What is a Cerebral Aneurysm?

The cerebral aneurysms are outpouching of brain arteries, often at a weak spot, and looks like a berry hanging on a stem. A normal arterial wall is made up of three layers. If there is an abnormal loss or absence of the muscular layer of the artery wall, leaving only two layers, an aneurysm can form. 

The most common type of cerebral aneurysm is called a saccular, or berry aneurysm, occurring in 90 percent of cases. Other types of aneurysms are fusiform and dissecting aneurysms. Fusiform aneurysms are associated with atherosclerosis (Cholesterol plaque) and dissecting aneurysms are tears along the wall of the artery, causing the blood to flow between the layers of the arterial wall. They can rupture because of trauma or in severe cases, can rupture spontaneously also.

Above: Different Types of Cerebral Aneurysm

What does an aneurysm do? 

Aneurysms can sit silently for a very long time in the brain and grow larger and larger with time before finally giving away and causing a catastrophic hemorrhagic stroke. Therefore, it is imminent to diagnose an aneurysm before it has ruptured to prevent any future disability or loss of life. 

If diagnosed early and treated, aneurysms are harmless and pose no threat to the individual or life. Unfortunately, in the majority of the cases, an aneurysm is diagnosed when it has already ruptured or the weak spot gives away leading to a brain hemorrhage (a hemorrhagic stroke), technically called a “Subarachnoid Hemorrhage”. 

The good news is that smaller aneurysms (less than 7mm) have a lower risk of rupture than the larger ones and thus if detected early, while they are still small, they can be effectively treated before they burst. 

What are symptoms of an aneurysm?

Aneurysms may cause symptoms by compression of brain structures which are usually caused by either an aneurysm close to nerves or by a large aneurysm technically known as a “Giant aneurysm”. Thus, they affect the function of that region of the brain. 

The most common symptom is the closure of one eyelid. The other symptoms can be:

• Weakness of limbs 
• Pain above and behind one eye
• A dilated pupil
• Change in vision or double vision
• Numbness of one side of the face

If a hemorrhagic stroke has occurred due to aneurysmal rupture, the symptoms depend upon the size and severity of the stroke. 

How do I identify if an aneurysm has ruptured?

When an aneurysm ruptures, it is one of the most dramatic symptoms in medicine, often described as “very severe headache” or the “worst headache of my life”. Other symptoms of subarachnoid hemorrhage are:

• Nausea and vomiting
• Stiff neck
• Blurred or double vision
• Sensitivity to light
• Seizure
• A drooping eyelid
• Loss of consciousness
• Confusion or altered mental status
• Dilated pupils
• Difficulty in moving one or more limbs or Imbalance
• Coma

It can also cause unconsciousness or the worst, sudden death.

Above: CT Scan of a Ruptured Cerebral Aneurysm

The complications that can develop after the rupture of an aneurysm include:

• Re-bleeding: An aneurysm that has ruptured or leaked is at risk of bleeding again. Re-bleeding can cause further damage to brain cells.
• Vasospasm: After a rupture, blood vessels undergo constriction (vasospasm) as a defense to decrease blood loss. This further decreases the blood supply to brain cells, causing them to die (ischemic stroke).
• Hydrocephalus: The leaked blood can block the circulation of the brain fluid (CSF) leading to an excess of fluid and increased pressure on the brain, further damaging it.
• Hyponatremia: Subarachnoid hemorrhage can damage the vital centers of the brain responsible for controlling the sodium in the body besides various other centers for our vital functions like breathing, awareness, and blood pressure control. A decrease in sodium levels (hyponatremia) can lead to swelling of brain cells and cause permanent damage.

What increases the risk of rupture of aneurysm?

While smaller aneurysms have lesser chances of rupture, there are various factors which predispose an aneurysm for rupture:

• Size more than 7 mm in diameter
• Aneurysm in the arteries supplying the backside of the brain
• Previous history of a ruptured aneurysm
• Trauma (injury) to head

How is an unruptured aneurysm diagnosed?

With the help of advanced imaging techniques used for brain scannings like CT scans, MRI, and digital subtraction angiography (done in a Cath lab), we can efficiently diagnose even small aneurysms in the cerebral arteries. Hence, timely diagnosis and treatment are possible in all cases if the patient presents to us in the early course of the disease.

Above: A catheter being guided through a small cut in the groin to an artery and then to the blood vessel in the brain where aneurysm is located.