Neurological Disorders: Brain Aneurysm

Brain aneurysm (cerebral aneurysm) is a localized bulge or dilatation in the wall of a blood vessel especially an artery supplying the brain. This causes a weakness of the artery wall with a tendency to rupture and bleed.

Certain cerebral aneurysms are serious conditions and can cause catastrophic brain hemorrhage.

• Congenital (born with a problem)
• Acquired (disease develops after birth)

In the congenital type the berry or saccular aneurysm is the most important.

In the acquired type the following are some important types;

• Atherosclerotic aneurysm
• Mycotic aneurysm
• Miliary aneurysm (Charcoat-Bouchard Aneurysm)

Berry or saccular aneurysm:

They occur mostly in the large arteries of the brain especially in the region of circle of willis. This is nothing but somewhat circular shaped arterial network produced by anterior and posterior circulation of the brain along with some interconnecting or communicating branches.

The anterior circulation of the brain is provided by carotid arteries and they mainly supply the anterior (front) aspect of the brain.

The posterior circulation of the brain is provided by vertebrobasilar arteries and they mainly supply the posterior (back) aspect of the brain including the cerebellum and brain stem.

Some of the deeper structures of the brain are supplied by both anterior and posterior circulations.

Majority of the berry aneurysms occur in the anterior circulation. Incidence is high in adult age. Women are affected bit more than men.

This kind of aneurysm are congenital in nature (somebody born with it) however they most often do not present until mid-adult life. Patients with Ehrler Danlos or Marfan syndrome, Polycystic kidney disease etc can develop this type of aneurysm. Some cases are familial.

A rupture of berry aneurysm causes subarachnoid hemorrhage with a high risk of death. Symptom of the worst headache of one’s life is highly characteristic although not specific for this condition .

Miliary (Charcoat-Bouchard Aneurysm):

This is the result of chronic high blood pressure and occurs usually in the small caliber deep penetrating arteries of the brain. They too can rupture and cause serious bleedings.

The atherosclerotic aneurysms:

They are also called as fusiform aneurysms. They generally occur in the posterior circulation and in older people, obviously because the altheroclerosis is common in this population. Although they too can rupture and bleed but the main concern with these aneurysms are stroke causes by thrombosis (clot) formation in these aneurysms. They can also produce compression effect on the brain.

Mycotic aneurysms:

These brain aneurysms are secondary to the infection of the wall of an artery. This is commonly seen in the setting of infectious endocarditis (heart infection). If they rupture in addition to bleeding they can spread the infection to the brain resulting in focal encephalitis, brain abscess etc.

Clinically speaking acutely evolving excruciating headache with decreased level of consciousness and/or focal neurological deficits are some of the very characteristic symptoms of brain aneurysms that draws the attention of a physician towards this diagnosis.

Investigations usually begin with a non contrast head CT. Later MRI, MRA, CTA & conventional angiograms are usually necessary (a single patient may not require all these tests).

If the patient presented with acute bleeding then hospitalization is necessary. Cerebral vasodilators like nimlodipine are generally used in berry aneurysm related bleeding (subarachnoid hemorrhage).

The aneurysm itself may require a surgical or interventional radiology treatment including resection, coiling, clipping etc.

Aneurysms of the brain are managed commonly by both neurologists and neurosurgeons.