Cerebrovascular Disease in Pregnant Patients
Although stroke is the fourth leading cause of death in the general population in the United States, it is uncommon among women of childbearing age. Nevertheless, cerebrovascular disease is ranked as the seventh most common cause of maternal mortality. Pregnancy has long been recognized as a factor that increases the risk for cerebrovascular disease in young women, although the magnitude of the increase in risk has been exaggerated by referral-based studies. Many of the same mechanisms that produce stroke in older age groups are responsible for strokes in pregnant women, but the distribution of mechanisms is different. Furthermore, some mechanisms are unique to pregnancy, particularly in the area of ischemic cerebrovascular disease. Evaluation and treatment of pregnant patients with cerebrovascular symptoms require an awareness of the differences in the underlying pathophysiology between pregnant and nonpregnant patients. The physician must understand the potential adverse effects of diagnostic procedures and medications on the fetus as well as on the patient.
HEMORRHAGIC DISORDERS
Hemorrhagic cerebrovascular disorders cause 5% to 10% of all maternal deaths that occur during pregnancy. Most common, nontraumatic intracranial hemorrhage in pregnancy occurs within the subarachnoid space (subarachnoid hemorrhage [SAH]), within the ventricular system (intraventricular hemorrhage), into the brain parenchyma (intracerebral hemorrhage [ICH]), or as a combination of these. Hemorrhage within each of these areas may be produced by various pathophysiologic mechanisms, most commonly (1) rupture of an intracranial aneurysm, which usually produces SAH, occasionally in association with ICH or intraventricular hemorrhage; (2) bleeding from an arteriovenous malformation (AVM), which frequently produces SAH, ICH, or both; and (3) rupture of an intraparenchymal vessel, which results in ICH, often with some extension of the bleeding into the subarachnoid space or ventricular system.
Intracranial Aneurysm
On the basis of data collected from various referral practices during the past 50 years, the incidence of aneurysmal rupture during pregnancy has been estimated at approximately 1 in 10,000 pregnancies, approximately 2 to 3 times that of nonpregnant women of the same age group. However, data from the Rochester, Minnesota, population from 1955 to 1979 revealed no instances of intracranial hemorrhage among 26,099 pregnancies, an observation suggesting that previous rates may have been overestimated. Approximately one half of the patients with ruptured aneurysms during pregnancy have had previous successful pregnancies
with no difficulty. As in the general population, there is some tendency toward increasing risk with increased maternal age. During pregnancy, the risk for rupture increases with each trimester, with about 80% occurring during the third trimester and 10% each in the first and second trimester. Although one might expect the Valsalva maneuver of childbirth to increase the risk for aneurysmal rupture, initial ruptures uncommonly occur during labor and delivery. However, rebleeding frequently occurs during labor and the first few weeks postpartum (Table 22-1).
with no difficulty. As in the general population, there is some tendency toward increasing risk with increased maternal age. During pregnancy, the risk for rupture increases with each trimester, with about 80% occurring during the third trimester and 10% each in the first and second trimester. Although one might expect the Valsalva maneuver of childbirth to increase the risk for aneurysmal rupture, initial ruptures uncommonly occur during labor and delivery. However, rebleeding frequently occurs during labor and the first few weeks postpartum (Table 22-1).
Early investigation and treatment of intracranial aneurysm are important in pregnant patients, particularly when the aneurysm has produced intracranial hemorrhage. Most patients with ruptured aneurysms will be treated, if possible. Radiographic and surgical procedures should not be delayed or avoided, although special shielding and strategies that use the lowest dose of radiation during radiography are required to protect the fetus. The clinical decisions that are involved in managing these patients vary with the type, size, and location of the aneurysm; the condition of the patient; and whether the aneurysm is symptomatic (see Chapters 14, 15, and 17). If the intracranial aneurysm is obliterated successfully (surgically clipped, trapped, or documented to be obliterated after coiling or other endovascular procedure) from the circulation before the 35th week of gestation, the rest of the pregnancy and delivery can proceed normally. In the uncommon situation that the ruptured aneurysm cannot be obliterated completely (incompletely clipped, arterial ligation, not obliterated after coiling or other endovascular procedure, wrapped, or packed) or if an operation is not performed, a cesarean section would typically be performed. If the SAH occurred during the third trimester, a combined neurosurgery/obstetrics procedure may be considered, with delivery by cesarean section immediately before or after the neurosurgery.
Intracranial AVM
AVMs cause approximately the same number of intracranial hemorrhages during pregnancy as do aneurysms. Although previous data revealed a high incidence of
intracranial hemorrhage among patients with AVM, recent data have been conflicting and have shown a minimally increased risk for pregnant patients. AVMs tend to occur in younger pregnant women (aged 15-25 years), and aneurysms in pregnant women aged 25 to 35 years. In contrast to aneurysms, AVMs tend to rupture during the second trimester (peak, 16-24 weeks of gestation), and they are more likely to hemorrhage again in the same pregnancy and in subsequent pregnancies. Rebleeding during delivery may be more common with AVMs than it is with aneurysms. However, the increased risk for AVM hemorrhage during specific trimesters and during delivery was not noted in one study (see Horton et al. [1990] in Suggested Reading for Section IV). Pregnant patients with AVMs tend to have a lower parity than those with aneurysms (Table 22-1). A patient with intracranial hemorrhage caused by a ruptured AVM is 6 times less likely to have had a previous normal pregnancy than a pregnant patient with aneurysmal SAH. Overall, the fetal prognosis is worse when there is known maternal intracranial AVM compared with the prognosis with intracranial aneurysm.
intracranial hemorrhage among patients with AVM, recent data have been conflicting and have shown a minimally increased risk for pregnant patients. AVMs tend to occur in younger pregnant women (aged 15-25 years), and aneurysms in pregnant women aged 25 to 35 years. In contrast to aneurysms, AVMs tend to rupture during the second trimester (peak, 16-24 weeks of gestation), and they are more likely to hemorrhage again in the same pregnancy and in subsequent pregnancies. Rebleeding during delivery may be more common with AVMs than it is with aneurysms. However, the increased risk for AVM hemorrhage during specific trimesters and during delivery was not noted in one study (see Horton et al. [1990] in Suggested Reading for Section IV). Pregnant patients with AVMs tend to have a lower parity than those with aneurysms (Table 22-1). A patient with intracranial hemorrhage caused by a ruptured AVM is 6 times less likely to have had a previous normal pregnancy than a pregnant patient with aneurysmal SAH. Overall, the fetal prognosis is worse when there is known maternal intracranial AVM compared with the prognosis with intracranial aneurysm.
TABLE 22-1 Features of intracranial aneurysm and AVM during pregnancy | ||||||||||||||||||||||||||||||||||||||||||
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The mechanism for the somewhat increased risk for rupture of AVMs during pregnancy is unknown. Many investigators have suggested that the periods of the greatest risk of rupture (16-20 weeks of gestation and at the time of labor and delivery) correlate with the greatest increases in cardiac output. Shunting through intracranial AVMs presumably increases during pregnancy. No direct measurements are available, but analogies have been made to visible cutaneous spider nevi and vascular tumors of the skin and gums. These tumors increase in size as pregnancy progresses (particularly during times of increased cardiac output) and decrease in size or disappear after delivery. Increased shunting is thought by some physicians to predispose to rupture and to focal ischemic events from the AVM. The latter condition has been noted only rarely during pregnancy.
Some pregnant patients with AVMs also present with periodic throbbing headache that appears in the same location with each episode and is indistinguishable from classic migraine. Others present with progressive neurologic deficits or seizures without evidence of associated cerebral hemorrhage or infarction. However, during pregnancy, initial presentation with SAH is approximately 5 to 10 times more likely than is any other type of presentation.
As noted with intracranial aneurysms, early investigation and treatment of intracranial AVMs are important in pregnant patients, particularly in the setting of intracranial hemorrhage. Again, radiographic and surgical procedures should not be delayed or avoided, although special shielding and strategies that use the lowest dose or radiation during radiography are required to protect the fetus. The clinical decisions that are involved in managing these patients vary with the type of vascular malformation and whether it is symptomatic (see Chapters 14, 15, and 17).
If the AVM can be totally excised before the 35th week of gestation, the rest of the pregnancy and delivery can proceed normally. If the lesion is not operable or only partially resectable and has bled during the pregnancy, elective cesarean section is usually recommended.
Cavernous Malformations (CMs)
A CM may present with hemorrhage-related symptoms during pregnancy, including neurologic deficit, headache, and seizures. Although there are reports of cavernoma growth and rupture occurring during pregnancy, it is not clear that pregnancy impacts the likelihood of CM rupture, in general. Most recent data suggest that the rupture risk during pregnancy may not be elevated. This leads to the current recommendation that women with a CM need not avoid pregnancy.
For women who present with CM hemorrhage-related symptoms during pregnancy, the CM is typically treated following pregnancy. It is uncommon for CM treatment to be needed during pregnancy, but this is sometimes necessary for patients with severe neurologic symptoms or recurrent hemorrhage. There are conflicting data regarding the risk of CM hemorrhage with vaginal delivery but current data suggest that the overall risk is likely very low. For patients with CM-related symptoms during pregnancy, a cesarean section is often recommended.
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