Two years after his death, Robin Williams' widow is still fighting for answers.
Since the actor's suicide on Aug. 11, 2014, his wife, Susan Scheider Williams, has been working to understand and spread awareness of the brain disease Williams didn't know he had -- Lewy Body Disease (LBD) -- recently writing an essay on her husband's struggles for the medical journal Neurology.
WATCH: Robin Williams' Wife Breaks Silence About Actor's Suicide: 'We Did Everything We Could'
In her piece, titled "The Terrorist Inside My Husband's Brain," Susan describes her husband's final months, which she says were filled with paranoia, anxiety, stress and depression.
"This is a personal story, sadly tragic and heartbreaking, but by sharing this information with you I know that you can help make a difference in the lives of others," she writes, addressing the journal's readers of neurologists, doctors and scientists. "As you may know, my husband Robin Williams had the little-known but deadly Lewy body disease (LBD). He died from suicide in 2014 at the end of an intense, confusing, and relatively swift persecution at the hand of this disease's symptoms and pathology."
Susan then details Williams' final months, which were filled by a variety of symptoms that didn't seem to fit with any one disease. "Constipation, urinary difficulty, heartburn, sleeplessness and insomnia, and a poor sense of smell -- and lots of stress," she says of his symptoms in the fall of 2013. "By wintertime, problems with paranoia, delusions and looping, insomnia, memory, and high cortisol levels -- just to name a few -- were settling in hard. Psychotherapy and other medical help was becoming a constant in trying to manage and solve these seemingly disparate conditions."
WATCH: Zelda Williams Talks Coping With Dad Robin Williams’ Death: ‘I Wrote 12 Scripts, Didn’t See Daylight for a While’
The next spring, while filming Night at the Museum 3, she says Williams suffered from a panic attack, and had trouble remembering "even one line for his scenes" -- something that had never happened in his career. "This loss of memory and inability to control his anxiety was devastating to him," she adds.
Williams was diagnosed with Parkinson's Disease that May, and while she says that her "heart swelled with hope," she "knew Robin was not buying it."
"When we were in the neurologist's office learning exactly what this meant, Robin had a chance to ask some burning questions. He asked, 'Do I have Alzheimer's? Dementia? Am I schizophrenic?' The answers were the best we could have gotten: No, no, and no. There were no indications of these other diseases," she recalls. "It is apparent to me now that he was most likely keeping the depth of his symptoms to himself."
WATCH: EXCLUSIVE: Zelda Williams Isn't Ready to Watch Dad Robin's Movies Yet: It Would Be Self-Destructive
The couple continued to work through Williams' wide variety of symptoms, going through neurocognitive testing, physical therapy, therapy, mediation, and even self-hypnosis to try to manage his disease.
During his final month, however, Susan says she could tell her husband "was growing weary."
"The parkinsonian mask was ever present and his voice was weakened. His left hand tremor was continuous now and he had a slow, shuffling gait. He hated that he could not find the words he wanted in conversations. He would thrash at night and still had terrible insomnia," she writes. "At times, he would find himself stuck in a frozen stance, unable to move, and frustrated when he came out of it. He was beginning to have trouble with visual and spatial abilities in the way of judging distance and depth. His loss of basic reasoning just added to his growing confusion."
She then recounts a final perfect day with the actor in which she thought he might be getting better.
RELATED: Sarah Michelle Gellar Remembers Robin Williams on Anniversary of His Death: 'With All the Angels'
"We did all the things we love on Saturday day and into the evening, it was perfect -- like one long date. By the end of Sunday, I was feeling that he was getting better," she writes. "When we retired for sleep, in our customary way, my husband said to me, 'Goodnight, my love,' and waited for my familiar reply: 'Goodnight, my love.'"
"His words still echo through my heart today," she continues. "Monday, August 11, Robin was gone."
She concludes her essay with a call to action to the doctors and scientists she addressed in the beginning of her piece, thanking them "for what you have done, and what you are about to do."
"Hopefully from this sharing of our experience you will be inspired to turn Robin's suffering into something meaningful through your work and wisdom," she shares. "It is my belief that when healing comes out of Robin's experience, he will not have battled and died in vain."
WATCH: Robin Williams' Widow Opens Up in First TV Interview Since the Comedian's Death