Introduction 

Moyamoya disease is a rare but serious condition that affects the blood vessels in the brain.¹ This disease causes blood vessels in the brain to become narrow or blocked, which leads to the formation of small and fragile blood vessels, to try and bypass such blockages.¹ These blood vessels often look like a "puff of smoke" on imaging scans, which is what "Moyamoya" means in Japanese. This disease increases the risk of strokes, which are sudden interruptions in the blood supply to the brain.² While the disease can affect individuals of any age, it is most commonly diagnosed in children and young adults.

For women with Moyamoya disease, pregnancy can be particularly challenging. Pregnancy brings many changes to a woman’s body, including increased blood volume and pressure, which can stress the delicate blood vessels in the brain. This article will look at Moyamoya disease in more detail, its implications for pregnancy, and how it can be managed to ensure the safety of both mother and baby. 

Understanding moyamoya disease 

Moyamoya disease leads to a progressive narrowing and blockage of blood vessels, specifically the internal carotid arteries.³ These internal arteries are important blood channels that supply the brain. A blockage in these arteries leads the brain to create a network of smaller blood channels, to make up for the narrowing of these arteries and keep blood flowing.³ These new blood arteries tend to be very weak and prone to bleeding.

Symptoms of Moyamoya disease and pregnancy

Pregnancy induces significant cardiovascular changes that can impact women with Moyamoya disease. These changes include increases in blood volume, cardiac output, and blood pressure, which can heighten the risk of cerebrovascular events (i.e., emergencies in which the blood supply to the brain is cut off). Additionally, the hypercoagulable state of pregnancy, characterized by a tendency to form blood clots, can further complicate the condition.

The symptoms of Moyamoya disease can vary widely, but often include:

• Transient Ischemic Attacks (TIAs): also known as mini-strokes, are temporary episodes of reduced blood flow to the brain. These cause symptoms like weakness, numbness, or a difficulty speaking, which usually resolve within minutes or a few hours.⁴
• Ischemic strokes: these are more severe than TIAs and result in permanent damage. The narrowing of the cerebral arteries means there is a decreased blood flow to the brain. Symptoms include sudden weakness, numbness, confusion, trouble speaking, vision problems, and severe headaches. During pregnancy, this can be exacerbated and increase the chances of certain risks.⁵  
• Seizures: uncontrolled electrical activity in the brain due to fluctuating cerebral blood flow, leading to convulsions or unusual behavior.
• Cognitive Decline: difficulty with memory, thinking, or understanding.

Diagnosis and monitoring of moyamoya during pregnancy 

Diagnosing Moyamoya disease in pregnant women follows the same principles as in non-pregnant individuals, with careful consideration of the safety of imaging modalities for the fetus. The following diagnostic tools are commonly used:

• Magnetic Resonance Angiography (MRA): a non-invasive scan that uses magnetic fields to create detailed images of blood vessels⁶
• Computed Tomography Angiography (CTA): uses X-rays and a special dye to show blood flow in the arteries to provide detailed images of the blood vessels. While this is effective it is limited in pregnancy because of the radiation exposure and potential risks⁷
• Cerebral Angiography: an invasive test where a catheter is inserted into a blood vessel and a dye is injected to highlight the arteries on X-rays. This is the most definitive test for diagnosing Moyamoya disease, but is less commonly used during pregnancy due to its invasiveness and radiation exposure⁸

Challenges and risk for pregnant women with Moyamoya 

Pregnancy involves significant changes to a woman’s body that can affect Moyamoya disease. These include:

• Increased Blood Volume and Pressure: the heart pumps more blood during pregnancy, which can put extra pressure on the fragile blood vessels in the brain seen in Moyamoya disease.
• Hypercoagulable State: pregnancy increases the tendency of blood to clot, which can further complicate Moyamoya disease by increasing the risk of ischemic strokes⁸

Women with Moyamoya disease face several risks during pregnancy:

• Increased Risk of Stroke: both ischemic (due to reduced blood flow) and hemorrhagic (due to bleeding from fragile vessels) strokes are more likely to occur.
• Seizures: changes in blood flow and pressure can increase the likelihood of seizures.
• Hypertension (High Blood Pressure): pregnancy-induced hypertension can be particularly dangerous, further stressing the delicate blood vessels in the brain.
• Pre-eclampsia: a condition characterized by high blood pressure and damage to other organs, most often the liver and kidneys, which can be life-threatening.

Management strategies for pregnant woman with moyamoya disease 

Effective management of Moyamoya disease during pregnancy requires a team of specialists, including obstetricians, neurologists, and anesthesiologists. Some strategies used to manage the condition include:

Preconception Counseling

Women with Moyamoya disease should seek counseling before becoming pregnant.This helps in understanding the risks and planning for a safe pregnancy. Evaluations may include assessing the severity of arterial narrowing and previous stroke history.

Antenatal Care

Regular check-ups are essential to monitor the health of both mother and baby. These visits should include:

• Neurological Assessments: Regular checks for any new or worsening neurological symptoms including headaches, visual disturbances, weakness or seizures.⁹
• Blood Pressure Monitoring: Keeping blood pressure under control is crucial to reduce stroke risk. Safe medications like labetalol or methyldopa may be prescribed.⁹
• Fetal Monitoring: Regular ultrasounds to check on the baby’s growth and development.⁹

Medication Management

Some medications can help manage Moyamoya disease during pregnancy:

• Antiplatelet Therapy: low-dose aspirin may be recommended to reduce the risk of blood clots, which is generally safe during pregnancy.¹⁰ 
• Anticonvulsants: if the mother has a history of seizures, anticonvulsant medications may be required. Doctors will choose drugs that are effective and have minimal risk to the developing baby.

Labor and Delivery Planning

The delivery plan should minimize stress and the risk of stroke:

• Mode of Delivery: vaginal delivery is usually preferred because it carries fewer risks than a cesarean section. However, if the mother’s condition is severe, a cesarean section may be a safer option.¹¹
• Anesthesia Management: epidural anesthesia is often preferred to maintain stable blood pressure and reduce stress. General anesthesia is used less frequently due to its potential to cause blood pressure fluctuations.¹¹

Postpartum Care

The period after delivery is critical for the monitoring and managing of postpartum complications:

• Continued Monitoring: close observation for any signs of stroke or other neurological issues.
• Blood Pressure Control: ongoing management of blood pressure to prevent postpartum complications.
• Breastfeeding Considerations: guidance on the safety of medications during breastfeeding and ensuring they do not interfere with lactation.

Understanding the Interaction Between Pregnancy and Moyamoya Disease

The interaction between pregnancy and Moyamoya disease is complex and multifaceted. The physiological changes that occur during pregnancy can significantly affect the course of Moyamoya disease, and vice versa. Understanding these interactions is crucial for effective management of the condition.

• Physiological Changes in Pregnancy: pregnancy induces several physiological changes, including increased blood volume, cardiac output, and a hypercoagulable state. These changes are necessary to support the growing fetus, but can place additional stress on the cardiovascular system, in turn exacerbating conditions like Moyamoya disease.
• Cerebrovascular Hemodynamics: in Moyamoya disease, the narrowing of cerebral arteries impairs blood flow to the brain. The increased cardiac output during pregnancy can temporarily improve cerebral perfusion, but it also increases the risk of hemorrhagic events due to the fragile nature of the collateral vessels.
• Hormonal Influences: hormonal changes during pregnancy, particularly increased levels of estrogen and progesterone, can affect vascular tone and reactivity. These hormonal fluctuations may influence the course of Moyamoya disease, although the exact mechanisms are not fully understood.
• Impact on Fetal Development: Moyamoya disease can indirectly affect fetal development through its impact on maternal health. Complications such as stroke or seizures pose risks to both mother and fetus, highlighting the importance of meticulous prenatal care.

Summary 

Moyamoya disease poses significant challenges for pregnant women due to the increased risk of strokes and other complications. However, with careful planning, regular monitoring, and a multidisciplinary approach, many women with Moyamoya disease can have safe pregnancies and healthy babies. Understanding the complexities of Moyamoya disease and the physiological changes during pregnancy is crucial for healthcare providers to offer the best care possible. Ongoing research and advancements in medical science will continue to improve the management and outcomes for women with Moyamoya disease during pregnancy.