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ANATOMY AND PHYSIOLOGY OF HEARINGSENSORINEURAL HEARING LOSS
e main aim in evaluating a patient with SNHL is to identify any treatable causes, and the
provision of supportive treatment. e speed of onset of symptoms, laterality, and accompanying otological symptoms should be questioned. Previous otological conditions or surgery,
a history of trauma (including barotrauma), or intense noise exposure as well as a recent viral
infection may help to identify a cause. A full drug history, particularly aminoglycosides and
chemotherapy, is important in considering ototoxicity. A strong family history of early-onset
HL (before the age of 40) may indicate a genetic cause.
Examination should include otoscopy, tuning fork tests, cranial nerve examination, and
audiometry. Speech testing can help determine the impact of the HL. A magnetic resonance
imaging (MRI) scan of the internal auditory meatus should be performed in cases of asymmetrical HL (asymmetry on pure-tone audiometry of 15 dB or more at any two adjacent test
frequencies, using test frequencies of 0.5, 1, 2, 4, and 8 kHz; NICE 2020) to exclude a vestibular schwannoma or other intracranial pathology. Blood testing may be helpful to exclude an
autoimmune or infective cause.
General Management of Sensorineural Hearing Loss
Guidance should be given to patients to optimise their acoustic environment, and they
should be oered psychological counseling if their HL is having a negative impact on their
mood. Management may include provision of hearing aids/auditory implants, auditory rehabilitation, and the use of hearing assistance technology (see Chapter 17).
Specic Conditions
Sudden Sensorineural Hearing Loss (SSNHL)
Sudden sensorineural hearing loss (SSNHL) is dened as HL of rapid onset of ≥30 dB over
greater than three consecutive frequencies developing over ≤72 hours with a subjective sensation of hearing impairment. e majority of cases are idiopathic, with a cause identied in
only 5–10% of cases. Routine laboratory testing is not advised, although one might consider
specic blood tests (e.g. Lyme disease serology, autoantibodies, etc.) depending on the clinical
history. e possible causes of ‘idiopathic’ cases include labyrinthine viral infection, vascular
insult, intracochlear membrane rupture, and autoimmune inner ear disease. However, epidemiological, serological, and histopathological evidence to support these theories are inconclusive. In general, the shorter the history the better the prognosis. Age >60 years, the presence
of vertigo, and a more severe HL with a down-sloping audiogram are all features associated
with a poorer prognosis. Spontaneous recovery occurs in 32–65% of cases, typically within
2–6 weeks, even without treatment. Evidence is poor for the various proposed treatments due
to the combination of low incidence and high spontaneous recovery rate. Studies using agents
other than those detailed below, including antivirals, do not oer any signicant benet.
Specic Management
Steroids
Oral steroids are the standard treatment of SSNHL despite systematic reviews and metaanalyses revealing limited evidence of benet. Treatment started within 2 weeks of onset is
associated with the greatest hearing recovery; there is minimal benet aer 4–6 weeks. A
10- to 14-day course of once-daily oral prednisolone (1 mg/kg [maximum 60 mg]) is associated with better outcomes.
Intratympanic (IT) steroid therapy results in higher inner ear steroid levels than oral therapy.
e main advantage is a reduction in systemic side eects; therefore, it can be valuable in diabetics or patients who cannot take systemic corticosteroids. Dexamethasone and methylprednisolone sodium succinate are the most frequently used preparations. ere is no evidence on
which steroid is superior; however, better hearing outcomes have been associated with higher
doses and the cumulative eect of multiple administrations. Commonly this is administered
via a grommet or injected intratympanically under local anaesthetic with the patient lying in
a supine position and the injected ear facing towards the ceiling for approximately 30 minutes
78 e Ear
14. SENSORINEURAL HEARING LOSS
SENSORINEURAL HEARING LOSS
to facilitate diusion of the drug across the round window membrane. Diusion across the
round window membrane is variable and leads to unpredictable intracochlear bioavailability.
Risks of IT administration include pain, dizziness, and persistent tympanic membrane perforation at the site of injection. No comparative trials have shown superiority of primary IT
steroid therapy over oral steroids with respect to hearing outcomes; however, combination
therapy has been shown to improve overall hearing compared with oral treatment alone.
Hyperbaric Oxygen Therapy (HBOT)
Hyperbaric oxygen therapy (HBOT) delivers 100% oxygen at >1 atm pressure resulting in
increas ed tissue oxygenation and aids the re sponse to infection a nd ischaemia. Compl ications
of treatment are rare but include barotrauma to ears, sinuses, and lungs; temporary worsening of short-sightedness; claustrophobia; and oxygen poisoning. It is an expensive and timeconsuming treatment given over days or weeks and is not widely available. However, some
benet has been shown when initiated within 3 months of the onset of HL; the benet is
potentially greater in cases of severe to profound HL. Studies have shown some benet of
both IT steroids and HBOT as salvage therapies for refractory SSNHL.
Noise-Induced Hearing Loss (NIHL)
e eect of noise exposure on individuals is highly variable. Sound levels <80 dB(A) at any
length of exposure will not cause damage to the human ear. Sounds ≥130 dB(A) will denitely cause damage, even if the exposure time is short. Between these levels, the ‘safe’ period
of exposure decreases as the sound level increases, in a logarithmic fashion. Doubling the
sound intensity (3-dB increase) eectively ‘doubles the noise dose’, which means exposure
is only safe for half the time period. is is described as the ‘equal energy principle’. It only
applies approximately in animal experiments.
Initially, excessive noise exposure causes a temporary threshold shi (TTS), resulting in a
temporary HL. e high-frequency regions of the cochlea are most sensitive (between 3 and
6 kHz). Recovery of the TTS occurs over hours, days, or weeks following exposure. Expected
recovery time is dependent on the loudness and duration of the noise presented. However, a
permanent threshold shi (PTS) can occur at the initial insult, or it may evolve where there
is continuous or repeated excessive noise exposure at levels that would only have otherwise
caused a TTS. It is thought that this may be caused by metabolic factors such as excessive
neurotransmitter release, changes in cochlear blood ow, and oxidative stress within the hair
cells. Structural factors like depolymerisation of actin laments in the stereocilia, swelling
of the stria vascularis, and damage to aerent nerve endings and supporting cells are also
thought to play a part. Synaptic connections between inner hair cells and spiral ganglion
cells may also be susceptible to noise damage. Importantly, in animal studies, these synapses
can be the rst site of damage, even without an HL (‘hidden hearing loss’, or synaptopathy).
Additionally, genetic susceptibility, smoking and cardiovascular disease, and diabetes have
been implicated as risk factors.
Patients present with symptoms of HL and tinnitus alongside a history of excessive noise exposure, which may be occupational or recreational. It is more common in men. Hyperacusis may
be a feature causing accompanying distress and impaired social functioning. Acoustic shock is
a particular subgroup of noise-induced hearing loss (NIHL). It appears more oen in women,
particularly in call centres, and occurs aer exposure to a brief but unexpected loud and
unpleasant sound. Acoustic shock appears to cause high levels of psychological distress associated with symptoms of hyperacusis, otalgia, tinnitus, and imbalance. Objective HL is rare.
When assessing a patient with NIHL, volunteered post-exposure tinnitus suggests that TTS
was present. It is important to detail all potential sources of noise exposure, typical noise levels and periods of exposure, and any hearing protection used. A high-tone HL with a notch
at 3/4/6 kHz may be present, but it may not be obvious and it is not diagnostic. Signicant
asymmetrical thresholds may be present in military personnel due to the shadow eect from
the head when using shoulder-borne weapons.
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ANATOMY AND PHYSIOLOGY OF HEARINGSENSORINEURAL HEARING LOSS
e main aim in (medicolegal) assessment is to separate the eects of ageing and any other
idiopathic or degenerative component from that of the noise exposure. Standardised reference tables provide hearing thresholds at various ages for typical screened and unscreened
populations. Comparing the patients’ (or claimants’) hearing thresholds against expected
‘average’ values for age-related and idiopathic causes should allow an estimate of any excess
HL caused by noise exposure.
Specic Management
NIHL is a preventable health condition. Employers have a statutory duty under the Health
and Safety Work Act 1974 to minimise risks to employees from excessive noise exposure. e
Noise at Work Regulations 1989 were superseded by the European Control of Noise at Work
Regulations 2005 to describe action levels at 80 and 85 dB(A) for daily personal noise exposure, and a peak action level of 135 dB(A). At these levels, the employer has a responsibility
to conduct noise surveys and provide employees with hearing protection as well as regular
hearing assessments and a programme of employee education. ese actions are compulsory
when noise levels reach ≥85 dB(A). Personal hearing protection can be in the form of earplugs
or earmus; earmus are more reliable. Electronic active noise reduction (ANR) systems are
eective but expensive and are most commonly used in military and aircra environments.
Age-Related Hearing Loss
Age-related hearing loss (ARHL) is a progressive, bilateral, sensorineural hearing impairment of mid to late adult onset (typically starting between the ages of 40 and 60 years) in
the absence of any other cause of HL. Once hearing thresholds have deteriorated to approximately 75–80 dB HL, further progression appears to be slow.
ARHL is associated with male gender. ere is likely to be a signicant genetic association,
and recent gene-mapping studies have identied new and previously unrecognised genetic
loci that are relevant to ARHL. Noise exposure, smoking, alcohol consumption, hypertension, blood hyperviscosity, and cardiovascular and cerebrovascular disease have all been
suggested as possible contributory factors in developing ARHL.
Other degenerative processes in the central nervous system such as reduced neuronal plasticity, loss of cognitive abilities, and loss of other sensory modalities, particularly vision, can
massively increase the impact of HL in the elderly. is also explains why the elderly oen
require a long acclimatisation period to obtain maximum benet from hearing rehabilitation
and aids. ARHL is associated with cognitive impairment including dementia, depression,
and an increased incidence of falls. It has been recognised as one of the most signicant of a
number of modiable risk factors active in the development of dementia. Early recognition
of the need for, and encouraging the use of, hearing aids may in turn reduce the development
of these psychosocial comorbidities.
Most commonly the audiogram shows an HL which tends to be worse at the higher frequencies. In an individual over the age of 60, with normal examination ndings and a symmetrical (oen predominantly high-tone) HL, a diagnosis of ARHL is fairly secure. However, in
younger patients, a diagnosis of genetic, ‘non-syndromic’ HL should be considered.
Genetic Hearing Loss
Non-syndromic SNHL accounts for approximately 70% of genetic SNHL cases. e remaining 30% are recognised as being part of a syndrome. e inheritance pattern can be autosomal dominant, recessive, X-linked, or mitochondrial. A genetic HL may be recognised
when it is observed that several generations of family members have been aected. However,
de novo mutation or, a reduced penetrance inheritance pattern, may cause a singleton case.
Linkage analysis combined with whole genome/exome sequence analysis enables the identication of novel genes and pathways causing inherited SNHL. To date more than 60 loci
for genes causing HL have been mapped, but only just over half of the specic genes have
been identied.
80 e Ear
14. SENSORINEURAL HEARING LOSS
SENSORINEURAL HEARING LOSS
e audiometric pattern observed in genetic HL can vary. Some mutations result in a
low-frequency HL, whereas others result in a steeply down-sloping HL involving the high
frequencies. A ‘U-shaped’ or ‘cookie-bite’ audiogram is caused by an HL aecting the midfrequencies. Although some SNHL loci are associated with particular audiometric patterns
or clinical presentations, there is marked variability: the age of onset of HL, progression,
and audiometric conguration can vary between individuals even within one family, making distinction between genetic causes dicult. Achieving a molecular genetic diagnosis
through genetic testing may help to predict the progress of HL and guide genetic counselling. is is likely to be a more rewarding process in familial clusters rather than isolated
singleton cases.
Ototoxicity
Table 14.2 summarises known ototoxic agents and their mechanisms of action. ese agents
enter the inner ear through various mechanisms where they can cause damage. Entry is
predominantly via the blood supply into the perilymph, although the precise mechanism of
diusion across this blood-perilymph barrier is unknown. Endolymph can be accessed via
perilymph through selectively permeable membranes and tight junctions between adjacent
cells. Diusion can also occur via the round and oval windows from the middle ear. Any
hearing decit caused by hair cell loss is usually permanent as the organ of Corti cannot
spontaneously regenerate hair cells
Temporary Hearing Loss
Agents aecting ion transport across epithelia, such as loop diuretics, cause oedema of the
stria vascularis. is alters the endolymph composition, resulting in a reduction in endocochlear potential (EP) leading to a TTS associated with a pan-frequency HL. e eects are
completely reversible once administration is stopped, although this may take several days.
When administered in high doses (i.e. 2–5 g/day), salicylates penetrate the blood-perilymph
barrier easily and inhibit the activity of outer hair cells (OHCs). e degree of HL is directly
proportional to the serum and perilymph drug concentration. Quinines and their derivatives can act as nicotinic acetylcholine receptor antagonists, disrupting synaptic transmission on inner and outer hair cells and/or spiral ganglion neurons. Vestibular hair cells may
be aected too, resulting in vertiginous symptoms.
Permanent Hearing Loss and Balance
Aminoglycosides
All aminoglycosides are potentially both cochleo- and vestibulo-toxic, but they vary in their
site of maximal eect, for reasons unknown.
Within the inner ear, aminoglycosides specically target hair cells blocking the mechanotransduction channels at the tips of stereocilia. Apoptosis occurs once a certain concentration of the drug has been reached within the cell. Reactive oxygen free radical production
may also play a role. OHC loss occurs rst; inner hair cells are relatively spared but can be
lost later. Subsequently, the spiral ganglion neurons that supply aerent innervation to the
hair cells are lost.
In the vestibule hair cell loss occurs rst in the central epithelia of the utricular and saccular
maculae, before spreading towards the peripheries.
Toxic eects usually appear aer repeated systemic treatment, although even a single topical application to the middle ear cavity can initiate damage. e damage progresses even
aer administration has ceased and symptoms may not present until aer the patient has
completed a course of the oending drug. It must be stressed that vestibular symptoms with
clinically used drugs such as gentamicin precede HL eects, and should be sought rst.
Bilateral vestibular damage results in oscillopsia and severe unsteadiness that is worse in the
dark. Hearing impairment initially occurs in the high frequencies and progresses to include
successively lower frequencies.
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ANATOMY AND PHYSIOLOGY OF HEARINGSENSORINEURAL HEARING LOSS
Table 14.2 The effects of medication on sensorineural hearing loss
Mechanism of action
Classication Compounds
Aminoglycoside
antibiotics
Most cochleotoxic = neomycin,
followed by gentamicin,
kanamycin, and tobramycin
Least cochleotoxic = amikacin and
netilmicin
Most vestibulotoxic =
streptomycin and gentamicin
and notes
Blockade of mechano-
transduction channels at
stereocilia tips, apoptosis of hair
cells, and production of reactive
oxygen free radicals
Mutations in the gene that
encodes 12s ribosomal
mitochondrial DNA, including the
‘A1555G’ mutation (prevalence
0.19–1% prevalence) severely
increases cochlear but not
vestibular susceptibility to
aminoglycoside toxicity
Impaired renal function increases
susceptibility to damage
Loop diuretics Bumetanide, ethacrynic acid,
frusemide (furosemide),
piretanide
Disrupt ion transport across
epithelia within the inner ear,
resulting in oedema of stria
vascularis and reversible TTS and
pan-frequency hearing loss
Effects are reversible once
administration is stopped,
although it may take several days
Macrolide antibiotics Erythromycin, azithromycin,
Similar to that of loop diuretics
clarithromycin
Other antibiotics Ampicillin, capreomycin,
Specic mechanism unknown
chloramphenicol, colistin
(polymyxin E), minocycline,
polymyxin B, rifampicin,
vancomycin, viomycin
Antitumor agents Cisplatin (cis-platinum),
carboplatin, oxaliplatin
(carboplatin and oxaliplatin are
less ototoxic than cisplatin)
Similar to that of aminoglycosides,
but has additional effects on
spiral ganglion cells and causes
atrophy of stria vascularis
Actinomycin, bleomycin, nitrogen
mustards (e.g. mustine),
misonidazole
Anti-inammatory
agents
Salicylate (aspirin) Direct inhibition of OHCs causes
Fenoprofen, ibuprofen,
reversible TTS
indomethacin, naproxen,
phenylbutazone,
Antimalarials Quinine, chloroquine Nicotinic acetylcholine receptor
antagonism causing disruption
of synaptic transmission within
inner ear cells and reversible TTS
May also cause vertigo
Iron chelators Desferrioxamine Specic mechanism unknown
Beta blockers Practolol, propranolol Specic mechanism unknown
Contraceptives Medroxyprogesterone Specic mechanism unknown
Industrial chemicals Trimethyltin, toluene,
trichloroethylene, styrene, xylene
Note: OHC, outer hair cell; TTS, temporary threshold shift.
Loss of OHCs with predilection for
middle and apical turns of cochlea
82 e Ear
14. SENSORINEURAL HEARING LOSS
TINNITUS AND HYPERACUSIS
e dose, drug, route, and duration of administration can inuence the degree of impairment. Standard dosing safe levels are not calibrated for vestibular toxicity. Impaired renal
function increases susceptibility to damage. Mutations in the gene that encodes 12s ribosomal mitochondrial DNA, including the ‘A1555G’ mutation (adenosine to guanosine substitution at base position 1555), severely increases cochlear but not vestibular susceptibility to
aminoglycoside toxicity. Estimates of the prevalence of A1555G mutation vary from 0.19 to
1% in dierent ethnic populations, with a carrier rate of 17%.
Cisplatin
A degree of hearing impairment aects >60% of patients treated with current protocols of cisplatin. HL is bilateral, rst in the extended high frequencies then progresses with cumulative
doses into the speech frequencies. HL can progress aer administration has stopped, possibly
due to prolonged retention of platinum in the body. e pattern of cochlear hair cell damage
greatly resembles that of aminoglycosides, although vestibular hair cells are relatively spared.
Cisplatin additionally aects the spiral ganglion cells, causes atrophy of the stria vascularis,
and increases the susceptibility to NIHL for several years aer treatment has nished.
ere are many proposed systems for monitoring hearing during platinum chemotherapy
treatment, though adherence is sparse. e minimum requirement (adults) is for a baseline
audiogram, retest if complaint of HL arises, and exit audiometry. In children more regular
age-appropriate testing is required during treatment. Detection of HL is increased with more
frequent testing and when extended high-frequency audiometry (10–16 kHz) is used.
KEY POINTS
• Approximately 50% of idiopathic SSNHL cases will improve spontaneously; oral or IT
steroids have limited conclusive evidence of efcacy, but if used should be initiated as
soon as possible.
• In the assessment of NIHL one must consider the individual contributions of age and
idiopathic and noise-related components that can result in HL.
• AHRL is inevitable, and it can be associated with increased social isolation and
impaired cognitive functioning.
• An underlying genetic cause should be considered in younger patients presenting with
bilateral SNHL.
• Ototoxic agents exert their effect on the inner ear via different pathways to cause
disruption of the EP and damage and apoptosis of hair cells and spiral ganglion cells.
• The mainstay of assessment of SNHL is to identify any potentially reversible causes.
The general treatment is with hearing amplication and specic therapy for any
accompanying physical or psychosocial symptoms.
15. TINNITUS AND HYPERACUSIS
Denitions and Classication
Tinnitus is defined as the conscious perception of an auditory sensation in the absence
of a corresponding external stimulus. Most tinnitus comprises simple sounds like whistling, buzzing, humming, or ringing, but more complex sounds such as distant voices or
even music are occasionally reported. Somatosensory tinnitus is a subtype in which the
percept can be altered by physical contact or movement, particularly of the cervical spine
or jaw. Some tinnitus has a rhythmical nature, which may be synchronous with the heartbeat in which case it is dened as pulsatile tinnitus (Table 15.1) and a vascular origin is
ANATOMY AND PHYSIOLOGY OF HEARINGTINNITUS AND HYPERACUSIS
Table 15.1 Pathological causes of pulsatile tinnitus
Type of pathology Specic pathology
Vascular Atherosclerotic carotid artery disease
Arterial Arteriovenous stula
Arteriovenous malformation
Intracranial aneurysm
Dissection of the carotid artery
Venous Jugular bulb abnormalities
Dural venous sinus stenosis
Abnormal condylar or mastoid emissary veins
Microvascular Glomus tumour
Meningioma of middle ear
Cavernous haemangioma
Circulatory Increased cardiac output (anaemia, thyrotoxicosis,
pregnancy)
Aortic murmurs
Perceptual Conductive hearing loss
Other Idiopathic intracranial hypertension
Superior semicircular canal dehiscence syndrome
likely. Pulse-asynchronous rhythmical tinnitus may have an underlying muscular origin,
arising from myoclonus of palatal or intratympanic muscles. Most tinnitus is subjective
in that it can only be detected by the aected person. Occasionally, particularly with some
types of rhythmical tinnitus, it is possible for others to hear a sound and in this case the
tinnitus is objective. Disorders of sound tolerance are subdivided: hyperacusis is dislike of
all sounds above a certain intensity; misophonia is dislike of particular sounds, irrespective of the level of those sounds; and phonophobia is fear of particular sounds. Confusingly,
hyperacusis is also used as an umbrella term for all disorders of sound tolerance.
Epidemiology
Estimates of tinnitus prevalence vary from 5.1–42.7% but a large UK study suggested a
point prevalence of 10.1% in adults. Approximately 1 in 30 adults have tinnitus that is
moderately annoying and 1 in 200 have tinnitus that severely aects their ability to lead
a normal life. Prevalence increases with age up to the seventh decade of life: some studies
show the prevalence continuing to increase thereaer, whereas others show it plateauing or
even dropping. Tinnitus prevalence is similar in men and women. Children are less likely
than adults to volunteer that they have tinnitus but when asked directly, the prevalence
is not dissimilar to that in adults. Tinnitus is more common in people with hearing loss,
but the degree of hearing loss corresponds poorly with the severity of tinnitus. About 1
in 10 people with tinnitus have normal hearing as measured by pure-tone audiometry
and conversely, tinnitus can also exist aer division of the auditory nerve. ere are few
longitudinal studies of tinnitus, but those that are available suggest that for most people
the natural history is for tinnitus to become less intrusive with time. e prevalence of
hyperacusis is unclear.
Pathophysiology
ere are multiple theories regarding the underlying cause of tinnitus and it is possible that
there are multiple mechanisms. It is suggested that tinnitus emergence is a two-stage process:
an initial trigger, which may be in the peripheral or central auditory systems, or even from
parts of the brain outside the classical auditory pathways. is is followed by changes in the
central auditory system and associated non-auditory areas of the brain, particularly areas
84 e Ear
15. TINNITUS AND HYPERACUSIS
TINNITUS AND HYPERACUSIS
involved with emotion and arousal, resulting in the persistence and distress of the symptom. Mechanisms that have been proposed include reorganisation of the brain’s tonotopic
map following deaerentation, increased spontaneous neuronal ring, increased neuronal
synchrony, failure of inhibitory pathways, or errors of predictive coding. e initial trigger
can be any form of hearing loss including noise-induced hearing loss, presbycusis, or sensorineural loss secondary to administration of ototoxic drugs. Many patients, however, report
that their hearing did not change; instead, they feel that the trigger was a life event such as a
bereavement or nancial worry. Other triggers that have been suggested are somatosensory
triggers such as temporomandibular joint dysfunction.
Associations
Tinnitus is part of the symptom complex in Meniere’s disease, otosclerosis, and vestibular
schwannoma. Tinnitus and disorders of sound tolerance are frequently comorbid. Tinnitus
may be associated with psychological illness, particularly anxiety and depression.
Clinical Assessment
A tinn itus patient should have a deta iled neurotological history taken. e character of the t innitus should be assessed to ascertain whether it is pulsatile or non-pulsatile. Evaluating the impact
of the symptom should include questions on mood, sleep, and concentration. Examination is
oen normal, but it is important to exclude specic neu rotological pathologies. With rhythmica l
tinnitus, auscultation of the head and neck should be performed. If pulsatile tinnitus diminishes
with compression of the ipsilateral jugular vein, this points to a venous cause. With pulse-asynchronous pulsatile tinnitus, the pharynx should be checked for myoclonic contractions.
Investigations
Audiometry
Pure-tone audiometry should be conducted and, as many people with tinnitus report that
their ears feel full or blocked, tympanometry is useful. Specialist long time-base tympanometry may be helpful in reaching a diagnosis of middle ear myoclonus. Trying to audiometrically match the pitch and tone of tinnitus is dicult, adds little to the subsequent
management, and is unnecessary in most cases.
Imaging
For non-pulsatile tinnitus, magnetic resonance imaging (MRI) scanning should be considered if the tinnitus is unilateral, associated with a signicantly asymmetric audiogram
(asymmetry on pure-tone audiometry of 15 dB or more at any two adjacent test frequencies,
using test frequencies of 0.5, 1, 2, 4, and 8 kHz; NICE 2020) or if there are abnormal neurological symptoms or signs. Investigating pulsatile tinnitus is more complex and depends
in part on local expertise and availability. Investigative algorithms may include MRI, MR
angiography, computed tomography (CT), CT angiography or conventional angiography,
and lumbar puncture with cerebrospinal uid (CSF) pressure measurements.
Haematological Testing
Blood tests rarely add useful information in the tinnitus clinic and should be avoided unless
there is good clinical indication. Haemoglobin, pregnancy, and/or thyroid function tests may
be needed if the patient has pulsatile tinnitus secondary to a hyperdynamic circulation. ere
is some weak evidence that tinnitus is more common in people with vitamin B deciencies, so
this should be checked in people with restrictive diets or malabsorption syndromes.
Questionnaires
ere is no current objective measure or biomarker for tinnitus. Health care questionnaires
are therefore used to estimate tinnitus severity. Tinnitus-specic questionnaires include
the Tinnitus Questionnaire, the Tinnitus Handicap Inventory, and the Tinnitus Functional
Index. Questionnaires may also be used to assess comorbid conditions including anxiety,
depression, and insomnia.
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ANATOMY AND PHYSIOLOGY OF HEARINGTINNITUS AND HYPERACUSIS
Treatment
If the clinical assessment has revealed that the tinnitus is associated with a specic condition further management may be dictated by that condition. For example, a patient with
otosclerosis may need to be counselled regarding the options of watchful waiting, uoride
treatment, hearing aids, or stapes surgery. Surgery for otosclerosis is generally helpful for
associated tinnitus, particularly when the hearing is improved. Surgery also has a role for
those with tinnitus associated with severe/profound hearing loss: cochlear implantation
generally improves the tinnitus though this is not universal and there is a small risk of the
procedure triggering tinnitus or worsening pre-existing tinnitus.
Investigat ion of pulse-synch ronous tinnitus may reveal a treatable cause such as a vascular tumor,
carotid artery stenosis, arteriovenous stula, raised intracranial pressure, or venous obstruction
or abnormality. Further treatment will then be directed as necessary to rectify that problem.
Investigation of pulse-asynchronous pulsatile tinnitus oen draws a blank. If a particular
pathology is proven or strongly suspected, specic treatments are available including division of the tensor tympani and stapedius tendons for intratympanic myoclonus or Botox
injection of the relevant muscles for palatal myoclonus. ese treatments have signicant
risks attached and in the case of intratympanic tendon division are irreversible. Surgery
should therefore probably be best regarded as an option only aer careful consideration.
Most tinnitus is non-pulsatile and not associated with any specic condition. No drug therapy
is currently recommended, but helpful management strategies are available. ese fall into two
broad categories: audiologically based management and psychologically based management.
Audiological management is a combination of addressing any associated hearing loss with
hearing aids, assistive listening devices or, if necessary, cochlear implants, using sound
therapy, explanation, education and counselling, relaxation training and, if needed, advice
regarding sleep. Various protocols have been developed using these principles in a structured
way, including tinnitus retraining therapy, progressive tinnitus management and tinnitus
activities treatment. ere is a modest evidence base supporting these approaches.
Hearing Improvement
e rationale for addressing any hearing loss from the outset is threefold. Firstly, most
tinnitus clinicians feel that hearing loss causes people to strain to listen, which makes any
tinnitus seem louder. Correcting the hearing loss reverses this process. Secondly, if the person can hear better they pick up more environmental sound, which tends to distract their
brains from the tinnitus. Finally, improving the hearing allows people to interact with the
education and counselling modules of the therapy more eectively.
Sound Therapy
ere are many options for delivering sound therapy: simply opening a bedroom window can
allow sound from the outside world into an otherwise quiet domestic environment; sound can
be generated by a stand-alone electronic device; there are tinnitus apps for mobile phones or
computers; sound from electric fans, sh tank aerators, or indoor water features can be used;
and the tinnitus-aected person can wear ear-level devices resembling small hearing aids that
produce wideband sound. e consensus is that the sound used should be something that the
person nds neither intrusive nor too interesting and should be delivered at a low level that
mixes with the tinnitus perception rather than tries to mask it. When used at nighttime, sound
therapy can be delivered directly into the bedroom environment or can be delivered more
locally via pillow speakers, a small loudspeaker under the pillow, or via Bluetooth headbands.
If hyperacusis is the main problem, desensitisation using sound therapy is oen helpful.
Combination Devices
All the major hearing aid manufacturers now oer devices that combine hearing aids and
sound therapy devices in the same unit with the aim that the device is normally set to the
86 e Ear
15. TINNITUS AND HYPERACUSIS
TINNITUS AND HYPERACUSIS
hearing aid setting, but if the person is in a quiet environment they can switch to the sound
therapy program.
Psychological Treatments
e treatment with the be st evidence base for ec acy in manag ing tinnitu s is cognitive behaviour therapy (CBT). Newer psychological treatment modalities including mindfulness-based
cognitive therapy (MBCT), mindfulness-based stress reduction (MBSR), or acceptance and
commitment therapy (ACT) also seem helpful. In the United Kingdom there is a dearth of
audiologically literate psychologists to deliver such treatments, and alternative care pathways
are being investigated including educating audiologists to provide CBT or using the Internet
to deliver CBT.
Other Treatments
Although there is no drug approved specically for the management of tinnitus, drugs have
a role in the management of comorbid conditions such as anxiety and depression. Physical
therapies may have a role in the management of somatosensory tinnitus. Complementary and
alternative medicine treatments do not have any specic anti-tinnitus eect but can improve
relaxation and general well-being. Various experimental treatments are being explored, particularly neuromodulation and repetitive transcranial magnetic stimulation (rTMS).
KEY POINTS
• Tinnitus is the conscious perception of an auditory sensation in the absence of a
corresponding external stimulus. Hyperacusis is both a dislike of sounds above a
certain intensity and a blanket term for several forms of impaired sound tolerance.
• Modern models suggest that tinnitus is due to increased awareness of spontaneous
electrical activity in the auditory system. Although changes in the auditory periphery
can trigger tinnitus, the processes that cause the symptom to perpetuate and become
distressing occur in the central auditory pathways and in associated brain regions,
particularly the limbic system.
• Tinnitus is more common in people with a hearing loss, but the degree of hearing
impairment correlates poorly with tinnitus severity. About 1 in 10 people presenting
with tinnitus have a normal audiogram. Tinnitus can exist after division of the auditory
nerve.
• Patients with tinnitus and/or hyperacusis should undergo a basic audiological assessment.
Further investigation should be undertaken in the those with pulsatile tinnitus, objectively
audible tinnitus, unilateral tinnitus, tinnitus in association with asymmetric hearing loss,
and tinnitus in association with neurological symptoms and/or signs.
• Patients are often given negative counselling and being told that nothing can be
done for tinnitus. While a cure for tinnitus remains elusive, there are many helpful
management strategies, particularly sound-based therapies, counselling, and
psychological therapies.
Further Reading
McFerran D, Hoare DJ, Carr S, Ray J, Stockdale D. Tinnitus services in the United Kingdom:
a survey of patient experiences. BMC Health Serv Res. 2018; 18(1):110. doi:10.1186/
s12913-018-2914-3
McFerran DJ, Stockdale D, Holme R, Large CH, Baguley DM. Why is there no cure for tin-
nitus? Front Neurosci. 2019; 13:802. doi:10.3389/fnins.2019.00802
Phillips JS, McFerran DJ, Hall DA, Hoare DJ. e natural history of subjective tinnitus in
adults: a systematic review and meta-analysis of no-intervention periods in controlled
trials. Laryngoscope. 2018; 128(1):217–227. doi:10.1002/lary.26607
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