The effect of mechanical stimulation of various extraspinal trigger zones in abolition of blockages at C2-C3 and C3-C4 segments is not a permanent property, but it can be suppressed by means of maximum unforced rotations of the head and neck to the right side, while maximum unforced or forced inclination to the right is capable to establish such efficacy in hitherto ineffective zones. Moreover, there exists a complicated system of facilitatory and inhibitory impulses generated by previous stimulation of another zone, on the same or on the opposite side of the body. This preliminary report is intended to draw attention to the existence of these phenomena.

        Key words: head joints, blockages, extraspinal trigger zones, facilitation and inhibition