Surgical management of vestibular schwannoma.

1. SURGICAL
MANAGEMENT OF
VESTIBULAR
SCHWANNOMA
- DR. DHIRENDRA V. PATIL
M.S. (ENT)
J.N.M.C., Aligarh Muslim University.

2. INTRODUCTION
 For many years the management of
vestibular schwannoma (VS) did, in fact,
nearly always mean surgical management.
 The main reason for this was late
diagnosis.

3.  Most large centres now adopt a ‘wait and
rescan’ policy for tumours confined to the
internal auditory meatus (IAM), or with
limited extension into the cerebellopontine
angle (CPA).

4. HISTORY
 It remains unclear whether it was
Ballance in London, or Annandale in
Edinburgh who performed the first
successful VS removal.
 They performed these operations through
the suboccipital approach.

5.  William House, in the 1960s,
proposed surgery as soon as the
diagnosis could be made and
suggested the translabyrinthine
approach to the CPA.
 The logic of letting a small- or
medium-sized tumour to become a
large or giant tumour before
performing an operation was
unacceptable to him.

6.  House endured many hostile confrontations
with the ‘neurosurgical community’
whose objections were as much due to the
fact that ‘otologists’ were becoming
involved with this type of surgery as with
the approach itself.
 The ‘best’ approach is the approach that
gives the best results in the hands of the
individual surgeon.

7. RELEVANT
ANATOMY

8.  An axial
view of
the skull
through
the level
of the
IAC and
CPA.

9. Various Approaches

10.  Most vestibular schwannomas
originate in the region of the IAC,
enlarging the porus and extending
into the cerebellopontine angle.

11. IAC

12. Tumour Behaviour

13.  Schematic illustration of initial growth of VS

14.  Schematic illustration of intrameatal expansion
of VS

15.  Schematic
illustration of
expansion of
VS in the
cerebellopont
ine angle

16. SURGICAL
APPROACHES TO THE
CEREBELLOPONTINE
ANGLE

17. SURGICAL APPROACHES TO THE
CEREBELLOPONTINE ANGLE

19. Translabyrinthine
Approach

20. Translabyrinthine approach
 This is now the favoured approach for
the removal of VS for the majority of
neurotologists.

21. The key stages in the
operation are
 1. skin and periostial flaps;
 2. extended cortical mastoidectomy;
 3. bony labyrinthectomy;
 4. skeletonization of the jugular bulb and
vertical portion of the facial nerve;
 5. skeletonization of the internal auditory
meatus;

22.  6. identification of the facial nerve at the lateral
end of the internal meatus;
 7. opening of the posterior fossa through the
dura of the posterior surface of the petrous
bone;
 8. removal of tumour using standard
neurosurgical techniques;
 9. closure with obliteration of the middle ear
and petrosectomy defect, usually with
abdominal fat.

23. Skin incision
 A curved incision above and behind the
pinna is planned, it can be about 3-4 cm
behind the postauricular sulcus.

24. Vid-1

25. Cortical mastoidectomy

26.  Using cutting and coarse diamond paste
burs, bone is removed up to the middle
fossa dura, exposing it widely.
 This allows easy retraction of the dura with
the instruments during tumour removal.
 In a similar manner, bone is removed from
the sigmoid sinus and from the bone
overlying the posterior fossa dura for 2 or 3
cm behind the sinus.

27. Cortical mastoidectomy
 The secret of the operation is the extent of
the bone removal (Figure)

28.  Dural elevation
permits insertion
of retractors,
which augments
the exposure of
deeper
structures.

29.  Some surgeons like to leave an island of thin
bone over the sinus that can be retracted with
the sinus and provides some protection for
the sinus.

30. Bony labyrinthectomy
 A standard total bony labyrinthectomy is
performed (Figure)

31.  Removal of the
semicircular
canals is
commenced in
the sinodural
angle.

32.  Care must be taken in drilling out the ampulla
of the posterior canal, which lies medial to
the second genu of the facial nerve.
 The ampulla of the superior semicircular
canal should be retained, as it is a landmark
for the superior vestibular nerve (SVN).

33.  Labyrinthectomy
is then
deepened to
open and then
remove the
SCCC.

34.  The endolymphatic duct can be traced
from the vestibule along the line of the
common crus where it turns though 90
degree towards the posterior fossa dura
and widens out to become the sac.

35.  At this stage the
endolymphatic
sac and duct are
exposed.
 The duct wraps
around the
common crus on
its J shaped route
to the vestibule.

36.  Labyrinthectomy
is completed
with a diamond
burr to identify
the horizontal
and second
genu portions of
FN.

37. Vid-2 (Labyrinthectomy)

38. Skeletonization of the
jugular bulb and the
vertical
portion of the facial
nerve

39.  The jugular bulb is the lower limit
of bone removal and in nearly all
cases bone should be removed down
to its level.

40.  Once the
facial nerve is
located, the
remaining
portion of
sigmoid sinus
is uncovered,
in a direction
of jugular
bulb.

41.  The IAC lies in
the deep bone
to the
labyrinth(fig).

42.  The retrofacial air cells are
exenterated and bone may be
removed over the vertical portion of
the facial nerve until the sheath is
visible through the bone.

43. Vid-3 (left ear)

44. Skeletonization of the
internal meatus

45.  Exposure of the
internal auditory
canal
commences with
a cutting burr.
 Canal courses
posteriorly after
taking its origin
at the vestibule.

46.  Once the
plane of the
IAC has been
identified,
troughs are
drilled above
and below the
canal, parallel
to its long
axis.

47.  Bone is
removed
along the
posterior
petrous face
medial to the
porus
acosticus.

48.  A diamond
burr is used
to remove
the last
eggshell
thin piece
of bone
over the
canal dura.

49.  Before
removing the
remaining
bone from the
floor and roof
of canal, the
dura is
elevated from
the remaining
bony shell.

50.  The remaining
superior and
inferior bony
plates are
removed with a
diamond burr
while gently
displacing the
contents of
canal.

51.  The transverse
crest is a
prominent bony
landmark
separating SVN
and IVN.

52.  A U-shaped
gutter is
drilled above,
behind and
below the
internal
meatus
(Figure).

53.  The extent of bone removal should be
approximately 270 degrees round
the meatus, and is much faster if the
temporal bone is well pneumatized.

54.  One should constantly keep in mind
the position of the facial nerve in
the anterosuperior quadrant of
the meatus, and remember that in an
expanded meatus it may, in fact, be
very close to the middle fossa.

55.  At the lateral end of the meatus the
transverse crest and the canal for the
SVN should be sought.
 The latter runs from the lateral end of
the meatus towards the retained
ampulla of the superior semicircular
canal, and is a constant and reliable
landmark.

56. VID 4 (IAC
skeletanisation)

57. Opening the posterior
cranial fossa

58. Opening the posterior cranial
fossa
 This is done through a U-shaped dural
flap, based laterally close to the lateral
sinus.
 The upper limb is close to the superior
petrosal sinus and the lower limb close to
the jugular bulb.
 The medial limb is at the level of the porus.

59.  The dura of the internal meatus
should be cut from lateral to medial
at the level of the transverse crest.

60.  Dural incision
obtains wide
exposure of
both the IAC
and CPA.

61.  The IAC dura is
then opened with
upbiting and
angled scissors.
 The IAC and CPA
incisions are then
connected at the
level of porus
acusticus.

62. VID 5 (Dura incised)

63. Identification of the
facial nerve

64. Identification of the facial
nerve
 The facial nerve is displaced from its
normal position by the tumour, but in
the majority of cases it is displaced in
a fairly predictable way.
 It runs along the anterosuperior
quadrant of the meatus as far as the
porus.

65.  In the translabyrinthine approach, the
tumour is usually between the
surgeon and the facial nerve;
however, this is not always the case.

66.  The routine identification of Bill’s bar,
the vertical crest separating the SVN
from the facial nerve, has been
abandoned by many surgeons now
because of availability of reliable facial
nerve monitors.
 But it may be useful to do so in cases
of doubt, and at the institutes where
monitors are not available.

67.  Access to the anterosuperior part of the
meatus may be helped by careful
debulking of the tumour in the lower
half of the meatus.

68.  It is also useful
to try to identify
the facial nerve
on the
brainstem at the
earliest
opportunity
(Figure).

69. Tumour removal

70. Tumour removal
 With tumours confined to the internal
meatus or with little intracranial extension,
dissection can start at the fundus and
proceed medially, keeping to the arachnoid
plane.

71.  Little difficulty should be encountered
although even small tumours may be
surprisingly adherent to the facial nerve
just at and medial to the porus, and sharp
dissection may be needed (Figures).

74.  With larger tumours debulking of the
inside of the tumour is carried out so that
the tumour is converted from a solid ball
to a hollow ball.
 This technique is based on the fact that as
the tumour expands all important
structures such as the facial nerve and
AICA are pushed before the tumour and
are to be found in the arachnoid sheath on
the outside of the tumour capsule.

75.  A number of techniques and instruments can
be used for debulking.
 If the inside tumour is very soft it is
possible to reduce the volume quite rapidly
with suction alone.
 More solid tumours may require the use of
the ultrasonic surgical aspirator (CUSA)
or the cutting bipolar loops.

76. Vid 5 (US debulking)

77.  As the tumour bulk reduces it
becomes progressively easier to
manipulate the tumour capsule.

78.  After tumour removal, haemostasis
must be secured.
 Care must be taken with the use of
the bipolar diathermy in the vicinity of
the facial nerve.

79. CLOSURE

80. Closure
 This is one of the most important steps
in the translabyrinthine operation.
 CSF fistula remains one of the most
common postoperative problems.
 To minimize the risk, careful
obliteration of the middle ear and the
temporal bone defect is essential.

81.  The middle ear, Eustachian tube and
vestibule are obliterated with muscle
and bone wax.
 The supra- and inframeatal gutters are
obliterated with fat and obvious air cell
tracts sealed with bone wax.
 The temporal bone defect is obliterated
with abdominal fat either in strips or in
one large piece

82.  Fat grafts are
harvested from
the anterior
abdominal
graft.
 In woman, fat
can be
harvested from
hip region.

83.  A schematic
axial view
demonstrating
placement of
the FIRST fat
strip into the
craniotomy
defect.

84.  A schematic axial
view
demonstrating
additional fat
strips into the
craniotomy
defect.

85.  The periosteal flap is then sutured
back over the fat and the skin closed
in two layers.
 A firm-pressure dressing is applied
and kept in place for a week.

86. VID-6 (CLOSURE)

87. Middle Fossa
Approach

88.  Schematic coronal view through Temporal lobe and roof of
petrous pyramid.
 Temporal lobe retraction provides excellent view of IAC.

89.  The middle fossa approach is one of the
possible routes of access for hearing
preservation surgery.
 Its advantages and disadvantages are
summarized in Table.

91.  It has the advantage of allowing good
visualization of the lateral extent of the
internal meatus.
 The approach is however somewhat
cramped and access to the posterior fossa
limited.
 Maximum size of tumour that can be
removed is approx. 1–1.5 cm in
intracranial diameter.

92.  There is a small but real risk of
epilepsy following extradural
retraction of the temporal lobe
(Aggarwal et al).

93. The key stages in the middle
fossa approach are:
 1. skin and soft tissue incisions;
 2. middle fossa craniectomy;
 3. extradural approach to upper surface of
temporal bone and to posterior fossa;
 4. skeletonization of internal meatus;
 5. identification of facial and vestibular nerves;
 6. removal of tumour;
 7. closure.

94.  The surgeon is seated at the head end of the
bed during middle fossa surgery.

95. Incision
 A 6–7 cm vertical or gently
backward curving incision
starts at the level of the
zygomatic arch just in front
of the pinna.
 The temporalis muscle is
exposed and an inverted T-
shaped incision is made
though the muscle down to
the skull.

96. Craniectomy
 A 5 x 5 cm
square bone
flap is cut with
about two-
thirds in front
of the
intermeatal line
and one-third
behind it.

97.  The dura
over the
temporal lobe
is exposed.

98.  Eevation of dura from anterior face of petrous pyramid
proceeds from posterior to anterior.
 Eventual target is crest at the ridge of the petrous pyramid
(dashed line) and Porus acousticus (solid circle).

99.  Anteriorly, GSPN is
encountered, if it is
adhered to the dura it
must be liberated
sharply.
 Middle meningeal artery
bleeding can be
controlled with bipolar
cautery and packing
bone wax into its
foramen.

100.  Transparent view of petrous contents as shown from above.

101.  Picture after
the completion
of dural
elevation.
 Note the GSPN
and Arcuate
eminence
overlying the
SSCC.

102. Temporal lobe retractors

103. How to localise the IAC?
 Several methods are available for localising the
IAC in the middle fossa floor.
 One commonly used method is to first identify
the porus acousticus.
 Then drill the rest of the IAC wall from medial
to lateral to expose the full length of the canal.

104.  A deep trough is drilled into the apical petrous bone,
well anterior to anticipated location of canal.

105.  Another method to
locate IAC is by
tracing the GSPN
back to the
geniculate ganglion.
 Then follow the
labyrinthine
segment of nerve to
the fundus.
 This method is
‘House method’.

106.  IAC may be located
by beginning with
‘blue lining’ of SSCC
(arcuate eminence).
 SSCC is fairly
constant angular
relation to the
IAC(Between 45 and
60 degrees).
 This is ‘FISCH
method’.

107.  Once the dura
of IAC has been
opened, an
intracanalicular
tumour can be
visualised.
 Often the FN
lies on the
superior surface
of the tumour.

108. CLOSURE
 The cavity
created during
IAC exposure is
filled with a free
tissue graft (eg.
temporalis
muscle or fat
graft).

109.  The bone flap
is then
replaced and
wired in
position.

110. Vid 7 (Middle fossa approach)

111. Retrosigmoid
Approach

112. Retrosigmoid approach
 This approach has evolved from the
classic suboccipital operation that
was favoured by neurosurgeons for the
removal of all tumours but particularly
for large ones.
 The advantages and disadvantages of
the approach are summarized in Table.

114.  Postoperative headache is more
common with this approach than the
translabyrinthine operation.

115. Incision
 A vertical or slightly
curving incision is
made about 3 cm
behind the mastoid
process, from
above the level of
the transverse
sinus to the level of
the tip of the
mastoid.

116. Craniotomy and exposure of
the tumour
 A 5 x 5 cm craniotomy is
made using the drill, taking
the mastoid emissary vein
as the starting point and
retaining the bone dust for
closure.
 The anterior and superior
limits of bone removal are the
sigmoid and the transverse
sinuses, respectively.

117.  Dural incision is
made in such a
way to
facilitate suture
closure of the
dura.

118.  Before posterior retraction of the
cerebellum, it is necessary to release
the CSF pressure by opening the
cisterna magna.
 Premature retraction of the
cerebellum, before decompressing
the cistern, risks inducing massive
cerebellar swelling.

119.  Opening of the cisterna magna with a suction lancet.

120.  Axial schematic view of
Retrosigmoid approach
to the CPA and IAC.
 Note the cerebellar
retraction.

121. Closure
 Dural closure
should be very
thorough.
 Bone wax is
applied to
transected
mastoid air cells.
 Craniotomy
defect is
repaired.

122. COMPLICATIONS

123. COMPLICATIONS
(Shambaugh)
 lntraoperative Complications :
1. Cranial Nerve Injury
2. Bleeding
3. Brain Edema
4. Venous Air Embolism
5. Cardiac Arrhythmias
6. Brain Herniation

124.  Postoperative Complications:
1. Hemorrhage
2. Infarction
3. Cerebrospinal Fluid Leak
4. Meningitis
5. Tension Pneumocephalus

125. Stereotactic
Radiation Therapy

126.  ln 1951, the Swedish neurosurgeon
Leksell developed the first open
stereotactic instrument by focusing
multiple radiation beams on a single
target.
 Currently, stereotactic radiation is the
principal alternative active treatment
for vestibular schwannomas.

127.  The goals of stereotactic radiation therapy
are the :
1) Long-term prevention of tumor growth,
2) Maintenance of neurologic function, and
3) Prevention of new neurologic deficits.

128.  The word stereotaxis is derived from two
Greek words:
 Stereos - “three-dimensional,”
 Taxis - “orderly arrangement.”
 A high dose of radiation can be delivered
to a defined region, usually within a well-
immobilized system that conforms closely
to the 3D shape of the target volume.

129.  Stereotactic irradiation can be
performed by using any one of the
high-energy forms of radiation,
whether
1) Radiographs (x-rays),
2) Gamma rays, or
3) Charged-particle irradiation.

130.  It involves fixing a
Rigid Stereotactic
Frame to the patient’s
head, which then acts
as a reference, defining
the volume which it
encloses in a set of X,
Y and Z coordinates.

131.  By combining this setup with
radiological images (generally MRI),
it can be used to target pathological
structures including skull base
tumours.

133. How is Radiosurgery different
from Radiotherapy?
 Radiosurgery differs fundamentally from
radiotherapy in that it is delivered as a
single high dose of radiation, rather
than as a fractionated course of
treatment.

134. Advantages of
Stereotactic Radiation
 Potential advantages of stereotactic
radiation over Microsurgical resection
include :
1) Decreased hospitalization time,
2) A quicker return to work, and,
3) A reduced cost of treatment.
4) Can be considered for elderly or medically
unfit patients.

135. Stereotactic Radiation
Disadvantages
 Three concerns are frequently raised about
radiosurgery, particularly in comparison
with surgery.
1. The need for long-term follow-up.
2. The risk of radiation causing malignant
transformation.
3. The possibility that radiosurgery causes
peritumoural scarring that makes
subsequent surgery more difficult.

136.  In summary, although acceptable
outcomes have been reported with
stereotactic radiation therapy for the
treatment of vestibular schwannomas,
long-term outcomes at current levels of
radiation have not been well
documented.

137. THANK YOU
-drdhiru456@gmail.com

138. References :
1) Scott-Brown’s Otorhinolaryngology:
Head and Neck Surgery : 7th edition.
2) Shambaugh : 6th edition.
3) Neurotology and skull base surgery:
R. K. Jackler.
4) Cumming’s otorhinolaryngology : 5th
edition.