<prompt> Most common site of perilymph fistula ?Round windowOval windowOtic capsuleAttic  <response>: Ans. is b i.e., Oval window Perilymph fistula In this condition, perilymph leaks into the middle ear through the oval or round window. Perilymphatic fistula so positive fistula test may occur due to a defect in one of three locations : 1. Oval - window most common site Stapedectomy surgery for otosclerosis Head trauma or Barotrauma Pressure injury Acoustic trauma 2. Round window rupture of round window membrane Barotrauma :- SCUBA diving, airplane pressurization Congenital malformations mondini dysplasia 3. Otic capsule Another possible location for a fistula is in the bone of the ear the otic capsule. This is a rare condition where the bone between the ear and brain area is missing or thin, causing symptoms very similar to that of round or oval window fistula. Causes are :- Superior canal dehiscence syndrome Cholesteotoma Fenestration surgery surgically created window in horizontal SCC Erosion of Horizontal lateral SCC due to any cause Temporal bone fracture Micro fissure 