A weak or fine spot on a blood vessel in the brain that balloons out and fills with blood is called as a cerebral aneurysm a.k.a. intracranial/intracerebral aneurysm. Pressure may be exerted on a nerve or surrounding brain tissue by the bulging aneurysm. Also, it can leak or rupture, spilling blood into the neighbouring tissue (known as subarachnoid haemorrhage or SAH). Few cerebral aneurysms don’t bleed or cause other issues, especially those that are very tiny. These are incidentally detected in the course of investigation done for some other reason. Cerebral aneurysm can occur anywhere in the brain, but majority are located along a loop of arteries running between the underside of the brain and skull base (Circle of Willis).

Aneurysms may be a result of an abnormality in an artery wall that is congenital. Cerebral aneurysm is observed more commonly in people having particular genetic diseases, like connective tissue disorders and polycystic kidney disease, and specific circulatory disorders such as AVM i.e. arteriovenous malformations ( knotted tangles of veins and arteries in the brain that disrupt the flow of blood). Other causes can be trauma or head injury, high BP, infection, tumours, atherosclerosis and other diseases of the vascular system.

Cerebral aneurysm is of 3 types.
A rounded or pouch-like sac of blood attached by a neck or stem to an artery or a branch of a blood vessel is called a saccular aneurysm a.k.a. berry aneurysm (due to its resemblance to a berry hanging from a vine). It is the most commonly occurring form of cerebral aneurysm and is usually found on arteries at the base of the brain. It usually occurs in adults. A lateral aneurysm is seen as a protuberance on one wall of the blood vessel, whereas a fusiform aneurysm is formed by the broadening along the blood vessel walls.

Size is also a used to classify aneurysms. Small aneurysms are not more than 11 mm in diameter (around the size of a large pencil eraser), larger aneurysm are around 11-25 mm (about a coin’s width), and giant aneurysms are greater than 25 mm in diameter.

Brain aneurysms can happen to anyone and at any age. It is observed more commonly in adults than in children and its frequency is slightly more in women than in men. Higher risk is present in people with certain inherited disorders.

Haemorrhagic stroke, permanent brain damage and other serious complication or even death can be caused due to aneurysm that may burst and bleed into the brain. After bursting once, the aneurysm can even burst again. The re-rupture is typically devastating and can be life threatening. More grave post rupture complication of brain haemorrhage is vasospasm. In vasospasm, other blood vessels in the brain contract and restrict the flow of blood to essential areas of the brain. This decreased flow of blood can cause stroke or tissue damage. Hydrocephalus is another serious complication of subarachnoid haemorrhage. In this condition, excessive accretion of cerebrospinal fluid in the skull widens fluid pathways called ventricles that can bloat and exert pressure on the brain tissue.

Symptoms are absent in most cerebral aneurysms until they either become large or burst. Aneurysms that are small and unchanging generally won’t produce symptoms. On the other hand a larger aneurysm growing steadily may exert pressure on tissues and nerves. The symptoms are pain above the eye as well as behind it, weakness, numbness, or paralysis on a single side of the face; dilation of pupils and changes in vision. When there is haemorrhage of an aneurysm, the person may experience an expected and extremely severe headache, vision problems, nausea, stiff neck and / or loss of consciousness. The headache is especially excruciating and is usually different in degree and intensity from other headaches. Sometimes an aneurysm leaks for days to weeks before it ruptures. During this period, “Sentinel” or warning headaches may be felt. Only a few people have sentinel headache before an aneurysm rupture.

Some other signs that a cerebral aneurysm has burst are nausea and vomiting along with severe headache, drooping eyelid, increased sensitivity to light, and confusion. Some people may experience seizures too. When people experience these symptoms or along with a combination of other symptoms, they should seek medical attention immediately.

Majority of cerebral aneurysms go undiscovered until they rupture or are detected by brain imaging which may have been suggested for some other condition. Many diagnostic methods are available to guide and give information about the aneurysm and the best method of treatment. The tests are generally done following a subarachnoid haemorrhage, for confirmation of the diagnosis of an aneurysm.

Computed tomography (CT) of the head is a quick, pain free, non-invasive diagnostic tool that can reveal if a cerebral aneurysm is present and find out, for those aneurysms that have a burst, if there is blood leak into the brain.

Angiography is a dye test that is used to examine the arteries or veins. It is a significant diagnostic test in brain stroke management and accurately determines the shape size, location of the aneurysm, or the blood vessel that has bled.

MRI i.e. magnetic resonance imaging produces detailed images of the brain by using computer-generated radio waves and strong magnetic field. Images of blood vessel is produced using MRA (Magnetic resonance angiography). The images may be viewed as either 3 – dimensional pictures or 2 – dimensional cross slices of the brain and vessels. These pain free non-invasive procedures can help in understanding the size and shape of an aneurysm and to detect bleeding in the brain.

These are few surgical options available for the treatment of cerebral aneurysms –

i) Microvascular clipping is a procedure in which the blood flow to the aneurysm is cut. Once anaesthesia is administered, a portion of the skull is removed and the aneurysm is located. Using a microscope, the blood vessel that feeds the aneurysm is isolated and a small, metal, clothespin-like clip is placed on the aneurysm’s neck, cutting off its blood supply. The clip stays in the person preventing the risk of future bleeding. After replacing the piece of skull, the scalp is closed. It is found that clipping is highly effective, depending on the aneurysm’s location, shape and size. Usually, aneurysms that are surgically clipped completely do not return.

Occlusion is a related procedure, in which the entire artery that leads to aneurysm is clamped off (occluded). This procedure is usually carried out when the artery has been damaged by an aneurysm. An occlusion can be accompanied by a bypass, in which a tiny blood vessel is grafted surgically to the artery of the brain, rerouting the blood flow away from the portion of the damaged artery. This bypass procedure is usually carried out for giant aneurysms, where it is not possible to clip the aneurysm directly and parent artery needs to be permanently blocked.

ii) Endovascular embolization is a substitute for surgery. Once the patient is under anaesthesia, the physician inserts a catheter (long thin plastic tube) into an artery (generally in the groin) and threads it, using angiography, through the body to the aneurysm site. Detachable coils are passed through the catheter using a guide wire and released into the aneurysm. The aneurysm is filled with coils, blocking its blood circulation and causing blood to clot which in turn destroys the aneurysm.

iii) Other treatments for cerebral aneurysm are to control the symptoms and can involve anticonvulsants for preventing seizures and analgesics for treating headache. It is possible to treat vasospasm using calcium channel-blocking drugs. Also, if the person is restless, sedatives may be administered. A shunt can be inserted surgically into a ventricle many months after the rupture if the cerebrospinal fluid build up is causing harmful pressure on surrounding tissue. People who have experienced a subarachnoid haemorrhage usually require speech, rehabilitative and occupational therapy to regain lost ability and learn to cope with any disability that is permanent.

There are no known ways to prevent formation of cerebral aneurysm. If diagnosed with a cerebral aneurysm, the person should keep his blood pressure under control and avoid smoking, cocaine use or other stimulant drugs. Also consult with a doctor about the taking medicines such as aspirin or other drugs that are blood thinners. Women should enquire with their physicians about the use of oral contraceptives.