Multiple aneurysms refers to the presence of more than one brain aneurysm in a single patient at the same time. Approximately one-fifth of patients diagnosed with a brain aneurysm are found to have more than one aneurysm; in other words, this is not a rare condition, and it considerably complicates the evaluation process.

Multiple aneurysms are seen more frequently in certain patient groups. Their incidence increases in women, in smokers, in those with hypertension, and in those with a family history of aneurysm. In addition, certain genetic conditions such as polycystic kidney disease and some connective tissue diseases predispose to the development of more than one aneurysm. Aneurysms may sometimes be located on the same vessel, and sometimes symmetrically on both sides (mirror aneurysms).

The most fundamental clinical challenge posed by multiple aneurysms is determining which aneurysm has ruptured in the event of bleeding. When more than one aneurysm is seen in a patient presenting with subarachnoid hemorrhage, the surgeon must identify the one responsible for the bleeding in order to guide treatment. In this distinction, the bleeding pattern (the distribution of blood on CT), morphological features such as the size, shape, and irregularity of the aneurysms, and the location are evaluated together. Generally, the largest, most irregular, or the one closest to the bleeding area is considered responsible.

Multiple aneurysms also require special planning in the treatment approach. The ruptured aneurysm is treated as a priority; the other unruptured aneurysms are evaluated according to their size, location, and the patient’s general condition, either in the same session, at a later stage, or through follow-up. In some cases, different methods may be used together for different aneurysms (surgical clipping for some, endovascular treatment for others).

In summary, the presence of multiple aneurysms makes both the diagnostic evaluation and the treatment strategy more meticulous and individualized. In these patients, comprehensive vascular imaging and a careful follow-up plan are among the most important factors determining the outcome.