Superior canal dehiscence is a gap in the bone over one of the inner ear's balance canals that can cause pulsatile tinnitus, hearing your own body sounds, and dizziness triggered by loud noise or straining; surgery can repair it.
The syndrome (SCDS) was first reported by Lloyd Minor and colleagues in 1998. It is rare — affecting an estimated 0.7% of people, based on imaging studies — but it produces a symptom pattern distinctive enough that it's worth knowing about, since the symptoms are easy to misattribute to something else entirely.
What is happening in the ear
Normally, the inner ear's fluid-filled canals are fully enclosed in bone. In SCDS, a thin section of bone over the superior semicircular canal — one of the balance structures — is missing or abnormally thin, creating what researchers call a "third window": an unintended additional pathway for sound and pressure to affect the inner ear, alongside the two normal windows sound is supposed to travel through. That extra pathway is what produces the syndrome's unusual symptoms.
The distinctive symptom pattern
What sets SCDS apart from more common tinnitus causes is a specific cluster of symptoms tied to the "third window" mechanism:
- Sound-induced vertigo (called the Tullio phenomenon) — dizziness or a spinning sensation triggered specifically by loud sounds
- Pressure-induced vertigo — triggered by straining, coughing, sneezing, or changes in ear pressure
- Autophony — hearing your own voice as unusually loud, echoing, or distorted inside your head (also the main symptom of a patulous eustachian tube, a different condition)
- Hearing internal body sounds — your own heartbeat, footsteps, bowel sounds, or even your eye movements, at a volume that seems impossible until you learn about this condition specifically
- Pulsatile tinnitus and general aural fullness
- Often, low-frequency hearing loss and hyperacusis on the affected side
Not everyone with SCDS has every symptom, and some cases are found incidentally on imaging without significant symptoms at all — but the specific combination of sound- or pressure-triggered vertigo alongside hearing internal body sounds is distinctive enough that most other tinnitus causes wouldn't produce it.
SCDS is the best-known member of a family. A perilymph fistula is the other one worth knowing: a leak rather than a hole in the bone, but the same underlying problem of an inner ear that has acquired an opening it was not built with. It produces the same pressure sensitivity, and one of the causes the reviews list for it is otic capsule dehiscence — which is what SCDS is.
Why this one is easy to miss
Because SCDS symptoms overlap with several other inner ear conditions — including Ménière's disease and general pulsatile tinnitus — and because "I can hear my own eyeballs move" sounds implausible even to people experiencing it, this condition often goes undiagnosed for years, sometimes described in case reports as a multi-year history before an accurate diagnosis was reached. Symptoms are also frequently worse during upper respiratory infections, which can further muddy the picture if it's mistaken for a recurring ear infection.
How it's diagnosed
Diagnosis relies on a combination of the specific symptom pattern, a clinical exam finding called nystagmus (a distinctive eye-movement response to loud sound or pressure changes), vestibular testing (VEMP), and confirmation with high-resolution CT imaging of the temporal bone, which can directly visualize the bony gap.
Treatment
Mild cases without significantly disabling symptoms are often simply monitored rather than treated. For more severe, disruptive symptoms, surgical repair of the bony defect (plugging or resurfacing the dehiscence) is the definitive treatment and is generally reserved for cases where symptoms significantly affect daily life, given that it's a more involved procedure than most tinnitus treatments.
When to consider it
If your tinnitus specifically comes with sound- or pressure-triggered dizziness, unusually loud perception of your own voice or bodily sounds, or vertigo triggered by straining or loud noises, that combination is worth describing precisely to an ENT or neurotologist — it's a specific enough pattern that naming it accurately can meaningfully speed up getting the right diagnosis. It is also worth naming because SCDS is one of the structural causes on the short list of tinnitus that can be cured — repairable in selected cases, against a background where the honest answer for ordinary chronic tinnitus is that it is managed rather than resolved.