Superior Semicircular Canal Dehiscence

What is Superior Semicircular Canal Dehiscence?

Also known as Superior canal dehiscence syndrome (SCDS) is a medical condition where there’s a thinning or complete absence of bone overlying the superior semicircular canal, one of the three canals in the inner ear responsible for balance. This condition can cause various symptoms including vertigo, hearing loss, imbalance, and sound-induced/pressure-induced symptoms such as hearing one’s eye movements or the internal sounds of the body (autophony). 

Superior Canal Dehiscence (SCD) can present with a variety of symptoms, which can vary in severity from person to person. Some individuals may experience multiple symptoms, while others may have only a few. Common symptoms of SCD include: 

• Vertigo: Episodes of dizziness or spinning sensations, often triggered by certain head movements, changes in pressure (Hennebert’s sign), loud sounds (Tullio phenomenon), coughing, and sneezing. 

• Oscillopsia: Blurriness in vision, jumping vision with change in pressure or in response to loud sounds. 

• Hearing loss: Conductive Hearing Loss. 

• Hyperacusis: Increased sensitivity to sound, where everyday noises may seem excessively loud or bothersome. 

• Pulsatile Tinnitus: Some individuals with SCD may experience a pulsating or rhythmic sound in the affected ear, often synchronized with the heartbeat. 

• Autophony: The perception of hearing one’s own bodily sounds, such as the sound of one’s voice, heartbeat, or even eye movements. Autophony can be particularly bothersome and may worsen with certain activities or postures.

Superior Canal Dehiscence (SCD) is primarily caused by a thinning or complete absence of bone overlying the superior semicircular canal (SSC) in the inner ear. Several factors can contribute to the development of SCD: 

• Congenital Factors: Some individuals may be born with thinner bone overlying the superior semicircular canal, predisposing them to SCD later in life. Congenital abnormalities or developmental issues in the formation of the inner ear structures can contribute to this condition. 
• Trauma: Head trauma or injury to the skull near the inner ear region can lead to damage or thinning of the bone covering the superior semicircular canal. Traumatic events such as falls, accidents, or surgeries in the temporal bone region may increase the risk of developing SCD. 
• Degenerative Changes: Over time, natural wear and tear on the bones of the inner ear can lead to thinning of the bone covering the superior semicircular canal. This degeneration may occur gradually with age and can contribute to the development of SCD in some individuals. 
• Idiopathic Causes: In some cases, the exact cause of SCD may be unknown (idiopathic). While the underlying mechanism remains unclear, idiopathic SCD suggests that there may be other contributing factors, such as genetic predisposition or metabolic factors, that influence the development of the condition. 
• Medical Procedures: Certain medical procedures or interventions in the temporal bone region, such as mastoidectomy (surgery to remove infected mastoid air cells), may inadvertently lead to damage or thinning of the bone covering the superior semicircular canal, increasing the risk of SCD. 
• Other Conditions: Some medical conditions or syndromes, such as osteogenesis imperfecta (a genetic disorder characterized by fragile bones), may be associated with an increased risk of developing SCD. Additionally, conditions affecting bone density or remodelling processes may help thinning bone overlying the superior semicircular canal. 

Diagnosis and treatment of Superior Canal Dehiscence (SCD) typically involves a combination of clinical evaluation, specialized testing, and individualized management approaches.  

A thorough medical history and physical examination by a healthcare professional are the first steps in diagnosing SCD. The healthcare provider will inquire about the individual’s symptoms, medical history, and any factors that may contribute to inner ear disorders. 

Specialized tests like high-resolution CT scans, Vestibular Evoked Myogenic Potentials (VEMP) and audiometric tests may help the healthcare provider in the diagnosis of SCD.

Treatment of SCD aims to alleviate symptoms, improve quality of life, and address any functional impairments associated with the condition. Treatment options may vary depending on the severity of symptoms, individual preferences, and response to previous interventions. Common treatment approaches for SCD include:

Conservative Management: 

• Lifestyle Modifications: Avoiding triggers such as loud sounds, changes in pressure, or specific head movements may help reduce symptoms of vertigo and dizziness. 
• Hearing Protection: Using earplugs or noise-cancelling headphones in noisy environments can help minimize symptoms associated with sound sensitivity and Tullio phenomenon.

Surgical Intervention:

• Canal Plugging: In cases where conservative measures are ineffective or symptoms are severe, surgical repair of the dehiscence may be considered. This typically involves plugging or covering the dehiscent portion of the superior semicircular canal to restore normal fluid dynamics within the inner ear. 

• Canal Resurfacing: Another surgical option is resurfacing the dehiscent canal with bone cement or tissue grafts to reinforce the thinning bone and improve vestibular function. 
• Round Window Reinforcement: In some cases, procedures to reinforce the round window membrane may be performed to reduce the transmission of sound-induced pressure changes to the inner ear, thereby alleviating symptoms.