INNER EAR INFECTIONS

-18% infants born deaf or impaired hearing are proven to be caused by cong viral inf’n.

-Each year > 4000 persons get sudden deafness,(unilateral or bilateral Jaffe1973).? Inf’n.

-Bacterial labyrinthitis with profound hearing loss occurs in about 10% of individuals with

bacterial meningitis (Dodge et al., 1984).

-Thousands each year suffer from vestibular neuritis.

This acute deficit in vestibular function is accompanied by a period of intense vertigo

that many think has an infectious origin (Schuknecht and Kitamura, 1981).

-NB HSV and adenovirus are commonly latent in humans (oropharynx Fox & Hall, 1980).

Other viruses: ECHO, coxsackievirus, throats or stools of asymptomatic individuals. particularly when the virus is prevalent in the community (Fox and Hall, 1980).

-For labyrinthine infections, optimal proof of causality involves fulfillment of three criteria (see box on p. 2796).

(i) there should be an association of suspected bug with specific clinical synd. of D&V .

(ii) bug should be isolated from or identified in diseased labyrinthine tissues.

(iii) bug should be capable of causing a similar disease in experimental animals.

-Methods to identify viruses within the inner ear:

-isolated from perilymphatic fluid, endolymphatic fluid, inner ear tissue at Sx / autopsy.

-Viral antigens( by immunohistochemical methods)

-viral nucleic acid (by nucleic acid hybridization or by polymerase chain reaction

(Eisenstein, 1990; Falser et al., 1986).

-bacteria or fungi; light or electron microscopy.

- viral-specific cell changes occas. identified (eg Viral inclusion bodies & giant cells)

-To date only CMV & mumps virus identified from labyrinth

Treponema pallidum (Mack et al., 1969) \

measles virus (scala vestibule , Lindsay Hemenway, 1954).

NB: rubella virus is:

i. closely associated epimiologically with congenital deafness

ii.has been isolated from many sites in congenitally deaf infants,

BUT has never been isolated from viral antigens identified within inner ear

-The following infectious agents have been associated with deafness or vertigo, but have yet to fulfill the three criteria for optimal proof of causality.

Rubella Lymphocytic choriomeningitis

Varicella-zoster Yellow fever

Herpes simplex Western equine encephalitis

Epstein-Barr Tick-bome encephalitis

Variola (smallpox) St. Louis encephalitis

Hepatitis virus Encephalomyocarditis

Adenovirus Lassa fever

Influenza

Parainfluenza Coxsackievirus

CONGENITAL CYTOMEGALOVIRUS INFECTIONS

Incid: -most common congenital infection (in US >4000 cases / yr of SNHL Stagno 1977). -incidence of CMV about 1-2 per 100 live births (Reynolds et al., 1974).

-approx 90% of congenital infections are "silent,"

-1% to 5% are symptomatic => cytomegalic inclusion disease (CID) => multiorgan

damage (incl. liver, spleen, brain, eye, and inner ear (Hanshaw, 1976).

Clinical features

-incidence SNHL in childre with CID is up to 50% (Alford et al., 1990).

Hearing: -loss is at low frequency

-marked asymmetric or unilateral loss only occasionally

-some children born with moderate HL, may progress during first 10 years

The explanation: unknown.

-infants with silent infections, follow-up examination => 5%-15% develop

mild to moderate bilateral hearing loss (Hanshaw 1976; Reynolds 1974)

Diagnosis

-made (in symptomatic & asymptomatic infants) by isolation of CMV from fresh urine

-60% to 75% of congenitally infecte infants have detectable IgM Ab’s to CMV

Management

-Acyclovir ; => a transitory decrease in urinary shedding of CMV but no clinical improvt.

-Ganciclovir (newer,related drug) 25-100-x’s more active vs acyclovir against CMV.

-Foscamet (another new drug) antiviral activity against CMV (Balfour, 1990).

Temporal bone pathologic changes

- presence of inclusion-bearing cells in auditory and vestibular portions of the inner ear.

-in cochlea pathologic changes are most severe in basal turn.

-In organ of Corti, major hair cell degeneration does not occur and tectorial memb is (N).

-CN VIII ( & its spiral ganglion neurons) are spared of major pathologic damage.

-Hydrops of cochlea & saccule & collapse of Reissner's membrane has been observed.

-Immunofluorescence has identified CMV Ag:

- within cells lining memb. lab

- perilymph & endolymph.

-HSV particles have been seen within cells of memb lab by EM

CONGENITAL RUBELLA DEAFNESS

Incid:

-maternal rubella infection during first trimester =>highest risk for congenital infection

=> hearing loss, cardiac malformations, vision loss, and mental retardation

-50% of infants bom with symptomatic congenital rubella have hearing loss.

-2nd & 3rd trimester infection (often born with silent rubella) and appear normal at birth.

Of these: 10% to 20% develop hearing impairment (Karmody, 1968).

NB ! : Rubella vaccine can cross placenta and can infect fetus administered to

nonimmune pregnant women. Fortunately, risk of subsequent HL is minimal. Clinical features:

-usually => mild to severe bilateral hearing loss. ( ? asymmetric ).

-some children have delayed or impaired speech development but N pure-tone hearing, => central imperception (Ames et al., 1970).

-vestibular system is involved to a lesser extent.

Caloric stim’n => reduced or absent responses in 1 or both ears

-Diagnosis : (1) Isolation of rubella from urine or throat cultures during first weeks of life,

(2) identification of IgM antibodies against rubella in serum from neonate,

(3) increased Ab titer to rubella virus in infant during first few months of life.

-Temporal bone pathologic changes

-changes in congenital rubella deafness are characteristic BUT not specific for rubella.

-abnormality is cochleosaccular degeneration and strial atrophy of varying degrees (Brookhouser and Bordley, 1973; Lindsay et al., 1953).

ACQUIRED MUMPS VIRUS DEAFNESS

- Incid: -first recognized association with deafness in 1860.

-incid: (Everberg 1957) mumps=> hearing loss about 5 per 10,000 mumps cases -Children & young adults commonly.

Clinical features

-deafness: -develops toward end of parotitis.

-occasionally occurs, however, with no parotitis.

-onset usually rapid,

-unilateral 80% of time.

-often profound and usually permanent, (?? transient ).

-maximal in high frequencies.

-Tinnitus and fullness in involved ear, common,

-Vertigo in some (usually resolves over several weeks) NB: diminished/absent calorics

Diagnosis

-(1) isolation of mumps virus from throat or CSF.

-(2) fourfold or greater rise in mumps antibodies b/w acute & convalescent serum

-NB: isolated from perilymphatic fluid in one patient with acute unilateral deafness associated with parotitis (Westmore et al., 1979).

Mx: no specific treatment (vaccine only)

Temporal bone pathologic changes

-cochlea => - severe atrophy of organ of Corti and stria vascularis

- partial collapse of Reissner's membrane in the basal turn

- tectorial membrane folded, thickened, displaced from organ of Corti.

-upper turns had less damage, with occasional loss of hair cells.

-ganglion neurons may decrease in area of basal turn.

-minimal vestibular abnormalities.

Mechn :

- ?? into perilymph from CSF (???2ry to meningitis & patent cochlear aqueduct)

- since deafness usually develops at end of Wk 1 of parotitis (Everberg, 1957),

the clinical course of deafness is consistent with virus spread from CSF to inner ear.

-CN VIII (with cuff of arachnoid containing CSF), provides another route to perilymph.

-One study, however, found no correlation between sensorineural deafness and

meningitis (Vuori et al., 1962).

ACQUIRED MEASLES DEAFNESS

-Rubeola virus causes measles

-impt cause of acquired deafness.

-incidence of deafness following rubeola, is < I per 1000 cases of measles (Miller 1956).

Clinical features

-labyrinthine involvement => abrupt bilateral ( some unilat ) hearing loss at time of rash.

-cxtic audiogram => bilateral loss (may be asymmetric).

maximal hearing loss occurs at high frequencies.

-hearing loss : usually permanent ( +/- tinnitus and vertigo).

NB: 70% of patients may have absent or diminished calorics in one or both ears (Shambaugh et al., 1928).

Diagnosis

(1) isolation of rubeola virus from throat cultures;

(2) rubeola viral antigen by immunofluorescence pharynx, conjunctiva, or buccal cavity; (3) fourfold serologic rise in measles Ab titer b/w acute & convalescent serum samples.

Temporal bone pathology

-cochlear: -degeneration most severe in basal turn.

-tectorial membrane thickened and distorted.

-stria vascularis atrophy (maximal change in basal turn).

-saccule collapsed & membranous wall adherent to degenerated macular epith.

-giant cells, (typical of measles ) seen in organ of Corti and spiral ganglion cells.

ACQUIRED VARICELLA-ZOSTER VIRUS DEAFNESS Ramsay Hunt syndrome

- Ramsay Hunt syndrome (or herpes zoster oticus), caused by varicella zoster virus

& occurs years after the primary infection that manifests as chickenpox

-deafness occasionally; usually caused by 2ry viral or bacterial otitis media=> CHL

-auditory & vestibular symptoms in 25% patients with herpes zoster oticus (RH Synd).

Clinical features

-painful vesicles on skin of pinna, behind pinna, & along EAM.

-VII paralysis & deep ear pain 1-2 days later (Aleksic, 1973)

-facial weakness usually improves over weeks (occasionally permanent).

-25% of patients=> hyperacusis, tinnitus, nystagmus, & disequilibrium + facial paralysis - vertigo (severe) associated with ear vesicles but not facial paralysis.

-SNHL in 5% of patients (occasionally permanent).

-Audiograms suggest primary cochlear involvement or cochlear nerve involvement

-Caloric tests => decreased or absent in involved ear.

Diagnosis:

-suspect in patient with acute facial weakness & vesicles on auricle or in EAM.

-diagnosis can be confirmed by isolation of VZ from vesicle fluid.

-MRI: gadolinium enhancement of involved geniculate ganglion & nerve (Tien, 1990).

Prognosis:

-hearing loss, facial weakness and vertigo usually improve, over several weeks.

Management

-Acyclovir:

- increases rate of virus disappearance in skin lesions

- decreases pain in acute zoster

- dosage is 5 mg/kg/dose IV tds for 5 to 10 days.

-Corticosteroid may=> reduce intensity of inflm’n & edema in facial canal &labyrth.

NB: If hx of peptic ulcers => Zantac

Monitor BSL’s.

-Analgesia.

Mechns:

-caused by reactivation of latent VZ in geniculate ganglion=>

-vesicles over sensory portion of VII,

-ganglionitis and neuritis of VII (Aleksic 1973).

-patients with auditory and vestibular symptoms, the inflammation spreads to:

-involve CN VIII and labyrinth (Blackley, 1967; Proctor, 1979).

Temporal bone pathologic changes

-During subacute phase:

-active neuritis of VII with inflammatory cells, edema, necrosis, & hemorrhages

through the nerve sheath, but maximally near geniculate ganglion.

-geniculate ganglion also => inflammation, edema, and neuronal degeneration. - facial nerve nucleus in the brain stem is not involved.

- auditory nerve and labyrinth changes:

-inflammatory cells in CN VIII, (esp. vestib. branches), macula of utricle & saccule

BACTERIAL AND FUNGAL LABYRINTHITIS

Pathophysiology

-Bacteria and fungi can =>

(1) suppurative labyrinthitis ( most cases) with bugs reaching cochlea from:

-subarachnoid space (meningitis),

(ie. bugs reach scala tympani from SA space via pat. cochl aqedct

or up IAM passing through perineural & perivascular spaces)

-temporal bone (osteomyelitis),

-middle ear (otitis media).

(2) toxic labyrinthine damage from fungal toxins or inflammatory cell cytokines reaching perilymph through round window or modiolus

(3) purulent exudate enveloping CNVIII with nerve infarction or entrapment,

(4) ototoxic antibiotics given to treat the infection

Temporal bone pathologic changes

-bacteria into labyrinth => suppurative labyrinthitis.

=> severe hearing loss (usually permanent)

=> acute vertigo (resolves over weeks to months)

( permanent loss of calorics ).

-following antibiotic treatment,

=> acute inflammation resolves,

=> macrophages invade from bloodstream=> granulomas

-mnths-yrs fibroblasts invade memb. Lab=> scarring of endolymphatic structures

-multipotential mesenchyme cells invade and proliferate from the adjacent modiolus,

bony endosteum lining, => osteoblasts.

-osteoblasts form ectopic ossification (may partially obliterate memb labyrinthine space)

HEARING LOSS IN BACTERIAL MENINGITIS

Incid:-1/3 of all hearing deficits after birth are caused by complic’ns of arterial meningitis

-can be SNHL or CHL

-incid of HL varied with strain of bacteria isolated from CSF:

Streptococcus pneumoniae 30%

Neisseria meningitides 10%,

Haemophilus influenzae 5%.

Clinical features

- deafness occurs early during meningitis.

-if hearing loss not present by second 2 of antibiotic treatment=> rarely develops later.

-early diagnosis and treatment of meningitis may not prevent deafness (Klein 1986).

-all ages equally susceptible

-may be unilateral or bilateral.

-involves all frequencies and often profound.

-most permanent loss of hearing

-vertigo, nausea and vomting, and ataxia are often present

-ABR’s helpful in children

Mx

-A/B’s that cross BBB

-controversy ???? corticosteroids reduces incidence of hearing loss.

mech: ?? intense inflammation in/near memb. lab or VIII => 2’ry damage to cochlea or VIII

-once hearing loss has developed,=> no treatment works

CONGENITAL AND ACQUIRED SYPHILITIC DEAFNESS

Defn’s

-SNHL can be complication of congenital and acquired syphilis.

-Congenital syphilis (2 forms):

-early congenital (birth to 3 years)

-late congenital (8 to 20 years).

-Acquired syphilis:

-both secondary and tertiary stages may => deafness.

Clinical features

- SNHL hearing loss is bilateral, profound

-few vestibular symptoms and signs are noted.

-congenital syphilitic hearing loss

-usually b/w 8-20 (or longer) years when Sx’s first appear

-usually develop progressive but fluctuating,asymmetric hearing loss.

-tinnitus maybe intermittent.

- may get acute vertigo (similar to Meniere's) ..... decreased caloric responses found

-Hennebert's sign (a positive fistula test with intact tympanic membranes) may be present.

-Other signs of late late cong. syphyllis=>

-Hutchinson's teeth (pegshaped & notched permanent upper central incisors),

-mulberry molars ( first lower molar grinding surface with many tiny cusps),

-interstitial keratitis.

-audiograms => flat SNHL

-low speech discrimination scores are out of proportion to loss in pure-tone thresholds.

-early acquired syphilitic deafness

-usually occurs during 2’ry (Saltiel , 1983).

-usually abrupt onset

-tends to be bilateral and progressive.

-usually minimal vestibular symptoms

-may have headaches, stiff necks, CN palsies, optic neuritis, 2ry syphilitic rashes, LADY

- CSF shows lymphocytic pleocytosis, elevated protein, and normal glucose.

-late acquired syphilitic hearing loss

-usually occurs during 3’ry stage (Nadol, 1975).

-similar to late congenital form

-progressive, fluctuating, asymmetric, & sensorineural.

-tinnitus & vertigo (decreased caloric responses & positive fistula test with intact TM)

-loss of speech discrimination out of proportion to pure-tone HL

-CSF => minimal pleocytosis & elevated or normal protein.

Diagnosis

-all types of syphilitic hearing loss => +’ve fluorescent treponemal antibody-absorp’n in serum.

-spirochetes have been demonstrated by dark-field examination of perilymph obtained from a

diagnostic stapes footplate labyrinthotomy.

Management

-treatment of choice in syphilitic hearing loss is penicillin for 2 months.

-prednisone, 30 to 60 mg/day on alternate days for 3 to 6 months

-if hearing loss recurs after tapering, => long-term maintenance of prednisone (10-20 mg alt.days)

-prognosis: - poor in early congenital form

- better in late congenital or acquired forms

-Overall, 50% of patients show minor to considerable improvement after treatment.

Temporal bone pathologic changes

-early congenital=> -a labyrinthitis

-lymphocytic infiltration & destruction of labyrinth and CN VIII.

-spirochetes have been seen

-late congenital => -an osteitis of otic capsule with 2’ry involvement of the membranous labyrinth -may ® endolymphatic hydrops.

-early acquired => basilar meningitis affecting VIII, (esp.its auditory branch).

-late acquired => an osteitis resulting in 2’ry degeneration of cochlear.

VESTIBULAR NEURITIS

-also called: epidemic vertigo, acute labyrinthitis, vestibular paralysis, & vestibular neuropathy.

-vestibular neuritis currently prefeffed b/c pathologic findings =>vestibular n is site of damage

-URTI"s usually precede in about 50% of cases (Clemis and Becker, 1973);

NB: no viruses have been proven to cause vestibular neuritis.

Clinical features

- peak onset of vestibular neuritis is b/w 30 - 60 years.

-most pts => abrupt onset with single, severe attack of prolonged vertigo.

-occasionally several attacks over next weeks to months

-occasionally hospitalization because of dehydration.

-usually one ear is involved.

-compared to Meniere's, vertigo lasts longer and has no auditory symptoms.

-no other CNS abnormalities

-vigorous spontaneous nystagmus toward the uninvolved side (usually horizontal or rotary).

-caloric responses are diminished or absent in involved ear.

-CSF & EEG are normal.

Prognosis

-acute vertigo usually lasts days to weeks, with gradual recovery over weeks to months

-by 6 months most patients fully

-spontaneous nystagmus usually lasts I to 3 weeks.

-at clinical recovery, caloric response often returns to normal

Temporal bone pathologic changes

-primary damage to vestibular nerve (Schuknecht and Kitamura, 1981).

-partial-total loss of VIII branches (esp in sup. div’n supplying horizontal & sup ampullae)

-degeneration of hair cells

-NB: In expermts viruses shown to infect vestibular part of labyrinth & vestibular ganglion cells These include rubeola, herpes simplex, mumps, and reoviruses.

MENlERE'S DISEASE

- cause unknown.

-syphilis has been found as cause in about 10% patients with Meniere's-like syndrs (Nadol, 1975). -viral infct’n postulated as possible cause of endolymphatic hydrops(Adour1980; Schuknecht82)

-Herpes simplex virus considered

-experimentally, guinea pig CMV inoculations =>endolymphatic sac may =>endolymph hydrops

Bibliography:

Cummings, C. Otolaryngology.  chapter 155

Gates Current Therapeutics

Scott Brown, , Otolaryngology

Schucknect, Pathology of the Ear