Position and anatomical landmarks
Infiltration of the greater and lesser occipital nerves is performed according to the anatomical landmarks described by Vital and Becser (see Figure 1).
Figure 1: Anatomical landmarks of the Nervus Occipitalis Major and Minor according to Vital and Becser.
Procedure
The surrounding area is disinfected and covered with sterile drapes. A needle (22-G) is inserted (under ultrasound guidance) until there is contact with bone. The thermocouple is connected to the needle. Location of the nerve is confirmed when the patient experiences reproducible paresthesia in the occipital region by stimulation with 50 Hz, 0.5 V. Then, a pulsed radio-frequency current of 45 V lasting for 120 seconds is administered without preceding local anaesthetic. The maximum temperature should not exceed 42°C, but if this occurs the output should be reduced. If necessary, a second treatment period of 120 seconds can be administered if the impedance is above 500 Ω, prior to injection of 1 ml NaCl 0.9% solution.
Complications
- The most serious complication of the injection is infection.
- Small subcutaneous bleedings may result in a temporary increase in pain after the injection.