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Auditory and Facial Nerve Function Following Surgery for Cerebellopontine Angle Meningiomas
Pete S. Batra, MD;
Jose C. Dutra, MD;
Richard J. Wiet, MD
Arch Otolaryngol Head Neck Surg. 2002;128:369-374.
ABSTRACT
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Objective To investigate the postoperative auditory and facial nerve function
results after cerebellopontine angle meningioma removal.
Design Retrospective chart review.
Setting Tertiary care referral center.
Patients Twenty-one patients undergoing surgical removal of cerebellopontine
angle meningiomas by the senior author (R.J.W.).
Interventions Translabyrinthine or retrosigmoid approach for tumor extirpation.
Main Outcome Measures Postoperative auditory (pure-tone average and speech discrimination
score) and facial (House-Brackmann scale) function within 1 year of follow-up.
Results Twenty-three operations were performed on 21 patients. Hearing preservation
through the retrosigmoid approach was attempted in 11 patients (48%). Normal
hearing (class A) was preserved in 9 of 10 patients. Normal postoperative
facial nerve function (House-Brackmann grade I) was conserved in 11 (65%)
of 17 patients.
Conclusions This review demonstrates that successful hearing preservation is possible
with meningiomas. Therefore, the retrosigmoid approach should be used whenever
serviceable hearing is present preoperatively. Normal facial nerve function
can also be preserved in the majority of patients.
INTRODUCTION
APPROXIMATELY 10% of all intracranial tumors originate in the cerebellopontine
angle (CPA), with vestibular schwannomas comprising the majority of tumors
in this location.1 Meningiomas are the second
most common neoplasm in the CPA, representing 10% to 15% of tumors.2 They are histologically considered to be benign tumors
arising from the arachnoid villi of the venous sinuses.3
The usual sites of attachment of the posterior fossa meningiomas are the posterior
surface of the petrous bone, tentorium, clivus, cerebellar convexity, and
foramen magnum, in decreasing order of frequency.4
According to Nager and Masica,4 meningiomas
originate in 4 specific locations in the posterior petrous pyramid: the internal
auditory meatus, jugular foramen, region of the geniculate ganglion, and sulcus
of the greater and lesser superficial petrosal nerves. This may account for
the variability of location of meningiomas and for their relationship to critical
structures.
Clinical manifestations of meningiomas are usually otologic or neurologic,
secondary to involvement of contiguous structures of the posterior fossa.
Presenting symptoms commonly include hearing loss, imbalance, tinnitus, facial
numbness, and headaches. Less frequently, patients may complain of trigeminal
neuralgia, diplopia, nausea, facial paresis, otalgia, or loss of taste.2 Indeed, the clinical symptoms of meningiomas can be
very similar to those of vestibular schwannomas, thus making the preoperative
differentiation between the 2 neoplasms difficult.
Surgical removal is the accepted treatment for CPA meningiomas. Hearing
conservative and ablative approaches have been effectively used for tumor
extirpation. Hearing ablative surgery is performed in patients without serviceable
hearing, usually through the translabyrinthine approach. The retrosigmoid
and middle fossa techniques allow for hearing preservation whenever serviceable
hearing is present. Meningiomas of the CPA present a challenge to the neurotologist
for several reasons: (1) they are uncommon CPA tumors; (2) they are difficult
to distinguish from vestibular schwannomas, clinically; (3) the morbidity
associated with unchecked tumor growth; and (4) the formidable task of complete
tumor resection with minimal functional impairment.
There is relative paucity in the literature of reports critically assessing
the postoperative auditory and facial nerve function after CPA meningioma
surgery. Recent studies have suggested that hearing levels can be successfully
preserved with CPA meningiomas, even in the presence of large tumors.2, 5-6 Facial nerve function
can also be conserved in a significant number of patients. In this study,
we review the auditory and facial nerve function of 21 patients undergoing
CPA meningioma surgery.
PATIENTS AND METHODS
Twenty-one patients underwent surgical removal of histologically confirmed
CPA meningiomas by the neurotologic and neurosurgical teams at Hinsdale and
Evanston Hospitals (Illinois) between October 1982 and October 1998. A retrospective
analysis was performed on these patient records. The presenting clinical symptoms
were determined for all of these patients. Tumor size and site of origin were
determined from the preoperative magnetic resonance (MR) or computed tomography
scans and operative reports. Tumors were classified as premeatal (arising
anterior to the internal auditory canal) or retromeatal (arising from the
temporal bone posterior to the internal auditory canal). The surgical approach
used for removal of these tumors depended on preoperative hearing level, age,
and the general health of the patient. The translabyrinthine approach was
used in patients with poor preoperative hearing, regardless of tumor size.
This generally translated into pure-tone average (PTA) greater than 50 dB
and speech discrimination score (SDS) less than 50%. The retrosigmoid or suboccipital
approach was used in patients with class A or B hearing, even in patients
with large tumors ( 3.5 cm).
Preoperative and postoperative auditory and facial nerve function was
assessed within 1 year of follow-up. For patients undergoing hearing preservation
surgery, the mean PTA and SDS were calculated. Based on the PTA and SDS, preoperative
and postoperative hearing was classified based on the system used by the Committee
on Hearing and Equilibrium guidelines.7 The
preoperative and postoperative facial nerve function was graded based on the
House-Brackmann scale.8
RESULTS
PATIENT CHARACTERISTICS
Twenty-one patients underwent 23 procedures for surgical removal of
CPA meningiomas; 11 patients (52%) were female and 10 (48%) were male. The
age range of the patient population was 37 to 74 years with an average age
of 55.7 years. The clinical symptoms most commonly consisted of hearing loss,
imbalance, tinnitus, facial numbness, and headaches. Less frequently, patients
presented with vertigo, aural fullness, facial paresis, diplopia, or otalgia
(Table 1). The mean symptom duration
at presentation was 24.8 months with a range of 1 month to 10 years.
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Table 1. Symptoms in 21 Patients With Cerebellopontine Angle Meningiomas*
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TUMOR CHARACTERISTICS
Fourteen (67%) of the 21 tumors were located on the right side and 7
(33%) tumors on the left side. The meningioma size was determined as the largest
tumor dimension in centimeters on MR or computed tomographic scan. The average
size of the tumors was 2.4 cm with the range from 0.8 to 5 cm. Figure 1 demonstrates the typical MR appearance of CPA meningioma.
The tumor location was purely extracanalicular in 10 (48%), purely intracanalicular
in 2 (9%), and both extracanalicular and intracanalicular in 9 (43%) of the
patients (Table 2). The tumor
location was classified as premeatal in 11 (52%) and retromeatal in 10 (48%)
patients. The site of origin was as follows: petrous ridge in 13 (62%), petroclival
region in 4 (20%), tentorium in 2 (9%), and internal auditory canal in 2 (9%)
patients.
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Figure 1. T1-weighted magnetic resonance
image of left cerebellopontine angle meningioma compressing the adjacent brainstem.
Note the enhancing dural tail.
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Table 2. Tumor Characteristics*
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Twenty patients with meningiomas were newly diagnosed patients. The
last patient had recurrent meningioma previously resected at another institution
22 years ago. Hearing conservation was attempted in 11 patients by the retrosigmoid
approach in patients with class A or B hearing preoperatively. Nine of the
meninigomas were removed by the translabyrinthine approach and 1 by the retrosigmoid
approach in patients with nonserviceable hearing. Residual disease was treated
by surgery in 2 patients with nonserviceable hearing; thus, 23 total procedures
were performed on 21 patients.
Patients were monitored for residual and recurrent disease by interval
MR imaging with gadolinium enhancement. Imaging was performed at 1, 2, and
5 years postoperatively. The patients were considered free of disease when
no tumor was identified at the 5-year follow-up MR study. Any evidence of
new disease 5 years after surgery was classified as recurrent disease and
any evidence of disease within 5 years postoperatively, especially in patients
of subtotal resection, was classified as residual disease. Based on these
criteria, 1 case of recurrence occurred 10 years after hearing preservation
surgery by the retrosigmoid approach. The patient was subsequently treated
with stereotactic radiosurgery with stabilization of tumor growth.
Nineteen of the 21 patients underwent complete resection of the meningioma
at the first procedure. Two patients underwent subtotal resection of the meningioma
and were classified as having residual disease. In the first patient, subtotal
resection was performed secondary to intraoperative hemorrhage. Residual disease
was evident 2 years postoperatively; this was successfully removed by the
translabyrinthine approach. The second patient underwent subtotal resection
of a 2.2-cm meningioma; the tumor was noted to be aggressive histologically
with cytologic atypia and mitotic figures. This patient subsequently underwent
retrosigmoid removal of a residual tumor 2 years later. Residual disease was
documented 2 years later that required radiation therapy; this disease has
been stable for 3 years after radiation treatment.
AUDITORY RESULTS
Clinically, 10 of the 11 patients retained good or serviceable hearing
after surgery; 10 patients had class A hearing preoperatively. Postoperatively,
9 of the 10 patients had preservation of class A hearing. One patient retained
class B hearing after the surgery. One patient with class C hearing preoperatively
was noted to have class D hearing postoperatively (Figure 2). The average preoperative PTA for these 11 patients was
16 dB with a SDS of 86%. Subsequent to surgery, the average PTA was 20 dB
and the SDS was 87%.
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Figure 2. Preoperative and postoperative
auditory function in patients undergoing hearing conservation surgery according
to class of hearing. PTA indicates pure-tone average; SDS, speech discrimination
score.
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The tumor size ranged from 1.8 cm to 3.5 cm in the 9 patients who retained
class A hearing after surgery. Another patient with a 2.5-cm tumor, initially
with class A hearing, developed class B hearing after the surgery. The last
patient in the hearing preservation group had class C hearing with a 0.8-cm
petrous ridge meningioma, preoperatively. This patient had class D hearing
after the surgery. Tumor size did not affect the ability to successfully preserve
hearing in this group of patients. Eight of the meningiomas in the hearing
preservation group were classified as purely extracanalicular; class A hearing
was present in 6 (75%) of these patients postoperatively. Three were identified
as being extracanalicular; extension into the internal auditory meatus did
not affect hearing outcomes as all 3 patients retained class A hearing postoperatively.
Tumor location affected the possibility of successful hearing preservation
(premeatal vs retromeatal). Hearing conservation using the retrosigmoid approach
was attempted in all 10 retromeatal patients, regardless of tumor size. Postoperatively,
class A hearing was preserved in 8 of 9 patients. One patient retained class
B hearing after the surgery. Another patient with class B hearing preoperatively
developed class C hearing postoperatively. Ten of 11 premeatal patients did
not have serviceable hearing preoperatively. These patients underwent tumor
resection by the translabyrinthine approach. One premeatal patient with class
A hearing successfully retained the same level of hearing postoperatively.
FACIAL NERVE FUNCTION RESULTS
Facial nerve function results were available on 19 patients. The postoperative
facial nerve function on 2 patients could not be determined from clinical
records and were excluded from the analysis. Seventeen patients had a grade
I House-Brackmann score preoperatively. Eleven (65%) of 17 patients maintained
a grade I score after the surgery. In the remaining patients with grade I
preoperative facial nerve function, 2 (11.5%) retained grade II, 2 (11.5%)
maintained grade III, 1 (6%) retained grade IV, and 1 (6%) developed grade
VI function after surgery (Figure 3). In the patient with postoperative grade VI facial function, the facial nerve
had to be divided secondary to intimate involvement with the tumor. One patient
had grade VI function preoperatively; his facial function improved to a grade
IV score subsequent to tumor removal. Another patient with grade III function
before surgery developed grade VI function postoperatively.
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Figure 3. Postoperative facial nerve function
results in patients with grade I function preoperatively.
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The 17 patients with normal preoperative facial nerve function were
divided into groups based on tumor size (<2.0 cm, 2.0-4.0 cm, and >4.0
cm) to determine the effect of tumor size on postoperative facial function.
In the smaller than 2.0-cm group, 2 of 5 of the patients had normal postoperative
function. Seven of 10 patients in the 2.0- to 4.0-cm group had normal function
after the surgery. Only 1 in 2 patients had normal facial nerve function when
the preoperative tumor size was larger than 4.0 cm. Tumor size did not statistically
affect postoperative facial function using the Fisher exact test (P = .52).
The tumor location affected the postoperative facial nerve function.
All 10 patients with retromeatal tumors had grade I facial nerve function
preoperatively. All of these patients retained grade I function after surgery.
Seven patients with premeatal tumors had grade I function preoperatively.
Only 1 patient maintained grade I function after surgery. Facial function
in the remainder of the patients was as follows: grade II (2), grade III (2),
grade IV (1), and grade VI (1). Another premeatal patient with grade VI preoperative
function developed grade IV function postoperatively. The last patient with
grade III function preoperatively developed grade VI function after surgery.
The Fisher exact test was used to determine the statistical difference between
facial nerve outcome by the tumor location. Facial nerve function was more
likely to be preserved in patients with retromeatal tumors (P = .025).
COMPLICATIONS
Complications occurred in 6 patients postoperatively in this series;
auditory impairment and facial nerve deficits were considered separately.
A total of 15 complications occurred during the 23 procedures. Cerebrospinal
fluid leak, the most common complication, was seen in 4 patients. Postoperative
pneumonia and lower cranial nerve deficits occurred in 3 patients. Tracheostomy
secondary to respiratory failure was required in 2 patients. In these 2 patients,
the tumor size was 4.0 cm and 5.0 cm, respectively. Subdural hygroma, cerebellar
hematoma, and meningitis were seen in 1 patient each (Table 3).
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Table 3. Complications of Cerebellopontine Angle Meningioma Surgery
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COMMENT
Review of the literature shows few reports on sound audiometric data
for CPA meningiomas. This is compounded by the significant variability in
the data that are available on the postoperative auditory results.2, 6, 9-13
With this in mind, the goal of this retrospective analysis was to closely
examine preoperative and postoperative audiometric results for patients undergoing
hearing conservation surgery through the retrosigmoid approach. Hearing preservation
was attempted in 11 patients who underwent CPA meningioma resection in this
series. Class A hearing was preserved in 9 of 10 patients. The last patient
with class A hearing prior to surgery retained class B hearing postoperatively.
These data compare favorably to the auditory results available from
the other series. Grey et al5 attempted hearing
preservation in 11 patients and were able to achieve serviceable or better
hearing in 8 (73%) patients. Nassif and associates6
attempted hearing preservation in 16 of 56 patients with meningiomas presenting
to the House Ear Clinic, Los Angeles, Calif. Hearing levels were "preserved
near the preoperative level in 75% of patients postoperatively."6
Similarly, Schaller et al2 reviewed postoperative
auditory function after CPA meningioma removal in 13 patients with successful
hearing preservation being achieved in 69% of the patients. These studies
have shown that preoperative tumor size does not influence hearing results
as noted in this study.
Preoperative tumor location affected the ability to preserve hearing
with surgery. Ten of 11 patients with premeatal tumors had nonserviceable
hearing (class C or D) preoperatively. All 10 patients underwent successful
tumor removal by the translabyrinthine approach. In contrast, 9 patients with
retromeatal tumors had class A hearing preoperatively. Eight of 9 patients
maintained hearing at this level after retrosigmoid tumor removal. Similarly,
Schaller et al2 noted that hearing preservation
was generally only possible for retromeatal tumors. All premeatal patients
in their study had nonserviceable hearing preoperatively.2
The observed differences are likely secondary to the relationship of the tumor
to the cochlear-facial nervovascular bundle. Premeatal meningiomas are located
on the inner side of the arachnoid; thus, the relationship between the tumor
and the internal auditory canal is more intimate. The difficulty in achieving
a clean plane of separation between the nerves and the tumor results in lower
likelihood of preservation of auditory and facial function. Retromeatal tumors
are generally separated from the nerves by an arachnoid layer; they are less
likely to invade the neurovascular structures of the internal auditory canal
and allow for conservation of auditory and facial function.
Hearing preservation was not attempted in patients with class C or D
hearing preoperatively in this study. Case reports by Vellutini et al13 and Maurer and Okawara14
have demonstrated that hearing restoration can occur with meningiomas, even
in the face of profound preoperative deficit. More data are clearly required
before one can recommend hearing conservation for all patients, regardless
of preoperative hearing status, with presumptive diagnosis of CPA meningioma.
The success rate of hearing conservation achieved in CPA meningioma
surgery is significantly different than vestibular schwannoma surgery. In
a review of 10 large series, Gardner and Robertson15
found the hearing preservation rate to be 33% for these tumors. Similarly,
Cohen et al11 demonstrated successful hearing
conservation in 32% of the patients with anatomic preservation of the cochlear
nerve. The chance of hearing preservation was poor for vestibular schwannomas
larger than 1.5 cm; thus, the translabyrinthine approach was recommended for
patients in this category. Although no definitive explanation exists, the
observed difference in results may be related to the more intimate involvement
of the acoustic tumors with the cochlear nerve or its blood supply. Thus,
direct trauma to the nerve or disruption of the blood supply during tumor
extirpation may result in lower success rate in hearing preservation with
vestibular schwannomas.
Based on these data, the possibility of hearing conservation is clearly
superior for CPA meningiomas, even for large-sized tumors. Hearing preservation
should be attempted in retromeatal meningiomas of all sizes, if feasible,
with good or serviceable hearing (class A or B) preoperatively. Thus, it is
crucial to differentiate between meningiomas and vestibular schwannomas preoperatively,
as hearing preservation is rare with large acoustic tumors. Gadolinium-enhanced
MR imaging has been reliably used to differentiate between these 2 tumors.
Meningiomas generally possess a broad dural base on the posterior petrous
face with an enhancing tail. They are usually not centered around the internal
auditory meatus and rarely cause erosion or penetration of the internal auditory
canal. In addition, they may present with signs of calcification and local
hyperostosis. In contrast, vestibular schwannomas tend to be round, often
cystic masses that are centered around the internal auditory meatus causing
erosion or extension into the internal auditory canal.5
Facial nerve function was satisfactorily preserved in majority of the
patients in this series. Seventy-six percent of the patients with normal preoperative
facial function retained grade I or II function postoperatively. Two patients
developed grade VI function postoperatively, including 1 patient in whom the
facial nerve was divided secondary to involvement with the tumor. This compares
favorably with the findings by Schaller et al.2
Six of 10 patients with normal preoperative facial function retained grade
I or II function, while another 30% of patients maintained grade III or IV
function postoperatively.
Preoperative facial nerve paresis has been found to be a risk factor
for postoperative facial dysfunction. Schaller et al2
noted that all 3 patients with preoperative facial paresis developed grade
VI paralysis in their series. Similarly, 1 patient with grade III paralysis
in our series worsened to grade VI subsequent to the surgery. Interestingly,
another patient with grade VI dysfunction preoperatively gradually improved
to grade IV function after surgery.
Tumor size has also been noted to be a risk factor for facial paresis
after meningioma removal. All patients in the Schaller et al series with grade
III or worse facial function after surgery had preoperative tumor size larger
than 3.0 cm. Our series did not show statistical correlation with regard to
tumor size and postoperative facial function. The general trend demonstrated
that 66% (4 of 6) and 73% (8 of 11) of patients retained grade I or II facial
function for tumor sizes smaller than 2.0 cm and 2.0 to 4.0 cm, respectively.
One in 2 patients maintained normal postoperative facial function when tumor
size was larger than 4.0 cm.
Tumor location affected the postoperative facial nerve function. All
10 retromeatal patients with preoperative grade I function retained function
at this level postoperatively when undergoing retrosigmoid tumor removal.
Only 1 of 7 premeatal patients retained grade I facial function. The more
intimate involvement of the premeatal tumors with the facial and cochlear
nerves may account for the lower likelihood of preservation of facial function.
Nevertheless, given the success rate in maintaining good facial function postoperatively,
facial nerve preservation should always be attempted, when possible, with
CPA meningiomas.
CONCLUSIONS
This retrospective study demonstrates that CPA meningioma removal can
be successfully achieved by both translabyrinthine and retrosigmoid approaches.
The retrosigmoid approach was effectively used for preservation of auditory
and facial function for retromeatal meningiomas in this series. The translabyrinthine
approach was efficacious for removal of premeatal meningiomas with nonserviceable
hearing. Thus, hearing preservation should be attempted for retromeatal meningiomas
whenever feasible, even in the face of large tumors. Facial nerve function
can also be preserved following meningioma removal, and the success rate for
facial nerve preservation is greater with retromeatal compared with premeatal
tumors.
AUTHOR INFORMATION
Accepted for publication October 10, 2001.
Corresponding author: Richard J. Wiet, MD, Division of Otolaryngology–Head
and Neck Surgery, Evanston Northwestern Healthcare, 1000 Central St, Suite
610, Evanston, IL 60201.
From the Division of Otolaryngology–Head and Neck Surgery, Evanston
Northwestern Healthcare, Evanston, Ill, and the Department of Otolaryngology–Head
and Neck Surgery, Northwestern University Medical School, Chicago, Ill.
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