Download 5% Neurofibromatosis type 2 (bilateral)

Acoustic Neuroma
Department of Otorhinolaryngoglogy
the 2nd Hospital affliatted to Medical college
Zhejiang University
Xu Yaping
Anatomy
Cerebellopontine Angle-CPA (in the posterior fossa)
Epidemiology
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6 % of all Intracranial tumors
80 - 90% of CPA tumors
Incidence in US: 10 per million / year
Vast majority in adulthood
95% Sporadic (unilateral)
5% Neurofibromatosis type 2 (bilateral)
No known race, gender predilection
Pathogenesis
• Neither neuroma or acoustic (auditory)
• Schwannoma arising from vestibular nerve
• Benign tumor. Malignant degeneration exceedingly
rare.
• Majority originate within the IAC(the internal
auditory canal)
• Equal frequency on Superior and Inferior vestibular
nerves (controversial)
Jackler Staging System
Stage
Tumor Size
Intracanalicular
Tumor confined to IAC
I (small)
< 10 mm
II (medium)
11-25 mm
III (Large)
25-40 mm
IV (Giant)
> 40 mm
Phases of Tumor Growth
• Intracanalicular:
– Hearing loss, tinnitus, vertigo
• Cisternal:
– Worsened hearing and dysequilibrium
• Compressive:
– Occasional occipital headache
– CN V: Midface, corneal hypesthesia
• Hydrocephalic:
– Fourth ventricle compressed and obstructed
– Headache, visual changes, altered mental status
Intracanalicular
Compressive
Cisternal
Hydrocephalic
Hearing Loss
1. Most frequent initial symptom
2. Most common symptom ~ 95% AN patients
3. Asymmetric SNHL
4. Down-sloping / High Frequency
5. Decreased Speech Discrimination
6. Lack of conclusive correlation between tumor
size and hearing
Estimating Tumor Growth
• Serial MRI with and without GAD(Gadolinium)
---The only reliable study to estimate tumor growth
rate
• Gadolinium-enhanced MRI remains the gold
standard
---It can detect tumors as small as 1 mm and
differentiate AN from many CPA lesions
Delayed Diagnosis
Duration of Symptoms Prior to Diagnosis
Symptoms
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Hearing Loss
Vertigo
Tinnitus
Headache
Dysequilibrium
Trigeminal
Facial
Years
3.9
3.6
3.4
2.2
1.7
0.9
0.6
----Jackler RK. 2000. Tumors of the Ear and Temporal Bone
History and Physical
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Hearing Loss
Vertigo
Dysequilibrium
Tinnitus
Headache
Nystagmus
– Early small lesion: Horizontal (vestibular)
– Late large: Vertical (brainstem compression)
• Cranial neuropathy
– CN V, VII
– Lower cranial nerves (IX-XII)
Sudden Sensorineural Hearing loss
• Idiopathic
• 1-2 % SSNHL patients have AN
• 10- 26 % AN patients have a history of SSNHL
• Most experts advocate obtaining MRI in all patients
who present with SSNHL
Diagnosis
• History and Physical Exam
• Audiology testing:
– Audiogram
– ABR
– OAE
• Vestibular testings (eg. ENG, rotary chair,
posturography) all lack diagnostic value
• Radiography
– MRI
– CT
Gold Standard
Pure Tone
ABR: Retrocochlear Pathology
(Auditory Brainstem Response)
• Increased interpeak intervals
– I-to-III interval of 2.5 ms, III-to-V interval of 2.3
ms, and I-to-V interval of 4.4 ms
• Interaural wave V latency difference (IT5)
– Greater than 0.2 ms
• Poor waveform morphology ie. only some of
the waves are discernible
• Absent waveform
ABR patterns in AN
•10-20 % with only wave I
and nothing thereafter
•40-60 % with wave V
latency delay
•10-15 % have normal
findings
OAE(Otoacoustic emissions)
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Reflect cochlear/ OHC / sensory hearing
Not primarily used as screening tool
Presence of OAE in SNHL ↔ Retrocochlear
However, 50 % AN demonstrate both cochlear and
retrocochlear hearing loss
• Risk stratification for hearing preservation surgery
MRI Brain w. & w/o GAD
T1 pre-Gad
T1:
T2:
T1+Gad:
T2
T1 post-Gad
Isointense to brain, hyperintense to CSF
Hyperintense to brain, hypointense to CSF
Enhancing
CT Brain with contrast
1. Heterogeneous
enhancement on contrast
2. Rare calcification
3. Contraindication to MRI
(metallic implants),
claustrophobic patients
4. May not be able to
detect small tumor < 1.5cm
5. Radiation
Treatment options
• Observation<5mm
• Surgery : >1cm
– Translabyrinthine
– Retrosigmoid
– Middle fossa
• Radiotherapy
– Conventional
– Stereotactic:  knife <1-2cm
Conservative Management
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Advanced age (> 65 )
Short life expectancy (< 10 years)
Slow growth rate
Poor surgical candidate / poor general health
Minimal symptoms
Only hearing ear
Patience preference
Conclusions
• Tumor size has no correlation with audiovestibular
symptoms in Acoustic neuroma
• Understanding tumor growth rate is important for
predicting symptom progression and treatment
planning
• The study-of-choice to estimate tumor growth is
serial MRI
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