Daily Archives: December 3, 2009

Patient HM: An Odd Case of Amnesia

On December 5, 2008 Henry Molaison died. He was known as patient HM to the medical community. His entry into the annals of medical history began in 1953 when he underwent surgery for a seizure disorder. At that time, the evil and greedy pharmaceutical companies, that have since produced dozens medications to control seizures, had few effective anti-seizure medications in their medical bag of tricks. Those would come years and billions of dollars later. Because seizure disorders greatly disturbed most victim’s lives, many unusual and aggressive techniques were used for controlling them, including various surgical procedures.

HM apparently suffered a head injury at the age of nine and it was felt that this might be  the cause of his seizures. He would frequently suffer powerful convulsions and the disorder interfered with his ability to keep a job. For this reason he underwent surgical treatment in which a portion of his hippocampus, a structure deep in the brain, was removed. His seizures improved but a very unusual complication arose. HM developed anterograde amnesia. He was unable to form long-term memories. This condition remained with him until his death at age 82.

Amnesia is an odd dysfunction of the brain. Memories are trapped inside and cannot be accessed, and in some forms of amnesia, new memories cannot be formed and stored. Amnesia has many causes, including trauma, brain infections, severe stress, and a handful of other things. It occurs in several forms but I will only look at two here: Retrograde and Anterograde.

In Retrograde Amnesia the victim is unable to recall events that occurred prior to the onset of the amnesia. It can be complete or partial.  It can cover only the few minutes before the event all the way back to forever and anywhere in between. It can completely resolve, partially resolve, or never resolve.  It can last for minutes, days, weeks, months, years, or forever. When memory returns it can occur instantly, in fits and spurts, gradually, or never. Memories that do return can be complete, spotty, or with huge holes. Almost anything is possible. For example, a victim might remember faces but not names. He might remember events but not people. He might recognize who he is or not. In other words, his memory loss can be for almost anything and in any combination.

Anterograde Amnesia is marked by the inability to form new memories. Everyone you meet, every place you go, everything you see or read, and essentially everything you come into contact with makes sense at the time but no memories are formed so repeating any of these events is as if you were doing them for the first time. Imagine how debilitating this is. You meet your next-door neighbor, and the next day you don’t remember who he is or if you have ever seen him before. You read a book or see a movie but the next day remember nothing about it. You mail in your tax returns and don’t remember whether you did or not. Life can get confusing. HM had to live with this his entire life.

The movie Memento was based on this medical condition. Leonard, the protagonist of the story played by Guy Pearce, had anterograde amnesia. He resorted to making notes, tattooing important information on his body, and tried every trick he could think of to decide what was real, what was imagined, and who he could trust. Great movie. If you haven’t seen it you should.

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