Article In Brief
Pregnancy may increase a woman’s risk of cervical artery dissection, providing a possible explanation for why pregnancy is a risk factor for stroke.
Pregnancy may elevate a woman’s risk of cervical artery dissection, especially during the postpartum period—a possible explanation for why pregnancy is a risk factor for stroke, researchers reported.
In a population-based study published online July 13 in Annals of Neurology, investigators examined claims data in two major states and found a two-fold increase in cervical artery dissection among pregnant women compared with a matched group of women hospitalized for renal colic.
Cervical artery dissection is a tear in the wall of any of the arteries in the neck that can cause blood clots. It can involve a carotid or vertebral artery, although multiple arteries can be involved, and it is one of the most common mechanism of stroke in younger persons.
The exact pathophysiology of cervical artery dissection is poorly understood, but possible mechanisms include underlying genetic predisposition and environmental triggers, said investigator Setareh Salehi Omran, MD, in the department of neurology at the University of Colorado Anschultz Medical Campus, in Aurora.
“Although we lacked adequate power and clinical information to identify all risk factors, we found that nearly half of the patients with cervical artery dissection were diagnosed with hypertensive disorders of pregnancy at the time of their dissection diagnosis,” she told Neurology Today.
The researchers analyzed data from emergency departments and acute care hospitals in New York and Florida between 2005-2015 and identified 826 women with cervical artery dissection and 826 matched controls, between the ages of 12 and 42 years, who had been hospitalized for renal colic.
The subjects were matched for age, race, insurance, income, and state of residence, with pregnancy defined as labor and delivery within 90 days before or six months after the index visit. The researchers then compared the risk of cervical artery dissection during pregnancy versus the same time period one year later.
Pregnancy was twice as common among 826 women with cervical artery dissection compared with the controls, with heightened risk limited to the postpartum period. Postpartum events occurred an average of 21 days after hospital discharge, and 45 percent of women with postpartum cervical artery dissection had hypertensive disorders of pregnancy at the time of their dissection diagnosis.
While a known mechanism of stroke in young adults, data are limited on whether cervical artery dissection is a common mechanism of stroke during pregnancy and the postpartum period. Coronary artery dissection is thought to be a major cause of pregnancy-associated myocardial infarction, and the same researchers previously reported an association between pregnancy and aortic dissection/rupture and heart attack.
Pregnancy-induced physiological changes and the effects of labor and delivery might be expected to increase the risk of such dissections. However, evidence of a potential link between pregnancy and cervical artery dissection is limited to case reports and case series, said Dr. Omran.
“If hypertensive disorders of pregnancy are found to be a risk factor for cervical artery dissection in pregnancy, early recognition and treatment of these conditions may potentially reduce the rate of dissection formation, as well as the overall risk of stroke during pregnancy,” she said.
“Knowing that cervical artery dissection may be a mechanism of pregnancy-related stroke may also increase awareness among health care providers and aid in early recognition of dissection symptoms. If a dissection is correctly identified, providers may decide to start an antithrombotic medication to reduce the risk of ischemic stroke.”
The study had a number of limitations, Dr. Omran said, noting that the use of administrative claims data may have led to misclassification of diagnoses, and under-ascertainment of cervical artery dissections, because many cases are asymptomatic, undiagnosed, or misdiagnosed as pain or headache.
Ascertainment bias also might have affected the results, especially in higher-risk subgroups such as those with hypertensive disorders of pregnancy, or misdiagnosis of other conditions, she said. Moreover, prior reports have found about six percent of cases of cervical artery dissection may be asymptomatic.
Ascertainment bias is when study data are collected for a given population but where some members of that group are less likely to be included in the analysis.
“Given the increased risk of cervical artery dissections during pregnancy, and especially the postpartum period, we believe that clinicians should be attuned to symptoms—the most common being headache and face/neck pain,” Dr. Omran said. “Early recognition of symptoms can lead to prompt diagnosis and appropriate treatment to prevent ischemic stroke.”
To better assess the risk, the next steps involve obtaining more clinical information on patients that have a dissection during pregnancy, including information related to their pregnancy.
“An interesting follow up question is whether women who have had a previous dissection during pregnancy can safely have a future pregnancy,” Dr. Omran added.
“We know that pregnancy raises the risk of stroke, especially in women with pregnancy-related hypertension, but we think of pregnancy risks like preeclampsia and clotting issues. We generally do not think of cervical artery dissection in pregnancy,” noted Louise McCullough, MD, PhD, professor and chief of neurology at Memorial Hermann Hospital, University of Texas Health Science Center, in Houston.
She agreed with the investigators that additional research is needed.
“These epidemiological studies based on claims data have a lot of potential for bias, as the researchers said. It is really difficult to get granular data about other risk factors that may have contributed to the results,” Dr. McCullough said. “Also, it is important to remember that this is claims data from just two states—Florida and New York—and the findings may be unique to their populations.”
And even if the findings are confirmed in larger, more comprehensive investigations, the actual incidence of events in the study was relatively low: 12 cases per million pregnancies, versus six per million women in the control arm, Dr. McCullough said.
“I think pregnancy is a risk for multiple disorders, including stroke, but the contribution of cervical artery dissection requires more study. With any study that uses claims data to assess risks is always an important caveat.”
Pooja Khatri, MD, FAAN, professor of neurology and director of the vascular neurology division at the University of Cincinnati, told Neurology Today she believes the results of this new study are persuasive, but even more so if they can be replicated in a prospective cohort study, ideally with more detailed clinical data to further characterize the association.
“The authors pretty convincingly show us that pregnancy is a risk factor for cervical artery dissection. We have wondered this based on one-off reports previously, but this study’s design makes us pretty confident and goes along with our already knowing that pregnancy is a risk factor for dissection in other arteries including the coronaries and the aorta,” she said.
What remains unknown, however, is what might be causing the reported susceptibility. It could be higher blood volume, hormonal changes to the arterial walls and their ability to stretch, or be related to patients with overall hypertension and the associated vasculopathy of pre-eclampsia, and any of these on top of genetic predispositions, Dr. Khatri explained.
“We really don’t know the way to reduce the risk of cervical dissection in general. Some suggest that extreme and abrupt neck movements should be avoided, and clearly hypertension should be treated.”
Even so, increase awareness of the risk of dissection is needed for women and their physicians, she continued.
“New types of headaches, including face or neck pain, should be taken seriously, especially in the weeks just after pregnancy. While migraines, especially if similar to prior migraines, are the most common causes of headaches, new headaches or new types of headaches require prompt medical attention to be considered treatable issues.”