Fig. 1From: Myofascial trigger points in migraine and tension-type headacheThe bottom-up model states that increased peripheral nociceptive transmission sensitizes the central nervous system to lower the threshold for perceiving pain while the top-down model suggests these changes are already present in central nervous system. In relation to myofascial trigger points, a bottom-up model would suggest that increased nociceptive transmission from myofascial trigger points lowers the threshold for perceiving pain (red). A top-down model would suggest that central sensitization may contribute to the occurrence of myofascial trigger points rather than the other way around (blue)Back to article page