Sensitization: its role in primary headache.

The pathophysiology of the two most common primary headaches, migraine and tension-type headache, is complex and not yet fully understood. Recent animal and human studies examining these headaches indicate that the nociceptive input to the central nervous system (CNS) may be increased due to activation or sensitization of peripheral sensory afferents. The barrage of nociceptive impulses may result in sensitization of second- and third-order neurons in the CNS. In this way, sensitization may play a role in initiation and maintenance of migraine and tension-type headache. It is likely that the effects of established medication for both disorders may be partly due to a reduction in sensitization. Several interesting drugs that counteract sensitization are under development, and targeting this mode of action seems to be a promising way of improving the treatment for these prevalent disorders.