Alcohol-Related Dementia: Given the patient's history of alcoholism, this is a highly plausible diagnosis. Chronic alcohol abuse can lead to cognitive decline and dementia due to the toxic effects of alcohol on the brain.

Alzheimer's Disease: As the most common cause of dementia, Alzheimer's should be considered, especially given the patient's age. Intermittent memory trouble could be an early manifestation.
Vascular Dementia: This condition, caused by reduced blood flow to the brain, is a possibility, especially if the patient has risk factors such as hypertension, diabetes, or a history of stroke.
Normal Pressure Hydrocephalus (NPH): Characterized by the triad of gait disturbance, dementia, and urinary incontinence, NPH could be considered, although it's less common.

Vitamin B12 Deficiency: A condition that can cause cognitive decline and is often seen in alcoholics due to poor nutrition. It's crucial to diagnose and treat as it's reversible.
Hypothyroidism: Can cause cognitive symptoms and is important to diagnose as treatment can reverse symptoms.
Chronic Subdural Hematoma: Although less common, this condition can present with intermittent cognitive symptoms and is critical to diagnose due to its potential for severe outcomes if left untreated.
Brain Tumor: Although rare, a brain tumor could cause focal neurological deficits and cognitive decline, making it a critical diagnosis not to miss.

Frontotemporal Dementia: A group of diseases characterized by the progressive degeneration of the frontal and/or temporal lobes of the brain. It's less common than Alzheimer's but should be considered in differential diagnosis.
Creutzfeldt-Jakob Disease: A rare, degenerative, fatal brain disorder that can cause dementia and other neurological problems. It's essential to consider due to its rapid progression and fatal outcome.
Wernicke-Korsakoff Syndrome: A brain disorder caused by a thiamine deficiency, often seen in alcoholics. It leads to severe memory problems and is partially reversible with thiamine treatment.