In a fascinating presentation at the 54th American Headache Society Scientific Meeting this past June, Dr. Todd Schwedt said, "Migraine is a chronic disorder with episodic manifestations." It was refreshing to hear a Migraine specialist confirm this -- for quite some time it was thought that Migraine was vascular in nature. We now know it's a genetic neurological disease thought to be caused by a cascade of events and overly excited neurons in our brains. These neurons are easily triggered by certain stimuli that include changes in the weather, hormones, dehydration, sleep issues and certain foods. Pain can be a major component of a Migraine attack, but certainly not the only one. We are just beginning to learn which areas of the brain are connected with this. In his presentation, Dr. Schwedt discussed the areas affected by Migraine, the role played by each and how Migraineurs may have different ways of processing pain compared to those who don't have the disease.
In his session, The Cerebral Cortex and Migraine; Clincial Considerations, Dr. Schwedt explained the brain is so complex that there are many different "regions" involved during the pain process. He referred to these regions as the pain "matrix," including the posterior insula, amygdala, prefrontal cortex, hippocampus and temporal cortex, where each is responsible for a specific job in our body. Dr. Schwedt thinks this "matrix" may play a role in pain activation. But what do these regions, have to do with Migraine?
- The posterior insula is responsible for the sensory discriminative part of our brains and determines the location, intensity and modality of pain. Migraineurs may have lower pain thresholds during attacks and some have lower thresholds between attacks. An interictal (between attacks) study in both episodic and chronic Migraineurs used heat (applied to the arm and forehead) to show that it took less heat to cause pain in these groups than in the non-Migraine group, indicating they may have atypical pain processing in this region. Other data shows the cortex of Migraineurs may be thicker than in non-Migraineurs.
- The amygdala here refers to the affective motivational domain and determines our emotional response to feeling pain, fear of pain and pain avoidance. Dr. Schwedt reported he sees many Migraineurs in his practice that live in day to day fear of having a Migraine attack, which can substantially increase disability. A study using functional imaging showed when Migraineurs read pain-related words like stabbing, searing and burning, they were able to activate several regions of the pain matrix. An interesting item from the study turned up: althouth both the control and Migraine groups were able to activate these regions, the Migraine group had greater activation of the affective motivational regions. This may indicate that Migraineurs have a bigger emotional response when thinking about pain.
- The prefrontal cortex is the cognitive domain when it comes to pain processing - when we expect pain, pain memory and our attention to pain. It seems when we expect pain, it may be worse than if we weren't expecting it and we can also decrease our pain threshold for our next attack. Some Migraineurs may create a self-fulfilling prophecy (a positive or negative expectation regarding events that may affect the outcome) of pain. Dr. Schwedt reported that about 50% of Migraineurs think about Migraine even on pain-free days. The placebo and nocebo effects may come into play in this instance, in that, when we think something will happen - it probably will. Many Migraineurs have said, "I've tried every medication that any doctor has given me and nothing has worked and I don't think anything will ever work." There may be a physiological reason for this, but many times our cognitive processing may be involved.
- The temporal cortex refers to the integrative domain - this area helps integrate other pain domains and multisensory integration, which is the way our brain senses many things the same time. During a Migraine attack, we can experience phonophobia, photophobia and osmophobia at the same time, among other things.