SVN -lateral semi-circular canal – Caloric response
90 % of VS cases, Caloric response absent- SVN as source.
It appears to be the experience of most surgeons that the SVN is the most
common nerve of origin of these neoplasm's (Nager, 1964)
Retrospectively reviewed 271 cases of VS - translabyrinthine approach.
They concluded - 80% of the VS arise from the inferior vestibular nerve
7. 200 translabyrinthine cases of VS --superior ampullary nerve
They concluded that majority of VS originate from the inferior
vestibular nerve.Accounting for the poor functional outcome of the middle cranial
fossa approach and better hearing preservation rate reported in
A schwannoma is a tumor that arises from Schwann
cells, named after their discoverer, Theodor Schwann
(a 19th Century German histologist and physiologist)
Acoustic or vestibular
I period—Description of CP angle tumors
and first attempts at surgery
II period—Improvement of the surgical
outcome and introduction of the standard
of complete tumor removal
III period—Development of operative
techniques to preserve the facial nerve
IV period—Modern period of function
preserving safe CP angle surgery
1. Refinements of microsurgical techniques,
2. Combined with improvements in intraoperative
monitoring of facial and cochlear nerve function
3. Advances in neuroimaging
4. Reduction of mortality to optimizing facial nerve
function,1-4 hearing preservation,
5. Preservation of other cranial nerves
Hearing loss, Facial weakness or Balance disorders were
tolerated as simply part of the expected result. – NOW-
GOAL IS TO maintain regional cranial nerve function
29. Whom toobserve
elderly patients without any serious neurological
Bederson et al.7 reported that out of 70 patients, who were
53% had a mean growth of 3.4 mm in the 1st year and
6% had regression of the tumour.
This and another study265 showed that there was no
relationship of tumour growth to age
HCP is usually related to tumor size and occurs more
frequently in association with tumors greater than 3
cm in diameter.
The most common cerebrospinal fluid (CSF)
abnormality associated with these brain tumors in
general is elevated total protein concentration, which is
probably secondary to increased vascular endothelial
38. Including CSFdiversion procedures before, during, or
after tumor removal;
TREATMENT OF HCP ALONE WITHOUT TUMOR
TUMOR REMOVAL ALONE.
IN PREVIOUS YEARS, MANY OF THESE PATIENTS
WERE TREATED BY INSERTION OF A SHUNT FOR
CONTROL OF INTRACRANIAL PRESSURE AND
HCP BEFORE TUMOR EXCISION.
RECENT EVIDENCE, HOWEVER, INDICATES
THAT COMPLETE REMOVAL OF CPA TUMORS
WILL RESULT IN RESOLUTION OF HCP WITHOUT
THE NEED TO INSERT A PERMANENT SHUNT
At least five treatment
options are available for the
associated HCP in patients
with this diagnosis,
39. It has been reported that 3.7% (2) to 15% of patients
with CPA tumors develop HCP.
40. AN INCREASED LEVEL OF PROTEIN in the CSF
has been deemed the main cause of this presentation
on the basis of protein molecules’ clogging the pores of
the semipermeable membrane that forms the barrier in
the arachnoid granulations, leading to impaired
absorption of CSF
41. Tumors of the CPA—especially acoustic neuromas—
are almost always associated with increased protein
levels in the CSF, with values frequently being greater
than 1 g/L .
Passage of CSF over a tumor in a patient with an
abnormal blood-brain barrier, indicated by marked
enhancement with agents such as gadolinium, may
permit leakage of serum proteins into the CSF
42. If the patient is not a candidate for tumor resection-
symptomatic HCP, then consideration should be given
to inserting a shunt.
For the minority of patients with preoperative HCP
who require postoperative CSF diversion, the need for
the shunt usually becomes apparent within the first 2
months after tumor removal
43. HCP has been reported to occur in 3 to 10% of patients
after radiosurgical treatment of CPA tumors
Development of symptomatic HCP in these patients
could be explained by a release of proteinaceous and
cellular debris from tumor cells as a result of radiation-
44. 1. Do not advocate the use of preoperative permanent
shunting in patients with HCP who are candidates for
microsurgical tumor excision.
2. Postoperative follow-up of these patients after
microsurgical tumor excision is safe.
3. Permanent shunting should be considered in those
patients with persistent clinical symptoms and no
reduction in HCP 2 to 3 months postoperatively.
4. Permanent shunting as the only treatment for HCP
(without microsurgical tumor excision) should be
considered in elderly patients with tumors of stable size.
Bipolar facial monitoring orbicularis oculi and orbicularis
Trigeminal nerve masseter.
For hearing monitoring, the ear canal is inspected and
cleaned if necessary; an electronic clicker is placed in the
ipsilateral / CL EAR
scalp to record a brain stem auditory evoked response
(BAER) durng surgery.
lower cranial nerves - endotracheal tube with an
INITIAL DRILLING SHOULD BE LOCATED
FROM 15 TO 25 MM IN THE
POSTEROINFERIOR DIRECTION OF THE
ASTERION TO AVOID ANY TYPE OF INJURY
TO THE VENOUS SINUS
The medial dura is left intact to protect the cerebellum.
Too much CSF when the dura is not fully opened; doing
so can be associated with too much cerebellar relaxation,
causing a venous tear near the tentorium or in the area of
the petrosal sinus.
This can be difficult to control and forces a more rapid
dural opening than might be desired.
DRYING OF DURA AND MICROSCOPIC LIGHT
First, the dura of the posterior wall is coagulated and
incised in a pie-shaped fashion with a base at the porus
The lateral extent of the canal opening is determined from
the CT bone window;
however, care must be taken to avoid injuring the
vestibule and thereby causing a subsequent loss of
hearing. The horizontal extent of the tumor is usually 8-13
mm. whereas the vertical extent is 6-8 mm.
70. Total versus
COMPLETE REMOVAL IS A RULE
It must be kept in mind that subtotal removal will lead
to eventual recurrence, and revision surgery is more
difficult and has a worse outcome than primary
In patients over 70 years of age, a small part of the
tumor may be left over the facial nerve at the level of
Thin layer of tumor over the brainstem in all cases
In case of intraoperative complications
bradycardia during surgery at the brainstem
Anaesthesia related complications.
Anatomical variation (e. g., extremely lower-lying
middle cranial fossa dura, remarkably protruding
sigmoid sinus and jugular bulb). In such a case,
another approach is applied later
Will open large cerebello medullar cistern and surgical
localize cranial nerves IX and X, which are best identi
ed near the jugular foramen medial to the jugular bulb
Till where you dissect
103. Middle fossa approach
especially in lat part with
the aim of facial nerve &
unroofing of IAC
104. Middle fossa approach
IAC exposed by following GSPN to the geniculate
The bone is then drilled off the arcuate eminence
until only a thin layer of bone remains over
superior semicircular canal→Posterior boundary
of the dissection of IAC
VII nv. followed from geniculate ganglion to the
lateral end of the IAC
105. Middle fossa approach
Extra dural dissection
Complete exposure of the
Avoid blind dissection in
Total removal of Tumor
even the lateral part- good
for small tumors.
Hearing preservation (50-
No risk of CSF leak
Facial nerve comes first-
Limited access to post
fossa, esp. if there is
Elderly patients with thin
dura are less tolerant to
temporal lobe retractionPost op Complications:
112. Once the key landmarks have been identified, the IAC can
be localized using two key angles.
Traditionally, the GSPN-SSC angle (120 degrees)6 and the
SSC-IAC angle (60 degrees)17 have been used.
Once the IAC has been identified, exposure proceeds
from lateral to medial until the entire IAC has been
exposed along its superior surface
The early series from Karolinska used high doses of 25 to 35 Gy.
Kondziolka 1987 to 1992 that included 162 consecutive
patients with a mean transverse tumor diameter of 2.2 cm
and an average dose to the tumor margin of 16 Gy
Gamma Knife systems deliver doses to the periphery that
are generally 50% of the peak dose delivered to the
center of the tumor. Further reductions in the marginal
dose have resulted in a decrease in side effects when
doses lower than 13 Gy were used
The reduction in dose lowered the rate of facial
neuropathy from 29% to 5% and lowered the
morbidity of trigeminal neuropathy 2%
IMPROVEMORE CT – MRI
Radiosurgery is well suited for acoustic neuromas as it is
typically well demarcated from surrounding tissues on
Andrews and coworkers compared the results of
radiosurgery with FSRT in a study involving 125 patients.
Both radiosurgery and FSRT yielded excellent results, but
FSRT has been described by some to have a higher rate
of hearing preservation if the patient had serviceable
However, fractionation requires that patients make
frequent trips for treatment and may be more difficult for
patients who do not live close to a treatment center.
121. How toasses
Post SR imaging studies show a characteristic loss of
central contrast enhancement within the tumour, occurring
most commonly within 18 months of therapy.
This loss of central contrast enhancement has been
postulated to be due to radiation induced vascular injury
A peritumoural increased T2 signal may appear transiently
as may changes in the blood brain barrier with regres-
sion in tumour size in the region of the middle cerebel- lar
peduncle. These changes occur more commonly in
tumours greater than 15 mm in diameter
limited by its inability to expeditiously relieve mass effect
in patients for whom this is necessary.
The radio- biological nature of SRS also requires lower,
potentially less effective doses for higher target volumes
to avoid complications
The field of endoscopy has evolved from earlier “endo-
scope-assisted microsurgery” to complete endoscopic
Improved visualisation, more complete tumour removal,
and a lowered risk of CSF leakage.
Endoscopic or endoscope assisted removal of acoustic
schwannomas seems to be a tech- nically feasible, e
ective and safe procedure; however, good equipment and
special training are absolutely nec- essary for a ainment of
de novo acoustic schwannomas with the tumour size
ranging from 0.6–5.7 cm (most tumours were less than 3
cm in diameter and had a mean of 2.6 cm).
Tumours were removed via 1.5 cm “keyhole” retrosigmoid
craniotomies. Utilising the fully endoscopic technique, 106
out of 112 (95%) tumours were completely remov
Radical subtotal removal describes the procedure when
an extensive removal is done except for a portion of the
capsule le a ached to the brainstem or the facial nerve.
Wallner et al.,272 found the recurrence rate following
radical subtotal excision to be 9% and that following
subtotal excision to be 40%.
Auditory Brain stem Implant
The main and first indication for ABI is NF-II.
Emergent indications are bilateral total ossified
cochlea, VS with controlateral lesions or in a single
hearing ear, cochlear nerve aplasia or inner ear
143. The PubMed and Embase electronic databases were searched from
1990 - 2014, with additional data being gleaned from the Cochrane
Central Register of Controlled Trials, and Web of Science.
Well designed, prospective
Randomized control studies
Well designed comparative clinical
Case series, Historical controls, case
reports and expert opinions.
Level 3: It is recommended that MRI be used to evaluate patients with
asymmetric tinnitus/ sudden senorineural hearing loss
Level 2: Postoperative evaluation should be performed with postcontrast 3-D
T1 magnetization prepared rapid acquisition gradient echo (MPRAGE), with
nodular enhancement considered suspicious for recurrence.
1)MRIs should be obtained annually in all postoperative cases for 5 yr, with
interval lengthening thereafter with tumor stability.
2)The degree of lateral internal auditory canal involvement by tumor
adversely affects facial nerve and hearing outcomes
3)Standard T1, T2, FLAIR, and DWI MR sequences obtained in axial, coronal,
and sagittal plane may be used for detection of VS.
To support the superiority of either the middle fossa (MF) or the retrosigmoid (RS) approach for
complete VS resection and FN preservation when serviceable hearing is present.
To support the superiority of either the RS or the TL approach for complete VS resection and FN
preservation when serviceable hearing is not present.
Surgical resection should be the initial treatment in patients with NF2.
Patients with larger VS tumour size should be counselled about the greater than average risk of loss
of serviceable hearing.
Hearing preservation surgery via the MF or the RS approach may be attempted in patients with
small tumour size (<1.5 cm) and good preoperative hearing.
Surgical resection of VSs may be used to better relieve symptoms of trigeminal neuralgia than SRS
146. FACIAL NERVE MONITORING
1)It is recommended that intraoperative facial nerve monitoring be
routinely utilized during VS surgery to improve long-term facial
2) Intraoperative eighth cranial nerve monitoring should be used
during VS surgery when hearing preservation is attempted.
Level 3: When there has been progression of tumor after SRS, SRS can
be safely and effectively performed as a retreatment
147. EMERGING THERAPIES
1)Bevacizumab be administered to improve hearing or prolong time to
hearing loss in patients with NF2 without surgical options.
2) Lapatinib may be considered for use in reducing VS size and
improvement in hearing in NF2.
3) Erlotinib is not recommended for use in reducing VS size or
improvement in hearing in patients with NF2.
4)Everolimus is not recommended for use in reducing VS size or
improvement in hearing in NF2.
5) Perioperative treatment with nimodipine (or with the addition of
hydroxyethyl starch) should be considered to improve postoperative
facial nerve outcomes and may improve hearing outcomes.
6)It is recommended that aspirin administration may be considered for
use in patients undergoing observation of their VS.
Poor exposure of lateral end of
the internal auditory canal
CSF leak (7-21%)
Persistent postop headache
Good exposure of the CPA cistern
Good for medial tumors
Even large Tumor
Hearing preservation (50% in
Direct visualization of vessels
SDS > 50% serviceable hearing
Retro sigmoid approach best to preserve
Surgery can improve hearing in some cases
cochlear nerve monitoring
Hearing aids and brainstem implants!!!!
Neurosurgery. 1997 Feb;40(2):248-60; discussion 260-2.
Management of 1000 vestibular schwannomas (acoustic neuromas): hearing function in 1000 tumor resections.
The realistic chances of hearing preservation and the comparability of international results on hearing preservation in
complete microsurgical vestibular schwannoma resections were the focus of this study in a large patient population
treated by uniform principles.
One thousand vestibular schwannomas were operated on at Nordstadt Neurosurgical Department, from 1978 to 1993, by
the senior surgeon (MS). There were 1000 tumors in 962 patients, i.e., 880 patients with unilateral tumors and 82
patients operated on for bilateral tumors in neurofibromatosis-2 (120 cases). Preservation of the cochlear nerve was
attempted whenever possible. The audiometric data were analyzed by the Nordstadt classification system and
graded in steps of 30 dB by audiometry and in steps of 10 to 30% by speech discrimination; for comparability, the
data were also evaluated by the criteria of Gardner, Shelton, and House, and they were assessed in relation to the
Hannover tumor extension grading system.
Anatomic cochlear nerve preservation was achieved in 682 of 1000 cases (68%), as well as in some preoperatively deaf
patients, a very few of whom regained some hearing. Of a total of 732 cases with some preoperative hearing,
Functional cochlear nerve preservation in complete microsurgical resection should belong to the contemporary standard
of treatment goals.
172. Neurosurgery. 2003 Jun;52(6):1436-40; discussion
Second tumors after radiosurgery: tip of the iceberg or
a bump in the road?
Radiosurgery-associated second tumors have been reported in four isolated patients during the past 2 years. In our own
experience, we are aware of two additional patients. The purpose of this report is to call attention to this potentially
Four patients were found in the literature, and two additional patients were seen by the authors. Malignant tumors
occurred as early as 6 years after radiosurgery. The pathological findings in three of these four malignant tumors were
glioblastoma multiforme. Benign tumors developed between 16 and 19 years later. Tumors developed both within the
full-dose prescription volume and in the lower-dose periphery. Of interest, three of the six patients experienced
complications of the radiosurgery treatment before developing second tumors.
Although patients will increasingly be reported with second tumors after radio surgery in the future, the overall
incidence seems quite low and should not alter current radio surgical practice. However, continual surveillance of
treated patients should be considered.
173. World Neurosurgery 2010 Jun;73(6):751-4..
Malignant peripheral nerve sheath tumor arising from benign vestibular
schwannoma treated by gamma knife radiosurgery after two previous
surgeries: a case report with surgical and pathological observations.
We describe a case presenting with malignant peripheral nerve sheath
tumor (MPNST) at 8 years after GKRS after incomplete resections.
The tumor appeared to be a typical benign schwannoma at the surgery
preceding GKRS, and rapidly enlarged after long-term control, causing
progressive neurological deterioration. Operative findings showed that
the tumor was composed of two different components, and
histopathology distinctively demonstrated MPNST and benign
The coexistence of benign and malignant components might indicate that the
present MPNST had arisen from the benign schwannoma by transformation
in association with GKRS.
174. World Neurosurg. 2014 Mar-Apr;81(3-4):594-9.
Secondary neoplasms after stereotactic radiosurgery.
Patel TR1, Chiang VL2.
The use of medical radiation has increased 6-fold in the past 30 years. Within neurosurgery, the advent of stereotactic
radiosurgery (SRS) has significantly altered the treatment paradigm for both benign and malignant central nervous
system diseases. With this increased reliance on radiation has come a responsibility to identify the long-term risks,
including the potential development of radiation-induced neoplasms. Although the data regarding traditional radiation
exposure and its subsequent risks are well-defined, the data for SRS is less developed.
We reviewed the published literature to more accurately define the risk of developing secondary neoplasms after
A total of 36 cases of SRS-induced neoplasms were identified. More than half of the cases had an initial diagnosis of
vestibular schwannoma. Overall, the risk of developing an SRS-induced neoplasm is approximately 0.04% at 15 years.
The risk of developing an SRS-induced neoplasm is low but not zero. Thus, long-term surveillance imaging is advised for
patients treated with SRS.
Vestibular schwannomas grow at an average
0.66 mm/y and 0.19 cm3/y
The have a mean volume-doubling time of
4.4 years (Level l evidence).
microsurgery (MS) and stereotactic
radiosurgery (SRS) have equivocal tumor
control rates (Grade 1 C Recommendation, Level
However, tumor growth can be irregular and
there can be periods of no growth, slow growth,
and sudden growth (Levell and II evidence).
Therefore, a •wait-and-see approach is reasonable
for intra canalicular tumors or those with a
cerebellopontine diameter< 20 mm
176. SRS compared with MS
I. Patients treated with have improved
facial nerve function and hearing
outcomes (Levels II and Ill evidence).
II. SRS should therefore be the first-line
treatment for older patients
III. However, long-term control rates are
still not known for SRS, and this fact
must betaken into account when
counseling the patient, especially
Tumors> 30 mm
Not appropriate for SRS and
should be treated with MS
unless the patient has co
morbidities that preclude
Level IV Evidence
No High quality evidence
The patient should be counseled
appropriately regarding the current
understanding of the natural history
of VS and contrast it with outcomes
after MS and SRS to elect the most
appropriate course of management
(Grade 2C Recommendation, level
186. Decision Making
● Tumor size.
● Preoperative hearing for both ipsilateral and
contralateral side (based on pure tone audiogram, speech
discrimination scores, and occasionally auditory
brainstem response [ABR]).
● Patient’s preoperative general condition (anesthetic
● Patient’s expectations.
187. Surgeon Factors
Personal experience and preference.
It is important that the surgeon knows all the
approaches available, so that he or she is able to choose
the best approach for the individual patient.
188. Nonsurgical treatment is preferred in the following
● Small tumors in elderly patients.
● Tumor in the only hearing ear.
● Tumor in the patient with poor general condition.
15–20% of the tumors continue to grow after
PREVIOUS RADIOTHERAPY -the tumor is more
adherent to the brain- stem and the cranial nerves,
and also because the arachnoid plane is destroyed by
193. Facialnerve identification
Nerve involved by tumour should be identified proximal and
distal to tumour, where its displacement and distortions are
Landmarks Choroid plexus and Foramen of Luscka , Floculus
Slight greyish colour which is different from the adjacent
Flattened facial and cochlear nerves do not have an
arachnoidal layer separating them from the tumor capsule.
Bits of tumour attached to the nerve can be left alone