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Cerebral Arteriovenous Malformation Aneurysm


It's a common misconception that strokes are inevitably related to age. However, this is incorrect. Anyone, including children, can have a stroke, as strokes are caused by cerebrovascular diseases, and everyone, regardless of age, can develop congenital or acquired cerebrovascular abnormalities. This overview provides basic information about cerebral arteriovenous malformation aneurysms, answering a series of common questions of concern to patients and their families.


Cerebral arteriovenous malformation (AVM) is a congenital cerebrovascular condition affecting a wide age range, from four-year-old children to octogenarians. If a congenital cerebral arteriovenous malformation ruptures, it can cause severe hemorrhagic stroke, greatly impacting the patient's brain and neurological function, and placing a heavy physical, emotional, and financial burden on their family.



(Cerebral Arteriovenous Malformation - AVM)

What is a Cerebral Arteriovenous Malformation Aneurysm?

A cerebral arteriovenous malformation is a congenital disease of unknown cause and is not hereditary. The problem of arteriovenous malformation forms during fetal brain development. It consists of abnormal blood vessels in the brain lacking a normal capillary system, allowing direct connections between arterial and venous vessels.

In normal human brain circulation, blood from the heart and major neck vessels passes through the brain's four main arteries and their branches to a network of very fine capillaries. Oxygen and nutrients in the blood permeate through capillary walls to nourish brain cells before being carried away by the venous system back to the neck veins and heart, completing the cycle.

In addition to supplying oxygen and nutrients to brain cells, capillaries also act as a buffer for the blood pressure in incoming arteries. However, in congenital arteriovenous malformations, this central area inherently lacks the normal capillary system, subjecting veins to immense pressure from arterial blood, leading to enlarged and weakened vein walls prone to rupture and hemorrhagic stroke.

Gender, Age Distribution, and Symptoms of Cerebral Arteriovenous Malformation Aneurysm Patients

  1. No Symptoms:
    Most patients show no symptoms from birth until the malformation ruptures.

  2. Symptoms of Unstable Blood Supply to the Brain:
    The malformed vessels can reduce oxygen supply to nearby brain cells, causing neurological symptoms such as occasional speech difficulties, limb weakness, unstable vision, and even epileptic seizures.

  3. Hemorrhagic Stroke:Female patients are more commonly affected by congenital cerebral arteriovenous malformations, with a broad age range from four-year-old children to elderly individuals over eighty. Although the annual risk of rupture is less than 1%, it is one of the leading causes of hemorrhagic stroke in children, young people, pregnant women, and healthy individuals, mostly occurring between the ages of 10 and 40. Patients with congenital cerebral arteriovenous malformations typically show no symptoms until the malformation ruptures, leading to severe headaches, dizziness, nausea, vomiting, neurological dysfunction, confusion, epileptic seizures, and even coma.

Annual Rupture Rate of Cerebral Arteriovenous Malformation Aneurysms

While the annual rupture risk is less than 1%, younger patients have a greater cumulative risk over their lifetime.

How is a Cerebral Arteriovenous Malformation Aneurysm Diagnosed?

Since people with congenital cerebral arteriovenous malformations usually show no symptoms until emergency symptoms appear at rupture, anyone without symptoms should undergo detailed physical examinations of the brain and its vascular structure in advance. Early diagnosis of congenital or acquired cerebrovascular abnormalities can allow for planned treatment options and preventive treatment, significantly reducing many tragedies and regrets.

Detailed Physical Structure Examination for Screening Cerebral Arteriovenous Malformation Aneurysms

  1. Magnetic Resonance Imaging (MRI) and Magnetic Resonance Angiography (MRA)
    MRI is a 'non-radiative, non-invasive, painless' scanning technique, unlike X-rays or Computerized Tomography (CT scans) that involve radiation. Advanced MRI machines not only eliminate the need for injected contrast agents but also provide 3D stereoscopic angiographic effects, accurately and clearly depicting the location of cerebral arteriovenous malformations and their relationship with normal brain tissue.

    Additionally, MRI can scan different parts of the body and provide detailed screening of internal structures for individuals without symptoms, detecting potential risks of stroke or cancer.

  2. Computerised Tomography Angiography (CTA)
    CTA involves radiation and the injection of a contrast agent. Although not the first choice for general health screening, it provides additional information for neurovascular surgeons to reference when choosing treatment options.

  3. Dynamic and 3D Digital Subtraction Cerebral Angiogram (DSA)While minimally invasive and involving radiation and contrast injection, DSA is essential for neurovascular surgeons before choosing treatment. It is the gold standard for a comprehensive understanding of cerebral vasculature, from arteries to capillaries to veins, including blood flow direction and speed. DSA also informs whether the malformed vessels are at imminent risk of rupture, aiding in determining the best medical plan and timeline for the patient.


Treatment Options for Cerebral Arteriovenous Malformation Aneurysms

Current Treatment Options:

  • Conservative Observation:
    If the patient is asymptomatic, elderly, in poor health, or when any treatment poses higher risks than non-treatment, doctors generally opt for conservative observation.

  • Minimally Invasive Microscopic Excision:
    Surgery is conducted under 3D stereoscopic computer navigation. If needed, neurovascular surgeons also use motor neuron cortical reflex and continuous brain function monitoring systems. Besides thoroughly excising the arteriovenous malformation and removing hematoma, surgeons strive to protect the patient's brain and neurological functions. The success rate depends on the size, location, complexity of the malformation, and the surgeon's experience.

  • Endovascular Embolisation:
    Depending on clinical conditions, embolization can be performed independently or prior to microscopic surgery or radiosurgery to reduce the size and scope of the malformation.

    Neurovascular surgeons insert an ultra-fine catheter through a needle hole in the patient's thigh artery, navigate it to the brain's vessels under X-ray guidance, and inject tiny titanium wires, plastic beads, or special glue into the malformed vessels to embolize the feeding arteries and the malformation's center. The risk of endovascular embolization lies in accidentally damaging normal and malformed vessels during surgery, causing occlusion or rupture and leading to ischemic or hemorrhagic stroke. Another risk is prematurely blocking the venous outflow, leading to increased pressure and rupture of the malformation.

  • Radiosurgery:
    Radiosurgery, not requiring anesthesia, delivers radiation from multiple angles, focusing high-energy rays on the malformation. Over two to three years, the abnormal vessels gradually close, redirecting blood back to normal vessels, significantly reducing the risk of hemorrhagic stroke after the malformation disappears.

    Radiosurgery is suitable for:
    - ​Malformations smaller than 3 cm
    - Deeply located or close to vital neurological functions in the brain
    - Cases assessed by neurovascular surgeons as too risky for embolisation or microscopic excision

    Risks of Radiosurgery:
    - Although it does not involve anesthesia or surgery, radiation passes through normal brain tissue to reach the malformation, potentially causing short-term or long-term effects on nearby brain cells and vessels.
    - If the radiation is not precisely targeted, it can prematurely block the venous part of the malformation, causing blood to enter through the arteries but not exit through the blocked veins, increasing pressure and leading to rupture and hemorrhagic stroke.

    Radiosurgery Systems:
    - X-Knife
    - Gamma Knife
    - Cyberknife


Factors Affecting Treatment Decisions

According to the American Stroke Association's guidelines (ASA Guideline), based on Professor Spetzler-Martin's research, we can classify AVM risk levels into five grades (see below) to differentiate treatment methods:

  • Low-Risk (Grades 1 and 2) AVMs:
    Neurovascular surgeons generally use Minimally Invasive Microscopic Excision for treatment. If the malformation involves vital brain neurological functions, radiosurgery may be considered.

  • Medium-Risk (Grade 3) AVMs:
    Treatment may involve embolisation after minimally invasive microscopic excision.​

  • High-Risk (Grades 4 and 5) AVMs:
    If any treatment is too dangerous, doctors generally opt for conservative observation.


Differences between the Three Radiosurgery Methods:


Complications of Cerebral Arteriovenous Malformation Aneurysms

  1. Hemorrhagic Stroke:
    Cerebral arteriovenous malformations account for about 2% of all hemorrhagic strokes and are a common cause of stroke in children and young adults. They are prone to rupturing and causing intracranial hemorrhage, with an increased risk for specific types of malformations or previous hemorrhages.

  2. Brain Hypoxia:
    Arteriovenous malformations can reduce oxygen entering the brain, leading to symptoms such as difficulty speaking, weakness, numbness in limbs, and unstable or lost vision.

  3. Brain Damage:
    Some arteriovenous malformations cause certain blood vessels to enlarge, compressing parts of the brain and potentially causing local damage. They can also lead to fluid accumulation in specific brain areas, causing hydrocephalus.

Related Cases

Case 1: Pregnant Woman's Aneurysm Suddenly Bursts

Two healthy teenage girls, aged 15 and 16, with no history of headaches, experienced sudden rupture and severe hemorrhagic stroke due to congenital cerebral arteriovenous malformations during early and mid-pregnancy. Emergency craniotomy was performed to clear the hematoma and reduce intracranial pressure. After waiting three months for brain swelling to subside, minimally invasive microscopic surgery was done to completely remove the malformations. Both girls and their babies fully recovered without any sequelae.

Another case involved a 39-year-old woman in late pregnancy. One night, just before the baby was due, her husband heroically saved both her and the baby from a critical situation. The baby is now healthy and adorable. Unfortunately, due to severe brain damage caused by the ruptured arteriovenous malformation, the woman became vegetative and passed away after five years in the hospital.


Case 2: Permanent Brain Damage in a Four-Year-Old

A four-year-old child, healthy since birth with no symptoms, suddenly experienced severe headaches and fell into a coma while shopping with his mother. He was diagnosed with a severe hemorrhagic stroke caused by a congenital cerebral arteriovenous malformation. Despite being saved from a critical state, he could not reverse the permanent brain damage caused by the stroke. He remains severely disabled, bedridden, and unable to communicate.

Case 3: Aneurysm Rupture Causing Limb Weakness

A 49-year-old woman felt weakness in her left leg two weeks after vaccination. Despite seeing a Chinese medicine practitioner and an orthopedist and undergoing spinal MRI, no cause was found. A neurovascular surgeon performed a 3D stereoscopic MRI angiogram, revealing a congenital cerebral arteriovenous malformation with minor bleeding in her brain, compressing the right brain area controlling her left leg. After thorough removal of the malformation and hematoma under 3D stereoscopic computer navigation, her brain function was fully restored. Post-surgery, her left leg strength returned to normal.


The surgery is conducted under the guidance of three-dimensional (3D) stereoscopic computer navigation.


The procedure involves the use of motor cortex mapping and continuous brain function monitoring systems.

Case 4: Aneurysm Bleed Leading to Severe Epileptic Seizures

A 37-year-old woman was found unconscious at home and admitted to a public hospital. Despite normal CT scans, EEGs, and blood tests, doctors couldn't determine the cause of her syncope. After discharge, she consulted a neurovascular surgeon who noticed high serum creatine kinase levels in her blood tests, indicating a severe tonic-clonic epileptic seizure. A 3D stereoscopic MRI angiogram revealed a 3 cm congenital arteriovenous malformation in her left frontal lobe, which had recently bled, causing her unconsciousness and epilepsy. A Dynamic 3D Digital Subtraction Cerebral Angiogram (DSA) determined the blood flow pattern in the malformation. During a four-hour microscopic surgery, the neurovascular surgeon found old hemosiderin next to the malformation, and both the malformation and hematoma were completely removed. The patient's brain function was fully preserved, and she was discharged two days later without any epileptic seizures for ten years.

Case 5: Radiation Therapy Causes Early Occlusion of Aneurysm Veins, Leading to Rupture

A 42-year-old housewife discovered a congenital cerebral arteriovenous malformation during a full-body checkup in Shenzhen. After returning to Hong Kong and consulting a public hospital, she was advised to observe and follow a conservative treatment plan. However, on her family's advice, she underwent radiosurgery in Guangzhou. Shortly after returning to Hong Kong, she had a seizure and was admitted to a public hospital. Emergency craniotomy was performed to remove the hematoma and reduce intracranial pressure. Further investigation suggested that imprecise radiosurgery might have prematurely occluded the veins of the malformation, causing it to rupture and leading to hemorrhagic stroke. Although her life was saved, she lost her ability to speak (aphasia) and lost mobility in her right hand.


Case 6: Removing the Ticking Bomb Before It Explodes

Two individuals, a 16-year-old boy and a 56-year-old man, underwent detailed brain and cerebral vascular structure checks without any symptoms. 3D stereoscopic MRI angiograms revealed congenital cerebral arteriovenous malformations in both. Following observation and conservative treatment, they underwent endovascular embolization and radiosurgery, effectively curing the malformations. This preemptive action removed the cerebral ticking bombs, eliminating their future risk of hemorrhagic stroke.


3D stereoscopic cerebral angiography shows a congenital cerebral arteriovenous malformation (AVM) in the left side of the brain.

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