MKSAP Quiz: Evaluation for mild dementia
A 65-year-old man is evaluated for a 3-year history of mild dementia with fluctuations in attentiveness and visual hallucinations. He has also acted out his dreams in his sleep a few times over the last 2 years. He has no history of tremor. Following a physical exam and other tests, what is the most likely diagnosis?
A 65-year-old man is evaluated for a 3-year history of mild dementia with fluctuations in attentiveness and visual hallucinations. He has also acted out his dreams in his sleep a few times over the last 2 years. He has no history of tremor.
On physical examination, vital signs and the remainder of the physical examination are normal with the exception of mild rigidity of bilateral upper extremities.
MRI of the brain shows no significant vascular disease or hippocampal atrophy.
Which of the following is the most likely diagnosis?
A. Alzheimer disease dementia
B. Dementia with Lewy bodies
C. Frontotemporal dementia
D. Parkinson disease dementia
MKSAP Answer and Critique
The correct answer is B. Dementia with Lewy bodies. This content is available to MKSAP subscribers as Question 88 in the Neurology section. More information about MKSAP is available online.
The most likely diagnosis is dementia with Lewy bodies (Option B). Of the four core features of this condition—parkinsonian motor features (particularly gait problems and slowness of movements), visual hallucinations, rapid eye movement (REM) sleep behavior disorder, and frequent fluctuations in attention—this patient has three: parkinsonism, hallucinations, and attention fluctuations. The latter may manifest as acute confusional episodes in which the patient is less responsive than usual or as intermittent days with excessive daytime sleepiness.
Additionally, this patient may also have REM sleep behavior disorder (acting out his dreams), but polysomnography is required to confirm this diagnosis. Clinical history and neurologic examination findings are critical for the diagnosis of dementia with Lewy bodies to avoid inappropriate treatment, particularly with antipsychotic drugs to which these patients are uniquely sensitive. Indicative biomarkers also have been developed to support the diagnosis when sufficient clinical history is lacking.
Alzheimer disease dementia (Option A) is associated with hippocampal atrophy on MRI of the brain, and patients do not typically have associated parkinsonism (although this can happen in the later stages of disease). Distinguishing Alzheimer disease from dementia with Lewy bodies on the basis of cognition alone can be difficult, but other symptoms can help differentiate the two. REM sleep behavior disorder is much more common in dementia with Lewy bodies than Alzheimer disease. Delusions and hallucinations are common in dementia with Lewy bodies and frequently occur at the mild stages of disease. Additionally, significant sleep problems, especially daytime sleepiness, can be a debilitating feature of dementia with Lewy bodies. The fluctuations in Alzheimer disease can be described as days when memory is better or worse, whereas in dementia with Lewy bodies, the bad days involve decreased alertness.
The patient does not have the behavioral or language symptoms typically associated with frontotemporal dementia (Option C). In some familial forms of the disease, there can be parkinsonism, but this is rare. Visual hallucinations are not typical of frontotemporal dementia.
Parkinson disease dementia (Option D) can have symptoms similar to those of dementia with Lewy bodies. However, diagnosis of Parkinson disease dementia requires that the motor symptoms precede the cognitive impairment by at least 2 years.
Key Points
- The clinical diagnosis of dementia with Lewy bodies rests on the key features of dementia, parkinsonian motor features, visual hallucinations, rapid eye movement sleep behavior disorder, and frequent fluctuations in attention.
- Unlike Alzheimer disease, delusions and hallucinations are common in dementia with Lewy bodies, as are daytime sleepiness and rapid eye movement sleep behavior disorder.