The concept of superior semicircular can now the distance is very interesting.

 It is based on a mobile third window. 

Here is the concept in a simple analogy. 

Hearing and Balance function are housed in the same organ, and share the same fluid.  Hearing is based on vibrations.  Sound waves pushes in (and then out) on the oval window, forcing fluid to oscillate through a long tube and bulges the round window out (and then in) at the other end.

 That is like having a building with a long hallway, with two doors at either end.  If the entire hallway is packed with people, and another person enters... somebody must exit at the other end.  The traffic movement at that other end is detected as sound.

 The balance function on the other hand is a closed system, set up like a race track.  Movement of the fluid (or people- as in our analogy) within the racetrack is detected as head movement.

 As it turns out, the racetrack is connected to the long hallway.  Now, as long as the racetrack is intact, the hallway and the racetrack function independently.  However if another door or window is opened in the racetrack, then people can leak out of that window.  That would decrease the traffic of the original exit (the round window), decreasing the sensation of sound.  It would increase the traffic through the racetrack, which would be detected as increased head movement when there really was none.  (Sensation of movement when there is none is called vertigo).

 As a point of clarification, all of these windows are typically still covered with a membrane, so that the fluid does not actually leak out.  Since we are really talking about pulses and vibrations, it is the energy of these pulses and vibrations that is "leaking out".  (The fluid does not need to leak out for the energy to leak out).

 The leaky window is the superior semicircular canal dehiscence.  Therefore closure of that window can help stop both the sensation of dizziness and improve conductive hearing loss.

Surgical Treatment

 There are two ways to surgically repair a superior semicircular canal dehiscence.  One way is to cover the window by placing something on top of the window.  The other way is to plug the canal (racetrack).

Each method has its own risks and benefits.  The patient has two weigh out his or her own risks and benefits with the symptoms that are present.

Sometimes the choice is already made for you because so much of the canal is dehiscent (exposed) that any attempt to cover it will crush the canal and in effect plug it.

Middle Fossa Resurfacing:

The idea is to prevent the leakage of fluid pressure energy, while maintaining continuity of the fluid flow internally by covering the window with a firm solid substance.

This is done with a small piece of bone that is laid on top of the weakened (dehiscent) area.  Synthetic bone paste is used to "concrete mortar" that piece of bone in place.  This procedure involves opening up a window in the skull and lifting up the brain to get to the area of the leak.

Canal plugging:

The idea is to block the fluid flow through the semicircular canals, thereby shutting down the sensors so that the false sensation of motion is prevented.  Abnormal fluid flow causes so much dizziness and distress that it is better to have no fluid flow than abnormal flow.

This can be done either through a middle fossa approach, or through the trans-mastoid approach.  The trans-mastoid approach is done through an incision behind the ear.  It does not involve any manipulation of the brain, and thus is less risky neurologically.  However, the mastoid approach is slightly more risky to the hearing and facial nerve.