Solitary Schwannoma of the Eighth Cranial Nerve
The
An Immunohistochemical Jean F. E.
Study of the Cochlear Nerve-Tumor Interface
Marquet, MD; Glen E. J. Forton, MD; F. Erwin Offeciers, MD; Liliane L. M. Moeneclaey
\s=b\ Given recent controversy concerning hearing preservation surgery of the acoustic neurinoma, an immunohistochemical study was undertaken to investigate the cochlear nerve\p=n-\tumorinterface. Ten intact medium-sized acoustic neurinomas were studied by means of classic staining procedures and an immunohistochemical technique using monoclonal mouse antibodies to human neurofilaments. Our observations indicate that the cochlear nerve is histologically involved in the tumoral process in those cases in which macroscopically visible adherences between the cochlear nerve and the tumor are present. We were not able to discern a clear cleavage plane. Six of the 10 specimens showed tumoral invasion of the cochlear nerve. Several therapeutic attitudes are discussed in view of these observations and reports from the international literature. In conclusion, the principle of hearing preservation surgery is rejected in favor of total tumor removal in every case in which surgery is indicated. (Arch Otolaryngol Head Neck Surg.
1990;116:1023-1025)
Facing
the increasing number of articles dedicated to hearing con¬ servation surgery in those with acous¬ tic neurinomas, we initiated a histopathologic study on the interface be¬ tween the cochlear nerve and the tumor. Indeed, histopathologic evi¬ dence of cochlear nerve involvement or invasion is, in our opinion, a very seriAccepted for publication March 30, 1990. From the Ear, Nose, and Throat Department (Head: Prof Dr Marquet), University of Antwerp, Belgium. Reprint requests to Ear, Nose, and Throat Laboratory (T6.17), University of Antwerp\p=n-\UIA,Universiteitsplein 1, B-2610 Wilrijk (Antwerp), Belgium (Dr Forton).
ous
argument against hearing conser¬
vation surgery. As mentioned by Marquet1 in 1986, several points have to be considered when discussing acoustic neurinoma surgery. Recent advances in medical imaging techniques have enabled us to visualize very small acoustic tumors with unprecedented accuracy. The neuro-otologist is therefore offered two options when confronted with a newly diagnosed acoustic neurinoma: to operate or not to operate. The latter attitude is especially indicated in el¬ derly people with slowly growing tu¬ mors, in cases of bilateral acoustic neurinomas (as observed in some par¬ ticular patients and more commonly in those with neurofibromatosis type II), and in patients with a single hearing ear.
Should the surgeon decide not to perform surgery, a meticulous followup stratagem is to be carried out to monitor the growth of the tumor. For¬ tunately, gadolinium-pentetic acid magnetic enhanced resonance imaging allows excellent visualization of small intracanalicular tumors. Surgery can thus be postponed and whatever may be left of useful hearing on the affected side can be saved until surgery be¬ comes indicated. However, should the surgeon decide to operate at once, there are several points worth considering: the surgical inaccessibility of the fundus of the in¬ ternal auditory meatus by way of the suboccipital approach; the biochemical alterations that occur in the perilymph fluid in the course of tumor develop¬ ment, as demonstrated by Silverstein and Schuknecht2; and the vascular le-
sions that may be caused either by tu¬ mor growth or during surgery. House and Hitselberger3 consider these vas¬ cular lesions to be one of the major causes of postoperative deafness de¬ spite the anatomic integrity of the cochlear nerve. Also worth consider¬ ing are the histopathologic aspects of acoustic neurinomas in relation to the cochlear nerve. Although benign, the schwannoma, which usually originates from the inferior branch of the vesti¬ bular nerve, actually tends to destroy adjacent nerves, first by crushing them and later by invading them. Invasion of the cochlear nerve by the acoustic neurinoma has been described by Neely and associates,4 5 Ylikoski et al,6'7 and Forton et al.8 Even facial nerve in¬ volvement has been described by Luetje et al.9 Our observations have shown that recurrent acoustic neuri¬ nomas have a mean growth rate of 4.2 mm/y in every dimension,1 a fact that is frequently overlooked by sev¬ eral authors. These figures are compa¬ rable with those of Wazen et al,10 who have found a mean growth rate of 3.8 mm/y. In this study, we are partic¬ ularly interested in the nerve-tumor interface, in order to establish any co¬ chlear nerve involvement or invasion. MATERIALS AND METHODS We have studied 10 intact medium-sized acoustic neurinomas that have been re¬ moved via the translabyrinthine approach. These tumors were removed by the senior authors (J.F.E.M. and F.E.O.) en bloc with the cochlear nerve, allowing not only the identification of all the nervous structures involved but also the serial sectioning of the specimens. In all 10 cases, macroscopically visible adhérences between the cochlear
Downloaded From: http://archotol.jamanetwork.com/ by a University of Michigan User on 06/19/2015
Fig 1.—The nerve-tumor interface (Masson trichrome stain, X166). Note the close relationship that exists between the cochlear nerve and the tumor. A cleavage plane cannot be iden¬ tified.
Fig 2.—Detail of the nerve-tumor interface (Masson trichrome stain, X646). The tumor mass is stained green, which is partly due to the large amounts of collagen that are present. Note the red myelin sheaths (arrows), surrounded by green streaks of perineural connective tissue, and note the absence of a clear cleavage plane between the nerve and the neurinoma.
Fig 3.—The nerve-tumor interface (Verhoeff's stain, X66). The tumor mass is stained ocherous, clearly showing red streaks of collagen. The perineural connective tissue is stained red as well and the myelin sheaths show an unspecific gray.
Fig 4.—Detail of the nerve-tumor interface (Verhoeff's stain, X646). Note again the absence of a cleavage plane. Note that the nerve-tumor interface is composed of tumor matrix and poorly organized whirling bands of collagen as well as nerve fibers.
Fig 5.—An immunohistochemìcally treated section (Dakopatts M762, 109, and P850) featuring the cochlear nerve (X166). The axons are stained brown, indicating the presence of neurotilaments. Nuclei are stained
purplish blue.
Fig 6.—Detail of the nerve-tumor interface (peroxidase-antiperoxidase method with antibodies to human neurofilaments [Dakopatts M762, Z109, and P850]) (X646). Note the presence of cochlear nerve fibers (arrows) past the assumed nerve-tumor interface. These nerve fibers are surrounded by the polymor¬ phous nuclei of the proliferating cell population, indicating inva¬ sion of the cochlear nerve by the tumor.
Downloaded From: http://archotol.jamanetwork.com/ by a University of Michigan User on 06/19/2015
and the tumor were present. The specimens were fixed in a buffered 4% formaldehyde solution and embedded in nerve
paraffin. Subsequently, they were
cut
on a
microtome (Leitz) in 6-Mm-thick sections. These were mounted on slides precoated with poly-L-lysine. Three different staining procedures were performed. First, Masson's trichrome stain was applied, because it is a quick and easy routine stain and because it stains myelin red, which is a useful characteristic. Sec¬ ond, Verhoeff's elastin stain was applied, because it yields a clear picture, rich with contrasts: the characteristic streaks of col¬ lagen, which are colored red are readily identifiable in the tumor mass, which is stained ocherous. The nerve fibers, how¬
particularly stained. Only perineural connective tissue is colored red by this method. Thus, any connective tissue septum that might exist between the co¬
ever, are not
chlear nerve and the tumor should be visu¬ alized in this manner. Last, we devised an immunohistochemical protocol using mon¬ oclonal mouse antibodies to human neurofilament protein (2F11) (Dakopatts M762) as primary antibodies, rabbit immunoglob¬ ulins to mouse immunoglobulins (Dako¬ patts Z109) as secondary antibodies, and monoclonal peroxidase-antiperoxidase
antibody complexes (Dakopatts P850). A 3,3-diaminobenzidine tetrahydrochloride solution was used as chromogenic agent. Thus, any present bundle of nerve fi¬ mouse
stained brown. A discrete Harris' was used as counterstain. The details of our staining methods are discussed in a previous article.8 bers
was
hematoxylin stain
RESULTS
Rather than searching for tumoral cells invading the cochlear nerve, we decided to look for cochlear nerve fi¬ bers past the nerve-tumor interface and to search for connective tissue structures separating the cochlear nerve from the tumor. In none of the 10 specimens were we able to discern any well-defined connective tissue struc¬ ture separating the cochlear nerve from the tumor, let alone a true sep¬ tum. There appeared to be only loose and ill-oriented streaks of collagen be¬ tween them (Figs 1 through 4). The immunohistochemical tech¬ nique, however, revealed the presence of cochlear nerve fibers beyond the nerve-tumor interface in six of the 10 specimens. The axons were surrounded by tumoral and normal Schwann cells (Figs 5 and 6). Conversely, some spec¬ imens showed penetration of tumoral
tissue between the cochlear bers (Fig 6).
nerve
fi¬
CONCLUSIONS Our findings indicate that tumor in¬ vasion of the cochlear nerve is to be expected in those cases where adhér¬ ences between the cochlear nerve and the tumor are present. So-called sharp dissection is, in our opinion, not indi¬ cated in these cases, since tumoral tis¬ sue will inevitably be left behind; even¬ tually this could lead to tumor recur¬ rence.
It is
our
firm conviction that total
tumor removal is of the utmost impor¬ tance and should remain the primary goal of acoustic neurinoma surgery,
when this implies removal of the cochlear nerve, and in certain cases of the facial nerve as well. Doing this, we have observed only two cases of tumor recurrence in 150 patients operated on between 1974 and 1988. In both pa¬ tients tumoral tissue had to be left be¬ hind for vital reasons. Our observations indicate that there is no correlation whatsoever between tumor size and the degree of hear¬ ing loss, nor between tumor size and tumoral invasion of the cochlear nerve. Total deafness has been ob¬ served even with small intracanalicular tumors. As for the quality of the hearing one would attempt to save, it may be rele¬ vant to consider that 95% of all pa¬ tients having an acoustic neurinoma already have poor hearing on the af¬ fected side when their tumor is first diagnosed." If good hearing is present on the contralateral side, is it really worth saving nonserviceable hearing and taking the risk of tumor recur¬ rence? On the other hand, if a very small tumor should be found in a patient with excellent bilateral hear¬ ing, we are convinced that this partic¬ ular patient would be far better off if surgery could be postponed and metic¬ ulous follow-up could be carried out. In conclusion, given the advances that have been made in the field of medical imaging techniques, we be¬ lieve that the indications for acoustic neurinoma surgery may need some re¬ consideration. Indeed, we advocate that total tumor removal be carried out whenever the decision is taken to even
operate for any
ing
on an
acoustic neurinoma. If, whatsoever, the hear¬
reason
must be
preserved,
an
expectant
attitude is recommended. Hence, in our opinion, there is no place for hear¬
ing preservation
surgery.
References 1. Marquet J. Consid\l=e'\rationssur le traitement chirurgical des tumeurs de l'angle ponto-c\l=e'\r\l=e'\belleux.In: Fraysse B, Lazorthes Y, eds. Neurinomes de l'acoustique: Acquisition et controvers-
Toulouse, France: Editions M\l=e'\dicalesPierre Fabre; 1986:43-51. 2. Silverstein H, Schuknecht H. Biochemical studies of inner ear fluid in man: changes in otosclerosis, M\l=e'\ni\l=e`\re'sdisease and acoustic neuroma. Arch Otolaryngol Head Neck Surg. 1966; es.
84:395. 3. House WF, Hitselberger WE. The neurootologist's view of surgical management of acoustic neuromas. Clin Neurosurg. 1985;32:214-222. 4. Neely JG, Hough J. Histologic findings in two very small intracanicular solitary schwannomas of the eighth nerve. Ann Otol Rhinol Laryngol.
1986;95:460-465. 5. Neely JG. Gross and microscopic anatomy of
eighth cranial nerve in relationship to the solitary schwannoma. Laryngoscope. 1981; the
91:1512-1531. 6. Ylikoski J, Collan Y, Palva T, Jauhiainen T. Cochlear nerve in neurilemomas. Arch Otolaryngol Head Neck Surg. 1978;104:679-684. 7. Ylikoski J, Palva T, Collan Y. Eighth nerve in acoustic neuromas. Arch Otolaryngol Head Neck
Surg. 1978;104:532-537.
8. Forton G, Moeneclaey L, Declau F, Marquet J. The involvement of the cochlear nerve in neurinomas of the eighth cranial nerve. Arch Otorhi-
nolaryngol. 1989;246:156-160. 9. Luetje CM, Whittaker CK, Callaway LA, Veraga G. Histological acoustic tumor involvement of the VIIth nerve and multicentric origin in the VIIIth nerve. Laryngoscope. 1983;93:1133-1139. 10. Wazen
J, Silverstein H, Norrel H, Besse B.
Preoperative and postoperative growth acoustic
rates in documented with CT scanHead Neck Surg. 1985;93:151\x=req-\
neuromas
ning? Otolaryngol
155. 11. Van de Heyning P, Marquet J, Declau F. The preservation of facial function in acoustic neuroma surgery. In: Proceedings of the Sixth International Symposium on the Facial Nerve. Amsterdam, the Netherlands: Kugler & Ghedim; 1988.
Editorial Footnote The authors report their findings on 10 specimens that included tumor and cochlear nerve. They found evidence that the tumor is intimately connected with nerve, rendering ineffective those proce¬ dures designed to remove tumor and pre¬ serve the integrity of the nerve. The authors conclude that preservation of hearing can¬ not and should not be realistic goals in most patients, but they fall short of providing the final answer. We need to know the incidence of tumor recurrence in patients who have had tumor removal with preservation of
tumor
hearing.
Downloaded From: http://archotol.jamanetwork.com/ by a University of Michigan User on 06/19/2015
Byron J. Bailey, MD Chief Editor
The
An Immunohistochemical Jean F. E.
Study of the Cochlear Nerve-Tumor Interface
Marquet, MD; Glen E. J. Forton, MD; F. Erwin Offeciers, MD; Liliane L. M. Moeneclaey
\s=b\ Given recent controversy concerning hearing preservation surgery of the acoustic neurinoma, an immunohistochemical study was undertaken to investigate the cochlear nerve\p=n-\tumorinterface. Ten intact medium-sized acoustic neurinomas were studied by means of classic staining procedures and an immunohistochemical technique using monoclonal mouse antibodies to human neurofilaments. Our observations indicate that the cochlear nerve is histologically involved in the tumoral process in those cases in which macroscopically visible adherences between the cochlear nerve and the tumor are present. We were not able to discern a clear cleavage plane. Six of the 10 specimens showed tumoral invasion of the cochlear nerve. Several therapeutic attitudes are discussed in view of these observations and reports from the international literature. In conclusion, the principle of hearing preservation surgery is rejected in favor of total tumor removal in every case in which surgery is indicated. (Arch Otolaryngol Head Neck Surg.
1990;116:1023-1025)
Facing
the increasing number of articles dedicated to hearing con¬ servation surgery in those with acous¬ tic neurinomas, we initiated a histopathologic study on the interface be¬ tween the cochlear nerve and the tumor. Indeed, histopathologic evi¬ dence of cochlear nerve involvement or invasion is, in our opinion, a very seriAccepted for publication March 30, 1990. From the Ear, Nose, and Throat Department (Head: Prof Dr Marquet), University of Antwerp, Belgium. Reprint requests to Ear, Nose, and Throat Laboratory (T6.17), University of Antwerp\p=n-\UIA,Universiteitsplein 1, B-2610 Wilrijk (Antwerp), Belgium (Dr Forton).
ous
argument against hearing conser¬
vation surgery. As mentioned by Marquet1 in 1986, several points have to be considered when discussing acoustic neurinoma surgery. Recent advances in medical imaging techniques have enabled us to visualize very small acoustic tumors with unprecedented accuracy. The neuro-otologist is therefore offered two options when confronted with a newly diagnosed acoustic neurinoma: to operate or not to operate. The latter attitude is especially indicated in el¬ derly people with slowly growing tu¬ mors, in cases of bilateral acoustic neurinomas (as observed in some par¬ ticular patients and more commonly in those with neurofibromatosis type II), and in patients with a single hearing ear.
Should the surgeon decide not to perform surgery, a meticulous followup stratagem is to be carried out to monitor the growth of the tumor. For¬ tunately, gadolinium-pentetic acid magnetic enhanced resonance imaging allows excellent visualization of small intracanalicular tumors. Surgery can thus be postponed and whatever may be left of useful hearing on the affected side can be saved until surgery be¬ comes indicated. However, should the surgeon decide to operate at once, there are several points worth considering: the surgical inaccessibility of the fundus of the in¬ ternal auditory meatus by way of the suboccipital approach; the biochemical alterations that occur in the perilymph fluid in the course of tumor develop¬ ment, as demonstrated by Silverstein and Schuknecht2; and the vascular le-
sions that may be caused either by tu¬ mor growth or during surgery. House and Hitselberger3 consider these vas¬ cular lesions to be one of the major causes of postoperative deafness de¬ spite the anatomic integrity of the cochlear nerve. Also worth consider¬ ing are the histopathologic aspects of acoustic neurinomas in relation to the cochlear nerve. Although benign, the schwannoma, which usually originates from the inferior branch of the vesti¬ bular nerve, actually tends to destroy adjacent nerves, first by crushing them and later by invading them. Invasion of the cochlear nerve by the acoustic neurinoma has been described by Neely and associates,4 5 Ylikoski et al,6'7 and Forton et al.8 Even facial nerve in¬ volvement has been described by Luetje et al.9 Our observations have shown that recurrent acoustic neuri¬ nomas have a mean growth rate of 4.2 mm/y in every dimension,1 a fact that is frequently overlooked by sev¬ eral authors. These figures are compa¬ rable with those of Wazen et al,10 who have found a mean growth rate of 3.8 mm/y. In this study, we are partic¬ ularly interested in the nerve-tumor interface, in order to establish any co¬ chlear nerve involvement or invasion. MATERIALS AND METHODS We have studied 10 intact medium-sized acoustic neurinomas that have been re¬ moved via the translabyrinthine approach. These tumors were removed by the senior authors (J.F.E.M. and F.E.O.) en bloc with the cochlear nerve, allowing not only the identification of all the nervous structures involved but also the serial sectioning of the specimens. In all 10 cases, macroscopically visible adhérences between the cochlear
Downloaded From: http://archotol.jamanetwork.com/ by a University of Michigan User on 06/19/2015
Fig 1.—The nerve-tumor interface (Masson trichrome stain, X166). Note the close relationship that exists between the cochlear nerve and the tumor. A cleavage plane cannot be iden¬ tified.
Fig 2.—Detail of the nerve-tumor interface (Masson trichrome stain, X646). The tumor mass is stained green, which is partly due to the large amounts of collagen that are present. Note the red myelin sheaths (arrows), surrounded by green streaks of perineural connective tissue, and note the absence of a clear cleavage plane between the nerve and the neurinoma.
Fig 3.—The nerve-tumor interface (Verhoeff's stain, X66). The tumor mass is stained ocherous, clearly showing red streaks of collagen. The perineural connective tissue is stained red as well and the myelin sheaths show an unspecific gray.
Fig 4.—Detail of the nerve-tumor interface (Verhoeff's stain, X646). Note again the absence of a cleavage plane. Note that the nerve-tumor interface is composed of tumor matrix and poorly organized whirling bands of collagen as well as nerve fibers.
Fig 5.—An immunohistochemìcally treated section (Dakopatts M762, 109, and P850) featuring the cochlear nerve (X166). The axons are stained brown, indicating the presence of neurotilaments. Nuclei are stained
purplish blue.
Fig 6.—Detail of the nerve-tumor interface (peroxidase-antiperoxidase method with antibodies to human neurofilaments [Dakopatts M762, Z109, and P850]) (X646). Note the presence of cochlear nerve fibers (arrows) past the assumed nerve-tumor interface. These nerve fibers are surrounded by the polymor¬ phous nuclei of the proliferating cell population, indicating inva¬ sion of the cochlear nerve by the tumor.
Downloaded From: http://archotol.jamanetwork.com/ by a University of Michigan User on 06/19/2015
and the tumor were present. The specimens were fixed in a buffered 4% formaldehyde solution and embedded in nerve
paraffin. Subsequently, they were
cut
on a
microtome (Leitz) in 6-Mm-thick sections. These were mounted on slides precoated with poly-L-lysine. Three different staining procedures were performed. First, Masson's trichrome stain was applied, because it is a quick and easy routine stain and because it stains myelin red, which is a useful characteristic. Sec¬ ond, Verhoeff's elastin stain was applied, because it yields a clear picture, rich with contrasts: the characteristic streaks of col¬ lagen, which are colored red are readily identifiable in the tumor mass, which is stained ocherous. The nerve fibers, how¬
particularly stained. Only perineural connective tissue is colored red by this method. Thus, any connective tissue septum that might exist between the co¬
ever, are not
chlear nerve and the tumor should be visu¬ alized in this manner. Last, we devised an immunohistochemical protocol using mon¬ oclonal mouse antibodies to human neurofilament protein (2F11) (Dakopatts M762) as primary antibodies, rabbit immunoglob¬ ulins to mouse immunoglobulins (Dako¬ patts Z109) as secondary antibodies, and monoclonal peroxidase-antiperoxidase
antibody complexes (Dakopatts P850). A 3,3-diaminobenzidine tetrahydrochloride solution was used as chromogenic agent. Thus, any present bundle of nerve fi¬ mouse
stained brown. A discrete Harris' was used as counterstain. The details of our staining methods are discussed in a previous article.8 bers
was
hematoxylin stain
RESULTS
Rather than searching for tumoral cells invading the cochlear nerve, we decided to look for cochlear nerve fi¬ bers past the nerve-tumor interface and to search for connective tissue structures separating the cochlear nerve from the tumor. In none of the 10 specimens were we able to discern any well-defined connective tissue struc¬ ture separating the cochlear nerve from the tumor, let alone a true sep¬ tum. There appeared to be only loose and ill-oriented streaks of collagen be¬ tween them (Figs 1 through 4). The immunohistochemical tech¬ nique, however, revealed the presence of cochlear nerve fibers beyond the nerve-tumor interface in six of the 10 specimens. The axons were surrounded by tumoral and normal Schwann cells (Figs 5 and 6). Conversely, some spec¬ imens showed penetration of tumoral
tissue between the cochlear bers (Fig 6).
nerve
fi¬
CONCLUSIONS Our findings indicate that tumor in¬ vasion of the cochlear nerve is to be expected in those cases where adhér¬ ences between the cochlear nerve and the tumor are present. So-called sharp dissection is, in our opinion, not indi¬ cated in these cases, since tumoral tis¬ sue will inevitably be left behind; even¬ tually this could lead to tumor recur¬ rence.
It is
our
firm conviction that total
tumor removal is of the utmost impor¬ tance and should remain the primary goal of acoustic neurinoma surgery,
when this implies removal of the cochlear nerve, and in certain cases of the facial nerve as well. Doing this, we have observed only two cases of tumor recurrence in 150 patients operated on between 1974 and 1988. In both pa¬ tients tumoral tissue had to be left be¬ hind for vital reasons. Our observations indicate that there is no correlation whatsoever between tumor size and the degree of hear¬ ing loss, nor between tumor size and tumoral invasion of the cochlear nerve. Total deafness has been ob¬ served even with small intracanalicular tumors. As for the quality of the hearing one would attempt to save, it may be rele¬ vant to consider that 95% of all pa¬ tients having an acoustic neurinoma already have poor hearing on the af¬ fected side when their tumor is first diagnosed." If good hearing is present on the contralateral side, is it really worth saving nonserviceable hearing and taking the risk of tumor recur¬ rence? On the other hand, if a very small tumor should be found in a patient with excellent bilateral hear¬ ing, we are convinced that this partic¬ ular patient would be far better off if surgery could be postponed and metic¬ ulous follow-up could be carried out. In conclusion, given the advances that have been made in the field of medical imaging techniques, we be¬ lieve that the indications for acoustic neurinoma surgery may need some re¬ consideration. Indeed, we advocate that total tumor removal be carried out whenever the decision is taken to even
operate for any
ing
on an
acoustic neurinoma. If, whatsoever, the hear¬
reason
must be
preserved,
an
expectant
attitude is recommended. Hence, in our opinion, there is no place for hear¬
ing preservation
surgery.
References 1. Marquet J. Consid\l=e'\rationssur le traitement chirurgical des tumeurs de l'angle ponto-c\l=e'\r\l=e'\belleux.In: Fraysse B, Lazorthes Y, eds. Neurinomes de l'acoustique: Acquisition et controvers-
Toulouse, France: Editions M\l=e'\dicalesPierre Fabre; 1986:43-51. 2. Silverstein H, Schuknecht H. Biochemical studies of inner ear fluid in man: changes in otosclerosis, M\l=e'\ni\l=e`\re'sdisease and acoustic neuroma. Arch Otolaryngol Head Neck Surg. 1966; es.
84:395. 3. House WF, Hitselberger WE. The neurootologist's view of surgical management of acoustic neuromas. Clin Neurosurg. 1985;32:214-222. 4. Neely JG, Hough J. Histologic findings in two very small intracanicular solitary schwannomas of the eighth nerve. Ann Otol Rhinol Laryngol.
1986;95:460-465. 5. Neely JG. Gross and microscopic anatomy of
eighth cranial nerve in relationship to the solitary schwannoma. Laryngoscope. 1981; the
91:1512-1531. 6. Ylikoski J, Collan Y, Palva T, Jauhiainen T. Cochlear nerve in neurilemomas. Arch Otolaryngol Head Neck Surg. 1978;104:679-684. 7. Ylikoski J, Palva T, Collan Y. Eighth nerve in acoustic neuromas. Arch Otolaryngol Head Neck
Surg. 1978;104:532-537.
8. Forton G, Moeneclaey L, Declau F, Marquet J. The involvement of the cochlear nerve in neurinomas of the eighth cranial nerve. Arch Otorhi-
nolaryngol. 1989;246:156-160. 9. Luetje CM, Whittaker CK, Callaway LA, Veraga G. Histological acoustic tumor involvement of the VIIth nerve and multicentric origin in the VIIIth nerve. Laryngoscope. 1983;93:1133-1139. 10. Wazen
J, Silverstein H, Norrel H, Besse B.
Preoperative and postoperative growth acoustic
rates in documented with CT scanHead Neck Surg. 1985;93:151\x=req-\
neuromas
ning? Otolaryngol
155. 11. Van de Heyning P, Marquet J, Declau F. The preservation of facial function in acoustic neuroma surgery. In: Proceedings of the Sixth International Symposium on the Facial Nerve. Amsterdam, the Netherlands: Kugler & Ghedim; 1988.
Editorial Footnote The authors report their findings on 10 specimens that included tumor and cochlear nerve. They found evidence that the tumor is intimately connected with nerve, rendering ineffective those proce¬ dures designed to remove tumor and pre¬ serve the integrity of the nerve. The authors conclude that preservation of hearing can¬ not and should not be realistic goals in most patients, but they fall short of providing the final answer. We need to know the incidence of tumor recurrence in patients who have had tumor removal with preservation of
tumor
hearing.
Downloaded From: http://archotol.jamanetwork.com/ by a University of Michigan User on 06/19/2015
Byron J. Bailey, MD Chief Editor
