Robin took his life in 2014, leaving his millions of fans, family, and friends shocked and grieving. He was 63.
For the last year, Susan has remained mostly silent about her husband's tragic passing in an effort to uncover and study the real cause of his death.
Opening up about his suicide, Susan shared the details of Diffuse Lewy Body Dementia or Dementia with Lewy bodies (DLB) that took hold of Williams and the couple's harrowing ordeal to fight it.
Frequently misdiagnosed, DLB is the second most common neurodegenerative dementia after Alzheimer's and causes fluctuations in mental status, hallucinations and impairment of motor function.
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The disease started taking its toll on Williams in the last year before his death, by way of its "whack-a-mole"-like symptoms which included heightened levels of anxiety, delusions and impaired movement.
"They present themselves like a pinball machine. You don't know exactly what you're looking at," she said.
Robin's symptoms worsened in the months leading up to his death.
"I know now the doctors, the whole team was doing exactly the right things. It's just that this disease was faster than us and bigger than us. We would have gotten there eventually."
Susan hopes that she can use what she's learned to help others afflicted by DLB.
"I've spent this last year trying to find out what killed Robin. To understand what we were fighting, what we were in the trenches fighting and one of the doctors said, 'Robin was very aware that he was losing his mind and there was nothing he could do about it'," she said.