Microsoft Word - 7IacobG_LargeAndGiant.doc
Romanian Neurosurgery (2010) XVII 3: 305 – 312 305
Large and giant vestibular Schwannomas
G. Iacob, M. Craciun
Clinic of Neurosurgery, Universitary Hospital Bucharest Romania
Motto: “If any neurologic surgeon were asked to name the most difficult tumor to
extirpate, his answer would doubtless to be the acustic tumor”
Dandy (1)
Abstract
Background: The main objective in
treating large and giant vestibular
schwannomas (VS) (large - diameter
exceeding 3.5 cm and giant - diameter
exceeding 4.5 cm) is their complete
removal without significant morbidity. Our
experience on 7 cases (4 females, 3 males,
mean age 42.5 years) with marked
brainstem compression, operated between
2004-2009 focuses on factors influencing
recurrence and morbidity, especially related
to facial nerve function. These patients
were included in a series of 32 consecutive
vestibular schwannoma excisions.
Methods: This report is a retrospective
analysis of the surgical outcome of 7
patients with large and giant VS using the
retrosigmoid-transmeatal approach. Several
prognostic factors were evaluated: patient
age, tumor size and consistency, extent of
surgical removal, concurring
hydrocephalus, hearing loss, facial nerve
function, trigeminal nerve deficits, cranial
nerve VI, IX and X palsy, tongue edema,
ataxic gait and motor deficits.
Results: The mean age was 42.3 years, the
mean tumor diameter was 51.8 mm. There
were no deaths and the tumors were
histologically benign. Extensive
microscopic tumor resection was
performed in 5 cases related to solid
tumor’s consistency. Preoperatively hearing
loss and high intracranial pressure were
encountered in all patients. 4 patients had
cerebellar ataxia. Facial anatomical
continuity was preserved in 6 cases with
solid tumor consistency; 4 patients had a
preoperative facial palsy, a good facial nerve
function was achieved in 3 cases – House-
Brackmann grade I/II. We have met other
distinctive signs: cranial nerve V
hypoesthesia, VI, IX and X palsy, tongue
edema in 2 cases with slight contralateral
motor deficit. All patients were clinical and
MRI monitored at 3, 6 and 12 months
postoperatively.
Conclusion: Total resection associated
with a low morbidity rate is possible,
avoiding recurrence, reintervention and
severe scar tissue. In cases with subtotal
resection, radiosurgery is recommended to
improve outcome.
Keywords: large and giant vestibular
schwannomas (VS), surgical approach,
facial nerve function
Introduction
The progress of neurosurgery as a
specialty is related to the history of a
vestibular schwannoma (VS) – the more
accurate term of the classical acoustic
306 G. Iacob, M. Craciun Large and giant vestibular Schwannomas
neuroma, suggesting the tumor origin from
the superior (upper) division of the
vestibular nerve, not from the cochlear (also
known as the acoustic) nerve (2).
Microsurgical removal of large and giant
VS is a daunting task to surgeons,
presenting a greater challenge in the quest
for total removal - based on a clear surgical
strategy, functional cranial nerve
preservation and avoidance of any
complications (3-8).
For VS larger than 3 cm, associated with
significant compression of the brainstem,
Gamma knife therapy cannot be used
because of the need to program more than
one isocenter for the radiation dose,
exposing normal neural tissue to excess
amounts of radiation (5)(9).
We have made a retrospective analysis of
the surgical outcome of 7 patients with
large and giant vestibular schwannomas
operated using the retrosigmoid-
transmeatal approach.
Material and methods
From 2004-2009, 32 consecutive VS
resections were performed by the senior
author (G.I.) using the retrosigmoid-
transmeatal approach. Inclusion criteria
were all VS larger than 3 cm in size,
corresponding to grade IV Koos
classification. We have identified in a review
of the operations 7 cases with large or giant
VS: 4 females, 3 males, mean age 42.5 years
(ranging from 38-68 years).
Preoperative hearing loss - the threshold
retained for useful hearing was 60 decibel –
Norstadt classification for audiometric
hearing (10) and high intracranial pressure
with obstructive hydrocephalus were
encountered in 2 patients. 4 patients
(57.14%) had cerebellar ataxia; 5 patients
(71.42%) had facial numbness, paresthesia;
4 (57.14%) patients had a preoperative facial
palsy; 3 (42.8%) patients had swallowing
difficulties and contralateral motor deficit
was observed in 2 (28.57%) patients
All patients underwent CT, MRI T1 -
weighted imaging before and after
Gadolinium (Gd ) administration and T2 –
weighted imaging pre and postoperative;
measurements were made on the largest
diameter of the tumor excluding
intracanalicular components. Tumors
classified as large presented a diameter
above 3.5 cm, whereas the diameter of giant
tumors exceeded 4.5 cm. There were 4
(57.14%) cases with giant tumors and 3
(42.85%) cases with large tumors (mean
tumor diameter was 51.8 mm). The
tumor’s consistency was classified as solid
or cystic using T1 and T2 – weighted image
with Gd administration. We found that
28.5% of VS (2 cases) included in our study
contained cystic elements.
Surgery was performed using the
retrosigmoid – transmeatal approach in the
lateral decubitus. In 2 cases a temporary
shunt was placed intraoperatively to relieve
hydrocephalus. A retrosigmoid suboccipital
craniotomy of 4 cm diameter was made to
expose the posterior part of the sigmoid
sinus and the inferior part of the transverse
sinus. We favor such an approach for the
following arguments: a wider field of
action, direct visualization of anterior
inferior cerebellar artery (AICA) and other
brain stem vessels, dissection of all surfaces
of the acoustic tumor always under direct
vision, identification of the facial nerve in
the lateral angle of the internal auditory
canal, ready access to the facial nerve when
either anastomosis or graft reconstruction
may be necessary.
The surgical technique was based on
internal tumor debulking made in a
Romanian Neurosurgery (2010) XVII 3: 305 – 312 307
systematic fashion. The ultimate goal of VS
surgery being cranial nerves preservation,
tumor removal is merely a byproduct. The
surgical steps after dural opening tangent to
sinuses are:
-cisterna magna opening to allow
cerebellar retraction, made by applying a
single broad malleable blade from below
upwards
-identification of the double arachnoid
membrane protecting the cerebellum,
lower cranial nerves, anterior inferior
cerebellar artery (AICA)
-the tumor capsule is separated from the
cerebellum and the inferior tumor part is
elevated from the lower cranial nerves and
brain stem
-centrifugal, rapid, tumor debulking, to
shrink tumor using tumor forceps,
dissector (CUSA may perforate the
arachnoid layer and damage the neural
vasculature!); it’s better to leave a shelf of
tumor “capsule” all around to avoid injury
to all structures outside it
-the tumor is further separated at the
upper pole from the trigeminal nerve and
pons
-the meatus acusticus internum is
exposed in two stages: drilling away the
back wall, carrying out the remaining upper
tumor; optional drilling the fundus. It is
mandatory to avoid the semicircular canals
(laterally) and the jugular bulb (inferiorly)
whilst drilling; copious water irrigation
whilst canal drilling to prevent thermal
injury to VII & VIII complex; stripping the
dura from canal; waxing bone edges to keep
the field bloodless; placement of muscle
patch in IAC after tumor removal to
prevent CSF leak
-fine dissection close to nerves - the
remainder is separated from the facial
nerve, brain stem, abducens nerve using a
water-jet dissection. In our series, the facial
nerve was displaced over the medial aspect
of the tumor. Dissection was made
bidirectional from the medial and lateral
direction meeting near the meatus
acousticus internum where most
adherences are to be seen. A small part of
the capsule attached to the nerve should be
leaved. Several blood vessels should be
preserved: internal auditory artery, AICA
and its branches – the most displaced vessel,
SCA, brain stem perforators; also the
petrosal and mesencephalic veins.
-dura is closed watertight using a wet
fibrinoid-based collagen fleece
(Tachocomb), bone flap is refixed.
-for extensive adherences of the tumor
to the facial nerve and also to the brainstem
in 2 (28.57%) cases a partial tumor removal
was performed; no bipolar coagulation was
used for hemostasis in this situation:
applying a cottonoid, a Gelfoam or Surgicel
is temporarily sufficient. Trauma to
arachnoidless brain stem surface can be
predicted on pre-op CT/MRI. Possible
postoperative complications could be
induced by: forceful retraction of a densely
adherent tumor, traction on the bridging
vessels wich may lead to intra-pontine
hemorrhage and coagulation of perforators
that can induce brain stem infarction. To
avoid such complications, tumor feeders
should be coagulated and sectioned where
they enter the tumor; also staying within
the tumor arachnoid holds the key.
Functional outcome was measured using
the Karnofsky scale at 3, 6, 12 months
postoperatively. Several prognostic factors
were evaluated: patient age, tumor size and
consistency, extent of surgical removal,
concurrent hydrocephalus, hearing loss,
facial nerve function according to House-
Brackmann scale, trigeminal nerve deficits,
308 G. Iacob, M. Craciun Large and giant vestibular Schwannomas
cranial nerve VI, IX and X palsy, tongue
edema, ataxic gait, motor deficits.
Results
Extensive microscopic tumor resection
was performed in 5 (71.42%) cases;
diagnosis was confirmed by histopathology
in all cases. There were no deaths and the
tumors were histological benign (Figure 1).
Partial tumor removal was performed for 2
cystic tumors were the arachnoidal plane
was poorly defined, with severe adherences
to brainstem and facial nerve, extensive
bleeding and cerebellar edema.
Facial nerve anatomical continuity was
preserved in 6 (85.71%) cases with solid
tumor consistency and a good facial
function was achieved in 3 (42.85%) cases -
House Brackmann grade I/II. For 4
(57.14%) patients with giant VS, the facial
nerve deficit worsened postoperatively with
respect to House-Brackmann grading scale
by III grades, the face was rehabilitated with
plastic surgery techniques.
We have noticed a rapid tumor growth,
short symptom duration and facial nerve
involvement in 2 cystic tumors were a
partial resection was performed.
The Karnofski score at discharge was
superior to 80%. The major complications
in this series were: 3 (42.85%) patients with
cranial nerve V hypoesthesia, 5 (71.42%)
patients with increased facial numbness, 4
(57.14%) patients with transient VI, IX and
X palsy, tongue edema and 2 (28.57%) cases
with contralateral motor deficit. These
patients recovered well within 6 months
after operation.
In 2 cases with partially resected cystic
tumors, at 12 months after the operation we
have noticed on CT and MRI the same
dimensions of the tumor remnants.
Figure 1 Preoperative cerebral CT showing giant VS (51 mm) with obstructive hydrocephalus (A-C);
postoperative cerebral CT after 1 year follow-up showing complete resection (D, E); another case with giant VS
(57 mm) showing pre and postoperative CT
Romanian Neurosurgery (2010) XVII 3: 305 – 312 309
Discussion
VS are typically slow growing, benign
skull base tumor of cerebellopontine angle,
with natural unpredictable evolution and
annual growth rate between 0.2-2 mm; they
originate from the intracanalicular part of
the vestibular nerve, in the region of the
transition zone between central and
peripheral myelin (2).
While VS was first described by Eduard
Sandifort in 1777, the first successful
surgical removal was achieved by Sir
Charles Balance in 1894, cited by (2).
Several neurosurgical pioneers made major
advancements in managing this usually
benign skull base tumor: F. Krause who
introduced the retrosigmoid approach to
the cerebellopontine angle and H. Cushing
who advocated for subtotal removal and
was the first to reduce mortality from 50 to
7.7% - cited by (11). W. Dandy (1)
recommended total excision with
meticulous capsule dissection as goal of
surgery in order to prevent recurrences,
with an acceptable low mortality of 2.4%. In
1967 Olivecrona (12) proposed to preserve
the facial nerve, achieving this in 20% of his
304 patients with a total tumor removal in
217 patients and a mortality rate rising up to
23%.
The translabyrinthine approach was
adopted by Panse in 1904 - cited by (2) as a
method to achieve tumor removal
preserving the facial nerve. In 1964 House
(13) introduced operating microscope for
translabyrinthine approach and in 1965
Rand and Kurze - cited by (2) were the first
to introduce an operating microscope for
the transmeatal posterior fossa approach.
Yasargil (14) improved the microsurgical
technique, emphasizing the importance of
the brain stem arterial supply and the need
to optimize the preservation of facial nerve
function. These technical advances have led
to a 50% reduction in mortality, a rate of
complete tumor removal reaching 85% and
to a successful anatomical preservation of
the facial nerve in 80% of the cases.
The management of VS has evolved
significantly with the advent of new
radiological diagnostic procedures (high
resolution CT, multiplanar MRI) that allow
early diagnosis of small and medium size
VS; safe, modern anesthesia, development
and refinements in the microsurgical
techniques, neurophysiological
intraoperative monitoring and working in
multidisiplinary teams have led to a
dramatic improvement in clinical outcome,
with an operative mortality of around 1%
and a rate of total tumor removal close to
95% (2-9)(15-24).
In some expert hands: Koos W. (18),
Rhoton Al. (21), Samii M. (2)(6), Noren
G., Regis J., Pellet W., Cannoni M. – cited
by (11), the preservation of useful hearing
(Gardner-Robertson 1 or 2) has been
achieved in selected small lesions with very
good preoperative hearing and also the
possibility of preserving normal facial
motor function in many cases (House-
Brackman 1 or 2).
Although surgical procedures could be
complex and difficult, even in large and
giant VS compressing the brainstem, a
complete tumor removal has become the
rule in many cases, preserving all cranial
nerves in exceeding numbers, without
additional morbidity or mortality. In many
cases the VIIth nerve may be so thin that it
could be be confused with the arachnoid
when very severely compressed. There are
various anatomical relationships
encountered during resection; nerve
stimulator, electrophysiology may allow a
gentle separation of VII nerve from tumor
310 G. Iacob, M. Craciun Large and giant vestibular Schwannomas
by using micro dissector & sharp arachnoid
dissection (6)(7)(18).
Brainstem compression, even brainstem
dislocation, cerebellum and severe fourth
ventricle compression can produce
ventricular dilatation; the VII & VIII
complex, lower cranial nerves severely
stretched occur in large or giant VS
(10)(18).
The most common clinical signs (5) are:
cophosis, cerebellar ataxia, symptoms of
raised intracranial pressure (headache,
papilledema) and symptoms of normal
pressure hydrocephalus in elderly (gait
disturbance, dementia and incontinence).
In our series a temporary shunt was placed
intraoperatively to relieve hydrocephalus in
2 cases; generally the need of a preoperative
shunt was as high as 66% in ancient series
(14), others consider shunting rarely
required because total surgical excision is
sufficient (7).
The approach is controversial: many
surgeons prefer the retrosigmoid approach
in the sitting, semi-sitting or lateral position
(2-8)(15)(17-19)(21)(23). However Sami
(6) reported a high incidence of hematoma
after retrosigmoid removal of cystic tumors
in the semisitting position, as well as air
embolism irrespective of anesthetic
monitoring measures taken to prevent this
complication. In the lateral position the
peritumoral veins may generate
intraoperative bleeding (5). The
translabyrinthine approach is advocated by
ENT surgeons for good tumor exposure
with minimal retraction of the cerebellum,
early facial nerve identification and eases
the repair of the facial nerve when it is
transected (5)(13)(15)(16)(20)(24)(25). The
disadvantages of the translabyrinthine
approach (4) are: longer operating times,
higher rates of postoperative facial paralysis
and the risk of cerebrospinal fluid leak.
In large VS, Anderson (3) described a
combined translabyrinthine-retrosigmoid
approach especially for more lateral giant
tumors that extend to the fundus of the
IAC. The rates of preserving good facial
nerve function are similar among the
retrosigmoid, translabyrinthine and middle
fossa approaches in large VS: 42-52.6% with
early identification of the root entry/exit
zone and caution in tumor excision in the
extrameatal region just outside the porus
acusticus (5). Only 18% of operated
patients have excellent facial nerve function
(House-Brackmann grade I/II) explained by
the bad initial clinical status, the tumor size
and the lack of systematic intraoperative
facial monitoring (5)(8)(17)(19)(23).
According to Sami (6) facial nerve
anatomical results (of 200 cases of grade T4
VS, total removal was achieved in 98% and
anatomical facial nerve preservation was
possible in 98,5%) were not correlated with
functional results, while size was well
correlated with facial function. Even when
the facial nerve is left anatomically intact,
surgical interventions can have esthetic and
functional consequences which greatly
reduce the quality of life (4).
Removal of large and giant residual or
recurrent VS is more difficult due to scar
tissue and the absence of a clear arachnoid
plane between tumor and brainstem,
vessels, and nerves even for the most
experienced surgeon (11,18). When
excision is incomplete, the recurrence rate
is usually high, depending of VS cellularity
and vascularisation (7). Recurrence rate
reported was of 0-3.9% for gross total
removal; 9.4-29% for near total resection as
a result of surgical devascularization and
25-65% for subtotal resection, especially in
Romanian Neurosurgery (2010) XVII 3: 305 – 312 311
the midcerebellopontine angle after the
translabyrinthine approach (24). Vestibular
schwannomas can relapse 10-15 years
postoperatively (10% of patients) even
when surgeons have the impression that
these have been completely removed (4).
The growth rate of residual or recurrent VS
is unpredictable: most authors reported a
very low recurrence rate after complete
tumor excision; however, a higher
recurrence rate after subtotal removal has
also been observed in 44-53% of patients
(5). In cystic tumors (26) a rapid tumor
growth with possible vascular compression
led to a less favourable outcome than solid
tumor, also some tumor remnants may not
grow. Also cystic VS demand careful
dissection and may be subtotally resected
for various reasons: the arachnoid plane is
not easily preserved as it is densely adherent
to the surrounding structures; the cranial
nerves are displaced in a relatively uncertain
position; cyst formation may predict a more
intimate involvement of the neural tissue;
high tendency to postoperative bleeding;
dissection of the facial nerve from the
tumor is more difficult (5)(6)(22).
For subtotal tumor debulking confirmed
by MRI at 3 months, 6 months to 1 year
postoperatively, the alternatives are
(5)(6)(9)(17)(22)(26):
-planned staged approaches – first tumor
debulking via a retrosigmoid approach
followed by a second stage translabyrinthine
resection of the residual tumour
-wait and see – in case a a small and
stable residual tumor in elderly patients
-subtotal tumor debulking followed by
stereotactic radiotherapy which can offer
excellent facial nerve function in 85.7%
patients with House-Brackmann grade I/II
(1) and tumor growth control. At the time
of radiosurgery the tumor size is
diminuished < 20 mm and radiosurgery
could be made with a peripheral dose 11-13
Gy and in the tumor centre the dose should
be 22-26 Gy.
Conclusion
VS is a benign tumor in a malignant
location (2). Progressive improvement in
the results of VS surgery was possible
owing to: better clinical preoperative
deficits evaluation, tumor size (the smaller
the tumor, the better the outcome !),
imaging innovations, intensive care,
intraoperative monitoring, advent of
microsurgery and of course increasing
surgical experience (6-8)(18).
Complete VS removal at one stage while
preserving neurological functions and the
quality of life should be the optimal
treatment, thus avoiding recurrency,
reintervention and severe scar tissue.
For large and giant VS the optimal
treatment should be tried; however an
alternative could be the combined staged
therapy: subtotal intracapsular resection
relieving mass effect and brainstem
compression at the first stage, follow-up
and stereotactic radiosurgery at a second
stage for the residual tumor.
References
1.Dandy W.E. - Results of removal of acustic tumors by
the unilateral approach, A.M.A. Arch. Surg. 1941, 42:
1026-1043
2.Samii M. – Vestibular schwannomas, Sindou M. -
Practical Handbook of Neurosurgery, Springer Wien
New York, 2009, 333-345
3.Anderson D.E., Leonetti J., Wind J.J. et al. – Resection
of large vestibular schwannomas: facial nerve
preservation in the context of surgical approach and
patient assessed outcome, J.Neurosurg. 2005, 102 (4):
643-649
4.Fuentes S., Arkha Y., et al. – Management of Large
Vestibular Schwannomas by Combined Surgical
Resection and Gamma Knife Radiosurgery, in Regis J.,
312 G. Iacob, M. Craciun Large and giant vestibular Schwannomas
Roche P.H. - Modern Management of Acustic
Neuroma, Karger 2008, 79-82
5.Laghmari M., Ouahabi A. El., Derraz S., Khamlichi A.
El. – Treatment of large vestibular schwannomas:
Towards a compromise between recurrence and facial
function preservation, Pan Arab Journal of
Neurosurgery, 2009, vol.13, 1: 31-39
6.Samii M., Gerganov V., Samii A. – Improved
preservation of hearing and facial nerve function in
vestibular schwannoma surgery via the retrosigmoid
approach in a series of 200 patients, J. Neurosurg 2006,
105: 527-535
7.Turel K.E. – Surgical techniques & pitfalls in acustic
neuroma, Romanian Neurosurgical Congress,
Timisoara 2003.
8.Yamakami I., Uchino Y.,Kobayashi E. et al. – Removal
of large acoustic neurinomas (vestibular schwannomas)
by the retrosigmoid approach with no mortality and
minimal morbidity, J. Neurol Neurosurg Psych 2004,
75: 453-458
9.Lunsford L.D, Niranjan A., Flickinger J.C., Maitz A.,
Kondziolka D. – Radiosurgery of vestibular
schwannomas: summary of experience in 829 cases, J.
Neurosurg. 2005, 102 (Suppl): 195-199
10.Malis Li – Nuances in acoustic neuroma surgery,
Neurosurg. 2001, 49: 337-341
11.Regis J. et al. - Introduction, in Regis J., Roche P.H.
- Modern Management of Acustic Neuroma, Karger
2008, 1-5
12.Olivecrona H. - Acustic tumors, J. Neurosurg 1967,
26: 6-13
13.House W.F. - Translabyrinthine approach, in House
W.F., Luetje C.M. (eds) - Acustic Tumors, Baltimore,
University Park Press 1979, 43-87
14.Yasargil M.G. et al. - Microsurgical approach to
acoustic neuromas, Adv. Tech. Stand. Neurosurg. 1977,
4, 93-129
15.Briggs R.J., Fabinyi G., Kaye A.H. – Current
management of acustic neuromas: review of surgical
approaches and outcomes, J.Clin Neurosci 2000, 7:
521-526
16.Day J.D., Chen D.A., Arriaga M. – Translabyrinthine
approach for acoustic neuroma, Neurosurgery 2004, 54:
391-395
17.Iwai Y., Yamanaka K., Ishiguro T. – Surgery
combined with radiosurgery of large acoustic neuromas,
Surg. Neurol 2003, 59: 283-289; discussion: 289-291.
18.Koos W.T., Matula C., Lang J. – Color Atlas of
Microneurosurgery of Acustic Neurinomas, Thieme,
2002, 184-190.
19.Jung S., Kang S.S., Kim T.S. et al. – Current surgical
results of retrosigmoid approach in extralarge vestibular
schwannomas, Surg. Neurol 2000, 53: 370-377;
discussion 377-378
20.Mamikoglu B., Wiet R.J., Esquivel C.R. –
Translabyrinthine approach for the management of
large and giant vestibular schwannomas, Otol Neurotol
2002, 23: 224-227
21.Rhoton A.L. Jr. – The cerebellopontine angle and
posterior fossa cranial nerves by the retrosigmoid
approach, Neurosurgery 2000, 47: S93-S129
22.Ricardo R., Neto M.C. et al. - Treatment of large
and giant residual and recurrent vestibular
schwannomas, Skull Base 2007, 17(2): 109-117.
23.Seol H.J., Kim C.H.,Park CK et al. – Optimal extent
of resection in vestibular schwannoma surgery:
Relationship to recurrence and facial nerve preservation,
Neurol Med Chir (Tokyo) 2006, 46: 176-180;
discussion 180-181
24.Sluyter S., Graamans K,Tulleken C.A. et al. –
Analysis of the results obtained in 120 patients with
large acoustic neuromas results obtained in 120 patients
with large acoustic neuromas surgically treated via the
translabyrinthine-transtentorial approach, J. Neurosurg
2001, 94: 61-66
25.Brackmann D.E., Cullen R.D., Fischer L.M. – Facial
nerve function after translabyrinthine vestibular
schwannoma surgery. Am Otolaryngol Head Neck Surg
2007, 136: 773-777
26.Wandong S., Meng L., Xiangang L. et al. – Cystic
acoustic neuroma, J.Clin Neurosci 2005, 12: 253-255