Final answer:
A subdural hematoma is the most probable cause of the crescent-shaped lesion on a head CT in a patient on Warfarin and with a history of chronic alcoholism, due to increased bleeding risk and potential for unnoticed head trauma. Hence, option (1) is correct.
Step-by-step explanation:
The most likely cause of the crescent-shaped lesion on the head CT of an elderly patient who is on Warfarin and is a chronic alcoholic is a subdural hematoma. This type of hematoma typically presents as a crescent-shaped lesion on CT scans and is often associated with conditions that lead to increased bleeding, such as anticoagulant therapy with Warfarin.
Chronic alcoholism is another risk factor that contributes to the likelihood of a subdural hematoma due to potential falls or minor head injuries that may go unnoticed and the general effects of alcohol on the brain's vasculature.
Additional signs that support the diagnosis of a subdural hematoma include the presence of edema surrounding the hematoma, which can exacerbate the pressure on the brain tissue, potentially leading to functional impairment and displacement of structures such as the lateral ventricles.