Aneurysm is a dilation of a cerebral artery. The dimensions can vary from a few millimeters to lesions called “giants”, with diameters greater than 2.5 cm. The aneurysm can affect any cerebral artery even if with a different frequency and sometimes symptoms.
The classification of aneurysms
Aneurysms as well as for size and location can be divided into two large families:
- Broken aneurysms: those that determine the picture of subarachnoid hemorrhage.
- Unruptured aneurysms: lesions often occasionally encountered during other investigations.
About 4-5% of the population has aneurysms, but only a minimal amount of these will give a sign of themselves. The aneurysm is frequently localized in the bifurcation of the cerebral vessels, a sign that the cause is often embryological. Once formed, its natural history is variable. Important co-factors are: arterial hypertension, smoking, multiple aneurysms and connective tissue diseases.
In most cases the aneurysm remains silent throughout life. Rarely does it gradually increase in size until it gives symptoms of “mass effect” (headache, compression of cranial nerves with ocular motility disorders, epileptic seizures etc).
A minimal percentage goes to break. The dimensions of the bag are directly related to the risk of breakage. An aneurysm less than 6-7 mm has a low bleeding risk / year; if, on the other hand, it is greater than 7 mm, it is generally to be treated.
There is therefore a territory of “penumbra” around 5-7 mm, in which a careful evaluation by the neuro vascular team is necessary, which must assess the risk based on the patient’s age, the form of the aneurysm, the presence of multiple aneurysms and patient tolerance to the idea of having an unbroken aneurysm, an aspect not to be underestimated.