Do loud noises make you dizzy?
Can you hear your own voice, footsteps, heartbeat or even your eyes moving unusually loudly inside your head?
Perhaps coughing, sneezing, straining or changes in pressure cause a sudden sensation of vertigo or make the world appear to move.
These are some of the unusual symptoms that can occur with Superior Semicircular Canal Dehiscence Syndrome (SCDS).
It is an important condition to recognise because its symptoms can overlap with more common vestibular disorders such as BPPV, Vestibular Migraine, Ménière’s Disease and Persistent Postural-Perceptual Dizziness (PPPD).
However, SCDS has some particularly distinctive features—especially sound-induced dizziness, pressure-induced dizziness and unusually loud perception of internally generated sounds.
Importantly, finding a dehiscence on a scan does not automatically mean that someone has Superior Canal Dehiscence Syndrome. Diagnosis requires the patient’s symptoms, physiological testing and imaging to fit together.
What are the semicircular canals?
The inner ear contains the cochlea, which is primarily responsible for hearing, and the vestibular system, which helps control balance and spatial orientation.
Each inner ear contains three semicircular canals:
- Anterior or superior semicircular canal
- Posterior semicircular canal
- Horizontal or lateral semicircular canal
The canals are positioned at different angles and detect rotational movements of the head.
When you turn, tilt or nod your head, fluid movement within the semicircular canals stimulates specialised sensory receptors.
This information travels through the vestibular nerve to the brain, where it is integrated with information from your eyes and body to help maintain balance and stabilise your vision.
The superior semicircular canal is normally completely surrounded by bone.
In Superior Semicircular Canal Dehiscence, part of this bony covering is absent or extremely thin.
What is the “third window” phenomenon?
Understanding the concept of a third mobile window helps explain many of the strange symptoms associated with SCDS.
The normal inner ear essentially has two mobile windows:
- The oval window
- The round window
Sound entering the ear causes movement of fluid within the inner ear between these normal windows.
When there is an opening in the bone overlying the superior semicircular canal, this can effectively create an abnormal third mobile window.
Sound and pressure energy can then be transmitted through the inner ear differently.
This can alter both hearing and vestibular function.
As a result, something that would normally stimulate predominantly the auditory system—such as a loud sound—can abnormally stimulate the vestibular system.
This is why someone with SCDS may become dizzy when they hear a loud noise.
It also helps explain why internal sounds can suddenly seem extraordinarily loud.
What are the symptoms of Superior Canal Dehiscence?
SCDS can produce both vestibular symptoms and auditory symptoms.
Not every patient experiences every symptom, and the severity can vary considerably.
Some people have predominantly auditory symptoms.
Others have predominantly dizziness and imbalance.
Some experience both.
Sound-induced dizziness – the Tullio phenomenon
One of the most characteristic symptoms is dizziness or vertigo caused by sound.
This is known as the Tullio phenomenon.
A person may experience vertigo, disequilibrium or oscillopsia when exposed to particular loud sounds.
Examples may include:
- Loud music
- A barking dog
- Machinery
- Power tools
- Sudden shouting
- Loud traffic
- Musical instruments
- Other intense sounds
The important feature is that the dizziness or visual disturbance is time-locked to the sound.
In other words, the sound occurs and the vestibular symptom occurs with it.
This relationship is an important diagnostic clue.
Pressure-induced dizziness
Changes in pressure can also provoke vestibular symptoms.
A person with SCDS may experience dizziness or oscillopsia with:
- Coughing
- Sneezing
- Straining
- Lifting something heavy
- Performing a Valsalva manoeuvre
- Pressure changes within the ear canal
Again, the close temporal relationship between the pressure stimulus and the dizziness is important.
Someone might describe:
“Every time I cough hard, the room moves.”
or:
“When I strain, my vision jumps.”
This is quite different from the typical presentation of BPPV, where symptoms are provoked by movement of the head relative to gravity.
Autophony – hearing your own voice unusually loudly
One of the more unusual symptoms of SCDS is autophony.
Autophony refers to an abnormal amplification or altered perception of your own voice.
People may describe:
“My voice echoes inside my head.”
“My own voice sounds incredibly loud in one ear.”
“It sounds like I’m talking inside a barrel.”
This can be extremely distracting.
Hearing internal body sounds
Another striking feature of Superior Canal Dehiscence is bone-conduction hyperacusis, where internally generated sounds become unusually audible.
Some patients can hear sounds they had never previously noticed.
These can include:
- Their own footsteps
- Their heartbeat
- Eye movements
- Blinking
- Jaw movements
- Neck movements
- Chewing
- Internal digestive sounds
A patient saying:
“I can hear my eyes moving.”
is unusual enough that SCDS should be considered as part of the differential diagnosis.
Pulsatile tinnitus
SCDS can also cause pulsatile tinnitus.
Unlike typical continuous tinnitus, pulsatile tinnitus is often perceived as a rhythmic sound corresponding with the heartbeat.
Patients may describe hearing:
“whoosh, whoosh, whoosh”
in time with their pulse.
Pulsatile tinnitus has several potential causes, so it requires appropriate medical investigation rather than automatically being attributed to SCDS.
Hearing loss
Some patients with SCDS demonstrate an apparent conductive component to their hearing loss, particularly at lower frequencies.
Interestingly, the middle ear itself may be normal.
This occurs because the third-window effect changes the mechanics of sound transmission through the inner ear.
Audiometry may demonstrate a low-frequency air-bone gap and, in some cases, unusually low or even negative bone-conduction thresholds.
This is one reason SCDS can occasionally resemble a middle-ear conductive hearing disorder.
Aural fullness
Some patients describe pressure or fullness within the affected ear.
However, aural fullness is not specific to SCDS and can occur with numerous other conditions, including Ménière’s Disease, migraine-associated disorders and Eustachian tube dysfunction.
Chronic disequilibrium
Not everyone with SCDS experiences dramatic attacks of spinning vertigo.
Some patients instead report:
- Persistent unsteadiness
- Disequilibrium
- Difficulty walking
- Motion sensitivity
- Reduced confidence with balance
- Visual instability
- Feeling disorientated during movement
These symptoms can be more difficult to distinguish from other vestibular disorders.
Oscillopsia
Oscillopsia is the sensation that the visual environment is moving, bouncing or oscillating when it should be stationary.
In SCDS, sound or pressure can sometimes trigger abnormal activation of the superior semicircular canal and produce eye movements.
The patient may therefore perceive the environment as moving at the same time.
What symptoms particularly make us suspicious of SCDS?
The combination is important.
We become particularly suspicious when someone describes symptoms such as:
“Loud noises make me dizzy.”
“I become dizzy when I cough or strain.”
“I can hear my footsteps booming through my head.”
“My own voice sounds incredibly loud in one ear.”
“I can hear my eyes moving.”
“When there’s a loud noise, my vision jumps.”
“I can hear my heartbeat in my ear.”
These symptoms are quite different from the typical presentation of BPPV or a simple vestibular hypofunction.
The combination is important.
We become particularly suspicious when someone describes symptoms such as:
“Loud noises make me dizzy.”
“I become dizzy when I cough or strain.”
“I can hear my footsteps booming through my head.”
“My own voice sounds incredibly loud in one ear.”
“I can hear my eyes moving.”
“When there’s a loud noise, my vision jumps.”
“I can hear my heartbeat in my ear.”
These symptoms are quite different from the typical presentation of BPPV or a simple vestibular hypofunction.
What are the diagnostic criteria for Superior Canal Dehiscence Syndrome?
This is an extremely important distinction.
A CT scan showing a dehiscence alone is not sufficient to diagnose Superior Canal Dehiscence Syndrome.
According to the Bárány Society consensus diagnostic criteria, diagnosis requires evidence from three categories:
1. Characteristic symptoms
At least one symptom consistent with third-window physiology, such as:
- Bone-conduction hyperacusis
- Sound-induced vertigo and/or oscillopsia
- Pressure-induced vertigo and/or oscillopsia
- Pulsatile tinnitus
2. Physiological evidence of a third window
At least one physiological sign or test supporting abnormal transmission of pressure through the inner ear, including:
- Characteristic eye movements produced by sound or pressure
- Low-frequency negative bone-conduction thresholds on audiometry
- Enhanced Vestibular Evoked Myogenic Potential responses
3. Imaging evidence
A high-resolution CT scan of the temporal bone demonstrating a dehiscence of the superior semicircular canal.
The presentation also needs to be better explained by SCDS than another vestibular disorder.
This distinction prevents patients from being diagnosed purely because a scan happens to show thin or absent bone.
What bedside tests can be performed?
A Vestibular Physiotherapist can perform a detailed vestibular examination to determine whether the symptom pattern is suspicious for SCDS and whether another vestibular disorder may be contributing.
However, bedside testing does not replace audiological testing, VEMP testing and appropriate imaging when SCDS is suspected.
Oculomotor examination
An assessment may initially examine:
- Smooth pursuit
- Saccades
- Gaze holding
- Spontaneous nystagmus
- Visual fixation
- Alignment of the eyes
This provides information about the broader vestibular and neurological examination.
Bedside Head Impulse Test
The Head Impulse Test assesses the Vestibulo-Ocular Reflex.
The patient focuses on a stationary target while the clinician delivers small, rapid head movements.
SCDS does not necessarily produce an abnormal standard bedside Head Impulse Test.
However, the test remains useful because it provides information about semicircular canal function and helps assess for other vestibular disorders.
Positional testing
Dix–Hallpike and Supine Roll testing may be performed to assess for BPPV.
This is important because a patient experiencing positional dizziness may have BPPV rather than SCDS—or potentially more than one vestibular disorder.
BPPV typically produces characteristic positional nystagmus when the affected semicircular canal is stimulated.
In contrast, classic SCDS symptoms are more characteristically provoked by sound and pressure.
Sound-provoked testing
In an appropriate clinical setting, eye movements may be observed while exposing the affected ear to an appropriate auditory stimulus.
In SCDS, sound can provoke nystagmus with eye movements related to the plane of the affected superior semicircular canal.
This provides physiological evidence that sound is abnormally stimulating the vestibular system.
Specialist equipment such as video-oculography or Frenzel goggles may make subtle nystagmus easier to identify.
Sound-provocation testing should be performed carefully and is not simply a matter of exposing someone to unnecessarily loud noise.
Pressure-provoked testing
Changes in middle-ear or intracranial pressure can sometimes provoke characteristic symptoms and eye movements.
Assessment may involve clinically appropriate pressure or Valsalva manoeuvres while observing the eyes.
A positive response may produce dizziness, oscillopsia and/or nystagmus.
Again, these findings need to be interpreted alongside the entire clinical picture.
What is the fistula test?
A fistula-type test involves altering pressure within the external auditory canal while observing for dizziness or nystagmus.
A positive pressure-induced response can support the presence of a third-window phenomenon, although it is not by itself diagnostic of SCDS.
What is VEMP testing?
Vestibular Evoked Myogenic Potential (VEMP) testing is particularly valuable when investigating suspected Superior Canal Dehiscence Syndrome.
VEMPs assess reflex pathways arising from the otolith organs within the vestibular system.
Two commonly used tests are:
Cervical VEMP – cVEMP
cVEMP primarily evaluates a vestibulo-collic reflex involving the saccule and inferior vestibular nerve pathway.
In SCDS, the affected ear commonly demonstrates a lower-than-expected cVEMP threshold.
Essentially, the vestibular system responds to a quieter sound than would normally be expected because the third window alters the mechanics of the inner ear.
Ocular VEMP – oVEMP
oVEMP assesses a vestibulo-ocular reflex pathway, with a major contribution from the utricle and superior vestibular nerve.
SCDS can produce larger-than-expected oVEMP amplitudes.
The combination of an unusually low cVEMP threshold or elevated oVEMP amplitude with characteristic symptoms can substantially increase suspicion of a third-window disorder.
VEMP results must be interpreted using the laboratory’s own normal ranges and alongside audiometry and imaging.
What does an audiogram show?
A comprehensive audiological assessment is an important component of investigating suspected SCDS.
Audiometry may demonstrate:
- A low-frequency air-bone gap
- Very good bone-conduction hearing
- Bone-conduction thresholds below 0 dB HL in some patients
The presence of an apparent conductive hearing loss despite otherwise normal middle-ear function can be an important clue.
This is because the apparent conductive component originates from altered inner-ear mechanics, rather than necessarily being caused by pathology of the tympanic membrane or ossicles.
Audiometry should therefore be interpreted together with tympanometry, acoustic reflex testing, VEMPs and the clinical history.
What scan diagnoses Superior Canal Dehiscence?
The principal imaging investigation is a high-resolution CT scan of the temporal bones.
However, the way the scan is performed and reconstructed matters.
Very thin bone can sometimes appear absent because of limitations in CT resolution. This can potentially create a false impression of dehiscence.
For this reason, high-resolution imaging with very thin slices is preferred.
The Bárány Society consensus recommends CT resolution near 0.2 mm or better where technically available, with images reconstructed in the plane of the superior semicircular canal and orthogonal to it.
These specialised reconstructions are commonly described as:
- Pöschl view – parallel to the superior semicircular canal
- Stenvers view – perpendicular to the canal
This provides a much better assessment than relying solely on routine axial CT images.
Can an MRI diagnose SCDS?
MRI can provide useful information about the inner ear and brain and may be performed when investigating dizziness for other reasons.
However, high-resolution temporal bone CT remains the key imaging investigation for demonstrating the bony dehiscence in the established diagnostic criteria.
MRI may have a role in particular circumstances or in excluding alternative pathology, but imaging needs to be interpreted alongside symptoms and physiological testing.
Why doesn’t a positive CT automatically mean I have SCDS?
This is one of the most important messages in this article.
Some people have thin bone or apparent dehiscence on CT but do not have Superior Canal Dehiscence Syndrome.
SCDS is a clinical syndrome, not simply an imaging finding.
For example, imagine a patient has a CT for an unrelated reason and the report states:
“Possible superior semicircular canal dehiscence.”
But the patient has:
- No sound-induced dizziness
- No pressure-induced dizziness
- No bone-conduction hyperacusis
- No pulsatile tinnitus
- Normal VEMP testing
- No supportive audiological findings
The scan finding alone should not automatically become the explanation for every episode of dizziness they experience.
The symptoms, physiological evidence and imaging should tell the same story.
The diagnosis should make sense across three areas:
Your symptoms + physiological vestibular/audiological findings + high-resolution imaging.
When all three fit together, the diagnosis becomes considerably more meaningful and allows an appropriate management plan to be developed.
The Vertigo Co
If you are experiencing unexplained dizziness, sound- or pressure-induced vertigo, unusual auditory symptoms or persistent balance problems, consider booking a comprehensive Vestibular Physiotherapy assessment with The Vertigo Co.
This article provides general educational information and is not a substitute for individual medical assessment. New sudden hearing loss, severe acute vertigo, new neurological symptoms or other concerning symptoms require prompt medical assessment.
