Vertigo and the Inner Ear

By Dr. Prateek Porwal, ENT Surgeon & Vestibular Specialist | PRIME ENT CENTER, Hardoi UP
Last Updated: February 2026 | VAI Budapest 2025 Award Recipient

Understanding why you get vertigo requires understanding the inner ear—one of the most remarkable organs in your body. It’s the size of a pea, contains over 3,000 hair cells, and manages the incredibly complex task of detecting motion, gravity, and position. When something goes wrong in this tiny structure, the results are profound. Let me explain how this remarkable system works, what can go wrong, and why certain conditions cause the symptoms you experience.

The Inner Ear Anatomy: A Remarkably Complex System

Your inner ear has two main functions: hearing (cochlea) and balance (vestibular system). They’re closely related anatomically and sometimes affected together. The vestibular system has several components:

The Semicircular Canals

Three fluid-filled loops oriented in different planes—horizontal, anterior (vertical forward), and posterior (vertical backward). They detect rotational movements of the head. When you turn your head, the fluid (endolymph) inside the semicircular canals moves, bending hair cells and sending signals to the brain about rotation.

How they work: Each canal has an ampulla—a widened section containing a sensory organ called the crista. The crista has hair cells topped with cilia (tiny hairs). When head rotates, endolymph lags behind due to inertia, bending the cilia. Bent cilia depolarize hair cells, which fire nerve signals to the brain indicating head rotation direction and speed.

Why this is clever: The canals are arranged at right angles to each other. This allows detection of rotation in all three planes—pitch (nodding), roll (tilting), yaw (turning).

The Otolith Organs (Utricle and Saccule)

Located in the vestibule between the semicircular canals and cochlea, these structures detect linear acceleration and gravity. The utricle senses horizontal acceleration; the saccule senses vertical acceleration and gravity.

How they work: Each contains a sensory area called the macula with hair cells similar to semicircular canals. Embedded in a gelatinous layer above the hair cells are tiny crystals called otoconia (calcium carbonate crystals). When you accelerate horizontally (car speeding up), gravity acts on the otoconia, bending the cilia beneath them. This signals the brain about direction and magnitude of acceleration.

Otoconia are crucial for balance: They’re the key players in BPPV. When dislodged from normal position (from head trauma, age, or sometimes spontaneously), they migrate into the semicircular canals. This causes the severe vertigo of BPPV because the canals become hypersensitive to head movements—detecting gravity as if the head is moving in impossible ways.

The Three Fluids: Endolymph, Perilymph, and Cerebrospinal Fluid

Endolymph: The fluid inside the inner ear membranes (inside the cochlear duct, inside semicircular canals, inside utricle/saccule). High in potassium, low in sodium. Generated by stria vascularis. Crucial for hair cell function—maintains electrical gradient necessary for hair cell signaling.

Perilymph: Fluid surrounding inner ear structures, between the membranous labyrinth and bony labyrinth. Similar to cerebrospinal fluid, surrounds the vestibular nerve.

Cerebrospinal fluid (CSF): Surrounds brain and spinal cord, includes the inner ear region.

Why this matters: In Meniere’s disease, endolymph volume increases abnormally (endolymphatic hydrops). Increased pressure in the inner ear causes hearing loss, tinnitus, vertigo, ear fullness. Pressure cycles explain episodic nature of Meniere’s attacks.

How the Balance System Detects Motion and Position

The Vestibulo-Ocular Reflex (VOR)

This is the system that keeps your vision stable when your head moves. When you turn your head right, your eyes automatically turn left (via VOR) so your eyes stay focused on the target. Try this: hold your finger at arm’s length and focus on it. Turn your head rapidly side to side. Your eyes automatically track your finger—that’s VOR.

How it works: Semicircular canals sense head rotation. Vestibular nerve sends signals to brainstem nuclei. Brainstem immediately sends signals to eye muscles to move eyes opposite to head movement. The reflex is fast (milliseconds latency)—faster than conscious thought.

When damaged: Vestibular nerve inflammation (vestibular neuritis) damages this reflex. Head movements no longer keep eyes stable. Vision becomes blurry with head movement (oscillopsia). Patient sees the world jiggling when they move their head.

Vestibulospinal Reflex

Vestibular signals also go to spinal cord, controlling muscles that maintain posture and balance. When you’re on a ship and it rocks, your vestibular system automatically activates leg muscles to maintain balance. This happens unconsciously.

Vestibulo-Collic Reflex

Signals to neck muscles help stabilize head position. Works with VOR and vestibulospinal reflex to maintain overall balance and stability.

Hair Cells: The Key Sensory Cells

Both cochlea and vestibular system use hair cells—specialized sensory neurons. Humans are born with roughly 16,000 cochlear hair cells (for hearing) and 3,600 vestibular hair cells (for balance). This is a fixed number.

Critical point: Hair cells don’t regenerate in humans. Damage is permanent. Loss of hair cells means loss of function in that area. This is why sudden sensorineural hearing loss is serious—those hair cells are gone forever. It’s also why vestibular rehabilitation is so important—you can’t repair damaged hair cells, but your brain can learn to compensate through rehabilitation.

(Some amphibians and birds can regenerate hair cells, which is why researchers are investigating ways to trigger this in humans, but currently it doesn’t happen naturally in our species.)

Hair Cell Structure and Function

Each hair cell has:

• A kinocilium (single large cilium)
• Stereocilia (ranked rows of smaller cilia)
• Synaptic connections to vestibular nerve

How they sense motion: When stereocilia bend toward kinocilium, the hair cell depolarizes (becomes more electrically positive), increasing firing rate. When they bend away from kinocilium, it hyperpolarizes (becomes more negative), decreasing firing rate. This directional sensitivity allows the brain to determine motion direction and magnitude.

What Goes Wrong: Common Inner Ear Problems and Their Mechanisms

BPPV (Benign Paroxysmal Positional Vertigo)

What happens: Otoconia (crystals) dislodge from their normal position in the utricle/saccule and migrate into a semicircular canal (usually posterior canal, sometimes horizontal or anterior). When the head moves, gravity acts on the loose crystals, moving them within the canal, bending hair cells violently.

Why it causes vertigo: The brain interprets the hair cell signals as indicating head movement in an impossible direction. This sensory mismatch causes strong vertigo and nystagmus. The dislodged crystals essentially create a false signal telling the brain the head is rotating when it’s not.

Why it’s brief: The loose crystals eventually re-settle or get reabsorbed. Once they’re no longer moving, the signal stops and vertigo stops.

Why repositioning maneuvers work: The Epley maneuver and other repositioning maneuvers use gravity to move the loose crystals back into the utricle/saccule where they belong. Once there, they no longer cause problems.

Viral Infection of the Vestibular Nerve (Vestibular Neuritis)

What happens: Virus (typically herpes simplex, varicella zoster, or other upper respiratory viruses) infects the vestibular nerve, causing inflammation and sometimes temporary damage to nerve fibers. Hair cells themselves are usually intact but can’t communicate with the brain.

Why it causes severe vertigo: Sudden loss of vestibular input on one side creates profound sensory mismatch. Brain receives signals from one healthy vestibular nerve and one inflamed/non-functional nerve. This asymmetry causes strong vertigo, nausea, nystagmus.

Why it improves over time: Inflammation resolves. Nerve recovers. If hair cells weren’t permanently damaged, function returns. Brain also adapts and compensates for residual imbalance through neuroplasticity (this is what VRT facilitates).

Labyrinthitis (Inner Ear Inflammation/Infection)

Differs from vestibular neuritis: Infection affects not just the nerve but the inner ear structures themselves (semicircular canals, utricle, saccule, even cochlea). So patient has both vertigo AND hearing loss, whereas vestibular neuritis typically spares hearing.

Mechanism: Viral or bacterial infection causes swelling and hair cell damage. Results are similar to vestibular neuritis (sudden vertigo, nausea) but recovery may be slower because actual hair cells may be permanently damaged.

Meniere’s Disease (Endolymphatic Hydrops)

What happens: Abnormal accumulation of endolymph (inner ear fluid). Pressure builds in the inner ear. The exact cause is unknown—may involve immune system dysfunction, genetic predisposition, salt metabolism abnormalities, or viral triggers.

Mechanism of symptoms: High pressure distorts the membranous labyrinth, bending hair cells. Builds to critical pressure, then ruptures, causing acute vertigo episode. Fluid slowly reabsorbs, pressure normalizes, vertigo resolves. Then pressure builds again—hence episodic nature.

Why hearing loss develops: Pressure fluctuations initially cause temporary hearing loss (returns between episodes). With repeated episodes, permanent hair cell damage occurs, permanent hearing loss results. Early treatment (diet, diuretics, betahistine) aims to prevent permanent damage.

Why tinnitus and ear fullness occur: Hair cell irritation causes tinnitus. Fluid pressure causes sensation of fullness in affected ear.

Ototoxicity (Drug-Induced Inner Ear Damage)

Mechanisms: Some drugs directly damage hair cells. Most common: aminoglycoside antibiotics (gentamicin, tobramycin), some chemotherapy drugs (cisplatin), high-dose NSAIDs, loop diuretics (especially at high doses or combined with aminoglycosides).

Hair cells affected: Vestibular hair cells may be damaged, causing chronic balance problems. Cochlear hair cells may be damaged, causing hearing loss.

Why it’s irreversible: Hair cells are permanently lost. No regeneration in humans. Once damaged, function is gone forever.

Pressure Regulation and Perilymphatic Fistula

The inner ear has a delicate pressure-regulation system. A small opening in the bony labyrinth (the cochlear aqueduct) allows slow exchange between perilymph and CSF. This maintains pressure balance.

What is perilymphatic fistula? Abnormal opening in the oval window or round window (membranes separating middle and inner ear) allows perilymph to leak into the middle ear. This causes fluctuating hearing loss, vertigo, unsteadiness.

Common causes: Head trauma, barotrauma (diving, pressure exposure), straining (Valsalva maneuver), heavy lifting, coughing, sometimes spontaneous. High-risk sports (scuba diving, skydiving) can cause fistulas.

Diagnosis: Suspicion based on history (trauma followed by vertigo/hearing loss). MRI or imaging might show fluid in middle ear. Sometimes diagnosed during surgery when observing fluid around fistula site.

Treatment: Bed rest and head elevation initially may allow fistula to seal naturally. If persistent, surgery (patching the fistula) needed. Avoid Valsalva, straining, diving until fistula heals.

Why Head Trauma Is So Dangerous for Inner Ear Function

The inner ear sits in the temporal bone. Head trauma can cause:

• Otoconia dislodgement: Causes BPPV (discussed above)
• Haircell damage: Direct trauma kills hair cells. Permanent loss of vestibular or hearing function
• Perilymphatic fistula: Rupture of membranes between inner and middle ear
• Temporal bone fracture: Can directly disrupt inner ear structures or create fistula
• Whiplash-type injury: Inertial effects can damage hair cells without obvious trauma

This is why anyone with significant head injury should be evaluated for inner ear damage. Early detection can prevent permanent disability.

The Three-Semicircular-Canal System: How It Provides 3D Balance

The three canals—horizontal, anterior, posterior—are oriented at right angles to each other. This allows detection of rotation in all three planes:

• Horizontal canal: Detects yaw (turning left/right)
• Anterior canal: Detects pitch (nodding forward/backward)
• Posterior canal: Detects roll (tilting sideways)

When you turn your head in any direction, at least one canal detects the rotation. Most natural movements involve combinations—turning while nodding, for example—so multiple canals provide redundant information.

Why BPPV is often in posterior canal: The posterior canal is most dependent, so loose crystals naturally settle there. This is why posterior canal BPPV is most common and why the Dix-Hallpike test (which targets the posterior canal) is diagnostic.

Frequently Asked Questions About Inner Ear Anatomy and Function

Can hair cells regenerate if damaged?

Not in adult humans. We’re born with a fixed number of vestibular hair cells (about 3,600) and cochlear hair cells (about 16,000). Once lost to age, noise, infection, or trauma, they don’t come back. This is why preventing damage (hearing protection, avoiding ototoxic drugs) and rehabilitation (to maximize remaining function) are important.

What are those crystals in BPPV exactly?

Otoconia—tiny calcium carbonate crystals normally embedded in the gelatinous layer covering hair cells in the utricle and saccule. Their weight allows these organs to detect gravity and linear acceleration. When dislodged, they migrate into semicircular canals where they shouldn’t be, causing BPPV.

Why does my ear feel full with vertigo?

Sensation of fullness often indicates increased pressure in the inner ear (as in Meniere’s disease) or fluid accumulation (labyrinthitis). The inner ear space is small and rigid, so even small fluid changes cause pressure sensation. This is different from ear fullness from upper respiratory infection, which is middle ear pressure.

Can my inner ear heal after infection?

Depends on the infection and what’s damaged. Vestibular neuritis (nerve inflammation) often heals and function recovers, especially if inflammation wasn’t severe. Labyrinthitis (inner ear infection affecting structures) may cause permanent hair cell damage—function doesn’t fully recover. Rehabilitation helps maximize remaining function.

How important is the semicircular canal fluid?

Endolymph is crucial. It provides the medium in which hair cells detect motion. Its chemical composition (high potassium) maintains the electrical gradient necessary for hair cell signaling. Abnormal endolymph volume or pressure (Meniere’s disease) severely disrupts function.

Can I permanently damage my inner ear with loud noise?

Yes. Noise above 85 decibels for prolonged periods damages cochlear hair cells irreversibly. Hearing loss results and is permanent. Vestibular hair cells are somewhat more resistant but can be damaged by very intense noise. Hearing protection (earplugs at concerts, headphone volume limits, ear protection in loud workplaces) prevents permanent damage.