This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: ENT
Third window effect is seen in 
Select and explain. 
A. Perforated tympanum, B. Dehiscent superior semicircular canal, C. Round window, D. Oval window
B: Dehiscent superior semicircular canal
Answer: B: Dehiscent superior semicircular canal 
Explanation: Ans. b. Dehiscent superior semicircular canal Dehiscence of bone overlying the superior semicircular canal can cause a constellation of vestibular and auditory symptoms and signs. These abnormalities can be understood in terms of the effect of the dehiscence in creating a third mobile window into the inner ear.