The translabrynthine approach is used to surgically remove vestibular schwannomas. It provides the most direct exposure of the cerebellopontine angle but results in total hearing loss. The key steps involve complete mastoidectomy and labyrinthectomy to access the internal auditory canal. This allows for identification and preservation of the facial nerve while fully exposing the tumor for removal. Though it sacrifices any residual hearing, it allows for quick recovery and excellent postoperative facial nerve function outcomes.

1. By
DR Mohammed
Riyas

2. INTRODUCTION
 An acoustic neuroma (also called
vestibular schwannoma) is a
benign tumor arising from
abnormally proliferative shwann
cells , which envelope the lateral
portion of the vestibular nerve in

3. Little things about
CP angle

4. CP angle tumors
 Represents 10 % of all intracranial
tumors.
 Fatal without treatment.
 VS account for 78 % of CPA tumors
- mostly from vestibular branch of
VIIIth Nerve.
 Variety of other tumors arise from
this area like meningioma , CN
swannomas , dermoid tumors ,
arachnoid cysts ,lipomas ,

5. Anatomy of CP angle
 CPA – Irregularly shaped potential
space in the posterior fossa of the
brain .
 Anteriorly – posterior surface of
temporal bone .
 Posteriorly – anterior surface of the
cerebellum.
 Medially – cisterns of the pons &
medulla and olive.
 Superiorly – inferior border of pons

8. Anatomy of CP angle
 CN s V ( superiorly ) , IX,X,XI
(inferiorly ) transverse the cephalic
and caudal extent of the CPA.
 The central structures crossing the
CPA to & from the IAC are CN VII &
VIII s carrying with them a fine
sheet of arachnoid tissue upto IAC.
 Schwann cells sorround these
nerves beginning in the IAC , near
the porus at the Obersteiner-
Redlich zone.

9. Anatomy of CP angle
 CN s V ( superiorly ) , IX,X,XI
(inferiorly ) transverse the cephalic
and caudal extent of the CPA.
 The central structures crossing the
CPA to & from the IAC are CN VII &
VIII s carrying with them a fine
sheet of arachnoid tissue upto IAC.
 Schwann cells sorround these
nerves beginning in the IAC , near
the porus at the Obersteiner-
Redlich zone.

10. Anatomy of CP angle
AICA is the main artery in the
CPA and is the source of the
labrynthine artery .
The labrynthine artery
courses via the IAC & is an
end artery for the hearing and
balance organs.

11. Vestibular schwannoma
Nerve sheath tumors of the
superior and inferior
vestibular nerves.
They arise in the medial part
of the IAC or the lateral part
of the CPA and cause clinical
symptoms by displacing ,
distorting or compressing

12. Vestibular schwannoma
 Mean incidence range – 9.1 tmr/yr to
13 tmr/yr( as per SB)
 0.7 to 1.2 VS per lakh population/yr (
ballenger )
 Types - Sporadic ( 95%) and non
sporadic ( 5%)
 Age of presentation – 40 to 60 yrs.
 Age of presentation is less in non
sporadic ( 20-30 yrs )

13. Tumor biology
 Equal frequency in sup and inf
vestibular ( but recent japanese
studies suggested 85 % from inf
vestibular )
 Arise from schwann cells within
the IAC – lateral to O-R zone in the
area of scarpa ganglion.
 Schwannomas rarely arise from
the cochlear nerve & are rarely

14. Tumor pathogenesis
 Owing to mutations in the gene for
the tumor suppresor protein MERLIN
located on chr 22q12.
 Formation of VS requires mutation of
both copies of the merlin gene.
 Somatic mutations in both copies of
merlin gene results in sporadic VSs .
 Familial VS occuring in NF 2 requires
only one somatic mutation event .(
inherit one )

15. Tumor pathogenesis
 NF2 is autosomal recessive at gene
level but inheritance is autosomal
dominant ( pseudodominant )
 A mutation in the normal allele leads
to bilateral VS by the age of 20.
 Genetic screens for the NF2 mutation
have been developed and are the basis
for genetic counselling for family
members of NF2 patients

16. Tumor pathogenesis
 Biochemical factors- VS express
neuregulin ,which controls survival
and proliferation of schwann cells and
its receptors erbB2 & erbB3.
 FGF ,TGF B1 , PDGF & VEGF all these
contribute to VS proliferation.
 VS may accelerate during pregnancy.

17. pathology
 GROSS :
◦ VS have a smooth surface with a yellow to
gray color.
◦ Tumor is usually solid ,with occasional
cystic components and therefore has a
firm to soft texture depending on solid to
cystic components.
 MICROSCOPIC :
◦ Capsule – 3 to 5 micrometer in thickness.
◦ Two morphological tissue types – Antony
A & Antony B areas

18. T UMOR DEVELOPMENT
Develops in nerve sheath
Compresses rather than invading the
nerve
Gradually fills all the IAC
Protrudes out of the porus

19. T UMOR DEVELOPMENT-
extrameatally
Extrameatal expansion into the large &
empty pontine cistern
Displacement and stretching of the VII &
VIII th CN on the anterior
Compress cerebellum and trigeminal N
aspect of the tumor & of the AICA
on the inferior aspect
(During this time IAM continues to become
more & more widened )
which leads gradually to
hydrocephalus

20. T UMOR DEVELOPMENT-
extrameatally
Tumor may extent to the tentorium & can
obstruct the
cochlear aqueduct
The AICA & lower cranial nerves are also
displaced & become closely
Overtime , the trigeminal & abducens
Adherent to the inf surface of
tumor.
over the surface of the tumor and
get thinned.

21. 1. 2.
3.
4.
INTRACANALICULAR CISTERNAL
COMPRESSIVE HYDROCEPHALIC

22. Tumor development…..
 Periods of growth are intermixed
b/w slow growth & peroid of
quescence.
 Occasionally tumor may undergo
rapid expansion owing to cystic
degeneration or hemmorhage into
the tumor.
 The initial intracanalicular growth
effects the vestibulocochlear nerve

24. Stage 1
Stage 2
Stage 3

26. Cerebellopontine Angle:

27. Large Acoustic Neuroma: Tumors over 2.5 centimeters (this one is 2.6 cm) become impacted
into the brainstem and cerebellum. Complications associated with surgery and radiation are
higher. It is difficult to deliver an adequate dose of radiation to control tumor growth without
excessive dosing to the brainstem in tumors larger than this.

29. Symptoms & signs
 Intracanalicular:
◦ Hearing loss (UL progressive ), tinnitus, vertigo
◦ Loss of speech discrimination out of propotion to HL
 Cisternal:
◦ Worsened hearing and dysequilibrium
 Compressive:
◦ Occasional occipital headache
◦ CN V: Midface, corneal hypesthesia
◦ CN VII : Hitzelberger’s sign, loss of taste and reduced
lacrimation on Schirmer’s test ,facial weakness ( late)
◦ CN II , IV , VI : visual acquity and diplopia

30. Symptoms & signs
 Hydrocephalic:
◦ Fourth ventricle compressed and obstructed
◦ Headache, visual changes, altered mental status
◦ Nausea and vomiting
◦ On examination : ICP and pappiledema.
 Compression of CN IX & X
◦ Dysphagia , aspiration and hoarseness
◦ Poor gag reflex and VC paralysis.
 Cerebellar involvement( late )
◦ Incoordination , widely based gate , tendency to fall
owards affected side

31. Symptoms & signs
 Brainstem involvement:
• There is ataxia, weakness and numbness of arms and legs
with exaggerated tendon reflexes.

32. Jackler Staging System
STAGE TUMOUR SIZE
Intra canalicular Tumour confined to IAC
I (Small) <10mm
II(Medium) 11-25mm
III(Large) 25-40mm
IV(Giant) >40mm

33. Tumor Growth Rate

34. Duration of Symptoms Prior to
Diagnosis
SYMPTOMS YEARS
Hearing loss 3.9
Vertigo 3.6
Tinnitus 3.4
Headache 2.2
Dysequilibrium 1.7
Trigeminal 0.9
Facial 0.6

35. Diagnostic evaluation
 Average patient will require 4 years from the
onset of symptoms to diagnosis.
 Majority will present with complaints of UHL, UT,
Vertigo , dysequilibrium, facial numbness ,
weakness or spasm.
 Initial step in evaluation includes an audiologic
assessment .if it suggests a retrocochlear lesion ,
then imaging of the CPA is performed .
 Vestibular testing lacks specificity in diagnosis of VS

36. AUDIOLOGICAL EVALUATION
 Includes PTA , Speech discrimination score
(SDS) , Acoustic reflex threshold & acoustic
reflex decay
 PTA of patients with VS shows assymetric ,
down sloping , high frequency SNHL in almost
70% of patients

37. AUDIOLOGICAL EVALUATION
 Retrocochlear HL causes SDS to be lower than
predicted by the pure tone thresholds.
 This out of propotion is furthur accenuated
when retested at a higher speech intensity
( roll over phenomenon )
 Loss of acoustic reflex or acoustic reflex decay is
noted in most patients with VS

38. audiological tests
Cochlear Retrocochlear
a) Pure tone audiometry Sensorineural hearing loss Sensorineural hearing loss
b) Speech discrimination
score
<90% Very poor
c) Roll over phenomenon Absent Present
d) Recruitment Present Absent
e) SISI Over 70% 0-20%
f) Threshold tone decay
test
<25db >25db
g) Stapedial reflex Present Absent
i) Stapedial reflex decay
test
Normal Absent

39. VESTIBULAR TESTING
 Not sensitive nor specific for diagnosing VS
 The MC test used is ENG with caloric testing.
 Shows reduced caloric response in the affected ear.
 The extent of vestibular function present predicts the
amount of post op vertigo.
 The location of VS on the inf or sup Vestibular N may
also be predicted.

40. AUDITORY BRAINSTEM RESPONSE
 In patients with VS , the ABR is partially or
completely absent , or there is a delay in
latency of wave V on the affected side.
 An interaural delay of wave V greater than
0.2 ms is considered abnormal. ( 40-60 % )
 Overall ABR has a sensitivity of > 90% &
specificity of > 90 % in detecting VS.

41. AUDITORY BRAINSTEM RESPONSE
 In 20-30 % there are no identifiable
waveforms even with insignificant HL in
higher frequencies.
 In 10-20 % only wave I is present.

42. BERA patterns in AN

43. Imaging studies
 VS is definitely identified MC via an imaging study.
 Earlier plain film radiograghs and polytomographs
 Introduction of CT in 1970 allowed axial imaging
with improved bone & soft tissue evaluation.
 With the addition of iv iodinated contrast agent
,90 % of VS are enhanced furthur improving
diagnostic accuracy.

44. Imaging studies
 Intracanalicular tumors & tumors extending less
than 5 mm into the CPA frequently are missed
with contrast enhanced CT.
 Accuracy improved by air-contrast cisternography.
 MRI was introduced in 1980 & has become the
GOLD standard for VS

45. Imaging studies
 MRI :
 VII & VIII nerves as well as cerebellum ,brainstem , vasculature
& other structures are well visualized on MRI
 The addition of gadolinium furthur enhanced the diagnostic
accuracy
 Typically a series of T1 weighed images in which CSF is dark
and fat is bright, T1 with gadolinium contrast , T2 In which
CSF is bright is used.
 A hypointense globular mass centered over the IAC on T1 With
enhancement on gadolinium.
 VS are iso-to hypointense on T2.
 T2 fast spin echo MRI without contrast as screening.

46. MRI Brain
Isointense to brain,
hyperintense to CSF
Hyperintense to brain,
hypointense to CSF

47. management options
 The primary management of VSs is surgical removal.
 Roles of observation and radiotherapy are currently for
the pts,who cannot tolerate a surgical procedure or have
a life span of < 5 yrs.
 Surgical approaches to the CPA include:
◦ Translabrynthine
◦ Retrosigmoid
◦ Middle fossa craniotomies.

48. management options
 The appropriate approach for a particular
pt. is based on the hearing status , size of
the tumor , extent of IAC involvement and
experience of the surgeon
 The approaches are either hearing
preservative or ablating.
 The retrosigmoid & middle fossa
approaches are hearing preserving, while
translabrynthine approach is otherwise.

49. management options
 The middle fossa approach is well suited for the
pts with good hearing and tumor<2cm.
 The retrosigmoid approach is well suited for
those with good hearing and tumor<4cm and
not involving the lateral part of IAC.
 The translabrynthine approach causes total
hearing loss and so is appropriate for the pts with
poor hearing(PTA>30dB) or pts with good
hearing and tumors not accessible by the hearing
preserving approach.

50. management options
 Three critical issues inherent to all the three techniques are:
◦ Extent of exposure of IAC and CPA
◦ Identification and preservation of the facial nerve
◦ extent of brain retraction
 These operations use electro physiologic
monitoring of CN VII and ABR in hearing
preserving approach.

51. Middle Fossa Approach.
Translabyrinthine Approach
Suboccipital Approach
Surgical Approaches
Factors that influence surgical approach selection
•Age
•Hearing status
•Tumour size
•Surgeon’s preference.

52. Translabrynthine approach
 The primary approach for removal of VS.
 Most direct route to the CPA & requires
minimal cerebellar retraction.
 Identification of facial n is possible.
 Surgeons can ensure complete removal bcz
fundus of IAC is widely exposed.
 Immediate repair of facial n possible.
 Recovery is quite rapid with minimal pain and
excellent facial n results

53. Translabrynthine approach
 Obvious disadvantage is sacrifice of any residual
hearing.
 Technique :
◦ A postauricular incision is made 2 cm behind sulcus
◦ Complete mastoidectomy is done,with identification of
the middle fossa dura, sigmoid sinis , LSSC , fossa incudis
& facial n
◦ The sigmoid sinus is decompressed with a diamond burr

54. Translabrynthine approach
◦ A labrynthectomy is begun by removal of bone in the
sinodural angle along the horizontal scc
◦ Each SCC is then opened and followed into the vestibule,
with care taken to identify the ampulla of each SCC and
the subarcuate artery
◦ A bone is removed along the posterior fossa dura medial
to sigmoid sinus , the endolymphatic duct and sac are
encountered.

55. Translabrynthine approach
◦ Jugular bulb location is defined by locating ampulla of
posterior canal. ( inferior extent of dissection )
◦ Bone is removed around the inferior aspect of IAC until
the cochlear aqueduct is identified
◦ Posterior aspect of the canal is skeletonized until the
superior edge of the internal canal is identified
◦ Bone is then carefully removed between th e middle
fossa dura & the IAC

56. Translabrynthine approach
◦ Once the medial portion of the IAC is exposed for 270
the remaining piece of porus may be carefully removed
◦ Laterally the transverse crest should be identified at the
fundus of the IAC.
◦ Superiorly , the Bills Bar is identified together with the
labrynthine portion of the facial n
◦ The posteroir fossa dura is opened inferior to and parallel
to the superior petrosal sinus over the midportion of the
IAC
0

57. Translabrynthine approach
◦ Using the bills bar as guide , and with a fine hook , the
surgeon seperates the superior vest n from facial nerve.
◦ The capsule of the tumor is incised , & the tumor is
gutted with house urban dissector
0

59.  Radiotherapy :-
1. Conventional radiotherapy by external beam
has no role in the treatment of Acoustic Neuromas
due to low tolerance of CNS to radiation.
2. X – or Gamma knife surgery.

60. THANK YOU