Review Article Treatment of vestibular schwannomas. Why, when and how? E. Myrseth

Acta Neurochir (Wien) (2007) 149: 647–660
DOI 10.1007/s00701-007-1179-0
Printed in The Netherlands
Review Article
Treatment of vestibular schwannomas. Why, when and how?
E. Myrseth1 , P.-H. Pedersen1 , P. Møller2, and M. Lund-Johansen1
1
2
Department of Neurosurgery, Institute of Surgical Science, Haukeland University Hospital, University of Bergen, Bergen, Norway
Department of Otorhinolaryngology, Institute of Surgical Science, Haukeland University Hospital, University of Bergen, Bergen, Norway
Received July 13, 2006; accepted February 8, 2007; published online June 11, 2007
# Springer-Verlag 2007
Summary
Introduction
Sporadic vestibular schwannoma (VS) causes unilateral hearing loss, tinnitus, vertigo and unsteadiness. In
many cases, the tumour size may remain unchanged for
many years following diagnosis, which is typically made
by MRI. In the majority of cases the tumour is small,
leaving the clinician and patient with the options of either serial scanning or active treatment by gamma knife
radiosurgery (GKR) or microneurosurgery. Despite the
vast number of published treatment reports, comparative studies are few, and evidence is no better than class
III (May, 2006). The predominant clinical endpoints of
VS treatment include tumour control, facial nerve function and hearing preservation. Less focus has been put
on symptom relief and health-related quality of life
(QOL). It is uncertain if treating a small tumour leaves
the patient with a better chance of obtaining relief from
future hearing loss, vertigo or tinnitus than by observing it without treatment. Recent data indicate that QOL
is reduced in untreated VS patients, and may differ between patients who have been operated and patients
treated with GKR. In the present paper we review the
natural course and complaints of untreated VS patients,
and the treatment alternatives and results. Furthermore,
we review the literature concerning quality of life in patients with VS. Finally, we present our experience with
a management strategy applied to more than 300 cases
since 2001.
Vestibular schwannoma (VS) is a benign tumour arising from the Schwann cells in the vestibular component
of the statoacoustic nerve. The clinical incidence rate
is 10–15 per million=year [45, 76, 79, 129], but the
widespread use of MRI may lead to detection of more
tumours and an increase in incidence. Post-mortem dissections of temporal bones have shown the incidence of
small tumours to be much higher (0, 9%) possibly due
to selection bias [124, 130]. In an unselected autopsy
material of 298 temporal bones, no tumours were found
[21, 53].
The diagnosis of VS is usually made in adults with a
mean age ranging from 46 to 58 years in various series
[37, 74, 84, 110, 140]. VS is rarely found in teenagers,
and in these cases the tumour is often associated with
neurofibromatosis type 2 (NF-2).
Surgical treatment of VS has been one of the most
challenging procedures of neurosurgical practice for
more than a century. In 1894 Charles Ballance was probably the first surgeon to remove a VS, and in the surgical
report he described the difficulties of getting his index
finger around the tumour to achieve removal. The patient
was still alive twelve years later although with fifth and
seventh nerve palsies.
Concerned about the high morbidity and mortality
of early VS surgery, Cushing advocated intracapsular
tumour debulking. As standards of neurosurgery and
anaesthesiology improved, the concept of total tumour
removal was reintroduced by Dandy. Olivecrona and
Keywords: Vestibular schwannoma; microsurgery;
radiosurgery; quality of life.
648
subsequent neurosurgeons contributed to further neurosurgical development by addressing facial nerve preservation [36]. In the early 1960’s Bill House set a new
standard by introducing the operating microscope as a
valuable tool in VS surgery (for a review: see Ref. [72]).
In the early seventies Lars Leksell introduced Gamma
knife radiosurgery (GKR), and it was demonstrated that
GKR produced VS growth arrest or even involution.
Until December 2004, 28,306 VS patients had been
treated worldwide with GKR in 181 out of 213 reporting
centres (http:==www.elekta.com=).
Obvious as it may sound, it is nevertheless important
to remember that the treatment of any condition only can
be justified if the results of the treatment are better than
the natural course of the disease. There is a growing
debate on how VS can be best treated as it has become
clear that the tumour may remain unchanged in size for
years following diagnosis. A careful follow-up by MRI,
so-called ‘‘wait and scan’’, has therefore emerged as a
safe way of management in VS patients with small and
medium-sized tumours. Thus, newly diagnosed VS may
be managed by three principally different approaches.
The options are, ‘‘wait and scan’’, GKR or surgical resection, and the decision needs to be made whether
active treatment is indicated and which method of intervention is appropriate.
VS treatment has traditionally focused on tumour
control and preservation of cranial nerve function.
During recent years however, health related quality of
life (HRQOL) has emerged as a new issue in caretaking
of VS patients, addressing outcome factors other than
traditionally used endpoints. This research has given
information about the patient’s perception of the disease and treatment in relation to daily activities and
overall well-being.
In the present article we review relevant data which
may serve as a premise for future debate about VS treatment. This includes the clinical features and HRQOL in
VS patients managed by ‘‘wait and scan’’, GKR, or surgical resection. Finally, we discuss treatment algorithms for
VS patients and present our own management strategy.
E. Myrseth et al.
[10, 75, 80, 101, 107, 125, 134]. In a recent metaanalysis of VS growth, Yoshimoto found 22 retrospective and 4 prospective studies including 1340 patients
[144]. The proportion of tumours showing growth
varied considerably, from 15 to 85% in the different
reports (average 46%), and the mean growth rate
was 1.2 mm=year during a mean observation period of
38 months (range 6–64). Prospective studies, utilising
MRI serial imaging showed tumour growth rates lower
than the retrospective reports. Previous tumour growth
has been shown to represent a predictor for further
growth and eventual treatment [10, 24]. Intracanalicular
tumours seem to have lower growth rates than extracanalicular lesions [101, 134], and a younger age is
associated with more rapid tumour growth [74]. No
other reliable clinical or radiological predictors have
been found [101, 116, 123, 134]; for instance, the clinical growth index, as measured by the length of history divided by the maximum tumour diameter, did
not associate with growth. Using volume estimations
Mohyuddin et al. found a doubling time of 1.65 years
(range 20.9–46.3 months) in 50 VS patients [80].
Modern neuroimaging software programs allow onscreen volume estimation, which may improve future
studies of tumour growth [21].
Cochlear nerve symptoms
Unilateral hearing loss
The most common symptom of VS is reduced hearing
on the affected side (Table 1). When hearing is measured, it is necessary to quantify both pure tone audiometry and speech discrimination and the results obtained
are frequently classified using the Gardner-Robertson
scale [35]. On admission, about 95% of patients report
unilateral hearing impairment. Audiometry shows that
serviceable hearing (Gardner-Robertson grade A þ B
or class A1 þ A2 according to the Nordstadt ClassificaTable 1. Symptoms at onset and on admission in 301 patients with
vestibular schwannoma referred to the oto-neurosurgical group at
Haukeland University Hospital 2001–2005
Natural history
Tumour growth
The growth pattern of VS is highly variable, ranging
from spontaneous involution [66] to rapid growth [46].
The tumours usually grow slowly or remain unchanged
for years or growth may progress in a stepwise pattern
Reduced hearing
Tinnitus
Vertigo
Unsteadiness
%
Presenting
%
On admission
60.1
32.7
23.4
11.9
92.3
69.5
42.5
38.9
There is an increase in frequency of symptoms during the interval
between onset and admission.
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Treatment of vestibular schwannomas
Table 2. Hearing acuity on admission, both ears, according to the
Gardner-Robertson grading scheme in 298 out of 301 patients with
vestibular schwannoma
Grade
Tumour ear (%)
Contralateral ear(%)
A
B
C
D
22.3
26.3
14.2
37.2
90.9
7.3
1.1
0.7
tion) is present in about 50% of patients at diagnosis
(Table 2). According to large series, the mean duration
of gradual hearing loss before diagnosis is about 4 years
[74, 83]. Increased age associates significantly with hearing disability in untreated VS patients [74]. Typically,
hearing loss develops gradually, but an acute onset is
found in 12–22% of patients [74, 77, 93]. The possible
aetiological factors in these patients include a conduction block of the cochlear nerve or vascular compression
within the internal auditory canal (IAC) by a tumour
arising laterally. VS is rarely the cause of sudden deafness, as shown in the study by Saunders and co-workers,
who found only 13 cases of VS among 836 such patients
[119]. Patients suffering from sudden hearing loss seek
medical attention early, and have a shorter clinical history
than patients in whom the hearing loss is gradual [77, 93].
Tinnitus
Subjective tinnitus is a false perception of sound in
the absence of an acoustic stimulus [62]. In a prevalence
study, 2.6% of the responders reported severe tinnitus
[4]. Tinnitus associates with age, and is more common
in men than in women affecting approximately 11% of
men between age 64 and 75 years [62]. Tinnitus may be
present in a deaf ear, supporting the hypothesis of a
central pathophysiological origin. It is the second most
frequent symptom in VS patients, occurring in 63–75%
[74, 83, 84] of patients (Table 1) and in one third of
those affected the symptom is intermittent.
Tinnitus may be inversely proportional with tumour
size [74, 83], and is associated with depression [105].
The intensity of tinnitus may be quantified subjectively by self-reporting questionnaires, such as the Tinnitus
Impairment Index or a visual analogue scale (VAS) index [8, 68, 105].
Vestibular nerve symptoms
Vertigo
Vestibular nerve symptoms are found in 40–60% of
VS patients (Table 1) who may report a combination of
vertigo, dizziness and unsteadiness [54, 55, 74]. Dizziness is a common complaint, over time affecting up to
20–30% of individuals in the general population [87].
The incidence of true vestibular vertigo is approximately
5% and is distinguished from other types of dizziness by
a sensation of movement. It is a result of a mismatch
between the vestibular, visual, and somato-sensory systems. Since the functional ranges of these systems overlap, it permits partial compensation of their individual
deficiencies [16, 25]. Vertigo may be constant or intermittent, ‘‘nautical’’ (feeling like being on a ship), or
rotatory. Vertigo is associated with a significant reduction in HRQOL [29, 83, 142]. Vertigo is difficult to
quantify by objective means but self-reporting instruments such as an impairment index or a VAS scale
may be used [96].
Unsteadiness
About 40–50% of VS patients (Table 1), report unsteadiness at diagnosis [19, 83]. In the study by Matthies
and Samii, balance testing with eyes closed had the
highest rates of pathological findings in Class T1 (purely
intrameatal) and T4 (compressing the brain stem) tumours. Vestibular nerve signs were most pronounced
in Class T1, and cerebellar signs in Class T4 tumours
[74]. Sway motion can be measured by monitoring path
length and speed, or area of sway on a balance platform
[91]. Usually, values increase when the subject is tested
with eyes closed, and the ratio between results obtained
when testing with open and closed eyes, the so called
Romberg Index, may be calculated. A modern stabilometry platform, such as the Equi-Test+ system (Neurocom,
Clackamas, OR, USA), enables the investigator to discriminate vestibular from other causes of unsteadiness.
In addition, results are automatically compared with
built-in age-adjusted reference data. The path lengths
of VS patients are significantly longer than those of
normal subjects [83] especially when tested with eyes
closed [19]. Thus, the reduced vestibular function in VS
patients seems to be partially compensated by vision.
Other symptoms and clinical findings
Preoperative headache was recalled by one third of
operated VS patients in a large retrospective cohort
study [109, 110], and by 18% in a Finnish study [55].
In our prospective material, 42 out of 301 patients (14%)
complained of headache, in 17 patients this was reported
as a ‘‘fullness’’ or pressure in the ear region ipsilateral to
the tumour. Since headache is a very common symptom
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E. Myrseth et al.
Table 3. Other neurological findings in 301 patients with vestibular
schwannoma
Table 4. Tumour length along the pyramid in 301 patients with vestibular schwannoma
Impaired sensation in face
Impaired corneal reflex
Reduced taste
Pyramidal signs
Tumour size (mm)
11.0%
5.9%
5.2%
2.1%
and there are no studies comparing headache in VS
patients and a control group, it is uncertain whether
headache is associated with untreated VS.
A small proportion of newly diagnosed patients have
gait disturbances or ataxia caused by hydrocephalus or
compression of the brainstem and cerebellum. In addition, cranial nerve deficits, usually facial numbness and
occasionally diplopia and dysphagia may be found [74,
83], usually associated with large tumours (Table 3).
Canalicular
<10
11–20
21–30
>30
28.6%
16.3%
33.9%
12.9%
8.3%
angle (CPA), whereas tumour volumes were statistically
similar in patients with or without tinnitus or vertigo
[83]. In conclusion, many patients with useful hearing
may loose it during conservative management. The development of other complaints is less known.
Treatment
Symptom progression
Knowledge about the onset and development of complaints in VS patients is important when providing
advice on conservative management. In addition, this
knowledge is necessary to evaluate how treatment compares with the natural course of the tumour. Studies indicate that between one third [141] and one half [123] of
conservatively managed VS patients loose useful hearing over a period of three years. Thus patients managed
conservatively are definitely at risk of developing hearing loss. Our current knowledge about further symptom
development during ‘‘wait -and scan’’ is scarce, and
cannot be predicted to the individual patient. However,
progression from onset to diagnosis is recalled by patients in several studies [55, 74]. In the 301 patients
referred to us during the years 2001–2005, the median
duration of symptoms at diagnosis was 26 months (mean
51). The patients report an increase in frequency of
symptoms during the time interval from onset to diagnosis (Table 1). In a recent study of 199 untreated patients examined from 2001 out 2004 we found that the
average length of the history was similar in patients with
a combination of complaints and in patients presenting
with hearing loss alone [83]. It is reported that symptoms and tumour growth may progress independently
[134]. Although hearing impairment may associate with
tumour growth, it may not be an indicator of growth.
Tinnitus is reported to associate with small tumours, and
vestibular disturbance with intrameatal lesions as well as
large tumours compressing the brain stem [74]. In our
study, we found that unsteadiness associated with large
tumour size (more than 20 mm) in the cerebellopontine
Conservative management (‘‘wait and scan’’:
watchful waiting)
The concept of ‘‘wait and scan’’ is based on two
principles. First, a high proportion of the tumours do
not grow following diagnosis. Second, there is little evidence that treatment of a non-growing lesion is beneficial to the patient, but well documented that treatment,
in particular surgery, may cause additional complaints.
Therefore, in spite of increasing hearing loss in many
patients, conservative treatment may be a reasonable
option for patients with small to medium-sized tumours.
For the ‘‘wait and scan’’ strategy to be successful, patient compliance needs to be high and the follow up
program meticulous [116, 123]. This is illustrated in
two elderly patients who were referred to us during last
year. In both, the tumour had been known for several
years, but the follow up had been incomplete and both
developed gait difficulties due to brainstem compression
from a growing tumour. Such instances may be classified
as complications of the ‘‘wait and scan’’ approach.
Any progression of symptoms, such as hearing loss,
may be considered a failure of conservative treatment.
We believe that prospective studies need to be carried
out before patients can be advised on a statistical basis
about the relative merits of conservative management or
GKR in relation to hearing preservation.
Failure, defined as conversion from ‘‘wait and scan’’
to active treatment, is reported in 15–50% of patients in
various studies [24, 85, 123, 141]. The authors do not
report in detail why failure occurred, but tumour growth,
increasing symptoms and patients’ own preference were
probably the main reasons.
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Treatment of vestibular schwannomas
Surgery
VS surgery is technically challenging, and several
studies report on a gradual learning curve [17, 27, 52,
78, 136]. The translabyrinthine (TL) and the suboccipital=retrosigmoid (SO=RS) approaches can be used
for all tumour sizes, whereas the middle cranial fossa
(MCF) approach is useful only for removal of intracanalicular=small tumours. Hearing preservation can be
achieved only through the SO=RS and MCF approaches.
In many centres, VS patients are operated by an multidisciplinary team consisting of neurosurgeons and neurootologists [23, 84, 128], and the approach is chosen
based on criteria such as tumour size, tumour extension,
preoperative hearing level, and the surgeon’s experience.
Tumour control
In a review of 38 studies including a total of 5005 operated patients and 1475 treated with GKR, Yamakami
and co-workers found on average 96% total tumour
removal after microsurgery. The tumour recurrence rate
was 1.8%, which compared favourably with the recurrence rates following radiosurgery and tumour progression following conservative treatment [141]. Some
authors recommend subtotal tumour resection with subsequent GKR if a total resection puts the facial nerve
function at a high risk [50], a strategy which is also
advocated by our group. Due to inadequate access to
the lateral part of the internal auditory canal, the RS=SO
approach is claimed to be associated with a higher rate
of tumour recurrence than the TL approach [143], but
this has not been confirmed by comparative studies.
Facial nerve preservation
Second only to tumour removal, facial nerve preservation is the main goal of VS surgery. There are several
grading systems for the evaluation of facial nerve function, the most widely used being the House-Brackmann
scale [44] which provides a useful assessment tool. The
scale is subjective and inter-observer variation is documented [20, 103]. In addition, the study by Martin and
co-workers demonstrates that patients score their own
facial function as being a poorer grade than assessed
by the surgeons [73]. The size of the tumour and the
surgeon’s experience are the pre-operative predictors of
facial nerve outcome [11, 84, 114, 128]. In modern surgical practice per-operative facial nerve EMG is mandatory for anatomical and physiological monitoring,
and provides a reliable predictor of post-operative function [39, 49, 73, 86]. In our experience (using the Nim-
response system by Medtronic Xomed, Jacksonville, FL,
USA), we have found that a stimulus of 0.10–0.20 mA
generating normal signals indicates a good prognostic
sign for normal post-operative facial nerve function. If
the signals disappear in the medial portion of the nerve
permanent facial nerve palsy may be expected, even if
signals in the intracanalicular nerve segment are normal.
It has been claimed that because the facial nerve is
detected earlier during surgery it is more easily saved by
the TL than by the SO=RS approach [14, 133], but evidence for this is difficult to find in published literature,
as the functional results of both methods are within
the same range [3, 14, 23, 58, 84, 90, 115, 139, 143].
Patients with small tumours (including intrameatal) who
undergo the MCF approach may have a less favourable
facial nerve outcome than those operated by the SO=RS
or TL approaches [117], because the facial nerve is
located superior to the tumour which usually arises from
the inferior vestibular nerve in the internal auditory
canal. When drilling into the IAC from above, the surgeon’s view of the tumour is obstructed by the facial
nerve, which then becomes vulnerable to manipulation
during tumour resection.
Facial nerve transection is reported to occur in 2.5–
7% [23, 26, 114, 115] of surgical procedures. Immediate
intracranial nerve repair should be attempted in such
situations using a free graft from the great auricular or
the sural nerve.
Even in patients in whom the seventh nerve is anatomically and physiologically intact at closure, paresis increasing to complete palsy may develop during the early
post-operative period. Usually, nerve function improves
gradually over the next few months. In patients with postoperative facial nerve palsy, careful attention to the eye is
necessary to prevent infection and erosions of the cornea
caused by the impairment of eyelid closure. A tarsorraphy
or insertion of a gold weight or spring in the upper eyelid
will assist to protect the eye in these patients. When facial
nerve function does not recover, reconstructive surgery by
hypoglossal-facial or cross-face facial nerve anastomosis
(with nerve graft) are the alternative methods of treatment. Either method may establish facial nerve function
equivalent to House-Brackmann grade 3 in 61–79% of
the patients [26]. In long lasting facial nerve palsies reconstruction of facial symmetry is achieved through various face-lift cosmetic procedures.
Hearing preservation
Post-operative hearing preservation correlates strongly with tumour size. In 1986, Glasscock et al. stated that
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E. Myrseth et al.
preservation of hearing is unlikely when the tumour is
larger than 20 mm [38]. Yates et al. obtained no hearing
preservation in tumours 25 mm in the CPA, and Tonn
et al. had no hearing better than Gardner-Robertson
grade D in tumours larger than 30 mm in the CPA
[128, 143]. However, Samii and Matthies report good
post-operative hearing preservation for a proportion of
larger tumours [113].
Sanna and co-workers preserved hearing of class A or
B, i.e. functional hearing according to the AAO-HNS
grading scheme, in one third of patients operated by
the SO=RS approach (tumors <20 mm in the CPA) or
the MCF approach (tumour extending <5 mm into the
CPA). Reviewing published series where patients had
been operated through the SO=RS and MCF approaches
to preserve hearing, the authors pointed out that their
own complication rates of the latter were higher than
in patients operated by the TL approach. They concluded that attempts at hearing preservation should be
measured against the added risk of complications during
these procedures [117].
In comparison with historical data, the intraoperative
monitoring of cranial motor nerves and continuous recording of brain stem auditory evoked potentials (BAEP)
substantially improves the outcome of hearing function
[113, 128].
Similarly, studies reporting on post-operative vertigo
are few, and prospective studies with baseline registration of symptom severity by VAS or impairment index
questionnaires seem to be lacking. Lynn et al. assessed
post-operative dysequilibrium (imbalance, vertigo, and
light-headedness) in 237 VS patients operated by the
SO=RS approach [69]. In this series, 65% reported dysequilibrium between 3 months and 7 years after surgery
although with a mild impact on QOL. In the questionnaire
study by Wiegand et al. [138], 9% of patients reported
post-operative dysequilibrium as a severe handicap and
only 10% reported normal function. In the prospective
part of Levo et al.’s study [60], the sway velocity increased after the operation, and had not returned to preoperative values one year after surgery indicating an
increase of vestibular complaints. Multivariate analysis
revealed that the TL approach, rehabilitation, low age
and preserved facial nerve function predicted a good
outcome for postural stability. Patients operated by the
SO=RS approach and diagnosed with depression were at
risk of developing postoperative gait difficulties.
In conclusion, most of our knowledge about the effect
of VS surgery on tinnitus and vertigo derives from retrospective studies. Prospective studies with careful baseline recordings may provide further insight into these
problems.
Post-operative tinnitus, vertigo and unsteadiness
Postoperative headache
Only a few retrospective studies address the impact of
VS surgery on tinnitus. The study by Baguley et al. investigating pre-and post-operative tinnitus among 129
patients, indicates a favourable effect with TL tumour
removal [5]. The authors found that patients with no
tinnitus preoperatively were unlikely to develop it, and
mild or moderate tinnitus did usually remain unchanged,
or it became less intense whereas severe tinnitus improved in some patients. In a study addressing HRQOL
and the severity of tinnitus in a cohort of 51 operated VS
patients, post-operative tinnitus did not correlate with
tumour size or age [28]. The authors concluded that
post-operative tinnitus status was unpredictable, but, in
contrast to the results reported by Baguley et al., there
was a slight overall increase in patients reporting tinnitus
after surgery. Similar to our results [83], the authors
found that tinnitus did not interfere with HRQOL measured by the GBI questionnaire. Andersson and coworkers concluded that among 141 patients operated,
tinnitus was usually mild, and the likelihood of an improvement or worsening after surgery was low [2] and
similar results were found by others [11, 138].
In the study by Ryzenman and co-workers, 42% of
operated patients reported headache which was usually
mild. Women, especially of a younger age, were more
affected than men. During the first year after surgery, the
SO approach was associated with headache more than
the MCA and TL approaches, but this difference disappeared later. Tumour size did not associate with postoperative headache [110].
In our experience, postoperative headache is not a
major problem in VS patients. We do not specifically
address postoperative headache in our postoperative survey, but ask if there are any complaints other than the
cardinal symptoms. We routinely use craniotomy with
replacement of a free bone flap. Some studies indicate
that a standard craniectomy may be associated with significant postoperative headache, which may be reduced
with minimal bone removal during craniectomy [42, 51,
56, 118].
Other complications and mortality
Improvements of surgical technique and refinements
in anaesthesiology have reduced the mortality from more
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Treatment of vestibular schwannomas
than 25% in the hands of the early neurosurgical pioneers to 0–2% in the most recent series. In most patients
the cause of death is postoperative cardiopulmonary
complications [14, 23, 26, 41, 84, 112, 128, 141].
Apart from hearing loss and facial nerve dysfunction,
CSF leakage is the most frequent postoperative complication, occurring in 3–15% of cases [14, 26, 41, 59,
112, 128]. Usually the CSF leak resolves after temporary
lumbar drainage, leaving only a small number requiring
a secondary procedure. The frequency of postoperative
meningitis is about 1–3% [14, 26, 112, 128].
Cranial nerve or brainstem dysfunction is an infrequent postoperative problem, but may be found in patients with large tumors [15, 41, 59, 112].
Gamma knife radiosurgery (GKR)
Dose and tumour control
The Gamma knife consists of 201 60Cobalt sources
which are arranged in a hemisphere. Beams from the radioactive sources are directed through collimators and
converge to a common target. By individual plugging of
collimators or weighting the different 60Cobalt sources
the radiosurgeon can shape a three-dimensional radiation field similar to the lesion. Ideally, a single dose of
radiation sufficient to stop further growth may be administered to the lesion, while the dose delivered to adjacent
structures is much lower and therefore tolerable.
Usually, the dose to the tumour margin is the primary
radiophysical parameter during dose planning. Although
there is no consensus about the optimal dose, high rates
of tumour control with preservation of normal structures
can be achieved with a margin dose of 12 Gy. Maximum
doses of 20–25 Gy to the tumour centre are effective, but
there is a tendency nowadays to reduce the maximum
doses [32, 131, 132]. In order to obtain a margin dose of
12 Gy and a maximum dose within accepted limits, the
maximum tumour diameter should not exceed approximately 30 mm. However, a recent study shows beneficial
effect of low-dose GKR in a series of larger tumours, up
to 40 mm [47].
GKR has been used for more than three decades, and
worldwide an increasing number of VS patients receive
treatment by GKR instead of surgery. The aim of GKR
is tumour control, defined as either reduced or unchanged tumour volume. The majority of centres report
tumour control rates between 89 and 100%, but few
report observation periods longer than five years. Therefore, late regrowth may alter these figures, although a
recent long-term series showing a 10-year progression-
free survival of 92% indicates that recurrences develop
during the first three years [43]. The tumour growth rates
before GKR (or surgery) are usually unknown in reported series. Consequently, a proportion of treated tumours might have remained unchanged without any
treatment at all.
Effect on symptoms
Hearing preservation according to the GardnerRobertson scale (grade A–C) is reported in 50% to 89%
of patients undergoing GKR [31, 82, 94, 102, 116]. In
our own retrospective material, the frequency of hearing
loss was higher [84]. This may be due to variation in
radiation doses, but may as well be related to differences
in tumour volume and configuration. For instance, reports indicate that the risk of facial nerve dysfunction
may correspond to the length of the nerve irradiated,
tumour diameter and the dose delivered to the brainstem
[30, 34, 61].
In the literature covering GKR of VS, the main focus
of interest has been on tumour control and hearing preservation. The effect on tinnitus and vertigo is largely
unknown. More knowledge about this is of interest, as
reports indicate that in particular vertigo causes considerable discomfort and leads to impairment of quality of
life [83, 87, 96, 142].
Complications
The risk of facial nerve dysfunction has gradually
decreased from approximately 30% in early series, to
1–4% [31, 33, 82, 131]. Facial nerve function of grade
1 or 2 according to the House-Brackmann system may
therefore be expected in more than 96% of patients [67,
97, 131]. Similarly, trigeminal nerve function can be
preserved in 95–97%, and as the prescribed dose to the
tumour margin has been gradually lowered, post-irradiation trigeminal dysfunction is now rare [31, 32, 97].
Hydrocephalus may develop in 2–4% of VS patients
treated by GKR [84, 92], and it should be suspected in a
patient complaining of unsteadiness developing months
or years after treatment. The underlying mechanism is
uncertain, but it may be seen in medium-sized tumours,
and thus is unrelated to CSF obstruction. Since it may
also be seen in some untreated medium-sized tumours,
the contribution of GKR to hydrocephalus development
in VS patients is uncertain [106].
Post-GKR neoplasia, either as a second tumour or a
malignant change in the treated lesion has been reported
in a few cases [6, 40, 57, 63, 121, 122]. It is to be
654
expected that among the large number of patients treated
worldwide by GKR for benign lesions, some will develop a malignant brain tumour or a meningioma at a
later stage. Meningioma is the intracranial neoplasm
usually associated with previous irradiation [18, 111],
but an association with previous GKR has not been
documented.
Health-related quality of life in VS patients
Today, VS may be regarded as a chronic disease
which is only rarely life-threatening. Instead, the tumour
causes discomfort and leads to hearing loss. Therefore,
information about HRQOL during the course of treatment and conservative management is highly relevant
for this group of patients. Quality of life is measured
by validated generic or disease-specific questionnaires
and is increasingly being used as secondary and even
primary endpoints in clinical studies [13, 126, 127].
Generic questionnaires, which are applicable for patients
with many conditions, allow comparisons between patient groups and a reference population [64, 65, 135].
Some studies utilize questionnaires addressing symptoms
that are typically found in operated patients (see e.g. [1,
7, 48, 71, 95, 100, 102, 104, 109, 110, 116, 120, 133, 137]
but to our knowledge a validated disease-specific questionnaire has not been reported for VS. Instead, the generic questionnaires SF-36 [9, 12, 22, 70, 73, 83, 84] and
Glasgow Benefit Inventory (GBI) [83, 84, 88, 116] predominate. SF-36 can be used to distinguish among various stages of illness, and large scale reference data is
available in many countries for comparison with ageand sex-matched controls. The GBI questionnaire requests
the subject to compare QOL before and after a specific
event (for example the diagnosis or treatment of VS).
Three recent studies report on the QOL in untreated
VS patients [70, 83, 116]. In a study of patients managed
over a 15-year period, Sandoraam and co-workers demonstrated that patients managed conservatively reported
better QOL than patients receiving GKR or microsurgery [116]. MacAndie and Crowther demonstrated that
QOL in VS patients managed conservatively is similar
to other patients with vestibulo-cochlear complaints [70].
In our prospective study of 199 untreated VS patients we
investigated the impact of symptoms and tumour size on
QOL, which was below normative values across six out
of eight subscales of SF-36. We found that the overall
predictor of reduced QOL in untreated VS patients was
vertigo, which discriminated QOL across all SF-36 and
two out of three GBI subscales. When patients were
E. Myrseth et al.
grouped according to tumour size, tinnitus or reduced
hearing, less difference between groups was seen in the
reported QOL [83].
Most of our knowledge about QOL in VS patients
derives from retrospective studies of patients who received treatment (usually surgery) several years earlier.
The responders usually reported QOL lower than norms.
Somewhat surprisingly, poor facial nerve function associates only weakly with a reduction in QOL [12, 73,
84]. Only a few studies report on the QOL after GKR
[84, 116]. In our study, we found a slightly better QOL
outcome in the GKR than in the surgery group [84]. In
the study by Regis and co-workers comparing GKR and
surgery, the authors reported better QOL following GKR,
but the questionnaires used were not validated [102].
One may speculate that patients managed conservatively are at risk of the QOL being reduced if treatment
is necessary at a later stage because of a growing tumour. Two studies show that in patients who received
treatment because conservative treatment failed, QOL
was no worse than in patients who received treatment
initially [10, 116].
When studying treatment of any disease, prospective pre-treatment baseline data are valuable. To our
knowledge, studies comparing QOL before and after
treatment, and during the course of conservative management of VS seem to be lacking, and should be
undertaken.
Treatment decision and clinical management
Although the choice of treatment in VS patients is a
controversial issue, the treatment decision process has
been poorly investigated. A recent study of 139 VS patients managed at the Mayo Clinic showed that 23% of
the patients chose ‘‘watchful waiting’’, 36% underwent
GKR, and 40% underwent surgical tumour removal [98].
The authors found that the discipline of the attending
surgeon was a predictor for the choice of treatment, and
small tumour size and high age were predictors for conservative treatment.
As discussed before, the criteria for successful treatment of VS rely on tumour control rates and cranial
nerve preservation. Despite the large amount of studies
concerning treatment results, studies comparing treatment methods are based on no better than class 3
evidence [89], with one recent exception of class 2
evidence showing better results (facial nerve function,
complications, hearing preservation) for GKR than
for surgery [99]. Few centres, if any, can offer VS patients
655
Treatment of vestibular schwannomas
all available surgical methods and GKR. Clinicians recommend a treatment modality depending on what is
available at their institution, and will convey that to the
patients. It is our opinion that the alternatives ought to
be presented to the patients in an unbiased fashion, and
then discussed thoroughly with them [108]. Moreover,
patients are more knowledgeable about their disease and
treatment options than previously, and it is difficult to
conduct prospective randomised studies.
At the Haukeland University Hospital, Department
of Neurosurgery, the Gamma knife was established
in 1988 as the 5th centre worldwide. During the next
12 years, a total of 219 Norwegian VS patients were
treated, 103 with GKR, and 116 with microsurgery
[84]. Conservative treatment was used in a small number of selected patients [81]. GKR or microsurgery was
administered to tumours 30 mm, and microsurgery
(MS) to tumours >30 mm in the CPA. The choice of
method depended on patient preference and the medical condition. Patients with vertigo were predominantly
treated with surgery.
In 2001, we launched a new treatment algorithm dividing patients into four categories, based on CPA tumour size and tumour growth:
–
–
–
–
<5% risk of shunt-requiring hydrocephalus.
Complaints and QOL probably unchanged.
Very low risk of radiation-induced neoplasia.
No recovery period necessary.
MS:
– Total tumour resection in more than 90%.
– GKR of growing residual tumour is possible.
– Facial nerve function is dependent of tumour size;
80% H-B grade 1 or 2.
– Facial nerve reconstruction to HB grade 3 is possible.
– Total hearing loss except in some small tumours.
– Complaints and QOL probably unchanged.
– Mortality <1%.
– About 3 months to full recovery.
Until January 2006, 301 patients with VS referred to
our unit (Fig. 1) have signed a written consent and thus
been enrolled into a prospective research program on
1. <20 mm, single observation or no growth – Conservative management.
2. <20 mm and growth on serial scans – GKR or MS.
3. 20–25 mm, single observation – GKR or MS.
4. >25 mm – MS.
Conservative management involves outpatient consultation and contrast axial=coronal thin slice MRI at 6 and
12 months and then annually. In a few elderly category 2
patients with growing canalicular tumours we adopted a
‘‘wait and scan’’ approach. Although we established a
limit of 25 mm for recommending GKR, tumours up to
30 mm were treated in a few patients who had a strong
wish to avoid surgery. In the elderly, or medically ill
patients, a few even larger lesions have received GKR
treatment. These exceptions apart, the algorithm was
applicable to nearly all patients.
Patients in categories 2 and 3 received standardised
information given orally by one of the authors about
treatment alternatives as follows:
GKR:
– 90–95% tumour control.
– Later surgery possible, but probably more difficult
(in relation to dissection of VII nerve).
– Facial nerve palsy very rare.
– Gradual hearing loss may occur.
Fig. 1. Age distribution in 301 VS patients referred to the otoneurosurgical group. Mean: 57.0 years
Table 5. Primary and secondary treatment in 301 patients with vestibular schwannoma (see text for details)
Wait and scan
GKS
Microsurgery
Total
Primary management
Secondary management
165
81
55
301
20
3
2
25
Indicates that following initial decision to wait and scan, either GKR
or microsurgery were given to 20 (ten in each) patients.
656
E. Myrseth et al.
VS, approved by the regional Medical Ethical Committee. Out of 165 patients who were initially included into
the wait and scan program, MS and GKR each were
given later to two groups of ten patients. During the
period, 136 patients received primary treatment (55 with
MS and 81 by GKR (Table 5).
In order to investigate the choice of treatment in
patients with newly diagnosed VS, we conducted a prospective study during the years 2001 out 2005. Patients
with tumours 25 mm or less to be treated were presented
with the options of either choosing treatment themselves
or undergoing randomisation. Information was presented
about the treatment alternatives as above. If medical conditions or age (70-year limit) contraindicated surgery,
only GKR was used, and these patients were excluded.
Data collection and analysis was carried out according
to a pre-defined protocol. Out of 71 patients who fulfilled the inclusion criteria, only seven patients accepted
randomisation. Altogether 64 consenting patients with
tumours 25 mm or less did not accept randomisation
but fulfilled the criteria for a free choice between GKR
and surgery. Among the data collected in the period
2001–2006, we analysed if one particular treatment
was preferred, or if any of the following, i.e., age, sex,
tumour size or hearing function (Gardner–Robertson
A þ B grouped together against C þ D) were different
between the 2 groups.
Altogether 45 patients chose GKR and 19 surgery
(P< 0.001), (Table 6). The groups did not differ significantly in the distribution of any of the four parameters
tested.
Several conclusions may be drawn from the above
study. First, since only seven patients accepted randomisation, class I evidence for GKR versus MS for VS will
require a randomised multicentre study. However, if
given the above information, patients may decide on
the treatment choice themselves. Although no prospective data collection was used to investigate this, we
observed that many patients needed more than one consultation with the attending doctor. Frequently, the first
consultation, which was carried out in an outpatient setTable 6. Characteristics and individual treatment choice of 64 patients
with VS
N
Male=female
Age
Tumour size (mm)
Gardner Robertson A þ B
Gamma knife
Surgery
P
45
23=22
53.9 (9.2 SD)
15.9 (5.0 SD)
47.1%
19
7=12
50.3 (12.7 SD)
17.3 (5.9 SD)
48.6%
0.001
n.s
n.s
n.s
n.s
ting, was followed by a telephone consultation one to
two weeks later. The second important finding in this
study is that GKR was preferred by a significantly higher
proportion of patients than those choosing surgery. This
may not be surprising, since the complication rate is
lower, no recovery period is necessary, and the risk of
therapy failure is low and within the same range for both
alternatives. We think it is necessary to inform patients
about both options of treatment, and let the patient decide, even if their preferred treatment is not an option
available in the same institution.
Conclusion
Vestibular schwannoma is a benign tumour which
usually either grows slowly or remains unchanged for
many years. The complaints are usually mild, and may
persist despite treatment. As the average size of newly
diagnosed tumours is less than 20 mm, treatment is only
rarely a life-saving procedure. Instead, treatment aims at
preventing morbidity caused by growth. Tumour control
rate, facial nerve function and hearing preservation are
the traditional endpoints of VS treatment, but vertigo,
unsteadiness, tinnitus and health-related quality of life
should be reported as well. There is definitely a need for
prospective comparative studies.
To be justified, VS treatment should lead to an outcome better than the natural course. When treatment is
indicated, surgery and Gamma Knife Radiosurgery are
alternatives. Although prospective comparative studies
are lacking, both methods have a cure rate of 90–98%
and patients should be informed about each alternative.
The original work presented here indicates that given
balanced, unbiased information, a majority of patients
prefer GKR if treatment is indicated. Consequently, the
questions ‘‘why, when and how’’ need to be discussed
with the patient before treatment is undertaken.
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tumours: hearing preservation. It is the result of improved microsurgery
that the goalposts have moved, allowing hearing preservation to be the
relevant factor for those who present sufficiently early. Paradoxically,
surgery is now undermined by the outcome of less invasive methods.
As most patients present with progressive hearing loss, despite the
lack of high level statistical proof they suspect what the future holds
without any intervention. At the same time they are increasingly aware
of the radiosurgical hearing preservation in large series [1, 2]. Hearing
loss after the ‘‘watch and wait’’ policy (just as after microsurgery or
radiosurgery) should be considered failure of management. Contrary to
quality of life data presented in this paper this single issue often clinches
the decision for many younger patients.
As the authors quite rightly point out, the choice of treatment is often
determined by the local availability of techniques with the alternatives
only vaguely mentioned to the patient. In this day and age it is quite possible for patients to be referred to another centre (specialising in microsurgery of the skull base or radiosurgery) if necessary. In fact, it should
be considered negligent if such alternatives are not truly provided. The
study presented here is commendable for its detached and honest standardised patient information which makes their results credible.
References
1. Regis J, Pellet W, Delsanti C, Dufour H, Roche PH, Thomassin
JM, Zanaret M, Peragut JC (2002) Functional outcome after gamma
knife surgery or microsurgery for vestibular schwannomas. J Neurosurg 97(5): 1091–1100
2. Rowe JG, Radatz MW, Walton L, Hampshire A, Seaman S,
Kemeny AA (2003) Gamma knife stereotactic radiosurgery for
unilateral acoustic neuromas. J Neurol Neurosurg Psychiatry 74(11):
1536–1542
Andras Kemeny
Sheffield
In this comprehensive review, the authors discuss the spectrum of
clinical presentation for a vestibular schwannoma and the various management options. They provide a good overview of what is known
regarding the natural history for such tumors if untreated. We agree that
this is a reasonable choice for older patients, who may not require any
tumor care during their remaining life. However, for younger patients,
there is a growing experience showing that tumor irradiation may lead
to better cranial nerve outcomes (i.e., hearing preservation) than observation. Thus observation may not be a wise choice in a young patient.
As for the controversy over resection versus radiosurgery, there are
now four matched cohort studies, including one performed by these
authors, showing similar or better outcomes in the Gamma knife radiosurgery patients. Although a randomized trial is not likely to be conducted, there is sound level two evidence supporting radiosurgery for
smaller volume tumors. In addition, the long-term data for radiosurgery
continues to be published [1]. We need such information for after all
forms of management.
Reference
Comments
The authors present an overview, much like a didactic chapter, for
the presentation and management of acoustic neuromas on the apropos
of their study. As they allude to in the paper, the history of management
of these tumours progressed from trying to save the patients’ life, to
keeping the neurological deficit to the minimum. Initially surgeons were
happy to just minimize the deficit to the cerebellum and brainstem, later
attempting and achieving increasing functional facial nerve preservation, progressing to the current aim for many small and medium-sized
1. Kondziolka D, Nathoo N, Flickinger JC, Niranjan A, Maitz AH,
Lunsford LD (2003) Long-term results after radiosurgery for benign
intracranial tumors. Neurosurgery 53: 815–822
Douglas Kondziolka
Pittsburgh
Correspondence: Dr. Erling Myrseth, Department of Neurosurgery,
Institute of Surgical Science, Haukeland University Hospital, University
of Bergen, N-5021 Bergen, Norway. e-mail: [email protected]
`