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Symptoms, Causes, and Treatment of Perilymphatic Fistula – Superior Canal Dehiscence
Symptoms and Causes of Perilymphatic Fistula
Perilymphatic fistula is a caused by a loss the labyrinth bony wall integrity or by a defect in the oval window. Oval window is a membrane separating labyrinth from the middle ear. Potential causes are trauma, surgical procedures, or any disease process eroding the bony canal. This defect may be congenital as well. Occasionally, the defect occurs spontaneously while straining but there should be some preexisting wall weakness.
Classically, the story begins with hearing a pop in the ear during straining or head injury. Vertigo and some level of hearing loss, tinnitus, or ear fullness will follow. Subsequently, attacks of vertigo and hearing loss lasting from seconds to days may recur. The attacks are precipitated by pressure change due to coughing, sneezing or straining. Loud sound may also bring up vertigo and/or nystagmus.
Under normal conditions the labyrinth canal system is an enclosed system. Fistula is a hole in the wall, leading to communication to the outside; either into the middle ear or into the intracranial space.
Diagnosis of Perilymphatic Fistula
Presence of perilymphatic fistula may be confirmed by special maneuvers. Sealed pressure onto the auditory canal is expected to cause vertigo and nystagmus. Similar response may be produced by straining with closed nostrils.
Defects in the bone architecture in vicinity of the labyrinth are visualized with high a resolution thin slice CAT scan of the temporal bones.
Treatment of Perilymphatic Fistula
Noninvasive treatment consists of prolonged bed rest with elevated head for at least a week and restriction of all types of straining for a couple of months.
In cases of known bone lesions or failed conservative treatment, surgical repair is an option.
Superior Canal Dehiscence
Supperior Canal Dehiscence is a unique version of perilymphatic fistula caused by thinning of the bone separating labyrinth interior from the intracranial space. The main symptom is vertigo provoked by loud noise and pressure change.
Besides vertigo attack analogous to other forms of perilymphatic fistula, half of the patients hear their own voice unusually loud (autophony), hear their heart beats and may even hear the eye movements. Straining with closed nostrils reproduces the symptoms.
High Resolution CT of the temporal bones may detect a thinning or discontinuity of the bone separating superior canal from the intracranial cavity.
The main treatment approach is to avoid vertigo causing activity.
Surgical repair is another option.