When I finished my training, I was taught that the vast majority of dementia was Alzheimer’s disease, with occasional cases of multi-infarct dementia as well as odd syndromes such as Kreutzfeld-Jacob disease and genetic, traumatic, toxic and tumor-related syndromes. Parkinson’s disease, we were taught, caused a tremor and freezing up of a person’s movements and only very rarely was associated with any kind of memory loss.

These teachings helped us modern doctors leave behind terms such as “senility” or “hardening of the arteries” to explain cognitive loss. We still had no useful tools to change the course of dementia, but we were more scientific in our description of it.

In the last several years, however, neurologists have determined that there is a very common dementia that is associated with Parkinson’s disease. Lewy body disease or Lewy body dementia was a condition that I had been taught was not only uncommon but only accurately diagnosed at autopsy or with a brain biopsy. It appears, now, that it is quite common, comprising up to 30% of cases of dementia. It is more common in men than in women, like Parkinson’s disease but not like Alzheimer’s disease and is more common in people who have higher educational attainment. It is characterized by collections of protein known as Lewy bodies that are found throughout the cerebral cortex, rather than just in the movement centers of the midbrain, as in Parkinson’s disease.

There are some medical tests that will help to diagnose Lewy body disease, but they are not commonly performed. It is most commonly diagnosed by the identifying 2 of 4 common clinical features. These are:

1. Fluctuating cognition with varying levels of consciousness and alertness. They will fall deeply asleep and be unarousable or be very slow and confused, lasting hours sometimes, then improve to a more normal baseline, laughing and participating in conversations. Family will sometimes think they have had a stroke or a seizure.
2. Visual hallucinations. These may be quite detailed.
3. REM sleep disorder. Patients will often talk in their sleep or do complex movements, often getting up and walking or performing complex behaviors. This can be disturbing and even dangerous to a bed partner.
4. Motor features of Parkinson’s, including pill-rolling tremor, slow movements and rigidity. These features almost always follow the development of memory loss.

Patients have other clinical features such as depression, anxiety, apathy and loss of executive function (unable to clean a closet, sort and pay bills or put together a photo album.) They often have autonomic dysfunction, with fainting spells due to drop in blood pressure or inability to tolerate changes in temperature. They become unstable in their walking or standing and fall frequently. They have urinary incontinence. They have delusions that are detailed and hard to shake.

My father had this and I didn’t recognize it until about 3 months before his death. He was a very smart man, having graduated in physics from Caltech and then worked with early computers and was an important part of the space program. He worked on developing electric cars and wind power and studied the feasibility of oil shale and tar sands (not feasible and not efficient, he concluded.) He brought a supercomputer to the island of Maui and helped jump-start their technology industry. He was funny and engaging and had a knack for encouraging others by being a springboard for their ideas. He was the most compelling conversationalist I have ever known and played a mean game of scrabble.

When he lost his wife to cancer 12 years ago he began to notice some disturbing memory failures. He put those down to the stresses of home hospice and the depression that followed her death. He was capable with his laptop computer and enjoyed the early handheld computing devices, but when he got his first smartphone, the technology became more difficult for him to learn. He could use email, but forgot how it worked and never learned to access it with his iPhone. He took on the position of board president with an academic organization and wasn’t able to keep up with what he needed to do. He resigned and felt terrible about that. He tried to take blood pressure medication but would pass out unexpectedly so stopped it. He kept all of his mail and couldn’t figure out how to file it, feeling ashamed about the state of his desk. He flailed and talked in his sleep so much that his wife had to go to bed elsewhere. He would wake up at 4 in the morning, inconsolably sure that he needed to catch a plane or teach a class.

He fell frequently and when he walked or stood, would lean to one side, unaware that he was doing it. It was nerve-wracking to walk with him because he refused to take an arm and never learned to use a walker or cane. He slept more, often while sitting up, and had periods of unresponsiveness that were alarming. His falls were not minor and he gashed his face and ripped the skin on his arms, broke his hand and hit his head hard enough to spend an agitated night in the hospital. His writing became small, shaky and cramped.

It was clear he had dementia and that it wasn’t a normal kind. He saw a neurologist who thought he might have Parkinson’s disease and a wonderful gerontologist who diagnosed Alzheimer’s disease. His wife, who had been attending a dementia support group, had heard about how common Lewy body dementia was and suggested it might be that. I read the most recent literature and decided she was right. Not only did he have it, so had many of my patients over the years who I had thought had Alzheimer’s disease.

The fluctuations. The falls. The detailed hallucinations and delusions. The executive dysfunction. It isn’t subtle how different it is from Alzheimer’s disease. These are the people who come into the emergency department frequently when they are clearly worse than normal but improve overnight and return home, even though we think that’s a bad idea. They do fine until they fluctuate again and then are back. These are the difficult to handle patients with the mean delusions who drive their families or spouses nuts but are unmanageable in nursing homes. If Alzheimer’s disease were vanilla ice cream, Lewy body dementia would be rocky road, with real rocks.

My father was a sweet guy but this disease made him critical, unkind and selfish. But only sometimes. Only when we were so deliberately stupid that we didn’t understand that his reputation would be ruined if he didn’t get to the airport or to the lecture he was supposed to be giving. Only if we tried to help him walk when he could clearly do it better without our pushing him off balance. Only when he woke up scared and didn’t understand what was going on. At other times he was kind and appreciative and full of sweetness, humor and wisdom that he could no longer put express with words.

It was possible for him to stay at home with his wife for a long time with the help of caregivers. Eventually, however, the combination of impulsiveness, weakness and sleep disturbance made even 24 hour caregiver support inadequate and he had to be moved to a memory care center. The facility was really wonderful, catering to the dotty, delirious and demented, many of them with what appeared to be Lewy body dementia. He perked up briefly after moving, but then began to sleep more, sitting up in his wheelchair. He still had up times, explaining the chemical properties of tungsten, listening to a talk I needed to practice and offering good questions. He became weaker, unable to hold a cup or a fork, barely able to lift a cookie. Eventually he didn’t wake up at all and two days later died peacefully, in the care of hospice.

Since his diagnosis, I have been much more aware of those demented people who don’t have Alzheimer’s disease. It helps to know, so we don’t compare them unfavorably. They aren’t just difficult people with dementia, they are regular people with difficult dementia.

Robin Williams, the gifted actor and comedian, developed a set of disturbing symptoms in the last years of his life that were unexplained but progressive and horrible. He said goodnight to his wife one evening (she slept in a separate room because of his sleep behaviors), went to his bedroom and hung himself. An autopsy showed severe Lewy body dementia. She wrote a letter to the journal Neurology detailing their medical odyssey. It is heartbreaking to read.

We have no useful treatments for Lewy body dementia. Sometimes benzodiazepines help a bit with the sleep disorder, but my experience was that they did nothing. Anti-psychotic medication is not helpful and often can worsen the symptoms significantly. Parkinson’s medication can help with the rigidity and tremor, but my experience was that, by the time that was prominent it was more helpful for my father not to have the ability to act out his impulsivity. A wheelchair was much safer. Cholinesterase inhibitors, used in Alzheimer’s disease, are recommended but don’t help much and can cause sleep problems, nausea and drooling.

I will miss my father. I will think about his voice, his conversation, his smile, his love of math and his scientific contributions. I will remember his smell, his wispy white hair and the way he loved to have his back scratched hard. I will not miss his last 6 months, though, and I resent those nasty Lewy bodies that infested his wonderful brain.

Janice Boughton is a physician who blogs at Why is American health care so expensive?

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