The Most Misdiagnosed Type of Dementia

by Karen D. Sullivan, PhD, ABPP

The news recently suggested that beloved actor Robin Williams had Lewy body dementia (LBD). LBD is thought to be the most misdiagnosed type of dementia due to the lack of access to dementia experts and considerable overlap between LBD and its two closest conditions: Alzheimer’s disease and Parkinson’s disease with dementia. A correct dementia diagnosis matters for many reasons including identifying what medicines will help and, in the case of LBD, which to avoid, and allows patients and families to connect with community resources.

LBD is an umbrella term for two types of dementia: dementia with Lewy bodies and Parkinson’s disease dementia, associated with the presence of Lewy bodies-abnormal protein deposits called alpha-synuclein-in the brain.

Dementia with Lewey bodies causes changes in a person’s thinking, motor abilities and behavior that interfere with daily functioning. The main symptoms of dementia with Lewey bodies are fluctuating cognitive impairment, well-formed and recurrent visual hallucinations and motor symptoms like tremor and rigidity. Suggestive symptoms of dementia with Lewey bodies include repeated falls, syncope (i.e. fainting or passing out), REM sleep disorder (acting out of one’s dreams, often in an aggressive manner), and trouble with the autonomic nervous system (blood pressure rising and falling unpredictably, urinary incontinence and constipation).

Diagnosing LBD

Without MRI or CT scans or blood tests that can reliably diagnose Dementia with Lewey bodies, neuropsychologists (clinical psychologists with expertise in the brain) are increasingly called upon to provide the cognitive assessments that are often considered the most accessible gold standard tool for the diagnosis of a specific dementia and how it is progressing.

The most difficult distinction is between dementia with Lewey bodies and Parkinson’s disease dementia, because the symptoms are very similar. Neuropsychologists use their skills in clinical interviewing, alongside other techniques, to separate these two diseases based on the onset and symptoms. If the onset of dementia is within one year of motor symptoms, it is more likely to be dementia with Lewey bodies.

In contrast, if the onset of the motor symptoms is more than one year earlier than the onset of dementia, PDD is more likely. All individuals with PDD have motor symptoms at the time of a dementia diagnosis, in comparison to only 25-50 percent of those with dementia with Lewey bodies when diagnosed.

Separating dementia with Lewey bodies from Alzheimer’s disease (AD) is more straightforward with the right diagnostic tools (paper and pencil cognitive testing), although it can still be tricky. Short-term memory loss tends to be a more prominent symptom in early AD when compared with early dementia with Lewey bodies, whereas those with dementia with Lewey bodies usually experience problems in the realm of executive functioning-planning, organization and the processing of visual information. Well-formed and recurrent visual hallucinations are much more frequent in early-stage dementia with Lewey bodies, whereas delusions (thinking someone is stealing from them) tend to be more common in AD. REM sleep disorder is also more common in early dementia with Lewey bodies.

Treating LBD

Recent research suggests that LBD patients might have better responses to memory-enhancing medications (cholinesterase inhibitors such as Aricept).

A diagnosis of LBD also alerts medical providers to avoid medications that can aggravate symptoms dramatically, such as traditional antipsychotics, such as haloperidol (Haldol). Approximately 60 percent of LBD patients treated with these medications show distressing signs of sedation, decreased ability to move, or a life-threatening condition called neuroleptic malignant syndrome that develops with fever, severe muscle cramps and alterations in mental status.

Behavioral interventions may help families of dementia with Lewey bodies patients cope with cognitive symptoms, difficulty with eating because of tremor and fall prevention. For more information on LBD, visit


Dr. Sullivan, a clinical neuropsychologist at Pinehurst Neuropsychology, can be reached at 910-420-8041 or