Employers are required to comply with the Americans with Disabilities Act (ADA) and other legislation designed to protect people with disabilities. This includes providing reasonable job accommodations to people with disabilities. Reasonable accommodations can include an adjusted job schedule. There are many other accommodations that can be provided, depending on the nature and severity of the disability.
So the advantage of informing your employer is that you would be able to take advantage of the ADA provisions.
The disadvantage is that if you have an unscrupulous employer, they could hold your condition against you and you would have to fight for your rights.
Here's some information:https://www.dol.gov/general/topic/disability
(also check the subtopic links on the right)http://askjan.org/