Factors affecting surgical outcome of cerebellopontine angle tumors
Ramy Abdelmonem, Nasser Mosaad MD, Hossam Maaty MD, Walid Badawy MD&
Alaa Farag MD
Department of Neurosurgery, Banha University
ABSTRACT
Background: Cerebellopontine angle (CPA) tumors constitute 10% of intracranial masses. CPA tumors
still present a difficult surgical challenge especially when they are large in size and involve
neurovascular structures. Objective: The aim of the study is to study the outcome of microsurgical
resection and factors affecting its resectability. Patients and Methods: In this prospective study, twenty
cases were included, twelve cases were vestibular schwannoma (VS), four cases were epidermoied, three
cases were meningioma and one case was medulloblastoma. In each case diagnosis was made clinically
and confirmed radiologically and histo-pathologically. Results: Between March 2012 and June 2014,
twenty patients with different CPA tumors were operated, the patients were thirteen female and seven
male. In eight cases total resection was achieved, and subtotal resection in twelve cases. In this study
mortality was recorded in one case. Conclusion: The surgical treatment of CPA tumors still represents a
challenge for neurosurgeons. Surgery for CPA tumors poses a variety of problems reflecting the complex
anatomy of the CPA region.
Key words: CPA, Vestibular schwannoma, Meningioma, Epidermoid, Retrosigmoid approach.
INTRODUCTION
CPA tumors comprise about 8–10% of
all intracranial neoplasms with vestibular
schwannoma
representing
(80:90%),
meningioma(3:7%), epidermoied (2:4%), Other
cranial nerve (cranial nerves V, VII, IX, X, XI)
schwannoma(1:4%), arachnoied cyst (1:2%) and
others as hemangioma, lipoma, chondroma,
chondrosarcoma, chordoma, metastases which
represent a small group (12).
NF2 patients often present a challenge
because of the increased incidence of bilateral
Vestibular schwannoma (VS) and the younger
age at which tumors develop. NF2 tumors
present a more complex approach because
attempts at maintaining serviceable hearing need
to take into account future growth (10).
Lesions within the CPA may present
with symptoms and signs of cranial nerve
dysfunction: unilateral hearing loss, tinnitus,
disequilibrium, vertigo; diplopia due to
abducens palsy; facial paraesthesia, anaesthesia,
*Corresponding author:
Ramy Abdelmonem
Neurosurgery Department Banha University, Egypt
Email:ramyteama82@gmail.com,Tel:+2/0111442437
3
1
dysphonia, dysarthria and dysphagia. Other
manifestations as cerebellar and brainstem
compression, raised intracranial pressure or pain
localized to the ear/mastoid regions, or
sometimes non-localizing headache may also be
present (7).
Contrast-enhanced
MRI
is
the
investigation of choice in patients with
symptoms and/or signs of CPA disease. Thin
sections in axial and coronal planes can detect
tumors as small as 2 mm in diameter. CT scans
provide complementary information on bone
anatomy. Otoneurological investigations as pure
tone audiometry are indicated when a patient
presents with symptoms suggestive of
vestibulocochlear nerve dysfunction (7).
Treatment of CPA tumors comprises
clinical and radiological observation, surgery,
and radiosurgery (13). When considering the
management of a patient with CPA tumor,
several factors preside. The size of the tumor is
of paramount importance, large tumors may
cause the life-threatening complications of
symptomatic hydrocephalus, and direct mass
effect. If mass symptoms are evident, early
surgery to remove the tumor should be
considered (7).
CPA tumors may be operated upon
using the retrosigmoid approach, the middle
fossa approach, and the translabyrinthine
approach. The retrosigmoid approach is the most
frequently used and allows an extrapetrosal
approach to the CPA that avoids destroying or
opening the labyrinth (4).
The aim of this study is to evaluate
different factors that affect the surgical outcome
of CPA tumors.
Patients and methods
Between March 2012 to June 2014, a
prospective study conducted upon 20 patients of
CPA tumors treated in the Neurosurgery
departments Banha University and Gawish
medical center – Egypt.
In this study, the patients were subjected
to
thorough
neurological
examination.
Computerized tomography as well as Magnetic
resonance imaging with and without contrast
enhancement were done for all cases
preoperatively. Pure tone audiogram was done
for all patients preoperatively. All these patients
were submitted to surgery. Postoperative CT and
MRI were done as a routine. Facial nerve
function was graded according to HouseBrackmann facial nerve grading scale. Hearing
was graded according to Gardner-Robertson
grading system.
Tumors were classified according to size
into small (less than 2.5 cm in maximum
dimension) and large (more than 2.5 cm in
maximum dimension).
Operative management:
Surgery was performed with general
anaesthesia, with the aid of an operating
microscope and microsurgical instruments in all
cases, nerve monitoring was used in 8 cases and
CUSA was used in 10 cases.
Retrosigmoid suboccipital approach was
the corridor of surgery. Nine of patients were
operated in the semisitting position, the other
nine patients were operated in supine position
with head tilt with shoulder role under the
ipsilateral shoulder and two cases were operated
in the parck pench position.
2
The aim of surgery was total tumor
removal but the limits against that was the
attachment of tumor to different neurovascular
structures in the CPA. After careful planned
craniotomy and opening of the dura, the cisterna
magna was opened to provide relaxation and two
flexible arms were placed. After peeling away
the arachnoid, the posterior tumor is coagulated
with bipolar cautery and opened with
microscissors and specimens are sent for
pathologic study. The internal portion of the
tumor is then decompressed using an ultrasonic
aspirator in 10 cases. Hemostasis is obtained,
and the tumor capsule is dissected from the
arachnoid plane and rolled inward. This may be
repeated several times depending on tumor size.
The dura over the canal is coagulated and
flapped medially. Using a high-speed diamond
drill, the canal is opened. The dura of the canal
is then opened sharply. Piecemeal debulking is
started with microscissors and tumor forceps.
Pieces of muscle are fixed over the drilled
region to occlude the opened air cells in the
region of the IAC. Opened mastoid air cells are
carefully occluded with pieces of muscle and
bone wax. After meticulous hemostasis, the
dural opening is closed in a watertight fashion.
Extent of tumor removal was classified
as ‘total’ (all of the tumor material was removed
without any remnants in post-operative
contrasted MRI brain) or ‘Subtotal’ (a thin layer
of tumor attached to one or more nerves was
intentionally left behind or residual disease,
which is less than 50% of the initial tumor).
Follow up of cases was conducted in the
outpatient clinic. Evaluation was done both
clinically and radiologically with the help of CT
and MRI with contrast to detect any tumor
residual.
Stereotactic radiosurgery was used in
cases with residual more than 1 cm diameter or
in patients with residual tumor treated
conservatively and showed increase in size
during follow up.
RESULS
Twenty patients with CPA tumors were
operated. The patients were 13 female and 7
male. The mean age was 39.6 years.
The most common initial symptom
included is diminution of hearing and tinnitus
(90%) followed by vertigo or dizziness (75%).
Seven patients (35%) had trigeminal nerve
dysfunction, (30%) had preoperative facial
paresis (table1).
TABLE (1): Preoperative clinical data of the studied patients:
Variable
Hearing diminution
Tinnitus
Vertigo
Facial nerve
Trigeminal N. affection
Headache
Other cranial N affection
Other manifestations
Forms of other manifestations
(N=8)
Yes
Yes
Yes
Normal
Mild facial palsy
Yes
Yes
Yes
Yes
Skin pigmentations
+ICT
gait disturbance
Monoparesis
hemiparesis,
The tumors showed different patterns of
contrast enhancement in MRI T1WI with
Gadolinium (table 2). Enhancement was
homogenous in 5 patients heterogeneous in 10
patients and no enhancement was present in 5
patients. Seven patients (35%) had cystic
tumors.
TABLE (2)- Radiological findings of studied patients:
Variable
Enhancement
No
Heterogeneous
Homogenous
Size
< 2.5 cm
> 2.5 cm
Hydrocephalus
Absent
Present
Brain
stem Absent
compression
Present
Associated lesions
Absent
Present
Surgical results:
In 8 patients tumors were totally
removed (40%) subtotal removal was performed
in the other 12 cases (60%). In this study there
was one case of mortality (5%) because of SAH
and large intracerebellar hematoma. Another
case had small intracerebellar hematoma that
resolved spontaneously. Two cases (10%)
3
No. (N=20)
18
18
15
14
6
7
16
3
8
2
2
2
1
1
% (100%)
90.0
90.0
75.0
70.0
30.0
35.0
80.0
15.0
40.0
10.0
10.0
10.0
5
5
Tumors were larger than 2.5 cm in 15 patients
(75%) and smaller than 2.5 cm in 5 patients
(25%). Ventriculomegally was present in 6
patients (30%). Brainstem compression was
present in 14 patients (70%). Associated
multiple lesions were present in 5 patients (25%)
No. (N=20)
5
10
5
5
15
14
6
6
14
15
5
% (100%)
25.0
50.0
25.0
25.0
75.0
70.0
30.0
30.0
70.0
75.0
25.0
developed CSF leake, one case (5%) developed
transient hemiparesis and one case (5%)
developed hydrocephalus.
TABLE (3) - postoperative complications other
than cranial nerve affection:
Complication
CSF ottorrhea
HCP
Hematoma
SAH
Hemiparesis
Recurrence
Frequency
Percent (%)
2
1
2
1
1
2
10
5.0
10
5.0
5.0
10.0
In 9 cases (45%), histological
characteristics were consistent with VS World
Health Organization tumor Grade I. Three cases
(15%) had cystic VS. Four cases (20%) had
epidermoied tumor. Three cases (15%) had
meningioma two of them were cellular type GI
and one was psamomatous type GII. There was
also one case of medulloblastoma GII.
Facial Nerve:
Facial nerve was anatomically preserved
in 19 patients but was not anatomically
preserved in one case of large vestibular
schwannoma.
In an overall of 13 cases there was more
deterioration of facial function ranged from
moderate (GIII) to (GIV or V) facial palsy.
Follow up of these patients was performed both
clinically
and
by
facial
nerve
electrophysiological studies (NCV and EMG)
together
with
intense
physiotherapy.
Improvement of facial functions within one year
follow up occur in all cases except the case in
which the facial nerve was not anatomically
preserved. The final results are as follow: no
facial palsy in 9 cases (45%), mild facial palsy
(GII) in 4 cases (20%), moderate (GIII) in 3
cases (15%), severe (G IV, V) in 2 patients
(10%) and total loss in one case (5%).
There is a significant correlation
between postop facial palsy and tumors larger
than 2.5 cm with p value of 0.028 and also with
preoperative facial palsy with p value of 0.012.
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TABLE (4)- relationship between tumor size
and postop facial palsy:
size
Facial functions
Normal(I)
Mild(II)
Moderate(III)
Severe(IV,V)
Total
paralysis(VI)
>2.5
<2.5
9 (45%)
4 (20%)
1 (5%)
0 (0%)
0 (0%)
0 (0%)
0 (0%)
2 (10%)
2 (10%)
1 (5%)
Hearing Preservation:
Hearing preservation was attempted in
all cases. In 75% of patients the anatomical
integrity of the cochlear nerve was preserved.
The rate of cochlear nerve preservation was
higher among cases with tumors less than 2.5
cm. preoperatively; the cochlear nerve was the
most frequently affected cranial nerve. Four
patients (20%) had preoperative complete
hearing loss (Gardner-Robertson grade V). Of
the other 16 patients, three patients (15%) had
non-serviceable
hearing
loss
(GardnerRobertson grade III or IV); however in 13
patients (65%), preoperative hearing was
serviceable. Postoperatively, seven cases (35%)
were deteriorated to severe or total hearing loss.
Table (5)-postoperative hearing level:
Grade
I
II
III
IV
V
total
Frequency
1
8
2
3
6
20
Percent (%)
5
60
10
5
20
100
There is a significant correlation
between postop facial palsy and tumors larger
than 2.5 cm with p value of 0.033 and also with
preoperative facial palsy with p value of 0.025.
Fig(1):MRI brain T1WI with Gadolinium, upper left image, preoperative right VS, upper right image,
3 months postoperative shows residual minimal intracanalicular enhancement, lower image, 24 months
postoperative shows no increase in size of residual intracanalicular enhancement.
Fig (2): left image show axial T2 of left CPA epidermoied. Right image show Post-operative CT after
subtotal removal of the same patient.
5
DISCUSSION
The CPA is one of the difficult
intracranial locations located between the
superior
and
inferior
limbs
of
the
cerebellopontine fissure formed by the petrosal
cerebellar surface folding around the pons and
middle cerebellar peduncle. The superior limb
extends above the trigeminal nerve and the
inferior limb passes below the flocculus and the
nerves that pass to the jugular foramen (IX, X,
XI) (8).
In this study the most common clinical
manifestation was cranial nerve dysfunction that
was of gradual onset and progressive course in
the form of: hearing diminution (90%), tinnitus
(90%), dysequilibrium and vertigo (10%), Facial
weakness
(30%),
Facial
paraesthesia,
anaesthesia or pain (35%). large lesions lead to
dysphonia, dysarthria and dysphagia due to
involvement of the IX and X cranial nerves
(15%). Manifestations of cerebellar and/or
brainstem compression was present in 10% of
cases. Raised intracranial pressure secondary to
associated hydrocephalus, or occasionally to the
mass of the lesion itself was present in 10% of
cases. Headache was present in 30% of cases.
Those results were similar to those of
other series where vestibulocochlear, facial and
trigeminal nerves dysfunction were the most
common manifestations with larger tumors
causing brainstem compression and increased
intracranial tension. Greenberg pointed that the
characteristic onset of these tumors usually
begins with sensorineural hearing diminution
(98%), tinnitus (85%) and balance difficulties.
When the tumor grows more it causes facial
numbness (30%) and facial weakness (10%).
Nausea and vomiting was present in (10%) of
cases and headache in (32%) of cases (1). In a
series published by Sami et al., including 200
patients hearing affection was the most common
manifestation affecting 94% of cases, tinnitus in
90% of cases, vertigo was present in 49% of
cases, facial weakness in 10% of cases, facial
paraesthesia in 30% of cases while the lower
cranial nerve affection was present in 1.5% of
cases (9). In a series published by Marc et al.,
including 115 patients the most common
6
presenting symptom was hearing diminution
affecting 58% of cases followed by facial
numbness and facial pain affecting 50% of
cases, lower cranial nerve affection was present
in 12% of cases and facial palsy was present in
7% of cases. Headache was the second most
common complaint in this series affecting 52%
of cases (4).
MRI is the imaging modality of choice
giving three plane image of the tumor, extension
into the internal auditory canal, intratumoral
changes, brainstem compression, state of
surrounding vasculature and provisional
diagnosis of tumor type. . CT also shows
dilatation of the internal auditory canal, anatomy
of the bony labyrinth. in addition to hyperostosis
of petrous temporal bone in cases of
meningioma.
In this series tumors were larger than 2.5
cm in 15 patients (75%) reaching 5cm and
smaller than 2.5 cm in 5 patients (25%) reaching
2cm. Ventriculomegally was present in 6
patients (30%). In the series of Sami et al.,
including 200 cases diameter of the tumor was
larger than 2.5 cm in (60%) of cases,
hydrocephalus was present in (10%) of cases
and brainstem compression was present in 30%
of cases (9). In the series of Marc et al., The
median tumor diameter was 30 mm (4).
The most common position used was the
supine position with head tilt and shoulder roll
under the ipsilateral shoulder (45%) and the
semisitting position (45%). Parck pench position
was used in two cases (10%).
Surgical approach used in this work is
the suboccipital retrosigmoid approach. Which
is the most favorable approach for
neurosurgeons as it is familiar to them and allow
preservation of hearing and allows complete
access to the CPA (3, 4, 9). In the series of Sami
et al., including 200 cases suboccipital
retrosigmoid approach was used in all cases (9).
In the series of Peter et al., including 526 cases
retrosigmoid approach was used in 75% of cases
and translabyrinthine approach was used in 25%
of cases (7).
Subtotal removal was performed in 12
(60%) cases while total removal was achieved in
8 cases (40%). Complete surgical eradication of
the tumor tissue was not reachable in twelve
cases (12) because of: (a) complex relationship
of the tumor with the structures of the CPA and
brainstem (difficult accessibility), (b) its firm
adherence to surrounding structures and its large
size in some cases (problematic resectability).
In this series vestibular schwannoma
was totally removed in 5 cases (42%) and
subtotal removal in 7 cases (58%) to preserve
the functional integrity of the facial nerve. Better
results were found in the series of Sami et al.,
including 200 cases of VS in which total
removal was achieved in 98% of cases and only
2% of cases (4 cases) were removed subtotally
to preserve the functional integrity of the facial
nerve (9). In the series of Michelle et al.,
including 60 cases of VS total removal was
achieved in 90% of cases (54 cases) and subtotal
removal was performed in 10% of cases
(6cases)(5).
In this series meningioma was totally
removed in one case and was removed subtotally
in 2 cases was due to large size of the lesion
(diameter more than 4 cm) and the attachment of
the lesion to the posterior cavernous sinus. close
results were found in the series of Marc et al.,
including 115 cases, they removed meningioma
totally in 45% of cases (52 cases) and subtotal
removal was achieved in 55% of cases (63
cases) due to large tumor size, medial tumor
extension and its vascular attachment (4). In the
series of Nakamura et al., including 77 cases
total removal was achieved in 68 cases (89% of
cases) and subtotal removal was performed in 9
cases (11% of cases) (6).
In this series there were 4 cases of
epidermoied tumor total removal was achieved
in 2 cases (50%) and subtotal removal was
performed in 2 cases (50%). In the series of Han
et al., including 20 cases of epidermoied tumor
total removal was achieved in 14 cases (70%)
and subtotal removal was performed in 6 cases
(30%) (2). But in the series of Siegarie et al.,
including 43 cases of epidermoied tumor total
removal of the tumor occur in all cases (100%)
7
even in cases with extension into the middle
cranial fossa (11).
Hearing Preservation:
Some authors have stated that hearing
preservation surgery should be undertaken only
in carefully selected cases, depending on tumor
size and preoperative hearing level. The most
significant
factors
predicting
hearing
preservation are tumor size and extension and
preoperative hearing level. Predominantly,
caudal tumor extension leads to a greater degree
of cochlear nerve stretching and is related to a
poorer hearing outcome. Hearing was affected
preoperatively in about 18 cases (90%) of cases
of which 7 cases (35%) were deteriorated to
severe or total hearing loss post-operative. in the
series of Sami et al., including 200 cases
according to which serviceable hearing was
present in 51% of cases (9). In the series of Peter
et al., including 526 cases 4.8% of patients had
normal post-operative hearing and 8% had
serviceable hearing. A further 18% had some
hearing at post-operative period; the success of
hearing preservation is dependent upon tumor
size, with dismal results in patients with large
tumors. (7).
There was significant correlation
between hearing loss and tumors larger than 2.5
cm; also there is a positive correlation with the
preoperative hearing deficit. This is compatible
with the results of (2, 4, 5, 6, 7, 9).
Facial nerve
Anatomical preservation of the facial
nerve is the rule today and is achieved in 93 to
99% of cases. Good postoperative facial nerve
function (House–Brackmann Grades I and II) is
achieved in 52 to 93% of cases. The rates of
preserving good facial nerve function are similar
among the middle fossa, translabyrinthine, and
retrosigmoid approaches. Tumor size is the main
predictor of facial nerve preservation. In cases of
VSs larger than 4 cm, good function is achieved
in 38 to 58 %( 9).
In this series the final results at 1 year
follow up was as follow, no facial palsy in 9
cases (45%), mild facial palsy (GII) in 4 cases
(20%), moderate (GIII) in 3 cases (15%), severe
(G IV, V) in 2 patients (10%) and total loss in
one case (5%). Better results are found in other
series for example, in the series of Sami et al.,
including 200 cases in which moderate to severe
facial palsy affects 19% of cases with no cases
of total facial palsy (38 cases)(9). In the series of
Peter et al., including 526 cases the facial nerve
was anatomically intact following tumor
resection in 94% of cases (7).
There was significant correlation
between postoperative facial palsy and tumors
larger than 2.5 cm; also there is a positive
correlation with the preoperative facial palsy.
This is compatible with the results of (2, 4, 5, 6,
7, 9).
Other postoperative complications
In this study there was one case of
mortality (5%) because of SAH and large
intracerebellar hematoma. Another case had
small intracerebellar hematoma that resolved
spontaneously. Two cases (10%) developed CSF
leake, one case (5%) developed transient
hemiparesis and one case (5%) developed
hydrocephalus.
The most common complication in this
series was CSF leakage that occurred in two
cases requiring lumbar drain in one case that
was inserted for one week followed by removal
and conservative treatment. In the series of Sami
et al., including 200 cases postoperative CSF
leakage occurred in two cases (9). In the series
of Peter et al., including 526 cases postoperative
CSF leakage CSF leakage occurred in 5% of
patients, although a subset of 188 consecutive
patients were operated upon with a leak rate of
only 1.6% (6).
Recurrence occurred in two cases (10%)
one VS and one epidermoied which may be
related to increased percentage of subtotal
removal in this series. Better results are found in
the series of Sami et al., including 200 cases in
which there was only one case of recurrence of
VS (.5%) (9). In the series of Marc et al.,
including 115 case recurrences occurred in only
one case (4). The mortality of surgery for CPA
tumors has reduced dramatically over the course
8
of this century. In this series one case (5%) died
in the fourth postoperative day after the
occurrence of large cerebellar hematoma and
massive subarachnoid hemorrhage which is the
most common cause of death in most series
(4,7,9).
CONCLUSION
The surgical decision for these tumors
should depend primarily on the clinical findings
of the patient and radiological findings of the
tumor. Debate persists regarding the optimal
treatment of CPA tumors but generally surgical
treatment is used in case of large tumors
(<1.5cm) and in case of mass effect on the brain
stem and other cranial nerves.
The goal in treating CPA tumors should
be total removal in one stage and preservation of
neurological functions, because these factors
determine the quality of life for patients. This
goal can be achieved safely and successfully by
using the retrosigmoid approach.
The most important factor that affects
the surgical outcome of these tumors is the size
of tumor. Large tumors are associated with
worse postoperative outcome concerning facial
dysfunction, hearing loss and complications.
Acknowledgement
I like to thank Prof. Dr. Hossam Maaty
for his kind support and real help during this
study.
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