What are the causes of hemiparesis in pregnancy?

Causes of Hemiparesis in Pregnancy

Cerebrovascular accidents—both ischemic stroke and intracranial hemorrhage—are the primary causes of hemiparesis in pregnancy, with pre-eclampsia/eclampsia being the leading underlying etiology, followed by cerebral venous sinus thrombosis, particularly in the postpartum period. 1

Primary Cerebrovascular Causes

Ischemic Stroke

• Arterial infarction occurs at a rate of 11/100,000 deliveries, with the highest risk in the postpartum period (RR 8.7) 1
• Cerebral venous sinus thrombosis (CVST) is particularly common postpartum and represents approximately 2% of pregnancy-associated strokes 1
• Pregnancy induces hypercoagulability through increased platelet adhesion, elevated fibrinogen, increased factors VII, VIII, IX, X, and XII, decreased protein S and C levels, and reduced fibrinolysis 1
• The postpartum period poses even greater thrombotic risk than pregnancy itself due to venous stasis and continued hypercoagulability 1

Intracranial Hemorrhage

• Intracerebral hemorrhage occurs at 9/100,000 deliveries, with the postpartum period carrying the highest risk (RR 28) 1
• Ruptured berry aneurysms and arteriovenous malformations increase during pregnancy due to hemodynamic changes, increased blood volume, and hormonal effects on vessel walls 2
• Severe hypertension is notably not a reliable predictor of intracranial hemorrhage in pregnancy—only 1 of 6 women with intracranial hemorrhage had diastolic BP ≥110 mmHg in one series 3

Pre-eclampsia/Eclampsia as Leading Cause

Clinical Presentation

• Eclampsia remains the leading cause of both ischemic and hemorrhagic stroke in pregnancy 1
• Pre-eclampsia complicates 5-7% of pregnancies overall, but increases to 25% in women with pre-existing hypertension 1
• Severe pre-eclampsia manifests with cerebral edema causing headache, visual disturbances, occipital lobe blindness, hyperreflexia with clonus, and convulsions 1
• Women with hypertensive disorders face higher risk for cerebrovascular accident, accounting for 25% of pregnancy-associated strokes 1

Pathophysiology

• Pre-eclampsia involves systemic endothelial dysfunction with cerebral autoregulation disturbances 1
• Angiogenic factors (VEGF and sFlt-1) mediate the endotheliopathy that predisposes to both ischemic and hemorrhagic stroke 1

Antiphospholipid Syndrome

• Primary antiphospholipid syndrome presents with both arterial infarction and CVST during pregnancy 4, 5
• Hemiparesis can appear within hours after delivery, particularly following aspirin withdrawal 4
• CVST from antiphospholipid syndrome can occur as early as the first trimester, presenting with sudden headaches and hemiparesis 5
• The close temporal relationship between aspirin discontinuation and stroke suggests causal link, requiring continuation of anticoagulation even if antibodies were previously asymptomatic 4

Additional Risk Factors

Prothrombotic States

• Homocystinuria causes both arterial and venous occlusion, though uncommon 1
• Essential thrombocythemia and polycythemia vera lead to microvascular occlusion and major vessel thrombosis 1
• Inherited thrombophilias increase stroke risk when combined with pregnancy-related hypercoagulability 1

Cardiac Sources

• Peripartum cardiomyopathy represents the most common cause of severe cardiovascular complications in pregnancy 1
• Rheumatic heart disease with mitral stenosis increases embolic stroke risk due to atrial fibrillation and left atrial thrombus formation 6

Critical Diagnostic Pitfalls

Misdiagnosis as Eclampsia

• Presumption of eclampsia delayed correct diagnosis in 41.7% of cerebrovascular cases in one series 3
• Blood pressure does not reliably predict diagnosis—only 4 of 14 women with infarction had diastolic BP ≥110 mmHg 3
• Suspected eclampsia unresponsive to magnesium sulfate therapy warrants immediate neuroimaging 3

Timing Considerations

• Patient delay in seeking medical attention complicated 41.7% of cases 3
• Postpartum period (first 6 weeks) carries highest risk for both ischemic and hemorrhagic stroke 1
• Cerebral venous sinus thrombosis is more common postpartum than during pregnancy 1

High-Risk Clinical Scenarios

• Age >35 years, black ethnicity, multiple gestation, and greater parity increase stroke risk 1
• Pre-existing conditions: hypertension, heart disease, diabetes, lupus, sickle cell disease, migraine 1
• Cesarean delivery, fluid/electrolyte disorders, thrombophilia, postpartum infection 1
• HELLP syndrome (hemolysis, elevated liver enzymes, low platelets) indicates severe pre-eclampsia with cerebrovascular risk 1

Management Implications

• Immediate neuroimaging (CT or MRI) is essential when hemiparesis develops, regardless of blood pressure 3
• Anticoagulation decisions must balance maternal stroke prevention against bleeding risk and fetal safety 1
• Heparin (not warfarin) is the anticoagulant of choice during pregnancy, particularly in first trimester 1
• Postpartum monitoring must continue for at least 6 weeks given the elevated stroke risk during this period 1, 7

1, 7, 6, 3, 4, 5, 2