Vital Screening advice

Many relatives of patients who have had a subarachnoid haemorrhage want to know if there is a risk that they too might be affected. In addition they want to know if it would be worth them having special tests to rule out an intracranial aneurysm. This is what we call screening, the investigation of apparently healthy people looking for an abnormality.

These questions have been the subject of medical discussion for some years and the answers are far from clear. These issues rely on answers to the following questions:

a) Do relatives of patients with subarachnoid haemorrhage from a cerebral aneurysm have a higher risk of having an aneurysm than the rest of the population?

b) If an aneurysm is found what is the risk that it could rupture and produce a life threatening brain haemorrhage?

c) What are the risks of treatment of a cerebral aneurysm that is not causing any symptoms versus no treatment and observing it?

Family members of a subarachnoid haemorrhage patient appear to have little increased risk over the general population of having an aneurysm. However, if two or more members of a family, who are first degree relatives - that is parents, siblings, or children - have had a subarachnoid haemorrhage, then the risk that other family members may have an aneurysm is much greater.

In a study of 626 first degree relatives of 160 patients who had had a subarachnoid haemorrhage, the results were as follows:

All the relatives were screened with magnetic resonance angiography scan. Twenty five aneurysms (4%) were detected.
Of these, 18 patients went on to have surgery, of which 11 were left with some form of disability. These figures would equate to 40 aneurysms found for every thousand people screened. Of these 40 people, 30 would have surgery, of which 10 to 20 would have some neurological problems afterwards as a consequence of the screening and subsequent treatment. Seven people would have been prevented from having a subarachnoid haemorrhage. Since estimates of the incidence of aneurysms have been as high as 6% in the general population, it is possible that first degree relatives of subarachnoid haemorrhage patients do not have a significantly increased risk over the general population, or if they do, it is only slight. The situation is somewhat different for people who have had at least two first degree relatives who have suffered a subarachnoid haemorrhage. This is a slightly more unusual situation, where haemorrhage from ruptured aneurysms seems to run in families. In a study of patients who had at least two relatives who have had a subarachnoid haemorrhage, 34 of 244 people (13.9%) were found to have aneurysms, compared to an incidence of 6% in a group of normal volunteers. When other risk factors are taken into account, such as high blood pressure, smoking and heart disease, the incidence rose to 32%. Thus, although the case for screening in patients who have had one relative with subarachnoid haemorrhage appears weak, there is a case for offering screening to patients in whom at least two relatives have had a proven subarachnoid haemorrhage from a ruptured aneurysm.

A screening examination is either a magnetic resonance scan, which does not involve any injections, or a cerebral angiogram. The cerebral angiogram does involve an injection of dye and x-rays of the head are taken from the front and from the side. The cerebral angiogram is considered the most accurate method for the detection of aneurysms. However, the magnetic resonance angiogram technology is improving all the time and is good at picking up all but the very smallest aneurysms.

If an aneurysm is detected, then the question arises as to whether treating the aneurysm is better, or worse, than simply observing it. In a recent study of aneurysms which had been found incidentally and were simply observed, the risk of rupture over 7½ years was found to be 0.05% in aneurysms less than 10mm in diameter. In aneurysms greater than 10mm in diameter, the incidence of rupture rose to 1%. The risks of rupture varied, depending on the location of the aneurysm within the brain, and also with the aneurysm diameter. However, the commonest group of aneurysms found did have an exceedingly low risk of rupture. The same study looked at the risks of surgery. The risk of death from surgery for an aneurysm varies from 0% to 7% and the complication rate varies between 4% and 15.3%. In addition, the surgical complication rate rises steeply with age, being 5% in patients less than 45 years and rising to 32% in patients older than 64 years. Although the figures appear, at first, confusing, a clear message does emerge. The younger the age at which an aneurysm is detected means that there is a longer period of risk of rupture over that patient’s lifetime and also a reduced risk of surgical complications. At the other end of the age spectrum, for instance in the 6th and 7th decades, there is a shorter life expectancy and therefore a shorter period of risk, with a much increased surgical complication rate. A balance, therefore, has to be struck, between the benefits of treating an aneurysm and reducing the risk of a subarachnoid haemorrhage versus the risk of the patient being harmed by the surgical procedure itself. At the moment, the general consensus is that there appears to be a cut off point around the age of 45 years, beyond which, there is a reducing benefit from treatment.

To summarise, therefore, the present situation is that where a person has had two members of a family who have had a subarachnoid haemorrhage from a ruptured aneurysm, screening appears to be worthwhile. In cases of first degree relatives, where only one member of the family has had a subarachnoid haemorrhage, the evidence is weaker and each case is dealt with on an individual basis. There are certain groups of patients who are known to be at an increased risk of harboring an intracranial aneurysm, such as patients with adult polycystic kidney disease.

This summary of screening attempts to summarise a complex and controversial issue. Indeed, not all doctors agree that routine screening is indicated, even in the groups outlined above. In an editorial in the British Medical Journal in December 1999, the case was made out for not offering routine screening, except in individual high risk cases. The overriding problem is that we require more long term follow up studies, to determine whether, or not, there is benefit from detecting unruptured aneurysms. In the meantime, patients should seek specialist advice and decisions should be made, taking into account the patient’s family and medical history, as well as other risk factors. There are no plans to introduce mass screening for the general population, who do not have a relative with a subarachnoid haemorrhage. The evidence to date suggests that mass screening is not worthwhile. All patients considering being screened should be carefully counselled by a specialist and the implications of the screening procedure and a possible positive result discussed. If, for instance, the person being screened would not under any circumstances, consider having treatment, then there is little point in going ahead with the screening examination.

If you are a person who has had two family members who have suffered a subarachnoid haemorrhage, you may want to do discuss the possibility of screening with your doctor.

References:

Recommendations for the Management of Patients with Unruptured Intracranial Aneurysms. A statement for health care professionals from the Stroke Council of the American Heart Association. Circulation, 2,000; 102:2300-2308

Risks and Benefits of Screening for Intracranial Aneurysms in First Degree Relatives of Patients with Sporadic Subarachnoid Haemorrhage. The magnetic resonance angiography in relatives of patients with subarachnoid haemorrhage study group. New England Journal of Medicine, October 28, 1999:1344-1350.