During preparation of the teeth for installment of an orthopedic appliance, a 65-year-old woman complained of a sharp headache, a sensation of heat, nausea, numbness of the limbs, and impaired vision. Objectively, asymmetric due to the smoothed-out nasolabial fold on one side, she has difficulty speaking. Her blood pressure is 150/90 mm Hg. Make the provisional diagnosis.