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ANATOMY AND PHYSIOLOGY OF HEARINGCOCHLEAR IMPLANTS AND AUDITORY BRAINSTEM IMPLANTS
y
Speech processor
Transmitter
Microphone
Figure 18.1 Components of the cochlear implant. (1) The microphone picks up the acoustic
signal. (2) The sound processor converts the microphone output to an electrical signals (3) headpiece with a transmitting coil held in place by a magnet and uses radio frequency to transmit the
signal transcutaneously. (4) The receiver/stimulator decodes information from the transmitter and
generates electrical stimuli and (5) the electrode array stimulates auditory neurons.
Receiver/stimulator
Electrode arra
Criteria for Implantation
Implantation criteria vary between countries. UK criteria were updated by the National
Institute of Health and Care Excellence in March 2019:
Prognostic Factors
In children, the most important prognostic factor is age at implantation with earlier age associated with better hearing outcomes. ere is growing evidence that CIs should be provided
prior to the age of 12 months in congenital deafness. In adults, pre-lingual onset of deafness
and later age at implantation are negative prognostic factors. Some studies have shown that
longer duration of deafness is associated with poorer outcome in adults. Other factors that
98 e Ear
Cochlear implantation can be considered for individuals with bilateral severe to pro-
•
found hearing loss who do not receive adequate benet from hearing aids.
Unilateral implantation is recommended in adults.
•
Bilateral implantation in children or in adults who are blind or have other disabilities
•
that increase their reliance on auditory stimuli.
Severe to profound deafness is dened as pure-tone audiometric threshold ≥80dB
•
hearing level (HL) at two or more frequencies (500, 1000, 2000, 3000 and 4000 Hz)
bilaterally without hearing aids.
Trial of hearing aids should occur for at least 3 months. Adequate benet from hearing
•
aids is dened as the following:
For adults, a phoneme score of 50% or greater on the Arthur Boothroyd word test
•
presented at 70dBA
For children, speech, language and listening skills appropriate to age, develop-
•
mental stage and cognitive ability
18. COCHLEAR IMPL ANTS AND AUDITORY BRAINSTEM IMPLANTS
COCHLEAR IMPLANTS AND AUDITORY BRAINSTEM IMPLANTS
may inuence outcomes in children and adults include learning disability, communication
environment and aetiology of deafness (e.g. better in Meniere’s disease but worse in meningitis/temporal bone fracture).
Assessment
Assessment should be performed by a multidisciplinary team including but not limited
to surgeons, audiologists and rehabilitationists. It is crucial that patients have realistic
expectations of their hearing outcome and adequate pre-operative counselling is necessary. Behavioural audiological assessment involves age appropriate assessment of hearing
thresholds and in adults also includes word recognition tests. is can be supplemented with
objective measurements including otoacoustic emissions (assessment of auditory neuropathy spectrum disorder; see Chapter 16), auditory brainstem responses (ABRs; for hearing
threshold estimation; see Chapter 4) and auditory cortical responses (for assessing benet
from hearing aids; see Chapter 4). is is particularly important in young children and in
patients with suspected non-organic hearing loss. Transtympanic electrocochleography is
occasionally used in patients in whom there is concern about the presence/function of the
cochlear nerve.
Pre-operative imaging may include magnetic resonance imaging (MRI) and/or computed tomography (CT) and should be used to identify inner ear abnormalities and
for surgical planning. MRI should be performed in children with congenital deafness
to ensure there is a cochlear nerve of normal diameter; additional CT imaging is not
required in most cases.
Oen the better-hearing/better-aided ear is chosen for implantation in adults due to theoretically better survival of the peripheral and central auditory pathways on this side. Many
patients however, will prefer to have their worse ear implanted so that they can continue
to wear a hearing aid in their better ear. Vestibular function testing should be considered
in patients with imbalance. e ear with poorer peripheral vestibular function is generally
preferred for implantation to reduce post-operative vestibular disturbance.
Surgery
Surgery should be performed with strict aseptic technique and a facial nerve monitor should
be used. Typically, a postauricular incision is made, an anteriorly/superiorly based periosteal
ap is raised and small cortical mastoidectomy is performed. A posterior tympanotomy is
then formed to gain access to the round window (RW) and reduce the RW niche. Some
surgeons drill a bed for the implant package whilst others place it in a subperiosteal pocket.
Electrode insertion is performed through the RW membrane or through a cochleostomy
depending on the electrode and surgeon preference. A so tissue seal is oen placed around
the electrode at the promontory and the wound is closed in multiple layers. Intraoperatively
the implant may be assessed for faults and for correct placement using electrophysiological testing, X-ray or even CT. Chronic middle ear disease should be addressed prior to CI
and may necessitate tympanoplasty for perforations and blind sac closure for cholesteatoma/
mastoid cavities.
Many surgeons routinely use hearing preser vation techniques to conserve inner ear elements.
Meaningful preservation of hearing is usually only possible if preoperative low-frequency
thresholds are around 70dB or better. is allows electroacoustic stimulation, through a
hearing aid for residual hearing and electrical stimulation from the CI. Other advantages
to preserving inner ear residual function including reduced post-operative imbalance and
opening the possibility of the ear beneting from future hearing regeneration therapies. ‘So
surgery’ techniques include inserting the electrode through steroids or hyaluronate, avoiding suction near the cochlea and performing a slow insertion over minutes. ere is some
evidence that use of steroids either pre-operatively or post-operatively improves hearing
outcome. Recently, intraoperative electrocochleography has been used to provide real-time
feedback on basilar membrane trauma during insertion.
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ANATOMY AND PHYSIOLOGY OF HEARINGCOCHLEAR IMPLANTS AND AUDITORY BRAINSTEM IMPLANTS
Complications
Complications of CI surgery include standard complications of mastoid surgery (see
Chapter 10). In addition, patients must be warned of the risk of device failure and of menin-
gitis. For the latter reason, patients should have the 23-valent polysaccharide pneumococcal
vaccination (given aer the age of 2) in addition to the childhood meningitis immunisation programme. Intraoperative cerebrospinal uid (CSF) leak can occur when making the
cochleostomy or RW opening in patients with inner ear malformations but can be managed
by raising the head of the bed and inserting the electrode with a so tissue seal around it;
lumbar drainage is rarely required. Occasionally the electrode cannot be inserted fully due
to cochlear brosis/ossication, e.g. due to meningitis or otosclerosis. In some cases, it is
necessary to drill out the basal turn of the cochlea or even insert a split electrode for which
an additional channel is drilled into the middle turn of the cochlea. Tip folds over of the
electrode in the cochlea and facial nerve stimulation from the CI are complications that can
usually be managed by altering the stimulation settings for the CI. Some patients also experience chronic pain following surgery, which rarely necessitates device explantation. ere is
a risk of magnet displacement with MRI and the make of implant should always be checked
and appropriate precautions taken prior to such imaging.
Post-Operative Rehabilitation and Outcomes
e implant ‘switch-on’ usually occurs 2–6 weeks aer surgery. Patients have several
appointments for programming the implant and for auditory rehabilitation in the rst few
months aer surgery. In adults, peak performance is usually reached within 6–12 months. In
general, whilst hearing outcomes are usually excellent from CIs allowing ‘open set’ speech
perception, there can be signicant variability in outcomes. Speech-in-noise perception is
generally limited and adults oen struggle with music appreciation. ere is evidence that
bilateral implantation and bimodal hearing (hearing aid in one ear and CI in the other ear)
are associated with better sound localisation and speech-in-noise perception.
Future Developments
Extended criteria for CIs include single-sided deafness and management of tinnitus in
patients with severe to profound hearing loss; these indications are currently not funded
in the United Kingdom. Research is ongoing into the use of optical stimulation for CI
(rather than electrical stimulation) to allow more focused stimulation of auditory neurons,
robotic insertion of electrodes to minimise insertion trauma and the use of neurotrophins
on electrodes to promote growth of nerve endings. ere is also growing interest in the use
objective measurements, including electrophysiology and imaging techniques, to guide CI
programming.
Auditory Brainstem Implants
Indications
Auditory brainstem implants (ABIs) are used for hearing restoration in patients with severe
to profound hearing loss when a CI is not possible. Potential candidates include
Adults with bilateral vestibular schwannoma due to neurobromatosis type 2 (NF2),
•
undergoing tumour resection, in whom cochlear nerve preservation is not possible;
the function of the cochlear nerve can be checked during surgery with electrically
evoked ABR/compound action potential
Adults with cochlear ossication due to meningitis, labyrinthitis, fractures or
•
otosclerosis
Children with bilateral cochlear aplasia or bilateral auditory nerve aplasia or dysplasia
•
Similar to CIs, patients require extensive multidisciplinary assessment and counselling prior
to surgery. ey also require careful setting up of the device and a rehabilitation programme
to help with speech understanding.
100 e Ear
18. COCHLEAR IMPL ANTS AND AUDITORY BRAINSTEM IMPLANTS
EAR TRAUMA
Surgery
e ABI has similar components to the CI; the main dierence is that the electrode contacts are
on a at paddle. e retrosigmoid or translabyrinthine approaches are typically used for access
to the brainstem and the electrode paddle is placed on the lateral recess of the fourth ventricle
adjacent to the cochlear nucleus. Paddle position can be optimised based on implant evoked
ABRs. e facial and glossopharyngeal nerves are monitored for non-auditory stimulation.
Similarly, the vagus nerve can be monitored through the electrocardiogram (ECG). Switch
on is typically performed with the patient nil by mouth and with anaesthetic personnel and
equipment available in case of nonauditory stimulation causing cardiac rhythm disturbance.
Outcomes
Hearing outcomes from ABI are highly variable and are certainly inferior to CI. In addition, it takes many years for patients to reach peak performance. In most cases, they allow
awareness of sounds and an aid to lipreading, with the minority of cases achieving open-set
speech perception. Outcomes in adults without tumours are generally superior to that in
NF2 patients (see Chapter 22 for further details on outcomes in NF2).
KEY POINTS
• CIs may be considered in patients with severe to profound hearing loss that fulll NICE
20192 guidance.
• In children, an early age at implantation and in adults shorter duration of profound
deafness are associated with better-hearing outcomes.
• A positive communication environment is associated with better outcomes.
• ABI may be used for hearing restoration in cases of severe to profound hearing loss
where CI is not possible, most commonly in patients with NF2.
• ABI usually enables awareness of sounds, aids lipreading and rarely allows open-set
speech perception.
Further Reading
1. Tysome J, Axon P, Donnelly N et al. English consensus protocol evaluating candidacy for auditory brainstem and cochlear implantation in neurobromatosis type 2.
Otology & Neurotology: 2013 (34) 1743–1747. doi: 10.1097/MAO.0b013e3182a1a8b4.
2. National Institute for Health and Care Excellence. Cochlear implants for children and
adults w ith severe to profound deaf ness. 2020. Availa ble from: https://www.nice.org.uk/
guidance/ta566. (Accessed 10 July 2020.)
3. Taylor & Francis Online. Cochlear Implants International. 2020. Available from: https://
www.tandfonline.com/toc/ycii20/17/sup1. (Accessed 10 July 2020.)
19. EAR TRAUMA
1
Auricular Haematoma and Cauliower Ear
Auricular haematoma is caused by direct trauma to the pinna. In children there is a strong
association with non-accidental injury. Tearing of perforating vessels causes extravasation
creating an intracartilaginous space. ey are painful, tender and uctuant.
Haematoma aspiration must be performed within 48 hours and followed by compression.
ere is a high recurrence rate. A delayed presentation, recurrence or a requirement to
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ANATOMY AND PHYSIOLOGY OF HEARINGEAR TRAUMA
return urgently to contact sports mandates a formal procedure. Numerous methods have
been described but reliable results are only achieved if granulation tissue is curetted and post
drainage compression (e.g. dental rolls or silastic splints) is used.
Inadequate drainage results in new irregular cartilage formation (cauliower ear) and poor
cosmesis.
Caustic Injury – Button Batteries
Caustic injuries to the external canal and drum perforation from button batteries require
emergency treatment. Eardrops must not be used. Extensive so tissue and bone necrosis is
possible. Emergency removal, irrigation and debridement should be performed, but repair
or graing should be delayed.
Traumatic Tympanic Membrane Perforation
is is usually caused by slap injuries, penetrating objects and barotrauma.
Careful otomicroscopy with removal of any foreign body is required. A conductive hearing
loss is typical.
Antibiotic drops should only be used if there is evidence of infection.
e application of cigarette paper or Gelfoam over the perforation increases the speed but
not the incidence of spontaneous healing, which is greater than 80%. Formal repair should be
delayed until aer 3 months and has a better success rate than for perforations associated with
otitis media. Caustic and blast injuries have poorer outcomes, the worst being welding injuries.
Ossicular Trauma
Skull trauma is the most common cause. About two-thirds occur without a concomitant
temporal bone fracture. Dislocation of the incus is the most common injury. Isolated malleus
fracture may follow sudden pressurisation in the canal.
A high-denition computed tomography (CT) scan is recommended. ree-dimensional
(3D) imaging and virtual endoscopy will enable an accurate diagnosis in most cases.
Audiometry will demonstrate a conductive, or mixed, hearing loss in the acute phase.
Transmission of force through the ossicular chain to the inner ear may cause a sensorineural
component. Both may improve considerably following spontaneous clearance of the haemotympanum, healing of the tympanic membrane, scarring around the ossicles and improvement of cochlear concussion.
Reparative surgery should be delayed until 3 months. Aiding may be an appropriate
alternative.
Inner Ear Trauma (without Fracture)
(Inner Ear Concussion, Cochlear Concussion, Inner Ear Concussive Syndrome,
Mild Traumatic Brain Injury)
Minor head injuries are extremely common. Concussion (synonymous with mild traumatic
brain injury) is a brief loss of consciousness, or any change in mental state, at the time of the
accident. A subjective transient hearing loss occurs in 52% of cases lasting for up to 2 days, but
there is little evidence for permanent loss. Tinnitus and hyperacusis are common. True vertigo
is the only denite otological symptom occurring in 25% of cases, almost always disappearing
within 10 days. Non-specic dizziness, oen postural perceptive, occurs in many more cases.
During the rst week symptoms include headaches, dizziness, fatigue, memory decits, anxiety and depression. Up to 40% of patients have residual symptoms 1 year later. Positional
vertigo is common. Multiple repositioning manoeuvres are required in 67% of those with
post head injury benign paroxysmal positional vertigo (BPPV) (compared with 14% of those
with idiopathic BPPV).
102 e Ear
19. EAR TRAUMA
EAR TRAUMA
Treatment is supportive; there is no evidence to support the use of steroids. Rare sequelae
include perilymphatic stula (PLF), progressive sensorineural deafness (probably of autoimmune aetiology) and delayed endolymphatic hydrops.
Inner Ear Trauma and Temporal Bone Fracture
2
Always evaluate for other intracranial and cervical spine injuries in these cases.
Temporal bone fractures are traditionally described as longitudinal or transverse. Otic capsule ‘violating’ or ‘sparing’ is a more useful distinction (Figure 19.1) as the serious sequelae
of facial nerve paralysis, cerebrospinal uid (CSF) leak and profound hearing loss are twice,
four times and seven times, respectively, more likely in the former.
Any pattern of loss immediate/delayed or transient/permanent/progressive may be seen. A
conductive hearing loss is common but usually resolves. A sensorineural loss, usually at and
above 4kHz, is oen found. e degree of hearing loss is proportional to the degree of head
injury; complete loss is common.
Post-traumatic vertigo is usually short-lived in otic capsule–sparing cases. In violating cases
resolution is by central adaptation, which may take up to 12 months.
A complete neuro-otological examination should include the conscious level, cranial nerve
function (especially facial nerve), clinical testing of hearing (including tuning forks), audiometry, balance, gait and cerebellar function and should be performed as soon as the patient’s
general state permits. Mastoid bruising (Battle’s sign) may indicate an underlying fracture.
e meatus should not be irrigated, and microsuction should be performed only if infection
is suspected. Any so tissue should be le alone. Packing of the meatus is only indicated if
there is uncontrollable haemorrhage. Avoid packing material with a radiopaque marker as it
may interfere with subsequent imaging.
A high-denition temporal bone scan should be performed. Where hearing loss or vertigo are
evident, but with no fracture on CT, T1-weighted magnetic resonance imaging (MRI) may demonstrate a hyperintense signal in the labyrinth indicative of haemorrhage, and it may also identify temporal lobe contusion. Gadolinium-enhanced MRI of the facial nerve, or angiography
to exclude vascular injury, more accurately assesses the degree of damage to these structures.
Figure 19.1 Axial CT scan showing (a) otic capsule sparing and (b) otic capsule violating temporal
bone fractures.
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ANATOMY AND PHYSIOLOGY OF HEARINGEAR TRAUMA
e use of steroids is associated with increased mortality when there is concomitant traumatic brain injury, so it should not be used routinely.
In rare cases of bilateral temporal bone fracture, urgent hearing evaluation is required as
emergency cochlear implantation may be required prior to the onset of reparative cochlear
brosis.
Facial Palsy
3
Facial palsy complicates 7% of temporal bone fractures: 66% occur at the geniculate ganglion and 20% at the second genu, 8% in the tympanic and 6% in the mastoid segments. It is
important to ascertain whether the onset of a facial palsy was immediate or delayed, and if
partial or complete. e implication of an immediate palsy is that the nerve has been directly
traumatized, impinged or transected. Delayed onset, even if only by a few minutes, or any
residual function, implies neural continuity. Cases where onset cannot be ascertained are
best considered as of immediate onset.
e use of steroids is standard practice in those cases without evidence of signicant traumatic brain injury; the true benet is unknown.
e large majority of incomplete and delayed palsies recover to a House-Brackmann grade I
or II.
Electrophysiological testing is only necessary in cases of immediate complete palsy, or in
those with an uncertain history, where surgical decompression is considered. Without surgery, 50% of complete, and immediate, palsies make a good recovery. e role of surgical
decompression remains controversial. Patients with 90% neural degeneration on electroneuronography, performed 14 days post injury are considered for surgery, although 67% of those
meeting these criteria still recover well without intervention.
If the trauma is clearly localised to the vertical or horizontal portions then a transmastoid
approach provides access from the stylomastoid foramen to the geniculate ganglion. Access
to the intralabyrinthine portion while preserving audiovestibular function is best provided
by the middle fossa approach, but a translabyrinthine approach gives excellent access in
cases where cochlear and vestibular function have been lost.
CSF Leak
CSF leaks complicate 11–33% of temporal bone fractures. Spontaneous closure occurs in
95% within 14 days. e chance of spontaneous closure is proportional to the size of defect.
Recurrent late meningitis may occur many years following the apparent spontaneous healing of a CSF leak. Clear uid found when a grommet is placed for an eusion is a common
presentation. e quoted risk of meningitis secondary to ascending infection varies widely
but is about 2% when the leak has stopped within a week, increasing to about 7% overall with
a persisting leak. is increases to 20% if a concurrent ear infection is present.
Surgical closure is reserved for acute leaks that persist for more than a week, large defects,
and herniation of meninges/brain into underlying spaces where there is a risk of infection.
e location of a defect on a CT scan is not necessarily the site of the leak. Peri-operative
uorescein cisternography may be useful for locating it.
Small tegmen and posterior dural plate defects may be closed via a transmastoid approach.
is approach is familiar to otologists and does not require brain retraction, but it may
require disarticulation of the ossicles to obtain access to a medial defect. Large defects and
revision cases are best treated via the middle fossa; this approach provides excellent access
but requires retraction of the temporal lobe. Repair utilises a multilayered technique with
materials such as fascia, cartilage, bone and brin glue.
Vascular Injury
e risk of vascular injury is higher in more severe skull base fractures, particularly if there
is evidence of otic capsule fracture or cranial nerve palsies. Carotid injury may occur at the
104 e Ear
19. EAR TRAUMA
EAR TRAUMA
junction of the lacerum and cavernous portions or more rarely through the petrous segment.
Carotid artery dissection with a carotid–cavernous stula is a rare consequence as is intimal
damage resulting in aseptic sigmoid sinus thrombosis. e jugular and carotid canals should
be routinely examined on the CT scan with a low threshold for requesting angiography. A
specialist neurosurgical opinion should be sought. Treatment is usually endovascular with a
variety of options including detachable balloons, coils and stents.
Otitic Barotrauma
Middle Ear Barotrauma
Injuries include tympanic membrane perforation, ossicular fracture and/or dislocation and
are common during ight and scuba diving.
ey are caused by an excessive pressure gradient, or a sudden equalization of pressure,
across the tympanic membrane. Rapid alterations in ambient pressure increase the risk.
e middle ear passively vents during ascent, but the introduction of new air, by active
Eustachian tube opening manoeuvres, is required on descent. e more rapid the change
in ambient pressure the higher the risk, which is also increased in those whose middle ears
asymmetrically equalise, experience an inability to voluntarily equalize at sea level (divers)
or have nasal obstruction.
Spontaneous healing, with good hearing outcomes, frequently occurs within the 3 months
following trauma. Corrective surgery should therefore not be performed until aer this time.
e inability to voluntarily equalise middle ear pressure is the best predictor of susceptibility to diving-related trauma but not for ying-related trauma. Tympanometry is not a useful
predictor of susceptibility unless combined with multiple tests.
Proven eective methods of prevention are oral decongestants, regular use of an OtoventTM
nasal balloon, Eustachian tube balloon dilation and nasal septal (vomeroethmoidal) surgery. ‘Flight earplugs’ to decrease the rate of external auditory canal pressure change may
improve the ability to ‘equalise’ middle ear pressures. Topical nasal decongestant sprays are
ineective. Rhinitis should be treated, but individuals should not dive with upper respiratory infections.
Perilymphatic Fistula (PLF)
e most common causes of PLF are barotrauma and head injury, but other causes include
head injury, surgery, congenital anomalies and cholesteatoma.
Many PLFs are dicult to diagnose. Controversy continues regarding the existence of spontaneous stulae. If these do occur, they are rare.
e exact timing of the onset of symptoms relative to an injury is crucial.
A typical history includes diculty equalizing the middle ear pressure during descent, particularly during an upper respiratory infection. ere is a sudden onset of symptoms, usually
vertigo, hearing loss and tinnitus, more rarely Tullio’s phenomenon (third window eect)
and positional vertigo. Mued hearing and occasional, but persistent, disequilibrium may
be the only symptoms. Acute symptoms usually resolve aer several days. Mild disequilibrium (which may change to transient vertigo on straining), mild persistent nausea, motion
intolerance and a subtle sense of ‘not coping’, are the most common symptoms of a chronic
stula. Fluctuating hearing may occur, which might be positional due to air in the labyrinth;
although a convincing sign, it occurs infrequently.
An expectant approach, bed rest and steroids, is only appropriate for acute presentations if
there is minimal hearing loss. Immediate surgery is indicated if there is any signicant hearing loss. Chronic stula symptoms require further evaluation and elective exploration. At
tympanotomy, the oval and round windows should be reinforced with fascia/fat/vein adventitia. Surgical results are poor for hearing restoration, usually due to late presentation or
delayed surgery, but are excellent for balance control.
e Ear 105
ANATOMY AND PHYSIOLOGY OF HEARINGMETABOLIC BONE DISEASE AND SYSTEMIC DISORDERS OF THE TEMPORAL BONE
KEY POINTS
• Removal of button batteries from the external canal is a surgical emergency.
• Surgical repair of the tympanic membrane and/or ossicular chain should not be
performed until 3 months after the injury.
• Immediate-onset facial palsies require investigation and consideration given to surgical
decompression.
• Routine use of steroids increases mortality in acute brain injury.
• Surgery to close a PLF is a surgical emergency for effective hearing restoration.
Delayed intervention is very effective for vestibular symptoms but not hearing
improvement.
Further reading
1. Brodie HA, ompson TC. Management of complications from 820 temporal bone
fractures. Am J Otol. 1997;18:188–197.
2. Darrouzet V, Duclos JY, Liguoro D, Truilhe Y, De Bonls C, Bebear JP. Management
of facial paralysis resulting from temporal bone fractures: Our experience in 115 cases.
Otolaryngol Head Neck Surg. 2001;125:77–84.
3. Hornibrook J. Perilymph stula: y years of controversy. ISRN Otolaryngol. 2012;
2012:1–9.
20. METABOLIC BONE DISEASE AND SYSTEMIC DISORDERS
OF THE TEMPORAL BONE
Metabolic Bone Disease
Fibrous Dysplasia (FD)
In brous dysplasia (FD) normal bone marrow is replaced by proliferating bro-osseous tissue that expands and thins the overlying cortex. FD accounts for 2–3% of all benign bone
tumours and is commonly found in young adults. ere are three types1:
1 Monostotic: single bone disease, craniofacial bones aected in 10–25%
2 Polyostotic: involving several ipsilateral bones, craniofacial bones aected in >50%
3 McCune-Albright syndrome: cafe-au-lait pigmentation, polyostotic FD and hyper-
functioning endocrinopathies
Clinical Features
Cosmetic deformity or mass.
•
Conductive hearing loss (CHL) (stenosis of the external auditory canal [EAC]).
•
Sensorineural hearing loss (SNHL) (compression of internal auditory canal [IAC],
•
invasion of the otic capsule, infection).
Disequilibrium, tinnitus, otorrhea, otalgia, trismus, facial nerve compression
•
(Figure 20.1).
Alkaline phosphatase (ALP) may be raised.
•
Computed tomography (CT) shows ‘ground glass appearance’, asymmetry of the skull,
•
thickening of the cranial cortex and cystic changes.
Macroscopically there is gritty/rubbery, grayish-pink material.
•
106 e Ear
METABOLIC BONE DISEASE AND SYSTEMIC DISORDERS OF THE TEMPORAL BONE
Figure 20.1 Axial computed tomography. Fibrous dysplasia affecting the right petrous temporal
bone and facial nerve in its geniculate and tympanic segments.
19. EAR TRAUMA
Treatment
e majority of craniofacial monostotic FD requires no treatment beyond recognition and
reassurance. Bisphosphonates can be used to relieve bone pain and reduce fracture risk.
Surgical excision can be curative, but risks must be weighed against benets, and craniofacial
monostotic FD oen recurs. Radiation has been reported to cause malignant transformation,
particularly in polyostotic forms.
Osteitis Deformans/Paget’s Disease
Osteitis deformans/Paget’s disease is a systemic disease associated with four genetic mutations (the most common mutation is sequestosome 1). ere is an increasing risk with age.
Characteristics
Normal lamellar patterned bone replaced with disorganised woven pattern.
•
Disease hallmark is bone expansion and deformity of the axial skeleton.
•
Bone pain, pathological fractures.
•
95% have raised ALP.
•
1% undergo malignant transformation.
•
Disease can burn out.
•
Otological Features
40% have hearing loss (HL), such as CHL in low frequencies, progressive SNHL start-
•
ing with high-frequency loss. is is likely as a result of progressive demineralization
of the otic capsule.
20% have tinnitus and vertigo.
•
CT shows ‘osteoporosis circumscripta’, which is radiolucency of the skull, cotton-wool
•
appearance of bone, demineralization of the otic capsule and loss of the distinct bony
contour (Figure 20.2).
1
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