Incidentally discovered aneurysm in the brain. Now what do I do?

One of the readers of my blog wrote in to me. Her question and my response to it follows.

Hello Doctor,

I am a 27 year old otherwise healthy female. I work as a nurse and I recently got an MRI MRA due to some mild dizziness I was experiencing at work. I was shocked to learn that I have a 3mm aneurysm arising from the anterior aspect of the supracliniod portion of the left internal carotid artery consistent with ophthalmic artery aneurysm. I would greatly appreciate any advice/opinions you could provide….thanks so much.

Dear E,

                              Thank you for writing in to me.  Aneurysms in the brain are at times (actually quite frequently) discovered incidentally. The usual setting is that the patient seeks medical attention for some non-specific complaints commonly headache or like in your case dizziness. The doctor orders a MRI of the brain and the “silent” aneurysm comes to medical attention for the first time.

The majority of small sized aneurysms are clinically silent. By that I mean they cause no pain , headache, weakness in the arms or legs.  A small sized aneurysm may remain clinically silent and only come to medical attention when it ruptures and causes bleeding into the brain. Aneurysmal bleed usually causes subarachnoid hemorrhage (SAH). The SAH may be massive and carries a high morbidity and mortality rate. Survivors are usually left behind with significant neurological deficits (disabilities).

It is usually a giant aneurysm (defined as one greater than 2.5 cm in diameter)  that causes mass effect and hence may present clinically with weakness if it presses on the motor tracts in the brain or with problems with vision (decrease in visual acuity or double vision) if it press on the optic or other nerves with control the movements of the eye.

Now what to do when an aneurysm is discovered incidentally as in your case? Though I have not examined you, it is more than likely that the aneurysm is not the cause of your mild dizziness. The risk of an aneurysm to rupture has been studied  and the results are mixed. Since any aneurysm no matter what the size has the potential to rupture, every patient needs to be assessed on an individual basis for this.  Studies have shown that small aneurysms can be “safety” watched. The usual cut-off size is about 7 mm, though there is a debate whether aneurysms smaller than 7 mm in size carry a lower risk for rupture. It is well accepted that aneurysms greater than 25mm in size should be considered for therapy (there are different ways aneurysms can be treated—surgical treatment Vs endovascular treatment Vs a combination of the two) after closely weighing the potential risks of the surgery against the benefits (how likely is the aneurysm to rupture in the near future).

So my advise to you is to follow up with your physician.  After reviewing your MRI brain and other studies such as MRA (magnetic resonance angiography), he shall determine the best approach going forward. If he decides to wait and watch, then likely you shall need serial MRI studies at some interval of time (every 3 months Vs every 6 months Vs every year). Again there is no hard and fixed rule about how frequently you shall need to be scanned, this too shall be determined by your physician.

If you have high blood pressure, it shall be wise to maintain good blood pressure control.

I hope I have been able to shed some light on your query. Please feel free to write in again.

Personal Regards,

Nitin Sethi, MD

Incidental cerebral aneursym on brain imaging: what to do?

At times an incidental cerebral aneurysm is found when neuroimaging is carried out. Let me explain this with an example. You go to your doctor as you have been having headaches or suppose you have a history of migraine, your doctor orders a MRI brain. A  cerebral aneurysm is found on brain imaging.

What to do now is the question?

Does the aneurysm warrant treatment?

If yes what treatment?

To answer the above questions it is essential to first understand the natural history of cerebral aneurysm. An aneurysm is a dilatation of a blood vessel. These dilatations may be congenital (meaning you are born with it) or they may develop later in life due to trauma or turbulent blood flow. Cerebral aneurysms can rupture. When they do rupture they cause bleeding into the brain. This bleeding occurs into the subarachnoid space and hence it is called subarachnoid hemorrhage (SAH). SAH has a high morbidity and mortality and hence it is essential that if an incidental aneurysm is found we should know what to do about it.

Well first the question is whether the aneursym is indeed the cause of the symptom for which the imaging was done in the first place. As I stated earlier, the aneurysm may be entirely unrelated to the headache and may just be an incidental finding.

If the aneursym is incidental then the question is what needs to be done about it. What is the risk that it would rupture and cause hemorrhage? How soon should it be taken care of? Fortunately we now have some answers to the above questions. Studies have shown that the risk of rupture is directly related to the size of the aneurysm. Aneurysms which are small in size, less than 7 mm have a lower risk of rupture as compared to those above 10 mm in size. Hence a small aneurysm may be watched. Your doctor may opt to do nothing apart from recommending that the MRI scan be repeated after 6 months to 1 year. If there is interval increase in size of the aneurysm, then definitive treatment options can be pursued.

For aneuryms which are larger than 10 mm, it is important that they be treated on an urgent basis as the risk of rupture is high. There are different modalities to treat the aneurysm. One may either opt for endovascular coiling (here the skull is not opened, instead the aneurysm is approached via the endovascular route and then thrombogenic coils are placed into the aneurysm. The idea is to thrombose the aneurysm over time and hence to obliterate it). The other more invasive approach is to do a formal surgery, the skull is opened up, the aneurysm is located by the neurosurgeon and then a clip or band is placed across its neck to obliterate it.

Which option should be employed depends upon the aneurysm characteristics. Aneurysms which have a broad neck are difficult to coil, those which are in surgically inaccessible locations are more easy to coil endovascularly.

Hope this helps some of my readers. It is a beautiful Sunday afternoon here in New York City. Time to go for a run.

Personal Regards,

Nitin Sethi, MD