acoustic neuroma vestibular schwanoma

1. Vestibular
Schwannoma
Dr. Aditya ghosh roy
3nd year PGT
NRSMCH

3. HISTORY
• 1777- First observed on autopsy.
• 1833- Sir Charles Bell- first clinical case report of
vestibular schwanoma.
• 1894- First successful removal of vestibular
schwanoma by Charles A Balance.
• 1902- Henneberg & Koch introduced the term CP
angle.

4. • Cushing described 6 stages of ‘VS’/CP angle tumor:
• 1) Auditory and labyrinthine manifestation.
• 2) Occipito- frontal pain and sub occipital
discomfort.
• 3) Cerebellar signs.
• 4) Cerebral nerve involved.
• 5) Increased ICT + papilledema.
• 6) Dysarthria, dysphagia cerebellar cries
respiratory difficulty

5. • 1925- Dandy modified Cushing’s technique and
reduced mortality rates.
• 1949- Atkinson published autopsy studies.
- AICA occlusion cause of mortality.
• Quix- trans labyrinthine approach
• 1961- House used the middle fossa approach.
• 1964- House used the trans labyrinthine approach
with great success.
• 1973- Smith et al advocated the microscopic sub
occipital approach for preservation of hearing.

6. Epidemiology
• 6 % of all Intracranial tumors
• 80 - 90% of CPA tumors
• Vast majority in adulthood
• No known race, gender predilection
• 95% Sporadic (unilateral, around 50 yrs)
• 5% Neurofibromatosis type 2 (bilateral, younger
age)
95% chance of b/l VS, meningioma, ependymoma,
spinal cord & peripheral schwannoma.

7. Pathology
• Benign
• well circumscribed
• unencapsulated tumors
• arising from Schwann cells of vestibular nerve
• Malignant degeneration exceedingly rare
• Majority originate near the fundus of IAC
• lateral to Obersteiner- Redlich junctional zone

8. Macroscopic app
• Yellow pinkish grey
• Consistency
• Large tumour
• Cystic

9. Microscopic app.
• Antoni A - closely
packed cells with small
spindle-shaped and
densely stained nuclei.
A whirled appearance of
Antoni type A cells is
called a Verocay body
• Antoni B -looser cellular
aggregation of
vacuolated pleomorphic

11. 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

12. Phases of Tumor Growth
• Intracanalicular:
o Hearing loss, tinnitus, vertigo
• Cisternal:
o Worsened hearing and dysequilibrium
• Compressive:
o Occasional occipital headache
o CN V: Midface, corneal hypesthesia
• Hydrocephalic:
o Fourth ventricle compressed and obstructed
o Headache, visual changes, altered mental status

13. Phases of Tumor Growth
Jackler RK. 2000, p. 180: Tumors of the Ear and Temporal Bone
Intracanalicular Cisternal
Compressive Hydrocephalic

14. SYMPTOMS AND SIGNS
CLINICALLY :
• Otological Stage
• Stage of Vth nerve involvement
• Stage of Brainstem and cerebellar compression
• Stage of rising Intracranial tension
• Terminal Stage

15. • OTOLOGICAL STAGE
DEAFNESS
U/L SNHL, gradual 2-20yrs.
DUE TO = Direct compression of 8th nerve and also
interruption of blood supply of auditory nerve and cochlea.
TINNITUS
I/L, high pitched continuous
VESTIBULAR DYSFUNCTION
Small tumours = Vertigo, Large tumours = Dysequilibrium

16. • STAGE OF TRIGEMINAL NERVE INVOLVEMENT
Absent corneal reflex
Facial nerve involvement leads to facial numbness and
facial muscle weakness
• STAGE OF BRAINSTEM AND CEREBELLUM
INVOLVEMENT
Ataxia, dysmetria, past pointing, dysdiadokokinesis,
disturbance of gait, intention tremors,
Spontaneous nystagmus, dysynergia. (Cerebellar signs
Usually seen when tumour >4cm size)
• STAGE OF INCREASED INTRACRANIAL PRESSURE
Headache, Vomiting, neck rigidity, raised ICT.
• TERMINAL STAGE
Failures of vital centers in brainstem

17. GROWTH RATE AND
GROWTH PATTERN
• Mean growth rate 1.1 mm / yr (Scott Brown)
Growth patterns
1. Continuous growth
2. No measurable growth
3. No measurable growth followed by continuous growth
4. Negative growth
5. Various positive growth patterns

18. DIAGNOSIS
• Neuro otological
• Audiometry
• Vestibular studies
• Imaging

19. Neuro otological
• Nystagmus
o Early small lesion: Horizontal (vestibular)
o Late large: Vertical (brainstem compression
• Cerebellar signs
o Romberg test
o Fukuda stepping test
o Finger nose test
o Ataxic gait

20. • Cranial nerve
o Eight
o Fifth
o Seventh
hitzelberger sign
o Late stages

21. Audiological tests
• PTA
- Asymmetric unilateral SNHL
- More in higher frequencies
• Speech discrimination poor; Roll over phenomenon
present
• SISI low
• ABLB no recruitment
• Tone decay –high ,retrocochlear hearing loss
• Stapedial reflex absent

22. Pure Tone and Speech Audiometry
Down-sloping / High Frequency
Decreased Speech Discrimination

23. • Performance intensity function for phonetically
balanced words
• Sds at high sensation level
• Phenomenon of roll over – retrocochlear pathology

24. ABR: Retrocochlear
Pathology
• Increased interpeak intervals
o I-to-III interval of 2.3ms
o III-to-V interval of 2.1 ms
o I-to-V interval of 4.4 ms
• Interaural wave V latency difference
(IT5)
o Greater than 0.2 ms
• Poor waveform morphology
• Absent waveform

25. 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

26. ABR: Diagnostic
Efficiency
• Generally, Efficiency increases with Size
• Sensitivity: > 90 % for tumor > 3 cm
58-89% for tumor <1 cm
• No response for severe/ profound SNHL ( > 70 dB )

27. Stacked ABR
• Computed by aligning the wave
5 of five derived band bera and
adding together the amplitude
of five wave 5
• Attempt to improve detection
rate in small < 1 cm ANs
• “Stacking” of derived band
response

28. Vestibular Studies
• Caloric test- measures the response of lat scc which
is innervated by sup vestibular nerve
• VEMP- measures the response of inf vestibular
nerve
The significance is that hearing preservation may be
more difficult in tumor that arises from inf vestibular
nerve due to proximity to cochlear nerve

29. MRI
• T1 wt image hyperintense to csf
• Hypointense to gray matter
• T2 wt image hypointense to csf
• Hyperintense to gray matter

30. • Gold standard is gd enhanced t1 images
• T2- weighted fast spin echo( FSE ):
• T2 wt image hypointense
• Quicker,Screening
• 3D- constructive interference in steady state
( CISS ): assessment of fundal involvement
• 3D- fast imaging using steady state
acquisition: improve cisternal imaging

31. CT Brain with contrast

32. • Erosion of iac
• Subtle erosion cochlea and vestibule
• Less soft tissue detail
• Contrast agent required
• Heterogeneous enhancement on contrast
• More sensitive to differentiate acute intracerebral
bleeds than MRI
• Contraindication to MRI (metallic implants),
claustrophobic patients
• May not be able to detect small tumor < 1.5cm
• Radiation

33. Air Contrast CT
• Air outine small intracanicular tumour

34. Treatment options
• Observation
• Surgery
o Translabyrinthine
o Retrosigmoid
o Middle fossa
• Radiotherapy
o Conventional
o Stereotactic

35. Thank you
• To be continued

36. Observation
• Advanced age (> 65 )
• Short life expectancy (< 10 years)
• Slow growth rate
• Poor surgical candidate / poor general health
• Minimal symptoms
• Only hearing ear
• Patient’s preference

37. Growth rate prediction
• Younger age
• Larger tumor
• NF2-associated
• Cystic
• Recurrent
• CP angle tumor

38. Stereotactic radiation
Advantages Disadvantages
• Decreased hospitalization
• Elderly or medically infirm
patients
• Risks avoided ( infection,
CSF leak )
• Tumor recurrence after
surgery
• Repeated MRI
• Viable tumor
• Hydrocephalus, facial or
trigeminal neuropathy
• Sudden hearing loss
• Difficulty in preserving facial
nerve in surgical salvage
• Radiation induced
malignancy

39. Microsurgery
Approach selection:
Middle fossa- preserve hearing ( ideal for PTA <30 Db, SD
>70%), small tumors ( 1-1.5 cm ), fundus of IAC, temporal
lobe retraction
Translabyrinthine- preferred for pt without hearing, tumors all
sizes, excellent exposure of CPA, widest exposure of facial
nerve, avoidance of cerebellar or temporal lobe retraction
Retrosigmoid- tumors all sizes, better exposure of CPA,
possible hearing preservation, poor view to fundus, cerebellar
retraction
Combined- tumors greater than 4 cm or that have traverse
intracranial compartments

40. Translabyrinthine
approach

43. Middle fossa approach

46. Retrosigmoid approach

48. THANK YOU