Superior canal dehiscence

Superior Canal Dehiscence (SCD) is a rare medical condition affecting the inner ear, specifically the bony layer of the superior semicircular canal. This condition is characterized by a thinning or complete absence of the bone overlying the superior semicircular canal of the vestibular system. Patients with SCD may experience a variety of symptoms including vertigo, hearing loss, tinnitus (ringing in the ears), and autophony (hearing one's own bodily sounds, such as eye movements or heartbeat, loudly).

Causes

The exact cause of Superior Canal Dehiscence is not fully understood. It is believed to be due to a developmental anomaly where the bone overlying the superior semicircular canal fails to fully develop. In some cases, it may be acquired later in life due to trauma, infection, or other conditions that lead to bone erosion.

Symptoms

Patients with SCD may report a range of auditory and vestibular symptoms, which can significantly impact their quality of life. Common symptoms include:

• Vertigo and dizziness, often triggered by loud noises (Tullio phenomenon) or by changes in pressure (such as coughing, sneezing, or straining).
• Hearing loss, particularly in the affected ear.
• Tinnitus, which may be pulsatile or constant.
• Autophony, where internal sounds such as one's own voice, breathing, or heartbeat are heard loudly in the ear.
• Sensitivity to sound (hyperacusis), where normal environmental sounds are perceived as uncomfortably loud.

Diagnosis

Diagnosis of Superior Canal Dehiscence involves a combination of clinical evaluation, hearing tests, and imaging studies. High-resolution Computed Tomography (CT) scans of the temporal bone are the gold standard for visualizing the dehiscence. Vestibular testing, including Vestibular Evoked Myogenic Potentials (VEMP), can also support the diagnosis by demonstrating heightened sensitivity of the vestibular system.

Treatment

Treatment options for SCD vary depending on the severity of symptoms and the patient's overall health. Conservative management may include avoidance of activities that trigger symptoms and the use of medications to control dizziness and nausea. In cases where symptoms are severe and significantly impact the patient's quality of life, surgical intervention may be considered. Surgical options include:

• Middle fossa craniotomy, where the dehiscence is repaired through an opening in the skull.
• Transmastoid approach, where the dehiscence is accessed through the mastoid bone behind the ear.

Prognosis

The prognosis for patients with Superior Canal Dehiscence who undergo surgical treatment is generally good, with many experiencing significant improvement in symptoms. However, as with any surgery, there are risks involved, and outcomes can vary from person to person.

See Also

• Vestibular system
• Vertigo
• Hearing loss
• Tinnitus