrome caused by the local anaesthetic spreading to the cervical sympathetic trunk.
- Hoarseness can also occur due to spread to the laryngeal recurrent nerves.