Specialised treatment for abnormal blood-vessel connections .Arteriovenous malformations and fistulas create abnormal direct connections between arteries and veins. These connections can alter normal blood flow, raise pressure in veins and, depending on their location and drainage pattern, cause bleeding, seizures, neurological symptoms, eye problems or spinal cord dysfunction. Catheter angiography provides a detailed map of feeding arteries, the abnormal connection or nidus, and the veins carrying blood away. Embolization can then be used to close selected abnormal channels, reduce blood flow through the lesion or prepare it for surgery or radiosurgery.

Arteriovenous malformations of the brain and spine

An arteriovenous malformation (AVM) is a tangle of abnormal vessels in which blood passes directly from arteries to veins without the usual intervening capillary network. Brain AVMs may present with haemorrhage, seizure, headache or a neurological deficit, although some are found incidentally. Spinal AVMs may cause back pain, weakness, altered sensation, difficulty walking, bladder or bowel symptoms, or sudden spinal bleeding.

How AVMs are evaluated

MRI, CT angiography or MR angiography may suggest an AVM, but catheter angiography is often needed to define the precise vascular anatomy and plan treatment. The team assesses lesion size and location, arterial feeders, associated aneurysms, venous drainage and previous bleeding, along with the risks of intervention and observation.

Treatment options

Management may include observation, microsurgery, stereotactic radiosurgery, embolization or a staged combination. Embolization is not automatically curative. Its role depends on the anatomy and treatment goal and may be definitive for selected fistulous connections, targeted to a high-risk part of an AVM, or used before surgery or radiosurgery.

Dural arteriovenous fistula (dAVF)

A dural arteriovenous fistula is an abnormal connection between arteries supplying the dura and a dural venous sinus or cortical vein. Symptoms can include pulse-synchronous noise in the ear, headache, eye symptoms, cranial nerve problems, seizure, neurological deficits or intracranial bleeding. The risk is strongly influenced by how the fistula drains into the veins.

Catheter angiography is usually required to classify the fistula and determine the safest route for treatment. Embolization may be performed through an artery or vein using liquid embolic material, coils or a combination. The goal is to close the abnormal connection while preserving normal venous drainage and nearby arteries.

Carotid-cavernous fistula (CCF)

A carotid-cavernous fistula is an abnormal connection between the carotid arterial system and the cavernous sinus, a venous space behind the eye. It may follow trauma, arise from aneurysm rupture into the cavernous sinus or develop indirectly through small dural arteries.

Possible symptoms

• Red or swollen eye, prominent eye or eyelid swelling.
• A pulsating sound in the head or eye.
• Double vision, reduced vision or eye-movement weakness.
• Eye pain, headache or raised pressure within the eye.
• Symptoms beginning after head or facial trauma.

Treatment depends on the fistula type, flow rate, symptoms and venous drainage. Endovascular embolization aims to close the abnormal connection while preserving normal carotid blood flow whenever possible. Coils, liquid embolic agents, balloons, stents or other devices may be selected according to the anatomy.

Embolization for AVM and AVF

During embolization, a microcatheter is navigated close to the abnormal vessel connection. The specialist delivers an embolic material that reduces or stops abnormal blood flow. Treatment may be completed in one session or staged over more than one session to reduce physiological stress and manage complex anatomy safely.

Potential goals of embolization

• Complete closure of a selected fistula.
• Reduction of high-risk blood flow or treatment of an associated aneurysm.
• Reduction in AVM size or blood supply before microsurgery.
• Targeted treatment before or alongside stereotactic radiosurgery.
• Relief of venous hypertension affecting the brain, eye or spinal cord.

Risks and follow-up

Neurovascular embolization is technically complex. Risks may include bleeding, stroke, vessel injury, unintended blockage of a normal artery or vein, cranial nerve injury, contrast reaction, access-site complications or incomplete closure. The specific risk depends on the lesion, route and embolic material. Follow-up imaging is important because some lesions require staged treatment or can recur or recruit new vessels.