The Sad Story Of Robin Williams' Lewy Body Disease
Williams' wife, Susan Schneider Williams, writes at neurology.org about, as she puts it, "the terrorist inside my husband's brain":

The colors were changing and the air was crisp; it was already late October of 2013 and our second wedding anniversary. Robin had been under his doctors' care. He had been struggling with symptoms that seemed unrelated: constipation, urinary difficulty, heartburn, sleeplessness and insomnia, and a poor sense of smell--and lots of stress. He also had a slight tremor in his left hand that would come and go. For the time being, that was attributed to a previous shoulder injury.

On this particular weekend, he started having gut discomfort. Having been by my husband's side for many years already, I knew his normal reactions when it came to fear and anxiety. What would follow was markedly out of character for him. His fear and anxiety skyrocketed to a point that was alarming. I wondered privately, Is my husband a hypochondriac? Not until after Robin left us would I discover that a sudden and prolonged spike in fear and anxiety can be an early indication of LBD.

He was tested for diverticulitis and the results were negative. Like the rest of the symptoms that followed, they seemed to come and go at random times. Some symptoms were more prevalent than others, but these increased in frequency and severity over the next 10 months.

By wintertime, problems with paranoia, delusions and looping, insomnia, memory, and high cortisol levels--just to name a few--were settling in hard. Psychotherapy and other medical help was becoming a constant in trying to manage and solve these seemingly disparate conditions.

I was getting accustomed to the two of us spending more time in reviewing our days. The subjects though were starting to fall predominantly in the category of fear and anxiety. These concerns that used to have a normal range of tenor were beginning to lodge at a high frequency for him. Once the coroner's report was reviewed, a doctor was able to point out to me that there was a high concentration of Lewy bodies within the amygdala. This likely caused the acute paranoia and out-of-character emotional responses he was having. How I wish he could have known why he was struggling, that it was not a weakness in his heart, spirit, or character.

In early April, Robin had a panic attack. He was in Vancouver, filming Night at the Museum 3. His doctor recommended an antipsychotic medication to help with the anxiety. It seemed to make things better in some ways, but far worse in others. Quickly we searched for something else. Not until after he left us would I discover that antipsychotic medications often make things worse for people with LBD. Also, Robin had a high sensitivity to medications and sometimes his reactions were unpredictable. This is apparently a common theme in people with LBD.

During the filming of the movie, Robin was having trouble remembering even one line for his scenes, while just 3 years prior he had played in a full 5-month season of the Broadway production Bengal Tiger at the Baghdad Zoo, often doing two shows a day with hundreds of lines--and not one mistake. This loss of memory and inability to control his anxiety was devastating to him.

While I was on a photo shoot at Phoenix Lake, capturing scenes to paint, he called several times. He was very concerned with insecurities he was having about himself and interactions with others. We went over every detail. The fears were unfounded and I could not convince him otherwise. I was powerless in helping him see his own brilliance.

For the first time, my own reasoning had no effect in helping my husband find the light through the tunnels of his fear. I felt his disbelief in the truths I was saying. My heart and my hope were shattered temporarily. We had reached a place we had never been before. My husband was trapped in the twisted architecture of his neurons and no matter what I did I could not pull him out.

More on Lewy Body Disease here:

In the early 1900s, while researching Parkinson's disease, the scientist Friederich H. Lewy discovered abnormal protein deposits that disrupt the brain's normal functioning. These Lewy body proteins are found in an area of the brain stem where they deplete the neurotransmitter dopamine, causing Parkinsonian symptoms. In Lewy body dementia, these abnormal proteins are diffuse throughout other areas of the brain, including the cerebral cortex. The brain chemical acetylcholine is depleted, causing disruption of perception, thinking and behavior. Lewy body dementia exists either in pure form, or in conjunction with other brain changes, including those typically seen in Alzheimer's disease and Parkinson's disease.