After the decision is made to treat an intracranial aneurysm, clinicians must choose between two competing treatment options; open surgery or endovascular therapy. The rationale underlying the choice of treatment modality is usually unclear, as there is little good quality evidence available.

We discuss the patient and aneurysm-related factors cited in the neurovascular literature that are considered to influence aneurysm treatment choices.

The relevance and direction of influence of rupture status, age, type of presentation, and general medical condition, as well as aneurysm size, location, morphology, and multiplicity are discussed. The validity of these factors in influencing treatment decisions remains unclear, with frequently opposing views on the same factor by clinicians practicing opposing techniques. Perceived differences in efficacy and safety of the two different treatment approaches are commonly used in an attempt to justify treatment choices. Difficulties with treatment selection and case-by-case reasoning are reviewed.

Properly designed and conducted randomized trials are necessary in order to settle the controversy and to determine the optimal treatment modality for intracranial aneurysms. In the absence of reliable knowledge on which to base treatment decisions, the ethically appropriate choice for any clinician, from surgical or endovascular backgrounds, is to participate in randomized trials.