Endovascular Neurosurgery

Cerebral angiography is a specialised neuroimaging technique employing an iodinated contrast agent to offer detailed, real-time visualisation of blood flow within the cerebral vasculature. It facilitates the precise identification of vascular abnormalities, including cerebral aneurysms, arteriovenous malformations (AVMs), haemangiomas, and the underlying causes of stroke.

Given its superior spatial resolution and dynamic imaging capability, cerebral angiography is central to early diagnosis and in informing the appropriate treatment strategy for each patient.

Spinal angiography is a procedure that provides highly detailed, real-time assessment of the blood vessels supplying and surrounding the spinal cord. It generates precise haemodynamic imaging that may reveal vascular abnormalities not detectable by standard imaging modalities. 

Spinal angiography is of particular importance in the diagnosis of spinal vascular conditions including spinal arteriovenous malformations (AVMs), dural arteriovenous fistulae (DAVFs), and selected rare causes of spinal cord infarction. By accurately characterising the vascular architecture and flow dynamics, this technique guides optimal treatment planning and improves the precision and safety of subsequent intervention.

A cerebral aneurysm is an abnormal focal dilatation of an arterial wall, arising at a site of structural weakness that places the patient at risk of haemorrhage if the aneurysm ruptures. Rupture causes subarachnoid haemorrhage and is a leading cause of haemorrhagic stroke.

The primary goal of treatment is to occlude the aneurysm and eliminate the risk of bleeding. This can be achieved through two principal approaches.

For wide-necked or broad-based aneurysms, more advanced endovascular techniques may be employed, including balloon-assisted coiling, stent-assisted coiling, or placement of a flow-diverting stent (a fine mesh device that redirects blood flow away from the aneurysmal sac and promotes its progressive thrombosis).

An arteriovenous malformation (AVM) is an abnormal tangle of blood vessels where arterial blood flows directly into the venous system, thereby bypassing the normal capillary bed. In a healthy individual, oxygenated arterial blood, travelling under high pressure, passes through the fine network of capillaries to deliver oxygen and nutrients to the brain tissue before draining at a lower pressure into the venous system and returning to the heart and lungs.

In an AVM, this normal circuit is absent: arterial blood shunts directly into the venous system at high pressure. Over time, these abnormal vessels dilate and their walls become thinner, rendering them fragile and prone to rupture and haemorrhage.

AVMs may present with symptoms such as headaches, weakness, paralysis, visual disturbances, or seizures. Many patients first present with symptoms at the time of a haemorrhage from one of the AVM’s component vessels.

AVMs may be treated through three main modalities:

At FV, endovascular embolisation is performed using purpose-designed embolic agents to occlude the abnormal arteriovenous shunting, with the aim of reducing or eliminating the AVM. In selected cases, this technique may be curative in its own right, or may serve as a preparatory step before microsurgery or radiosurgery to optimise the safety and efficacy of subsequent treatment.

Dural arteriovenous fistulae (DAVF) are blood vessels that represent abnormal connections between arteries and veins that are found in the covering of the brain. This covering is known as the dura, hence the name. There is a direct connection between the arteries and the vein without any vessels between.

These fistulae or abnormal connections usually develop over time and can occur after trauma, infection or thrombosis (clotting-off) of veins in the dura. The fistula may cause abnormal noises in the head due to the high flow of blood. They can also cause headaches or result in bleeding into the brain.

The treatment is similar to those available for AVMs and can include embolization, surgery, and in some cases radiosurgery. Embolization is often used as the primary therapy to treat this problem. Embolization is performed by placing a tiny catheter directly into the DAVF. Embolic material is then injected into the blood vessel to block them up. The embolic material leaves the catheter as liquid and solidifies within the DAVF blood vessel to block it up. Sometimes coils are also used to block up the DAVF.

Atherosclerosis is hardening of the arteries that can result in narrowing (stenosis) or blockage (occlusion) of an artery. This can occur in any artery in the body. Risk factors for the development of atherosclerosis include: high blood pressure, high cholesterol, diabetes, smoking, obesity, and genetic disposition.

When an endovascular neurosurgeon is involved in treating this problem it involves the larger arteries going to the brain (carotid or vertebral arteries) or the arteries inside the head (intracranial arteries).

Atherosclerosis of the carotid arteries often causes transient ischemic attacks (TIAs) because the blood flow may be lowered to the point that a portion of the brain is temporarily not functioning normally. Typical symptoms may include weakness or numbness on one side of the body, inability to speak or understand speech, and changes in vision. If the blood flow is only decreased for a short time a TIA occurs, but if the interruption is sufficiently long a stroke occurs.

Treatment with medicine may be recommended if the narrowing is not severe. If the narrowing is more severe, surgery or endovascular therapy may be recommended. Surgery involves opening the artery and removing the atherosclerotic plaque that is narrowing it.

Endovascular therapy involves using a balloon or stent to push open the wall of the artery from within. In the carotid artery, a stent is usually placed to open the narrowing. First, the doctor places an umbrella-like device beyond the narrowed segment to catch any debris that floats off when the stent is put in. Once the stent has been positioned the umbrella is closed and removed from the artery.

There are four main arteries that supply blood flow to the brain. Two carotid arteries and two vertebral arteries. The carotid arteries can be felt on each side of the lower neck, immediately below the angle of the jaw. The vertebral arteries are located in the back of the neck near the spine and cannot be felt on physical exam.

The artery walls are made up of three layers of different types of tissue, each with a specific function. Dissection occurs when a tear in the artery wall allows blood to leak between the layers and separate them.

Sometimes a stroke is the first sign of cervical artery dissection and emergency treatment is required. More commonly, symptoms develop over a period of hours or days, even in patients who have traumatic injuries. Symptoms are general rather than specific and include headache, neck and face pain (especially pain around the eyes), vision disturbances such as double vision or a droopy eyelid, a pulsatile “whooshing” sound in one of the ears, known as pulsatile tinnitus, or a sudden decrease in sense of taste and/or weakness on one side of the body.

Stroke can develop hours, days or even a week after these symptoms begin. This is the most serious risk of cervical artery dissection.

Angioplasty (repairing the dissected section of artery with inflation of a special balloon) or placement of a stent (a mesh-like device that holds the artery open) are two endovascular procedures that are used to treat cervical artery dissections. They frequently are used together to provide the longest-lasting treatment.

Carotid-cavernous fistulae are a specific kind of dural fistula that involves the carotid artery (or its branches) and a large vein (cavernous sinus) behind the eye. These fistulae can occur because of trauma, if there is an aneurysm in the carotid that breaks and causes the communication, or they can happen spontaneously without a definite reason.

Symptoms can include eye pain, swelling and redness of the eye, double vision or loss of vision if untreated. These fistulae are often treated by an endovascular approach, putting a catheter in the artery or vein, and using material to block up the connection between the artery and vein. This material can include balloons, coils, and liquid glue.