Bleeding into the brain parenchyma most often is caused by spontaneous rupture of small vessels previously damaged by chronic hypertension (see Fig. 60-2). Thus, pregnancy-associated hemorrhagic strokes such as the one shown in Figure 60-3 are
FIGURE 60-3 A 37-year-old gravida with intrapartum eclampsia at term. A noncontrast computed tomography axial head image demonstrates a large intraparenchymal hemorrhage.
oten associated with chronic hypertension and superimposed preeclampsia (Cunningham, 2005; Martin, 2005). Because of its location, this type of hemorrhage has much higher morbidity and mortality rates than does subarachnoid hemorrhage (Smith, 2015). Pressure-induced rupture causes bleeding into the putamen, thalamus, adjacent white matter, pons, and cerebellum. In the 28 women described by Martin and associates (2005), half died and most survivors had permanent disabilities. his cautions for the importance of proper management for gestational hypertension-especially systolic hypertension-to prevent cerebrovascular pathology (Chap. 40, p. 738).
In a study of 639 cases of pregnancy-related subarachnoid hemorrhage from the Nationwide Inpatient Sample, the incidence was 5.8 per 100,000 pregnancies, with half occurring postpartum (Bateman, 2012). A remarkably similar incidence was reported in Japanese women (Yoshida, 2017). hese bleeds are more likely caused by an underlying cerebrovascular malformation in an otherwise norml patient (see Fig. 60-2). Ruptured saccular or "berry" aneurysms cause 80 percent of all subarachnoid hemorrhages. The remaining cases are caused by a ruptured arteriovenous malformation, coagulopathy, angiopathy, venous thrombosis, infection, drug abuse, tumors, or trauma. Such cases are uncommon, and a ruptured aneurysm or angioma or bleeding from a vascular mlformation has an incidence of 1 in 75,000 pregnancies. Although this frequency is not diferent from that in the general population, the mortality rate during pregnancy is reported to be as high as 35 percent (Yoshida, 2017).
Intracranial Aneurysm. Approximately 1 to 2 percent of adults have this lesion (Lawton, 2017). Fortunately, only a small percentage rupture. he rate approximates 0.1 percent for aneurysms <10 mm and 1 percent for those >10 mm (Smith, 2015). Most aneurysms identified during pregnancy arise from the circle of Willis, and in 20 percent of case, there are multiple lesions. Pregnancy does not raise the risk for aneurysmal rupture. However, because of their high prevalence, they are more likely to cause subarachnoid bleeding than other etiologies (Hirsch, 2009; Tiel Groenestege, 2009). A systematic review of 44 women with 50 aneurysms in pregnancy reported that 72 percent ruptured during pregnancy, and 78 percent of these did so during the third trimester (Barbarite, 2016). his proclivity for rupture late in pregnancy was also reported by Yoshida and colleagues (2017).