Migraine can manifest as a wide range of neuro-ophthalmic symptoms. In recent years, research on migraine photophobia has made great strides, while the accepted definition of ophthalmoplegic migraine has been questioned.
OJAI, CA—Migraine can be the cause of symptoms ranging from cranial nerve palsy to static-like visual effects to weeks of pupillary dilation, said Deborah I. Friedman, MD, MPH, Professor of Ophthalmology and Neurology at the University of Rochester School of Medicine in New York. She described the pathology and treatment of migraine’s neuro-ophthalmic manifestations at the Fourth Annual Meeting of the Headache Cooperative of the Pacific.
Ophthalmoplegic Migraine
The classification of ophthalmoplegic migraine, in which a waning headache is followed by cranial nerve palsy lasting from days to weeks, may require expansion, according to Dr. Friedman. As the condition often has secondary causes that can be treated with steroids, it is currently classified as a cranial neuralgia. But some cases may truly be attributable to migraine, she said “If there’s a secondary cause, okay, there’s a secondary cause,” said Dr. Friedman. “But not everybody has an abnormal MRI. And some patients have a lifetime full of recurrent episodes and third-nerve palsy and headache that are very, very stereotypic.”
She proposed two categories for patients with ophthalmoplegic migraine symptoms. “One category would be patients who really do have ophthalmoplegic migraine that’s migraine, and the criteria would include spontaneous resolution,” Dr. Friedman said. “A second category would be patients who have a secondary cause that resolves with steroids or who have an abnormality on their MRI scan.”
Photophobia
Photophobia, an abnormally heightened sensitivity to light or worsening of headache with exposure to light, seems to be an intrinsic property of migraine, Dr. Friedman said. In a recent study, control subjects were able to habituate to increasing degrees of heat and light, while patients with migraine became increasingly uncomfortable. Other research suggests that migraine photophobia is caused by melanopsin-containing retinal ganglion cells, which mediate light input. These cells converge in the thalamus with dura-sensitive neurons, which mediate pain, and then project to various parts of the cortex.
Eyeglasses with a rose-colored tint called FL-41, as well as yellow-tinted glasses for indoor use and amber-tinted glasses for outdoor use, can be useful for alleviating photophobia, Dr. Friedman said. In contrast, she warned, the constant use of very dark glasses can worsen the problem.
“The retina adapts to being in darkness all the time,” said Dr. Friedman. “It’s just like spending your life in a dark room or a movie theater and then trying to go out into the real world. I tell my patients to ease out of dark glasses, switch to amber tints, and then gradually lighten the tint.”
Migraine Aura
Migraine aura can manifest as positive symptoms, such as streaks, flashes, and zigzag lights, or negative symptoms, such as vision loss, grey-out of vision, and visual field defects. These symptoms correlate with cortical spreading depression, an intense depolarization of neuronal and glial membranes characterized by a loss of membrane resistance.
Dr. Friedman and a colleague are currently studying the characteristics of migraine aura in 126 patients who experience the phenomenon. Of these patients, 50% described an image that starts in the periphery of vision and then moved inward, 56% described a moving image, 66% described a shimmering image, 40% described an image in color, and 20% described an image that is sometimes in color and sometimes in black-and-white or silver-and-white.
Visual Snow
Visual snow is a persistent, positive visual phenomenon of unknown origin that looks like television static or transparent squiggles. As patients with the problem tend to be observant, fastidious, and bothered by busy environments or flickering images, they may have some type of hyperexcitability that makes them visually allodynic, noted Dr. Friedman. It would be interesting to investigate whether drugs aimed at attention deficit disorder can be used to treat visual snow, she said.
At present, though, most cases of visual snow are “probably impossible to treat,” Dr. Friedman said. “You can try every anticonvulsant known to mankind and it doesn’t work.”
Retinal/Ocular Migraine
Retinal migraine, also called ocular migraine, involves visual symptoms in one eye. As with regular migraine aura, it can involve positive or negative symptoms.
“I find that the term ‘ocular migraine’ tends to be misused by pretty much everybody, especially ophthalmologists,” Dr. Friedman said. “Patients who have isolated aura with no headache are told, ‘Oh, you have ocular migraine.’ But true retinal migraine or ocular migraine is a monocular visual phenomenon.”
Although diagnosis requires the presence of headache and reversible symptoms, some patients with monocular symptoms have no headache or develop a permanent field defect in one eye.