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Treatment of Cerebral Arteriovenous Malformation Aneurysms


Cerebral Arteriovenous Malformation (AVM) is a congenital brain vascular anomaly affecting a wide age range, from 4-year-old children to people over 80 years old. Once ruptured, a congenital cerebral AVM can cause severe hemorrhagic stroke, significantly impacting the patient's brain and mental health, and placing a heavy burden on the patient's family.


Cerebral Arteriovenous Malformation - AVM

Causes of Cerebral AVM

Cerebral AVM is a congenital disease with unclear causes and no genetic origins. The problem of arteriovenous malformation forms during fetal brain development within the mother's womb, leading to abnormal vascular tissue in the brain lacking a normal microvascular system, directly connecting arterial and venous blood vessels.

In normal human brains, blood supply comes from major vessels in the heart and neck, passing through four main arteries in the brain, then through smaller branches to numerous tiny microvessels. Oxygen and nutrients in the blood permeate through microvessel walls to nourish brain cells. Blood then flows back through the venous system to the neck veins and heart, completing the cycle.

Besides supplying oxygen and nutrients, another function of microvessels is to buffer the pressure from blood entering the arteries. However, the center of congenital arteriovenous malformations inherently lacks this microvascular system. This absence subjects veins to enormous arterial blood pressure without buffering, causing vein enlargement and fragility, and increasing the risk of rupture and hemorrhagic stroke.

  1. Patient Demographics and Symptoms: Most patients, from birth until AVM rupture, exhibit no symptoms.

  2. Symptoms of unstable brain blood supply include occasional speech difficulties, limb paralysis, unstable vision, and even epileptic seizures.

  3. Hemorrhagic Stroke: Female patients are more common, covering a wide age range. Despite a less than 1% annual risk of AVM rupture, it's a leading cause of hemorrhagic stroke among children, young people, pregnant women, and healthy individuals. Most patients are between 10 and 40 years old. Individuals with congenital cerebral AVM typically show no symptoms until a rupture occurs, leading to severe headaches, dizziness, nausea, vomiting, neurological dysfunction, confusion, seizures, or even coma.

Diagnosis of Cerebral AVM

Since patients generally show no symptoms until an emergency occurs due to AVM rupture, it's advisable for anyone to undergo detailed brain and vascular structure checks, even without symptoms, to diagnose congenital or acquired cerebral vascular anomalies. Preventative treatment can significantly reduce tragedies and regrets before a hidden cerebral time bomb explodes.

Detailed Structural Examination Options:

  • Computerised Tomography Angiography (CTA): Involves radiation and intravenous contrast injection. While not the first choice for general health screening, CTA provides additional information for neurovascular surgeons to reference in choosing treatment plans.

  • Dynamic and 3D Digital Subtraction Angiography (DSA): Although minimally invasive with radiation and contrast injection, DSA is a gold standard final check required by neurovascular surgeons before deciding on a treatment plan. It provides comprehensive information on brain vessels, from arteries to microvessels and veins. DSA also helps determine if an AVM is at risk of imminent rupture, aiding in the decision of the best medical approach and timing.

  • Magnetic Resonance Imaging (MRI) and Magnetic Resonance Angiography (MRA): MRI is a "non-radiative, non-invasive, painless" scanning technique, differing significantly from radiative X-rays or CT scans. Advanced MRI machines not only avoid the need for contrast injection but also achieve 3D stereoscopic cerebral angiography effects, clearly depicting the position of cerebral AVMs and their relationship with normal brain tissue. MRI can also scan different parts of the body, providing a detailed screening for stroke or cancer risks in asymptomatic individuals.

Common Clinical Treatment Options

The current treatment options include:

  • Conservative Observation: For patients with no symptoms or those with symptoms but advanced age, poor health, or when the risk of any treatment exceeds that of non-treatment, a conservative approach is generally taken.

  • Minimally Invasive Microscopic Excision: The surgery is guided by 3D stereoscopic computer navigation, utilizing motor cortex mapping and continuous brain function monitoring systems. The goal is to completely remove the AVM and hematoma while protecting the patient's brain function. The success rate depends on the AVM's size, location, complexity, and the surgeon's experience.

  • Endovascular Embolisation: Depending on clinical conditions, this method can be performed alone or before microscopic surgery or radiosurgery to reduce the size and scope of the AVM. The neurovascular surgeon inserts an ultra-fine catheter through the artery in the patient's groin, navigating to the brain's vessels under X-ray guidance. Materials like tiny titanium wires, plastic beads, or special glue are injected into the AVM's vessels to block the arteries feeding the malformation and its center. Risks include accidental damage to normal and malformed vessels, causing ischemic or hemorrhagic stroke. Another risk is premature closure of veins draining the AVM, leading to a sudden increase in blood pressure and rupture.

  • Radiosurgery: This treatment does not require anesthesia. Radiation from multiple angles focuses on the malformed vessels, gradually closing them over two to three years, redirecting blood flow back to normal vessels. Once the AVM disappears, the risk of hemorrhagic stroke significantly reduces. Radiosurgery is suitable for AVMs smaller than three centimeters, located deep in the brain or near critical neural functions. If the neurovascular surgeon assesses the risks of embolization or excision as too high, radiosurgery is chosen.

  • Radiosurgery Risks: Though non-invasive and radiation-based, the treatment can affect nearby brain cells and vessels. If the treatment is imprecise, it might cause premature closure of venous parts of the AVM, leading to a rise in blood pressure and rupture.

  • Radiosurgery Systems: Options include the X-Knife, Gamma Knife, and Cyberknife.

Factors Influencing Neurovascular Surgeons' Decisions:

Based on the American Stroke Association (ASA) guidelines and Professor Spetzler-Martin's research, AVMs are categorized into five risk levels to determine the treatment method:

  • Low-Risk (Levels 1 and 2) AVMs: Treated with Minimally Invasive Microscopic Excision, with radiosurgery considered if the AVM is near critical brain functions.

  • Moderate-Risk (Level 3) AVMs: Treated with endovascular embolization following microscopic excision.

  • High-Risk (Levels 4 and 5) AVMs: If all treatment options are too risky, a conservative approach with ongoing observation is generally adopted.

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