The widow of the late Robin Williams has written an emotional essay for a medical journal, opening up about the Oscar-winner’s final days and shedding some light on the devastating medical issues he was coping with before he tragically took his own life.

In the essay, entitled “The Terrorist Inside My Husband’s Brain” for The Official Journal of the American Academy of Neurology, Susan Schneider Williams writes: “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 continues: “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. He was not alone in his traumatic experience with this neurologic disease.”

Unfortunately, Williams’ LBD was not discovered until the coroner’s report was released following his death, which explained the baffling symptoms Williams was suffering as doctors struggled to figure out what was wrong.

“Once the coroner’s report was reviewed, a doctor was able to point out to me that there was a high concentration of Lewy bodies within the amygdala,” she writes. “This likely caused the acute paranoia and out-of-character emotional responses he was having. How I wish he could have known why he was struggling, that it was not a weakness in his heart, spirit, or character.”

RELATED: Robin Williams’ Daughter, Zelda, Talks Finding A Silver Lining After Her Father’s Death

In fact, she notes that Williams was suffering from an array of symptoms that didn’t fit into any single illness, including “constipation, urinary difficulty, heartburn, sleeplessness and insomnia, and a poor sense of smell — and lots of stress,” she writes of what Williams was going through in 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.”

She adds: “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.”

She also recalls when Williams had a panic attack when he couldn’t remember his lines while filming “Night at the Museum 3”, something that he had never experienced before. “This loss of memory and inability to control his anxiety was devastating to him,” she says.

Williams was diagnosed with Parkinson’s Disease about a month before his death, she notes. “He kept saying, ‘I just want to reboot my brain.’ 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?’ and when his doctor said ‘No,’ Robin was unsatisfied.”

RELATED: Matt Damon Remembers Robin Williams In Touching Tribute On Anniversary Of His Death

She admits that during his final month alive she could see he “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. 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.”

Looking back, she recalls one final day when she felt hopeful that Williams might be improving. “We did all the things we love on Saturday day and into the evening, it was perfect — like one long date,” she writes. “By the end of Sunday, I was feeling that he was getting better. 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 concludes the essay with a message of encouragement for doctors studying LDB. “I know you have accomplished much already in the areas of research and discovery toward cures in brain disease,” she writes. “And I am sure at times the progress has felt painfully slow. Do not give up. … If only Robin could have met you. He would have loved you — not just because he was a genius and enjoyed science and discovery, but because he would have found a lot of material within your work to use in entertaining his audiences, including the troops. In fact, the most repeat character role he played throughout his career was a doctor, albeit different forms of practice.”

She concludes: “Thank you for what you have done, and for what you are about to do.”