What is the most likely diagnosis for a 44-year-old patient with Down syndrome experiencing impaired memory and difficulties in daily life?

The most likely diagnosis for a 44-year-old patient with Down syndrome experiencing impaired memory and difficulties in daily life is Alzheimer's disease. Individuals with Down syndrome have a higher risk of developing dementia, particularly Alzheimer's disease, often at a much younger age than the general population. Cognitive decline in this demographic typically presents with memory impairment, difficulties in daily functioning, and changes in behavior and personality, which align with the described symptoms.

In addition, the pathophysiology of Alzheimer's disease in patients with Down syndrome is often linked to the presence of an extra copy of chromosome 21, which carries the gene for amyloid precursor protein, a key component in the development of amyloid plaques seen in Alzheimer's. These plaques are a hallmark of the disease and contribute to cognitive decline.

While stroke and delirium can cause acute changes in cognitive function, they are less likely to be the cause of ongoing memory issues and difficulties in daily living in this particular context. Tic douloureux, or trigeminal neuralgia, is related to facial pain and does not align with the cognitive symptoms presented. Thus, Alzheimer's disease is the most fitting diagnosis in this scenario, considering the patient’s age, genetic predisposition, and symptomology.