Middle ear and mastoid surgery - Victor...

Middle ear and mastoid surgery

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Endomeatal sub corticalmastoidectomy.

Victor Slavutsky.

A-CONDITIONS FOR A GOOD SURGICALAPPROACH

A natural pathway should be used, takingadvantage of this natural space to obtain accessto the anatomical structures, without having tocreate a further surgical additional space. Theapproach should be as simple and direct asposssible.Healthy tissue should be respected to amaximum and further lesions should not becaused, beyond those caused by the pathologyitself.It should provide access and control to all thecompromised anatomy, since the cholesteatomais an invasive pathology that involves theanatomical recesses.It should try to preserve the function of all thestructures involved by the approach, and restoreit at the same time.

Endomeatal approach is treated as a current access pathway to thecholesteatoma, since it meets all the conditions of an optimal approach.The aim is to show the usefulness of this approach in removing thecholesteatoma, without reconstruction and integrating the mastoid cavity,conducting a semi-open technique through an autostatic ear speculum.

Aim

B-ENDOMEATAL APPROACH.REVERSETECHNIQUE.

Following a reverse way from the inner part ofthe external auditory canal (EAC), theEndomeatal Approach (EMA) starts in the atticusand ends in the mastoid.Just as a tympanic pocket retraction is treatedto prevent Cholesteatoma, with an EMAtympanostomy tube insertion ,surgery is carriedout when it is already present, even if it is asimple attical invagination, or a largecholesteatoma.It consists of starting the dissection from itsattical origin, up to the involved anatomical point,whichever that is, but always from the inner sideto the outside.This will enable, by the endomeatal pathway,controlling the extension of the approach, notto go beyond its size, preventing wideapproaches to solve small cholesteatomas, andat the same time, leaving a size cavity matchingthe cholesteatoma, with no need of extensive

Highligts


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incisions, that imply more injuries and theformation of an additional surgical space;understanding for this, the surgical space thatneeds and requires the surgical technique toeliminate the pathology. If this surgical spacematches the pathology itself is considered likea noninvasive surgery, meanwhile if it is not, isconsidered as a minimum or maximum invasivesurgery, depending on the extension of injuriescaused by the technique. The EMA is a minimuminvasive surgical technique.

C-SEMI-OPEN TECHNIQUE

Preserving the EAC posterior wall is not aguarantee of removal of the cholesteatoma, butit may also be the cause of a residualcholesteatoma, and moreover, it is notnecessary for the safeguard of hearing.Therefore, preserving it has always been acontroversial issue.This is not a closed technique(cwu), but neitheris an open technique(cwd), in any case, a semi-open technique, because the tympanic cavityis closed att ical ly, by conduct ing atympanoplasty, and the mastoid cavity remainsopen, for subsequent control.The characteristics of these two independentcavities are:

D-CHARACTERISTICS OF ENDOMEATAL MASTOID CAVITY

a-THE MASTOID CORTICAL BONE ISPRESERVED: To be able to conduct anappropriate epithelization, in a cavity with all itsbone perimeter preserved.

B-THE EXTERNAL ACCESS WHICHCOINCIDES WITH THE APPROACHPATHWAY: and not to practice an extrameatalapproach, to perform later an endomeatal cavitycontrol, as it happens in the conventionalretroauricular approach.This coincidence of cavity access with approachpathway enables performing a mastoid cavityrespecting the external auditory meatus, andthat is what renders the meatoplastyunnecessary, with a correct aeration, recurrencecontrol, and chance of cleaning the mastoidcavity.

Mastoid Cavity

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c-PRESERVING THE EXTERNAL AUDITORYMEATUS: the meatoplasty becomes necessarywhen the mastoid cortical bone has beenremoved. It is practiced as a response to amaximal size cavity, that extends from themastoid aditus and antrum, sinodural angle andretrosigmoid space, up to the superficial planesof skin and subcutaneous tissues by demolitionof the cortical bone, leaving an external limitthat is a muscular plane, which in turn delineatesa cavity in its maximal extension, and therefore,will require more ventilation and cleaning. Fig.6.329A mastoid cavity (MC) whose external limit islocated at the same level as the external auditorymeatus (EAM) (Fig. 6.330), through which its

control must be done, is impossible to cleanand aerate correctly, unless its access is widerand its size reduced, and this is what makesthe meatoplasty, and the use of muscularpedicles as necessary. Fig. 6.331But this is not necessary, when access to themastoid is made within the auditory meatus,respecting it, preserving the cortical mastoidbone as external wall, and starting the drillingin the anterior tympanosquamous suture, whichwill significantly reduce the size of the cavity,one of the main factors to integrate the mastoidcavity. Fig. 6.334

E-CAVITY INTEGRATION

Fig. 6.329. Transcortical approach creates a maximum Mastoid Cavity.CWU

Fig. 6.330. The dot line indicates the Mastoid Cavity external limit, located at the same level as the External AuditoryMeatus.CWD

Fig. 6.331. Meatoplasty and muscular pedicles are necessary for a wide access and reduced size of Mastoid Cavity

EAM

MC

Meatoplasty

Muscular pedicles


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Understanding by integrated mastoid cavity,the one that does not cause discomfort to thepatient, does not require the care of the surgeon,and does not need to be reconstructed. Thisapproach requires achieving the integration ofthe cavity, preserving the cortical bone, to thusobtain a cavity with a preserved bone perimeter,and with its aeration ensured trough thecommunication with the EAC, which is reachedby approaching the mastoid anteriorly, throughthe tympanic bone. Three factors must beconsidered to integrate the mastoid cavity:

a-SIZE

The cholesteatoma is an invasive pathologythat ends as far as its extension reaches.

It is not necessary to remove the smallest andfarthest cells, because the mucosa heals inthem spontaneously, as long as a good aerationis maintained (1). The removal of healthy mastoidcells does not insure recurrence.TheMACS(Mastoid Air Cell System) contributes tothe normal gas flow into the middle ear,(6)(7)soany surgical technique must be respectful asfar as possible,with this anatomical structure.TheMACS is not in the cholesteatoma origin,it onlysuffers the growth of it.There is no need todestroy the MACS as long as atelectasis isavo ided.Once the cor t ica l bone isdestroyed,there is no chance to preserve evenpartially the MACS,because the uncontrolledcells that remains under the soft tissues or infarthest anatomical place, becomes a potential

Fig. 6.332 Enlarged Eustachian tube function in closed technique.CWU

Fig. 6.333 Not enlarged Eustachian tube function. EMA semi-open technique

Ventilation Ventilation

aeration

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aspect of recurrent cholesteatoma or chronicmiddle ear efussion,and that is why thesemastoid cells must be radically eliminated. Thisfact is a consequence of the transcorticalapproach.The subcortical approach(EMA) preserves theMACS,according with the cholesteatomainvolvement,and entails an orderly developmentand regeneration of the mastoid,(13) with aproperly aeration,trying to prevent atelectasis(ventilation-aeration).Acquired cholesteatoma is not a mastoidpathology in its origin, so there is no need toremove healthy bone tissue unnecessarilybeyond the cholesteatoma itself, which wouldlimit mastoid drilling, and would significantlyreduce the size of the mastoid cavity and the

extension of thiscondition. This main factor is what will permitcavity-integration, as long as a proper aerationis kept.

b-VENTILATION AND AERATION

This technique puts into practice a concept ofventilation-aeration in two independent cavities.One, a tympanic cavity ventilation trough theEustachian tube in order to preserve the middleear pressure, and physiological function. Two,the mastoid cavity aeration through a naturaltube, which is what the EAC becomes whenthe cavity access and the approach pathwayare made to match. Ventilation involves directlythe Eustachian tube, but aeration does not.Pretending that an ear with Eustachian tubedysfunction could ventilate the tympanic cavity,and besides, the surgically widened mastoidcavity, are the pathophysiogenic causes of failurein closed techniques. Fig. 6.332The ear will express through fibrosis, adhesiveprocesses, effusion, and in the worst of cases,recurrence of cholesteatoma.This technique prevents the functionalenlargement of the Eustachian tube, which isthe origin of atelectasis, (8) and itsconsequences. Fig. 6.333

c-EPITHELIZATION

The last integrated factor is a correctepithelization, and this will depend on themanagement given to the soft tissues. The EMAdoes not apply external incisions, or dischargeincisions, and is characterized by a total respectfor soft tissues that correspond to the auricular

Fig. 6.334 EMA Cavity-Integration factors:start attical dissection (ad), preserve cortical bone (cb),match access with approach (aa)


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insertion, avoiding the use of mastoid retractorsand the use of muscular pedicles that wouldcompromise the vascular irrigation of thesetissues, causing an ischemia at precisely themoment when vascular input is most needed,i.e. the immediate post-operatory period.Any tissue will be better integrated if vascularirrigation is made by preserved vessels, thanby the newly formed ones.Moreover, advantages must be taken of thecharacteristics of this skin, which is differentfrom the rest, because it does not grow fromthe depth to the surface, but instead, does it bya medial development of 0.05 mm per day,which favors epithelization, as long as thevascular pedicles that nourish it are respected,and that the cavity is not excessively enlarged.A very large cavity will demand more aerationand epithelization, that will hardly permitintegration.

These three factors: size, aeration andepithelization, have to go together andsupplement each other, to be successful in theintegration, and for these three factors to act inagreement, it is necessary: Fig. 6.334

- To start the dissection at the origin of thecholesteatoma, to control its extension;

- To preserve the mastoid cortical bone, with asubcortical approach to achieve a uniform planeof epithelization;

- To match the access with the approach, toensure a direct aeration.

F-REPAIR AND RECONSTRUCT

The term repair is used, when the mastoidcortical bone is preserved, and the termreconstruction is used when it is not, becausedamages are more extensive.This is a technique that lowers the EAC posteriorwall only as needed, so as to avoid leavinginaccessible anatomical spaces, in the post-operative period.An open technique with well performed cavitydoes not require reconstruction. (2)EMA does not apply any kind of reconstruction,or obliteration, or extrusion, nor any other surgicaltechnique that does not allow the cavity visualcontrol in the post-operative period. The bestreconstruction is that one that is never needed.The visual control in a well performedendomeatal mastoid cavity enables watchingand controlling the ear response. Otherwise,complications may arise.

G-CAVITY PROTECTION

The EMA mastoid cavity has a double protection.Internal: by attically closing the tympanic cavity,thus preventing effusions in the middle earcompromising the mastoid cells.External: by preserving the protective role ofthe external auditory meatus. Fig. 6.335

H-CHARACTERISITICS OF THE TYMPANIC CAVITY

It will depend on the type of tympanoplasty tobe conducted, which in turn will depend on themucosa condition, the residual ossicular chain,tubal dysfunction, etc.Mostly, acquired cholesteatoma is an

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Fig. 6.336. EMA semi-opentechnique.Left ear.Postoperative atticaly closedTympanic Cavity withoutmeatoplasty.

Fig. 6.335. EMA semi-opentechnique.Left ear.Post-operative open Epytimpanic-Mastoid Cavity withoutmeatoplasty.


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epitympanic pathology (5),(9) in its origin andgrowing, and respects the mesotympanumdue to Proctor's tympanic isthmus. Dependingon an earlier diagnosis, often times there isnothing to do in the mesotympanum, except topreserve the undamaged structures; but if it isnecessary to act due to an osteitis of the wholeatticus, with ossicular and cavity involvement,the tympanic cavity is closed at the level of theFallopian canal, when there is no lateral atticalwall left. Fig. 6.336Although a flatter cavity is obtained, the atticusis under control (specifically the supratubalrecess), (3) and the final tympanoplasty resultis usually appropriate.

Surgical StepsAll the surgery is aided and carried out, througha two-valve autostatic ear speculum (mod. Dr.Prades), it is a two-hand surgery with usualsurgical instruments (Fig. 6.337), under localanesthesia in combination with intravenoussedation,if it is necessary,otherwise pre-operatory prescription(diazepam-metamizol)isenough.

SURGICAL POSITION

The head patient is not secured and rests inthe head-holder operating table, lower than thepatient's shoulders. Neck extension facilitatesthe procedure, while head rotation to theopposite side determines the patient surgicalposition, which must be free of any fixation, toallow the speculum to be placed in the optimalposition. It should also be repositioned as

needed throughout the procedure, sinceinadequate visibility, is probably the primaryobjection to the EMA.

SOFT TISSUES

The technique consists of practicing a hightympanotomy, with a U skin incision, fromapproximately 6 to 12, from the tympanic annulusto the end of the bony portion of the EAC, in itsjunction to the cartilaginous portion. All the skinfrom the posterior wall is freed, except in thosecases of small cholesteatomas,or wide EAC,were a tympanomeatal flap is confectioned,depending on skin condition.

HARD TISSUES

The drilling starts, taking as reference thetympanosquamous suture and the anteriortympanic spine, to continue the dissection tothe mastoid antrum and exteriorizing it,enlargingthe atticotomy upward and backward in thedirection of the tegmen, and later lowering it tothe tip of the mastoid, as much as necessary.

CHOLESTEATOMA SIZE

EMA recognizes three types,depending on thei n v o l v e m e n t . A t t i c a l f o r s m a l lcholesteatoma;attical-antral for mediumcholesteatoma and attical-antral-mastoidal forlarge cholesteatoma.In small cholesteatoma,only with atticalinvolvement,there is no need to totally removethe attical lateral wall.Partial demolition up tothe involved anatomical point is enough,takingcare that the lateral wall is a critical point forresidual cholesteatoma. To explore the anterior

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atticus and supratubal recess, the cog must beremoved, but does not imply sacrificing theossicular chain if it is not compromised, due tothe appropriate EMA visibility.When the eardrum is preserved and also theossicular chain,the skin of the posterior wall isfree or taking part of the tympanomeatalflap,once it is replaced covering the minimalcavity, a spontaneous repair of the posteriorwall,with a connective bridge protecting thecavity can be observed as a final surgical result.

In medium cholesteatoma,once the antrum isexteriorized is easily to find the limit of thecholesteatoma extension,but to continue or notit also depends on the cholesteatoma condition,ifit is encapsulate there is no need to advance,butif is not,antrostomy must be enlarged untilnormal mucosa is finded.

Small and medium cholesteatomas are a majorindication for the EMA,since is capable tomaintain the correspondence with thepathology.Limited approach to limited pathology.

Fig. 6.337 EMA surgical instrumental set


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In large cholesteatoma, the posterior and atticallateral wall are completely lowered, followingthe Fallopian canal up to the stylo mastoideanforamen, what it is termed as a "roundmastoidectomy", because the wider EAC isvirtually confused with the mastoid cavity..

FUNCTIONAL STEP

Conducting a tympanoplasty without the atticallateral wall and with preserved eardrum or graft,over the Fallopian canal,resuts in a flat tympaniccavity with a type lll solution(columellartympanoplasty-myringostapediopexy).Incholesteatoma surgery ,the stapes can be notinvolved and if it is ,the EMA allows to gentlyclean the oval window and expose properly thestapes,similar as an endomeatal stapedectomyprocedure.For those cases where the tympaniccavity is deeper,ossicular transposition with thepatient incus is the answer to maintain thecontact in between the stapes and theea rd rum.Meanwh i l e t he s tapes i savailable,functional results can have a goodchance,as surgeons already know.Thetechnique try to avoid the use of artificialprosthesis, using ossicles,cartilage andperichondrium from of the patient.If it is not possible a functional step,due tosevere lesions(chronic effusion, absence ofossicular chain,fixed footplate,mucosainvolvement,tubal dysfunction,etc.)the tympanic-mastoid cavity must remains open as a radicalsurgery treatment,trying to achieve a dry ear.One-stage surgery is practiced whenever ispossible.

DRESSING

The EAC and the cavity is packing withGelfoam,and external cotton and a gauze endsthe dressing. Perioperative antibiotics are notusual.

PITFALLS

FACIAL NERVE

The EMA is a safe surgical technique,becauseall the anatomical structures are under visualcontrol,including the facial nerve that can beperfectly identified in its tympanic segment,whichis the only visible portion of the Fallopiancanal.Coming from behind the EAC posteriorwall,the anatomical landmarks may disappear(e.g. the lateral semicircular canal and mastoidantrum in atelectatic ear),with the risk of facialnerve injury.Coming in front the posterior walland through the EAC the facial nerve is alwaysidentified with no need to drill.That is one of themain advantages of EMA,taking care that at thisp lace i s ve ry common to f i nd adehiscence.Mostly lesions of the facialnerve,takes place in the second genu and thethird segment,due to the poor visibility of theretro auricular approach.

PERILYMPHATIC FISTULA.ONLY HEARINGEAR

Another consideration in cholesteatoma surgeryis the presence of a perilymphatic fistula,mostof the times around the lateral semicircularcanal, overall if it is a only hearing ear.In thosecases EMA allows to explore the ear, andevaluate the risk of totally remotion, in order tolive a residual cholesteatoma and control it

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through the EAC access,without living a largemastoid cavity.

ANATOMICAL RECESSES

Residual cholesteatoma in the anatomicalrecesses,can be better eliminated also comingin front the posterior wall of the EAC,that comingfrom behind, specifically the supratubal recessand sinus tympani, that are involved in thecholesteatoma origin(3)(5). In all cases thesupratubal recess must be explored andexposed,and depending on the cholesteatomasize the surgical result can be just an epytimpaniccavity or epytimpanic-mastoid cavity.

TYMPANOPLASTY

Cartilage is not used to perform a tympanoplasty,due to its poor visibility and elasticity. One ofthe main principles of cholesteatoma surgerywith the EMA, is the capability to notice therecurrence in an earlier stage that enables toact accurately at the right moment, beforedefinitive lesions can take place.Cartilage is anexcellent tissue to repair the bone defect,especially in tympanic pocket retraction withlimited atticotomy of the posterior wall,it helpsperfectly to keep in place the restoredtympanomeatal flap.

PEARLS OF WISDOM

Even there is no need to use theotoendoscopes,surgeons with no experience inthis approach,but also, in those cases ofanatomical variability, the otoendoscope mightbe useful controlling and solving the lack of

visibility, that direct microscopic visualizationmakes difficult, and thus enables infiltrationcontrol of the cholesteatoma and act accurately,according to what the cholesteatomarequires,with limited drilling.During surgery,patient´s head and the autostaticear speculum,need to be repositioneddepending on the cholesteatoma anatomicalarea involved.At that point, surgeon also needto modify his surgical position,it does not implya big movement,but it must be enough spacearound him,and not to be tighten by assistantsor surgical instruments.

PROCEDURE

ADVANTAGES

The endomeatal approach is a procedure thatallows several advantages:Allows a direct access to the cholesteatoma,because it is a technique that does not seek forthe cholesteatoma, but finds it at its anatomicalor ig in. The dissect ion starts in thecholesteatomatous atticitis.Allows controlling the extension of the approachand not going beyond the size of thecholesteatoma; practicing a limited drilling, anda correspondence surgery with cholesteatomasize not creating further additional surgicalspace,respecting to a maximum healthy tissuesand for instance the MACS.Allows a better identification of the anatomicalstructures, since by acting endomeatally, thereis no need to drill to find the tympanic segmentof the facial nerve and is unnecessary toskeletonize the lateral sinus and the whole duraas well.Allows better control of the sinus timpany, stape


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cruras, anterior atticus, supratubal recess, andthe Eustachian tube orifice,(4) that conditionthe residual cholesteatoma and functional result.Allows to explore and control the only hearingear and evaluate the surgical risk,without leavinga large mastoidectomy.Allows minimal incisions, since they are onlylimited to the skin of the posterior wall of theEAC, in order not to compromise vascularirrigation and to favor an appropriateepithelization.Allows not having to practice meatoplasty andpreserving the external auditory meatus.Allows an internal and external protection ofthe mastoid cavity.Allows a ventilation of the meso-tympanic cavityand aeration of the epytimpanic-mastoid cavity,in order to prevent enlargement of theEustachian tube function.Allows integrating the cavity resulting fromsurgery.Allows preserving the auditory function andrestoring it if necessary, in one-stage surgery.Allows reducing the surgical time with localanesthesia or and intravenous sedation withan outpatient plan surgery, and interveningthose patients with severe associated pathology,that do not admit general anesthesia or geriatricpatients.Allows controlling recurrence and cleaning theepytimpanic-mastoid cavity in office control,avoiding secondary surgical look.Allows obtaining enough grafts; in this case,the tragal perichondrium; while with othersapproaches sometimes it is not sufficient,because approach injuries are more extensive.Allows the daily hygiene of the patient and waterrisk,due to the characteristics of the EAC, theintegrated mastoid cavity, and the protective

function of the preserved external meatus.Allows a hearing aid, because preserving themeatus stabilizes the prosthesis and facilitatesits adjustment.

DRAWBACK

The technique drawback is that it is a deep andnarrow surgical space, and any surgery mustbe performed trough the ear speculum, whichshould not be a drawback for ENT surgeons,who are used to work in these spaces becauseour specialty is focused on cavities, just as ithappens with endonasal or endolaryngealsurgery.

DISCUSSION

More than 30 years of experience with the EMA,(12) show a surgical technique that meets allthe conditions of an optimal approach.Compared with other surgical alternatives, EMAdoes not leave any unexplored anatomicalrecess as it could occur through the posteriortympanotomy mastoidectomy (e.g. sinustimpany and supratubal recess) (3) mostly thereason for failure, with an uncontrolled post-operative mastoid cavity, of the canal wall-upprocedure.EMA does not practice meatoplasty andtranscortical demolition, leaving a singleanatomical sequel: the integrated mastoidcavity.It prioritizes function over reconstruction in comparison with canal wall-downmastoidectomy and reconstructive techniques.It is a third choice surgical alternative, neitheropen nor closed, but a semi-open technique.(11)

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RESULTS

Our last surgical series,carried out in 156 patientsand controlled in a five years period, show 92%of good results, understanding as such, thepresence of a dry cavity, appropriatelyepithelized. Hearing results (preserved/improvedhearing) were correct in 72% of the cases, takingas reference pre-operatory audiogram.Complications displayed: Recurrence ofcholesteatoma: 3.9% .Wet ear: 2.9%, due totubal involvement. Deficient epithelization: 0.7%,that affected the mastoid tip. NeurosensorialInvolvement: 3%, affecting mainly highfrequencies.

POTENTIAL COMPLICATIONS AND HOW TOAVOID THEM

FACIAL NERVE

EMA is most of the time,a local anesthesiaprocedure and a transitory facial palsy can arisein the immediately post operatory period,due tothe over anesthetic dose,even it recovers in fewhours,the way to avoid it is to stop the anestheticinfiltration under microscope control,up to themoment when the inner skin portion of theEAC,begin the detachment from the bone,andalso changes its colour.

OTORRHEA AND RECURRENCE

Cronic otorrhea and recurrent cholesteatomais another hugely complication in the postoperative period,that can be avoided duringsurgery,lowering the posterior wall as much asneeded, until a good access to the mastoid

cavity and the supratubal recess isachieved.There must be always the outcometo clean the epytimpanic-mastoid cavity easilyand with a good aeration,otherwise otorrheaand recurrence, will not be solved.

FISTULA C.F.L

Cerebrospinal fluid leakage is not an importantcomplication with the EMA,due to meningealdura it is not an anatomical landmark and duraexposition is limited to the cholesteatomasize.Tegmen dehiscence can be a surgical findand depending on the size ,usually there isnothing to do but if a small tear appears as aconsequence of cholesteatoma removal, patientmust rest with an upper head position, and infew days leakage wi l l usual ly stopspontaneously.

POST OPERATIVE MANAGEMENT

The EMA allows a simpler post-operative period,due to the absence of external incisions, suturingand compression dressings.The EAC dressing must remains in place duringone month,and if it becomes wet, or extruded,then smoothly suction and antibiotic drops mustbe prescr ibed.Over tha t per iod o ftime,ephitelization must be controlled inoffice,just to avoid small granulomas that areeasily solved with gently suction,and helps toguide the epithelial regeneration.Control mustbe taken each two or three weeks.Long term results,encourage the control to oneor twice a year as much,depending on the newskin aspect and size of the integrated cavity.


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PRESENT AND FUTURE OF OTOLOGICALAPPROACHES

Specialties connected to otology have alreadyevolved into this type of approach:endo.Rhinology with endo-nasal surgery, andlaryngology with endo-laryngeal surgery. It isonly logical that it is so.Current clinical and radiological exploration (10),allows making an increasingly earlier stagediagnosis of cholesteatoma, and therefore, witha smaller size. This will lead to less aggressiveapproaches, so as to prevent a lag between thecholesteatoma injuries, and the surgicalperformance. The endomeatal approach,suggest a different systematization thanconventional surgery, in order to obtain anothersurgical and functional concept.Cholesteatoma is not a retro-auricular pathology,it has epytimpanic and anterior-attical in origin,and can be approached in that order.

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4. Hulka GF, McElveen JT Jr.A randomized, blinded study of canal wall upversus canal wall down mastoidectomydetermining the differences in viewing middleear anatomy and pathology.Am J Otol. 1998 Sep;19(5):574-8.

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Abraham [corrected to Seifert,

7. Doyle WJ.The mastoid as a functional rate-limiter of middleear pressure change.Int J Pediatr Otorhinolaryngol. 2007Mar;71(3):393-402.

8. Sadé J, Avraham S, Brown M.Ate lectas is , re t ract ion pockets andcholesteatoma.Acta Otolaryngol. 1981 Nov-Dec;92(5-6):501-12.

9. Sadé J.Retraction pockets and attic cholesteatomas.Acta Otorhinolaryngol Belg. 1980;34(1):62-84.

10. De Foer B, Vercruysse JP, Bernaerts A,Deckers F, Pouillon M, Somers T, CasselmanJ, Offeciers E.Detect ion of postoperat ive res idualcholesteatoma with non-echo-planar diffusion-weighted magnetic resonance imaging. OtolNeurotol. 2008 Jun;29(4):513-7

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12. Prades J, Slavutsky V.Modelated and Conserved tympanichomografts.Spanish,Pub.HomoinjertosTimpanicos Moldeados y Conservados. Revistabrasileira de orl. 1974 Vol. 40 Ed. 2 - Maio -Dezembro - (16º) 179 a 182

References.

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