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'The Terrorist Inside My Husband's Brain': Robin Williams' Widow Details His Disease
Robin Williams and Susan Schneider Williams at the premiere of the movie "Old Dogs" on November 9, 2009 in Hollywood, California.
Credit: Jason Merritt / Getty Images

It was only after actor Robin Williams' death in August 2014 that doctors found the true cause of the symptoms that had plagued him for years, according to Williams' widow, Susan Schneider Williams.

Writing in an editorial published Sept. 27 in the journal Neurology, Schneider Williams detailed the intense difficulty of determining the cause of her husband's symptoms.

After his death, doctors finally determined that Williams had a condition called Lewy body disease, which Schneider Williams described as a "terrorist within his brain." [Top 10 Stigmatized Health Disorders]

Lewy body disease is one of the most common forms of dementia, according to the National Institutes of Health. It occurs when Lewy bodies, or clumps of protein called alpha-synuclein, build up in the brain.

The doctors who examined Williams' brain after his death said that his case was "one of the worst pathologies" they had ever seen, Schneider Williams wrote. "He had about 40 percent loss of dopamine neurons, and almost no neurons were free of Lewy bodies throughout the entire brain and brainstem," she wrote.

But Robin Williams was not diagnosed with Lewy body disease while he was alive. Rather, he received a diagnosis of Parkinson's disease on May 28, 2014, Schneider Williams wrote. Both Lewy body disease and Parkinson's disease involve the presence of Lewy bodies in the brain, according to the editorial.

Robin Williams' clinical symptoms were those of Parkinson's, and his brain pathology showed he had Lewy body dementia, Schneider Williams wrote. Whether a person is diagnosed with Lewy body disease or Parkinson's disease can depend on which symptoms occur first, she wrote.

Indeed, symptoms of Lewy body disease can resemble those of Parkinson's disease, according to the Lewy Body Dementia Association.

Before Williams was diagnosed with Parkinson's disease, he had experienced a wide array of symptoms that seemed unrelated, according to the editorial. [3 Myths About Parkinson's Disease]

By October 2013, Schneider Williams said the actor had been experiencing constipation, urinary difficulty, heartburn, sleeplessness, insomnia, a poor sense of smell and stress. In addition, he had "a slight tremor in his left hand that would come and go," but at the time, that was attributed to a previous shoulder injury, she wrote.

At the end of that October, Williams developed gut pain, and his reaction was "markedly out of character," Schneider Williams wrote. "His fear and anxiety skyrocketed to a point that was alarming," she wrote.

Over the next few months, Williams' symptoms got worse. He had increasing problems with paranoia, delusions, insomnia and memory, as well as high cortisol levels, Schneider Williams wrote. He tried psychotherapy and various medications, she wrote. Later, she learned that a high concentration of Lewy bodies in the part of his brain called the amygdala likely caused the "acute paranoia and out-of-character emotional responses he was having," she wrote.

His neurological symptoms worsened through the spring, and his "loss of memory and inability to control his anxiety was devastating to him," Schneider Williams wrote.

He later developed more physical symptoms typical of Parkinson's disease, including a continuous tremor in his hand and a slow, shuffling gait, according to the editorial. He had terrible insomnia and began having trouble judging distance and depth, Schneider Williams wrote.

In addition, his symptoms could come and go quickly, she wrote. Williams would be "lucid with clear reasoning one minute and then, five minutes later, blank, lost in confusion," she wrote. This fluctuation in symptoms is common in people with Lewy body disease, she added.

Overall, Williams "experienced nearly all of the 40-plus symptoms of [Lewy body disease]," Schneider Williams wrote. Though he never said he had hallucinations, a doctor later told Schneider Williams that he likely did have them but didn't tell anyone.

Originally published on Live Science.