Operative steps described to excise large acoustic neurofibromas using Retromastoid approach in lateral position.

1. DR.U.S.
LARGE ACOUSTIC NEURINOMA
SURGICAL STEPS
RETROMASTOID APPROACH

2. DR.U.S.
Large Acoustic Neurinoma – Successfully excised
PRE-OP MRI
POST OP CT – NO TUMOR
This presentation is based upon > 60 cases of Large/ Giant Acoustic
Neurofibromas excised over last 20 years
through Retromastoid approach

3. DR.U.S.
PRE-OPERATIVE MRI SCAN WITH CONTRAST SHOWING A LARGE
RECURRENT ACOUSTIC NEURINOMA OF SIZE 50mm x 38 mm x 36 mm

4. DR.U.S.
Post-operative CT brain showing radical excision of the RECURRENT ANF

5. DR.U.S.
Fresh ANF vs Recurrent ANF – Surgical strategy
•Steps outlined below to deal with a FRESH CASE of acoustic neurofibroma as well as a RECURRENT
ANF.
•Initially most of the steps like OT arrangements, positioning, skin incision, extent of craniotomy,
exposure of the transverse sinus and sigmoid sinus are same. Even in recurrent ANF, the dural opening
or opening of the fascia that was used to close the defect is the same.
•The identification of the Arachnoid plane DIFFERS BETWEEN THESE TWO TYPES.
•But intratumoral decompression is the same technique.
•Dealing of the cranial nerves would be different since it would be influenced by the pre-operative
status. But still the BASIC DIKTAT OF PRESERVERATION OF ALL THE CRANIAL NERVES
SHOULD BE STRICTLY ADHERED.
•Complications that can be encountered during each step and its management is almost the same.

6. DR.U.S.
OT ARRANGEMENT

7. DR.U.S.
OT arrangement – This is just an illustration. Depending upon the
surgeon’s preference it can be arranged.
Position for Right side posterior fossa approachPosition for Left side posterior fossa approach
Normal Operating
Microscope can be
Positioned
Normal Operating
Microscope can be
Positioned

8. DR.U.S.
OT ARRANGEMENT FOR ANF RETROMASTOID APPROACH
This is my preference with the Anaesthetist at head end itself with Anaesthesia Monitors
directly opposite to the surgeon.
I have regular operating microscope which I bring from the opposite side.
This is just an illustration. Depending upon the surgeon’s preference it can be arranged.
Position for Right side posterior fossa approach
IONM
Monitoring
Normal Operating
Microscope can be
Positioned
Anaesthesia
Monitors
SIGNIFICANT ADVANTAGE:
I have observed in this type of
OT arrangement is, I can have
the assistance of the 2nd
Assistant from Opposite side.
It is extremely useful in
• Irrigating while applying
bipolar
• Identifying bleeding points
• Dissecting on my side, since
he can clearly see from
opposite side.
2nd
Assistant
DISADVANTAGE is getting the
instruments from the Staff Nurse
who needs to be efficient while
Assisting.
Can change to opposite side the entire arrangement in LEFT SIDE posterior fossa approach

9. DR.U.S.
PATIENT POSITIONING
It is surgeon’s preference
[In this presentation only LATERAL position will be described, which I am used to.
Readers are referred to the standard operative atlas
describing the nuances of SITTING POSITION]

10. DR.U.S.
FIX THE SKULL FIXATOR BEFORE TURNING THE PATIENT TO LATERAL POSITION
• ALWAYS FIX THE SKULL USING SKULL
FIXATOR FOR ACOUSTIC NEURINOMA.
• SINGLE PIN TO BE FIXED ON THE SIDE OF THE
TUMOR and DOUBLE PIN ON THE OPPOSITE
SIDE.
• If VP shunt has been done, ensure that the pins don’t
penetrate into the burr hole site or into the tube along
its course.
• DON’T USE DOUGHNUT.
• ENSURE THAT ET TUBE IS WELL FIXED , since it
can slip during surgery. [Documented in literature].
It occurs because plasters around ET tube becomes loose
after betadine scrub soaks the plasters. It can occur also due
to drag of the ET tube in Prone position.
This picture is of another case
Shown for illustration of how to securely fix
a 3 point skull fixator

11. DR.U.S.
TURNING THE PATIENT TO LATERAL POSITION AFTER FIXING THE SKULL
FIXATOR
MOVEMENT OF PATIENT FROM SUPINE
INTO LATERAL OBLIQUE POSITION.
Fix the skull fixator in supine position.
Take care that skull fixator doesn’t compress the
eyes or nose or fore head even during flexion of
the neck.
TURN THE PATIENT LIKE LOG OF WOOD
To prevent cervical spine injury
IN THIS CASE ONLY AFTER PATIENT IS POSITIONED
LATERALLY, IONM IS FIXED OVER THE FACE AND
OVER THE SCALP

12. DR.U.S.
PATIENT POSITIONING STEPS
3 POINT SKULL FIXATOR IS SHOWN HERE –
with Sugita’s skull fixator frame it is different
LATERAL OBLIQUE POSITION DOUBLE PIN ON
THE OPPOSITE SIDE
SINGLE PIN
ON THE SIDE OF
THE TUMOR

13. DR.U.S.
Patient Positioning [Contd]
• Bring the patient to the edge of the table and then fix the head
• Keep one litre plastic saline bottle or foam or small soft towel below the axilla of
the hanging arm.
• Cover the hanging arm with a thick roller gauze and attach a small straight arm rest
covered with a roller gauze to the forearm and rest it in a “L” shaped manner.
• The arm on the side of the tumor is placed on the arm rest to lessen the respiratory
load of its weight.
• Place a soft small towel under the axilla of the upper arm and chest
• Keep a pillow between the legs.
• After fixing the head, strap the patient securely with plasters
• Elevate the head end 30 degrees

14. DR.U.S.
POSITIONING IN THE LATERAL POSITION
POSITIONING OF THE HEAD
Head should always be above the heart level.
FLEX THE NECK ANTERIORLY TOWARDS THE
CHEST.
• Mild to moderate flexion only
• ET tube should not be compressed
• OPPOSITE JUGULAR VEIN SHOULD NOT BE
COMPRESSED
• Minimum 3 finger breadth space between chin and sternum
should be present.
ROTATE THE HEAD MILDLY TOWARDS THE FLOOR
so that mastoid process-asterion is at superior level.
SLIGHTLY TILT THE NECK TOWARDS THE FLOOR.
Keep the neck stretched
As far as possible keep the head slightly parallel to the floor.
FIXATION USING SUGITA SKULL FIXATOR
IS SHOWN IN THE ABOVE FIGURE
Take care of the AXILLA ON THE DEPENDENT ARM

15. DR.U.S.
POSITIONING IN THE LATERAL POSITION – SEEN FROM DIFFERENT
ANGLES WHILE FIXING WITH SUGITAL SKULL FIXATOR

16. DR.U.S.
SUGITA FOUR PIN SKULL FIXATOR : FIXING THE PINS
•The FIRST PIN over the frontal bone on the side of the
lesion about 2cm away from the MIDLINE and 7cm above
the eyebrow.
•The FOURTH PIN over the occipital bone 7cm away from
the midline on the side OPPOSITE to the lesion and
positioned slightly above the line joining the EOP to
mastoid base.
•The other TWO PINS placed in the slot adjacent to the first
and fourth pin.

17. DR.U.S.
PATIENT POSITION AS SEEN FROM THE OPERATING SURGEON’S SIDE
• Patient’s head is elevated 30 degrees above the heart
level. Done by inclining the upper portion of the
operating table and raising the head.
• Bring the patient’s head at least 20 – 25 cm away from
the top edge of the OT table.
• Patient’s shoulder is place close to the edge of the
operating table on the side where the surgeon sits or
stands so that the table edge gets in the surgeon’s way
as little as possible.
• The head is tilted 15 degrees to the opposite side of the
lesion
• Vertex is tilted 10 degrees down.
• The side of the head is positioned parallel to the floor
so that the asterion is the uppermost part seen.

18. DR.U.S.
Patient SKULL POSITION AND SHOULDER
POSITION as seen from the Operating Surgeon’s Side
Patient position OF THE LEGS as
seen from the Operating
Surgeon’s Side
CLOSE UP VIEW

19. DR.U.S.
PATIENT POSITION AS SEEN FROM THE PATIENTS’ FACE SIDE
POINTS TO BE CAREFULLY NOTED
• PROTECT THE EYES – Apply eye ointment
and eye bandage. The skull fixator should NOT
COMPRESS the eyes or forehead.
• DEPENDENT ARM – AXILLA TO BE PROTECTED
Give an arm rest and support it.
Keep generous padding under the axilla.
The arm should not be compressed.
Ensure that there is no compression over the nerves
or vessels.
• UPPER ARM: Support it with an arm rest
Don’t allow it to rest over the chest.
• Cover both the arms with soft roll so that it DOESN’T COME
INTO CONTACT WITH ANY METAL PARTS OF THE OT TABLE

20. DR.U.S.
Positioning of the ARMS & LEGS
• Bring the patient to the edge of the table and then fix the head
• Keep one litre plastic saline bottle or foam or small soft towel
below the axilla of the hanging arm.
• Cover the hanging arm with a thick roller gauze and attach a
small straight arm rest covered with a roller gauze to the forearm
and rest it in a “L” shaped manner.
• The arm on the side of the tumor is placed on the arm rest to
lessen the respiratory load of its weight.
• Place a soft small towel under the axilla of the upper arm and
chest.
• Keep a pillow between the legs.
• Protect the peroneal nerves.
• After fixing the head, strap the patient securely with plasters.
• Elevate the head end 30 degrees.

21. DR.U.S.
INTRAOPERATING MONITORING LEADS
• Fix the leads of the facial nerve monitoring
electrodes.
• If facilities are available for exhaustive
monitoring like BAER, SSEP, MEPs fix the
leads.
• Take care of the EYES
• Coordinate with the INOM in charge

22. DR.U.S.
LP DRAINAGE OF CSF
•LP drainage can be inserted before positioning if the surgeon prefers.
•Not to drain the CSF during the time of insertion.
•At the time of completion of the craniectomy and BEFORE OPENING
THE DURA, preferably at the beginning of the craniotomy/craniectomy,
to ask the Anaesthetist to drain around 100-150ml.
•In a few cases it may not be able to tap the CSF especially where a prior
VP shunt is done for hydrocephalus. In that case proceed directly with the
surgery.

23. DR.U.S.
Why such an elaborate description of the positioning is given?
•Elaborate description of the positioning of the patient in lateral position was given above for the reason,
if severe brain bulge occurs during opening of the dura, it is due to faulty positioning in the
majority of cases.
•It would very difficult to change the position once you fix the skull fixator.
•Then you have to ABANDON THE SURGERY. [This occurred in one of my earlier cases, where I
was forced to stop the surgery when I attempted different positioning from what I used to do.
Unfortunately for me in that case, I had a new anaesthetist who allowed the patient to strain against the
ET tube leading to further aggravation of the brain bulge. Inserted EVD and after a week successfully
reoperated in my familiar position of lateral position. Follow up of > 12 years, patient is doing well.]
•To prevent such a catastrophic event, I have explained in detail about the nuances of positioning in
lateral position.

24. DR.U.S.
SKIN INCISION

25. DR.U.S.
SKIN INCISION IN RETROMASTOID
APPROACH
[This case was resurgery]
• Mark the Mastoid Tip.
• Draw the Mastoid process.
• Draw a line connecting the EOP to the Mastoid
Base indicating the TRANSVERSE SINUS.
• SUPERIOR POINT: Mark a point 3-4 cm above
the pinna [Upper limit of the incision].
• Mark the ASTERION which is roughly 4-5cm
behind the midpoint of the junction of the ear to the
scalp.
• Draw the midline.
• INFERIOR POINT: Mark a point 2- 3cm away
from the midline at the level of C2-C3.
• A “S” shaped incision about 8-10cm is made
along the medial border of the mastoid process [two
finger breadth medial to the mastoid tip] connecting
the Superior point to the Inferior point.
C2spinous
Process
Inferior
Point
EOP Mastoid
Tip & Process
4-5 cm
Asterion
Superior
Point
Midline

26. DR.U.S.
FEW SURGEONS PREFER “C” SHAPED INCISION
Advantage: Better bone exposure medially and craniotomy site would not be directly underneath the skin
incision.
Better closure of the fascia. Risk of CSF leak is decreased

27. DR.U.S.
STEPS DESCRIBED IS WITH RESPECT TO A FRESH ACOUSTIC
NEUROFIBROMA CASE BEING OPERATED

28. DR.U.S.
MUSCLE SEPARATION Undermine the tissue after incising the skin for 2-3 cms on each
side of the skin incision.
• Periosteum and more superficial muscles below superior nuchal
line [Splenius capitis, Trapezius and Sternocleidomastoid] are
incised with monopolar cautery in the same direction of the skin
incision BUT 1cm AWAY FROM THE LINE OF SKIN INCISION.
• INFERIOR EXTENT: Inferiorly dissect underneath the muscle by
introducing the mosquito forces and then lift the muscle. Using
monopolar cautery cut it layer by layer.
• CAUTION: PALPATE WHILE CUTTING THE DEEPER LAYER OF
MUSCLES TO DETECT THE ABNORMAL COURSE OF VERTEBRAL
ARTERY.
• Superficially identify the occipital artery and coagulate and cut
it.
• Similarly the occipital nerve.

29. DR.U.S.

30. DR.U.S.
VERTEBRAL ARTERY VARIATION AND ITS IMPLICATIONS
ANAMALOUS COURSE AT C1-C2
THREE types of vertebral artery variation at the
craniovertebral junction have been described.
• The most common variant is a persistent First
intersegmental artery [FIA],which arises when part
of the embryonic FIA persists causing the
VERTEBRAL ARTERY TO TAKE AN “ANOMALOUS”
COURSE AND ENTER THE SPINAL CANAL BETWEEN
C1 AND C2 with absence of the normal vertebral
artery branch.
• A recent magnetic resonance angiography (MRA)-based
study has shown this variant to be present in 3.2% of
patients
PMC full
text:
Evid Based Spine Care J. 2014 Oct; 5(2): 121–
125. doi: 10.1055/s-0034-1386751
BEWARE OF ANAMALOUS COURSE AT C1-C2 – TRAVERSING MEDIALLY
ANAMALOUS COURSE AT C1-C2 – TRAVERSING
MEDIALLY – I HAVE ENCOUNTERED TWO SUCH
CASES

31. DR.U.S.
BONE EXPOSURE
• INFERIOR LIMIT: Expose the posterior lip of the FORAMEN
MAGNUM.
• Note: Deeper muscles [Obliques and rectus capitis] need not be
incised unless the tumor is extending below the level of foramen
magnum.
• NO need to expose the arch of atlas or vertebral artery.
• LATERAL EXTENT: Dissect across till mastoid emissary vein is
clearly seen. The mastoid tip to be completely exposed. If needed
cut across the muscles transversely in the region of the foramen
magnum and retract the muscles with fish hooks.
• MEDIAL EXTENT: For 2 cm away from the line of skin incision.
• Take a small bit of muscle [If transverse sinus inadvertently gets
injured then it can be placed to obtain hemostasis].
• Dissect the periosteum completely from the bone on all the sides.
• IDENTIFY THE LAMBDOID SUTURE, THE ASTERION, THE
MASTOID TIP AND POSTERIOR LIP OF THE FORAMEN
MAGNUM/

32. DR.U.S.
WHERE TO PLACE THE BURR HOLE SAFELY IN
RETROMASTOID CRANIECTOMY

33. DR.U.S.
WHERE TO PLACE THE BURR HOLE SAFELY IN RETROMASTOID
CRANIECTOMY
HORIZONTAL LINE:
• Superior aspect of the Zygomatic
arch.
VERTICAL LINE:
• From the Mastoid Notch
• So safely the burr hole can be
placed 10MM [1CM] BELOW
THE ZYGOMATIC LINE AND
MEDIAL TO THE MASTOID
LINE
ZYGOMATIC
LINE
MASTOID LINE

34. DR.U.S.
EMISSARY FORAMEN AND BURR HOLE PLACEMENT IN
RETROMASTOID APPROACH
When EMISSARY FORAMEN/S are clearly seen
The burr hole can be SAFELY PLACED 10MM
[1CM] BELOW THE LARGEST EMISSARY
FORAMEN SEEN CLOSE TO MASTOID
PROCESS AND MEDIAL TO THE MASTOID
EMISSARY
FORAMEN
MASTOID
Sigmoid Sinus
Picture as seen during Retromastoid Approach in
Lateral Position
Foramen
Magnum
Strategic
BURR HOLE

35. DR.U.S.
BURR HOLE PLACEMENT IN RETROMASTOID CRANIECTOMY
Strategic
BURR HOLE
IN ABSENCE OF VISIBLE EMISSARY FORAMEN: SAFELY THE BURR HOLE CAN BE PLACED
• 1 cm BELOW THE ZYGOMATIC LINE [Need to palpate the Zygomatic Arch through drapes – Practically
it is difficult] [So use various other landmarks like Asterion, Nuchal Line, Semispinalis Capitis muscle insertion]
• 1 cm MEDIAL TO THE MASTOID LINE
MASTOID LINE
PICTURE AS SEEN DURING RETROMASTOID
APPROACH IN LATERAL POSITION
Strategic
BURR HOLE
DRAPES

36. DR.U.S.
RETROMASTOID CRANIECTOMY/ CRANIOTOMY
*BEFORE STARTING CRANIOTOMY, IF LP DRAIN IS INSERTED,
ask the Anesthetist to let out around 100ml of CSF to relax the
cerebellum.
After placing the burr hole depending upon the Surgeon’s preference
either Craniotomy or Craniectomy can be performed.
CRANIOTOMY: It is advisable to place a second burr hole 3 cm away
from the first burr hole and a 3rd burr hole. Complete the craniotomy
using Craniotomy.
CRANIECTOMY: Can be completed using Kerrison’s upcutting & or
bone nibblers.

37. DR.U.S.
EXTENT OF THE CRANIECTOMY
• LATERAL EXTENT: Drill over the mastoid process after completing the craniectomy or craniotomy. Should cross the
mastoid foramina. Keep irrigating the field profusely to prevent air embolism. Expose the sigmoid sinus along its entire
vertical length.
• Followed by nibbling the bone from the superolateral burr hole site upwards using 3mm upcutting to expose the
transverse sinus.
• Then nibble the bone superolaterally to expose the junction of the transverse sinus with sigmoid sinus.
• Remove the posterior lip of the foramen magnum as far lateral as possible and if needed laterally use the drill.
• MEDIAL EXTENT: 4 cm from the lateral extent of the craniectomy.
• Thus the craniectomy should expose:
• SUPERIORLY: TRANSVERSE SINUS INFERIORLY: FORAMEN MAGNUM LIP
• LATERALLY: SIGMOID SINUS MEDIALLY: 4cm from the lateral extent.

38. DR.U.S.
•
Bone removal over the transverse sinus to expose the edges of the transverse sinus
Drilling over the mastoid to expose the Sigmoid Sinus.
Wax the Mastoid

39. DR.U.S.
MASTOID PROCESS – VARIATIONS – Its significance
CT showing
HYPERPNEUMATISATION HYPOPNEUMATISATION During craniectomy, LIBERAL
MASTOIDECTOMY TO BE
PERFORMED to clearly visualize
the sigmoid sinus course.
If mastoid air cells are opened which
can occur in hyperpneumatised
mastoid, then WAXING SHOULD
BE EXTENSIVE & VIGOROUS to
prevent postoperative CSF
otorrhoea and /or rhinorrhoea

40. DR.U.S.
Craniectomy & Exposure Of Transverse Sinus,
Drilling Of Mastoid To Expose The Sigmoid Sinus
Exposure of the Transverse sinus and the
Superolateral corner of it
NOTE: TRANSVERSE SINUS WOULD
BE SEEN AS BLUISH IN COLOUR
Transversesinus
DRILLING OVER THE MASTOID PROCESS TO EXPOSE THE
SIGMOID SINUS.
Initially use a 3mm or 5mm CUTTING BURR.
Drill It Like A Saucer. Never like a Cup.
When the bone thickness is < 2-3 mm, use either DIAMOND BURR
OR better use upcutting to remove the bone over the sinuses
LATERAL
INFERIOR
MEDIAL
SUPERIOR

41. DR.U.S.
Sigmoid Sinus Exposed In The Lateral Extent Of The Craniectomy
Transversesinus
NOTE: TRANSVERSE SINUS & SIGMOID SINUS WOULD BE SEEN AS BLUISH TO
DARK BLUISH IN COLOUR.
Clearly distinguishable from the dura & the underlying cerebellum
Sigmoid sinus

42. DR.U.S.
INTRAOPERATIVE MANAGEMENT OF AIR EMBOLISM AND
INJURIES TO TRANSVERSE SINUS AND SIGMOID SINUS

43. DR.U.S.
COMPLICATIONS THAT CAN INADVERTENTLY OCCUR
AIR EMBOLISM
• Air embolism: To be prevented by generously irrigating while stripping
the muscles from the bone.
• If emissary vein is opened, to generously irrigate and control the
bleeding either by waxing or coagulating if possible + waxing.
• IF ANESTHETIST INFORMS ABOUT AIR EMBOLISM, LOWER THE HEAD
END AND FLATTENT THE OT TABLE AND FOLLOW ANESTHETIST
INSTRUCTIONS. KEEP IRRIGATING THE OPERATIVE FIELD.

44. DR.U.S.
• DON’T: ATTEMPT COAGULATING THE INJURED TRANSVERSE/ SIGMOID SINUS. IT IS GOING TO INCREASE
THE RENT IN THE SINUSES AND CAUSE PROFUSE BLEEDING.
DO’s:
• Elevate the HEAD END BY 30 DEGREES.
• Pack the injured site with either cotton patty or gauze piece.
• ALWAYS TAKE A SMALL MUSCLE DURING DISSECTION OF THE MUSCLES AND PREPARE A SANDWICH OF
SURGICEL-MUSCLE PATCH [Crush the muscle and flatten it]- SURGICEL. Keep it ready.
• Along with it keep multiple pieces of sandwich of surgical-gelfoam-surgical.
• Gently remove the packed patty or gauze piece and keep the sandwich containing the muscle – surgical over the injured sinus.
Keep a gauze or cotton patty over it. Apply gentle pressure for 5-10 minutes. Observe the region carefully. In majority of the cases
bleeding would stop. Don’t remove the cotton patty. In the end of surgery it can be removed after giving gentle saline wash.
• If PROFUSE BLEEDING CONTINUES, then you can try applying the suture using 4’0 vicryl. Take the bite from below the edge
of the transverse sinus or cut edge of the sinus and take the thread over the surgical sandwich to the nearby adjacent pericranium
and tie the knot. Apply pressure.
COMPLICATIONS THAT CAN INADVERTENTLY OCCUR
INJURY TO TRANSVERSE SINUS/ SIGMOID SINUS

45. DR.U.S.
DURAL OPENING – EITHER “C” OR “X” Shape
There is no hard and fast rule – it depends on the surgeon’s preference.
[Both types I have used]
NOTE: The cut edge of the dural flap should be close to the edges of the sinuses.
BUT DISTALLY CURVE THE CUT EDGE PARALLEL TO THE SINUS IF “X’ shaped incision is
made to open the dura. To prevent the extension of the dural tear into the transverse sinus.
‘C’ shaped opening of the Dura.
Always there should be a dural flap over the cerebellum

46. DR.U.S.
CSF DRAINAGE FROM THE CISTERNA MAGNA
•Depending upon the preference of the surgeon, it can be opened either “X” or “C” shaped.
LET OUT THE CSF FROM CISTERNA MAGNA
•Before opening the dura, in the inferior end close to the cisterna magna, open the dura. Open the
arachnoid and patiently let out the CSF. Can introduce a very small cottonoid patty in the opening
and gently keep removing it 2-3 times, this manoeuvre would drain CSF.
•Time spent on letting out CSF is worth it. Cerebellum would become lax and avoid majority of
post operative complications.
•In case if the cisterna magna could not be reached, due to limited craniectomy, it is suggested to
extend horizontally the inferior aspect of the craniectomy medially for 10-15 mm. Then attempt
opening the dura and cisterna magna. Invariably in most of the case it would be possible.
•In patient’s who had prior insertion of VP shunt, surgeon may not be able to let out CSF.

47. DR.U.S.
EXTENT OF DURAL OPENING
•Depending upon the preference of the surgeon, it can be opened either “X” or “C” shaped.
Here I describe, about “X” shaped opening which I commonly use.
•After letting out the CSF, use a 4’0 vicryl and lift the dura. Use two stitches to elevate the dura. In
between the stitches, make a nick with 15 blade knife. Then introduce a small cottonoid patty if
cerebellum is very close to the dura. If surgeon feels there is enough space and safely can open
the dura using dural scissors, then he can open it in a “X” shaped manner.
•The upper triangular flap should be lifted towards the transverse sinus and can be sutured to the
nearby pericranium. Similarly the lateral flap towards the sagittal sinus.
•Medial flap can be used to cover the cerebellum.
•Inferior dural flap towards the foramen magnum.
•DISTALLY CURVE THE CUT EDGE PARALLEL TO THE SINUS IF “X’ shaped incision
is made to open the dura. To prevent the extension of the dural tear into the transverse sinus.

48. DR.U.S.
POSITIONING OF THE LEYLA RETRACTOR SYSTEM
There are varieties of the Leyla retractor system/ Brain retractor system.
Commonly used Leyla retractor system is TABLE MOUNTED.
• There is skull mounted system but it occupies the space within the Retromastoid craniectomy
region. It can be mounted only inferiorly since superiorly there is transverse sinus and laterally
sigmoid sinus.
• In Sugita system, it could be mounted on the cranial frame.
HERE I DESCRIBE THE TABLE MOUNTED SYSTEM:
• The basic retractor system of the table clamp and the curved rod is attached to the OT table.
Again it is preferable to attach to the OT table rod opposite to the surgeon.
• The rod that holds the flexible arm is directed upward towards the head end.
• The flexible arm is attached to the clamp attached to the curved rod.
• It is bent in such a way that the brain spatula can be easily positioned from the medial aspect of
the craniectomy.
• The brain spatula elevates the lateral margin of the cerebellum.
Patient in LATERAL position
Patient in SITTING position

49. DR.U.S.
VISUALIZATION OF THE TUMOR
[In majority of cases there may not be any requirement of the cerebellar retractor. Without using the Leyla
retractor, I have intermittently retracted the cerebellum manually to get a better view of the tumor]
Surgeons who have facilities for RETRACTOR LESS SURGERY CAN ADOPT IT.
•Attach the Leyla retractor system.
•Check outside the functioning of the Leyla retractor system.
•Attach 15 or 20mm malleable brain spatula to the Leyla arm. Gently retract the
cerebellar lateral end medially over a cottonoid patty or glove bit or over the medially
placed dural flap.
•Initially retract the cerebellum gently medially in the superolateral aspect and try to
visualize the tumor.
•If tumor could not be visualized, the retract the cerebellum in the inferolateral area
directed medially and try visualizing the tumor.
•Once the tumor is seen adjust the brain spatula so that mid portion of the tumor is
clearly seen.

50. DR.U.S.
BRIEF NORMALANATOMY OF CPANGLE AS VISUALIZED
AFTER RETRACTING THE CEREBELLUM
Lower cranial nerves as seen under operating
microscope in the inferior border of the tumorPicture taken from the internet – google images

51. DR.U.S.
RETRACTING THE CEREBELLUM
Picture taken from the internet – google images

52. DR.U.S.
TUMOR EXCISION Identify the tumor: SEEN AS DIRTY GREYISH RED IN COLOUR in majority of
cases.
ARACHNOID DISSECTION:
• Over the tumor arachnoid layer is seen as a white glistening covering.
• Choose a spot over the tumor where underneath the arachnoid there are no
vessels.
• Lift the arachnoid with Micro-Toothed bayonet forceps in the center of the
tumor and make a small nick with 15 blade knife.
• BE CAREFUL NOT TO INJURE THE UNDERLYING VESSELS IF ANY.
• DON’T INJURE THE TUMOR CAPSULE.
• Peel away the arachnoid covering from the tumor capsule either using a blunt
Micro-Dissector or tip of the Micro-sucker or using a small cottonoid.
• It should be peeled off in all the directions as much as possible but the
BORDER OF THE ARACHNOID covering should be clearly seen.
• Usually the arachnoid border after dissecting and pushing it is seen as a rolled
over thickened white glistening fibre.
Tumor
Picture taken from the internet – google images

53. DR.U.S.
MICROINSTRUMENTS USED DURING SURGERY –
Useful in Arachnoid Dissection
Micro Bayonet Plain & Toothed forceps Straight Micro Scissors
Micro Dissector
Blunt tipped for
teasing the arachnoid
off the tumor capsule

54. DR.U.S.
INTERNAL DECOMPRESSION OF THE ANF
Tumor in a recurrent case of ANF Internal Decompression of the tumor using CUSA

55. DR.U.S.
INTERNAL DEBULKING OF THE TUMOR EITHER USING CUSA OR
SCISSORS-SUCTION- SAMII KNIFE – TUMOR FORCEPS
•Expose at least 15- 20mm of the capsule of the tumor after arachnoid dissection.
•Open the capsule generously for at least 10-15mm using a 11 blade knife in a “X”
shaped manner.
•Coagulate the edges of the capsule.
•FIRST DO INTERNAL DECOMPRESSION WITHIN THE CAPSULE.
•In centres which have CUSA, use it.
•In NON-CUSA CENTRES: Use sucker to decompress the tumor.
•SOFT TUMOR: If tumor is soft try the double suction method. Holding a large 4mm
suction in the right hand and 3mm suction in the left hand try to decompress it. [I use
Sundt Flow Regulated Suction to clear the blood from the field. Regular 4mm suction to
suck the tumor] [Pic]
•Decompress the tumor within the tumor capsule 360 degrees.

56. DR.U.S.
MICRO INSTRUMENTS USED DURING INTERNAL DECOMPRESSION
OF ANF
MICROTUMOR
FORCEPS
NON-STICK 1MM/2MM
BIPOLAR FORCEPS
SUNDT FLOW
REGULATED
SUCTION SET
4mm tip Micro-
suction

57. DR.U.S.
Yasargil – 7.5 inches length microscissors
Curved Microscissors Straight MicroscissorsSAMII KNIFE

58. DR.U.S.
INTERNAL DECOMPRESSION OF THE TUMOR
•FIRM TUMOR: Use Samii Knife [Pic] to scoop the tumor from all sides under direct vision while sucking out the tumor
bits with either large bore Micro-sucker [I prefer Sundt Flow Regulated Suction].
•VERY FIRM: If the tumor is very firm, fibrous and hard, then coagulate the tumor using bipolar by inserting it distal to
the visualised tumor. The bipolar tip edges should be clearly seen. It is similar to holding the tumor with bipolar forceps
and coagulating it. Then cut using Micro-Scissors. Always visualize the edges of the Micro-Scissors. In avascular or
minimally vascular tumor can hold the tumor with 3/5mm tumor holding forceps [PIC] and cut with Micro-Scissors.
•Simultaneously give a thorough saline wash.
•THE ARACHNOID PLANE TO BE CLEARLY SEEN. PEEL THE ARACHNOID AWAY FROM THE TUMOR
CAPSULE AS THE TUMOR IS DECOMPRESSED.
•Simultaneously incise the visualized edges of the capsule with microscissors and enlarge the opening. Precisely coagulate
the bleeding points. NO INDISCRMINATE COAGULATION.
•Can also use in soft to firm tumor cases, cottonoid inside the tumor to scrape the tumor out.

59. DR.U.S.
COAGULATION AND CONTROL OF HEMOSTASIS
•KEEP THE BIPOLAR COAGULATION STRENGTH TO MINIMUM THAT IS NECESSARY TO ACHIEVE
COAGULATION.
•No need to achieve haemostasis every time after you remove bit of the tumor if there is only minimal ooze.
•There would be bleeding/ oozing till the tumor is completely removed.
•Keep removing the tumor.
•Always keep the tumor bleeding under control.
•NEVER LOSE THE ARACHNOID PLANE. NEVER ALLOW THE BLEEDING TO OOZE OUT OF THE TUMOR
CAVITY.
•If there is profuse bleeding then give saline wash and identify precisely the bleeding point and coagulate it using minimal
current strength.
•In a situation, continuous diffuse bleeding interferes with internal decompression, place a cottonoid and gently compress
that area. Wait for few minutes. Then by giving saline wash, gently roll over the cottonoid and identify the bleeding. If it is
tumor bleed, it would have stopped. If it is from the arterial branch supplying the tumor, it would be clearly visualized,
coagulate it.

60. DR.U.S.
Instruments used
HEBBAR
SURGICALS
SUNDT FLOW
REGULATED
SUCTION SET
I HAVE NEVER USED LASER
JEFFERSON DURAL
FORCEPS
BAYONET SHAPED
MICRO NON TOOTHED
AND TOOTHED
FORCEPS
MICROTUMOR
FORCEPS
BIPOLAR
FORCEPS
RHOTON
MICRODISSECTOR
SET

61. DR.U.S.
RHOTON MICROINSTRUMENTS THAT WERE COMMONLY USED IN TUMOR
DISSECTION
RHOTON MICRODISSECTOR
COMPLETE SET OF 20 INSTRUMENTS
COMMONLY USED RHOTON
MICROINSTRUMENTS

62. DR.U.S.
IDENTIFICATION OF ADEQUATE INTERNAL DECOMPRESSION
•If the internal decompression is adequate, when you hold the CAPSULE AND
SHAKE IT, THE CAPSULE SHOULD EASILY MOVE or
•Capsule should be seen as TRANSPARENT COVERING when the tumor is
completely removed.

63. DR.U.S.
DISSECTION OF THE TUMOR WITHIN THE INTERNAL
AUDITORY MEATUS

64. DR.U.S.
IDENTIFICATION OF THE INTERNALAUDITORY MEATUS
Tubingen line is the landmark to recognize IAC.
To locate it: Initial step is to identify several vertical
folding of dura located around the area of the
vestibular aqueduct.
After this, folding's of dura upward consistently
reached a linear level where all of the folding's
ended.
And the dura tightly adhered to the bony surface in a
smooth, fold less shape.
Removal of the bone just above the Tubingen line
located the IAC.

65. DR.U.S.
INCISION OF THE PETROUS DURA WITH 11 BLADE KNIFE AND
SEPARATION OF THE DURA FROM PETROUS BONE NEAR IAC
Beware of the SUBARCUATE ARTERY WHICH IS A BRANCH OF THE AICA
It passes over the Internal Auditory Meatus to reach the Subarcuate fossa. Usually it has a long stem. It CAN
CAUSE CONTIUOUS BLEEDING. HENCE NEED TO BE IDENTIFIED AND COAGULATED.
If continuous bleeding occurs a combination of surgicel with coagulation over it is helpful to control the bleeding.
But in case if it has a VERY SHORT STEM FROM AICA THEN ONE HAS TO DISSECT IT BEFORE
CUTTING IT

66. DR.U.S.
DRILLING OF THE IAM. REMOVING THE THINNED OUT BONE USING
FINE CURRETTE
• Drilling of the IAM should be performed at the end of tumor removal
i.e. after nearly removing more than 80-90% of the tumor.
• Don’t attempt to drill in large tumors initially itself because it could
cause distant neurological traction and deficit.
• Don’t drill more than 10 mm from the medial edge of IAM. Maximum
up to the subarcuate crest if it can be clearly seen.
• Use 2mm/3mm cutting burr initially and drill. If diffident, from the
beginning you can use DIAMOND BURR 2 OR 3MM AND DRILL
BUT IT WOULD TAKE LONGER TIME.
• DRILLING DIRECTION SHOULD BE FROM MEDIAL TO
LATERAL.
• In case even if your drill slips, it would slip only towards lateral side
and risk of injury to vital structures are rare.
• When you start drilling , please don’t irrigate for few seconds UNTIL
YOU GET A GOOD GRIP OF THE BONE. THEN YOU NEED TO
IRRIGATE LIBERALLY .
Process of Drilling IAM
After drilling IAM
Tumor

67. DR.U.S.
Dura exposed after drilling the IAM along with the tumor.
Using a fine straight micro scissors make a small nick over the dura over the tumor.
Following that separate the dura longitudinally using either curved ball tipped probe or fine sharp curved
instrument
INTERNAL AUDITORY MEATUS [IAM] SEEN AFTER DRILLING THE
POSTERIOR WALL OF IAM

68. DR.U.S.
Dura opening over the tumor in the IAM using a ball tipped angled probe

69. DR.U.S.
Sharp angled long hook [circle] like micro instrument used to open the dura over the tumor in the IAM
Using Samii knife /disc shaped [circle] micro instrument dissect the tumor located within the IAM

70. DR.U.S.
MEDIAL SIDE: After completing the dissection in the lateral side of the tumor,
from the medial side the arachnoid is peeled off the tumor capsule with a disc
shaped tip instrument

71. DR.U.S.
EXCISION OF THE CAPSULE OF THE TUMOR FROM THE
CRANIAL NERVES
•STIMULATE AND CONFIRM THAT FACIAL NERVE IS NOT PRESENT BEFORE
CUTTING ANY PART OF THE CAPSULE.
•Good understanding and clarity in communication between the Surgeon and the IONM
operator would greatly help in avoiding facial nerve injury.
•To have clear cut strategy of frequency of stimulation of the 7th nerve.

72. DR.U.S.
Plane of dissection is developed between the perineurium and the capsule i.e. in the
subperineurial plane using a disc tipped Micro instrument
TUMOR

73. DR.U.S.
Tumor is dissected away from the nerves from the lateral end of the IAM using a
Samii knife – disc shaped tip instrument directed laterally.
TUMOR

74. DR.U.S.
AS SEEN UNDER OPERATING MICROSCOPE IN LATERAL POSITION
Developing a plane of dissection between the tumor capsule and the perineurium
SUPERIOR
INFERIOR
Perineurium is seen as ARACHNOID LAYER- GLISTENING
TRANSPARENT [Arrow]

75. DR.U.S.
Gentle suction dissection to peel the tumor from the nerves
IX, X CNs
TUMOR
Narrow pole of the tumor capsule peeled away from the
perineurium using DISC DISSECTOR

76. DR.U.S.
Using tumor holding forceps the tumor is gently taken out of the field.
Make sure there is NO ATTACHMENT TO THE NERVES.
IF PRESENT DISSECT THE TUMOR FROM THE NERVES OR VESSELS
NEVER PULL THE TUMOR

77. DR.U.S.
FINAL PART OF THE TUMOR BEING REMOVED FROM THE
PERINEURIUM

78. DR.U.S.
VIEW AFTER REMOVING THE TUMOR –
FACIAL NERVE IS SEEN
Stimulate facial nerve using nerve stimulator using 0.05mV

79. DR.U.S.
INTRAOPERATIVE VIEW UNDER OPERATING MICROSCOPE AFTER
TUMOR EXCISION
COTTONOID KEPT AFTER OBTAINING COMPLETE HEMOSTASIS TO
SEE IF THERE IS ANY FURTHER BLEEDING

80. DR.U.S.
TUMOR CAVITY BED IS LINED WITH SURGICEL

81. DR.U.S.
HEMOSTASIS IS ACHIEVED USING SURGICEL.
Avoid Indiscriminate use of bipolar cautery.
Irrigate copiously to identify any bleeding point.
If bleeding spurter is seen, then use fine tip bipolar at low current to cauterize it precisely

82. DR.U.S.
Small fat is kept over the surgical in the region of the IAM.
Over it again surgical is placed.

83. DR.U.S.
Dura is closed with fascia, since dura would have shrunk in size.
Dural patch taken from the back of the upper dorsal region or nearby fascia over the occipital
region. Fat is placed over it

84. DR.U.S.
Using titanium mesh cranioplasty can be done.
Or using a sandwich of Surgicel – Gelfoam – Nibbled Bone chips with bone
dust – surgical can be placed over the dura to cover the defect [I use this technique]
Most important USE LIBERALLY THE BONE WAX TO SEAL THE MASTOID AIR CELLS
Picture taken from the internet – google images

85. DR.U.S.
RECURRENT ACOUSTIC NEUROFIBROMA
SALIENT FEATURES TO NOTE:
• Be careful during exposure. Consider always there is ABSENCE OF DURA.
• Need to reassess the extent of craniectomy. If needed to drill/ up cut to expose clearly the transverse
sinus and sigmoid sinus.
• Dura may or may not be present. Only fascia may be present instead of dura. The same can be incised
and used during dural closure.
• Cerebellum may be gliotic which can be predicted if MRI scan is properly studied.
• Surgical significance of gliotic cerebellum is it WOULD BE DENSELY ADHERANT TO THE
TUMOR SURFACE and TO THE PETROUS BONE. Surgeon may be forced to perform excision of the
part of the lateral third of the cerebellum to visualize the tumor.

86. DR.U.S.
MRI Scan/ Intra-OP picture showing the Gliotic Cerebellum in Recurrent
ANF
GLIOTIC
CEREBELLUM
GLIOTIC
CEREBELLUM
TUMOR

87. DR.U.S.
RECURRENT ACOUSTIC NEUROFIBROMA
ARACHNOID DISSECTION
SALIENT FEATURES TO NOTE:
• ARACHNOID PLANE MAY NOT BE SEEN – It depends upon the extent of the tumor resection
during the previous surgery. Hence SURGEON NEED TO BE EXTREMELY CAUTIOUS DURING
TUMOR DISSECTION.
• INITIALLY DO MAXIMUM GROSS INTRATUMORAL DISSECTION till
• 1. The lower cranial nerve could be clearly seen with their arachnoid covering.
• 2. Then trace medially, the brainstem with its GLISTENING WHITE SURFACE COULD BE
CLEARLY SEEN.
• 3. Finally if possible DRILL THE IAM, if during previous surgery it has not been drilled.
• 4. If IONM, facilities are available, FREQUENT STIMULATION AND COORDINATION WITH
IONM TECHNICIAN WOULD GREATLY HELP IN PRESERVING THE 7TH NERVE.
• 5. IT IS ADVISABLE TO LEAVE A SMALL BIT OF TUMOR OVER THE FACIAL NERVE SO AS
NOT TO AGGRAVATE THE PRE-EXISTING FACIAL NERVE PARESIS IF PRESENT.

88. DR.U.S.
IMPORTANT POINTS TO NOTE
DISSECTION OF THE TUMOR FROM THE BRAINSTEM:
• STOP WHEN BRADYCARDIA OCCURS [It occurred twice in one of my cases. Following stoppage
of surgery for 5 minutes, pulse rate normalized. Again I proceeded with surgery. No untoward
postoperative sequela]
• STOP WHEN ASYSTOLE OCCURS [It occurred one of my case’s at that point of time, I decided not
to proceed with the surgery. This occurred when trying to remove the last bit of tumor in a recurrent case
of ANF from the brainstem – 7th nerve junction, after clearly delineating the 5th nerve and lower cranial
nerves. There was no untoward postoperative sequelae].
• LESSONS LEARNT, A SURGEON SHOULD KNOW WHEN TO COME OUT OF SURGERY
WITHOUT CAUSING MORE HARM TO THE PATIENT.

89. DR.U.S.
REFERENCES
• Kenichiro Sugita. Acoustic Neurinoma. In Microneurosurgical Atlas. Editor: Kenichiro Sugita. Springer
Verlag, Tokyo. 1985: pp 237-244.
• Albert L Rhoton Jr. Microsurgical anatomy of the cerebellopontine angle. In Neurosurgery. Editors: Robert H
Wilkins, Setti S Rengachary. McGraw Hill, New York. 1996, Vol 1:pp 1063-1083.
• Acoustic Neuromas. Suboccipital approach. Rosenwater RH, Buchheit WA. In Brain Surgery- Complication
avoidance and management. Editor: Michael L J Apuzzo. Churchill Livingstone, New York. 1993: pp 1743-
1771.
• Color Atlas of Microneurosurgical approaches. Cranial base and Midline. Editors: J Diaz Day, Wolfgang T
Koos, Christian Matula, Johannes Lang. Thieme, Stuttgart 1997. pp194-202.
• Samii M., Gerganov V.M. (2010) Suboccipital Lateral Approaches (Retrosigmoid). In: Cappabianca P.,
Iaconetta G., Califano L. (eds) Cranial, Craniofacial and Skull Base Surgery. Springer, Milano.
https://doi.org/10.1007/978-88-470-1167-0_10.
• I do acknowledge few pictures were taken from the above references and from the internet – google images
and videos to clearly document/ describe each step in the presentation.

90. DR.U.S.
FINAL REQUEST TO MY NEUROSURGICAL COLLEAGUES WHO
VIEWED THIS PRESENTATION
•I request each young neurosurgeon the previous day to review the MRI scans displaying it in the x-ray lobby and
make a precise note of the tumor characteristics. Take the note to the OT.
•To go through the operative procedure given in the neurosurgery operative books. If possible VIDEO [AANS HAS
POSTED A VERY GOOD VIDEO ON ACOUSTIC NEUROFIBROMA EXCISION]. Consider all the possible
complications and mentally prepare yourself to tackle it, if they occur during the surgery.
•The MOST IMPORTANT ASPECT IS TO HAVE ONE DAY BEFORE SURGERY TO HAVE A DETAILED
DISCUSSION WITH YOUR SURGICAL TEAM INCLUDING THE OT STAFF NURSE, ANESTHETIST AND
ASSISTANT.
•TO SHOW EITHER STILL PHOTOGRAPHS OR A SHORT VIDEO OF EACH STEP STARTING FROM
POSITIONING TO FINAL SUTURING OF THE SKIN.
•OT Assistants play a vital role during positioning, securing the ET tube, protecting the eyes, brachial plexus and
limbs, genital system. GOOD PREOP PREPARATION IS THE KEY TO SUCCESS OF YOUR SURGERY.

91. DR.U.S.
My sincere thanks to my teachers who taught me the nuances of Neurosurgery
and each one of you for taking time to go through it.
•I sincerely hope this would be useful for the young neurosurgeons who desire to operate on CP ANGLE
tumors/ ACOUSTIC NEUROFIBROMA.
•There would be areas of lacunae in this presentation. I request you to modify and repost it for the benefit of
others.
•In this presentation I have attempted to delineate the most important steps involved during the surgical
excision of the ACOUSTIC NEUROFIBROMA
•It’s solely based upon my experience of operating successfully a series of Acoustic neurofibroma tumors.
•YOU CAN DO IT, OUTSHINE AND PRODUCE BETTER OUTCOME IN THE FUTURE.