TIBURON (KPIX 5) — A powerful essay from Robin William’s widow sheds light on the painful neurological disorder that made the beloved actor take his own life.

When Williams died at his Tiburon home in 2014, a simplistic rather narrative emerged about his lifelong battle with depression. With the emergence of Susan Schneider’s heartbreaking essay, we now know it was much more complicated than that.

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She titled the letter, “The Terrorist Inside My Husband’s Brain,” and published it in the medical journal, Neurology.

The genius movie star and comedian’s widow pens a poignant essay addressed to the scientists who are working on a cure for the disease that killed her husband.

Schneider writes that Williams was misdiagnosed at first. Doctors believed he had Parkinson’s Disease, and that’s what he thought he had when he committed suicide two months later.

But subsequent autopsies revealed another disease had ravaged Robin’s mind. It’s called Lewy Body Dementia, or LBD, which has a strange variety of symptoms. It sent him into bouts of anxiety and paranoia.

“He would thrash at night and had terrible insomnia,” she wrote. “At times, he would find himself stuck in a frozen stance, unable to move and frustrated when he came out of it.”

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“They didn’t have the answers to what was going on until after he died and that’s an all too common story,” says Doctor Kate Possin, a UCSF professor of Neurology.

Possin has spoken to Schneider, and the fact that he didn’t know quite what was ailing him was a major contributor to his death.

“As we’ve learned from that really beautiful letter from Susan, they were suffering with a lot of symptoms they didn’t have the answers to, struggling with unknown reasons for feelings of extreme anxiety as well as other symptoms like gastrointestinal symptoms or spacial dysfunctions — other memory problems that they didn’t understand.” says Possin.

“This took over their lives. And I understand from Susan that this is why he decided to take his life.”

Would a proper diagnosis have made a difference? Schneider has mixed feelings. On the one hand, LBD has no cure so it would have been a very cruel way for Robin Williams to die. On the other hand, it might have given them peace to know just what was breaking down his mind.

Schneider says she shared their personal story in hopes it would help doctors understand patients grappling with LBD, their spouses, and their caregivers.

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“Perhaps this will add a few more faces behind the why you do what you do. I am sure there are already so many… Not only did I lose my husband to LBD, I lost my best friend.”