Final answer:
In the case of an 80-year-old man with vascular dementia presenting with right hemiparesis and mutism, E. Complete loss of the gag reflex is the sign not compatible with this clinical presentation, as the gag reflex generally remains intact with upper motor neuron lesions associated with strokes in dementia.
Step-by-step explanation:
An 80-year-old man with known vascular dementia presents with new onset right hemiparesis and mutism. When considering the clinical presentation, the sign that is not compatible is E. Complete loss of the gag reflex. This is because the gag reflex is usually preserved in patients with vascular dementia and would not typically be lost unless there was a brainstem lesion. The other options listed, such as Meyerson's sign, right-sided Hoffman's sign, right-sided Babinski's sign, and a positive palmomental reflex, are all findings that can be associated with upper motor neuron lesions, which may occur in strokes—a common cause of acute neurological symptoms in someone with vascular dementia.