Intracranial aneurysms: The ticking time bomb

MANY of us would have heard someone say “mine yuh blood vessel buss inna yuh head” when they are trying to calm someone who is hot-tempered. This term is in reference to a ruptured aneurysm, which is often fatal.

But what are aneurysms? Dr Duane Patten, consultant neurosurgeon and complex spine surgeon at Island Surgical Partners, said an intracranial aneurysm is an abnormal “ballooning” of the arterial blood vessels of the brain.

According to Dr Patten, anyone can get an aneurysm; however, he pointed out that there are genetic and environmental factors that modify each person’s risk of getting an aneurysm.

“Penetrating trauma to the head and infections can also cause aneurysms, but are of a different pathological spectrum. There is currently no up-to-date literature on the prevalence of intracranial aneurysms in Jamaica; however, extrapolation from North American data would put the prevalence between three to five per cent of the population,” he said.

Of note, Dr Patten explained that the vast majority of aneurysms are asymptomatic, meaning no notable symptoms occur.

“If we use the higher end of the prevalence spectrum, approximately 150,000 people would have aneurysms in Jamaica; however, the annual incidence of aneurysm rupture is in approximately 10:100,000. This works out to 300 people per year, so less than one per cent of intracranial aneurysms become symptomatic per year.”

Further, Dr Patten said symptoms from an aneurysm are due to rupture of the aneurysm and compression of the surrounding neural structures.

“The typical symptom from a rupture is a sudden onset severe headache, described as a thunderclap headache. Depending on the extent of the rupture the person can have difficulty speaking, weakness of the limbs, seizures, or even become comatose. The most common compressive symptom is on the third cranial nerve. This nerve travels from the brainstem to the eyes. During its course, it traverses a lot of intracranial vessels, and if one of those vessels has an aneurysm, it compresses the nerve resulting in double vision due to weakness of the muscles that makes the eye move,” he pointed out.

What’s more is that it is difficult to suspect someone is having an aneurysm.

“Unfortunately an intracranial aneurysm is called a ticking time bomb. They are usually asymptomatic until they suddenly rupture and become symptomatic. Asymptomatic aneurysms are also found incidentally when the patient is being scanned for another reason,” Dr Patten said.

He added: “We know there are risk factors — both genetic and environmental — that increases the risk of acquiring an intracranial aneurysm. Patients in high-risk groups should be screened for intracranial aneurysms — that’s the only way to diagnose them prior to rupture. Diagnosing an aneurysm is done using imaging techniques, include a Computed Tomography Angiogram (CTA), Magnetic Resonance Imaging and Angiogram (MRI/MRA) or a catheter angiography, where contrast (a dye that can be seen on X-ray) is injected directly into the blood vessels and X-ray images taken.”

Dr Patten said recently the concept of aneurysm screening has been discussed. He noted that recommendations are still controversial; however, patients with two or more relatives with an aneurysm or identical twins where one has an aneurysm, should be screened. Other high-risk groups that should be screened are patients with genetic disorders of connective tissue.

“The connective tissue helps to form the wall of blood vessels, and patients with disorders that affect it will be more prone to have intracranial aneurysms. These disorders include Ehlers-Danlos syndrome, Marfan syndrome, fibromuscular dysplasia and polycystic kidney disease. Screening should start in the early 20s and occur every five to 10 years,” he said.

Additionally, Dr Patten said risk factors for developing intracranial aneurysms can be broken down into genetic and acquired.

“Genetic factors include the connective tissue disorders previously mentioned. Acquired risk factors include smoking, hypertension and alcoholism. There are other genetic factors that are not fully understood that increase the risk of getting an aneurysm,” he said.

“The best way to prevent yourself from getting an aneurysm is to avoid the environmental risk factors. Do not smoke or consume excessive amounts of alcohol. The genetic factors cannot be changed. However, even with avoiding all risk factors, an intracranial aneurysm can still develop. Women are affected more than men (3:2), blacks are affected more than whites (2:1).”

Dr Patten emphasised that the majority of aneurysms do not rupture and people and live their entire lives not knowing they had a “ticking time bomb” in their head.

“The issue is not surviving an aneurysm, but surviving an aneurysm rupture. When Jamaicans say ‘a blood vessel bus in a him/her head’ they are correct. The results of a ruptured aneurysm is a subarachnoid haemorrhage (SAH), this is basically blood in the spaces around the brain. Approximately 15 per cent of patients with a SAH will die before even getting to hospital. Of the patients that survive, only a third will go on to have a good outcome; the remainder will remain significantly disabled. These are figures from countries that have the resources to manage SAH effectively. I can only imagine that our figures are worse,” he said.

He said ruptured aneurysms are treated as an emergency, while unruptured or asymptomatic aneurysms can be treated electively.

“They can be treated with open surgery or endovascular treatment. Open surgery involves making an incision on the scalp, removing a portion of the skull (craniotomy), dissecting between the lobes of the brain to get to the blood vessels, and putting a clip across the aneurysm to prevent any further blood from getting into it,” he said.

“In endovascular treatment, the catheter is passed from a vessel in the groin, up to the vessels in the brain. Once the aneurysm is reached with the catheter, special flexible coils are placed in the aneurysm. This will also have the effect of preventing further blood getting in the aneurysm,” he said.

Overall, Dr Patten said it must be noted that in ruptured aneurysms, the operation or endovascular treatment is only an initial step in the overall management.

“These patients are still at risk for developing further problems due to the nature of the illness. These problems can add to the morbidity and mortality burden even after a successful operation,” he said.