Personality

One of the most fascinating aspects of neurology for me is the idea that parts of our identity can be altered by illness. It's easy to imagine that diseases can change our memory or our sensory perception or our balance. But I've always been so curious of the idea that illness can affect parts of ourselves that seem so intrinsic and fixed. When I first read Oliver Sacks' The Man Who Mistook His Wife for a Hat, I was most drawn to the stories where personality changes with illness. There are bizarre diseases that can make patients hyper-religious. In my psychology course, I loved hearing about Phineas Gage who had an iron rod pierce his brain's left frontal lobe in a railroad construction accident.

He survived the accident, but his personality changed dramatically. How can an injury change who we are?

That last time I was in the intensive care unit, I saw terribly sad example of this. A young woman presents with several weeks of subacute altered mental status. Her sense of smell and taste change. She becomes less interactive, more withdrawn. Eventually, she has a seizure at home and is brought into the emergency department. She is intubated for recurrent seizures, and her head imaging shows enhancement of the temporal lobes. A tentative diagnosis of HSV encephalitis is made, and she is started on acyclovir. However, during this hospitalization, she starts exhibiting extreme behaviors including suicidal behaviors that her family says she's never had. What a terrible and strange disease that can make someone suicidal. I wonder how this happens on the level of the neurons and neural networks.

Image is in the public domain; from Wikipedia.