Question:hard
A 70 year old man presents with a history of prosopagnosia, loss of memory, and third person hallucinations since 1 month. On examination, deep tendon reflexes are increased, and the mini mental state examination score is 20/30. What is the most likely diagnosis?
A 70 year old man presents with a history of prosopagnosia, loss of memory, and third person hallucinations since 1 month. On examination, deep tendon reflexes are increased, and the mini mental state examination score is 20/30. What is the most likely diagnosis?
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A fast, about 1 month, onset plus a focal neurological sign such as increased reflexes plus patchy deficits like prosopagnosia points to vascular, multi infarct dementia rather than the slow course of Alzheimer's.
Updated On: Jul 8, 2026
- Dissociated dementia
- Schizophrenia
- Multi infarct dementia
- Alzheimers disease
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The Correct Option is C
Solution and Explanation
Step 1: Understanding the Concept:
This question wants you to use the speed of onset and the presence of a focal neurological sign to pick between two dementia types and two non-dementia options.
Step 2: Key Approach:
Compare the timeline and the exam finding against what each disease typically looks like, rather than only matching the symptom list.
Step 3: Detailed Explanation:
One month is a short window for cognitive decline. Alzheimer's disease is a slow, gradually worsening illness that usually takes well over a year to become this noticeable, so the timeline argues against it here.
Increased deep tendon reflexes on exam is a sign that a specific motor pathway has been damaged, which points toward focal brain injury from small strokes rather than the diffuse, slowly spreading changes of Alzheimer's disease.
Multi infarct dementia fits both of these findings well, since repeated small strokes can strike quickly, in a step wise pattern, and can also leave behind focal signs like brisk reflexes along with patchy cognitive loss, which explains the prosopagnosia as damage to the specific area that reads faces.
A mini mental state score of 20 out of 30 confirms real cognitive impairment, which supports a dementia diagnosis over a purely psychiatric one.
Schizophrenia does not explain increased reflexes or true memory loss, and a first psychotic break at 70 years old would be unusual, so it is a poor match. Dissociated dementia is not an accepted category and offers no mechanism for the findings.
Step 4: Final Answer:
The rapid, one month onset with a focal sign of increased reflexes fits multi infarct dementia better than the slow course of Alzheimer's disease.
This question wants you to use the speed of onset and the presence of a focal neurological sign to pick between two dementia types and two non-dementia options.
Step 2: Key Approach:
Compare the timeline and the exam finding against what each disease typically looks like, rather than only matching the symptom list.
Step 3: Detailed Explanation:
One month is a short window for cognitive decline. Alzheimer's disease is a slow, gradually worsening illness that usually takes well over a year to become this noticeable, so the timeline argues against it here.
Increased deep tendon reflexes on exam is a sign that a specific motor pathway has been damaged, which points toward focal brain injury from small strokes rather than the diffuse, slowly spreading changes of Alzheimer's disease.
Multi infarct dementia fits both of these findings well, since repeated small strokes can strike quickly, in a step wise pattern, and can also leave behind focal signs like brisk reflexes along with patchy cognitive loss, which explains the prosopagnosia as damage to the specific area that reads faces.
A mini mental state score of 20 out of 30 confirms real cognitive impairment, which supports a dementia diagnosis over a purely psychiatric one.
Schizophrenia does not explain increased reflexes or true memory loss, and a first psychotic break at 70 years old would be unusual, so it is a poor match. Dissociated dementia is not an accepted category and offers no mechanism for the findings.
Step 4: Final Answer:
The rapid, one month onset with a focal sign of increased reflexes fits multi infarct dementia better than the slow course of Alzheimer's disease.
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