What Is an Aneurysm?
An aneurysm is a bulge that forms in the weakened part of a blood vessel wall.
Reasons for Brain Aneurysm Formation
When the blood flows through cerebral blood vessels, it exerts increased pressure on the weakened parts of the blood vessel thus leading to the formation of a brain aneurysm.
Other specific cause includes:
- Congenital (present at birth)
- High blood pressure
- Atherosclerosis
- Head trauma
What Are the Types of Cerebral Aneurysm?
- Saccular aneurysm, also known as a berry aneurysm, is the most common type of cerebral aneurysm. It is a blood-filled round sac-like protrusion from the walls of the main artery or one of its branches.
- Fusiform aneurysm in which the bulge is not restricted to just one side of the wall but is present all around.
- Mycotic aneurysm which is very rare and is the result of an infection. Infection of the vessel wall causes weakening which results in aneurysm formation.
What Are the Symptoms of Cerebral Aneurysm?
The symptoms depend on whether the aneurysm has ruptured or not.
Ruptured Aneurysm
A sudden onset headache that is severe in nature is the most commonly reported symptom. This headache is often described by people as the worst headache of their lives.
Along with the headache, other symptoms can be experienced:
- Vomiting sensation or actual vomiting
- Neck stiffness
- Blurry vision
- Seizure
- Losing consciousness
- A confused mental state
- Droop in eyelids
- Eyes feel sensitive to light
Leaking Aneurysm
This often precedes a rupture. Here, the aneurysm develops a leak and as a result some blood leaks into the surrounding tissues. When this happens, the rupture that follows will be severe. A ruptured aneurysm follows a leaking aneurysm after a few days or weeks.
- Sudden onset severe headache that can last from several days to two weeks is a symptom of a leaking aneurysm.
Unruptured Aneurysm
This type will not show any symptoms, especially if the aneurysm is small. However, a large aneurysm, which exerts pressure on surrounding tissues and nerves, might exhibit the following symptoms:
- Distended pupil
- Pain above and behind an eye
- Vision is affected
- Ptosis
Consequences of an Aneurysm Rupture
When an aneurysm ruptures, blood will leak into surrounding tissue leading to many symptoms, the most prominent of them being a thunderclap headache.
A number of health conditions may result because of a rupture.
Subarachnoid Haemorrhage:
This is bleeding in the arachnoid layer, or the part that surrounds the brain. The most common cause of this haemorrhage is a ruptured aneurysm.
SAH can result in a number of other complications:
Vasospasm: Here, restriction in the size of the blood vessels leads to lower oxygen supply to the brain.
Hydrocephalus: Accumulation of cerebrospinal fluid or blood around the brain exerts pressure on the brain.
Seizure: This refers to undisciplined electrical activity that can further damage the brain after an aneurysm ruptures.
Coma: Loss of consciousness which can go on for weeks.
Death: 50% of ruptured aneurysms are fatal.
Reasons for Aneurysm Rupture
Hypertension or increased blood pressure is the most common reason for rupture. This is because when the blood pressure is high, the force exerted on blood vessels’ walls is also more. Hence, anything that can increase blood pressure can result in an aneurysm rupture. An increase in blood pressure can be due to:
- Stress or any strong emotion like anger
- Straining to lift something
- Untreated hypertension
Many factors determine whether an aneurysm is likely to burst, including:
Size:
Aneurysms that are small have lower chances of rupturing.
Growth:
An aneurysm that has increased in size with time is more likely to rupture.
Location:
Aneurysms in the front portion or back portion of the brain have increased chances of rupturing.
Age:
The elderly (over 70 years) are more at risk for aneurysm rupture.
Other than the above, those who have a history of aneurysm rupture or have multiple aneurysms have the highest risk of aneurysm rupture.
Diagnosis of Brain Aneurysm
Some people with unruptured brain aneurysms will not show any symptoms. The aneurysm might be discovered accidentally in a brain imaging test that was probably undertaken for a different reason. However, if symptoms (like severe headache) are experienced, your doctor might advise the following tests to check for aneurysm rupture:
CT Scan:
This test utilizes x-rays and computers to produce cross-sectional brain images and will most probably be the first test advised. This test can check for blood leakage from the aneurysm. A CTA (CT angiogram) might also be recommended which will give an even more detailed picture and can reveal the size, location and status of the aneurysm.
MRI Scan:
A magnetic resonance imaging scan uses magnets, radio waves and computers as part of the diagnostic process to confirm an aneurysm. A magnetic resonance angiogram (MRA) will be useful in revealing more details about the aneurysm like size, location, etc.
Cerebral Angiography:
Here, a catheter is inserted via a blood vessel in the wrist or groin and guided to the brain to get images which can reveal the presence of aneurysm or blockages.
Treatment Options:
There are two treatment modalities for treating a ruptured aneurysm which can also be applied to unruptured ones.
Surgical Clipping
Here, the blood vessel feeding the neck of the aneurysm is clipped off with a metal clip and blood flow into it is stopped. This is a very effective method used by neurosurgeons to treat aneurysm and when treated like this, the aneurysm doesn’t recur. However, the risks of this treatment include bleeding into the brain and cutting off the blood supply to the brain. The recovery period after surgical clipping is typically 4-6 weeks.
Endovascular Treatment
Coiling for Brain Aneurysm: Here too, the blood entering the vessel is stopped but the procedure is different. An interventional neuroradiologist slides a catheter through a blood vessel in the wrist or groin and guides it to the affected blood vessel in the brain. On reaching the aneurysm, a small soft wire coil is placed which changes the blood flow pattern leading to the formation of a clot. This clot prevents blood from entering the aneurysm.
Flow Diversion Stents: Here again, an interventional neuroradiologist guides a catheter to the brain from the wrist or the groin. On reaching the aneurysm, a mesh tube is placed which prevents blood from entering it and diverts the blood away.
After Endovascular Coiling
The patient will be shifted to the recovery room or the ICU after the procedure. The patient has to lie down flat for 12-24 hours after the procedure.
If the procedure was done for a ruptured aneurysm, the patient will be moved to the ICU and kept under observation.
If the procedure was done for an unruptured aneurysm and the patient is recovering well, he/she will be discharged after 24-48 hours.
Risks of Endovascular Coiling
Blood Clots: Formation of blood clots within the catheter, coil, stent or blood vessel is a possibility. These clots can travel and block a smaller artery resulting in a stroke. By giving heparin,the risk of clot formation can be reduced. While 8% of cases suffer a clot, only 3% suffer a stroke.
Aneurysm Rupture: Here, the aneurysm is punctured by the instruments used like a catheter, coil, etc. This is more common in ruptured aneurysms.
Vasospasm: The blood vessel can narrow as a result of some kind of irritation from catheter manipulation. Medication or angioplasty can treat vasospasm.
Coil Position: The coil placed to treat the aneurysm can protrude into the parent blood vessel resulting in its narrowing. Using a stent or a balloon, the coil can be repositioned properly. Coil moving out of its position after the procedure is quite rare.
Incomplete Occlusion: Here, the coil does not fill the aneurysm and a residual neck is left through which blood can re-enter and the aneurysm can recur.
Follow-Up
The patient needs to come for a follow-up after 2 weeks/4 weeks/3 months/6 months/1 year post-procedure.
Dr Periakaruppan
Senior Interventional Radiologist,
Kauvery Hospital Chennai
