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Extensive Intratemporal Cholesteatoma:

Surgical Strategy

Alexis Bozorg Grayeli, Isabelle Mosnier, Hani El Garem, Didier Bouccara, and

Olivier Sterkers

Department of OtolaryngologyHead Neck Surgery, Hopital Beaujon, AP-HP, Universite Paris 7,

Clichy, France

Objective: To evaluate the decisional elements in the surgicalstrategy for extensive intratemporal cholesteatomas.Study Design: A retrospective review of cases followed up

between 1985 and 1996.Setting: Tertiary referral center.Patients: Nineteen patients with temporal bone cholesteatomaextending beyond the middle ear limits and surgically treatedwere included. Preoperative imaging distinguished apical (8),infralabyrinthine (3), supralabyrinthine (3), retrolabyrinthine(1), and translabyrinthine (4) cholesteatomas.Intervention: Apical and supralabyrinthine lesions weretreated through a middle fossa approach. Infralabyrinthine andtranslabyrinthine locations were exposed through a subtotalpetrosectomy or a transotic route, depending on the preopera-tive audiovestibular status and labyrinthine destruction on com-puted tomography. The retrolabyrinthine lesion was ap-proached through a retrolabyrinthine route.Main Outcome Measures: Patients were assessed for postop-erative audiologic and facial functions and for recurrence oftumor.

Results: The facial nerve was neither rerouted nor interruptedduring surgery. Among the 12 patients with preoperative facialpalsy (FP), 5 cases of improvement (42%), 6 cases of stable

function (50%), and 1 case of mild deterioration (8%) wereobserved postoperatively. In patients without preoperative FP,facial function remained unchanged postoperatively. The laby-rinth could be preserved in three patients (16%), with postop-erative stable hearing function in two (11%), and a 40-dB meanauditory deterioration in one (5%). Complete macroscopic re-section was obtained in all patients. Two cases (11%) of post-operative recurrence were observed.Conclusion: The surgical strategy, principally based on cho-lesteatoma location and preoperative auditory function, yieldeda high rate of local disease control and facial function preser-vation. Key Words: Intratemporal cholesteatomaFacialnerveFacial palsy.

Am J Otol 21:774781, 2000.

Although chronic otitis media has dramatically de-creased in developed countries because of a better un-derstanding of its pathophysiology and its managementin early stages, the incidence of extensive cholesteatomasseems constant (1). These lesions remain a great surgicalchallenge with two principal goals: maximum functionalpreservation and minimum risk of recurrence. Many ap-proaches to cranial base lesions have been described,whose aim is to limit the risk to the adjacent neurovas-cular structures (25). Nevertheless, each approach car-

ries inherent anatomic limitations and should be tailoredto individual cases. Consequently, a precise preoperativeexamination determines the surgical strategy and thepostoperative functional results.

Because these cranial base lesions vary so greatly, a

simple and exhaustive strategic scheme cannot be pro-posed. However, major decisional factors can be high-lighted, and principal surgical attitudes can be deducedfor each type of lesion and location.

The aim of this retrospective study was to assess pre-operative decisional elements and to analyze surgicalstrategy in the light of the postoperative results and thepathophysiology of extensive cholesteatoma.

MATERIALS AND METHODS

A retrospective study of 19 patients undergoing surgery forcholesteatoma extending beyond the middle ear limits between1985 and 1996 in our department was undertaken.

Data from medical files were collected concerning medicalhistory, preoperative symptoms, neurologic and audiovestibu-lar clinical status, audiometric and vestibular test results, facialelectromyography (EMG) and blink reflex test results in casesof clinical abnormality or encasement of the facial nerve in

Address correspondence and reprint requests to Pr. Olivier Sterkers,Service dOto-Rhino-Laryngologie, Hopital Beaujon, 100 BoulevardGeneral Leclerc, F-92118, Clichy Ce dex, France.

The American Journal of Otology

21:774781 2000, The American Journal of Otology, Inc.

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cholesteatoma, and radiologic explorations, including com-puted tomography (CT) and magnetic resonance imaging(MRI). The type of approach, observations on cholesteatomaextent during surgery, the surgical sacrifice of neurovascularstructures, and the quality of macroscopic resection were alsonoted. Postoperative data were obtained regarding complica-tions, neurologic deficits, audiovestibular tests, and radiologic

appearance.Cholesteatoma locations and extensions assessed on preop-

erative CT were classified as apical, supralabyrinthine, infral-abyrinthine, retrolabyrinthine, and translabyrinthine accordingto Fisch and Mattox (4). This classification is summarized inFigure 1.

Facial function was clinically assessed according to Houseand Brackmann (6).

Mean hearing thresholds were calculated by air conductionaudiometry at 500, 1,000, and 2,000 Hz. These were consideredto be within normal limits when


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patients. A spontaneous nystagmus was associated withRombergs sign in two patients (10%). Preoperative ves-tibular caloric test results were available in 12 patients(63%), of whom 5 showed clinical signs (Table 3). Theyrevealed vestibular hyporeflexia in four patients (33%)and areflexia in eight patients (66%) on the affected side.Areflexia was associated with a labyrinthine fistula inone patient (5%).

Preoperative facial palsy was clinically observed in 12patients (63%). Facial function assessments are summa-rized in Figure 3. The facial nerve had been interruptedduring previous surgery in one patient. Facial electromy-ography or a blink reflex test was performed in ninepatients (47%). Among those, three (16%) had a delayedR1 response on the blink reflex associated with a normalfacial function (grade I). Mild degenerative EMG signswere present in two patients with grade I (11%) and 2with grade II facial function (11%). Severe degenerativeEMG signs were detected in a grade II (5%) and a gradeIV (5%) facial paresis.

Other preoperative neurologic symptoms included tri-geminal deficit in one patient (5%) and intracranial hy-pertension syndrome in two patients (10%), associatedwith abducens nerve palsy in one patient (5%).

Cholesteatoma location and extension onpreoperative imaging

The apical location was most frequently observed (8patients, 42%). In this group, cochlear fistula was presentin four patients (50%), and extension to the cerebel-

lopontine angle in one patient (5%). The greatest cho-lesteatoma diameter on CT axial views in this group was35 10.9 mm.

Infralabyrinthine lesions were observed in three pa-tients (16%). This location was associated with apicalextension in two patients and with labyrinthine involve-ment in two patients. The mean greatest diameter onaxial views in this group was 38 3.5 mm.

Supralabyrinthine lesions were observed in three pa-tients (16%). Preoperative imaging showed lysis of thetegmen tympani associated with cholesteatoma extensiontoward the middle fossa in all patients and a superiorsemicircular canal fistula in two patients. The meangreatest diameter on axial views in this group was 25 5.0 mm. The cholesteatoma diameter was smaller in su-pralabyrinthine than in apical or translabyrinthine lesions(p < 0.05).

Four cases (21%) of translabyrinthine extension withlarge labyrinthine destruction were observed. The meangreatest diameter on axial views was 36 4.8 mm.

One case of retrolabyrinthine location without destruc-tion of the otic capsule was observed (5%). The lesionmeasured 25 mm in its greatest diameter. The choleste-atoma extension followed retrolabyrinthine cells directlyto the posterior fossa dura in the presinusal region. Nointradural extension was observed.

Surgical approachesThe surgical approaches used in this series were

middle cranial fossa (MCF) with or without mastoidec-

TABLE 3. Preoperative audiovestibular function in different cholesteatoma extension types

Extension type

Preoperative hearing loss* (n 18)

Preoperative vestibular tests (n 12)Mild(25 to


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tomy, extended middle cranial fossa (EMCF) (4), retro-labyrinthine (5), subtotal petrosectomy with otic capsulepreservation, and transotic with otic capsule resectionaccording to Fisch and Mattox (4) (Table 4). Endoscopicassessment of the surgical resection was performed incases of bilobulated lesions and intracranial extension.

Factors influencing surgical strategy

Cholesteatoma location and extensionThe transotic approach was used in apical cholestea-

tomas in two lesions involving the entire otic capsule andencasing the intratemporal carotid canal. These lesionsextended to the cerebellopontine angle in one patient andthe internal auditory canal in the second. The EMCF orthe MCF approach was used in five patients with apicallesions and was combined with a radical mastoidectomy

in two patients. The EMCF or MCF approach was usedfor lesions extending upward through the supralabyrin-thine cell tract and the geniculate ganglion region withlimited or no involvement of the cerebellopontine angle.Destruction of the cochlea by the lesion was encounteredin two patients of this group.

Similarly, three cases of supralabyrinthine lesions with

neither apical nor internal extensions were operated onby the MF and EMF approaches.

Infralabyrinthine cholesteatomas were approached bya transotic route in two cases of anterior and internalextension through the infralabyrinthine cell tract associ-ated with cochlear destruction. In the third case, an an-terior extension of cholesteatoma limited to the posterioraspect of the vertical portion of the carotid canal wasapproached by a subtotal petrosectomy route.

All translabyrinthine lesions were approached by a

FIG. 2. Intratemporal cholesteatoma extension on preoperative imaging in four representative cases. A: Supralabyrinthine extensionwith cochlear destruction on frontal computed tomography (CT) view. B: Apical extension with carotid canal involvement on axial CT view.C: Infralabyrinthine extension with cochlear destruction on frontal CT view. D: Translabyrinthine extension with cerebellopontine angleinvolvement on axial magnetic resonance imaging in T1 sequence

777EXTENSIVE INTRATEMPORAL CHOLESTEATOMA

The American Journal of Otology, Vol. 21, No. 6, 2000


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transotic route because of the labyrinthine destructionand the large cholesteatoma diameters.

Preoperative auditory functionThe otic capsule was destroyed during surgery in 16

patients (84%), principally in those with preoperativesevere or profound hearing loss (Fig. 3). Moreover, fivepatients in this group (31%) had ipsilateral vestibularareflexia. The labyrinth was preserved in two patients(11%) with supralabyrinthine cholesteatoma 20- and 30-dB preoperative hearing loss and in one patient (5%)with an infralabyrinthine tumor and preoperative mixedsevere hearing loss.

Involvement of the cranial nerves by cholesteatomaThe facial nerve was encased in the lesion in fourapical (21%), one supralabyrinthine (5%), and one in-fralabyrinthine (5%) extensions. The nerve was involvedin its tympanic segment in five apical and supralabyrin-thine extensions (26%) and in its mastoid segment in theinfralabyrinthine lesion. The surgical approach did notnecessitate facial nerve rerouting, and the nerve was de-compressed without interruption in all these cases. Thegreater superficial petrosal nerve was encased in an api-cal lesion and was consequently interrupted (5%). Thetrigeminal nerve was involved in one case of apical cho-

lesteatoma (5%) but could be preserved during the sur-gical resection by an EMCF approach. No caudal cranialnerve involvement was observed in our series.

Postoperative resultsThe otic capsule was surgically preserved in three pa-

tients (16%). Two of these patients had a 20- to 30-dBconductive preoperative hearing loss associated with asupralabyrinthine cholesteatoma. Both underwent surgi-cal resection by the MCF approach. Postoperatively,hearing thresholds remained stable in one patient, and amean deterioration of 40 dB with mixed hearing loss wasnoted in the second. The third patient had an 80-dBmixed hearing loss associated with an infralabyrinthine

lesion preoperatively. A subtotal petrosectomy was per-formed. Hearing thresholds remained stable postopera-tively. The otic capsule was surgically removed in 10patients (53%) with profound hearing loss with largelabyrinthine destruction on preoperative CT, in 2 patients(11%) with large cochlear fistula with mild and severehearing loss, and in 3 patients (16%) with extensive le-sions associated with moderate and mild hearing losswithout evidence of radiologic labyrinthine destruction.

Preoperative and postoperative facial functions aresummarized in Figure 4. In seven patients, preoperativenormal facial function remained unchanged after sur-

TABLE 4. Surgical approaches used in different cholesteatoma extension types

Approach

Cholesteatoma location

Total (%)Apex Infralabyrinthine Supralabyrinthine Translabyrinthine Retrolabyrinthine

Middle fossa 2 2 (11)Exte nded middle fossa 3 1 4 (21)Middle fossa + mastoid 2 2 (11)Retrolabyrinthine 1 1 (5)Subtotal petrosectomy 1 1 (5)Transotic 3 2 4 9 (47)Total 8 (42%) 3 (16%) 3 (16%) 4 (21%) 1 (5%) 19

FIG. 3. Preoperative audiometric results; datawere available in 18 patients. Mean air conduction

hearing thresholds on 500, 1,000, and 2,000 Hz foreach subgroup (profound hearing loss, 85 dB;severe hearing loss, 65 to


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gery. In 12 patients with preoperative facial palsy, im-provement after nerve decompression was observed in 5patients (42%) (4 grade II to grade I, and 1 grade IV to

III). A deterioration of facial function from grade II to IIIwas noted (5%). In patients with severe or total facialparalysis (grade V and VI), the last follow-up assessmentremained unchanged.

Other postoperative deficits were one case of ipsilat-eral ninth cranial nerve paresis, which regressed at thelast follow-up examination, and one case of preopera-tive cerebellar syndrome, which persisted at the lastexamination.

Postoperative complications were limited to two casesof cerebrospinal fluid (CSF) leak through the incision,which was cured under conservative treatment.

Surgical resection was macroscopically complete inall cases. No residual mass was detected on postoperative

imaging. Two cases of recurrence (11%) were observedon systematic follow-up radiologic examination 2 yearsafter the surgery. These concerned two apical lesions,accompanied by severe hearing loss, excised by the MCFand EMCF routes and associated with mastoidectomy.These patients underwent surgical resection of their re-current lesions.

Information concerning postoperative professional ac-tivity was obtained in 15 patients. Among those patients,14 (93%) had resumed their previous activities at the lastfollow-up examination.

The decisional elements determining the type of sur-gical approach are summarized in Figure 5.

DISCUSSION

Cholesteatomas extending beyond the middle ear lim-its are not frequent: 15% of middle ear cholesteatomasinvolve the inner ear structures and are referred to asextensive in large series (7). Nevertheless, these lesionsraise individual diagnostic and therapeutic challenges inrelation to different types of extension.

The presenting signs of an extensive intratemporal

cholesteatoma may be misleading. Intact tympanic mem-brane was observed in 10% of our patients and in avariable proportion in other series, ranging from 0% (8)to 12% (9). Although some authors classify all thesecases as primary lesions (8), others have a more restric-tive definition of a primary cholesteatoma and add theabsence of otitis media, paracentesis, and temporal bone

trauma in the history as supplementary conditions (10).Intense headaches were experienced by four patientsin our series, associated with an apical lesion in threepatients (75%). This symptom has been reported as anearly sign of apical extension in other series (11,12). Theheadache may be explained by the meningeal tractionand irritation in contact with the lesion (12). Bacterialmeningitis was the presenting symptom in three of ourpatients (16%), all associated with superior extension ofthe lesion and disruption of the tegmen tympani. Bycomparison, the intracranial complication rate was evalu-ated as 1.2% in a series of 1,907 cholesteatomas (13). Inthe latter series, bacterial meningitis was the most fre-quent intracranial complication, and it was related to a

tegmen tympani disruption in 30% of patients (13).Sensorineural hearing loss, vertigo, and facial paresis

are the clinical signs indicating an extensive lesion in thepresence of a cholesteatoma. Their frequency in differentseries varies from 42% (14) to 100% (15) for sensori-neural hearing loss, from 7% (9) to 61% (16) for vestib-ular signs, and from 26% (9) to 83% (17) for facialdysfunction. As observed in our series and reported byother authors, facial paresis is frequently associated withapical extension of the lesion (12,17). This symptom isoften related to the involvement of the geniculate gan-glion and the tympanic segment of the nerve followingthe extension of the cholesteatoma to the supratubal re-cess from the attic compartment (18).

The decision process in the treatment of intratemporalcholesteatomas generally favors complete resection by awide exposure and preservation of facial function byavoidance of nerve rerouting when possible (8,19,20).Because of the variety of cholesteatoma locations, ex-tension types, and involved structures, different ap-proaches may be considered in each case. In our series,the selection of the approach type was mainly based onthe radiologic examination and the audiovestibular func-tional test results (Fig. 5). The preoperative radiologicexamination in extensive cholesteatomas is based onhigh-definition CT (20,21). Magnetic resonance imagingprovides important information in case of intracranialextension and on the probable histologic type of the le-

sion (20,22). In addition to confirmation of the diagnosis,the radiologic assessment of cholesteatomas distin-guishes several routes of extension (4,14,15). Theseroutes mainly follow petrous bone cell tracts, which offerlow resistance to the cholesteatoma outgrowth. The rela-tive frequency of different extension types varies in dif-ferent series. Sanna et al. (14) reported a predominanceof the perilabyrinthine extension type (43%) in theirpopulation. Charachon et al. (9) observed that the supral-abyrinthine extension was the most frequently encoun-

FIG. 4. Facial function grading at preoperative examination(open bars) and at last follow-up assessment (hatched bars) ac-cording to House and Brackmann (6).




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tered (47%) and that in this group, 80% of tumors in-volved the apex. Similarly, in our series, the apical ex-tension was the most frequently encountered. Reporteddifferences in extension type frequency may be due inpart to differences in recognizing extensions, becausemany tumors have complex extension routes and may beclassified in two different categories (9,15). In the apicalextension, the lesion follows the supralabyrinthine celltract from the attic and involves the greater petrosalnerve canal, or it invades the inferior perilabyrinthinecell tract from the mastoid cavity and progresses towardthe apex along the carotid canal (18,23). The latter typeof extension is the basis of another category, defined asinfralabyrinthine-apical by Fisch and Mattox (4). The

cochlear basilar turn may be involved in this type ofcholesteatoma progression (18), as was observed in threeof our eight apical lesions.

The supralabyrinthine type of extension eroding thetegmen tympani concerned the smallest lesions in ourseries. The MCF approach gave the best access to thelesion and permitted the preservation of the auditoryfunction in the absence of labyrinthine fistula in two ofthree patients. The translabyrinthine type of extensionconcerned patients with large tumors and ipsilateral pro-

found hearing loss in our series. The translabyrinthinelesion was approached through a transotic route in allpatients. This approach carried a low risk for the facialnerve. Moreover, it permitted surgical resection througha large access route and reduced the risk of recurrence inthese patients. Independently from the approach width,temporal bone endoscopy offers enhanced control duringsurgical resection, may avoid rerouting of the facialnerve, and diminishes the risk of CSF leak (24,25).

In addition to radiologic examination, audiometrictests helped determine the selection of the approach, be-cause the labyrinthine sacrifice concerned patients withprofound hearing loss in 82% of patients (Fig. 3). Ves-tibular function deficit represented an additional indica-

tion of inner ear involvement in patients with hearingloss, but it was not a determinant in the selection ofsurgical approach. Similarly, other cranial nerve deficitsdid not influence the type of approach in our series.

The frequency of postoperative recurrence is variableand cannot be directly compared between the differentreports because of the heterogeneity of cholesteatomasizes, the types of extension, and the different ap-proaches used (8,9,12). It varies from 0% (12) to 14%(9). In our series, recurrences concerned two apical le-

FIG. 5. Summary of surgical strategies in this se-ries. +, preserved auditory function; , destroyedauditory function; EMCF, extended middle fossaapproach; STP, subtotal petrosectomy; MF, middlecranial fossa approach; TO, transotic approach;RL, retrolabyrinthine approach.

780 A. B. GRAYELI ET AL.



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sions (11%) approached by the EMCF and MCF withmastoidectomy routes.

The poor auditory prognosis in our series was causedby frequent cochlear destruction by a large fistula. Al-though limited vestibular fistulas can be repaired withsatisfactory auditory results (27,28), involvement of thecochlea by the lesion has a poor prognosis and occurred

in the majority of our patients. Our postoperative com-plications were limited to two postoperative regressiveCSF leaks. Complications reported in the literaturemainly include CSF leak (7%) (9)and bacterial meningi-tis (8%) (16). Mortality rates ranging from 0.2% (3) to5% (9) are reported in large series, underlining the im-portance of the preoperative examination and the surgi-cal decision to the final outcome in patients with exten-sive intratemporal cholesteatomas.

In conclusion, the choice of surgical approach wasprincipally based on the cholesteatoma location, as as-sessed by CT scan and MRI, and the auditory function.The strategy favored complete macroscopic resectionand preservation of the facial nerve function. The poor

auditory prognosis was related to involvement of thelabyrinthine structures by the cholesteatoma in the ma-jority of our patients.

REFERENCES

1. House WF, Hitselberger WE. The transcochlear approach to theskull base. Arch Otolaryngol Head Neck Surg 1976;102:33442.

2. Fisch U, Fagan P, Valvanis A. The infratemporal approach for theskull base. Otolaryngol Clin North Am 1984;17:51352.

3. Wigand ME. The enlarged middle fossa approach to the cerebello-pontine angle: technique and indications. Rev Laryngol Otol Rhi-nol 1998;119:15962.

4. Fisch U, Mattox D. Microsurgery of the skull base. New York:Theime, 1988:12740.

5. Darrouzet V, Guerin J, Aouad N, et al. The widened retrolabyrin-

thine approach: a new concept in acoustic neuroma surgery.J Neurosurg 1997;86:81221.

6. House JW, Brackmann DE. Facial nerve grading system. Oto-laryngol Head Neck Surg 1985;3:18493.

7. Sheehy JL, Brackmann DE. Cholesteatoma surgery: managementof the labyrinthine fistula, a report of 97 cases. Laryngoscope1979;89:7887.

8. Atlas MD, Moffat DA, Hardy DG. Petrous apex cholesteatoma:diagnostic and treatment dilemmas. Laryngoscope 1992;102:13638.

9. Charachon R, Martin C, Gratacap B, et al. Temporal bone choles-teatoma. In: Tos M, Thomsen J, Peitersen E, eds. Proceedings ofthe Third International Conference on Cholesteatoma and MastoidSurgery. Amsterdam: Kugler & Ghedini, 1989:10818.

10. Zappia JJ, Wiet RJ. Congenital cholesteatoma. Arch OtolaryngolHead Neck Surg 1995;121:1922.

11. Flood LM, Kemink JL. Surgery in lesions of the petrous apex.Otolaryngol Clin North Am 1984;17:56575.

12. Glasscock ME, Woods CI, Poe DS, et al. Petrous apex cholestea-

toma. Otolaryngol Clin North Am 1989;22:9811003.13. Fisch U: Intracranial complications of cholesteatoma. In: Sade J,

ed. Proceedings of the Second International Conference on Cho-lesteatoma and Mastoid Surgery. Amsterdam: Kugler, 1982:36979.

14. Sanna M, Zini C, Mazzoni A, et al. Cholesteatoma of the temporalbone. In: Tos M, Thomsen J, Peitersen E, eds. Proceedings of theThird International Conference on Cholesteatoma and Mastoid

Surgery. Amsterdam: Kugler & Ghedini, 1989:107780.15. Martin C, Prades JM, Bertholon P, et al. Intrapetrous cholesteato-

ma. Rev Laryngol Otol Rhinol 1996;117:15763.16. Burggraaff B, Luxford WM, Doyle KJ. Neurotologic treatment of

acquired cholesteatoma. Am J Otol 1995;16:4805.17. Yanagihara N, Matsumoto Y. Cholesteatoma in the petrous apex.

Laryngoscope 1981;91:2728.18. Bartels LJ. Facial nerve and medially invasive petrous bone cho-

lesteatomas. Ann Otol Rhinol Laryngol 1991;100:30816.

19. Parisier SC. Management of cholesteatoma. Otolaryngol ClinNorth Am 1989;22:92740.

20. Sterkers JM, Sterkers O. Deep-seated destruction of the inner earby cholesteatoma. In: Sade J, ed. Proceedings of the Second In-ternational Conference on Cholesteatoma and Mastoid Surgery.Amsterdam: Kugler, 1982:3638.

21. Phelps PD, Wright A. Imaging cholesteatoma. Clin Radiol 1990;41:15662.

22. Mafee MF. MRI and CT in the evaluation of acquired and con-genital cholesteatomas of the temporal bone. J Otolaryngol 1993;22:23948.

23. Robert Y, Dubreuile F, Carcasset, S et al. Petrous bone extensionof middle-ear acquired cholesteatoma. Acta Radiol 1996;37:16670.

24. Rosenberg SI. Endoscopic otologic surgery. Otolaryngol ClinNorth Am 1996;29:291300.

25. Axon PR, Fergie N, Saeed SR, et al. Petrosal cholesteatoma: man-

agement considerations for minimizing morbidity. Am J Otol 1999;20:50510.

26. Proctor B. Surgical anatomy of the ear and the temporal bone.New York: Thieme, 1989:858.

27. Kobayashi T, Sakurai T, Okitsu T, et al. Labyrinthine fistulaecaused by cholesteatoma: improved bone conduction by treatment.

Am J Otol 1989;10:510.

28. Ars B, Claes J, Casselman J, Ars-Piet N. Preservation of cochlearfunction after extensive labyrinthine destruction. Am J Otol 1996;17:405.



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