Ear complaints and balance problems can be very difficult to address, work-up, and treat. An unusual but possible cause to consider in your patients that present with a concur about vertigo concerns when exposed to noise, associated with ear fullness and / or conductive hearing loss is a disorder of the semicircular canals.
The semicircular canals are are three semicircular, interconnected tubes located inside each ear. When we say in the ear, we mean specifically housed inside the temporal bone.
There are three semicircular canals. These are the horizontal semicircular canal (also known as the lateral semicircular canal), the superior semicircular canal (also known as the anterior semicircular canal), and the posterior semicircular canal (also known as the inferior semicircular canal). The orientations of the canals cause a different canal to be stimulated by rotation of the head in different planes. The horizontal canal / lateral canal is stimulated when you turn your head to the left and right hand sides before crossing a road (transverse plane). The superior canal / anterior canal is stimulated when nodding your head (sagittal plane). The posterior canal / inferior canal is stimulated when you move your head to touch your shoulders (coronal plane). Each bony canal is fluid filled with motion sensors present at base of each canal in the dilated portion that opens into the utricle. The sensors in the dilated portion (ampullae) are motion sensitive. They are not gravity specific sensors. In the utricle and saccule there are gravity sensitive cells.
Semicircular canals require integrity of bone to function properly. Dehiscence or loss of bone covering, can affect function. Semicircular canal dehiscence (SCD) is an important entity that can present with symptoms of noise or pressure induced vertigo, autophony (unusually loud hearing your self speak), aural fullness and conductive hearing loss. SCD can have a varied presentation and mimic of other conditions.
In reviewing these cases, it is important to obtain a thorough history (ear fullness, what makes worse, for example exercise, voice louder in ear than usual, intermittent vertigo with noise, etc) and a careful examination to include supportive audiological testing and imaging (high-resolution CT images).
Semicircular canal dehiscence may occur in the superior, lateral or posterior canal. Your patient may experience vertigo, visual disturbance in which objects in the visual field appear to swing back and forth after exposure to noise or changes in pressure. Hearing loss with a conductive component can occur. The presence of autophony makes it difficult to separate from other ear disorders (otosclerosis, patulous eustachian tube, etc).
You can learn more about this topic by looking to this article:
American Journal of Otolaryngology
Vol 37 Issue 3
Christopher A. Schutt, John F. Kveton
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