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Migrainous Infarctions: Pathophysiology, Prevention, and Treatment
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Abstract
Migraines and strokes are prominent conditions in the United States, with migraines
affecting 10-12% of the population and new or recurrent strokes occurring in 795,000 people
annually.1,2 Migrainous infarctions, in which an ischemic stroke coincides or is a result of a
migraine aura, account for a portion of this percentage. How these infarctions occur, the
pathophysiology, possible risk factors which contribute to their incidence, and how they affect
the practice of physician assistants, will be discussed and expounded upon herein. Physician
assistants may encounter these conditions frequently in practice. Thus, it is important to
understand their pathophysiology, prevalence, characteristics, treatments, and prevention. In
doing so patient health may be optimized and the occurrence of these conditions may be reduced.
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Introduction
Present day healthcare is constantly changing – from technological advances such as the
artificial heart ―Big Blue‖ to fundamental interactions with patients as seen in the utilization of
the pain scale. Yet, while healthcare continues to change, the diseases and conditions which
make it a necessity in society seem to remain prominent.
Migraines and strokes are prime examples of such conditions and they are ever prevalent
in the United States, with 25% of women and 8% of men suffering from debilitating migraines,3
and 1 out of 18 deaths occurring from strokes, which is ranked as the fourth leading cause of
death in the United States.2 With such statistics, it is important for physician assistants to
understand the mechanisms of these conditions, how they’re linked, and how best to treat them.
While the delivery and management of healthcare is constantly changing, the need for patient
care is constant.
Migraines are a condition affecting a certain population of people and are a debilitating
set of symptoms i.e. pain, disorientation, nausea, vomiting, and increased sensitivity to light,
sound, or touch, which cause great discomfort. Thus, migraines are designated as a syndrome,
defined as a set of symptoms arising from a common cause.4 During the past decade, there have
been many medical inquiries to explore and explain the relation of migraines to strokes. It has
been recognized that strokes can occur in the presence of typical migraine attacks. The
International Headache Society created the term ―migrainous infarction‖ to describe the event –
also known as a ―migraine-induced stroke‖. For a stroke to be considered a migrainous infarction
it must meet the following criteria: it must be preceded or coincide with an aura, it must be
similar in intensity to previous attacks, the aura must persist for hours or days, the stroke must be
seen on a computerized tomography scan (CT scan) or magnetic resonance imaging (MRI) scan,
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the stroke must be located in a part of the brain correlating to the presenting symptoms, and all
other possible causes of a stroke must be ruled out.5
A stroke is the blockage of an artery or vessel by a blood clot, or the breakage of either
which disrupts blood flow to an area of the brain.6 Deprived of oxygen and blood supply, the
brain’s cells begin to die. If the depravation persists long enough it will result in brain damage
and even death. There are many risk factors for stroke, one of which has been recently affirmed –
migraines with auras.
As stated above, migraines are a debilitating syndrome which can present with a wide
variety of symptoms, some of which are increased sensitivity to light, touch, or sound known as
migraine variants. When increased sensitivity to external stimuli or visual auras present before or
during a migraine it is known as a migraine with aura (MA). 15-20% of people suffering from
migraines present with auras while nearly 80% do not.7 This subpopulation is at an increased risk
for migrainous infarctions.6 This knowledge is invaluable to healthcare providers as well as
patients because it can help identify those who are at an increased risk of a fatal stroke.
Migrainous infarctions have been linked to ischemic strokes where blood flow is greatly
reduced by the blockage or breakage of an artery or vessel in the brain. Migrainous infarctions
mostly occur in the posterior circulation. The direct pathophysiology behind this event is still
relatively unknown. There are risk factors which are believed to lead to, if not directly cause,
migrainous infarctions such as patent foramen ovale and right-to-left-shunts in addition to
migraines with auras, which are believed to be secondary to underlying problems resulting in
poor circulation.8
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Pathophysiology of Migranous Infarctions
Migraine auras (MA) can present with visual scotomas or blind spots. These can occur
before or during the migraine. Upon observation of people suffering from migraine auras using a
magnet encephalogram (MEG), cortical spreading depression (CSD) waves were seen. These
CSD waves have a similar propagation velocity to the visual scotomas present in migraine auras
and confirmed the theory that CSD was the underlying mechanism in this subpopulation of
migraines.9, 10 CSD is found to cause a depression of neuronal activity which spreads from the
posterior (occipital) portion of the brain through the cortex and other gray matter areas.11 This
reduction in neuronal activity can result in hypoxia (a decreased level of oxygen), ischemia
(reduced blood flow), and infarction. CSD originating in the occipital lobe of the brain explains
the occurrence of migraine auras presenting with visual scotomas and other sensory disruptions,
and also provides a mechanism as to how migrainous infarctions can occur – most of which take
place in the posterior circulation,8 where CSD originates. Spreading depression similar to CSD
has even been documented in patients with post-ischemic strokes.12
While CSD may be the pathophysiology of migrainous infarctions, there are a number of
risk factors contributing to strokes. These risk factors – patent foramen ovale and right-to-left
shunts – affect blood flow to the brain and thereby stimulate CSD. Migraine auras also have a
higher prevalence in conjunction with these two risk factors.13 A general mechanism has not
been directly correlated to how these two risk factors cause CSD and thus stroke. Paradoxical
embolization is believed to be the reason.1 A paradoxical emboli is a condition where emboli
originating from the venous system enter the arterial circulation via an abnormal communication
between the heart’s chambers i.e. right-to-left shunt and patent foramen ovale, culminating as a
stroke.14 A study completed in 2010 found that CSD is readily triggered by intravascular cerebral
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microemboli.1 Michael A. Mosokowitz, MD, one of the researchers participating in the study,
said ―another scenario, more relevant to migraine with aura, is that these particles get stuck for
ultra-short periods of time, but long enough to depolarize surrounding tissue and trigger cortical
spreading depression. Unfortunately, another scenario, and this also occurs in patients harboring
a patent foramen ovale, is that embolic particles may stay within the blood vessel and cause an
infarct.‖15
Risk Factors
The foramen ovale is an opening connecting the right and left atria, needed for blood to
bypass the lungs prenatally. Patent foramen ovale is a congenital defect where the bypass does
not close resulting in a right-to-left shunt. This condition is significant because patent foramen
ovale is present in nearly 1 out of every 4 people, 16 and is present in 48% of people who suffer
from migraines with auras.1 The method of choice used for identifying a right-to-left shunt in the
presence of patent foramen ovale is saline contrast echocardiography.17 Diagnosing a right-to-left
shunt due to a patent foramen ovale in a person who suffers from migraine with auras is a very
good indicator that person should be closely monitored throughout their lifespan. In doing so, the
intent is to reduce the risk of migrainous infarctions. Physician assistants have a role in the
prevention and treatment of the morbidity and mortality of migrainous infarctions.
The identification of circulatory factors influencing migrainous infarctions in those with
migraine auras can enable the formation of preventative strategies. The Italian Project on Stoke
in Young Adults Study (IPSYS), sought to identify risk factors which could be used as predictive
markers and create a profile for those who are at risk of migrainous infarctions. The study
determined the presence of right-to-left shunts and migraine auras are common comorbidities in
young adults with ischemic strokes and reaffirmed the theory that CSD is triggered by
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microembolization brought on by cerebral hypoxic-ischemic episodes, which if prolonged could
cause cerebral ischemia and infarction.18
Prevention and Treatment
The prevalence of migraine auras and strokes in the United States has remained stable
over the past 15 years. However, this should not be viewed positively. According to the
American Migraine Prevalence and Prevention study nearly 25% of those with migraines are
ideal candidates for preventative therapy but a significant amount of these individuals do not
receive it. The study’s purpose was to determine the use of preventive treatment and assess the
epidemiology, burden, and patterns of treatment for migraines in the United States. 19
The responsibility for prevention and treatment of migraines is on the healthcare provider
and patient. Each plays an important role in the management of the condition. It is up to the
physician, the physician assistant, or the nurse practitioner to determine the best course of
treatment. Acute treatment of migraines includes protective measures to reduce the risk of
circulatory factors. This includes restricting the use of over-the-counter (OTC) medications and
prudently prescribing analgesics, muscle relaxers, triptans, antiemetics, or giving trigger point
injections (TPIs) and nerve blocks. Recognizing risk factors and comorbidities is therefore
important in the treatment of migraines.2,20
The Role of Physician Assistants
As important as the treatment of migraines is, the most important role of physicians,
physician assistants, and nurse practitioners is prevention. This is why it is important to examine
the patient’s risk profile thoroughly, not only for migraines but for strokes as well. The diagnosis
of migraines is an important factor in helping alleviate and treat the condition. Magnetic
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resonance imagining (MRI), computerized tomography scan (CT scan), magnet encephalogram
(MEG), and diffusion-weighted imaging (DWI), 21 are just a few of the tests that can be
performed to assess the patient’s risk and confirm the diagnosis. The neurologic assessment
portion of the physical exam is a valuable asset to the healthcare provider in differentiating
between differential diagnoses and migraines. The physical examination is important for patients
suffering from migraine auras such as the eye and fundoscopic exams in the presence of visual
scotomas. If the patient presents with a migraine aura it is important to note the onset of the
migraine as well as the severity. As previously discussed, an ongoing cortical spreading
depression (CSD) can result in hypoxia and infarction.
The prevention and treatment of migraine and migrainous infarctions begins with
awareness. Of the 25% of those who are candidates for treatment,19 some might not realize the
variety of treatment options available beyond OTC medications. Risk factor profiles, imaging
studies, progressive treatments, and CSD which is now being used as a biomarker, have great
significance in diagnosing, raising awareness, and even preventing migrainous infarctions.
As physician assistants, the majority of whom practice in primary care and general
medicine,22 it is important to understand the different causes, symptoms, and treatments of
migraines and strokes. This is especially the case since both conditions are prominent among the
United States’ population. Frequent cases of migraines with and without auras will present
throughout a physician assistant’s career. Some may very well be at an increased risk for
migrainous infarctions. Knowing the signs and diagnostic procedures available could help
significantly decrease the patient’s morbidity and mortality.
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Conclusion
The future of understanding migrainous infarctions in better detail is optimistic. As more
studies are employed the definitive pathophysiology behind the cause of migrainous infarctions
will be revealed. With this discovery, the care, management, and deterrence of migrainous
infarctions will greatly improve. The role of physician assistants in the treatment and prevention
of migraines will become even more imperative.
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References
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