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Difficulty: EasyNeurocognitive Disorders

A 72-year-old man is brought to the clinic by his wife due to a 1-year history of progressive memory decline. She reports that his cognitive abilities fluctuate significantly; on some days he is highly alert, while on other days he is deeply confused. Over the past 6 months, he has frequently reported seeing small animals in their living room, even though none are present. Additionally, his sleep is highly disturbed; he often yells and physically thrashes in bed, appearing to act out his dreams. On physical examination, the patient has a shuffling gait, a resting tremor in his right hand, and mild cogwheel rigidity. Laboratory studies reveal a thyroid-stimulating hormone (TSH) level of 2.1 µU/mL (normal: 0.4-4.0 µU/mL) and a normal vitamin B12 level. Which of the following is the most likely diagnosis?

  1. Dementia with Lewy bodiesAnswer
  2. B
    Schizophrenia
  3. C
    Brief psychotic disorder
  4. D
    Hypothyroidism-induced cognitive impairment
  5. E
    Substance-induced psychotic disorder

Answer

Dementia with Lewy bodies
The correct answer is Dementia with Lewy bodies. This neurodegenerative disorder is characterized by a progressive cognitive decline accompanied by distinctive core clinical features. A probable diagnosis requires the presence of dementia and at least two of the following: fluctuating cognition with pronounced variations in attention and alertness, recurrent visual hallucinations that are typically well-formed and detailed, rapid eye movement (REM) sleep behavior disorder (acting out dreams), and spontaneous features of parkinsonism (e.g., shuffling gait, resting tremor, rigidity). This patient's presentation fits perfectly with all of these classic clinical hallmarks.

Step-by-Step Solution

1
Analyze the patient's primary symptoms and timeline.
The patient has a 1-year history of cognitive decline with marked fluctuations, recurrent visual hallucinations, REM sleep behavior disorder, and parkinsonism.
Identifying the specific combination of cognitive, psychiatric, and motor symptoms is necessary to differentiate among the neurocognitive disorders.
2
Evaluate the laboratory results.
TSH and Vitamin B12 are normal.
This rules out common reversible causes of dementia and psychosis in the elderly.
3
Match the clinical presentation to the diagnostic criteria.
The symptom profile perfectly matches the core diagnostic criteria for Dementia with Lewy bodies.
Dementia with Lewy bodies requires dementia plus two or more core features: visual hallucinations, parkinsonism, REM sleep behavior disorder, and fluctuating cognition.

Key Concept

Diagnosis of Dementia with Lewy bodies based on its core clinical features.
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Topics

Neurocognitive Disorders

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