Which statement best describes a third-window disorder such as superior canal dehiscence?

• A. It causes vertigo only with head movement, not with sound
• B. It is not associated with any hearing symptoms
• C. It demonstrates decreased sensitivity to sound
• D. It allows abnormal pressure or sound transmission, producing vertigo/nystagmus

Answer: (C)

A third-window disorder creates an extra mobile window in the inner ear, so energy from sound or from pressure changes can be shunted into the vestibular system. That means vertigo and nystagmus can be triggered not just by head movements, but by loud sounds or changes in pressure (the Tullio phenomenon and related signs). Hearing symptoms are common because this abnormal transmission also alters how energy reaches the cochlea, often producing a low-frequency conductive-type hearing loss and sometimes making bone-conduction sounds feel more intense. So the description that best fits is that it allows abnormal pressure or sound transmission, producing vertigo/nystagmus.