Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.
An 81-year-old man is evaluated for the gradual onset and progression of memory loss over the past year. He says he has difficulty recalling the names of familiar people, has misplaced his wallet on numerous occasions, and is slower to find his car in large, crowded parking lots. He continues to manage his finances, travel with his wife, and perform the activities of daily living without difficulty. He has borderline hyperlipidemia that is managed by diet alone. A paternal uncle developed Alzheimer dementia at age 74 years. His only medications are aspirin and a daily multivitamin.
On physical examination, temperature is 36.7 °C (98.1 °F), blood pressure is 126/82 mm Hg, pulse rate is 68/min, respiration rate is 14/min, and BMI is 26. His level of alertness, speech, and gait are normal. He scores 26/30 on the Folstein Mini–Mental State Examination, losing all three points on the recall portion and one point on the orientation section for incorrectly stating today’s date.
Results of a complete blood count, serum vitamin B12 measurement, thyroid function tests, and a basic metabolic panel are normal.
An MRI of the brain without contrast shows no abnormalities.
Which of the following is the most likely diagnosis at this time?
A) Alzheimer dementia
B) Dementia with Lewy bodies
C) Frontotemporal dementia
D) Mild cognitive impairment
E) Vascular dementia
MKSAP Answer and Critique
The correct answer is D) Mild cognitive impairment. This item is available to MKSAP 15 subscribers as item 30 in the Neurology section. More information about MKSAP 15 is available online.
This patient has mild cognitive impairment (MCI), which denotes abnormal cognitive decline that is not severe enough to produce disability. His self-reported memory loss, which is confirmed by his performance on the Folstein Mini–Mental State Examination, is his only symptom; there are no other signs of dementia. Memory loss is nonspecific and is part of many dementia syndromes. However, the lack of any functional impairment in this patient makes MCI the most likely diagnosis at this time. Although there are no universally accepted criteria for MCI, the disorder has been defined as a memory abnormality corroborated by objective memory impairment on standardized tests, without general cognitive impairment or an effect on functional independence. The rate of progression to dementia is approximately 10% to 15% per year.
Alzheimer dementia is the most common cause of MCI involving memory loss. Because this patient has no functional disabilities and thus does not meet the criteria for frank dementia, Alzheimer dementia is an incorrect diagnosis at this point. He may eventually develop the disease, given that the conversion rate of MCI to dementia is roughly 10% to 15% per year and that, at autopsy, approximately 80% of patients originally diagnosed with MCI have Alzheimer dementia.
Early-stage symptoms that are characteristic of frontotemporal dementia include changes in behavior and personality, such as increasing apathy, disinhibition, or perseverative (repetitive to an exceptional degree) fixations. This patient has exhibited no such changes.
The onset of dementia with Lewy bodies could also be characterized by memory loss. Besides clearly not having dementia of any sort at this stage of his illness, this patient lacks any of the other symptoms of dementia with Lewy bodies, such as parkinsonism, visual hallucinations, psychomotor slowing, and dream enactment behavior.
Typical manifestations of vascular dementia include psychomotor slowing, a stepwise progression, and a history of stroke, none of which pertain to this patient.
Key Point
- Mild cognitive impairment denotes abnormal cognitive decline that is not severe enough to produce disability.
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