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Facial Function in Hearing Preservation Acoustic Neuroma Surgery
Moisés A. Arriaga, MD;
Douglas A. Chen, MD
Arch Otolaryngol Head Neck Surg. 2001;127:543-546.
ABSTRACT
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Objective To determine if facial function is worse after hearing preservation
acoustic neuroma surgery (retrosigmoid and middle fossa) than in translabyrinthine
surgery.
Design Retrospective medical record review.
Setting Private neuro-otology subspecialty practice of patients operated on
in a tertiary care hospital.
Patients This study evaluated 315 consecutive acoustic neuroma surgical procedures
between April 1989 and July 1998. A total of 209 translabyrinthine procedures
and 106 hearing preservation surgical procedures were performed. The hearing
preservation procedures were equally divided between retrosigmoid (n = 48)
and middle fossa (n = 58) procedures.
Methods Medical records were reviewed and tabulated for tumor size, surgical
approach, and House-Brackmann facial function grade at short-, intermediate-,
and long-term intervals.
Results Postoperative facial function in hearing preservation surgical procedures
at short- and long-term follow-up was not worse than facial function after
translabyrinthine surgical procedures in comparably sized tumors.
Conclusion Concern about postoperative facial function should not be the deciding
factor in selecting hearing preservation vs nonhearing preservation acoustic
neuroma surgery.
INTRODUCTION
THE OVERALL objectives of acoustic tumor (vestibular schwannoma) surgery
are straightforward. The first objective is patient safety, that is, removing
the life-threatening risks of an expanding mass in the posterior fossa. The
second objective is functional preservation, that is, preserving facial function
and, if possible, hearing. Before the microsurgical era, the risk of mortality
from acoustic tumors was high. A number of factors have combined to improve
the success of acoustic tumor surgery, including the routine use of the microscope,
improved anesthetic techniques, intraoperative monitoring of facial function,
better understanding of the perioperative physiologic stresses of posterior
fossa surgery, and improved diagnostic techniques. Modern series of surgically
managed acoustic neuromas routinely report mortality rates of approximately
1% and anatomic facial nerve preservation rates greater than 90%.1
Three principal surgical approaches are available for managing acoustic
neuroma: middle fossa craniotomy (subtemporal), retrosigmoid craniotomy (suboccipital),
and translabyrinthine craniotomy. The first 2 surgical approaches offer the
possibility of hearing preservation since the otic capsule is not violated.
Each of these approaches has particular strengths. With regard to hearing
preservation, the middle cranial fossa offers complete exposure of the internal
auditory canal with limited posterior fossa exposure. The retrosigmoid approach
offers excellent exposure of the posterior fossa; however, exposure of the
internal auditory canal, especially the lateral one third, is hampered by
the posterior semicircular canal and vestibule. The translabyrinthine approach
offers excellent posterior fossa and internal auditory canal exposure, but
hearing is sacrificed with removal of the semicircular canals. The technical
demands of hearing preservation acoustic neuroma surgery are greater than
in translabyrinthine surgery, since the surgeon must focus on preservation
of the cochlear nerve and its blood supply in addition to the usual considerations
of safe tumor removal and facial nerve preservation.
Our center is convinced that each of these approaches has merit, and
the appropriate approach for a particular patient is individualized based
on the patient's medical status, the anatomic size and location of the tumor,
and the patient's preferences. For most patients, facial function preservation
is a higher priority than hearing preservation, since most of these patients
have already become accustomed to a certain degree of hearing loss in the
affected ear. Nonetheless, hearing preservation and facial function preservation
are not mutually exclusive goals. As more patients are presenting with tumors
at sizes amenable to hearing preservation surgery, the question of whether
hearing preservation surgical approaches pose a greater risk than translabyrinthine
surgery to facial function outcome after acoustic neuroma surgery has become
a significant issue. The purpose of this study is to address the question,
"Is facial function worse after hearing preservation surgery (retrosigmoid
and middle fossa) than after translabyrinthine surgery?" The answer to this
question provides guidance if concern over postoperative facial function should
be a deciding factor in selecting hearing preservation approaches vs nonhearing
preservation approaches in acoustic neuroma surgery.
METHODS
This study retrospectively evaluated 315 consecutive acoustic neuroma
surgical procedures performed by Pittsburgh Ear Associates surgeons (M.A.A.
and D.A.C.) between April 1989 and July 1998. Facial function was graded according
to the House-Brackmann scale.2 All facial nerve
grading was performed by the authors. Facial nerve function was graded at
3 intervals after surgery: immediately after surgery (within 48 hours), at
an intermediate time after surgery (at the 2-week postoperative visit), and
in the long term (at least 3 months after surgery). Data were obtained by
reviewing office records, hospitalization records, operative reports, and
discharge summaries. Tumor measurements are the largest dimension in centimeters
(including internal auditory canal and posterior fossa component).
Statistical comparisons of tumor sizes were made with the t test, and facial function results were evaluated with the  2 test. The statement regarding no statistical difference between groups
means that a statistical test is performed and failed to reject the null hypothesis
(P>.05).
RESULTS
Facial function results are listed separately according to the 6 House-Brackmann
grades and in a grouped fashion. The groups were excellent (grades I and II),
acceptable (grades III and IV), and poor (grades V and VI).
In the total group at long-term follow-up, 80% demonstrated excellent
function, 13% demonstrated acceptable function, and 7% had poor function.
In this group of 315 patients, 58 were operated on through the middle fossa
approach, 48 through the retrosigmoid approach, and 209 through the translabyrinthine
approach. The mean ± SD size was 0.75 ± 0.31 cm for middle fossa
tumors, 1.9 ± 1.09 cm for retrosigmoid tumors, and 2.06 ± 1.12
cm for translabyrinthine tumors. Middle fossa tumors were significantly smaller
than retrosigmoid and translabyrinthine tumors.
Table 1 lists the facial
outcome for these patients according to surgical approach and time after surgery. Table 1 lists all patients in the series
regardless of tumor size, previous operation, anatomic status of the facial
nerve at the conclusion of surgery, primary and revision surgery, and whether
or not data were available at all 3 intervals. This last factor explains the
different totals at the different intervals. These raw data are provided to
facilitate comparison with other reports.
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Table 1. Facial Function and Surgical Approach for All Tumor Sizes
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Overall, at long-term follow-up, 88% of middle fossa patients had excellent
facial function compared with 91% of retrosigmoid patients and 77% of the
translabyrinthine patients. Four patients experienced facial nerve transection:
1 middle fossa, 1 retrosigmoid, and 2 translabyrinthine. In contrast, 2% of
middle fossa patients had poor long-term facial function outcome compared
with 7% of retrosigmoid patients and 7% of translabyrinthine patients.
To adequately compare the effects of the operative approach, we chose
to compare the facial function outcomes in patients with similarly sized tumors.
We selected tumors 1.5 cm and smaller because this was the largest tumor excised
through the middle fossa approach in our series. To fully assess the effects
of the operative procedures, we excluded patients who had previously received
treatment for their acoustic tumors (either surgery or radiation). Also, we
excluded patients who did not present with preoperative grade I facial function.
The facial function of cases that met the criteria for comparison are presented
in Table 2. This group of 167
acoustic tumors measuring 1.5 cm or less were initially treated through the
middle fossa (n = 57), retrosigmoid (n = 27), or translabyrinthine (n = 83)
surgical approach as their initial management. In this series of 167 tumors
measuring 1.5 cm or less, facial function was not significantly different
between either hearing preservation approach and the translabyrinthine approach
at the immediate, intermediate, or long-term time frame. Long-term facial
function was excellent in 90% of translabyrinthine, 89% of middle fossa, and
100% of retrosigmoid cases. Viewed from the perspective of poor functional
outcomes, only 1 patient (2% of middle fossa cases) had poor long-term facial
function.
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Table 2. Facial Function and Surgical Approach in Previously Untreated
Acoustic Tumors Measuring 1.5 cm or Less
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The intervals of these data permitted us to assess delayed facial palsy.
We define delayed palsy as a deterioration of function from excellent or acceptable
to poor from the immediate to intermediate interval. No patients in the retrosigmoid
group experienced delayed palsy, whereas 5 patients (9%) in the middle fossa
group had delayed palsy and 7 patients (8%) in the translabyrinthine group
had delayed palsy. With the exception of 1 patient whose facial function went
from grade II (immediate) to grade IV (intermediate) and remained at grade
IV (long term), all patients with delayed palsy recovered to within 1 grade
of their immediate postoperative function.
The surgical complication rate overall was low. Among the 167 patients
in the small tumor group, 1 patient had meningitis and 7 had cerebrospinal
fluid leakage, with none requiring surgical repair (3 in the translabyrinthine
group [3.6%], 2 in the middle fossa group [3.5%], and 2 in the retrosigmoid
group [7.4%]).
COMMENT
We have previously presented a detailed assessment of hearing preservation
results using our criteria for patient selection.3
Our strategy individualizes the surgical approach to the patient's medical
characteristics, tumor anatomy, and patient preferences. In general, we encourage
hearing preservation in patients with a speech reception threshold of 30 dB
or better and speech discrimination of 70% or better. However, we believe
that a patient with a speech reception threshold of 50 dB and speech discrimination
of 50% is an acceptable candidate. In certain circumstances, depending on
patient preferences, we have offered hearing preservation to patients with
even poorer hearing. We used the middle cranial fossa approach for tumors
involving the internal auditory canal with extension of 0.5 cm or less into
the cerebellopontine angle. In contrast, we use the retrosigmoid approach
for patients with tumors with greater than a 0.5-cm cerebellopontine angle
extension but not reaching the lateral third of the internal auditory canal.
Using these restrictive criteria, we have published an overall useful hearing
preservation rate of 67%, with 74% useful hearing preservation in middle fossa
and 58% useful hearing preservation in retrosigmoid cases.2
Since that publication, the success rate for hearing preservation has improved
with useful hearing preservation in 78% of middle fossa tumors and 64% of
retrosigmoid tumors (M.A.A. and D.A.C., unpublished data). The increasing
emphasis by referring physicians and patients on hearing preservation prompted
us to review our facial function outcomes in acoustic neuroma surgery in a
formal fashion.
In this series, the rate of anatomic preservation of the facial nerve
was 99% overall, with 98% in middle fossa, 98% in retrosigmoid, and 99% in
translabyrinthine cases. Modern series are consistently reporting high rates
of anatomic preservation,4 but function is
the principal concern. This study confirmed our previously identified findings
regarding the chronology of facial function after acoustic neuroma surgery.
Specifically, this study confirms that postoperative facial function after
acoustic neuroma undergoes a temporary decrease in the weeks after surgery
but then recovers during the ensuing months.5
In addition, the relationship of better postoperative facial function in smaller
tumors was also confirmed. Since these facial function outcomes were consistent
with previous statistical trends, the validity of the functional outcomes
observed in the remainder of the study was enhanced.
Although the difference was not significant, translabyrinthine tumors
at the immediate and intermediate intervals showed a trend toward better facial
results than middle fossa tumors in our series of acoustic neuromas 1.5 cm
or smaller. This is consistent with the generally accepted surgical impression
that the facial nerve undergoes greater manipulation in middle fossa than
translabyrinthine surgery for similarly sized tumors, since the facial nerve
must be mobilized to permit removal of the adjacent acoustic neuroma. Nonetheless,
the rate of delayed facial paralysis was similar in the middle fossa and translabyrinthine
series (8% and 9%, respectively). The rate of excellent facial function in
the retrosigmoid cases was 100% at each of the 3 intervals for the retrosigmoid
tumors. This trend in the present study can be explained by our selection
method for offering retrosigmoid surgery. This group of tumors represents
lesions in which the tumor did not reach the fundus of the internal auditory
canal. Thus, most of the dissection of tumor from the facial nerve was not
performed within the confines of the bony limits of the internal auditory
canal. It can be argued that this potentially lessens the trauma to the facial
nerve. Despite these trends, these findings did not reach statistical significance.
Our results confirm the previous findings of no significant difference
between facial function and surgical approaches in a series comparing only
translabyrinthine and middle fossa surgery performed at another center.6 Overall, facial function outcome was not significantly
different from either middle fossa or retrosigmoid vs translabyrinthine resection
of acoustic neuromas 1.5 cm or smaller in this series.
Our series may be biased toward poorer results at the long-term interval,
since we accepted 3-month data for this interval. We know from chronology
studies that the facial function improvement continues for at least a year
after the decrement in function seen at the postoperative visit. Despite this
factor, the long-term facial function rates were excellent in 89% of middle
fossa cases, 90% of translabyrinthine cases, and 100% of retrosigmoid cases
with tumors 1.5 cm or smaller. Despite a slight trend toward better function
in the translabyrinthine and retrosigmoid groups at the intermediate interval,
the difference is not significant. Also, the delayed paralysis rate was the
same for middle fossa and translabyrinthine cases.
Obviously, the decision of how to manage acoustic tumors is complex
and involves many variables, including tumor size, patient age, patient health,
and patient preferences. A patient with useful hearing and a small acoustic
tumor should understand that hearing preservation surgery may expose them
to a slight (not statistically significant) risk of temporary facial weakness
in comparison with nonhearing preservation surgery. For many patients, the
probability of successful hearing preservation outweighs this risk. We conclude
that concerns about postoperative facial function should not be the only deciding
issue for hearing preservation vs translabyrinthine surgery.
AUTHOR INFORMATION
Accepted for publication September 22, 2000.
We thank Robert Rubin, MD, PhD, and Karen Berliner, PhD, for statistical
consultation and Shirley Simonic for manuscript preparation.
From Pittsburgh Ear Associates' Hearing and Balance Center, Allegheny
General Hospital, Pittsburgh, Pa.
Corresponding author and reprints: Moisés A. Arriaga, MD,
Pittsburgh Ear Associates, 420 E North Ave, Suite 402, Pittsburgh, PA 15212.
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