I just read this recently, but of course can't remember author, title or where I found it. Dean becomes blind and deaf, and it takes a while for Sam to find him in a hospital. The scene that really stood out is when Dean's strapped to the hospital bed and Agent Henricksen taunts him with how he is torturing Sam, trying to prove that Dean is faking (he isn't). Sam eventually rescues him, of course. They become somewhat psychic with each other, and then Wincest-y. I think Dean regains his sight at the end. It is not Dark Side of the Moon by Fleshflutter or Heart Language by janissa11.