Robin Williams’ widow Susan Schneider Williams in an essay shared details on her husband’s anxiety- and confusion-riddled last few months. The essay published Thursday in the journal Neurology is the latest step in Schneider Williams’ efforts to bring awareness to Lewy Body Disease (LBD) which led to the comedian’s death in 2014.

In her essay, Schneider Williams revealed that doctors figured the true cause of Williams’ death only after it occurred though the symptoms had been plaguing him for years. Nearly 1.5 million people in the U.S. are suffering from LBD and according to multiple doctors Schneider Williams met, the comedian was “one of the worst pathologies they had seen.”

“He had about 40% loss of dopamine neurons and almost no neurons were free of Lewy bodies throughout the entire brain and brainstem,” she wrote in the essay titled ‘The terrorist inside my husband's brain.’

“Robin was losing his mind and he was aware of it. Can you imagine the pain he felt as he experienced himself disintegrating? And not from something he would ever know the name of, or understand? Neither he, nor anyone could stop it—no amount of intelligence or love could hold it back,” Schneider Williams wrote.

In his final months, Williams’ symptoms took a toll on him, his widow revealed. He had trouble remembering single lines during the filming of “Night at the Museum 3.” He experienced tremors, anxiety, paranoia and significant memory loss.

Doctors found later that in addition to LBD, the actor was also showing signs of experiencing the early stages of Parkinson’s disease.

“Powerless and frozen, I stood in the darkness of not knowing what was happening to my husband. Was it a single source, a single terrorist, or was this a combo pack of disease raining down on him? He kept saying, ‘I just want to reboot my brain,’” Williams’ widow penned.

Williams died of suicide in August 2014 having experienced nearly all of the symptoms of LBD before his death.

Robin williams Actor Robin Williams appears onstage during MTV's Total Request Live at the MTV Times Square Studios in New York City, April 27, 2006. Photo: PETER KRAMER/GETTY IMAGES