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The long-term outcome of hearing preservation following vestibular schwannoma surgery
Auris Nasus Larynx 27 (2000) 9 – 13 www.elsevier.com/locate/anl
The long-term outcome of hearing preservation following vestibular schwannoma surgery Y. Inoue a,*, J. Kanzaki a, K. Ogawa a, N. Hoya a, S. Takei a, R Shiobara b a
Department of Otolaryngology, School of Medicine, Keio Uni6ersity, 35 Shinanomachi, Shinjuku-ku, Tokyo 160, Japan Department of Neurosurgery, School of Medicine, Keio Uni6ersity, 35 Shinanomachi, Shinjuku-ku, Tokyo 160, Japan
b
Received 17 February 1999; received in revised form 8 April 1999; accepted 14 May 1999
Abstract Objecti6e: The aim of this study is to describe the long-term outcome of preserved hearing after vestibular schwannoma surgery. Methods: Subjects are 20 unilateral vestibular schwannoma patients whose class A hearing of the AAO-HNS classification was preserved successfully after tumor removal. Hearing preservation surgery was attempted via the middle cranial fossa (MCF) or the extended MCF approach. The follow-up periods ranged from 2 to 16 years. The outcome measures included the pure tone average (PTA) and speech discrimination score (SDS). Results: PTA was maintained in less than 30 dB in 11 out of 20 patients within 2 years follow-up, six out of 13 patients within 4 years follow-up, and two out of five patients within 6 years follow-up, respectively. SDS was maintained in more than 70% in 17 out of 20 patients within 2 years follow-up, ten out of 13 patients within 4 years follow-up, and three out of five patients within 6 years follow-up, respectively. Conclusions: The preserved hearing maintained about more than 40% of the patients with the class A hearing in every 2 years follow-up. From this result, we can conclude that the hearing preservation surgery could be one of the best treatments for vestibular schwannoma patients with class A hearing. However, further study will be needed to clarify the mechanism of the deterioration in hearing after hearing preservation surgery. © 2000 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Vestibular schwannoma; Hearing preservation surgery; Hearing level; Speech discrimination score
1. Introduction The recent developments of diagnostic tools such as MRI have increased the incidence of the vestibular schwannoma patients with good hearing. We sometimes see a patient without otological symptoms whose vestibular schwannoma was found by chance, when he had MRI screening on the other purpose. Thus, the hearing preservation is now one of the most important goals in vestibular schwannoma surgery. Although there have been numerous studies on hearing preservation surgery for vestibular schwannoma, there are only a few reports on the long-term outcome of preserved hearing. Because the incidence of the deterioration of preserved hearing was various among the reports [1–8], it seems important to clarify whether the preserved * Corresponding author. Tel.: + 81-3-33531211; fax: +81-353790335.
hearing would be maintained or not in a long-term follow-up. In the present study, we examined the long-term outcomes in auditory functions in vestibular schwannoma after hearing preservation surgery. 2. Subjects and methods The subjects were 20 vestibular schwannoma patients whose hearing was preserved successfully in the class A in the AAO-HNS classification [9] after tumor removal. There were seven women and 13 men, whose age ranged from 20 to 55 years at the operations. Hearing preservation surgery was attempted via the middle cranial fossa (MCF) approach or the extended MCF approach [10]. Preoperative hearing of all patients was the class A in the AAO-HNS classification. Neurofibromatosis patients were excluded in this study.
0385-8146/00/$ - see front matter © 2000 Elsevier Science Ireland Ltd. All rights reserved. PII: S 0 3 8 5 - 8 1 4 6 ( 9 9 ) 0 0 0 4 6 - 2
Y. Inoue et al. / Auris Nasus Larynx 27 (2000) 9–13
10
The mean diameter of the tumors was 6.1 mm in the range from 0 (an intracanalicular tumor) to 16 mm. The original nerve of the tumor was identified at operation in 15 patients. The tumors originated in the inferior vestibular nerve in seven patients, while in the other eight patients the tumors originated in the superior vestibular nerve. In 19 out of 20 cases total tumor removal was performed and in only one case a sub-total removal was performed. The auditory functions were evaluated using pure tone audiometry and speech audiometry. The pure tone average (PTA) was calculated at four frequencies between 500 and 3000 Hz. The increase in PTA of 15 dB or more and the decrease in speech discrimination score (SDS) of 20% or more were defined as a significant deterioration, respectively. Facial nerve function of the patients after tumor removal ranged from House– Brackmann grade I to grade II. The follow-up period ranged from 2 to 16 years with a mean of 4.3 years.
The long-term results in PTA of all patients are summarized in Fig. 2. PTA was maintained in less than 30 dB in 11 out of 20 patients within 2 years follow-up, six out of 13 patients within 4 years follow-up, and two out of six patients within 6 years follow-up, respectively. Five patients showed significant deterioration in PTA during the follow-up periods. Among all the patients a recurrent tumor was found in two patients using MRI.
3. Results
4. Discussion
3.1. Pure tone a6erage (PTA) The changes in PTA of all patients during 5 months after surgery are shown in Fig. 1. The initial value indicated the preoperative hearing level. Audiometry was performed at the bed-side within 2 weeks after surgery. In most patients, PTA demonstrated a significant temporary deterioration immediately after surgery, and then it showed a marked improvement within 2 months.
3.2. Speech discrimination score (SDS) The long-term results in SDS after surgery are shown in Fig. 3. SDS was maintained in more than 70% in 17 out of 20 patients within 2 years follow-up, ten out of 13 patients within 4 years follow-up, and three out of five patients within 6 years follow-up, respectively. Five patients including two recurrent cases showed a significant deterioration in SDS during the follow-up periods.
There are some controversies in the term of ‘hearing preservation’. Some authors suggested that ‘preserved hearing’ should be at least in the class A of the AAOHNS classification when the patient has normal hearing in the opposite side ear [11]. In the present study, therefore, we limited the subjects to only the patients with the class A hearing in the AAO-HNS classification after tumor removal. In order to evaluate the long-term changes in postoperative hearing, we have to clarify which hearing level should be used as an initial value for immediate postop-
Fig. 1. The changes in PTA of all patients during 5 months after surgery.
Y. Inoue et al. / Auris Nasus Larynx 27 (2000) 9–13
11
Fig. 2. The long-term results in PTA of all patients; * recurrent case.
Fig. 3. The long-term results in SDS after surgery; * recurrent case.
erative hearing. Although there are some guidelines for the evaluation of hearing preservation in vestibular schwannoma, they do not mention about the time for the evaluation [9,11]. Thus, we investigated the shortterm hearing change following hearing preservation surgery before analyzing the long-term outcome of postoperative hearing. In the present study, there was temporary deterioration in PTA immediately after surgery in most patients. The deteriorated hearing showed marked improvement within 2 months in most patients. This temporary deterioration of PTA may be caused not only by the cochlear or cochlear nerve damages induced by surgical manipulations, but also by
the middle ear dysfunctions, such as CSF accumulation. McKenna et al. [3] reported that an immediate postoperative audiogram was obtained within 2 months following surgery. Goel et al. [4] also reported that postoperative hearing level was ascertained at 3 months after surgery. From these results, PTA obtained around 2 months after surgery could be used as an immediate postoperative PTA. Thus, immediate postoperative hearing is indicated in the hearing around 2 months after surgery in the present study. However, there were some patients whose hearing deteriorated gradually from the class A to the class B hearing in the AAOHNS classification within 1 year follow-up. Therefore,
Y. Inoue et al. / Auris Nasus Larynx 27 (2000) 9–13
12
retrosigmoid approach after 3 years follow-up. According to these results, the deterioration in the preserved hearing was seen most often after the tumor removal via the MCF approach. However, five out of 20 patients showed significant deterioration in preserved hearing after 4 years follow-up in the present study using MCF approach. In order to clarify the difference in the course of hearing deterioration among the surgical approaches, it should be more important how to treat the internal auditory canal (IAC) than the approach itself. It was not clear whether tumors were completely removed in the IAC or not via the suboccipital and retrosigmoid approaches. Further study will be needed to clarify the difference in hearing deterioration among these approaches. Belal et al. [8] described in their histopathological report about the fibrosis in the cochlea and the IAC after hearing preservation surgery. Shelton [2] also reported histopathological changes in the cochlea such as fibrosis of the scala tympani, osteoid and new bone formation in the area of the round window and a scattered loss of ganglion cells. They speculated from these findings that the scarring and fibrosis in the IAC would lead to progressive constriction of the cochlear vascular supply and it may be a cause of the progressive hearing loss observed in the operated ears. Shelton suggested these pathological changes could be reduced by an use of abdominal fat instead of temporal muscle for packing the IAC after tumor removal in order to prevent CSF leakage [2]. In this series, we obliterated the IAC after tumor removal with the temporal muscle in 12 patients (muscle group), and with the abdominal fat in eight patients (fat group). Although the follow-up period was much longer in the muscle group than in the fat group, there was no significant difference in the
we will need a new guideline for the definition of the immediate postoperative hearing. In the literature, the preserved hearing were reported to be maintained in 44 – 100% of the patients during longterm follow-up [1 – 8]. The differences in the incidence among these reports may depend on several conditions such as follow-up period, preoperative hearing level and surgical approach. However, there was no report describing when the significant deterioration was found in preserved hearing. Thus, we investigated the changes in preserved hearing every 2 years. The relationship between PTA and SDS in our patients with more than 4 years follow-up was shown in Table 1. The change in PTA was not always correlated with the change in SDS, and the changes in the hearing class in the AAO-HNS classification was not always correlated with significant change in hearing. It happened that the hearing was ranged in the class A hearing even after it had shown a significant change in PTA or SDS. This discrepancy could be caused by the difference in the definition between the AAO-HNS hearing class and significant change. From this result, it is not sufficient to describe only about the range of change in hearing (significant change) but also the hearing level itself, in order to evaluate the long-term outcome of hearing preservation surgery. Shelton [2] reported that 14 out of 25 patients whose tumor was removed by the MCF approach showed significant deterioration in their postoperative hearing after 5 years follow-up. On the other hand, McKenna et al. [3] reported only four out of 18 patients showed significant deterioration after tumor removal via the suboccipital approach after 5 years follow-up. In the report of Tucci et al. [5], five out of 17 patients showed significant deterioration after tumor removal via the
Table 1 The relationship between PTA and SDS in the patients who were followed up for more than 4 years (PTA/SDS in the AAO-HNS classification) Obliteration
Muscle
Fat
a b
Age
K.H N.R M.I F.K K.T S.M K.U T.Ob K.Sb Y.F M.K K.K S.A
42 48 37 52 40 64 37 43 45 44 31 20 23
Sex
M F M F F F F M M F M M F
Years after surgery 1
2
3
4
5
A/A A/A A/A A/A A/A A/A A/A A/A A/A
A/A B/A A/A A/A A/A A/A B/A A/A Ba/B
B/A B/Ba A/A A/A A/A A/A B/A A/B B/Ba
B/A Ca/B A/A A/A A/A A/A B/A C/B B/B
B/A C/B B/Aa A/A A/B A/A B/A C/Ca C/B
A/A A/A A/A A/A
a
B/A B/A A/A A/A
B/A B/A A/A
B /A A/A A/A A/A
a
B/A B/A A/A A/A
The period when the patients showed significant deterioration in PTA or SDS. Recurrent case.
6
7
8
9
10
A/A Ba/B A/A B/A
A/A B/A
B/A
Ba/
B/
C/C
C/Ca
C/C
C/C
Y. Inoue et al. / Auris Nasus Larynx 27 (2000) 9–13
course of hearing deterioration between them (Table 1). The results suggest that the material used for packing the IAC is not a sole cause of the deterioration of preserved hearing. On the other hand, tumor recurrence is also considered as a cause of hearing deterioration after hearing preservation surgery. Because all tumors filled up the fundus of IAC in our series, we drilled out the whole IAC in order not to leave tumor in the fundus. However, Ylikoski [12,13] and Neely [14] reported that several cochlear and superior vestibular nerves that appeared to be normal were histologically invaded by a tumor. In the present study, the tumor recurrence was found in two out of 20 patients (10%) by MRI, although in 19 out of 20 cases total tumor removal was performed. Therefore, even in patients who underwent total tumor removal, we should consider tumor recurrence when hearing deteriorates during long-term follow-up. Delayed hydrops in the cochlea after the tumor removal was investigated as another cause of deterioration in preserved hearing [6]. It is a reasonable mechanism to explain about fluctuating hearing in the patients after tumor removal. However, we have never experienced such cases whose hearing was maintained with isosorbide or diuretics. Further study will be needed to clarify the mechanism of the deterioration in hearing after hearing preservation surgery. Although five out of 20 patients showed a significant change in their hearing during the follow-up periods in this study, the hearing was maintained in the class A or B hearing in almost all patients except for two recurrent cases. There was a patient whose hearing was maintained as the class A hearing for 7 years after surgery. From this result, we can conclude that the hearing preservation surgery could be one of the best treatment for the vestibular schwannoma patients with the class A hearing.
.
13
References [1] Palva T, Troupp H, Jauhiainen T. Hearing preservation in acoustic neuroma surgery. Acta Otolaryngol (Stockh) 1985;99:1 – 7. [2] Shelton C, Hitselberger WE, House WF, Brackmann DE. Hearing preservation after acoustic tumor removal: long-term results. Laryngoscope 1990;100:115 – 9. [3] McKenna MJ, Halpin C, Ojemann RG, Nadol JB, Montgomery WW, Levine RA, et al. Long-term hearing results in patients after surgical removal of acoustic tumors with hearing preservation. Am J Otol 1992;13:134 – 6. [4] Goel A, Sekhar LN, Langheinrich W, Kamerer D, Hirsch B. Late course of preserved hearing and tinnitus after acoustic neurilemmoma surgery. J Neurosurg 1992;77:685 – 9. [5] Tucci DL, Telian ST, Kileny PR, Hoff JT, Kemink JL. Stability of hearing preservation following acoustic neuroma surgery. Am J Otol 1994;15:183 – 8. [6] Atlas MD, Harvey C, Fagan PA. Hearing preservation in acoustic neuroma surgery: a continuing study. Laryngoscope 1992;102:779 – 83. [7] Rosenberg RA, Cohen NL, Ransohoff J. Long-term hearing preservation after acoustic neuroma surgery. Otolaryngol Head Neck Surg 1994;97:270 – 4. [8] Belal A, Linthicum FH, House WF. Acoustic tumor surgery with preservation of hearing. Am J Otol 1982;4:916. [9] Committee on hearing and equilibrium guidelines for the evaluation of hearing preservation in acoustic neuroma (vestibular schwannoma), Otolaryngol Head Neck Surg 1995;113:179–180. [10] Kanzaki J, Shiobara R, Toya S. Classification of the extended middle cranial fossa approach. Acta Otolaryngol (Stockh) 1991;487:6 – 16. [11] Sanna M, Karmarkar S, Landolfi M. Hearing preservation in vestibular schwannoma surgery: fact or fantasy? J Laryngol Otol 1995;109:374 – 80. [12] Ylikoski J. Eight nerve in acoustic neuromas. Arch Otolaryngol 1978;104:532 – 7. [13] Ylikoski J. Cochlear nerve in neurilemmomas. Arch Otolaryngol 1978;104:679 – 84. [14] Neely JG. Is it possible to totally resect an acoustic tumor and conserve hearing? Otolaryngol Head Neck Surg 1984;92:162–7.
The long-term outcome of hearing preservation following vestibular schwannoma surgery Y. Inoue a,*, J. Kanzaki a, K. Ogawa a, N. Hoya a, S. Takei a, R Shiobara b a
Department of Otolaryngology, School of Medicine, Keio Uni6ersity, 35 Shinanomachi, Shinjuku-ku, Tokyo 160, Japan Department of Neurosurgery, School of Medicine, Keio Uni6ersity, 35 Shinanomachi, Shinjuku-ku, Tokyo 160, Japan
b
Received 17 February 1999; received in revised form 8 April 1999; accepted 14 May 1999
Abstract Objecti6e: The aim of this study is to describe the long-term outcome of preserved hearing after vestibular schwannoma surgery. Methods: Subjects are 20 unilateral vestibular schwannoma patients whose class A hearing of the AAO-HNS classification was preserved successfully after tumor removal. Hearing preservation surgery was attempted via the middle cranial fossa (MCF) or the extended MCF approach. The follow-up periods ranged from 2 to 16 years. The outcome measures included the pure tone average (PTA) and speech discrimination score (SDS). Results: PTA was maintained in less than 30 dB in 11 out of 20 patients within 2 years follow-up, six out of 13 patients within 4 years follow-up, and two out of five patients within 6 years follow-up, respectively. SDS was maintained in more than 70% in 17 out of 20 patients within 2 years follow-up, ten out of 13 patients within 4 years follow-up, and three out of five patients within 6 years follow-up, respectively. Conclusions: The preserved hearing maintained about more than 40% of the patients with the class A hearing in every 2 years follow-up. From this result, we can conclude that the hearing preservation surgery could be one of the best treatments for vestibular schwannoma patients with class A hearing. However, further study will be needed to clarify the mechanism of the deterioration in hearing after hearing preservation surgery. © 2000 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Vestibular schwannoma; Hearing preservation surgery; Hearing level; Speech discrimination score
1. Introduction The recent developments of diagnostic tools such as MRI have increased the incidence of the vestibular schwannoma patients with good hearing. We sometimes see a patient without otological symptoms whose vestibular schwannoma was found by chance, when he had MRI screening on the other purpose. Thus, the hearing preservation is now one of the most important goals in vestibular schwannoma surgery. Although there have been numerous studies on hearing preservation surgery for vestibular schwannoma, there are only a few reports on the long-term outcome of preserved hearing. Because the incidence of the deterioration of preserved hearing was various among the reports [1–8], it seems important to clarify whether the preserved * Corresponding author. Tel.: + 81-3-33531211; fax: +81-353790335.
hearing would be maintained or not in a long-term follow-up. In the present study, we examined the long-term outcomes in auditory functions in vestibular schwannoma after hearing preservation surgery. 2. Subjects and methods The subjects were 20 vestibular schwannoma patients whose hearing was preserved successfully in the class A in the AAO-HNS classification [9] after tumor removal. There were seven women and 13 men, whose age ranged from 20 to 55 years at the operations. Hearing preservation surgery was attempted via the middle cranial fossa (MCF) approach or the extended MCF approach [10]. Preoperative hearing of all patients was the class A in the AAO-HNS classification. Neurofibromatosis patients were excluded in this study.
0385-8146/00/$ - see front matter © 2000 Elsevier Science Ireland Ltd. All rights reserved. PII: S 0 3 8 5 - 8 1 4 6 ( 9 9 ) 0 0 0 4 6 - 2
Y. Inoue et al. / Auris Nasus Larynx 27 (2000) 9–13
10
The mean diameter of the tumors was 6.1 mm in the range from 0 (an intracanalicular tumor) to 16 mm. The original nerve of the tumor was identified at operation in 15 patients. The tumors originated in the inferior vestibular nerve in seven patients, while in the other eight patients the tumors originated in the superior vestibular nerve. In 19 out of 20 cases total tumor removal was performed and in only one case a sub-total removal was performed. The auditory functions were evaluated using pure tone audiometry and speech audiometry. The pure tone average (PTA) was calculated at four frequencies between 500 and 3000 Hz. The increase in PTA of 15 dB or more and the decrease in speech discrimination score (SDS) of 20% or more were defined as a significant deterioration, respectively. Facial nerve function of the patients after tumor removal ranged from House– Brackmann grade I to grade II. The follow-up period ranged from 2 to 16 years with a mean of 4.3 years.
The long-term results in PTA of all patients are summarized in Fig. 2. PTA was maintained in less than 30 dB in 11 out of 20 patients within 2 years follow-up, six out of 13 patients within 4 years follow-up, and two out of six patients within 6 years follow-up, respectively. Five patients showed significant deterioration in PTA during the follow-up periods. Among all the patients a recurrent tumor was found in two patients using MRI.
3. Results
4. Discussion
3.1. Pure tone a6erage (PTA) The changes in PTA of all patients during 5 months after surgery are shown in Fig. 1. The initial value indicated the preoperative hearing level. Audiometry was performed at the bed-side within 2 weeks after surgery. In most patients, PTA demonstrated a significant temporary deterioration immediately after surgery, and then it showed a marked improvement within 2 months.
3.2. Speech discrimination score (SDS) The long-term results in SDS after surgery are shown in Fig. 3. SDS was maintained in more than 70% in 17 out of 20 patients within 2 years follow-up, ten out of 13 patients within 4 years follow-up, and three out of five patients within 6 years follow-up, respectively. Five patients including two recurrent cases showed a significant deterioration in SDS during the follow-up periods.
There are some controversies in the term of ‘hearing preservation’. Some authors suggested that ‘preserved hearing’ should be at least in the class A of the AAOHNS classification when the patient has normal hearing in the opposite side ear [11]. In the present study, therefore, we limited the subjects to only the patients with the class A hearing in the AAO-HNS classification after tumor removal. In order to evaluate the long-term changes in postoperative hearing, we have to clarify which hearing level should be used as an initial value for immediate postop-
Fig. 1. The changes in PTA of all patients during 5 months after surgery.
Y. Inoue et al. / Auris Nasus Larynx 27 (2000) 9–13
11
Fig. 2. The long-term results in PTA of all patients; * recurrent case.
Fig. 3. The long-term results in SDS after surgery; * recurrent case.
erative hearing. Although there are some guidelines for the evaluation of hearing preservation in vestibular schwannoma, they do not mention about the time for the evaluation [9,11]. Thus, we investigated the shortterm hearing change following hearing preservation surgery before analyzing the long-term outcome of postoperative hearing. In the present study, there was temporary deterioration in PTA immediately after surgery in most patients. The deteriorated hearing showed marked improvement within 2 months in most patients. This temporary deterioration of PTA may be caused not only by the cochlear or cochlear nerve damages induced by surgical manipulations, but also by
the middle ear dysfunctions, such as CSF accumulation. McKenna et al. [3] reported that an immediate postoperative audiogram was obtained within 2 months following surgery. Goel et al. [4] also reported that postoperative hearing level was ascertained at 3 months after surgery. From these results, PTA obtained around 2 months after surgery could be used as an immediate postoperative PTA. Thus, immediate postoperative hearing is indicated in the hearing around 2 months after surgery in the present study. However, there were some patients whose hearing deteriorated gradually from the class A to the class B hearing in the AAOHNS classification within 1 year follow-up. Therefore,
Y. Inoue et al. / Auris Nasus Larynx 27 (2000) 9–13
12
retrosigmoid approach after 3 years follow-up. According to these results, the deterioration in the preserved hearing was seen most often after the tumor removal via the MCF approach. However, five out of 20 patients showed significant deterioration in preserved hearing after 4 years follow-up in the present study using MCF approach. In order to clarify the difference in the course of hearing deterioration among the surgical approaches, it should be more important how to treat the internal auditory canal (IAC) than the approach itself. It was not clear whether tumors were completely removed in the IAC or not via the suboccipital and retrosigmoid approaches. Further study will be needed to clarify the difference in hearing deterioration among these approaches. Belal et al. [8] described in their histopathological report about the fibrosis in the cochlea and the IAC after hearing preservation surgery. Shelton [2] also reported histopathological changes in the cochlea such as fibrosis of the scala tympani, osteoid and new bone formation in the area of the round window and a scattered loss of ganglion cells. They speculated from these findings that the scarring and fibrosis in the IAC would lead to progressive constriction of the cochlear vascular supply and it may be a cause of the progressive hearing loss observed in the operated ears. Shelton suggested these pathological changes could be reduced by an use of abdominal fat instead of temporal muscle for packing the IAC after tumor removal in order to prevent CSF leakage [2]. In this series, we obliterated the IAC after tumor removal with the temporal muscle in 12 patients (muscle group), and with the abdominal fat in eight patients (fat group). Although the follow-up period was much longer in the muscle group than in the fat group, there was no significant difference in the
we will need a new guideline for the definition of the immediate postoperative hearing. In the literature, the preserved hearing were reported to be maintained in 44 – 100% of the patients during longterm follow-up [1 – 8]. The differences in the incidence among these reports may depend on several conditions such as follow-up period, preoperative hearing level and surgical approach. However, there was no report describing when the significant deterioration was found in preserved hearing. Thus, we investigated the changes in preserved hearing every 2 years. The relationship between PTA and SDS in our patients with more than 4 years follow-up was shown in Table 1. The change in PTA was not always correlated with the change in SDS, and the changes in the hearing class in the AAO-HNS classification was not always correlated with significant change in hearing. It happened that the hearing was ranged in the class A hearing even after it had shown a significant change in PTA or SDS. This discrepancy could be caused by the difference in the definition between the AAO-HNS hearing class and significant change. From this result, it is not sufficient to describe only about the range of change in hearing (significant change) but also the hearing level itself, in order to evaluate the long-term outcome of hearing preservation surgery. Shelton [2] reported that 14 out of 25 patients whose tumor was removed by the MCF approach showed significant deterioration in their postoperative hearing after 5 years follow-up. On the other hand, McKenna et al. [3] reported only four out of 18 patients showed significant deterioration after tumor removal via the suboccipital approach after 5 years follow-up. In the report of Tucci et al. [5], five out of 17 patients showed significant deterioration after tumor removal via the
Table 1 The relationship between PTA and SDS in the patients who were followed up for more than 4 years (PTA/SDS in the AAO-HNS classification) Obliteration
Muscle
Fat
a b
Age
K.H N.R M.I F.K K.T S.M K.U T.Ob K.Sb Y.F M.K K.K S.A
42 48 37 52 40 64 37 43 45 44 31 20 23
Sex
M F M F F F F M M F M M F
Years after surgery 1
2
3
4
5
A/A A/A A/A A/A A/A A/A A/A A/A A/A
A/A B/A A/A A/A A/A A/A B/A A/A Ba/B
B/A B/Ba A/A A/A A/A A/A B/A A/B B/Ba
B/A Ca/B A/A A/A A/A A/A B/A C/B B/B
B/A C/B B/Aa A/A A/B A/A B/A C/Ca C/B
A/A A/A A/A A/A
a
B/A B/A A/A A/A
B/A B/A A/A
B /A A/A A/A A/A
a
B/A B/A A/A A/A
The period when the patients showed significant deterioration in PTA or SDS. Recurrent case.
6
7
8
9
10
A/A Ba/B A/A B/A
A/A B/A
B/A
Ba/
B/
C/C
C/Ca
C/C
C/C
Y. Inoue et al. / Auris Nasus Larynx 27 (2000) 9–13
course of hearing deterioration between them (Table 1). The results suggest that the material used for packing the IAC is not a sole cause of the deterioration of preserved hearing. On the other hand, tumor recurrence is also considered as a cause of hearing deterioration after hearing preservation surgery. Because all tumors filled up the fundus of IAC in our series, we drilled out the whole IAC in order not to leave tumor in the fundus. However, Ylikoski [12,13] and Neely [14] reported that several cochlear and superior vestibular nerves that appeared to be normal were histologically invaded by a tumor. In the present study, the tumor recurrence was found in two out of 20 patients (10%) by MRI, although in 19 out of 20 cases total tumor removal was performed. Therefore, even in patients who underwent total tumor removal, we should consider tumor recurrence when hearing deteriorates during long-term follow-up. Delayed hydrops in the cochlea after the tumor removal was investigated as another cause of deterioration in preserved hearing [6]. It is a reasonable mechanism to explain about fluctuating hearing in the patients after tumor removal. However, we have never experienced such cases whose hearing was maintained with isosorbide or diuretics. Further study will be needed to clarify the mechanism of the deterioration in hearing after hearing preservation surgery. Although five out of 20 patients showed a significant change in their hearing during the follow-up periods in this study, the hearing was maintained in the class A or B hearing in almost all patients except for two recurrent cases. There was a patient whose hearing was maintained as the class A hearing for 7 years after surgery. From this result, we can conclude that the hearing preservation surgery could be one of the best treatment for the vestibular schwannoma patients with the class A hearing.
.
13
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