Brain blood vessels & stroke

A brain (cerebral) aneurysm is a weak, bulging area in the wall of an artery in the brain. Many aneurysms are small, cause no symptoms and are found by chance on a scan. If an aneurysm bursts, it bleeds into the space around the brain, called a subarachnoid haemorrhage. This is a medical emergency, usually causing a sudden, severe headache, often with vomiting, neck stiffness, drowsiness or collapse.

Unruptured aneurysms are assessed with CT angiography, MR angiography or catheter angiography. The decision on whether to treat depends on the aneurysm's size, shape and location, your age and health, your family history and other risk factors, and is made together with you after discussing the risks and benefits.

Depending on the condition, management may involve observation with repeat imaging and control of risk factors such as blood pressure and smoking, microsurgical clipping, or endovascular treatment such as coiling or flow diversion, which is arranged with partner specialists. A ruptured aneurysm is treated urgently in hospital.

Vascular malformations are abnormal tangles or connections of blood vessels. An arteriovenous malformation (AVM) is a tangle of vessels where arteries connect directly to veins. A cavernoma (cavernous malformation) is a cluster of small, thin-walled vessels. A dural arteriovenous fistula is an abnormal connection between arteries and veins in the covering of the brain.

Some cause no symptoms and are found by chance. Others may cause bleeding in the brain, seizures, headaches, a whooshing sound in the ear, or weakness, numbness or other neurological symptoms. Assessment includes MRI, CT angiography or MR angiography and, often, catheter angiography to map the blood vessels.

The appropriate treatment depends on the lesion's type, size, location, vascular anatomy and how it has presented, and is usually considered by a multidisciplinary team. Depending on the condition, options may include observation, medicines to control seizures, microsurgical removal, or endovascular embolisation or stereotactic radiosurgery arranged with partner specialists and centres.

Moyamoya disease is a rare condition in which the large arteries at the base of the brain gradually narrow, reducing blood flow. The brain grows small fragile vessels to compensate. It can affect both children and adults, and may cause mini-strokes (transient ischaemic attacks), strokes, seizures, headaches or, in adults, bleeding in the brain. Other conditions, such as blocked neck or brain arteries, can also reduce blood flow to the brain.

Assessment includes MRI, CT or MR angiography, catheter angiography and cerebral perfusion studies, which measure how well blood reaches different parts of the brain.

Extracranial-to-intracranial (EC-IC) cerebral bypass is an operation that connects an artery from outside the skull, usually in the scalp, to an artery on the surface of the brain, to improve blood flow. It may be considered in selected patients with impaired cerebral blood flow or complex cerebrovascular disease where revascularisation is clinically appropriate. Depending on the condition, management may also involve medicines and control of stroke risk factors.

A stroke happens when blood flow to part of the brain is blocked (ischaemic stroke) or when a blood vessel bleeds into the brain (haemorrhagic stroke). Bleeding may be caused by high blood pressure, an aneurysm or vascular malformation, blood-thinning medicines or other conditions. A large stroke can also cause dangerous brain swelling.

Most strokes are treated medically by stroke teams. Neurosurgery may be needed in selected cases, for example to remove a blood clot pressing on the brain, to relieve pressure from swelling (decompressive craniectomy) or to drain fluid that has built up. Emergency surgery takes place in hospital.

After the emergency, the neurosurgeon may follow you up to look for and treat the cause of the bleeding, review imaging, plan any further surgery such as cranioplasty, and coordinate with stroke physicians and rehabilitation services.