Henry Molaison was a one-of-a-kind brain patient. He was literally the only person to have ever undergone a radical procedure that removed the medial temporal lobe to treat debilitating seizures. When his physician found what had become of his patient's memory, the doctor refused to carry out the procedure on anyone else and successfully lobbied against its use by other physicians.
What happened? The removal of Molaison's medial temporal lobes, located above the ears, left him with the rare disorder of complete anterograde amnesia. As a result of this condition, Molaison was completely unable to form any new memories. Molaison could retain old memories and remember the ones he'd formed throughout his life up until the surgery that took place in his 20s. He was also capable of forming procedural memories, or habits. However, he couldn't form new declarative memories, or remember who his friends were, what he'd had for lunch or who was president. He lived this way for 55 years, dying in 2008 at age 82 [source: Carey].
Because of his unique condition, Molaison served as the subject of a number of studies, becoming widely known in the neurological community as patient "H.M."