An 85-year-old man comes with complaints of memory deficits. His daughter accompanies him and states that he has had symptoms for the last 2-3 years. He has no movement disorders, no hallucinations, and no other complaints. His laboratory evaluation is negative, CT and MRI of his brain reveal no acute process but some cerebral atrophy. Which of the following is the most likely diagnosis?

The most likely diagnosis for this 85-year-old man is Alzheimer's disease.

Here's the step-by-step reasoning:

1. Age: Alzheimer's disease is most common in people over 65, and the risk increases with age. Our patient is 85, which puts him in a high-risk group.

2. Symptoms: The patient has been experiencing memory deficits for the last 2-3 years. This is a common symptom of Alzheimer's disease, which often starts with difficulty remembering new information because the disease typically impacts the part of the brain associated with learning first.

3. No movement disorders or hallucinations: While these symptoms can occur in other types of dementia, they are not typically associated with Alzheimer's disease, especially in the early stages.

4. Negative laboratory evaluation: Alzheimer's disease is primarily diagnosed based on patient symptoms and cognitive testing. There are no specific laboratory tests to diagnose the disease.

5. Brain imaging: The CT and MRI scans show cerebral atrophy but no acute process. This is consistent with Alzheimer's disease, which is a progressive disease that causes brain cells to waste away (atrophy) and die.

Therefore, based on the patient's age, symptoms, lack of other neurological symptoms, and brain imaging findings, Alzheimer's disease is the most likely diagnosis.