Hi, Thank you for asking to HCM, In subjects with dementia undergoing a surgery on most cases deteriorates the condition. The main reason is blood hypoperfusion during any kind of surgery. Then having in consideration your father past medical history of cerebral aneurysm this is another negative factor. I would advice you to have an appointment with your doctor to thoroughly discuss the possibility of other options for treatment or other ways how to evitate this problem. Hope this will help with the solution of your problem, feel free for any other information.