Between Attacks
Comparing the two migraine groups interictally showed statistically significant differences in macular structure and function. Compared with the MO cohort, the MA cohort had higher circularity (mean [SD] 0.686 [0.088] vs. 0.629 [0.120] MO, P = .004), as well as a 13% (SD ± 10%, P = .003) lower foveal vessel flux index. “Not only is perfusion lower in both types of migraine during the attack,” said Dr. Rapoport, “but between attacks, people with MA had a lower blood supply to the retina than those who had MO.”
Unilateral Migraine
In a subset of patients (14 with MA and 12 with MO) whose headaches occurred unilaterally, investigators found retinal vascular parameters consistent with greater perfusion in the ipsilateral eye versus the contralateral eye. The significance of these findings remains unclear, Dr. Rapoport said, because circulatory findings revealed by CAT or MRI scans of patients with unilateral headaches are often normal or involve complex changes or mild edema on the side of the headache. The visual cortex on either side receives input from both eyes, he added.
Study Limitations
Authors acknowledged several study shortcomings. Most notably, COVID-19 restrictions resulted in a small sample size, and several patients (excluded from analysis) failed to return for repeat scans during migraine attacks. The study included patients with migraine attacks of varying frequency, and a handful of patients used acute rescue medications before undergoing ictal scans.
“If a future study corrected all these shortcomings,” Dr. Rapoport said, “the results might be more impressive and even more significant.” Based on these results alone, he said, it would be premature to pronounce OCTA-derived measurements of retinal perfusion and related parameters as future migraine biomarkers.
“But it’s a good start. If this hasn’t been done before, in quite this way, this is a very interesting study which, when repeated, should lead to even more significant findings.”
For now, the paper should remind practicing neurologists to dig deeper when patients complain of visual problems during migraine attacks. “It might be blurred vision for just 3 minutes,” he said. “Some patients may be calling it an aura, or the doctor may be thinking it is an aura because they’re not digging for further information in the history. We may now have a window into decreased retinal perfusion during a migraine attack and why some patients have blurred vision.”
The study was funded by the Amgen and the Baldwin Foundation. Dr. Rapoport is editor-in-chief of Neurology Reviews but reports no relevant relationships with the funders of this research.