Almost every hotel with an elevator has at least one handicapped-accessible room, although five-star hotels are more apt to cover all bases, such as grip handles and lower sinks. Although ramps have begun to appear at Turkish brick-and-mortar museums, don't expect seamless access. (The crumbling ruins of outdoor archaeological sites are another story altogether; confirm with your travel agent that your needs will be accommodated.) However, Turkish hospitality being what it is, it'll be the odd tour guide or group leader who won't bend over backward to accommodate your individual needs.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.