Greater occipital nerve block modulates nociceptive signals within the trigeminocervical complex.

These data suggest that the functional inhibition of the occipital nerve block on trigeminal nociceptive activity is likely to occur at the C2 level where the occipital nerve enters the trigeminocervical complex and converges on the same central nuclei before the signal crosses the midline at that level and is then transmitted to higher processing centres.