Sound-induced vertigo, also known as the Tullio phenomenon, is a vestibular disturbance where loud noises or changes in pressure trigger sudden episodes of dizziness. This is a distinct medical issue caused by an underlying structural problem in the inner ear. Understanding this phenomenon requires looking closely at the delicate balance system and how a small defect can fundamentally alter its function.
The Inner Ear Mechanism: Why Sound Causes Dizziness
The inner ear contains two separate, fluid-filled systems: the cochlea for hearing and the semicircular canals for balance. Sound energy enters the inner ear through the oval window and is typically dissipated by the round window. This ensures the vestibular system, which senses head movement, is insulated from sound-induced pressure waves.
The primary cause of sound-induced vertigo is Superior Semicircular Canal Dehiscence (SSCD). This condition involves a thinning or complete absence of the bone covering the superior semicircular canal. This bony defect creates an abnormal opening into the cranial cavity, acting as a third mobile “window” in the inner ear system.
This “third window” disrupts the closed hydraulic circuit of the inner ear fluid. When sound waves or pressure changes enter, the pressure is shunted through this new pathway in the superior canal instead of dissipating normally.
The abnormal pressure transmission causes the endolymph fluid within the semicircular canal to flow in response to sound. This movement incorrectly stimulates the hair cells, the sensory receptors within the balance organ. The brain interprets this fluid motion as real head movement, triggering the sensation of vertigo.
Recognizing the Signs and Triggers
Patients typically report true rotational vertigo—a false sensation of spinning—rather than lightheadedness or unsteadiness. This dizziness is brief but intense, lasting only as long as the sound or pressure stimulus is present. The specific eye movements, called nystagmus, that accompany the vertigo often align with the plane of the affected superior semicircular canal.
The most prominent triggers are auditory, including loud noises, high-pitched sounds, or specific musical notes. Patients may also find that their own voice or the sound of chewing triggers the vertigo, which is a form of hyperacusis.
Symptoms are also provoked by pressure changes that affect the inner ear fluid. Non-auditory triggers include:
- Straining, coughing, sneezing, or bearing down during physical activity.
- Pressure changes in the middle ear, such as those caused by nose-blowing or changes in altitude.
Another common symptom is oscillopsia, the illusion that stationary objects are moving back and forth during head movements. Since the dehiscence can affect hearing, some patients report autophony, an abnormally loud hearing of their own internal body sounds, such as their heartbeat or voice.
Medical Confirmation and Treatment Options
Diagnosis begins with clinical observation to confirm the Tullio phenomenon, where a loud sound provokes visible eye movement (nystagmus) and vertigo. Specialized testing confirms the inner ear’s hypersensitivity to sound. Vestibular Evoked Myogenic Potentials (VEMP) testing is a non-invasive procedure that measures muscle reflexes triggered by loud sounds.
In patients with SSCD, VEMP tests often show an abnormal response, such as a lower threshold or larger amplitude, indicating over-sensitive balance organs. This physiological finding is confirmed with high-resolution Computed Tomography (CT) scans of the temporal bone. The CT scan visualizes the precise bony defect, confirming the absence of bone over the superior semicircular canal.
For those with mild symptoms, conservative management is recommended, involving avoidance of the specific loud sounds and pressure-related triggers that provoke vertigo.
For patients whose quality of life is severely impaired, surgical intervention is an option. The goal of surgery is to permanently seal the third window defect through a procedure called canal plugging or resurfacing. By restoring the normal closed hydraulic system of the inner ear, this procedure is highly effective in eliminating sound- and pressure-induced vertigo.