Third window effect is seen in
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.
Perforated tympanum
Dehiscent superior semicircular canal
Round window
Oval window