Robin Williams’ wife, Susan Schneider Williams, wrote a heartfelt letter to scientists whose research focuses on neurological disorders, revealing that her late husband hid one heartbreaking symptom from her.

Williams, known for his roles in Dead Poets Society, Mrs. Doubtfire and Good Will Hunting, had been dealing with mental health struggles before he committed suicide in 2014 at 63.

Before his death, Williams was misdiagnosed with Parkinson’s disease in 2013 after experiencing “a firestorm of symptoms” like “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,” she wrote.

Williams also started displaying shifts in mental health followed by delusions, paranoia and anxiety. It wasn’t until May of that year the family learned he was misdiagnosed.

“Not until the coroner’s report, three months after his death, would I learn that it was diffuse LBD [Lewy body dementia] that took him,” Schneider Williams said. “All four of the doctors I met with afterwards and who had reviewed his records indicated his was one of the worst pathologies they had seen.”

Lewy body dementia is “associated with abnormal deposits of a protein called alpha-synuclein in the brain. These deposits, called Lewy bodies, affect chemicals in the brain whose changes, in turn, can lead to problems with thinking, movement, behavior, and mood,” according to National Institute on Aging.

“Throughout the course of Robin’s battle, he had experienced nearly all of the 40-plus symptoms of LBD, except for one. He never said he had hallucinations,” she wrote. “A year after he left, in speaking with one of the doctors who reviewed his records, it became evident that most likely he did have hallucinations, but was keeping that to himself.”

Williams’ widow doesn’t think her late husband’s life could’ve been saved by a diagnosis. “There is no cure and Robin’s steep and rapid decline was assured. It felt like he was drowning in his symptoms, and I was drowning along with him.”

Schneider Williams now sits on the Board of Directors for the American Brain Foundation, working to raise awareness about Lewy Body Dementia.

She ends her letter by telling researchers to continue to study the disease that took her husband. “I am sure at times the progress has felt painfully slow. Do not give up. Trust that a cascade of cures and discovery is imminent in all areas of brain disease and you will be a part of making that happen,” Schneider Williams wrote. “If only Robin could have met you. He would have loved you.”

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