Symptoms of significant brain atrophy include progressive cognitive impairment involving multiple cognitive functions, otherwise known as dementia, seizures and aphasia, which is the disruption in the understanding or production of language or both.
The Senate majority leader has somewhat less official power than the Speaker of the House. This is because the vice president is technically the Senate's presiding officer, a ceremonial position that calls chiefly for casting a vote in the event of a tie.
For that situation the House Minority Leader can play the role of a de facto leader of the opposition, often more so than the Senate Minority Leader, due to the more partisan nature of the House and the greater role of leadership.