Optical Coherence Tomography Findings in Migraine

Migraine is a complex, neurological disorder with a genetic basis . It a primary type of headache that characterized by moderate to severe intensity pain associated with fatigue, depression, hyperactivity, nausea, sensitivity to light or sound and other neurological symptoms . The international classification of headaches divides migraine into two main types: migraine without aura and migraine with aura. It affects a large range of individuals, although it more commonly begins in the first few decades of life . According to World Health Organization data, migraine has become the third most common disease in the 21st century . In the meantime, migraine is one of the top ten causes of disability in the world . Based on the WHO reports, Atlas of Headache Disorders and Resources in the World 2011, migraine affects 11% of adults worldwide, and females have three times higher prevalence than males, and it is the leading cause of years lost due to disability in individuals aged 15 to 49 years. Migraine has generally increased in incidence worldwide in recent years, especially in developing countries, possibly with adverse lifestyle changes brought about by rapid urbanization in these regions. There is no consensus on the pathogenesis of migraine, but it is generally accepted that migraine is caused by the combined involvement of nerves and blood vessels . Cortical spreading depression (CSD) has been known to play an important role in the pathogenesis of migraine, which can activate and sensitize the trigeminal vascular system (TGVS), then triggers migraine-associated neurological and vascular responses, and finally induces pain. There are four potential phases of migraine have been identified, including the premonitory phase, aura, headache, and the postdrome, and these are not necessarily linear in occurrence. A better comprehension of the underlying pathophysiology of these phases has led to, for the first time in history, new preventive treatments coming out tailored specifically to treat the mechanism of migraine. Although migraine is a transient phenomenon of cerebral vasoconstriction, transitory and recurrent constriction of the retinal and ciliary arteries may cause ischemic damage to the optic nerve, retina, and choroid in patients with migraine . There is evidence that ganglion cell death in migraine patients may be secondary to alterations in the microcirculation of the optic nerve head or even in the quality of retinal perfusion Though brain and retina come from the same embryologic origin, retina provides a unique window into the nervous system because of having unmyelinated axons and a low concentration of glial cells. That is why retina is called "a relative vacuum" while studying neurons and axons and it can serve as a valuable surrogate marker of neurodegeneration and neuroprotection. Optical coherence tomography (OCT) was developed as a noninvasive technique for acquiring in vivo cross-sectional images during the 1980s and 1990s . Over the last 20 years, OCT has been extensively applied by ophthalmologists to study ocular pathologies, but in these days, it is also being used by neurologists and was studied as a biomarker in various neurologic conditions. There are many studies investigated the altered retinal nerve fiber layer (RNFL) thickness by using OCT in migraine patients but the findings were inconsistent. Some studies reported reduction of RNFL thickness in patient with migraine. While other studies reported normal thickness of RNFL and did not find any statistically significant change in RNFL thickness between different types of migraine and between migraine and control groups. The present study aims to detect changes in RNFL thickness in patients with different types of migraine in comparison to healthy control.