TERM

DEFINITION

Ablation

Detachment or removal, as of an organ or part, especially by surgery. Also, destruction of function, as by a chemical.

Aminoglycoside

A class of antibiotic drugs often used for selective ablation of the vestibular endorgan. Examples are streptomycin and gentamicin; both have their main toxic effects on vestibular hair cells and dark cells, and to a lesser extent, on cochlear hair cells.

Ampulla

The dilated or expanded end of each of the three membranous semicircular ducts of the inner ear.

Ataxia

Impaired coordination, especially in gait.

Audiometric assessment (AA)

Overall assessment of hearing function. Includes the threshold of hearing at different frequencies of the hearing spectrum, both by air conduction and bone conduction, which thereby analyzes the contribution of the middle vs. inner ear structures. Also, includes tests of the ability to discriminate speech.

Auditory

Refers to the sense of hearing.

Auditory brainstem response audiometry (ABR)

Method for computer analysis of retrocochlear (neural pathways between the cochlea and the brain) function by means of electrodes placed on the head and ears. Specifically, to detect and localize a lesion affecting the auditory portion of the eighth nerve or its higher pathways.

Automated positioning

Use of an automated apparatus to position the patient. Used for analysis of positional nystagmus and for treatment of various forms of vestibular lithiasis.

Automated repositioning

Treatment of canalithiasis (BPPV) or cupulolithiasis by repositioning of abnormal labyrinthine densities with an automated positioning apparatus. Ideally this is accomplished with equipment that has a 360-degree range in any axis and an IR video system to monitor and record nystagmus during the procedure. This is the most effective method for treating difficult cases of BPPV and variants.

Benign paroxysmal positional vertigo (BPPV)

A condition in which violent, brief (seconds) episodes of spinning vertigo are provoked by moving the head into certain positions. The mechanism is abnormal densities, mainly displaced otoconia from the utricle, which collect in a posterior semicircular canal, where they shift position when the head is tilted. The diagnosis is made by observing typical nystagmus after the Hallpike maneuver. Treatment: the offending loose densities can be moved out of the semicircular canal with the Epley (canalith repositioning) maneuvers, thus controlling the symptoms.

BPPV variant

Vertigo due to any other form of vestibular lithiasis besides typical posterior canal canalithiasis.

Biphasic nystagmus

Involuntary eye movement occurring with a fast phase in one direction and a slow phase in the opposite direction. Also called "jerk nystagmus". It is generated in the vestibular system. By convention, the nystagmus is designated by the direction of its fast phase.

Brainstem

Composed of the pons, the medulla oblongata, and the nuclei of the cranial nerves. It receives information relating to balance and initiates muscle adjustments that enable one to keep their balance and to maintain clear vision as they move.

Caloric test

Method for assessing the relative function of the horizontal semicircular canals by means of warm or cool stimulus presented to external ear canals. Does not assess function of the otolith organs (utricle and saccule).

Canalith

Free-floating density in a semicircular canal. Can be displaced otoconia, calcified masses or layering of endolymph.

Canalithiasis

A condition in which loose densities in a semicircular canal produce nystagmus and vertigo when a critical provocative position of the head is assumed. The symptoms generated are called benign paroxysmal positional vertigo (BPPV).

Canalith Repositioning

Procedure for the treatment of canalithiasis (BPPV) through maneuvers designed to induce migration of free particles out of the semicircular canals, assisted by concurrent observation of the nystagmus being produced by the migrating particles. Also known as the "Epley Maneuvers".

Central compensation

The tendency of the central nervous system to respond to impaired function or defect by a change in its activity that counterbalances the impairment or defect.

Central nervous system (CNS)

The part of the nervous system that integrates sensory input and motor output; made up of the brain and spinal cord.

Cerebellum

Muscle coordination center of the brain.

Cerebrum

The main part or mass of the brain. Consists of two equal portions, known as hemispheres.

Cervical vertigo syndrome (Post-traumatic)

A theoretical condition unsupported by any study. There is no reliable clinical test for the syndrome, no typical time course for the condition has been established, and treatment directed at the neck has not proven to be generally effective. (The symptom complex is identical to the "inner ear concussion syndrome." Most cases assigned the diagnosis of "cervical vertigo" actually have the sequella of inner ear concussion.)

"Chronic disabling vertigo"

A term used by a small group of physicians to describe a condition supposedly resulting from vascular compression of the eighth nerve. Treatment by intracranial vascular decompression was advocated. In the few published cases pegged with CDV and surgerized, the symptoms have been strikingly similar to those of severe canalithiasis (BPPV); further, they were not given a preliminary trial of canalith repositioning. Therefore, it is likely that most cases, if not all, actually had canalithiasis.

Cochlea

The snail-shaped portion of the inner ear which is concerned with hearing.

Cochlear duct

A canal, triangular in cross section, situated in the cochlea between the scala tympani (lower canal of the cochlea) and scala vestibuli (upper canal of the cochlea). It is filled with a fluid called endolymph, and it contains the organ of Corti, the ultimate mechanism that transforms sound into nerve impulses that are transmitted to the brain by the cochlear nerve for interpretation.

Cochlear nerve

One of the two components of the acoustic (eighth) nerve. The other part is the vestibular nerve. The cochlear nerve is concerned with hearing.

Computerized dynamic posturography (CDP)

A test that obtains a computer analysis of the overall balance function, and identifies those sensory or motor systems that are contributing to imbalance because of a deficit or improper utilization. The test subject stands on a moveable force platform that has a moveable visual background.

Concussion

A sudden and violent jarring or shaking (result of high g-forces), resulting in injury to soft tissue, specifically in the CNS or inner ear. Does not necessarily require a direct traumatic blow.

Corticosteroid

A steroidal anti-inflammatory drug. Dexamethasone is an example.

Cupula, cupulae

A fine striated membranous structure covering the hair cells of the crista of the ampulla of each semicircular canal. The cupulae are deflected by inertial movement of fluid in the semicircular canal, whereby the canals are mechano-receptors of angular acceleration in the specific plane of the canal.

(Heavy cupula)

A condition created when a cupula is weighted by densities. The nystagmus produced is slow in onset and persistent.

Dark cells

Pigmented cells in the inner ear that secrete endolymph.

Eighth nerve

Nerve that carries impulses concerned with balance and hearing between the inner ear and the brain.

Electrocochleog-raphy (ECoG)

A test to analyze the overall cochlear function and the relationship between the cochlear fluids, especially to identify endolymphatic hydrops. Uses sound stimuli and electrical potentials detected via an electrode in the EAC to do a computer analysis of the cochlear response.

Electronystagmog-raphy (ENG)

Battery of tests using electrodes placed around the eye to monitor eye movement. Assesses the vestibulo-ocular reflex portion of the vestibular system, including the oculomotor function through introduction of various stimuli. Typical battery includes caloric, gaze, positional and oculomotor stimuli. Will also assess the ability of the CNS to suppress nystagmus during optic fixation. Does not assess function of the otolith organs (utricle and saccule).

Endolymph

The fluid contained within the membranous labyrinth.

Endolymphatic duct

A duct which arises from the saccule and utricle and ends in the endolymphatic sac. Believed by some to have an important role in the production of endolymphatic hydrops.

Endolymphatic sac

The dilated blind end of the endolymphatic duct.

Endolymphatic hydrops (EH)

Abnormal accumulation of endolymph fluid which results in a dilatation of the membranous labyrinth. It can cause the symptoms of Meniere’s disease.

Endolymphatic shunt procedure

Surgery to permanently drain the endolymphatic sac via a shunt tube either into the middle ear space or the subarachnoid space.

Epley Maneuvers

A procedure for correcting the symptoms of BPPV (canalithiasis) through maneuvers designed to induce migration of free particles out of the semicircular canals, assisted by concurrent observation of induced nystagmus. Also known as "canalith repositioning" or, when used more broadly to treat the various manifestations of vestibular lithiasis, the treatment is called "particle repositioning".

External auditory canal (EAC)

Ear canal external to the tympanic membrane.

Fistula

An abnormally formed canal or passage running between two organs or spaces within the body, or between the surface of the body and an internal organ or a space inside the body.

"Fistula test"

This term originally described a test involving the application of positive and/or negative pressure to an EAC for detecting a softening in a bony erosion (softening) of a semicircular canal as indicated by a severe induced nystagmus. In the 1970’s, the term "fistula test" began to be misused to denote the Hennebert test, thus incorrectly inferring that the test is diagnostic of a perilymph fistula.

Glycerol test

A test that indicates the presence of endolymphatic hydrops (EH). Ingestion of glycerol solution causes rapid absorption of fluid from endolymphatic system. A positive test is indicated by ± 10 db change in hearing at any frequency or a 12% improvement in speech discrimination.

Hallpike test, Hallpike maneuver

A physical maneuver that rotates the posterior semicircular canal in the plane of gravity during which the eyes are observed for a characteristic pattern of movement (typical nystagmus) diagnostic of BPPV. From a sitting position, the patient is moved quickly to a supine position with the head over the end of the table and turned 45 degrees to the side of the ear being tested.

Hennebert phenomenon

The production of induced eye movement, vegetative symptoms (nausea, vomiting, paleness, etc.) and postural instability in response to air pressure applied to an external auditory canal with an intact tympanic membrane.

Hennebert sign

Observation of induced eye movement in response to air pressure applied to an external auditory canal with an intact tympanic membrane. The induction of biphasic nystagmus is consistent with a bony defect in the semicircular canal in the plane of the nystagmus. Induction of static torsion of the eyeball proportional to the pressure applied (positive or negative) is consistent with otolithic membrane involvement, most likely by vestibular fibrosis.

Hennebert symptom

Subjective sensation of motion, nausea or imbalance in response to air pressure applied to an external auditory canal with an intact tympanic membrane.

Application of air pressure, positive and/or negative, to an external auditory canal (EAC) with an intact tympanic membrane, usually with the patient seated. Simultaneously the eyes are observed for nystagmus and the patient reports any sensation of movement, nausea, imbalance, etc. Any positive sign or symptom is abnormal, but the interpretation of the abnormality depends upon the characteristics of that sign or symptom. (See Hennebert sign, Hennebert symptom) NOTE: This test is also frequently called a "fistula test" in relation to a perilymph fistula. This is a misinterpretation because, although a positive sign or symptom is suggestive of the presence of a perilymph fistula, it is not diagnostic of one. Thus, the use of the term "fistula test" is confusing, and should be avoided.

Hydrops

An abnormal accumulation of fluid in an organ, a body cavity, or in a tissue.

Hyperactive labyrinthine dysfunction

The condition in which a labyrinth is in an abnormally sensitive state with respect to certain stimuli and/or inputs. More appropriately called "irritable labyrinth", in that the labyrinth becomes easily "irritated" by non-vestibular stimuli such as sound or pressure change.

(IR Videonystag-mography)

Use of video camera in apparent darkness (with infrared light) to record eye movement for recording and analysis. This test method is far superior to eye electrode ENG, because it is more sensitive, less affected by artifact, and because it provides assessment of any torsional component of eye movement, which is of great importance in identifying the source of some types of vertigo.

Inner ear (Labyrinth)

Consists of a complex cavitation in the temporal bone and is divisible into three parts, the vestibule (in the middle), cochlea (in front), and semicircular canals (in the back). All three parts form a continuous and tortuous cavitation which is lined loosely by a membrane (membranous labyrinth) separated from the bone surface by a fluid called perilymph. The membranous labyrinth, like most linings of the body, is in substance a sac with intricate ramifications. Its cavity contains a fluid called endolymph. The hearing portion of the labyrinth is the cochlea. The balance portion consists of the vestibular endorgans.

Inner ear concussion (IEC)

Indirect trauma and violent jarring of the membranous structures of the inner ear.

Inner ear concussion syndrome (Labyrinthine concussion syndrome)

A controversial syndrome consisting of chronic lightheadedness, imbalance, nausea, cognitive dysfunction, etc. (The same symptoms have been called "post-concussive syndrome," "perilymph fistula syndrome," "minor head trauma syndrome," "cervical vertigo syndrome," "whiplash syndrome," etc.). The proof of inner ear origin has been through the excellent symptomatic improvement noted with treatment of the ear.

Intratympanic (transtympanic) perfusion of the round window

The delivery of medication into the middle ear (tympanic cavity) by way of an opening in the tympanic membrane, whereupon it is perfused against the round window membrane whence it diffuses into the inner ear. The amount reaching the inner ear is proportional to the concentration of the medication times the amount of time that concentration is in contact with the membrane.

Intratympanic (transtympanic) perfusion of streptomycin. (IPS)

Perfusion of streptomycin through the tympanic membrane into the middle ear so as to obtain diffusion through the round window membrane into the inner ear. The indications for IPS are:

(1) chronic, intractable, disabling vertigo; (2) symptoms generated predominantly in labyrinth to be treated; (3) more conservative treatment not appropriate (as determined by trial or prior experience); (4) adequate vestibular and cochlear function in the contralateral ear; and (5) adequate compensatory function of the CNS.

Intratympanic perfusion of gentamicin (IPG)

See "intratympanic (transtympanic) perfusion." Gentamicin is an aminoglycoside antibiotic, with similar action and indications to streptomycin. Used mainly for treatment of Meniere’s disease, but can be effective in ablating, partially or completely, an aberrant labyrinth regardless of the pathophysiology involved.

Intratympanic perfusion of corticosteroids (TPC)

See "intratympanic (transtympanic) perfusion." Corticosteroids are anti-inflammatory medications. Indications for this use are not standardized, but it has proven to be very effective against a variety of cochlear and labyrinthine conditions.

Irritable (irritative) labyrinthine focus; "irritable labyrinth"

Abnormal, erratic (unstable) function of a labyrinth that acts as a source of vertigo or imbalance. This abnormality usually results from disease or trauma affecting the vestibular mechano-receptors, causing them to become abnormally receptive to non-vestibular stimuli, such as sound, pressure or gravitational change. If this focus is constantly being irritated (stimulated), the erratic input creates a constantly changing sensory mismatch of the patient’s vestibular perception of spatial orientation compared to the accurate visual and somatosensory cues. The brain may be unable to compensate for this persistent instability, leaving the patient with chronic, disabling vertigo and/or imbalance.

Labyrinth

See inner ear.

Labyrinthectomy

Destruction of the labyrinth, or its function.

Labyrinthine anesthesia test(LAT)

(Temporary pharmacological labyrinthectomy)

Involves placing local anesthetic intratympanically into the suspect ear, and allowing it to absorb through the round window into the inner ear. If this temporarily resolves or ameliorates the ongoing vertiginous signs or symptoms, or the postural instability, then the test ear can be assumed to be the major source of these signs or symptoms. It can also detect residual labyrinthine function not detectable by caloric testing.

Labyrinthine deficit

Decreased function of the labyrinthine sensors. With time, central compensation will typically occur if the deficit remains stable.

Labyrinthine dysfunction

Abnormal, but not necessarily decreased, function of a portion of the labyrinthine sensors. In proportion to which labyrinthine function is unstable and erratic, the CNS is typically less effective in compensating for the abnormality.

Labyrinthitis

An inflammatory condition of the labyrinth.

Macula

A patch of hair cells in the saccule and utricle. The patch is coated with a gelatinous layer that contains small granules called otoliths. This provides sensory input of inertio-gravitational orientation.

Mechanoreceptors

Organic transducer made up of a mechanical portion that activates a neural portion. It provides a specific function by reacting only to a certain form of stimuli. Example 1: a semicircular canal, which consists of a curved, fluid-filled tube with a flow sensor (cupula) at one end (mechanical) that activates attached hair cells (neural). It reacts only to angular acceleration (turning) in its plane. Example 2: an otolith organ, which consists of heavy particles (mechanical) that are attached to a bed of hair cells (neural). The direction of inertio-gravitational pull on the heavy particles, and hence the hair cells, provides input as to head position.

Membranous labyrinth

Membranous vessel comprising contiguous tubes and sacs contained within the bony labyrinth. This contains endolymph and the sensory cells for hearing and spatial orientation.

Meniere’s disease

A disease of the inner ear associated with dilatation of the membranous labyrinth (endolymphatic hydrops) and characterized by attacks of vertigo, fluctuating unilateral hearing loss and tinnitus. The attacks last for minutes to hours.

Microcath®

A special, small, patented catheter designed to deliver intratympanic medications to the inner ear, via the round window, over an extended period of time. The method has the advantage of more accurate control of dose rate.

Morbidity

Illness; sickness; adverse symptoms and signs.

Motor coordination test (MCT)

A part of platform testing that assesses the reflexes of the muscles of postural control in response to sudden movements of the platform. Detects abnormalities of CNS function and of the motor pathways.

Nystagmus

Involuntary (reflex) alternating movements of the eyeballs, induced normally by active or passive head motion; induced abnormally by disease conditions in the labyrinth or CNS. Nystagmus may also be induced during certain tests (caloric, Tullio, Hennebert, etc.). See biphasic nystagmus.

OMNIAX

Omniaxial automated chair that can place a patient in any position relative to gravity, and move them through any plane. When combined with IR nystagmography, it is a valuable tool for both the diagnosis and treatment of certain vestibular disorders.

Ossicles

Malleus, incus, stapes. The three tiny bones of the middle ear that conduct sound from the tympanic membrane to the oval window of the inner ear.

Otalgia

Pain in the ear; earache.

Otic capsule

Bone surrounding the inner ear.

Otolith, otoconia

Calcium carbonate crystals normally attached to a membrane in the otolith organs (utricle and saccule) within the vestibule of the inner ear. They provide inertio-gravitational sensation. These crystals can break off from this membrane in the saccule for various reasons and migrate into a semicircular canal, causing symptoms of BPPV.

Otolith organs

The utricle and saccule are the otolith organs. They lie within the otic capsule on the medial wall of the vestibule. Each includes a membranous sac containing fluid (endolymph). Within each sac is a macula, a flat membrane that projects sensory hair cells to its overlying otolithic membrane. The otolith organs are "mechanoreceptors," which are organic transducers made up of a neural and a mechanical portion. They are normally responsive to gravitation and other linear acceleration forces. If they become abnormally responsive to sound and/or pressure (irritative focus); the result is vertigo and/or imbalance.

Ototoxic

Toxic to the sensory cells of the inner ear (cochlear and vestibular endorgans).

Oval window

Oval-shaped opening into the inner ear. The footplate of the stapes fits into the oval window.

Particle repositioning

Procedure for repositioning of symptom-causing particles in the semicircular canals, whether initially free or attached to a cupula. so that they no longer cause symptoms.

Perilymph

The fluid contained in the space surrounding the membranous labyrinth but within the osseous (bony) labyrinth. This fluid is contiguous with the cerebro-spinal fluid via small openings.

Perilymphatic fistula (PLF)

An abnormal opening (leak) between the labyrinth and the middle ear space, commonly located at the outer margin of the stapes footplate. Thought to be most often caused by trauma, but may also be congenital or a complication of ear surgery. Significance and frequency are very controversial.

Positional nystagmus and vertigo

Nystagmus and vertigo that are precipitated or aggravated by certain position changes or assumptions, usually in relation to gravity.

Post-traumatic vertigo

Vertigo which follows trauma. Most commonly occurs when an irritable labyrinthine focus develops in the weeks to months following the incident. Other causes of post-traumatic vertigo include vestibular lithiasis, PLF, and endolymphatic hydrops (EH).

Post-treatment morbidity

The untoward symptoms and signs that result from a treatment procedure, as from surgery, chemotherapy or transtympanic perfusion with aminoglycosides.

Postural Hennebert test

Also known as the "platform pressure test", or "pressure evoked (postural) destabilization (PED) test". It is the application of air pressure to an EAC with the patient standing. It tests for postural destabilization, which is an abnormal response to pressure change of the vestibular endorgans (otolith organs or semicircular canals). When performed on a force platform, which quantifies and documents the postural stabilization, it is often called the "platform pressure test". It has also been called a "platform fistula test", which is a misnomer because this, and the various other pressure tests, are suggestive of, but not diagnostic of, a perilymphatic fistula.

Postural Tullio test

Also known as the sound evoked (postural) destabilization (SED) test. It is the presentation of sound to the test ear with the patient standing and observed for increased postural destabilization as well as other factors. It serves to detect and localize abnormal vestibular endorgans) and determines their threshold of receptivity to sound stimuli. Most commonly, a 500-Hz pure tone is presented in ascending fashion until a threshold of destabilization is noted. A force platform may be used in assessment.

Posturography

Analysis of postural responses with a force platform.

Pressure test

See Hennebert test

Pre-treatment morbidity

State of the illness, and level of symptoms, present immediately before the institution of treatment.

Psychotropic

Denotes substance that affects psychic function or behavior.

(Romberg test)

A sign manifested by unsteadiness or loss of position sense when the patient is asked to stand with feet close together and eyes closed. If the patient sways severely or falls, the sign (test) is positive.

Round window

Membrane separating the middle ear space and the fluid of the inner ear. It lies deep in the round window niche.

Saccule

A sac located in the vestibule that contains an otolith organ. It is a part of the membranous labyrinth of the inner ear.

Semicircular canals

Circular bony tube extensions of the labyrinth, with three on each side lying in orthogonal planes. Each contains a fluid duct (containing endolymph) with a dilated end (ampulla) containing a sensor (cupula) of fluid motion. By virtue of the endolymph being forced by inertia against the cupula during head movements, the semicircular canals act as mechanoreceptors (sensors) of angular acceleration (turning) in the plane of the canal.

Semicircular ducts

The membranous ducts lying within the osseous (bony) semicircular canals, and containing endolymph.

Sensorineural hearing loss (SNHL)

"Nerve loss" involving the cochlea or its central pathways.

Sensory conflict (mismatch)

A condition experienced in which the perceptions obtained through the senses of spatial orientation (visual, vestibular and somatosensory) do not match. This typically creates nausea.

Sensory organization test (SOT)

A test designed to assess the relative contribution of visual, vestibular of somatosensory sensory input to postural stability (or instability). Determined through the relative stability under 6 different test conditions on a force platform.

SOT composite score

An arbitrary, single number assessment of overall postural stability based on the average of 6 posturography test conditions.

Stenger test

A standard test for malingering of a unilateral sensorineural hearing loss.

Titration

Method of dosing medication whereby it is given only until a certain end point effect is obtained. This end point may be the advent of the desired therapeutic effect, or the onset of certain side effects.

Transtympanic

Through the tympanic membrane. See intratympanic.

Tullio phenomenon

The production of induced eye movement, vegetative symptoms (nausea, vomiting, paleness, etc.), and/or postural instability in response to loud sound presented to an ear.

Tullio test (standard)

A sound evoked test, in which the patient is observed for abnormal eye movement phenomena during presentation of loud sound to one ear. The standard test, usually performed with the subject seated, largely detects an abnormality of a semicircular canal. It is much less useful than the postural Tullio test, performed with the subject standing and observed for postural destabilization, which detects otolithic organ dysfunction as well.

Tympanic membrane

The "eardrum," a thin, taut membrane that separates the external ear canal from the middle ear air cavity.

Tympanovestibular coupling

A direct or indirect coupling between the tympanic structures (tympanic membrane, ossicles, middle ear cavity) and a vestibular endorgan, with the result that the vestibular endorgan is abnormally responsive to pressure changes or sound vibrations transmitted from the tympanic structures.

Typical nystagmus (of BPPV)

The nystagmus seen in certain positions (i.e. Hallpike position) that is pathognomonic for canalithiasis (BPPV). Essential elements are latency, quick torsional movements toward the downward placed ear, torsional axis offset toward downward ear and limited duration. Confirming elements are reversal of direction after the precipitating movement is reversed, and decay in the response upon repetition of the precipitating movement.

Utricle

A small sac in the vestibule of the inner ear that contains an otolithic endorgan. It senses mainly tilt along the roll and pitch axes.

Vertigo

An illusion of movement. The illusion can be a sensation of rotation, linear movement or tilt. Vertigo is frequently accompanied by symptoms of "imbalance" and/or "nausea." Vertigo is usually due to a recent insult to the balance system, usually occurring in the inner ear. It can also be caused by abnormalities of the CNS. Most true vertigo originates in the inner ear. Most vertigo is caused by one of the following four common dizziness syndromes involving malfunction of the inner ear: (1) vestibular lithiasis, including BPPV; (2) Meniere’s disease (endolymphatic hydrops); (3) inner ear concussion; and (4) vestibular neuronitis ("acute labyrinthitis").

Vestibular

Relating to the portion of the inner ear, and its central neural pathways, involved in the sense of spatial orientation.

Vestibule

The vestibule of the ear is the central part of the inner ear cavity, between the cochlea and semicircular canals. The utricle and the saccule are within the vestibule, and the oval and round window lead into it.

Vestibular endorgans

Utricle, saccule, and semicircular canals.

Vestibular hyperacusis

Abnormal sensitivity to noise in which the discomfort experienced is vestibular in character (vertigo, imbalance, nausea). The mechanism is thought to involve altered specificity of certain vestibular endorgans whereby they are abnormally receptive to pressure change and sound.

Vestibular lithiasis

Any condition in which abnormal densities in the vestibular endorgan produce nystagmus and/or vertigo. Includes both canalithiasis and cupulolithiasis, and can involve any semicircular canal.

Vestibular mechanoreceptors

The semicircular canals and the otolith organs, (utricle and saccule) are "mechanoreceptors," which are organic transducers that respond to specific physical factors, in this case angular acceleration or linear acceleration respectively. If they become abnormally sensitive (irritable labyrinthine focus), then vertigo, imbalance or nausea are easily produced by pressure change and/or sound.

Vestibular nerve

One of the two components of the eighth nerve. Serves the vestibular endorgans. It is concerned with controlling equilibrium and stabilizing the eyes in space.

Vestibular nerve section

Surgical transection of the vestibular branch of the eighth (acoustic) nerve. This is designed to completely and permanently eliminate all vestibular input from that side. It is a major intracranial procedure with risks of CSF leak, meningitis, facial nerve paralysis, unilateral hearing loss, etc. Rarely fatal.

Vestibular Neuronitis

An inflammation of viral origin involving a vestibular nerve that may cause severe vertigo of days to weeks duration.

Vestibular rehabilitation therapy

Physical therapy methods designed to enhance central compensation as well as habituation to non-physiologic changes in peripheral vestibular input. Effective only when the peripheral lesion is essentially stable.

Vestibulo-ocular reflex (VOR) system

The portion of the vestibular system that uses rotational (angular) sensory input from the semicircular canals to stabilize the eyes in space through involuntary eye movements (nystagmus).

Vestibulopathy

Pathology of the vestibular system.

The portion of the vestibular system that uses inertio-gravitational sensory input from the otolith organs to maintain balance by controlling the muscles of postural control.