A brain aneurysm shows up in a weak artery wall, the cause of this occurrence is still unknown. Although, it could be degeneration, increasing age, and high blood pressure.More commonly linked to atherosclerosis, a blood vessel disease that causes arteries to harden through the gradual build-up of fatty deposits on the inside of the arterial walls. People with specific genetic disorders including connective tissue disorder and polycystic kidney disease are more prone to developing brain aneurysms. Other causing factors for example includes some of the circulation diseases such as arteriovenous malformation, also alcohol and drug abuse, head trauma, infections, and tumours.