Superior canal dehiscence syndrome

Superior canal dehiscence syndrome (SCDS) symptoms can vary significantly and typically appear in middle age, affecting men and women equally. Symptoms often progress slowly but may worsen suddenly after head trauma.

The abnormal opening between the inner ear and the brain cavity alters the whole inner ear function. The hearing organ (cochlea) becomes less responsive to external sounds, resulting in hearing loss and aural fullness*.

At the same time the cochlea becomes overly sensitive to internal body sounds (autophony), such as one’s voice, pulse, steps or even eye movement. The balance organs capacity to detect head movements are impaired (resulting in chronic dizziness), becomes hypersensitive to intense sounds (sound-evoked vertigo) and pressure changes (pressure-evoked vertigo)

Symptoms of autophony can ultimately affect sleep quality and interfere with social interaction. Chronic dizziness may lead to a constant elevated mental effort in managing daily activities, and sound and pressure evoked vertigo can induce social avoidance.

Diagnosis is challenging and therefore often delayed. At the time of diagnosis, SCDS is unfortunately often already complicated by stress symptoms and mental fatigue.

SCDS in children is even more rare and often associated with inner ear malformations.

*Aural fullness refers to a sensation of pressure, blockage, or fullness in the ear. It can feel like the sensation experienced during altitude changes, like when ascending in an airplane or diving underwater.

Superior canal dehiscence syndrome (SCDS) diagnostics criteria include:

• Symptoms, such as pressure- or sound-induced vertigo and/or autophony.
• Clinical findings, including:
  - Hearing test with pathologically low bone thresholds in the low frequencies.
  - Hypersensitivity of the balance organ to sound or vibrations, as demonstrated by vestibular evoked myogenic potentials (VEMP).
  - Presence of sound- or pressure-induced eye movements.
• Confirmation of bony dehiscence through radiological imaging.

Counseling and clinical support are provided to care takers and patients. In cases where symptoms are disabling, we offer surgery.

Surgery is particularly successful in addressing symptoms of autophony and pulsatile tinnitus. It has a favorable effect on dizziness and stops sound and pressure induced vertigo. However, some patients may experience residual aural fullness or hearing loss a few weeks after the procedure. Approximately 10% of patients experience permanent hearing reduction on the operated side, and rare cases of complete hearing loss have been reported.

At Karolinska, the preferred choice of surgical treatment is the transmastoid approach, which involves accessing the dehiscence via the bone behind the ear. The dehiscence is then corrected either by capping (covering the bone opening) or plugging (blocking the affected canal). We prioritize capping to preserve canal function.

The surgery is performed under general anesthesia and typically takes 2 hours. Post-surgical dizziness is common but usually resolves within a few weeks with physiotherapy.

Our team of medical audiologists and surgeons provides a complete battery of modern SCDS clinical testing defining the clinical picture in detail. An experienced team of neuroradiologists support in diagnosis and surgery planning, and the medical team provides a first meeting with the patients, supporting them with counseling, surgery decision making and clinical follow up before and after surgery. Every step of the decision-making process is based on the last clinical evidence.

As a reference center for SCDS diagnostics and surgery, we are committed to advancing patient care through the development of innovative diagnostic techniques and evidence-based practices.