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ANATOMY AND PHYSIOLOGY OF HEARINGTHE FACIAL NERVE
Figure 21.2 (A) Axial T1-weighted MRI with contrast showing enhancing nerve facial schwan-
noma lling the internal auditory meatus and extending along the greater supercial petrosal nerve
into the middle fossa. (B) Coronal MRI showing a facial schwannoma arising from the geniculate
ganglion and extending through the petrosal foramen into the middle fossa, pushing upwards into
the temporal lobe.
highly specialised facial therapists. Additional support from an oculoplastic surgeon, expert
radiologist, clinical photography and psychological services is advised. e development of
support networks and groups has enabled patients to benet from the experience of others.
Physiotherapy
Tightness and shortening of the muscle bres can result in a ‘frozen face’. Specic guidance
regarding muscle stretches allows the muscles to relax and facial symmetry to improve. Once
the muscle length is restored, more active movement is usually achieved.
Chemodenervation with Botulinum Toxin
Botulinum toxin can be used to release the over-tightened facial muscles. In patients
with synkinesis (unwanted muscle contractions resulting from aberrant reinnervation)
118 e Ear
21. THE FACIAL NERVE
VESTIBULAR SCHWANNOMA
chemodenervation is helpful in reducing these unwanted movements. Chemodenervation
can be employed to weaken the more active ‘normal’ facial muscles to achieve a more balanced facial appearance.
FACIAL REANIMATION
Reinnervation
Lack of recovery of facial function by 12 months is considered a permanent decit as loss
of motor end-plate units likely means that reinnervation techniques will have no benecial
eect. Prior to this point, nerve transfers including contralateral facial nerve, nerve to masseter and the hypoglossal nerve can be employed.
Static Reanimation
Periocular surgery, including lower-lid tightening, lateral canthopexy, brow li and upper
eyelid positioning/weighting surgery may be performed under local anaesthesia and can
provide benet for the patient with troublesome eye symptoms. Various face-liing techniques can improve the static position of the face.
Dynamic Reanimation
In those patients in whom active movement is desired, particularly in terms of smile, it is
usually necessary to bring new tissue to the area. is may be in the form of muscle transfer,
for example, a temporalis transfer or free muscle gra. In the latter case, innervation of the
muscle gra may be from the facial nerve stump (e.g. in a cancer case) or more commonly
the nerve to masseter or cross face nerve gra.
KEY POINTS
• Most common cause is idiopathic (Bell’s palsy).
• Slowly progressing weakness suggests space-occupying lesion (anywhere along the
course of the nerve).
• Corticosteroids are the mainstay of acute management (antivirals indicated in
complete palsy).
• Two-thirds of patients with Bell’s palsy recover completely by 6 months.
• Established weakness should be managed in specialist multidisciplinary treatment.
Further Reading
1. Gagyor I, Madhok VB, Daly F, Sullivan F. Antiviral treatment for Bell’s palsy (idiopathic facial paralysis). Cochrane Database Syst Rev. 2019; 9(9):CD001869. doi: 10.1002/
14651858.CD001869.pub9.
2. Peitersen E. e natural history of Bell’s palsy. Am J Otol. 1982; 4(2):107–111.
22. VESTIBULAR SCHWANNOMA
Overview
Vestibular schwannomas (VS) are the most common tumours of the cerebellopontine angle
(CPA) although, with an incidence of 33.8 tumours per 1,000,000 person-years, they remain
rare clinical entities. ey are benign lesions t hat arise from abnorma l proliferation of Schwann
cells along the vestibular divisions of the vestibulocochlear nerve (cranial nerve [CN] VIII).
e Ear 119
ANATOMY AND PHYSIOLOGY OF HEARINGVESTIBULAR SCHWANNOMA
Table 22.1 Classication of VS according to size
Classication Grade Size (mm)
Grade 0 Intrameatal 0
Grade 1 Small 1–10
Grade 2 Medium 11–20
Grade 3 Moderately large 21–30
Grade 4 Large 31–40
Grade 5 Giant >40
a
Consensus Meeting on Reporting Systems on Vestibular Schwannomas (Kanzaki
et al., 2003).
a
VS may be conne d to the interna l auditory cana l (IAC) or extend into the CPA. Uncommonly
they can be entirely medial. Rarely, they can also invade the labyrinth. Current consensus
is that the largest extrameatal dimension should be used to report tumour size (Table 22.1).
e diagnosis of VS relies mainly on magnetic resonance imaging (MRI) scanning. VS are iso/
hypointense on T1- and T2-weighted sequences and they enhance avidly with contrast (gadolinium). T2-weighted imaging is adequate for diagnosis and monitoring, but a contrast-enhanced
scan can help distinguish VS from other lesions, and fat suppression can diagnose lipomas. It is
generally accepted that every patient with unilateral audiovestibular symptoms of unknown aetiology should undergo an MRI scan of the IACs. is is also true for patients presenting with sudden sensorineural hearing loss (SSNHL), where an underlying VS is found in 1.9–4.9% of cases.
At diagnosis, the average tumour size is 10 mm but 33% are conned to the IAC.
Approximately 30% of tumours demonstrate growth aer diagnosis (>2mm) with approxi-
mately 10% showing regression and approximately 60% remaining stable. Tumour growth
can, but rarely does, occur aer 5 years of radiological stability.
ose VS that demonstrate growth have a mean annual growth rate of 1.6–4.7mm. Over a
5-year period, 23% of purely intrameatal tumours will extend into the CPA.
Most tumours are solid, but cystic changes are seen in around 10% of tumours. Cystic
changes are associated with more unpredictable tumour behaviour and some authors have
reported that radiotherapy is less eective in these cases. Growing cystic tumours may
therefore be considered earlier for surgery.
Overall, 95% of VS patients will suer from hearing loss, either at presentation or subsequently (Table 22.2). It is usually progressive but it may be of sudden onset in up to 10% of
neurobromatosis type 2 (NF2)-related tumours and 20% of sporadic tumours. Seventy
percent of patients have tinnitus, usually not disturbing, and 50% have balance disturbance at presentation. ere is no association between audiological symptoms and tumour
size. Non-audiovestibular symptoms such as facial numbness, ataxia or headache may also
develop but usually only occur with larger tumours. e most widely used hearing classication systems for VS patients are the American Academy of Otolaryngology-Head and
Neck Surgery classication (AAO-HNS) and the Word Recognition Scale (WRS).
Over a 10-year period of observation, 54% lose their AAO-HNS class A hearing level. Over
the same period, those who had WRS class 0 hearing at presentation will deteriorate to class
2 or worse in 31% of patients.
Tumour Treatment
ere are three main treatment options: wait and rescan, radiotherapy and surgery.
Based on the current literature, a few general management principles can be established:
An initial wait and rescan approach is indicated for tumours below 20mm as long as
•
there is no signicant brainstem compression.
120 e Ear
22. VESTIBULAR SCHWANNOMA
VESTIBULAR SCHWANNOMA
Table 22.2 Classication of hearing levels
a
Class
A ≤30 >70
B >30 and ≤50 ≥50
C >50 ≥50
D Any level <50
c
Class
0 100
I 70–99
II 50–69
III 1–49
IV 0
a
Class A and B hearing are referred to as ‘serviceable’, while class C and D are ‘non-serviceable’.
b
Pure-tone average: average thresholds (dB) at 500, 1000, 2000 and 4000 Hz.
c
Class 0 and I hearing are considered ‘good’.
If signicant tumour growth occurs (>2 mm), active treatment (radiotherapy or sur-
•
gery) must be considered although it may be deferred if growth is slow and tumour
size is small, or if there are medical contraindications or limited life expectancy, as
around 20% of tumours stop growing aer a period of growth.
Growing tumours up to around 25 mm may be treated with radiotherapy, although
•
surgery is an option depending on the patients risk preferences.
Tumours larger than 25 mm are generally treated with surgical resection.
•
Pure-tone average (dB)
AAO-HNS (1995)
b
Word Recognition Scale
Speech discrimination scores (%)
Speech discrimination scores (%)
Radiotherapy
Two different types of radiotherapy treatment are currently available, stereotactic radiosurgery (SRS) and fractionated radiotherapy (FRT). SRS is generally given as a single
dose of treatment. Two main types of radiotherapy are used: gamma radiation or electrons. The former is delivered by the Gamma Knife. The latter is delivered via a linear
accelerator (LINAC) with several types of machines available that vary with regards
to their method of targeting (e.g. Novalis and CyberKnife). A dose of 12–14Gy at the
tumour margins is the usual dose used, which balances tumour control with risk of complication. In FRT, multiple treatment sessions are required (1.8–2Gy/day over 5–6 weeks
or 5-7Gy/day over 3–5 fractions) and treatment is usually delivered using a LINAC.
Accuracy is sub-millimetric with the head fixed by a tight mask for LINAC and by a
frame fixed to the head in Gamma Knife.
e main objective of radiotherapy in VS is to stop tumour growth and avoid further need for
surgical intervention. Tumours may transiently enlarge up to 24 months post-treatment, aer
which they usually stabilise or regress. When a tumour begins or continues to enlarge aer
that period, treatment failure is conrmed and surgery is generally indicated. e reported
tumour-control rate following radiotherapy ranges from 92–98% over a 3- to 10-year followup period. Patients may experience various complications aer treatment, including:
Trigeminal neuropathy (0, 3–27%)
•
Facial nerve palsy and/or facial hemispasm (<2%)
•
Hydrocephalus (<1%; increased risk if CPA component >2.5cm)
•
Brain radionecrosis and/or stroke
•
Hearing loss
•
Induction of new tumours
•
Conversion of a benign tumour to a malignant one
•
e Ear 121
ANATOMY AND PHYSIOLOGY OF HEARINGVESTIBULAR SCHWANNOMA
A recent meta-analysis found that of those that had serviceable hearing (AAO-HNS class A
or B), only 25% of patients retain serviceable hearing aer 10 years of follow-up. Induction
of new tumours and malignant transformation in the existing tumour are very rare, occurring in much less than 1% of patients per decade aer treatment. ese latter risks are less
relevant to the older patient and make radiotherapy, with its relatively low morbidity, particularly attractive to this group.
Surgery
Surgery is the treatment of choice for tumours >25 mm and may be oered instead of radiotherapy for smaller growing tumours, particularly in the younger age group. ree surgical approaches are widely used to resect VS: translabyrinthine, retrosigmoid and middle
fossa (Table 22.3). e retrolabyrinthine, transcochlear and endoscopic transpromontorial
approaches have also been described.
Table 22.3 Surgical approaches to the CPA
Surgical
approach Key surgical steps Advantages Disadvantages
Translabyrinthine 1 Skin and periosteal ap
2 Extended cortical
mastoidectomy
3 Bony labyrinthectomy
4 Jugular bulb and facial
nerve skeletonisation
5 IAM skeletonisation
6 Identication of the
facial nerve (lateral
portion of the IAM)
7 Opening of the
posterior fossa dura
8 Tumour removal
9 Closure (with
abdominal fat graft)
Middle fossa 1 Skin incision and
division of temporalis
muscle
2 Middle fossa
craniectomy
3 Extradural approach to
the middle fossa oor
and posterior fossa
4 IAM skeletonisation
5 Identication of facial
and vestibular nerves
6 Tumour removal
7 Closure
Retrosigmoid 1 Skin and soft tissue
incisions
2 Retrosigmoid
craniectomy
3 Dural opening and CSF
decompression
4 Intradural approach to
the tumour
5 Tumour removal (± IAC
drilling)
6 Closure
1 Extradural drilling
2 No cerebellar
retraction
3 Early identication
of the facial nerve
(lateral end of the
IAC)
4 VS of any size can
be removed
5 Immediate repair of
facial nerve possible
1 Hearing preservation
(possible)
2 No cerebellar
retraction
3 Extradural drilling
4 Good access to the
lateral end of the
IAM compared with
retrosigmoid
1 Hearing
preservation
(possible)
2 Excellent
visualisation of the
CPA
1 No hearing
preservation
2 Increased incidence
of postop CSF leaks
1 Facial nerve
between the
surgeon and the
tumour
(unfavorable
position)
2 Temporal lobe
retraction with risk
of epilepsy
3 Removal of tumour
with a maximal
CPA dimension of
10–15 mm
1 Intradural drilling
2 Cerebellar
retraction
3 Increased incidence
of postoperative
headache
4 Limited access to
the lateral portion
of the IAM
122 e Ear
22. VESTIBULAR SCHWANNOMA
VESTIBULAR SCHWANNOMA
Both the middle fossa and retrosigmoid approaches oer the potential benet of hearing
preservation. is is also true for the retrolabyrinthine approach. To preserve hearing,
the tumour must be small (maximal CPA component of <10 mm) and not extend up to
the fundus of the IAC. Approximately 50% of patients retain serviceable hearing 10 years
aer surgery. However, hearing preservation rates vary widely depending on the surgical
approach used.
ere are two main factors aecting surgical outcomes and postoperative complication rates:
tumour size (most important) and experience/surgical skills of the skull base unit. While
mortality is rare (≤1%), surgical excision of a VS is a major surgical intervention that has
a wide range of potential complications, the most common of which is cerebrospinal uid
(CSF) leakage. e leak may occur through the wound, from the external ear canal or from
the nose via the Eustachian tube. Minor leaks may be managed conservatively with a lumbar drain. More severe CSF leaks are managed with blind sac closure and Eustachian tube
obliteration, with or without CSF lumbar drainage. Refractory leaks will rarely require permanent CSF diversion (<1%).
e facial nerve is in close proximity to the tumour and its preservation is a key aim of surgery. Most series report the following facial nerve outcomes, using the House-Brackmann
(HB) classication:
0–15 mm: 80–95% HB grade I–II with 100% anatomical preservation
•
>15 –25 mm: 80–90% HB grade I–II with 90% anatomical preservation
•
>25 mm: 50–70% HB grade I–II with 65–80% anatomical preservation
•
Recurrence rate aer surgery is mainly inuenced by the completeness of resection.
Following gross total excision, recurrence is observed in 1–3% of cases. For near-total (linear remnant of tumour adherent to the facial nerve) and subtotal resections (solid mass of
tumour le behind), regrowth rates can reach up to 21% and 22%, respectively. e tumour
residuum may necessitate further treatment by radiotherapy or surgery depending on its size
and whether or not it is growing on radiological follow-up.
Neurobromatosis Type 2 (NF2)
NF2 is a genetic condition associated with the development of numerous tumours involving the nervous system. e disorder is inherited in an autosomal dominant fashion. In
around 50% of cases, patients do not have any positive family history and present with a
de novo mutation. Among de novo cases, up to 60% display somatic mosaicism, where one
cell lineage with a mutated NF2 gene and one without any mutation develop throughout
the body. In the presence of mosaicism, mutation is postzygotic and patients have more
localised manifestations with less severe phenotypes. Because of mosaicism, the transmission rate in de novo cases is below 50%. In the second generation and beyond, transmission
is 50%, as children inheriting NF2 from a mosaic parent will have the NF2 mutation in
their germline.
e NF2 gene is located on chromosome 22q12.2 and encodes the NF2 protein, also known as
merlin or schwannomin. is cell cytoskeleton–associated protein is involved in cell growth
inhibition. e loss of these tumour-suppressor functions is believed to be the main factor
in the formation of all schwannomas and meningiomas. A range of mutation types has been
identied in NF2 including missense, truncating and splice site mutations and deletions.
ere is a strong genotype/phenotype relationship with missense mutations being associated
with milder disease compared with truncating mutations.
e birth incidence of NF2 in the United Kingdom is estimated at 1 in 33,000 live births. By
60 years of age, almost every NF2 pat ient will be sy mptomatic. Bilateral VS are almost pathognomonic in NF2 and 95% of patients will develop bilateral tumours by the age of 30. Schwannomas
may also aect other cranial, spinal and peripheral nerves. Approximately 50% of patients have
e Ear 123
ANATOMY AND PHYSIOLOGY OF HEARINGVESTIBULAR SCHWANNOMA
intracranial or spinal meningiomas. Less frequently, they can develop other low-grade intracranial tumours, such as ependymomas. Ophthalmic abnormalities are also frequently encountered (e.g. 60–80% cataracts). Over the years, dierent clinical diagnostic criteria have been
proposed, among which the ‘Revised Manchester criteria’ is the most widely used.
When NF2 is suspected, contrast-enhanced MRI scanning of the head and whole spine must
be performed. At-risk individuals requiring further investigations must meet one of the following criteria:
Positive family history of NF2
•
<30 years old presenting with unilateral VS and/or meningioma
•
Multiple spinal tumours (schwannomas and/or meningiomas)
•
Cutaneous schwannomas
•
e screening protocol for VS in asymptomatic at-risk patients is as follows:
Genetic screening
•
Start MRI screening from age 10
•
10–20 years: MRI every 2 years
•
21–40 years: MRI every 3–5 years (because this group have slower growing
•
tu mours)
If genetic screening negative and no tumour by age 40 then discharge
•
NF2 can also be diagnosed by identifying pathological mutations in patients’ blood, with a
success rate of 93% in non-mosaic cases. e presence of the NF2 mutation in blood is much
lower in mosaic cases.
Overall, 60% of patients with NF2 have bilateral VS at their initial assessment. VS in NF2
tend to be more aggressive than sporadic tumours, but behavior is inuenced by genotype/
mosaicism. Overall 65% of NF2 VS demonstrate growth over time, with an average growth
rate of 2mm/year. Over the course of their disease, most patients will develop bilateral profound deafness either as a result of the tumour or treatment.
Historically, VS treatment in NF2 has been mainly surgical. A conservative approach is,
however, indicated for small- or medium-sized stable or very slow growing tumours. New
systemic therapies such as bevacizumab, a monoclonal antibody of vascular endothelial
growth factor A, have demonstrated considerable ecacy in controlling VS growth and may
also preserve audiological function. In a limited number of cases, radiotherapy may be considered, although control is less eective compared with sporadic tumours. ere is also a
greater risk of inducing new tumours within the radiotherapy eld and of inducing malignant change in previously treated tumours (malignant peripheral nerve sheath tumours)
compared with sporadic tumours, especially if treated at a young age.
Optimising hearing rehabilitation in NF2 is critical as bilateral hearing loss has a very signicant impact on quality of life. In those who develop profound hearing loss in an ear
with a stable tumour (whether through its natural behaviour or through treatment with
radiotherapy/bevacizumab) there is now good evidence for the eectiveness of cochlear
implantation. Similarly, there is good evidence that, in selected cases, tumour removal with
preservation of the cochlear nerve together with cochlear implantation oers reasonable
hearing outcomes. Outcomes are, however, less good in NF2 than the average non-NF2
cochlear implant user, with untreated ears having the best outcome and those having had
radiotherapy or nerve-preserving surgery having poorer outcomes. For most patients having surgery, cochlear nerve preservation is not possible and the only way to provide some
audition is through auditory brainstem implantation (ABI). ese provide environmental sound awareness and act as an aid to lipreading in most cases. Only 10% of recipients
achieve open-set speech discrimination. Both cochlear implantation and ABI have a nonuser rate of around 20% in NF2.
124 e Ear
LESIONS OF THE CEREBELLOPONTINE ANGLE, PETROUS APEX AND JUGULAR FORAMEN
KEY POINTS
• Sporadic and NF2-related VS are rare benign slow-growing tumours originating from
the vestibular divisions of CN VIII.
• They most often present with hearing loss, tinnitus or balance disturbance.
• While there is no correlation between tumour size and hearing loss at presentation,
other non-audiological symptoms are associated with larger tumour size.
• MRI scan with contrast is the diagnostic modality of choice for VS and must be
performed in the presence of unilateral or asymmetric audiovestibular symptoms of
unknown aetiology.
• NF2 is an autosomal dominant disorder associated with a mutation on chromosome
22q12.2. Bilateral VS is almost pathognomonic of this condition.
• Small- or medium-sized VS may be managed conservatively (watch and wait) with
only 30% demonstrating growth. Growing small- or medium-sized tumours may
be managed with surgical resection or with radiotherapy. Large tumours (>3cm) are
generally managed with surgical resection. In NF2, systemic drug therapies, such as
bevacizumab, have demonstrated signicant efcacy in controlling tumour growth.
• Radiotherapy has a high tumour control rate (92–98%) and low short-term
complication rates. Hearing loss increases greater than it would otherwise do following
treatment and there is a small risk of inducing new tumours or inducing malignant
change in the treated tumour in the long run.
• Surgery is the treatment of choice for large tumours or following radiotherapy failure.
It is also a viable option for growing small- and medium-sized VS. There is a risk of
facial palsy, which increases with increasing tumour size.
22. VESTIBULAR SCHwANNOMA
Further Reading
Borsetto D., Faccioli C., and Zanoletti E., Sporadic acoustic neuroma: current treatment
options with focus on hearing outcome. Hearing, Balance and Communication, 2018.
16(4): p. 248–254.
Carlson M.L. (Ed.), Comprehensive Management of Vestibular Schwannoma, New York:
ieme, 2019.
Kanzaki J, Tos M, Sanna M, et al. New and modied reporting systems from the consen-
sus meeting on systems for reporting results in vestibular schwannoma. Otol Neurotol
2003; 24(4): 642–648.
23. LESIONS OF THE CEREBELLOPONTINE ANGLE, PETROUS APEX
AND JUGULAR FORAMEN
Introduction
Most conditions of the petrous apex (PA), cerebellopontine angle (CPA) and jugular foramen
(JF) can be distinguished by using a combination of computed tomography (CT) and magnetic
resonance (MR) without the need for biopsy (Table 23.1). Bony destruction in the CT is sugges-
tive of a malignant process, whereas well-dened expansion is indicative of a benign process.
Petrous Apex Lesions
Anatomy
e PA is the anteromedial pyramid-shaped portion of the petrous temporal bone.
•
It is divided into two compartments by the internal auditory meatus: an anterior por-
•
tion, principally consisting of bone marrow/air cells and a posterior portion, from the
dense bone of the otic capsule (Figure 23.1).
e Ear 125
ANATOMY AND PHYSIOLOGY OF HEARINGLESIONS OF THE CEREBELLOPONTINE ANGLE, PETROUS APEX AND JUGULAR FORAMEN
Table 23.1 Conditions of the PA, CPA and JF with characteristic radiological ndings
MRI
Pathology Location CT
Cholesterol
Granuloma
Asymmetric
marrow
Epidermoid cyst PA/CPA Expansile ↓ ↑ No High signal on DWI
Mucocele PA Expansile ↓ ↑ No DWI with no restricted
Meningioma PA/CPA/JF Hyperostosis →/↑ →/↓ Yes Dural tail, calcication
Arachnoid cyst CPA CSF density ↓ ↑ No Same signal as CSF
Schwannoma CPA/JF Isodense to
Paraganglioma JF Expansile → ↑ Yes ‘Salt and pepper’
Lipoma CPA Fat density ↑ ↑ No Saturation on T1 fat
Chordoma Clivus
Chondrosarcoma PA/petro-
Metastasis,
myeloma
Sarcoma,
Langerhans cell
histiocytosis
Petrositis PA →/↓ ↑ Rim-
PA Expansile ↑ ↑ No Peripheral low-signal
PA No expansile
changes
the brain
occipital
ssure
PA/CPA
PA ↓ age
Aggressive
Bony
destruction
T1 T2 Contrast Peculiarity
hemosiderin ring (T2)
Consistency on T2
can be variable
reecting contents
↑ ↑ No Saturation on T1 fat
sequences
diffusion
→/↓ ↑ Ye s Can contain cystic
areas
appearance in larger
lesions
sequences
→/↓ ↑ Ye s Honeycomb
enhancement
↑ age
→/↓ →/↑ Yes
Meningeal thickening,
enhancing
enhancing Meckel
cave, cranial nerves
(especially cranial
nerves V and VI)
e tentorium inserts onto the petrous ridge to separate the middle and posterior
•
cranial fossae.
Relations of the PA include the petro-occipital ssure and clivus (medial), the inner
•
ear (lateral), the petrous carotid artery as it exits the foramen lacerum (anterior), the
CPA (posterior), the jugular bulb and inferior petrosal sinus (inferior), the middle
cranial fossa and Meckel’s cave (superior).
Dorello’s canal carries the sixt h cranial nerve and is found at the medial end of petrous
•
ridge at the conuence of the inferior petrosal and cavernous sinus.
Clinical Conditions
Cholesterol granulomas and epidermoids: Cholesterol cysts or granulomas are
•
thought to arise from haemorrhage into the air cell system causing an inammatory
reaction. Causative theories for this bleeding include Eustachian tube dysfunction
and marrow exposed to the air cell system. Epidermoid lesions are thought to originate from transplantation of epithelial cell rests by the laterally migrating optic and
126 e Ear
LESIONS OF THE CEREBELLOPONTINE ANGLE, PETROUS APEX AND JUGULAR FORAMEN
Figure 23.1 Anatomy of the petrous apex. IAM, internal auditory meatus.
otic capsules or developing neurovasculature. While cholesterol granulomas oen
present with uctuating conductive hearing loss (presumably related to Eustachian tube
dysfunction or cyst content leakage), epidermoids are more likely to present with progressive sensorineural hearing loss. Epidermoids may present with progressive facial nerve
palsy while cholesterol granulomas rarely do. Trigeminal neuralgia, otalgia and ear pain
can feature in cholesterol granulomas but this is unusual for epidermoids. Epidermoids
show low signal on Tl-weighted images, while cholesterol granulomas exhibit high signal.
Both types of cyst give high signal on T2-weighted images, but they can exhibit signal
inhomogeneity depending on the nature and amount of cyst content.
22. VESTIBULAR SCHWANNOMA
Factors that must be considered when considering treatment approach include patient’s
symptoms, life expectancy and surgical anatomy. Neural decits are rarely reversed by surgery. Figure 23.2 shows a proposed approach to management. Most cholesterol cysts can be
drained into the mastoid or sphenoid system, allowing hearing to be retained. Approaches
include the infra-labyrinthine and infra-cochlear approach (both limited by the height of
the jugular bulb) and the trans-sphenoidal approach (limited by the position of the carotid).
Drainage is associated with higher recurrence rate. For patients with facial palsy, pain, recurrent cysts and without serviceable hearing, resection may be favoured. A middle fossa, or
subtotal petrosectomy + cochlear drill out may be used for small cysts, whilst an infratemporal fossa type B approach can be used for larger lesions.
Infection: Petrous apicitis may present with middle ear infection, retro-orbital pain
•
and sixth nerve palsy.
Tumours: Chordomas arise from notochord remnants and are locally malignant
•
(regional metastasis rare) and have a high tendency to recur. Chordomas almost always
arise in the midline, and spread to the PA is common. ey can present indolently with
headache, visual disturbance or lower cranial nerve palsies. Chondrosarcomas likely
develop from cartilaginous remnants from development. ey too present insidiously
and can cause various cranial nerve palsies. Surgery is considered the standard of care
in the treatment of skull base chordomas and chondrosarcomas. Radiation therapy,
in the form of proton beam therapy, stereotactic radiosurgery (SRS) or conventional
fractionated radiation, is oen used as adjuvant therapy.
e Ear 127
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