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ANATOMY AND PHYSIOLOGY OF HEARINGMETABOLIC BONE DISEASE AND SYSTEMIC DISORDERS OF THE TEMPORAL BONE
Figure 20.2 Axial computed tomography. Osteitis deformans affecting the occipital and tem-
poral bones. There is loss expansion of the medullary cavity, coarsening of the trabecular pattern
and diffuse sclerosis.
Treatment
Bisphosphonates to prevent bone reabsorption and f ractures (may slow heari ng decline)
•
Non-steroidal anti-inammatory drugs (NSAIDs) for bone pain
•
Hearing aid, cochlear implantation (CI)
•
Middle ear surgery usually ineective
•
Osteogenesis Imperfecta (Brittle-Bone Disease/Lobstein Disease)
Osteogenesis imperfecta (OI) is a connective tissue disorder caused by defects in type I collagen (>95% caused by dominant mutations in COL1A1/COLI1A2) leading to ‘brittle bones’.
Severe/lethal forms are associated with the recessive pattern. ere are ve main subtypes.
Characteristics
Blue sclerae
•
HL (rare in type IV, can be conductive, SNHL or mixed and seen earlier than patients
•
with otosclerosis)
Defective dentition
•
Barrel chest
•
Scoliosis
•
Pathological fractures, joint laxity
•
Growth retardation
•
Radiology
Radiology shows features similar to otosclerosis (but in OI the bony labyrinths are aected
more). ese features include demineralization of the otic capsule (halo or double ring on
CT), enveloped stapes, obliterated inner ear windows, abnormal bone extension involving
semi-circular canals or fallopian canal involvement.
108 e Ear
METABOLIC BONE DISEASE AND SYSTEMIC DISORDERS OF THE TEMPORAL BONE
Treatment
Bisphosphonates increase bone density, reduce bone pain and fracture risk. Stapedectomy is
generally associated with good outcomes, though surgery can be technically more dicult
and outcomes poorer than in otosclerosis. CI is another option.
Osteopetrosis (Albers-Sconberg/Marble Bone Disease)
Osteopetrosis is a rare condition aecting osteoclast activity causing failure of resorption of
calcied cartilage and excessive immature bone formation. is leads to cortical thickening
of the temporal bone (thick skull) and foramina stenosis/compression of corresponding cranial nerves. e condition is more common in Costa Rica and Saudi Arabia.
Characteristics
ere are two types of osteopetrosis:
1 Benign osteopetrosis (normal life span): Oen asymptomatic, requiring no medical
treatment.
2 Malignant osteopetrosis: Oen presenting in infancy with bone marrow failure, neuro-
logical decits, pathological fractures, severe anemia, failure to thrive and optic nerve
atrophy. It is treated with interferon gamma and steroids.
ENT Manifestations
Ear, nose and throat (ENT) manifestations of osteopetrosis include nasal obstruction,
obstructive sleep apnoea, HL (conductive/mixed), otitis media with eusion (OME), thickened tympanic membrane resulting in type B tympanograms (present in 80%), vertigo and
facial nerve paresis. Imaging reveals poorly pneumatised mastoid air cells and narrowing of
the EAC; middle ear space and Eustachian tube; IAC and petrous carotid canal. Treatment
includes regular aural toilet, hearing aids and ventilation tubes.
19. EAR TRAUMA
2
Infections Affecting the Temporal Bone
Mycobacterium Tuberculosis (TB)
Mycobacterium tuberculosis (TB) is rare, <1% of all chronic OME
•
Hematogenous spread or via Eustachian tube
•
Consider if odourless otorrhoea with poor response to antibiotics, multiple perfora-
•
tions/large perforation, pale granulation tissue or patient from TB endemic areas
Facial nerve palsy and early SNHL
•
Send pus/tissue for polymerase chain reaction as microbiology swabs are rarely posi-
•
tive (<20%)
Consider biopsy (granulomata with caseous necrosis)
•
Can cause erosive destruction of the temporal bone
•
Treatment
Treatment is antituberculous treatment for 6 months, consider surgery for diagnosis or
patients failing to respond to medical therapy.
Human Immunodeciency Virus (HIV)
RNA virus, preferentially infects neurons and immune cells, particularly CD4+ T cells.
•
HL occurs in around one-t hird of patients; this may be conductive (OME, ot itis externa,
•
chronic otitis media) or sensorineural.
Other features include facial nerve palsy and malignancy.
•
Immunodeciency is a risk factor for necrotising otitis externa.
•
Can have successful otological surgery to treat all secondary complications if HIV well
•
controlled.
2
e Ear 109
ANATOMY AND PHYSIOLOGY OF HEARINGMETABOLIC BONE DISEASE AND SYSTEMIC DISORDERS OF THE TEMPORAL BONE
Lyme Disease
Lyme disease is spread by tick bites (genus Ixodes) that cause a localized skin reaction several
days aer a bite. e ticks that spread the disease are oen found in woodland areas. e
most common clinical symptoms are painful radiculitis, cranial palsy (43.4%; mostly facial
which can be bilateral) and headache. However, there are case reports of stand-alone presentations with only sudden HL ± bilateral vestibular failure, but this is rare. Late stages of
the disease can result in severe neurological dysfunction (chronic encephalomyelitis, ataxia,
spastic paraparesis).
Investigations include a two-tier approach that include A C6 antigen–based enzyme-linked
immunosorbent assay (ELISA; combined IgG and IgM) followed by secondary testing with a
conrmatory immunoblot (separate IgG and IgM), if the test was positive or indeterminate.
Treatment is with oral doxycycline for 21 days or intravenous ceriaxone in Lyme carditis
or in unstable patients.
Syphilis
Syphilis is sexually transmitted and is caused by the spirochete Treponema pallidum, which
can spread through the cerebral spinal uid and into the endolymph of the inner ear.
Otosyphilis is known to mimic Meniere’s disease, autoimmune inner ear disease, perilymphatic stula, sudden HL and bilateral vestibular loss. Secondary syphilis can present with
a meningitis.
Radiological ndings include inammatory resorptive osteitis of the temporal bone, and
rarely bony erosion of the ossicles. SNHL is reversible in syphilis if treated in time with penicillin antibiotics; consider screening for disease in patients with sudden SNHL (treponemal
enzyme immunoassay to detect treponemal IgG and IgM).
Inammatory Disease Affecting the Temporal Bone
ese conditions are treated in conjunction with rheumatologists and/or other specialists.
Treatment options may include oral steroids, steroid-sparing immunosuppressants (methotrexate, azathioprine, cyclosporine) or biologics (e.g. rituximab or etanercept).
Autoimmune Hearing Loss
Autoimmune HL is a progressive, bilateral, asymmetric subacute HL that occurs over weeks
to months; HL is oen steroid responsive. It may be primary (occurring in isolation) or secondary to another autoimmune disease. Vestibular involvement is ∼50%. ere is no consensus over diagnostic criteria and no clear evidence to suggest that intratympanic medication
improves hearing outcomes.
3
Cogan’s Syndrome (CS)
Cogan’s syndrome (CS) aects Caucasian adults in the third decade. Typical CS includes
SNHL, interstitial keratitis and audiovestibular dysfunction; whereas atypical CS includes
inammatory ocular symptoms (glaucoma, conjunctivitis, episcleritis, uveitis) and SNHL.
CS is associated with systemic vasculitis in 15–21% and can coexist with other autoimmune
diseases.
ere is no routine laboratory test available for diagnosis. CI is considered for profound
SNHL (early ossication of the cochlea).
Vogt-Koyanagi-Harada
Vogt-Koyanagi-Harada is a multisystem, idiopathic, bilateral granulomatous uveitis with
neurologic, auditory or dermatologic manifestations.
Otological symptoms include SNHL (high frequency), which is steroid responsive, tinnitus
and/or vertigo typically coinciding with the onset of ocular pathology.
110 e Ear
METABOLIC BONE DISEASE AND SYSTEMIC DISORDERS OF THE TEMPORAL BONE
19. EAR TRAUMA
ANCA-Associated Vasculitides
Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides aects small and large
vessels. Immunouorescence testing is done for c-ANCA/p-ANCA and ELISA testing for
MPO and PR3 antibodies. Localised tissue biopsies from nose/ear provide low diagnostic yield.
ere are three types of ANCA: granulomatosis with polyangiitis (respiratory tract), eosinophilic granulomatosis with polyangiitis (respiratory tract and skin) and microscopic polyangiitis (respiratory tract and kidneys).
Otological symptoms include chronic otitis media, vertigo, polyneuritis causing multiple
cranial neuropathies (including facial nerve palsy) and SNHL. ese symptoms (serous otitis
media/HL) can be the rst presentation of the disease.
Relapsing Polychondritis
Relapsing polychondritis is systemic, but episodic inammatory disease primarily aects
the cartilaginous structures of the ears, nose and tracheobronchial tree joints; inner ear;
eyes and the cardiovascular system. It has an unknown aetiology but is oen associated with
rheumatoid arthritis (RA) and systemic lupus erythematosus. Cartilage biopsy is not recommended. Mortality is double that of the normal population.
Sarcoid
Sarcoid diseases are characterized by non-caseating granulomata mainly developing in
the lungs. e skin, lymph nodes and joints may also be aected. Facial nerve palsy is the
most common otologic manifestation and can develop either in isolation or with uveitis
and parotitis as a component of Heerfordt’s disease (uveoparotid fever). Raised angiotensinconverting enzyme titre helps to conrm the diagnosis and hypercalcaemia may also be present. Management is in conjunction with respiratory physicians and usually involves systemic
corticosteroids/immunosuppressants.
Idiopathic
Langerhans Cell Histiocytosis (LCH)
e aetiology of Langerhans cell histiocytosis (LCH) is unknown, and the accumulation of
clonal Langerhans cells occur within any part of the body. It can be single system or multisystem. Isolated pulmonary histiocytosis is common in adults. LCH can develop into malignant histiocytosis.
LCH is diagnosed based on positive immunohistochemistry (Langer CD 207 or CD1a) and
histological examination demonstrating Birbeck granules on electron microscopy. Otologic
symptoms are rare (<4%) but include otorrhea, so tissue or postauricular swelling and oen
bilateral disease.
Imaging shows punched out lesions. LCH of the temporal bone rarely violates the otic capsule. It can mimic otitis media but mastoid disease sparing the middle ear, or outside-in
osseous erosion.
On magnet ic resonance imag ing (MRI), LCH lesions are hy pointense on T1-weighted images,
isointense to hyperintense on T2-weighted images and avid with gadolinium. Positron emission topography is used to diagnose multisystem disease. LCT is treated with chemotherapy,
radiotherapy and surgery for unifocal disease.
KEY POINTS
• There is a limited role for surgery in FD and Paget’s disease of the temporal bone.
• Lyme disease can cause facial palsy particularly in children.
• TB of the temporal bone can present with odourless otorrhoea, middle ear granulation,
facial palsy and HL.
• Autoimmune HL is typically subacute, bilateral, uctuating and steroid responsive.
e Ear 111
ANATOMY AND PHYSIOLOGY OF HEARINGTHE FACIAL NERVE
e
tw
Submandibular and
Submandibular ganglio
posterior digastric
Further Reading
1. Xie C, Mathew R, Adam J, Patel PM. Metabolic bone diseases of the temporal bone:
Part 2. e Otorhinolargologist. 2018;11(3).
2. Cohen BE, Durstenfeld A, Roehm PC. Viral causes of hearing loss: a review for
hearing health professionals. Trend s Hea r. 2014;18:2331216514541361. doi:10.1177/
2331216514541361
3. Strum D, Kim S, Shim T, Monfared A. An update on autoimmune inner ear disease: a
systematic review of pharmacotherapy. Am J Otolaryngol. 2020; 41(1):102310.
21. THE FACIAL NERVE
Anatomy of the Facial Nerve
e key functions of the facial nerve include:
Primarily motor nerve supplying muscles of facial expression
•
Parasympathetic secretomotor supply to lacrimal and salivary glands
•
Sensory supply from external auditory canal
•
Special sensory (taste) from anterior two-thirds of tongue
•
e course of the facial nerve is shown in Figure 21.1 and can be divided into intracranial,
intratemporal and extratemporal portions. e intracranial portion is approximately 24 mm
sublingual salivary
Figure 21.1 General visceral afferent axons (nasopharynx, palate, submandibular and sublingual
salivary glands) not shown. Cell bodies of origin in the geniculate ganglion project to more caudal
regions of the solitary nucleus. (With permission from Haines DE. Fundamental Neuroscience for
Basic and Clinical Applications. London: Elsevier Health Sciences, 2012.)
112 e Ear
Superior salivatory nucleus
Facial and intermediate
Internal acoustic meatus
Pterygopalatine
Nasal, palatine,
lacrimal glands
Taste from anterior
o thirds of tongue
glands
Chorda tympani
nerve roots
ganglion
n
Muscles of facial
expression and
Geniculate
ganglion
Stylomastoid
foramen
Skin of the external
acoustic meatus
Abducens nucleus
Internal genu of facial nerv
Facial motor nucleus
Solitary tract and
nucleus
Spinal trigeminal
tract and nucleus
21. THE FACIAL NERVE
THE FACIAL NERVE
long and courses through the cerebellopontine angle (CPA) cistern to the porus of the internal auditory meatus (IAM). e intratemporal portion is 28–30 mm long. is includes the
meatal segment, which runs in the IAM. e labyrinthine segment then runs laterally to
the rst genu and the geniculate ganglion, the tympanic segment runs posteriorly from the
geniculate ganglion to the second genu and the vertical segment runs from the second genu
to the stylomastoid foramen. e extratemporal segment runs forward into the parotid gland
where it divides into upper and lower branches.
Pathophysiology of Nerve Injury
Peripheral ner ves may be injured in a var iety of ways, with local or systemic causes. Ischaemia
induced by mild pressure may produce transient paraesthesia with no obvious structural
changes, and recovery is rapid. Prolonged ischaemia or immune-mediated attack may cause
loss of myelin without loss of axonal integrity. In trauma, if the compressing force, such as
a spicule of bone or a haematoma, is removed, remyelination typically takes place within
2–4 months, usually with little residual loss of function.
An injury that physically separates axons from their cell bodies triggers cellular events at the
site of the lesion and in distant parts of the injured neurons and their target organs, which has
a signicant impact on outcome. Wallerian degeneration refers to the degeneration of a nerve
distal to the site of injury. Peripherally, atrophy of chronically denervated muscles may preclude
their reinnervation. Table 21.1 shows the Seddon and Sunderland classications of nerve injury.
Table 21.1 Nerve injury classication and electrophysiological correlates
Electrophysiological
Seddon Sunderland Pathology
Neurapraxia Grade 1 A transient light compression causing
endoneurial edema but no signicant
morphological changes. A more
substantial and prolonged mechanical
compression or stretch is most likely
to cause a focal demyelination that
may be paranodal or affect whole
internodes. Anoxia plays a role in the
pathogenesis
Axonotmesis Grade 2 Axons degenerate distal to the site of
the ‘lesion’, irrespective of calibre or
modality
Endoneurium, perineurium and
epineurium remain intact. Schwann
cell basal lamina tuubes either remain
continuous across the ‘lesion’ or are
minimally separated within a
morphologically intact perineurium
and epineurium
Axonotmesis Grade 3 Endoneurium disrupted, axons
degenerate distal to the site of the
‘lesion’
Axonotmesis Grade 4 Perineurium disrupted, axons
degenerate distal to the site pf ‘lesion’
Neurotmesis Grade 5 Epineurium disrupted, axons degenerate
distal to the site of the ‘lesion’
Source: Modied from Birch. Surgical disorders of the peripheral nerves. 2nd ed. Springer;
London; 2011.
Note: SNAP, sensory nerve action potential; CMAP, compound muscle action potential.
correlate
Conduction block ±
conduction slowing.
Never distal to ‘lesion’
shows normal
conduction
Fibrillation
Mild diminution to
complete absence of
SNAP and CMAP
responses, in proportion
to degree of axonal loss
± varying degrees of
conduction block and
slowing associated with
demyelination
Fibrillations, absent SNAP
and CMAP responses
Fibrillations, absent SNAP
and CMAP responses
Fibrillations, absent SNAP
and CMAP responses
e Ear 113
ANATOMY AND PHYSIOLOGY OF HEARINGTHE FACIAL NERVE
Clinical Evaluation of Patients with Facial Palsy
History
Most patients with acute-onset facial palsy will be assumed to have an idiopathic (Bell’s)
palsy. Progressive palsy, or an incomplete facial nerve palsy that does not start to recover
aer 3 to 6 weeks, should prompt suspicion of neoplasm and further investigation. Ipsilateral
recurrent facial nerve palsy is occasionally seen in patients with idiopat hic palsy, MelkerssonRosenthal syndrome (a condition characterised by facial oedema, familial history and ssured tongue) and tumours. Bilateral concurrent facial nerve paralysis is most commonly
associated with severe head trauma or systemic conditions including Guillain-Barré syndrome, sarcoidosis, Lyme disease, rabies and Moebius syndrome.
Physical Examination
A thorough head, neck, otologic and cranial nerve examination is required when evaluating
facial nerve dysfunction. e degree of facial weakness must be recorded and an attempt
made to localise the site of the cause.
e House-Brackmann Staging System is the most widely used of several grading scales
(Table 21.2).
Facial nerve dysfunction includes secondary eects which usually result from aberrant
neural regeneration and include synkinesis, hemifacial spasm, contracture, crocodile tears,
epiphora, dysgeusia, pain and hyperacusis. e Sunnybrook Facial Grading scale attempts to
include some of these secondary eects in the overall score.
Functional and psychological impairments that include diculties in eating, drinking,
speaking and conveying emotion are not captured in any of the clinician-ranked scales and
would be better measured by patient-reported outcome measures.
Table 21.2 House-Brackmann staging system
Degree of injury Grade Denition
Normal I Normal symmetrical function in all areas
Mild dysfunction
(barely noticeable)
Moderate dysfunction
(obvious difference)
Moderately severe
dysfunction)
Severe dysfunction V Motion barely perceptible
Total paralysis VI No movement, loss of tone, no synkinesis, contracture or spasm
II Slight weakness noticeable only on close inspection
Complete eye closure with minimum effort
Slight asymmetry of smile with maximal effort
Synkinesis barely noticeable, contracture or spasm absent
III Obvious weakness, but not disguring
May not be able to lift eyebrow
Complete eye closure and strong but asymmetric mouth
movement with maximal effort
Obvious, but not disguring synkinesis, mass movement or spasm
IV Obvious disguring weakness
Inability to lift eyebrow
Incomplete eye closure and asymmetry of the mouth with
maximal effort
Severe synkinesis, mass movement, spasm
Incomplete eye closure, slight movement of the corner of the
mouth
Synkinesis, contracture and spasm usually absent
114 e Ear
21. THE FACIAL NERVE
THE FACIAL NERVE
Investigation and Nerve Monitoring
Electrophysiological Tests
Electrophysiological tests provide prognostic information to guide management in complete
paralysis.
Electroneuronography (ENoG)
During electroneuronography (ENoG), a supramaximal stimulus is delivered to the facial
nerve trunk as it exits the stylomastoid foramen and the evoked biphasic compound muscle
action potential (CMAP) is recorded using surface electrodes. e response of the paralysed
side is expressed as a percentage of the normal contralateral side. If the CMAP amplitude on
the aected side is 10% of the normal side, then it is assumed that 90% axonal loss has been
sustained. ENoG is said not to be useful until the fourth day of facial nerve paralysis, which
is when axonal degeneration associated with injury occurs.
Electromyography (EMG)
Electromyography (EMG) records active motor unit potentials of the orbicularis oculi and
orbicularis oris muscles during rest and voluntary contraction. EMG has a role in decision
making, as seen in Table 21.3.
Table 21.3 ENoG and EMG
Long-term
paralysis
management
decision
N/A
Surgical
exploration is
indicated with
a view to
achieving nerve
continuity
Surgical
intervention
not indicated
Static or
dynamic facial
reanimation is
indicated.
Study Measurement
ENoG Evoked CMAP
EMG
Acute
paralysis
EMG
Prolonged
paralysis
compared
with normal
site
Active motor
unit potentials
after voluntary
forceful
contraction
When to
measure
Between
3 days and
3 weeks
Complementary
to ENoG,
after 2 weeks
In long-standing
paralysis
Use in
acute-onset
paralysis
>90% of
degenerated
bres
suggests poor
prognosis
Presence of
active motor
potentials in
response to
voluntary
contractions
indicates
good
prognosis
Use in longstanding paralysis
Not useful because
of desynchronisation
Fibrillation
potentials suggest
Wallerian
degeneration (arise
2–3 weeks after
injury)
Polyphasic potentials
suggest
reinnervation (may
precede clinical
recovery
by 6–12 weeks)
‘Silence’ on EMG (no
electrical output)
indicates long-term
denervation and
suggests that
muscle has been
replaced by brous
tissue.
e Ear 115
ANATOMY AND PHYSIOLOGY OF HEARINGTHE FACIAL NERVE
Blood Investigations
In patients who present with an atypical history or who fail to recover within 6 weeks, the
authors practice is to arrange the following blood tests:
Angiotensin-converting enzyme: elevated in sarcoidosis
•
Anti-neutrophil cy toplasmic antibody : elevated in gra nulomatosis with poly angiitis (GPA)
•
Human immunodeciency virus (HIV), Lyme and syphilis serology
•
Radiological Imaging
e optimal imaging modality for facial nerve disorders may include:
Computed tomography (CT) if ear abnormality present or history of trauma
•
Magnetic resonance imaging (MRI) with pre- and post-contrast of whole facial nerve
•
course (cortex to neck) for tumours
Scan at 3/12 in cases of presumed idiopathic if incomplete recovery
•
Management of the Patient with a Facial Nerve Disorder
Acute Facial Palsy
Eye Care
Appropriate eye care, including advice regarding corneal protection with lubrication and
patching should be instituted immediately in cases where eye closure is impaired. Patients
should be instructed in the use of drops (day) and ointment (night) and in manually closing
their eyes and stretching the upper lid to prevent shortening. Upper eyelid weighting with
external adhesive skin-tone coloured weights (Blinkeze™) can be advised.
Idiopathic (Bell’s) Palsy
Patients present with a prodromal illness, which may include periauricular pain and general
malaise. Within 72 hours they rapidly develop lower motor neuron facial weakness. In up to
70% of cases this weakness is complete (House-Brackmann VI).
e aetiology of idiopathic palsy remains unclear, but evidence suggests an infectious origin,
which triggers an immunologic response resulting in damage to the facial nerve. Pathogens
implicated include herpes simplex virus type 1 (HSV-1), herpes simplex virus type 2 (HSV-2),
human herpesvirus and varicella zoster virus (VZV). Idiopathic palsy is more common in
pregnancy and has a poorer prognosis with the majority of cases being in the third trimester.
Normal function is usually regained within 6 months in about two-thirds of all patients, but
a signicant proportion have long-term issues with facial asymmetry, tightness and synkinesis. Poor prognosis has been related to complete paralysis at onset.
e pharmacological management of idiopathic palsy primarily involves oral corticosteroid
medication with benet if instigated within 72 hours. In addition, the most recent evidence
from a Cochrane review
the rate of recovery and reduces the long-term aer eects of idiopathic palsy. A typical
treatment regimen is prednisolone 1 mg/kg/day for 10 days and oral acyclovir (400 mg ve
times daily) for 10 days.
Inammatory Disorders
For inammatory conditions that cause facial palsy, including GPA, sarcoid and Lyme disease, see Chapter 20.
Iatrogenic Injury
If facial palsy is observed immediately aer tympanomastoid surgery and the nerve was not
injured/not at risk, a few hours of observation will allow local anaesthetic-induced weakness
to clear. e possibility of a tight mastoid dressing over an exposed nerve should prompt
consideration of pack removal. If the paralysis is incomplete or delayed, the patient should be
116 e Ear
1
concludes that the addition of antiviral medication likely improves
21. THE FACIAL NERVE
THE FACIAL NERVE
started on oral steroids and observed. In cases where re-exploration is needed, this should be
performed with an expert colleague. In rare cases, a delayed palsy is observed a few days aer
uneventful middle ear surgery. Use of systemic steroids should be considered and prognosis
appears to be good.
Cerebellopontine Angle Tumour Surgery
Postoperative facial nerve function in CPA tumour surgery mainly depends on tumour size
and surgical experience. When the facial nerve is lost during dissection, it may be possible to
achieve an end-to-end anastomosis or place a cable interposition gra.
Facial Nerve Trauma
Management of facial nerve paralysis following trauma is oen deferred until the patient is
medically stable. Facial nerve paralysis can result from stab wounds to the face or mandibular fractures. If possible, it is advisable to explore the region within 3 days as a nerve stimulator may be used to identify the distal nerve branches. With gunshot wounds care must be
taken when assessing facial nerve function as there is oen signicant facial oedema and
both muscle tone and eye closure appear adequate when in fact they are not. For temporal
bone fractures see Chapter 19.
Tumours of the Facial Nerve
Facial nerve tumours are rare. e most common histological type are facial nerve schwannomas (FNS); however, facial nerve haemangiomas, malignant nerve sheath tumours and ‘skip’
lesions from parotid malig nancies, amongst others, can a lso occur. As with other schwannomas,
FNS are benign, slow-growing tumours arising from Schwann cells within the nerve sheath.
Clinical Presentation of Facial Schwannomas
FNS can arise from anywhere along the course of the facial nerve from the CPA to the ramications within the parotid. FNS are commonly found to involve multiple segments with the
most common sites being the geniculate ganglion (68%), labyrinthine (52%) and tympanic
(43%) segments. Symptoms vary according to the segment involved. Whilst presentation
can be with sudden-onset facial weakness, progressive weakness or hemifacial spasm, particularly the combination of synkinesis and partial paralysis are more suggestive of FNS. In
addition, many patients preserve normal facial nerve function and may present with hearing
loss, tinnitus, imbalance or a neck lump. Hearing loss may be sensorineural with IAM/CPA
involvement or conductive if the horizontal portion of the facial nerve is aected.
Investigations
Diagnosis is with high-resolution cross-sectional imaging including T1-weighted MRI with
gadolinium. FNS that are limited to the IAM/CPA can be dicult to dierentiate from vestibular schwannomas, but involvement of the geniculate ganglion with extension along the
greater supercial petrosal nerve is indicative of FNS (Figure 21.2). CT of the temporal bones
may demonstrate smooth bony expansion at the site of the FNS.
Management of Facial Nerve Schwannomas
e primary aim of management is preservation of optimal facial function for as long as possible. For most patients this is achieved through conservative management with observation
and serial scanning. For tumours that grow and/or develop loss of facial function, treatment
options will include stereotactic radiosurgery (SRS), bony decompression of the IAM/facial
canal, surgical debulking or excision with graing/reanimation. Facial nerve resection with
graing is unlikely to achieve better than House-Brackman grade III, therefore, for patients
with growing tumours but normal facial function, SRS is usually preferred.
Multidisciplinary Management of Established Facial Palsy
Facial palsy has a huge negative impact on quality of life and is best managed by a multidisciplinary facial nerve clinic comprising surgeons from otolaryngology and plastic surgery and
e Ear 117
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