Understanding Brain Aneurysm

The recent canonisation of Pope John Paul II was hailed as a global historical event, however it also highlighted a serious medical condition which the late Pope is said to have healed miraculously- intracranial aneurysm.

An intracranial aneurysm (also called cerebral or brain aneurysm) is a cerebrovascular disorder in which weakness in the wall of a cerebral artery or vein causes a localised dilation or ballooning of the blood vessel.

Almost 500,000 deaths worldwide each year are caused by brain aneurysms and half the victims are younger than 50 and the ratio of men versus women is 3:2. Women over the age of 35 are particularly exposed to the risk. In fact, results of various studies shows that females are up-to two times more likely to develop cerebral aneurysms compared with males. A recent report from the Institute of Medicine (IOM), arm of the National Academy of Sciences confirms that there are several instances of sex differences in the incidence and sign of cerebrovascular disease and trauma that warrant further investigation. Smoking, high blood pressure, and a family history of brain aneurysms seem to further increase a woman’s risk of developing this potentially fatal condition.

What is cerebral aneurysm?

Dr Vipul Gupta

An aneurysm is an outpouching from the blood vessel or dilatation of the blood vessel that has a potential for rupture or other related complications. Almost five per cent of adult population can have an aneurysm. They do not have a single cause. Common causes are of intracranial aneurysms are vessel degeneration from haematologic factors, atherosclerosis, high flow states, underlying vascular disorders, trauma, infection drug abuse and neoplastic invasion. Disorders associated with aneurysm formation include hypertension, aortic coarctation, adult polycystic kidney disease, fibromuscular dysplasia, connective tissue disorders and Moyamoya disease. In most cases, a brain aneurysm causes no symptoms and goes unnoticed. In rare cases, the brain aneurysm ruptures, releasing blood into the skull and causing a stroke. The most common location for brain aneurysms is in the network of blood vessels at the base of the brain called the circle of Willis.

Aneurysm facts

• Ruptured brain aneurysms are fatal in about 40 per cent of cases. Of those who survive, about 66 per cent suffer some permanent neurological deficit.
• Brain aneurysms are most prevalent in people ages 35 – 60, but can occur in children as well. The median age when aneurysmal haemorrhagic stroke occurs is 50 years old and there are typically no warning signs. Most aneurysms develop after the age of 40.
• Women, more than men, suffer from brain aneurysms at a ratio of 3:2.
• Ruptured brain aneurysms account for five per cent of all new strokes.
• Accurate early diagnosis is critical, as the initial haemorrhage may be fatal, may result in devastating neurologic outcomes, or may produce minor symptoms. Despite widespread neuroimaging availability, misdiagnosis or delays in diagnosis occurs in up to 25 per cent of patients with sub-arachnoid haemorrhage (SAH) when initially presenting for medical treatment. Failure to do a scan results in 73 per cent of these misdiagnoses.
• There are almost 500,000 deaths worldwide each year caused by brain aneurysms and half the victims are younger than 50

Problems caused by aneurysms

The most feared complication caused by aneurysm is sub-arachnoid haemorrhage (SAH). Sometimes aneurysms occur due to mass effect and unusually due to thrombo-embolic phenomenon.

Why is treatment of SAH an emergency?

SAH is always an emergency because ruptured cerebral aneurysms continue to be a significant cause of death as well as a health and economic problem which can be significantly reduced if treated early. It is an important cause of mortality and morbidity because young and middle-aged adults are most often affected. Studies to date show peaks at various ages in the 40-70 year range. An estimated 12 per cent of patients die before reaching the hospital. Epidemiological studies estimate that about 40 per cent of those reaching hospital die.

Re-bleed due to re-rupture of aneurysm is a very important factor, which makes early treatment all the more important. With modern surgical and interventional (endovascular) techniques, most of the aneurysms can be treated with reasonable safety. The peak risk of re-bleed is within the first 24 hours after SAH, thereafter the rate declines to 1.5 per cent per day, with a cumulative risk of 19 per cent in the first two weeks. Early treatment in selected cases not only prevents morbidity and mortality due to re-bleed but also enables aggressive treatment of secondary complications such as vasospasm and hydrocephalus.

What are the common signs and symptoms of SAH?

Hallmark of SAH is a sudden, usually severe headache and about 80 per cent patients give such a history. Sentinel headaches may occur a few hours to a few months before the rupture, with a reported median of two weeks prior to diagnosis of SAH. Headache of SAH is usually typical but sometimes is variable as to render the diagnosis difficult. Most common incorrect diagnosis in order of decreasing frequency are systemic infection or viral illness, migraine, hypertensive crisis, cervical spine disorder such as arthritis or herniated disc, brain tumour, aseptic meningitis, sinusitis and alcohol intoxication.

Ominous features associated with headache are vomiting, alteration in consciousness, meningism, seizure or focal neurologic deficit. Physical examination findings may be normal, or the clinician may find some focal neurological deficits. There might be varying degrees of level of unconsciousness depending on the grade of the patient. Patients usually have nuchal rigidity as a sign of meningism. The focal deficit usually pertains to the vascular territory involved, like bilateral lower limb weakness in anterior cerebral artery territory or hemiparesis in middle cerebral artery territory or third nerve palsy in posterior communicating artery territory.

What are the investigations needed?

Computed tomography (CT)

This test should be the first investigation to be performed particularly to look for presence for bleeding. In most of the cases, CT will show evidence of blood in sub-arachnoid space although one should be aware that three per cent of patients might have normal scans within 24 hours of confirmed SAH. CT scan also helps in diagnosis of associated intraventricular haemorrhage, intra-cerebral haemorrhage, as well as for presence of mass effect, ischemic changes and hydrocephalus. With passage of time, sensitivity of CT to detect SAH in a patient decreases and by Day-five, significant number of patients may have normal CT in spite of the presence of bleed and aneurysm.

Lumbar puncture (LP)

Lumbar puncture is done to detect RBCs and xanthochromia as an evidence of SAH. LP is indicated in case where the clinical history is strongly suggestive of SAH with a negative CT or the patient presents many days after the episode with a negative CT scan.

Magnetic resonance imaging (MRI)

Although some reports show that MR can detect acute haemorrhage, CT should always be done first to rule-out haemorrhage.

Catheter angiography (DSA- digital subtraction angiography)

This is the most accurate investigation in diagnosis and evaluation of aneurysms causing the SAH. Cerebral angiography is performed once the diagnosis of SAH is made. This study assesses the ruptured aneurysm, vascular anatomy, presence of other aneurysms and secondary vasospasm. In particular, 3-D DSA is most accurate in evaluating assessment of intracranial aneurysms.

CT/MR angiography

Although CT/MR angiography can detect intracranial aneurysms, its sensitivity in detection of small intracranial aneurysm is poor.

What are the various types of treatment for intracranial aneurysms?

Aneurysms can be treated by endovascular and surgical techniques. The primary goal of treatment is complete, permanent and safe aneurysm occlusion.

Surgery

Surgery has been the conventional method of aneurysm treatment. Surgery entails direct exposure of the aneurysm, the parent vessel(s) and surrounding structures. The aneurysm is then secured by the placement of a metallic clip along the neck thereby excluding it from the circulation. Problems with surgery include invasiveness and trauma to normal brain parenchyma. Surgery has an edge over the endovascular method in cases of large haematoma or hydrocephalus where a decompression would always benefit the patient.

Endovascular coiling of aneurysms

In this treatment a micro-catheter is placed from one of the leg arteries into the aneurysm, which is then occluded with coils (usually detachable platinum coils) so as to prevent repeat bleeding. A recent randomised, multi-centre trial conducted in Europe and North America has shown that long-term clinical results were better with embolisation than open surgery in certain subset of patients. Endovascular treatment is usually the treatment of choice of patients with surgically poorly accessible aneurysms (posterior circulation, cavernous ICA aneurysms), in patients with medical risk factors and in patients with poor clinical status after the bleed. 

How is coiling procedure performed?

Cerebral aneurysm surgery

The procedure is done under general anaesthesia. A guide catheter is placed through in one of the femoral (leg) vessel into the appropriate parent vessel. Multiple angiograms are done to localise the aneurysm and to assess its morphology. 3-D angiogram is of great help in this process and it guides the interventional radiologist in selecting the approach. A microcatheter is carefully navigated into the aneurysm under roadmap guidance. An appropriate sized coil is then placed into the aneurysm. Specially shaped coils (such as 3-D coils) are available for this purpose. Angiogram is done to confirm the placement of the coil before it is detached. This detachment is usually done by electrolytic method, sometimes by mechanical means. Further, the aneurysm is packed by placing more coils until complete occlusion is achieved. Patient is brought out of general anaesthesia depending upon the clinical situation. Patient always need follow-up angiograms to assess the stability of occlusion. Unusually, aneurysm may re-canalise or grow and patient may need a repeat procedure.

Why is it important to manage such patients in specialised centres?

A comprehensive stroke centre is defined as a facility or system with the necessary personnel, infrastructure, expertise, and programmes to diagnose and treat patients who require a high intensity of medical and surgical care, specialised tests, or interventional therapies. This kind of a centre has:

• Stroke team/physicians
• Diagnostic techniques such as MRI, CT (with CT angiography), digital subtraction angiography (DSA) and transcranial Doppler.
• Surgical and interventional therapies- well established surgical procedures such as haematoma removal, clipping of aneurysms as well as interventional neuroradiology and endovascular therapy
• Infrastructure such as neurosurgical ICU, and round-the-clock interventional and surgical facilities

Studies have shown that patients treated in stroke centres have better outcomes as compared to patients treated in regular hospitals. Results of both surgery and intervention are also largely dependent upon the expertise of the treating physician. Effective management in a stroke centre with a team of doctors specialising in different aspects is important because patients with SAH are prone to secondary complications, which can cause delayed onset of worsening after SAH.

These include:

• Cerebral ischemia due to vasospasm – Symptomatic vasospasm is narrowing of vessels that have resulted in cerebral ischemia with clinical symptoms and signs. Angiographic vasospasm is arterial narrowing demonstrated on angiography after SAH and overall incidence of this is about 50 per cent Almost 60 per cent of patients with thick clots develop moderate or severe angiographic vasospasm in at least one major artery.
• Hydrocephalus
• Hyponatremia
• Hypoxia/ hypotension from cardiopulmonary complications
• Systemic sepsis, meningitis
• Cardiovascular complications- such as ECG abnormalities are quite common in these patients. Unusually, they may be associated with underlying cardiac damage manifest as contraction band necrosis and elevated cardiac enzymes.

Results of coiling are better than surgical clipping International subarachnoid Aneurysm trial (ISAT Trial)

• Randomised, prospective, international controlled trial compared neurosurgical clipping with endovascular treatment in aneurysms and concluded that results of coiling were better than surgical clipping .
• The early survival advantage was maintained for upto seven years and was significant.

The Barrow Ruptured Aneurysm Trial (BRAT Trial)

• Endovascular coil embolisation is superior to microsurgical clipping.

References

• Molyneux AJ, etal; International Subarachnoid Aneurysm Trial (ISAT) Collaborative Group International subarachnoid aneurysm trial (ISAT) of neurosurgical clipping versus endovascular coiling in 2143 patients with ruptured intracranial aneurysms: a randomised comparison of effects on survival, dependency, seizures, rebleeding, subgroups, and aneurysm occlusion. Lancet 2005;366:809-17
• Risk of recurrent subarachnoid haemorrhage, death, or dependence and standardised mortality ratios after clipping or coiling of an intracranial aneurysm in the International Subarachnoid Aneurysm Trial (ISAT): long-term follow-up. Lancet Neurol. 2009 May ; 8(5): 427–433.