It was recently revealed that late actor Robin Williams had Lewy body dementia, which his widow believes was responsible for his death.
"Lewy body dementia is what killed Robin," Susan told ABC News. "It's what took his life and that's what I spent the last year trying to get to the bottom of, what took my husband's life."
Susan explained that it was during Williams' autopsy that a coroner found signs of Lewy body dementia (LBD), and doctors who analyzed the autopsy report told her it was one of the most severe cases they had ever seen.
But why was his condition not spotted earlier? After all, LBD is the second most common form of progressive dementia, affecting around 1.3 million Americans, mostly those aged 65 and older.
Despite its prevalence, however, the disease is also the most misdiagnosed form of dementia.
According to the Lewy Body Dementia Association (LBDA), its takes an average of three doctors and more than 18 months to correctly diagnose LBD. Most doctors fail to recognize the signs of LBD; the symptoms are very similar to Alzheimer's disease and other neurodegenerative disorders, such as Parkinson's disease.
In this Spotlight, we take a look at what LBD is, the signs and symptoms of the disease, the treatment options, why the condition is so frequently misdiagnosed, and what is being done to raise awareness of this potentially devastating condition.
What is LBD?
LBD was first discovered in the early 1900s by German-born neurologist Dr. Freiderich H. Lewy. While studying Parkinson's disease, Dr. Lewy identified tiny deposits of a protein called alpha-synuclein in brain cells, which were later named Lewy bodies.
Lewy bodies are found in both Parkinson's and LBD, but for each condition, they are located in different regions of the brain. In Parkinson's, Lewy bodies are primarily found in the substantia nigra region, while they are mainly found spread throughout the cerebral cortex in people with LBD.
While it is unclear exactly how Lewy bodies develop, their build-up in the brain has been linked to reduced levels of neurotransmitters - particularly acetylcholine and dopamine - nerve cell damage and loss of brain tissue.
As mentioned previously, the symptoms of LBD overlap with those of Parkinson's; many people with Parkinson's experience memory and thinking problems associated with dementia, while many individuals with LBD will experience movement problems associated with Parkinson's.
This overlap has led some researchers to believe LBD and Parkinson's is triggered by the same abnormalities in the way the brain processes the protein alpha-synuclein.
Some individuals with LBD and Parkinson's with dementia may also have beta-amyloid plaques and tau tangles in their brain, which are hallmarks of Alzheimer's disease.
The signs and symptoms of LBD
Problems with attention and alertness are very common among people with LBD, and the severity of these symptoms fluctuate frequently throughout the day.
Similar to individuals with Alzheimer's, people with LBD may experience cognitive impairment - particularly memory loss - though this is likely to be less prominent than with Alzheimer's.
Behavioral and mood symptoms, such as anxiety and depression, may occur with LBD.
Most people with LBD experience visual hallucinations - seeing things that are not there - while a smaller proportion may experience auditory hallucinations.
Around two thirds of people with LBD experience movement disorders similar to those seen in Parkinson's - including slowed movement, tremors, rigid muscles and shuffling movements when walking - and this worsens as the disease progresses.
Sleep disorders are another common symptom of LBD, as are changes in autonomic body functions, such as blood pressure, temperature and bowel function.
Susan Williams explained how her husband displayed a mix of different symptoms - including hallucinations, anxiety, depression, sleeplessness and impaired movement - which rapidly worsened in the months before his death.
"They present themselves like a pinball machine," she told People magazine. "You don't know exactly what you're looking at." And this is one of the many reasons why it is so difficult to diagnose LBD.
There is no single test for LBD. As with other forms of dementia, diagnosis of LBD relies on clinical evaluation, in which a health care professional will assess a patient's physical and neurological symptoms and make a professional judgment as to whether they may have the condition.
Many medical professionals are unfamiliar with LBD, which means a patient may see several doctors before being diagnosed with the condition.
The National Institute on Aging (NIA) recommend seeking out a neurologist for an LBD diagnosis, as they are more likely to be skilled in that area. If this is not possible, then a geriatric psychiatrist, a neuropsychologist or a geriatrician may also have experience with diagnosing LBD.
To reach a diagnosis of LBD, a medical professional will typically conduct a series of tests to rule out other conditions. They may conduct a neurological examination, which may involve tests of reflexes, eye movements, balance and sense of touch.
They may also assess a patient's mental abilities and conduct a series of blood tests - to rule out vitamin deficiency associated with poor brain function, for example - and brain scans, such as magnetic resonance imaging (MRI) and computed tomography (CT), which can rule out brain tumors and check for signs of Alzheimer's.
However, doctors are unable to reach a definitive diagnosis using these tests. At present, only a brain autopsy after death can diagnose LBD with certainty.
On the next page we look at the frequency of LBD misdiagnosis, the treatment options for the condition, and what is being done to raise LBD awareness.