Changes in blood flow in the retina, according to a recent study, could explain why some migraine patients have visual disturbances. The findings may provide a long-desired visible marker for migraines that clinicians can use to help with clinical management of the ailment.
Migraine sufferers frequently encounter visual impairments, including blind spots, light sensitivity, pain around the eye, and blurred vision. However, the underlying mechanisms responsible for these symptoms remain foggy.
UCLA Health researchers used a non-invasive imaging technique, known as optical coherence tomography angiography, or OCTA, to visualize changes in the retinal blood vessels of migraine patients both during and between migraine attacks. The imaging was performed on 37 migraine patients with aura symptoms, 30 migraine patients without aura symptoms and 20 healthy patients for a control group.
Decreased Blood Flow
The researchers discovered that blood flow in the retina is reduced during migraine attacks in both migraine patients with and without aura symptoms. Individuals with aura symptoms, on the other hand, had reduced blood flow in particular parts of the retina compared to individuals without aura symptoms.
(A) and (B) show the raw optical coherence tomography angiography image and foveal VFI map respectively in a HC participant. (C) and (D) Show the raw OCTA image and foveal VFI map respectively in a MA participant. (E) and (F) show the raw OCTA image and foveal VFI map respectively in a MO participant.
Credit: Headache. 2023; 00: 1-21. doi:10.1111/head.14654
Furthermore, uneven blood flow in the retinas was linked to which side of the head migraine patients experienced pain.
The results might provide an explanation for the visual symptoms experienced by certain patients and could also serve as a migraine attack biomarker.
The study was led by former UCLA Department of Neurology Clinical Instructor Dr. Katherine Podraza (now of the Hartford Healthcare Headache Center) and coauthored by former UCLA Health research scientist Nitin Bangera, UCLA Goldberg Migraine Program clinical research coordinator Akira Feliz and UCLA Goldberg Migraine Program Director Dr. Andrew Charles of the UCLA Department of Neurology.
Optical Coherence Tomography
Recent developments in optical imaging techniques have permitted high-resolution observation of the retina’s cells and blood vessels at the capillary level. These strategies have been employed in a small number of migraine investigations.
The majority of the studies used optical coherence tomography (OCT) and OCT angiography (OCTA) to analyze retinal layers and vasculature in the interictal stage. Optical coherence tomography uses interferometry and short-coherence-length light to get depth resolutions on the micrometer scale. The light beam is then scanned across the image plane to make two- and three-dimensional pictures from light reflected from biological tissue or other scattering media.
Mixed results have been reported, presumably due to variations in study design, demographics investigated, and variances in technical components of the studies due to the use of different OCT/OCTA machines.
To date, there have been limited studies that used OCTA to evaluate the macular microvasculature during the interictal and especially the ictal phases of migraine.
Migraine with aura (ocular migraine) has been linked to thinning of various retinal layers, including the retinal nerve fiber layer, ganglion cell layer, choroid layer, and increased size of the foveal avascular zone.
Limitations
There were a few constraints on the study that may have impacted the results, as noted by the authors.
Although the study protocol required participants with migraine to have an interictal and ictal retinal scan, not all participants returned during a migraine attack to complete the second scan, which could be a source of selection bias. Furthermore, the number of HC participants was limited due to difficulties with recruitment during the COVID-19 pandemic when this study was completed, and an improvement to the study protocol and analysis would have been to have better age- and sex-matched HCs.
Furthermore, the authors write, the study population was comprised of patients suffering from episodic low-frequency, episodic high-frequency, and chronic migraine. Although the majority of participants had either high-frequency or chronic migraine, the variability in disease severity may have resulted in variability in the results, and further research into the role of disease severity in changes in vascular structure and function in migraine patients’ retinas may be beneficial.
Abstract
Objective: To determine if there are changes in structure and function of the retinal vasculature during and between migraine attacks using optical coherence tomography angiography (OCTA).
Background: Migraine attacks commonly include visual symptoms, but the potential role of the retina in these symptoms is not well understood. OCTA is a rapid, non-invasive imaging technique that is used to visualize the retinal microvasculature with high spatial resolution in a clinical setting. In this study we used OCTA to quantify different features of the retinal vasculature in patients with migraine during and between attacks, as well as in healthy controls (HCs).
Methods: We performed a prospective cohort study of 37 patients with migraine with aura (MA) (median [interquartile range, IQR] age of 37 [14] years, 86% female) and 30 with migraine without aura (MO) (median [IQR] age of 37 [17] years, 77% female) and 20 HCs (median [IQR] age of 35 [7] years, 50% female). Macular OCTA scans were obtained for all participants for the interictal analysis. In 12 MA and eight MO, scans were captured both during and outside of migraine attacks and five HCs had initial and repeat scans. In addition to analyzing the morphology of the foveal avascular zone, we calculated the vessel flux index (VFI), which is an indicator of retinal perfusion and conventional metrics (such as vessel area density) in the foveal and parafoveal regions.
Results: There was a significant difference in the parafoveal VFI in the ictal state between the groups (p = 0.009). During migraine attacks there was a significant reduction in the parafoveal region VFI in MA (−7%, 95% confidence interval [CI] −10% to −4%; p = 0.006) and MO (−7%, 95% CI −10% to −3%; p = 0.016) from their interictal baseline as compared to the change between repeat scans in HCs (2%, 95% CI −3% to 7%). Interictally, there was a mean (standard deviation [SD]) 13% (10%) (p = 0.003) lower blood perfusion in the MA group as compared to the MO group in the foveal region (mean [SD] 0.093 [0.023] vs. 0.107 [0.021], p = 0.003). Interictal analysis also revealed higher circularity in the superficial foveal avascular zone in the MA group compared with the MO group (mean [SD] 0.686 [0.088] vs. 0.629 [0.120], p = 0.004). In addition, interictal analysis of the patients with MA or MO and unilateral headache showed increased retinal vascular parameters consistent with greater perfusion in the eye ipsilateral to the side of the pain as compared with the contralateral eye.
Conclusions: These results indicate that perfusion is reduced in MA and MO in the parafoveal retina during the ictal period. Interictally, the foveal retina in MA has reduced perfusion when compared to the foveal retina in MO. Patients with unilateral headache showed interictal asymmetry of retinal perfusion between eyes. These results indicate that changes in retinal perfusion could be a part of migraine pathophysiology, and that distinct retinal vascular signatures identified with OCTA could represent biomarkers for migraine.
Reference:
- Podraza K, Bangera N, Feliz A, Charles A. Reduction in retinal microvascular perfusion during migraine attacks. Headache. 2023; 00: 1-21. doi:10.1111/head.14654