Pain reflexes in the clinical assessment of migraine syndromes

Nociceptive flexion reflexes, RIII reflex in particular, have been demonstrated to be a useful tool for pain research in humans, since the threshold of RIII reflex is that of pain. In this study a reduction of RIII reflex threshold, strictly related to the severity of the disease, is described in migraine with interval headache (MIH), that is considered a severe and evolutive form of common migraine (CM). These abnormalities were not found in CM or in other chronic pain conditions, i.e. chronic tensive headache (CTH), suggesting that this electrophysiological parameter may be useful in the clinical assessment of primary headache. Moreover, the administration of amitriptyline, a drug producing analgesia mainly by blocking serotonin uptake, was able to markedly increase the RIII reflex threshold in MIH. This fact supports the hypothesis that an impairment of serotoninergic antinociceptive system may exist in this type of headache. A significant correlation between percentage increase in RIII reflex threshold and reduction of PTI was also observed after amitriptyline treatment, indicating that pain reflex may be used for predicting treatment response in migraine.