What Is Lewy Body Dementia? Info on the Disease Robin Williams' Wife Said Killed Him

More than a year after actor Robin Williams died by suicide in what was widely believed to be a result of depression, his wife Susie Williams opened up to Good Morning America's Amy Robach in an exclusive interview on Tuesday about what she said really caused her husband's death — a neurocognitive disease called Lewy body dementia.

"Lewy body dementia killed Robin, it's what took his life," she said during the interview, adding that experts diagnosed Robin with the disease after his autopsy. 

"You can see very dramatic effects in thinking, emotion and behavior," Dr. Dan Kaufer, director of the University of North Carolina's Memory Disorders Program, said in an interview during the Good Morning America special. 

The disease that killed Robin: Lewy body dementia is a form of dementia that kills outer and mid-layer brain cells and distorts surviving cells in structures called "Lewy bodies," according to the Centers for Disease Control and Prevention. Like other forms of dementia, Lewy body dementia is a neurocognitive illness that progressively impairs memory, language ability, motor skills and object recognition, according to the CDC.

There is no way to detect Lewy bodies disease aside from an autopsy, according to the Alzheimer's Association, meaning any diagnosis on a living person is limited to a doctor's educated opinion.

Experts estimate that Lewy body dementia is the third-most common form of dementia, according to the Alzheimer's Association. The disease is named for Frederick H. Lewy, the neurologist who recognized the disease in the early 1900s. The main protein found in Lewy body cells is actually found in abundance in the brain, but its purpose remains unknown.

Lewy body and Parkinson's: The Alzheimer's Association also notes studies have linked Lewy body dementia to Parkinson's disease, early signs of which Robin Williams began to display in May 2013, Susie Williams told Robach. The combination of these two diseases could have caused cognitive implications that led the actor to suicide. "Many people with both [Lewy body dementia] and Parkinson's dementia also have plaques and tangles — hallmark brain changes linked to Alzheimer's disease," the Alzheimer's Association writes of the two conditions.

Symptoms: Symptoms of Lewy body dementia include impaired "thinking and reasoning," back-and-forth "confusion and alertness," hallucinations and rapid-eye movement sleep disorder, according to the Alzheimer's Association. Susie told Robach that she and Robin slept apart due to his sleeping troubles.

Treatment: A cure for the disease has yet to be found — current treatments only slow down the degeneration process or ease symptoms, according to the Alzheimer's Association. These include antidepressants and antipsychotic drugs.

Robin Williams was supposed to check into a center for neurocognitive testing the week he took his life, according the the exclusive interview, but his wife said she doesn't blame him for not pursuing treatment, as doctors told him he only had an estimated three years to live.