Last week, I told you about Dr. Todd Schwedt's session, The Cerebral Cortex in Migraine: Clinical Considerations, that he presented at the 54th Annual Scientific Meeting of the American Headache Society in June. In that session, we learned that our brain has many regions that may be involved in the pain process and, as we all know, Migraine is not only about head pain. Dr. Schwedt went on to explain that Migraine involves multisensory integration. Human brains can accept many different stimuli and process them at the same time. During a Migraine attack, one can encounter dizziness, nausea, clumsiness, trouble finding words and vertigo in addition to light sensitivity (photophobia), olfactory (osmophobia) sensitivity and auditory (sound) sensitivity. These sensitivities can take place ictally (during) and interictally (between) attacks.
Since pain is only one component of a Migraine attack, there is evidence that Migraineurs may process stimuli - olfactory, auditory and visual to name a few - differently than non-Migraineurs. Visual hypersensitivity or photophobia is a large part of a Migraine attack with almost 90% of Migraineurs suffer with it during an attack. Close to 50% of people with Migraine have persistent photophobia between attacks. Light is not the only thing that Migraineurs can have a hypersensitivity to - it seems motion can over-stimulate too. A small interictal study using alternating bar patterns to visually stimulate Migraineurs activated the visual cortex in all participants and just one non-Migraineur. Another study used a white moving dot pattern on a black background to visually stimulate the subjects, showing the Migraine group had a stronger activation in the middle temporal complex (motion sensitive region) compared to the non-Migraine group. These studies support the idea that Migraineurs have enhanced reaction to light and motion stimuli in addition to having thicker cortex in the visual motion processing centers of the brain compared to non-Migraineurs.
Similar to photophobia, osmophobia is often a Migraine trigger with between 25-43% Migraineurs experiencing it during attacks, while 35% suffer osmophobia between attacks. Many of us are capable of altering our day in hopes to avoid certain smells to stem off a Migraine attack. I do my best to stay away from the garden section in one of the big box stores because the odor will undoubtedly trigger an attack or make my head pain worse. Further, researchers found when they exposed noxious odors to Migraineurs who had osmophobia symptoms during and in between attacks, they had greater activation in the temporal pole region compared to non-Migraineurs, but less activation in the frontal, temporal-parietal and other regions of the brain. They were able to see this using PET scan imaging. Another study compared Migraineurs' responses to odors during a Migraine attack and discovered, when exposed to odors, they had greater activation of several regions that included the amygdala, insular cortex, rostral pons and other areas. Some of same regions that process odors also seem to activate the pain matrix and may be part of the "Migraine generator" (like the rostral pons) which shows how odors can trigger a Migraine attack.
Dr. Schwedt rounded out his session discussing how a Migraineur "co-processes" different stimuli and that Migraine itself is multisensory integration that has "gone wrong." He went on to explain what multisensory integration is:
"sensory-specific brain responses and perceptual judgments of incoming sensory stimuli which concern one sense may be modulated by relations with other senses."
This means, our brains can take in many sensory stimuli (visual, olfactory, auditory and somatosensory) at the same time and process them simultaneously - we don't process one type of stimuli at a time. He thinks this is important because Migraineurs with osmophobia seem to have a higher attack frequency and are found to be photophobic. If Migraineurs are hypersensitive to light they may also be sensitive to odors and have a hyper reactive trigeminal system. One study that measured pain thresholds in a group of Migraineurs who were not experiencing a Migraine and were exposed to bright light, became more sensitive after exposure when their pain thresholds were re-measured. This did not happen in the control group.
There are numerous clear connections between the intensity of Migraine pain and severe photophobia, phonophobia and osmophobia. We also know that Migraines can be triggered by smells, lights, lighting patterns, and sound. The cerebral cortex has been found to be involved in pain processing and a large amount of data that suggest Migraineurs have "atypical" processing of sensory stimuli. Dr. Schwedt suggests that this may directly relate to atypical Migraine characteristics.
Schwedt, Todd, M.D. "The Cerebral Cortex and Migraine." Platform Presentation. 54th Annual American Headache Society Scientific Meeting. June, 2012.
Photo: National Institute of Mental Health, National Institutes of Health, Department of Health." Brain Basics." Last reviewed November 9, 2012.
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© HealthCentral Network, 2012.
Last updated November 20, 2012.