Differential Diagnosis
- Single most likely diagnosis
- C. Dementia with Lewy bodies: This condition is characterized by visual hallucinations, cognitive decline, and parkinsonian motor symptoms such as rigidity and mask-like expression. The patient's symptoms of visual hallucinations, poor attention, difficulty with daily activities, and parkinsonian features (mild right arm rigidity, mask-like expression) are consistent with Dementia with Lewy bodies.
- Other Likely diagnoses
- A. Alzheimer’s type dementia: While Alzheimer's is the most common cause of dementia, the presence of visual hallucinations, parkinsonian features, and a relatively rapid decline in cognitive and motor function make Dementia with Lewy bodies more likely. However, Alzheimer's cannot be ruled out without further testing.
- B. Frontotemporal dementia: This condition typically presents with changes in personality, behavior, and language, which are not prominent in this patient's presentation. However, some forms of frontotemporal dementia can present with parkinsonian features and cognitive decline, making it a possible consideration.
- Do Not Miss diagnoses
- D. Normal pressure hydrocephalus: Although the MRI of the brain is reported as normal, normal pressure hydrocephalus can sometimes present with subtle or non-specific changes on imaging. The patient's history of falls and gait disturbance ("legs don't seem to do what I want") could be indicative of normal pressure hydrocephalus, which classically presents with the triad of gait disturbance, dementia, and urinary incontinence. Given the potential for significant improvement with treatment (shunting), this diagnosis should not be missed.
- Rare diagnoses
- Vitamin B12 deficiency: Although rare, a deficiency in vitamin B12 can cause cognitive decline, neuropsychiatric symptoms, and neurological signs such as ataxia and weakness. Given the patient's lack of past medical history and medication use, a vitamin B12 deficiency is a rare but possible consideration.
- Prion diseases: These are rare, degenerative brain disorders that can present with rapidly progressive dementia, ataxia, and myoclonus. While the patient's presentation does not strongly suggest a prion disease, they are important to consider in the differential diagnosis of rapidly progressive dementia.