EN4.{12-14,16-20} | Hearing Vestibular and Neuro Otology — Glossary

The WHO/national screening standard for neonatal hearing: screen (OAE) by 1 month of age; confirm diagnosis (ABR) by 3 months; fit hearing aids and begin early intervention by 6 months.

The pathognomonic audiometric signature of NIHL: a dip in hearing threshold at 4000 Hz with partial recovery at 8000 Hz, reflecting selective vulnerability of the basal cochlear outer hair cells.

American Academy of Otolaryngology — Head and Neck Surgery (1995) criteria for definite Meniere's disease: ≥2 spontaneous episodes of vertigo ≥20 minutes + audiometrically documented SNHL + tinnitus or aural fullness + other causes excluded.

The difference between air conduction and bone conduction thresholds on pure-tone audiometry; in otosclerosis typically 30–60 dB, reflecting the conductive block from stapes fixation.

X-linked (most common) hereditary nephritis (COL4A5 gene) with progressive bilateral SNHL, glomerulonephritis (haematuria, proteinuria), and ocular abnormalities (anterior lenticonus); males more severely affected.

An electrophysiological test recording five wave peaks (I–V) generated in the cochlea, VIII nerve, and auditory brainstem; in acoustic neuroma, wave V is prolonged or absent on the affected side.

A hearing disorder with absent or abnormal ABR but present OAEs, indicating intact outer hair cells but dysfunctional auditory nerve or cochlear inner hair cells; OAE screen alone would give a false pass; ABR detects ANSD.

A sensation of pressure, fullness, or blockage in the ear; the fourth element of the Meniere's disease tetrad, often a prodromal symptom preceding the vertigo attack; frequently omitted by students.

Idiopathic acute lower motor neurone facial nerve palsy, presumed due to HSV-1 reactivation causing oedema in the narrow labyrinthine segment of the facial nerve canal; accounts for ~70% of all acute facial palsies; treated with prednisolone within 72 hours.

The normal reflex upward and outward rolling of the eyeball on attempted eye closure; visible in facial palsy patients because the eyelid cannot close, exposing the sclera; confirms intact superior rectus function.

The commonest cause of episodic vertigo; caused by displaced calcium carbonate otoconia migrating into the posterior semicircular canal (usually); produces brief (<1 min) positional vertigo with fatigable upbeat-torsional nystagmus on Dix-Hallpike testing.

An H3 receptor antagonist and H1 receptor agonist used in Meniere's disease; reduces endolymph pressure and improves cochlear microcirculation; standard medical treatment for reducing frequency of Meniere's attacks.

The late stage of Meniere's disease in which vertigo attacks cease spontaneously (vestibular damage is complete and stable), but permanent SNHL and disequilibrium persist; the natural history in many patients over decades.

A formal vestibular test using warm (44°C) and cold (30°C) water irrigation of the ear canal to assess horizontal semicircular canal function; canal paresis of >25% asymmetry indicates significant unilateral vestibular hypofunction. Mnemonic: COWS (Cold Opposite, Warm Same).

Reduced or absent caloric response on one side on electronystagmography (ENG) or videonystagmography (VNG), indicating unilateral vestibular hypofunction; present in most acoustic neuromas.

A dip of 5–15 dB in bone conduction at 2000 Hz (and sometimes 500/4000 Hz) on pure-tone audiometry in stapes fixation; a mechanical artefact of impaired inertial bone conduction through the fixed stapes — NOT true sensorineural cochlear loss; disappears after stapedectomy.

The dominant neurophysiological model of subjective tinnitus: cochlear hair cell damage reduces afferent input, unmasking and amplifying spontaneous neural activity in the central auditory pathway; explains why tinnitus persists even after peripheral input is removed.

A fluid-filled cistern in the posterior cranial fossa bounded by the pons, cerebellum, and petrous temporal bone; contains cranial nerves V–X and is the commonest site for acoustic neuroma.

A branch of the facial nerve arising from the mastoid segment; carries taste sensation from the anterior two-thirds of the tongue and parasympathetic supply to the submandibular and sublingual salivary glands; its involvement causes ipsilateral taste loss.

Extension of the otosclerotic focus to the cochlear endosteum; produces a sensorineural or mixed hearing loss component in addition to the conductive element.

A surgically implanted electronic device that bypasses damaged cochlear hair cells and directly stimulates the spiral ganglion neurones via an electrode array in the scala tympani; indicated for profound bilateral SNHL not benefiting from hearing aids.

A surgically implanted device for profound bilateral SNHL that bypasses damaged hair cells by directly stimulating spiral ganglion neurones via an electrode array in the cochlear scala tympani; indicated when hearing aids provide inadequate benefit; optimal outcomes when implanted before age 18–24 months.

Hearing loss caused by a lesion in the outer or middle ear that reduces the mechanical transmission of sound to the cochlea; characterised by an air-bone gap on audiometry.

Cytomegalovirus infection acquired in utero; the most common non-genetic cause of congenital SNHL in vaccinated populations; may be asymptomatic at birth but cause progressive, sometimes late-onset hearing loss; treated with valganciclovir if detected within 1 month of birth.

The most common cause of autosomal recessive non-syndromic sensorineural hearing loss; encodes a gap junction protein in cochlear supporting cells critical for potassium recycling in the endolymph; GJB2 mutations account for 20–50% of hereditary SNHL.

Cold Opposite Warm Same — a mnemonic for caloric test nystagmus direction: cold water produces nystagmus with the fast phase directed away from (opposite to) the irrigated ear; warm water produces nystagmus toward (same side as) the irrigated ear.

The developmental window (primarily first 2 years of life) during which the primary auditory cortex is maximally plastic and establishes neural connections for spoken language; cochlear implantation before this window closes yields dramatically better language outcomes than later implantation.

A diagnostic manoeuvre for posterior canal BPPV: the head is turned 45 degrees toward the test ear and the patient is rapidly moved to supine with the head extended below the table; a positive test produces upbeat-torsional nystagmus after 2–5 seconds, lasting <1 minute, fatiguing on repeat.

An electrophysiological test recording the summating potential (SP) and action potential (AP) of the cochlea; in endolymphatic hydrops, the SP/AP ratio is elevated (>0.37–0.50); the most specific objective investigation for Meniere's disease.

An electrophysiological test measuring the amplitude of the facial nerve compound action potential; >90% degeneration compared to the normal side within 14 days of onset = severe axonal loss and poor prognosis; guides surgical decompression decisions.

Distension of the endolymph-filled membranous labyrinth caused by failure of endolymphatic sac resorption; the underlying pathology of Meniere's disease; produces episodic ruptures of the labyrinthine membrane causing attacks of vertigo, tinnitus, and hearing loss.

A structure in the petrous bone/posterior cranial fossa that absorbs excess endolymph; its dysfunction is the postulated cause of endolymphatic hydrops in Meniere's disease.

A five-position head movement sequence that repositions displaced otoconia from the posterior semicircular canal back into the utricle; first-line treatment for posterior canal BPPV; approximately 80% resolution in a single session.

The bony canal in the temporal bone that houses the intratemporal facial nerve from the IAC to the stylomastoid foramen; its narrowest part (labyrinthine segment) makes the nerve vulnerable to compression by inflammatory oedema in Bell's palsy.

The commonest form: the otosclerotic focus is anterior to the oval window (fissula ante fenestram), anchoring the stapes footplate and producing conductive hearing loss.

A small cleft in the otic capsule immediately anterior to the oval window; the most common site of origin of the otosclerotic focus.

A hearing classification used in acoustic neuroma surgery: class I (SRT ≤30 dB, SDS ≥70%) and class II (SRT ≤50 dB, SDS ≥50%) are 'serviceable' and worth attempting to preserve; class III–V are not.

The sensory ganglion of the facial nerve, located at the first genu (bend) of the intratemporal facial nerve; gives rise to the greater superficial petrosal nerve (GSPN) controlling lacrimation; the site of latent HSV-1 (Bell's palsy) and VZV (Ramsay Hunt) reactivation.

A middle ear paraganglioma (glomus tumour) arising from the glomus bodies on the cochlear promontory; presents as pulsatile tinnitus with a red-blue pulsating mass visible through the intact tympanic membrane; highly vascular — do not biopsy in clinic.

Oral glycerol (1.5 g/kg) as an osmotic agent to temporarily reduce endolymph volume; a positive test (≥15 dB improvement at ≥2 frequencies within 2 hours) supports the diagnosis of endolymphatic hydrops; used when diagnosis is uncertain.

A branch of the facial nerve arising at the geniculate ganglion; carries parasympathetic fibres to the lacrimal gland via the pterygopalatine ganglion; its integrity is tested by Schirmer's test (lacrimation).

A hypodense ring around the cochlea on HRCT temporal bone, indicating active cochlear otosclerosis (retrofenestral involvement); its presence guides treatment decisions including sodium fluoride therapy.

A validated bedside battery for distinguishing peripheral from central acute vestibular syndrome: Head Impulse test (positive = peripheral), Nystagmus type (direction-changing = central), Test of Skew (vertical skew = central); more sensitive than early CT for posterior fossa stroke.

A six-point scale grading facial nerve function: I = normal, II = mild weakness, III = moderate (eye closes with effort), IV = incomplete eye closure, V = severe (barely perceptible movement), VI = complete paralysis.

A six-point scale (I = normal, VI = total palsy) grading facial nerve function; used preoperatively and postoperatively to document and communicate facial nerve outcomes in acoustic neuroma surgery.

The characteristic MRI appearance of acoustic neuroma: intracanalicular component (the cone) with CPA extension (the ball), seen on gadolinium-enhanced T1 sequences.

A bony canal in the petrous temporal bone transmitting the facial nerve, cochlear nerve, and superior and inferior vestibular nerves from the brainstem to the inner ear structures.

Chemical labyrinthectomy — injection of an aminoglycoside (gentamicin) into the middle ear, where it diffuses through the round window membrane to selectively ablate vestibular hair cells; achieves ~85–90% vertigo control; cochleotoxicity risk ~10–30%; used when hearing is already severely impaired.

Delivery of corticosteroid (typically dexamethasone) directly into the middle ear via the tympanic membrane; used as salvage treatment in SSNHL when systemic steroids fail or are contraindicated.

Injection of dexamethasone or methylprednisolone into the middle ear; hearing-preserving; reduces Meniere's attack frequency; preferred when hearing is still serviceable; requires repeat injections.

Ossification of the cochlear lumen following bacterial meningitis (most common cause) or other cochlear insults; creates a bony obliteration of the scala tympani that prevents cochlear implant electrode insertion; occurs rapidly after meningitis — urgent CI is required before ossification is complete.

Inability to fully close the eyelid on the affected side due to orbicularis oculi paralysis; the primary early risk in facial nerve palsy is corneal exposure keratopathy from incomplete eye closure.

The central nervous system's abnormal compensatory response to peripheral sensory deafferentation, leading to increased spontaneous neural firing in deafferented regions of the auditory cortex; the proposed central generator of most subjective tinnitus.

Idiopathic endolymphatic hydrops causing the clinical tetrad of episodic vertigo (20 minutes to several hours), fluctuating low-frequency SNHL, tinnitus, and aural fullness; affects 0.1–0.2% of the population; idiopathic in origin.

The same clinical picture as Meniere's disease but caused by a known aetiology (e.g. syphilitic labyrinthitis, hypothyroidism, autoimmune inner ear disease); distinguished from idiopathic Meniere's disease, which has no identifiable cause.

The tumour suppressor protein encoded by the NF2 gene; its loss leads to uncontrolled Schwann cell proliferation and acoustic neuroma formation, especially in NF2.

A temporal craniotomy superior to the IAC, providing access to the fundus (lateral end) of the IAC from above; preferred for small intracanalicular tumours where hearing preservation is the primary goal.

Hearing loss with both conductive and sensorineural components; air-bone gap present, and bone conduction thresholds also elevated above normal.

An autosomal dominant condition (mutation in NF2 gene on chromosome 22q12, encoding merlin/schwannomin) characterised by bilateral acoustic neuromas, meningiomas, and spinal schwannomas.

Permanent bilateral symmetric SNHL caused by excessive noise exposure (≥85 dB TWA); characterised by a notch at 4000 Hz on audiometry; irreversible once established; preventable with hearing protection.

The transition point between central (CNS glial) and peripheral (Schwann cell) myelin on a cranial nerve, typically a few millimetres from the brainstem; the most common site of acoustic neuroma origin.

Tinnitus audible to the examiner (via auscultation near the ear); rare (<5%); indicates a mechanical sound source such as a vascular anomaly, glomus tumour, or muscular myoclonus.

The bony housing of the inner ear, formed from endochondral bone; uniquely, it normally undergoes no remodelling after birth — this quiescence is disrupted focally in otosclerosis.

Accumulation of non-infected fluid in the middle ear causing CHL; the commonest cause of hearing loss in children aged 2–7 years; bilateral in most cases; managed with watchful waiting (3 months) or grommets if persistent with significant hearing loss or speech delay.

Sounds generated by the outer hair cells of the cochlea (active amplification process); measured by a microphone in the ear canal; absent when outer hair cells are damaged; used in neonatal hearing screening (TEOAE/DPOAE).

Calcium carbonate crystals embedded in the maculae of the utricle and saccule; when dislodged into a semicircular canal they cause BPPV by creating abnormal cupular deflection during head movement.

A disease of abnormal endochondral bone remodelling confined to the otic capsule, causing progressive fixation of the stapes footplate and conductive hearing loss; the commonest cause of progressive CHL in young adults with normal-appearing TMs.

Cochlear or vestibular damage from drugs or chemicals; most important agents: aminoglycosides (gentamicin, amikacin), cisplatin, high-dose loop diuretics; cochleotoxicity manifests as bilateral high-frequency SNHL.

The paradoxical phenomenon of hearing better in noisy environments than in quiet ones; occurs in conductive hearing loss when background noise prompts speakers to raise their voices, giving the patient with CHL a relative signal advantage.

Autosomal recessive hearing loss (SLC26A4/pendrin gene mutation) with bilateral SNHL, enlarged vestibular aqueduct (on CT temporal bone), and goitre (thyroid enlargement); associated with thyroid organification defect.

Irreversible SNHL caused by cumulative noise-induced outer hair cell destruction; does not recover with rest; the end result of repeated unprotected noise exposure.

Age-related bilateral symmetric high-frequency sensorineural hearing loss; the most common cause of hearing loss globally in adults over 65; results from gradual cochlear hair cell degeneration at the basal turn.

Tinnitus synchronous with the heartbeat; indicates a vascular source until proven otherwise; must be investigated with MRI, MRA, and CT angiography to exclude arteriovenous malformation, glomus tumour, carotid atherosclerosis, or high-flow vascular states.

Herpes zoster oticus — VZV reactivation in the geniculate ganglion causing facial palsy, herpetiform vesicles in the external ear, and potentially SNHL and vertigo; treated with steroids plus antivirals; prognosis worse than Bell's palsy.

A posterior fossa craniotomy posterior to the sigmoid sinus, providing access to the CPA and the medial IAC with the possibility of hearing preservation; suitable for medium to large tumours.

Bone conduction perceived louder than air conduction in the Rinne test; indicates conductive hearing loss of ≥30–35 dB on the tested side.

Air conduction perceived louder than bone conduction in the Rinne test; indicates normal hearing or sensorineural hearing loss (the conduction pathway is intact or both pathways are equally impaired).

Deterioration of speech discrimination score at high presentation intensities on performance-intensity (PI) function testing; a hallmark of retrocochlear (VIII nerve) pathology as in acoustic neuroma.

A topognostic test measuring lacrimation by placing filter paper strips in the conjunctival sac for 5 minutes; reduced wetting on the affected side indicates a lesion at or proximal to the geniculate ganglion (GSPN affected).

A faint pinkish-red blush visible through the intact tympanic membrane in the region of the oval window, caused by the hypervascular active otosclerotic focus; indicates active, progressive disease.

Hearing loss caused by dysfunction of cochlear hair cells, the eighth cranial nerve, or central auditory pathways; no air-bone gap; bone conduction thresholds elevated.

A medical treatment for active otosclerosis that arrests disease progression by incorporating fluoride into the abnormal bone, making it more resistant to resorption; does not restore already-lost hearing; given with calcium and vitamin D.

The ratio of the summating potential to the action potential on electrocochleography; normally <0.37–0.50; elevated in endolymphatic hydrops (Meniere's disease), reflecting the distortion of the receptor potential from distended Reissner's membrane.

The original Shea operation for otosclerosis: complete removal of the stapes arch and footplate with placement of a prosthesis from the incus to an oval window tissue graft; largely replaced by stapedotomy.

A bilateral reflex contraction of the stapedius muscle in response to loud sound, testing the VIII nerve → brainstem → VII nerve arc; absent or decaying in acoustic neuroma (retrocochlear pattern).

The current gold standard surgical treatment for otosclerosis: a small fenestra (0.6–0.8 mm) is made in the stapes footplate, and a piston prosthesis is inserted from the incus long process through the fenestra into the vestibule; lower risk of sensorineural loss than stapedectomy.

Focused ionising radiation (Gamma Knife, CyberKnife, or LINAC) delivered precisely to the tumour in a single or few fractions, causing growth arrest; achieves ~90–95% tumour control over 10 years for acoustic neuroma ≤3 cm.

Tinnitus perceived only by the patient, generated by the cochlea, eighth nerve, or central auditory pathway; the vast majority of tinnitus cases; most commonly associated with sensorineural hearing loss from noise, ageing, or ototoxicity.

An otological emergency defined as ≥30 dB SNHL at ≥3 contiguous audiometric frequencies developing within 72 hours; mostly idiopathic; requires same-day ENT assessment, MRI, and high-dose corticosteroids.

Abnormal misdirected reinnervation following facial nerve damage, causing simultaneous involuntary movement in one part of the face during voluntary movement of another (e.g. eye closure during smiling); managed with botulinum toxin.

A reversible rise in hearing threshold immediately after noise exposure, caused by outer hair cell metabolic fatigue; recovers within hours to days; repeated TTS leads to permanent threshold shift.

The perception of sound in the ear or head in the absence of an external acoustic stimulus; affects ~10–15% of adults; can be subjective (perceived by patient only) or objective (audible to examiner).

The measured intensity of a sound that the patient perceives as equivalent in loudness to their tinnitus; typically only 5–10 dB above hearing threshold, despite subjective perception of the tinnitus as very loud; useful for patient education.

A clinical technique using an audiometer to match the perceived pitch of a patient's tinnitus to a pure tone or narrow-band noise; most tinnitus matches to 3–8 kHz; useful for counselling (the matched loudness is typically only 5–10 dB above threshold).

A structured tinnitus management programme combining directive counselling (explaining the neurophysiological model to demystify tinnitus) with sound therapy (low-level broadband noise to reduce the contrast between tinnitus and silence); the most studied evidence-based non-pharmacological treatment.

A battery of clinical tests (Schirmer's test, stapedial reflex testing, taste testing) used to estimate the anatomical level of a facial nerve lesion by determining which branches are functionally impaired.

A surgical approach to the IAC and CPA through the mastoid and inner ear (labyrinth), providing wide direct access but necessarily sacrificing cochlear function; chosen when hearing preservation is not a goal.

A tympanogram with reduced peak compliance (shallow curve) at normal peak pressure; characteristic of stiffened ossicular chain as in otosclerosis or tympanosclerosis; contrasts with type B (flat, effusion) and type Ad (hypercompliant, discontinuity).

Autosomal recessive syndromic hearing loss with congenital bilateral SNHL (moderate to profound) plus progressive retinitis pigmentosa causing tunnel vision and night blindness; the most common cause of combined deaf-blindness.

Acute unilateral peripheral vestibular hypofunction, presumed viral (HSV-1 reactivation in Scarpa's ganglion); presents as acute continuous vertigo lasting days to weeks without hearing loss; treated with prochlorperazine acutely and vestibular rehabilitation during recovery.

A structured programme of gaze stabilisation and balance exercises that promotes central adaptation to chronic unilateral vestibular hypofunction; first-line long-term treatment for persistent dizziness after vestibular neuritis.

The correct name for acoustic neuroma — a benign tumour of Schwann cells of the vestibular division of cranial nerve VIII, arising at the Obersteiner-Redlich zone in the internal auditory canal.

The reflex that stabilises the visual image on the retina during head movement by generating equal and opposite eye movement; tested by the head impulse test; impaired in unilateral vestibular hypofunction (positive HIT = corrective saccade visible).

A behavioural hearing test for children aged 6 months to 2.5 years; the child is conditioned to turn toward a sound by being rewarded with a visual stimulus (e.g. animated toy); allows sound-field threshold estimation.

An autosomal dominant syndromic hearing loss (PAX3 gene mutation) characterised by bilateral SNHL, white forelock, premature greying, heterochromia iridis, and telecanthus (dystopia canthorum in type I).