Question

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. Dissociated dementia
• B. Schizophrenia
• C. Multi infarct dementia
• D. Alzheimers disease

Hint:

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.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
A 70 year old man has trouble recognising familiar faces, called prosopagnosia, along with memory loss and hallucinations of a voice commenting on him in the third person, all starting within the last month. His reflexes are increased on exam, and his mini mental state score is 20 out of 30, showing mild to moderate cognitive impairment. We need the best diagnosis for this picture.

Step 2: Key Concept:
Multi infarct, or vascular, dementia comes from a series of small strokes in the brain. It often shows a relatively sudden or step wise onset, focal neurological signs such as increased or asymmetric reflexes, and cognitive loss that can include specific deficits like face recognition trouble depending on which brain areas were hit. Alzheimer's disease, in contrast, usually creeps in slowly over one to several years, without early focal neurological signs like brisk reflexes.

Step 3: Detailed Explanation:
The short one month time course here is far too fast for typical Alzheimer's disease, which develops gradually and is usually noticed only after a year or more of slow decline.
The increased deep tendon reflexes are a focal neurological sign, pointing to actual damage in specific motor pathways in the brain, which is a hallmark of vascular injury rather than the diffuse, gradual degeneration seen in Alzheimer's disease.
Prosopagnosia points to damage in a specific brain region that handles face recognition, fitting with patchy, localized infarcts rather than the more even, widespread cortical loss typical of Alzheimer's disease.
Hallucinations and cognitive decline can both be explained as complications of the vascular brain injury affecting multiple areas.
Schizophrenia is very unlikely to begin for the first time at age 70, and it would not explain the memory loss, the prosopagnosia, or the increased reflexes, since schizophrenia is a primary psychotic illness without this kind of focal neurological sign.
Dissociated dementia is not a standard diagnostic entity and does not fit this organic, focal neurological picture at all.

Step 4: Final Answer:
The fast onset, focal neurological sign of increased reflexes, and patchy cognitive deficits such as prosopagnosia together point to multi infarct dementia.