HYDERABAD:Cerebral Aneurysm is an outpouching or ballooning of a part of blood vessel inside the brain due weakness in the wall. Aneurysms usually develop at branching points of arteries and are caused by constant pressure from blood flow. They often enlarge slowly and become weaker as they grow, just as a balloon becomes weaker as it stretches. Eventually, the aneurysm may rupture or burst resulting in brain hemorrhage. Brain aneurysms can occur in anyone and at any age. They are most common in adults between the ages of 30 and 60 years.
What are the risk factors for aneurysm formation?
Risk factors you can control
l High Blood Pressure.
l Smoking.
l Drug abuse – especially cocaine, amphetamines.
Risk factors you cannot control
l Ageing – Risk of aneurysm formation increases with advancing age because of long standing exposure of blood vessel wall to the jet of blood.
l Gender – Women are more likely than men to develop a brain aneurysm.
l Trauma – Injury to the head or neck resulting in tear or weakness in the wall of the blood vessel.
l Inflammation – irritation of the blood vessel vessel (multifactorial) resulting in weakness of wall. Infections in the blood or valves of the heart.
l Familial / Genetic – Some individuals and families have an inherent risk because of defect in the strength of the wall around blood vessel.
When should a brain aneurysm be suspected?
Most cerebral aneurysms do not show symptoms until they either become very large or rupture. An unruptured aneurysm may go unnoticed throughout a person’s lifetime and may not cause any symptoms.
A steadily growing aneurysm may press on adjacent brain tissue and nerves causing:
l Pain behind the eye.
l Drooping of upper eyelid.
l Double vision.
l Inability to see objects clearly (blurring of a part of the field of vision).
l Numbness or weakness of one half of body or one limb.
l Difficulty in balancing while walking.
l Seizures
l Recurrent minor strokes resulting from dislodgement of a small blood clot from within the aneurysm (temporary weakness of one half of body or, inability to understand or speak, fainting episodes).
A sudden onset thunderclap headache is suggestive of bleeding from rupture of aneurysm. Headache may be associated with nausea, vomiting, sensitivity to light, stiff neck, seizures or fainting. This is a medical emergency!
Sometimes an aneurysm may leak a small amount of blood into the brain (called a sentinel bleed) days or weeks prior to a major rupture. Such patients experience minor headache which may or may not be associated with nausea, vomiting or light-headedness. However, only a few individuals experience these warning symptoms.
What causes an aneurysm to bleed?
The exact factor which is predisposes to rupture of aneurysm is not known. Strong emotions such as being upset or angry, straining at stools (in patients with chronic constipation), sexual activity lead to a sudden rise in blood pressure which might result in rupture of a pre-existing aneurysm.
What are the chances that an unruptured aneurysm may bleed?
There is no way to predict accurately the chance of rupture of an aneurysm which has been found incidentally. The following factors predict that the aneurysm has a higher likelihood of rupture. However it must be noted that aneurysm of any size, shape and location can rupture.
l Size > 7mm for aneurysms located in the front portion of the brain circulation.
l Shape – Irregular shaped aneurysms are more likely to rupture than the regular shaped ones.
l Patients with multiple aneurysms and those with history of a ruptured aneurysm in the past.
l Patients with underlying problems in the framework that supports the blood vessel (collagen vascular diseases) or genetic conditions like polycystic kidney disease.
l Location: an aneurysm located in the back of the head has a higher risk of rupture than those located in the front.
How is an aneurysm diagnosed?
If bleeding from rupture of aneurysm is suspected, then a CT scan of the brain is performed followed by one of the following three modalities to confirm the presence of aneurysm in the brain.
l CT angiography
l MR angiography
l Digital Subtraction Angiography (DSA) of the brain, which is the most reliable way to detect all types and sizes of cerebral aneurysms.
In certain circumstances, a spinal tap may be performed to collect and analyse cerebrospinal fluid in order to confirm the presence of subarachnoid haemorrhage.
In about 5-10% of cases, the source of bleeding may not be seen on the initial angiogram. In such cases, one has to undergo a repeat angiogram after a period of 6-8 weeks to rule out an underlying aneurysm.
How are brain aneurysms treated?
Every patient with aneurysm is different. Hence, treatment is tailored to an individual and outcomes vary between individuals. Management of brain aneurysm depends on whether they have ruptured and caused brain hemorrhage or not.
The aim of treatment in a ruptured aneurysm is to prevent another episode of bleed by securing the aneurysm with open surgical or endovascular techniques. The choice of technique depends on aneurysm related factors, available expertise and the health care facility. In addition to brain damage, other organs like heart and lungs can be indirectly affected from the brain haemorrhage. Such patients require prolonged treatment in the intensive care unit.
Treatment of unruptured aneurysms is relatively less complicated because the late consequences that result from brain haemorrhage are eliminated.
What are the various treatments available?
Medical therapy:
l Control of blood pressure.
l For untreated small aneurysms with low risk for rupture (which cannot be predicted with certainty), regular follow up with an angiogram of the brain is recommended.
l Anti-seizure medications – to control fits.
l Medications to reduce the risk of vasospasm (narrowing of blood vessels).
Open surgery:
l Clip occlusion to prevent blood from entering the aneurysm.
l Clip reconstruction of the parent vessel – for complicated aneurysms.
l Trapping of the segment of blood vessel containing the aneurysm [with or without addition of a by-pass procedure]
Endovascular techniques:
l Sealing the aneurysm sac by filling coils within it [may require stent or balloon assistance].
l Flow Diversion.
l Parent [main] blood vessel occlusion.
Is follow-up required after treatment of an aneurysm?
Any aneurysm that has been treated can regrow, although it happens in 5-10% of patients who have been treated. New aneurysms can form in other sites in individuals who are predisposed. Similarly, aneurysm may not heal immediately following certain treatment modalities like flow diverter placement. Hence the follow up is mandatory. The interval for follow up and the imaging modality is decided by the treating doctor on a case to case basis.
The author is a Consultant Neuro Surgeon, Apollo Hospitals, Hyderabad.