Together, these changes could one day represent migraine biomarkers, authors say. The study was published online in Headache.
“We’re always looking for a biological marker for migraine,” said Alan M. Rapoport, MD, a clinical professor of neurology in the David Geffen School of Medicine at the University of California Los Angeles and past president of the International Headache Society. Researchers have identified many parameters that make people more likely to experience migraine, he said, but there remains no smoking gun. “We do not yet have a diagnostic test.”
Investigators have long been examining ocular vascular supply, added Dr. Rapoport, who was not involved with the study, because the eyes, visual system of the brain, and migraine are closely related. “But no one has ever figured out that one could use anything related to the eye as a definitive diagnostic test. This study was interesting because researchers used a very advanced technique to see if there are changes in the vascular supply to the eyeball during migraine.”
During Attacks
Study investigators prospectively enrolled 37 patients diagnosed with migraine with aura (MA), 30 with migraine without aura (MO), and 20 healthy controls. All subjects underwent macular OCTA for interictal analysis. A total of 20 patients with migraine (12 with MA and 8 with MO) underwent repeat scans during migraine attacks, and 5 control patients had repeat scans.
Compared with interictal measurements, significant parafoveal reductions in vessel flux index, an indicator of retinal perfusion, occurred in both the MA and MO groups during migraine attacks: –7% (95% CI, –10% to –4%; P = .006) and –7% (95% CI, –10% to –3%; P = .016), respectively, versus controls (2%, 95% CI, –3% to 7%).
The fact that migraine attacks resulted in reduced blood supply to the retinal region responsible for central vision is intriguing, said Dr. Rapoport, because sufficient reductions in blood supply there could result in blurred vision or other visual difficulties that might be mistaken for a true aura. “Many patients describe blurred vision related to their migraine headaches which do not usually qualify for an aura diagnosis,” he said.
Diagnostic criteria for MA, which afflicts around one third of people with migraine, include visual aberrations lasting at least 5 minutes and no more than 60 minutes. Visual aberrations average about 20-25 minutes, said Dr. Rapoport. “And we don’t usually accept blurred vision.” For most people who experience ictal blurred vision, he added, the phenomenon only lasts a short time and is not considered an aura.
More typical visual manifestations of MA include zigzag lines in an overall crescent shape that may blink, have bright edges, grow and shrink in size, and/or move across the visual field; patients also may have blind spots or distortions (e.g. far away vision, smaller or larger vision, or kaleidoscopic fractured vision). Nevertheless, said Dr. Rapoport, the study may shed light on why some people experiencing a migraine attack may suffer a brief bout of blurred vision and mistakenly report experiencing an aura.