Superior Canal Dehiscence

May 12, 2019 - by Preview - in Uncategorized

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Superior canal dehiscence is a rare condition and is one of a group of diseases caused by a “third mobile window”. It is due to an abnormal connection between the inner ear and the brain cavity.

Patients complaint of dizziness may be vertigo (a “spinning sensation”) and/or unsteadiness and/or lightheadedness, lasting a few seconds. This is triggered by loud sounds (this is called the Tullio Phenomenon) and with the dizziness there can be a short-lasting bobbing of vision (oscillipsia).

The dizziness can also be triggered by sneezing, lifting heavy weights, straining, nose blowing, popping one’s ear and coughing (this is called Hennebert’s Symptom).

Another set of complaints that occur with or without dizziness, are oversensitive distorted hearing (normal sounds are too loud) or deafness. Some patients complain of the ability to hear their eyes moving or blinking and can hear their own footsteps or voice echoing in the affected ear.

There may be a history of head trauma or pressure injury to the ear (barotrauma)

If the patient is asked to “hum” the patient hears the “hum” louder in the affected ear.

Pressing on the tragus of the affected ear induced upwards and in-tortion – Hennebert’s Sign.

Stimulation of the mastoid process behind the ear with a vibrating device can induce a down beat nystagmus with a torsional component.

The Weber tuning fork tests lateralises to the affected ear

A 128 Hz tuning fork held on ankle is heard in affected ear.

Investigations reveal an audiogram hearing test which shows a mild “pseudo-conductive” result where, in the low frequencies, the bone conduction is better than normal, and the air conduction is normal

High resolution (0.5mm) CT imaging is required.

The treatment for this condition is mainly the avoidance of triggers and possibly a resurfacing surgical procedure

 

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