| The pain of migraine, as all who suffer from the | | | | diseases of the eye, such as retinosa |
| condition from will attest, is a good deal more | | | | pigmentosa). |
| than a headache. Usually unilateral (affecting one | | | | Recruiting a total of twenty blind migraine |
| half of the skull only), it is a throbbing, pulsating | | | | sufferers who fell into both groups, the study |
| ache often associated with nausea, vomiting and | | | | found that the 'legally blind' individuals consistently |
| excruciating sensitivity to light (photophobia). Many | | | | reported an exacerbation of migraine pain when |
| migraine sufferers can only find some relief after | | | | exposed to light - especially light in the blue and |
| lying in a darkened room. The condition is believed | | | | gray wavelengths. By contrast, patients in the |
| to involve irritation of the meninges (the | | | | 'totally blind' group experienced no worsening of |
| protective membranes which envelop the brain | | | | their migraine pain upon exposure to light. |
| and central nervous system), a development | | | | This finding strongly implicates the optic nerve in |
| which stimulates pain receptors and leads to the | | | | migraine pain and photophobia: in blind individuals it |
| sustained arousal of multiple sensory neurons. A | | | | is functionally inactive, no longer carrying signals |
| group of Harvard scientists have recently | | | | from the retina to the brain. But just how does |
| elucidated the specific neurons which become | | | | the active optic nerve exacerbate migraine pain? |
| activated upon exposure to photons, a finding | | | | Burstein's team suspected that a group of |
| which sheds new light on why the condition | | | | recently discovered retinal cells which contain |
| appears to be aggravated by light. | | | | melanopsin photoreceptors may play a significant |
| As the team of researchers led by Dr. Rami | | | | part - these are the only functioning light |
| Burstein noted, even some blind individuals suffer | | | | receptors left in patients who are legally blind and |
| from migraine, an observation that led them to | | | | are believed to be involved in the regulation of the |
| speculate about how signals from the retina | | | | pupillary light reflex and the regulation of |
| travelling along the optic nerve may be instigating | | | | sleep-wake cycles. |
| or aggravating the pain. For the purposes of the | | | | When the team injected a dye into the eyes of |
| study, the researchers made a distinction | | | | rats and tracked the signals from the melanopsin |
| between individuals who are totally blind due to | | | | retinal cells along the optic nerve to the brain, |
| organic/physical factors (such as glaucoma or | | | | they discovered a cluster of neurons which |
| retinal cancer) and those who are deemed 'legally' | | | | became especially active during migraine. |
| blind. Members of the former group are unable to | | | | Electrodes implanted into these 'migraine neurons' |
| sense light of any kind and are, as a result, unable | | | | showed that light triggered a stream of electrical |
| to sustain the normal diurnal sleep/wake cycle. | | | | impulses which converged. Moreover, the neurons |
| Those in the latter 'legally blind' group, whilst being | | | | remained aroused even after the light exposure |
| unable to perceive images, nonetheless retain a | | | | ceased, a finding which elegantly explains how light |
| degree of light perception, an ability which enables | | | | aggravates migraine, and why lying in the dark for |
| them to continue with a normal sleep-wake cycle | | | | half an hour or so can alleviate same. |
| (they have usually suffered from degenerative | | | | |