Size & location. It depends on the location, the size, the rate of growth & whether it has leaked or ruptured. Throbbing headaches which stay in one location are common but must be distinguished from migraine. New onset seizure, partial loss of vision or symptoms of stroke are other typical presentations but none are specific. Ct or MRI can rule in/out an aneurysm reliably.
Depends. There are a variety of types of aneurysms. Generally they are a weakened or abnormal portion of a brain blood vessel. Usually an artery which carries high pressure blood is involved. If an aneurysm is suspected, a thorough neurosurgical evaluation is warranted.