What is Superior Semicircular Canal Dehiscence (SSCD)?
Your inner ear is comprised of balance canals (semicircular canals), balance organs, and the hearing organ (cochlea). In most patients, the inner ear is surrounded by a dense layer of bone. Superior Semicircular Canal Dehiscence (SSCD) is a condition in which there is an absence of the bony covering over one of the semicircular canals, resulting in an abnormal opening between the brain and the semicircular canal. Although many cases are asymptomatic, some patients experience problems with hearing and balance.
Symptoms of SSCD
SSCD is sometimes described as the “great otologic mimicker” due to its tendency to present symptoms that resemble many other ear disorders. It is therefore frequently misdiagnosed. To illustrate the similarity between SSCD and other conditions, the symptoms listed below are matched with a few disorders that also may cause these symptoms. Please note that this is not an exhaustive list of conditions.
- Hearing loss – Otosclerosis
- Fluctuating hearing loss –Meniere’s disease
- Vertigo – Meniere’s disease, Vestibular migraine, Benign paroxysmal positional vertigo
- Fullness in the ear and hearing loud breathing – Eustachian tube disorders
- Pulsatile Tinnitus – Infections, Eustachian tube disorders, Otosclerosis, Vascular conditions, Tumors
The most common symptoms of SSCD are vertigo, typically induced by sudden and loud sounds, sound distortion, fullness or pressure in the ear, and autophony, which is when you hear your voice resonating or echoing in your head. Other sounds in your body may also be amplified, such as your breathing, bowel sounds, and heartbeat.
What Causes SSCD?
There are several hypothesized reasons for the development of SSCD. In some cases, the absence of bone covering the superior semicircular canal may be due to a birth defect that occurred during inner ear development (i.e., congenital). Head trauma, certain infections, and gradual bone thinning with aging may also be causes.
Patients who have elevated intracranial pressure, which gradually remodels and thins the bone over the inner ear, may also develop SSCD. It is also possible that SSCD is multifactorial. It’s thought that up to 20% of people have some degree of bone loss in this area, but never experience the symptoms of SSCD.
An SSCD diagnosis comes after taking a medical history of symptoms, physical examination, followed by computed tomography (CT) scan of the ear to identify the anatomic defect. In some cases, the defect is identifiable with magnetic resonance imaging (MRI).
Although many people may have thin or no bone tissue in the area where SSCD is concerned, they do not have the syndrome if they do not experience symptoms. A thin layer of bone may be present; however, the bony covering of the semicircular canal may be too thin to be detected by current imaging technology.
When SSCD is suspected, our audiologists may perform tests designed to induce the symptoms of SSCD or to support the diagnosis.
Options for managing SSCD include observation or surgical treatment. Observation may include avoiding known triggers (e.g., loud noises, rapid head movement) that produce symptoms. Surgery usually involves plugging the involved semicircular canal, resurfacing the bony defect over the canal, or a combination of these techniques. Depending on the location of the defect and the unique anatomy of a patient’s temporal bone, the procedure is performed either through the mastoid bone (behind the ear) or via a middle fossa craniotomy (a window of bone removed above the ear) to obtain access to the defect in the semicircular canal.
Surgery is performed to address severe and bothersome symptoms such as vertigo, autophony, and pulsatile tinnitus. Surgery is usually not offered to address hearing loss alone. Regardless of the surgical approach, there is a small risk of permanent hearing loss.
Another relatively newer technique is called round window reinforcement. Although this technique carries a lower risk of hearing loss and is performed entirely through the ear canal, its efficacy remains controversial.
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Whether your symptoms are mild or severe, developing superior semicircular canal dehiscence can disrupt your lifestyle in significant ways. At Associates of Otolaryngology, we have the diagnostic tests and expertise to confirm your diagnosis. For severe cases, all surgical options may be offered.