Advanced Alzheimer's Disease: The patient's inability to recognize his wife and lack of verbal communication are consistent with the severe cognitive decline seen in advanced stages of Alzheimer's disease. This diagnosis is most likely given the patient's baseline condition and the absence of other symptoms.

Frontotemporal Dementia: This condition can also lead to significant cognitive decline and changes in personality or behavior, including a lack of recognition of familiar individuals. However, it typically presents with more prominent changes in behavior or language early in the disease course.
Vascular Dementia: While less likely given the absence of other symptoms like focal neurological deficits, vascular dementia can cause significant cognitive decline. The lack of recognition and verbal communication could be part of a multi-infarct dementia picture.
Lewy Body Dementia: Characterized by fluctuations in cognitive function, visual hallucinations, and Parkinsonian motor symptoms, Lewy body dementia could be considered if the patient had a history of these symptoms. However, the information provided does not strongly support this diagnosis.

Creutzfeldt-Jakob Disease: Although rare, this prion disease can cause rapid cognitive decline, including memory loss and changes in behavior. It is crucial to consider due to its fatal outcome and the need for prompt diagnosis to prevent further transmission.
Normal Pressure Hydrocephalus (NPH): NPH can cause cognitive decline, gait disturbances, and urinary incontinence. While the patient's symptoms do not fully align with NPH, it is a treatable condition, making it a "do not miss" diagnosis.
Hypothyroidism: Severe, untreated hypothyroidism can lead to cognitive decline and altered mental status. Given its treatability, it's essential to rule out hypothyroidism as a cause of the patient's condition.

Prion Diseases Other Than Creutzfeldt-Jakob Disease: Such as fatal familial insomnia or Gerstmann-Sträussler-Scheinker disease, these are extremely rare and typically present with distinct features in addition to cognitive decline.
Whipple's Disease: A rare, systemic bacterial infection that can cause cognitive decline among other symptoms. It would be unusual for Whipple's disease to present solely with cognitive symptoms without other systemic signs.
Hashimoto's Encephalopathy: A rare condition associated with Hashimoto's thyroiditis, characterized by cognitive decline and altered mental status. It is treatable with corticosteroids, making diagnosis important.