Researchers think they know the reason why light worsens the already unbearable pain of migraines, even in some blind people.
A report that was published online in January 10 Nature Neuroscience, reveals how visual and pain pathways found in the brain converges to generate this phenomenon.
Though the results are unlikely to help the patients suffering from migraines in the near future, according to Dr. Michael Palm, this study gives a better insight as to the hypothesis and mechanism behind migraine. Dr. Michael Palm, assistant professor of neuroscience and experimental therapeutics and internal medicine at Texas A&M Health Science Center College of Medicine, College Station, and director of the Parkinson’s and Headache programs at Texas Brain and Spine Institute in Bryan says that they are progressing in understanding of this phenomenon.
According to the researchers based at Boston, there exist cells called the thalamus in a part of the brain. This part is where data from the visual system and information from the pain system meet. This anatomic convergence is the first plausible explanation for how it could be that light makes a headache worst, adds Dr. Richard Lipton, the director of the Montefiore Headache Centre and the professor of neurology and epidemiology at the Albert Einstein College of Medicine found in New York City.
Rami Burstein, the senior author of the study, professor of anesthesia and neuroscience at Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, declares that around 85 percent to 90 percent of all migraine patients report having photophobia. This relates to when light worsen the pain.
Burstein acknowledged that they have clueless about how light and pain talk to each other in the brain. Lipton on his side noted that for light to produce pain, those pathways would surely have to join at some particular level.
In order to solve the paradox, the team of researchers studied 20 blind people, all of whom were migraine patients. Six of the participants being studied had no light perception in any way, and their optic nerve was not functioning. These people also did not experience any kind of photophobia.
The remaining 20 participants could discern light and dark and they also experiences photophobia. Burstein explained that this fact revealed to them that the optic nerve is critically needed so as to produce photophobia or exacerbation of migraine by light.
The researchers subsequently discovered that a set of photoreceptors known as melanopsin project onto neurons on the thalamus that also deals with pain signals.
Burstein explains that if they wanted to understand how does light worsen pain, it is imperative that they follow in the brain the pathways that lead from the eye into the brain by making use of the third set of photoreceptors. This connection established, Burstein and his colleagues shifted to animals.
The thalamus represents the brain’s sensory switchboard, which receives sensory signals from various different parts of the body. It then redirects those signals to numerous sensory, motor and cognitive areas of the cortex.
Burstein states that they have been able to identify a new pathway in the found that starts from the eye and goes to the brain areas where the neurons that are operational during migraine attacks are found. He further advanced that the light can actually increase the electrical activity of the neurons that are already active to begin with.
The results of this research should put to ease any thought that migraine patients exaggerate their sensitivity to light, declares Lipton. He adds that this provides an anatomic and physiological basis for a shared experience – that light actually makes the experience of pain worse, not because you have the tendency to whine about it but because an anatomic pathway actually exists that connects the visual system to the pathway that produces headache. He says that the odd bit of clinical symptomatology has indeed a firm foundation in brain science.
Source: Health News
Wed, Feb 3, 2010
Gerontology, Health And Aging