If medical expenses aren't claimed in year of death, can they be claimed in the following year? If yes, how many months of expenses can be claimed for deceased person?

My father passed away in 2017.  No medical expenses were claimed in 2017, as taxes payable was already $0.  Can my mother claim medical expenses incurred for my father up until his date of death?  Can she claim expenses for him for 12 or 24 months?