This document discusses vestibular schwannoma, also known as acoustic neuroma. It begins by clarifying that this is a misnomer, as the tumor originates from schwann cells of the vestibular nerve, not the acoustic nerve. The document then covers the epidemiology, pathogenesis, clinical presentation, investigations including MRI and BERA, and various treatment options like observation, microsurgery via different approaches, and stereotactic radiotherapy. The goals of management are preservation of life, facial function, and hearing.

1. ACOUSTIC NEUROMA
Dr.AJAY MANICKAM

2. Misnomer
 Neither “acoustic” , nor neuroma.
 Schwann cells of vestibular division of eighth
cranial nerve
 In 1992, NIH Consensus Development
conference adopted the standard
terminology….

3. VESTIBULAR SCHWANNOMA

4. Skull base
 Composed of ethmoid,
sphenoid, occipital,
frontal & temporal
bones

5. Cerebellopontine angle
 Fluid-filled space of lateral
cistern
 Anterior – postr surface of
petrous bone
 Posterior – antr surface of
cerebellum
 Medial – inferior olive
 Superior – infr border of pons &
cerebellum
 Inferior – cerebellar tonsil

6. Arteries in CPA
 Loop of AICA often
traverses between the
7th & 8th cranial nerves
at their brainstem
entry site.

7. Tumours of CPA
 Vestibular schwannoma –
91.3%
 Meningioma – 3.1%
 Epidermoids – 2.4%
 Non-vestibular
schwannomas – 1.4%
 Arachnoid cysts – 0.5%

8. V.S. - epidemiology
 Most common skull-base neoplasm
 Most common temporal bone neoplasm
 6% of all intracranial tumours
 91% of CPA tumours
 No racial or gender predilection

9. Forms of V.S.
Sporadic With Neurofibromatosis
 95% of allVS
 Unilateral
 5th-6th decade of life
 NF type 2
 5% of allVS
 Bilateral
 Younger age
 NF type 1
 2% of NF1 develop unilateralVS

10. Pathogenesis
Obersteiner-Redlich zone  Originates within IAC
 Superior : inferior = 1:1
 Vestibular nerve myelination :
proximally by oligodendroglial
cells & distally by schwann cells
 Junction is the O-R zone,
situated near vestibular /
Scarpa’s ganglion, rich in
scwann cells

11. Genetics
 Chromosome 22q12 defect
 Sporadic – “double-hit” of 2
normal genes
 NF2 – 1 defective gene;
“single-hit” is enough
 Gene product – MERLIN –
inhibits IP3

12. Pathology - gross
 Smooth surface
 Bright yellow to gray in
colour
 Large tumours are often
cystic
 Unencapsulated
 Soft & friable to firm &
rubbery

13. Pathology - microscopic
Antoni A Antoni B
Densely packed-cells with small
spindle shaped nuclei
Loosely-arranged, vacuolated,
pleomorphic cells

14. Verocay body
Whorled pr palisading variety of Antoni A cells
Stains +ve for S-100 immunoperoxidase, neuron-specific enolase & vimentin

15. Growth pattern
 Benign, slow-growing tumour – 0.2cm / year
 Grows by cellular proliferation
 Tumor involution –
1. Spontaneous decompression of cystic areas
2. Tumour outgrowing blood-supply
 Rapid tumour expansion –
1. Cystic degeneration
2. Intratumour bleeding

16. Stages of growth
Intracanalicular – within IAC
Cisternal – displaces CSF,
AICA, 7th & 8th nerve

17. Brainstem compression –
touches laterlal pontine
surface & displaces 5th nerve
Hydrocephalic stage – 4th
ventricle effaced secondary
to brainstem compression

18. Clinical presentation
 Hearing loss –
 MC presenting feature
 Unilateral
 Sensorineural, initially at higher frequencies
 Sudden-onset SNHL in 26% cases
 Poor SDS score, disproportionate to PTA values

19. Cont.
 Tinnitus –
 2nd most common symptom >50% cases
 Constant
 Unilateral
 High-pitched

20. Cont.
Vertigo –
 Slow reduction of vestibular function –
central compensation – vertigo is rare
 Occurs in smaller tumours where
considerable vestibular function remains
 Self-resolving ( days to weeks )

21. Cont.
Dizziness –
 In brainstem compression stage of larger mass
 Due to uncompensated peripheral vestibular
disturbance & cerebellar compression
Large tumours compressing cerebellum –
 Dysmetria
 Truncal ataxia
 Hemiplegia, increased DTR ( long tract problem)

22. Cont.
 Trigeminal nerve dysfunction –
 Absent corneal reflex – earliest manifestation
 Mid-face hypoesthesia
 Occurs in brain-stem compression stage
 Occasional facial pain
 Motor fibres are more resistant to stretch than
sensory – so unilateral temporal wasting, masseter
atrophy & secondary malocclusion is rare.

23. Cont.
Facial nerve dysfunction –
 Rare as it is very resistant to stretch
 Hypofunction ( weakness / palsy ) or
hyperfunction (spasm or twich of orbicularis
oculi )
 Histelberger’s sign – hypoesthesia of postero-
superior part of EAC & conchal bowl
 Always exclude facial schwannoma

24. Cont.
Eye manifestation -
 Horizontal nystagmus beating away from
tumour side due to vestibular hypofunction
 Vertical nystagmus in brainstem compression
 Hydrocephalic stage – papilloedema, optic
atrophy, blindness – rare.

25. Investigations
Audiogram
 Unilateral, down-
sloping, high-frequency
SNHL
 Disproportionate SDS
score
 Screening tool

26. MRI
Gadolinium enhancement
 Central
hypointense
areas
represent
cystic
change

27. MRI – cont.
Ice-cream cone appearance NF2

28. BERA
 Most sensitive & specific audiological test
 Replaced by MRI as principal investigation
 BERA normal – 10-15% cases
 No waves – 20-30% cases
 Only wave 1 – 10-20% cases
 All waves present with delayed wave 5 latency – 40-60%
 Good hearing prognosis – no wave 5 latency with
preservation of wave 3

29. ENG
 Reduced ipsilateral response with horizontal
nystagmus is seen
 Poor specificity – not usually done
 Has prognostic value – if ‘–ve’ caloric test –
1. Less post-op vertigo
2. Better hearing outcome ( caloric –ve in LSC
involvement i.e. superior vestibular nv, which is
away from cochlear nv )

30. Treatment options
Observation
with serial
imaging
Microsurgery
• Translabyrinthine
• Retrosigmoid
• Middle cranial
fossa
Stereotactic
radiation

31. Goals of management
1
• Preservation of life
2
• Preservation of facial function
3
• Preservation of hearing

32. Observation
 Where patient can outlive the tumour
 Unfavorable patient factors (aged, poor health)
 Favorable tumour factors ( small, slow-growing )
 Poor surgical candidates
 Serial MRI ( 6monthly in 1st year – then yearly)
 Measure largest extrameatal diameter in axial cut
 Observe if <0.2 cm / year
 If >0.2 cm / year – surgery or radiotherapy

33. Microsurgery options
PTA with SDS
Good hearing
<1 cm – MF
1-2.5 cm – RS
>2.5cm –TL
(or RS if
limited IAC
extension)
Poor hearing TL

34. Complications
 Facial nerve transection – highest in MF
 Hearing loss – highest inTL
 Persistent post-op headache – highest in RS
 Retraction injury – cerebellum in RS, temporal
lobe in MF – encephalomalacia
 CSF leak – more in RS
 Recurrence – least inTL

35. Stereotactic radiotherapy
 Controversial role
 Primary t/t – smaller tumour in old age
 Avoid in young – long-term complications of RT
 Avoid in >3cm tumour – risk of oedema &
secondary brainstem compression
 Indefinite monitoring with MRI
 Good option in recurrence following microsurgery

36. NF2
 Primary management
followed by Auditory
Brainstem
Implantation
preferably in the same
sitting

37. THANK
YOU