Mastoidectomy and epitympanectomy - Vula - University of Cape Town

OPEN ACCESS ATLAS OF OTOLARYNGOLOGY, HEAD &NECK OPERATIVE SURGERYMASTOIDECTOMY & EPITYMPANECTOMY Tashneem Harris & Thomas LinderChronic otitis media, with or withoutcholesteatoma, is one of the more commonindications for performing a mastoidectomy.Mastoidectomy permits access toremove cholesteatoma matrix or diseasedair cells in chronic otitis media.Mastoidectomy is one of the key steps inplacing a cochlear implant. Here a mastoidectomyallows the surgeon access tothe middle ear through the facial recess.A complete mastoidectomy is not necessary;therefore the term anterior mastoidectomyis often used (anterior to the sigmoidsinus). A mastoidectomy is often an initialstep in lateral skull base surgery fortumours involving the lateral skull base,including vestibular schwannomas,meningiomas, temporal bone paragangliomas(glomus tumours), and epidermoidsor repair of CSF leaks arising from thetemporal bone.Definition of CholesteatomaCholesteatoma is a chronic middle earinfection with squamous epithelium andretention of keratin in the middle earand/or temporal bone with progressivebone erosion. A middle ear atelectasis doesnot retain keratin, although it also revealsskin in the middle ear space due to theretraction pocket.Aims of Cholesteatoma SurgeryEradication of disease and preventingresidual diseaseImproving middle ear ventilation andpreventing recurrent diseaseCreating a dry, self-cleansing cavityReconstitution of the hearing mechanismTypes of MastoidectomyThe terminology around mastoid surgery isnot uniform. In fact, several terms are usedto describe the different types ofmastoidectomy as summarized in Table 1.Table 1: Types of mastoidectomyCanal wall upmastoidectomyCombined approachIntact canal wallmastoidectomyClosed techniqueCanal wall downmastoidectomyRadical mastoidectomyModified radicalmastoidectomyOpen techniqueFront-to-back mastoidectomyAtticoantrostomyOpen mastoidoepitympanectomyOne of the problems is that theterminology does not in fact entail specificinformation about what was done either tothe middle ear or the mastoid. It is theauthors’ preference to use the termsopen/closed mastoidoepitympanectomyand to state separately whether atympanoplasty or ossiculoplasty was donee.g. left open mastoidoepitympanectomyand tympanoplasty type III.The most commonly used terms for canalwall down mastoidectomy are radical ormodified radical mastoidectomy. Theclassical radical mastoidectomy is notfavoured by the authors as it results in alarge cavity which frequently dischargesand therefore does not satisfy the ultimategoal of mastoid surgery which includeshaving a “trouble free” cavity.The method of open and closed mastoidoepitympanectomyas described in this textis standard. Common to both open andclosed mastoidoepitympanectomy is thebony work involving the mastoid cavity. It

involves first identifying the importantlandmarks (= skeletonization = leaving athin shelf of bone covering the importantstructure) before removing the disease andmaximum exposure for completeexenteration of the disease.A closed technique, keeping the posteriorcanal wall in place and working transcanal(following a proper canalplasty) andtransmastoid (with or without posteriortympanotomy) is suggested in moderatelypneumatized and ventilated ears withsufficient exposure to remove the disease.Open mastoidoepitymanectomy involvescomplete exenteration of the mastoid aircell system (e.g. retrosigmoid, retrofacial,perilabyrinthine) and the epitympanum(removal of incus and malleus head,exenteration of the supralabyrinthine andsupratubal cells) and is indicated in poorlypneumatized and ventilated ears withlimited access and exposure. It requiresskeletonization of the facial nerve alongthe mastoid segment to lower the posteriorcanal wall to the facial nerve (still coveredby bone). The mastoid area behind thefacial nerve is later obliterated with amuscle flap to keep the volume of the finalcavity low and avoid discharging ears.The other method of “canal wall down”mastoidectomy is front-to-back mastoidectomy.Surgeons may elect this approachwhen it has been decided in advance thatthe canal wall will be taken down e.g. witha sclerotic mastoid. The principles of thismethod are that one follows the disease,i.e. the mastoid is only opened as far as theextent of the disease. The only problemwith this approach is that one has to becertain that there are no more mastoid cellspresent as incomplete exenteration willcause a discharging cavity.Surgical TerminologyCanalplasty: Enlargement of the externalear canal while avoiding injury to thetemporomandibular joint anteriorly and themastoid air cells posteriorly (Video)Epitympanotomy: Partial removal of thelateral wall of the attic to expose the headof the malleus and incus in order to removesoft tissue pathology in the epitympanum;the ossicles are left in placeEpitympanectomy: Removal of the lateralwall of the attic, with removal of the incusand head of malleus and with exenterationand exteriorisation of supralabyrinthinecellsCortical mastoidectomy: Also referred toas simple mastoidectomy, it entailsexenteration of the mastoid air cells and isperformed most commonly for acutemastoiditisPosterior tympanotomy: Drilling away ofthe bone between the pyramidal (mastoid)segment of the facial nerve, and the lateralbony canal and chorda tympani resulting inaccess to the middle ear from the mastoid.Posterior tympanotomy may be done forthe following reasons:As part of a closed mastoidoepitympanectomy(combined approach)when removing cholesteatomaTo remove pus from the region of theround window in acute bacterial orviral otitis media with sensorineuralhearing lossTo provide access to the promontory orround window in cochlear implantsurgery and access to incus or roundwindow with insertion of the VibrantSoundbridgeClosed mastoidoepitympanectomy withtympanoplasty: This includes acanalplasty, mastoidectomy, epitympanec-2

tomy, (posterior tympanotomy) andtympanoplasty. The external bony canal ispreserved. The drawback of this approachis the limited view into the anteriorepitympanum and the sinus tympani incases of limited pneumatisation andcholesteatoma formationOpen mastoidoepitympanectomy (withobliteration): This involves the radicalexenteration of the tympanomastoid tractswith exteriorisation of the surgical cavity,and lowering of the posterior bony canalwall to the level of the skeletonised facialnerve. In order to reduce the size of thecavity, especially with moderately-wellpneumatised mastoids, the mastoid tip isremoved and a myosubcutaneous occipitalflap is created to reduce the size of thecavity. Meatoplasty is routinely performed.Open/Closed MastoidoepitympanectomyAge is not a limiting factor as childrenbehave equally well with open MET’s asdo adult patients!Deciding whether to do open or closedcavity mastoidoepitympanectomy maydepend on the factors listed in Table 2.Applied AnatomyKnowledge of middle ear and temporalbone anatomy is vital to understanding theconcepts of surgical management. It isimperative to practise the surgery and learnthe 3-dimensional temporal bone anatomyin a temporal bone laboratory. Theimportant landmarks and structures will behighlighted with the surgical steps.Table 2: Indications for closed vs. opencavity mastoidoepitympanectomy (MET)Factor Closed MET Open METExtent ofdiseasePneumatisationAerationFollow-upLimitedPrimary surgerywith sufficientspaceGoodpneumatisationAir in middleear and mastoidair cellsGood 5 yearfollow-upanticipatedPreoperative assessmentHistoryLargecholesteatomaLabyrinthinefistulaOthercomplicationsRecurrentcholesteatomaafter previousclosed METPoorpneumatisationGlue in middleearGranulation tissuein mastoid aircellsBleedingPoor 5 yearfollow-upanticipatedPatients with chronic ear diseasefrequently have a longstanding history ofhearing loss or chronic otorrhoea. It isimportant to establish whether there is ahistory of previous surgery. Foul smellingotorrhoea is a clear hint of cholesteatoma.OtomicroscopyThis is an important means to determinethe presence of cholesteatoma and it helpsto define the extent of disease. The earshould be thoroughly cleaned of secretionsand debris. Findings may include a3

etraction pocket with accumulation ofkeratin in the attic or in the posterosuperiorquadrant of the tympanic membrane,granulation tissue or a polyp (Figures 1 &2). A polyp “signals” an underlyingcholesteatoma.Pneumatic otoscopyThis should be routinely performed todetermine the presence of a positive fistularesponse. A negative response, howeverdoes not exclude a fistula.AudiologyPure tone audiometry should be obtainedwith air and bone conduction, and alsospeech reception thresholds should bedetermined. These should be done within 3months of surgery.High resolution CT (HRCT) scanFigure 1: Right ear: Granulation tissue inthe attic and a retracted tympanicmembrane; bony erosion of the superiorcanal wall; lenticular and long process ofthe incus is present with retraction ofposterosuperior quadrant of tympanicmembrane; tympanic membrane is indirect contact with the stapessuperstructure (myringostapediopexy)Figure 2. Right ear: Polyp obscuringposterosuperior retraction pocketAll patients undergoing surgery shouldideally have preoperative imaging asHRCT (0,5mm cuts) is invaluable for bothfor diagnosis and surgical planning.Preoperative counselling is mandatorywith any surgical procedure. Informationgained from the CT scan enables thesurgeon to discuss in detail with the patientwhat the surgical goals and risks of thesurgery are, as well as the possibility of astaged procedure and follow-up routine.Diagnostic value of HRCTSpecificity is poor with mass lesionswhich may include granulation tissue,secretions, cholesterol granuloma or aneoplasmIt therefore cannot be used todefinitively diagnose cholesteatoma,which remains a clinical diagnosisbased on otoscopic findingsFindings highly suggestive ofcholesteatoma include the presence ofan expansile soft tissue mass; retractionof the tympanic membrane; erosion ofthe scutum; erosion of the ossicles;sharp erosion of bone; extension of thelesion medial to the otic capsule; anderosion of the tegmen tympani4

Surgical planning with HRCTHRCT of the temporal bone is theotologist’s road map and one should have asystematic approach when evaluating theCT scan. The decision whether to do anopen or closed cavity operation depends onthe degree of pneumatisation andventilation of the temporal bone and extentof disease, all of which can be determinedon HRCT. Axial as well as coronal imagesare needed for preoperative evaluation andshould always be in the operating theatreand visible to the surgeon as intraoperativereference (and not in the patient’s chart!)CT scan checklist1. Pneumatisation: The temporal bonemay be well-pneumatised, may havereduced pneumatisation, or besclerotic. This gives importantinformation about what the eustachiantube function during the first 4 years ofthe patient’s life was like. It isimportant to assess the pneumatisationof the petrous apex as well. Poorventilation favours an open cavityprocedure2. Ventilation: This is assessed by theaeration of the middle ear and mastoidair cells. Opacification of the middleear or mastoid cells suggests poorventilation of the middle ear cleft. Thisgives the best information abouteustachian function at the present time.Poor ventilation of already-impairedpneumatised cell tracts favours anopen cavity procedure3. Ear canal: Evaluate the thickness ofthe bone anteriorly and posteriorly.This is important when one needs to doa canalplasty as the anterior relation ofthe tympanic bone is the temporomandibularjoint and posteriorly aremastoid air cells. These should not bebreached when doing a canalplasty4. Size and presence of emissary vein: Alarge emissary vein can causetroublesome bleeding if notanticipated!5. Sigmoid sinus and its relation in themastoid cavity: In children the sigmoidmay be very close to the lateral surfaceof the mastoid; in adults a sigmoidsinus malformation may only beappreciated on preoperative CT scan.When the sigmoid sinus lies veryanteriorly in the mastoid cavity it maybe difficult to perform a posteriortympanotomy due to very limitedexposure. In revision surgery, it isimportant to assess whether thesigmoid sinus has been exposed orwhether it is still covered by bone. Ifthe sigmoid sinus has been exposed atprevious surgery, it will be coveredwith scar tissue which becomesdifficult to elevate thus riskingbreaching the sinus when elevating theperiosteal flap6. Jugular bulb: Is it high-riding (up tothe level of annulus)? Is it dehiscent?7. Carotid artery: Is there dehiscence,especially at the level of the eustachiantube?8. Tegmen tympani: What is the shape ofthe tegmen? Is it flat or does it slopeupwards with cells lying medial to it?Is it low-lying? Is it dehiscent? A bonydefect of the tympanic tegmen oranterior wall of the epitympanumshould raise the suspicion of anencephalocoele or cholesteatomaextending into the middle cranial fossa.This requires further imaging in theform of an MRI9. Facial nerve: The tympanic segmentmay be dehiscent, especially inchildren or in the presence ofcholesteatoma. In cases of revisionsurgery, it is important to knowwhether the facial nerve has been leftexposed in an open cavity whenelevating the tympanomeatal flap5

10. Is there a fistula of the lateralsemicircular canal?11. Extent of disease: Does it only involvethe mesotympanum or does it extendfurther into the mastoid cavity? Is thepetrous apex involved?12. Status of ossicular chain: Are theossicles present or have they beeneroded?When approaching the mastoid tip theskin incision follows the skin tensionlines which run directly inferiorly (notcurved) towards the neckPreoperative preparationDrugs: A single intravenous dose ofamoxicillin with clavulanic acid and ananti-emetic is given preoperatively.However antibiotics are unnecessary witha dry ear, even in presence of acholesteatoma. Low dose subcutaneousheparin is recommended to prevent deepvein thrombosis with prolonged surgery.Positioning: The patient lies supine withthe head rotated away from the surgeon.Avoid overextension in children; Down’ssyndrome is associated with atlantoaxialsubluxation.Facial nerve monitoring: Avoid longactingmuscle relaxants so that the facialnerve can be monitored.Figure 3. Postauricular skin incision(left ear)Elevate the skin flap towards theexternal ear canal. Cut through thepostauricular muscle to reach thecorrect plane just superficial totemporalis fascia. A large rake can beused to retract the pinna forward(Figure 4)For adequate exposure the superiorincision has to be made at the 12o’clock position relative to the bony earcanal (Figure 4)Closed MastoidoepitympanectomySkin Incision and flapInfiltrate the area of the postauricularskin incision as with local anaesthetic(lidocaine 1% and adrenaline diluted to1:200 000)Make a curved skin incision about1,5cm behind the postauricular sulcuswith a #10 blade extending from justabove linea temporalis to the mastoidtip. Do not place the incision in thepostauricular sulcus (Figure 3)Figure 4: Flap elevated in plane justsuperficial to temporalis fascia6

Periosteal flapAn anteriorly based periosteal flap isdeveloped, about 1,5cm in length(Figure 5)CanalplastyIf there are any bony overhangs acanalplasty is performedA canalplasty should always be donefirst as it defines the anterior limit ofyour mastoidectomyFor a detailed description of thesurgical technique readers arereferred to the canalplasty chapter orcanalplasty videoThe entire annulus should be visiblewith one view of the microscopefollowing canalplasty (Figure 7)Figure 5: Periosteal flapA periosteal raspatory is used toelevate the flap from the bone until thespine of Henlé and the entrance tobony canal come into view (Figure 6)Figure 7: Completed canalplasty withentire annulus visibleElevation of tympanomeatal flapFigure 6: Raspatory used to elevateflap until spine of Henlé and theentrance to bony canal come into viewA sharp towel clip can be placed on theperiosteal flap at the level of the earcanal to retract the pinna forwardIn an adult two self-retaining retractorsare placed between the skin edges andsoft tissue for exposure; one selfretainingretractor is usually sufficientin a childThe posterior meatal skin flap iselevated towards the annulus using amicroraspatory in one hand and a pieceof ribbon gauze which has been soakedin adrenalineThe microsuction is never placeddirectly onto the meatal skin for risk ofinjury of the skin flapElevate the annulus from its sulcusaway from the pathological area e.g. aposterior retraction pocket wouldpreclude entering the middle ear at thelevel of the posterior tympanic spine asthis would breach the cholesteatomasac (Figure 8)7

eflect periosteum posteriorly whereyou may encounter an emissary vein,and inferiorly to the mastoid tip12345Figure 8: Tympanomeatal flap andannulus have been elevated and middleear is entered below the pathologicalareaInspection of middle earThe middle ear in Figure 8 has beenentered at 6 o’clock after excluding adehiscent jugular bulb on CT scanDefine the extent of the disease in themiddle ear and around the ossicularchainFigure 9: Surface markings of left ear:Temporomandibular joint (1); root ofzygoma (2); external ear canal (3);suprameatal spine (4); mastoid tip (5);Macewen’s triangle (6); opening ofemissary vein (7)67Division of incudostapedial jointTo avoid causing a sensorineuralhearing loss when working in theepitympanum, the incudostapedial jointis divided using a small joint knifeAntrotomy and MastoidectomyNote: Always perform antrotomy and/ormastoidectomy after the canalplasty hasbeen doneThe principal surgical landmarks arelinea temporalis superiorly, the bonyear canal and spine of Henlé anteriorlyand the mastoid tip inferiorlyIdentify and expose the surgicallandmarks (Figures 9, 10)Using the mastoid raspatory, reflect theperiosteal tissue superiorly in order toexpose the linea temporalis; thenFigure 10: Completed bony exposureIdentify Macewen’s triangle which issituated posterosuperiorly to theexternal auditory canal. It is boundedanteriorly by the Spine of Henlé andapproximates the position of theantrum medially (Figure 10, 11)AntrotomyA common mistake is to search for theantrum very low, thus endangering thefacial nerveThe safest way to finding the antrum isto follow dura8

The tegmen tympani marks the superiorlimit of the dissectionStart drilling above linea temporalisFigures 11, 12)to avoid touching the ossicles whichwould induce sensorineural hearinglossLSSCDural plateFigure 11: Yellow lines indicate whereto drill along; red star indicates whereto commence drillingFigure 13. Dural plate and lateralsemicircular canalThe body and short process of incusare the next landmarks one encounters;the incus is often first identified by itsrefraction in the irrigation fluid (Figure14)Medial to the incus the tympanicsegment of the facial nerve (VIIn) isidentified (Figure 14)Figure 12: Drilling along lineatemporalisExpose tegmen tympani (middlecranial fossa dural plate); it isidentified by a change in colour of thebone and change in the pitch of theburr (Figure 13)Always skeletonize the dura of themiddle cranial fossa (dura seen shiningthrough thin layer of bone) and followthe dural plate of the middle cranialfossa in an anteromedial directionThe lateral semicircular canal isencountered next (Figure 13)The direction of the drilling now has tobe changed to a medial-to-lateral actionFigure 14. Postero-anterior viewthrough antrotomy and aditus adantrum into epitympanumIncusBodyShort processVIInDural plateLSCC9

Drilling tipsAvoid keyhole surgery; work through awide spaceThe tip of the drill should always bevisibleNever drill behind edges of boneDrilling should always be parallel toany structure you are trying topreserve e.g. facial nerve, sigmoidsinusWhen drilling deeper in the mastoidcavity the burr needs to be lengthenedOne cannot lengthen a cutting burr asthis will cause the drill to jump withthe risk of injuring structures (Figure15)MastoidectomyFollow the sinodural plate posteriorlyup to the sinodural angle, which is thearea between the sigmoid sinus andduraLike the dural plate, the sinus plate isidentified by the change in colour ofthe bone and a change in the pitch ofthe burrSkeletonise the sigmoid sinus; do notexpose the sigmoid sinus, but leave acovering of bone over the sinus.(Figure 17)Figure 17: Sigmoid sinus, sinoduralangle and dural plateDural plateSinoduralangleSigmoidsinusFigure 15: Correct length of a cuttingburr in the drillTherefore if it is necessary to lengthenthe burr, then change to a roughdiamond or diamond burr (Figure 16)Figure 16: A diamond burr can belengthened in order to safely drilldeeper in the mastoidThe lateral and posterior semicircularcanals are identified and theretrolabyrinthine air cells areexenteratedNext identify the facial nerveThe superior landmarks for the mastoidsegment of the facial nerve are thelateral semicircular canal, to which thefacial nerve runs anteroinferiorly, andthe posterior semicircular canal, towhich the nerve runs 2,5mm anteriorto. The figure below is a cadaverdissection which demonstrates therelationship between the lateralsemicircular canal, posterior semicircularcanal and facial nerve (Figure18)10

DuraSCCSigmoid sinusIncusLSCVIInPSCCFigure 18: Relations of VIIn to shortprocess of incus; superior semicircularcanal (SCC); lateral semicircularcanal (LSC); posterior semicircularcanal (PSC); dura; and sigmoid sinusFinding the facial nerve along digastricridge and the stylomastoid fibers is avery safe way of identifying the facialnerve away from any mastoidpathologyIt requires proper drilling techniqueand can easily be learned in thetemporal bone laboratoryWhen searching for the mastoidsegment of facial the nerve, a large (4-5mm) diamond burr is usedUse ample irrigation to prevent thermalinjury to the nerveThe digastric ridge is the distallandmark for the mastoid segment ofthe facial nerve. It is a smooth convexbone found close to the mastoid tip.The digastric ridge can be difficult tofind in poorly pneumatised temporalbones. Once the sigmoid sinus hasbeen skeletonised the digastric ridge isfound by drilling inferiorly to the sinus,close to the mastoid tip, from laterallyto medially, in a horizontal direction.Periosteal fibres run anteriorly from thedigastric ridge in a plane perpendicularto the ridge. The facial nerve can belocated proximal to the stylomastoidforamen by drilling the last of theseperiosteal fibres. One often encountersthe sensory branch of facial nerve(which innervates the posterior wall ofthe external auditory canal and aportion of the tympanic membrane)just above the stylomastoid foramen.Skeletonise the nerve by drilling in awide plane between the lateralsemicircular canal proximally and thestylomastoid foramen distally, workingfrom anteriorly to posteriorly (Figure19)Figure 19: Distal portion of mastoidsegment of facial nerve (arrow) isidentified close to digastric ridgeAlways drill parallel to the course ofthe facial nerve and use lots of waterfor irrigation. Drill along the lateralaspect of the nerve; do not drill behindand medial to the fallopian canalWatch out for an early take-off of thechorda tympani close to thestylomastoid foramenOnce the facial nerve has beenidentified, the retrofacial cells can beexenteratedPosterior tympanotomyThe facial nerve is skeletonised leavinga thin shelf of bone covering the nerveIt is followed proximally towards itspyramidal segment, just inferior to thelateral semicircular canalThe facial recess is approached bydrilling away the bone situated11

etween the pyramidal segment of thefacial nerve posteriorly, the chordatympani, and the fossa incudissuperiorly (Figure 20)IncusChordaPTympanotomyVIInFigure 21: Direction of drilling withepitympanotomy or epitympanectomyFigure 20: Landmarks for posteriortympanotomy are VIIn, chorda tympaniand short process of incusIn the absence of disease in the facialrecess, the stapes superstructure isvisible through the tympanotomyFor removal of cholesteatoma in facialrecess one has to work from both sidesof the intact posterior external auditorycanal wallEpitympanotomyIf the cholesteatoma does not extendsignificantly into the epitympanum, anepitympanotomy (atticotomy) isperformedThis involves exposure of the head ofthe malleus and the incus to removesoft tissue from the epitympanumThe lateral wall of the epitympanumor attic is removed with a diamondburr; drilling is commenced at 12o’clock relative to the ear canal, takingcare not to make drill contact with themalleus or incus which is immediatelymedial to the outer attic wall, or tobreach the dural plate above (Figure21)EpitympanectomyThis is indicated when cholesteatomaextends medial to the ossicles oroverlies the lateral semicircular canal;in cases of bony erosion of the ossiclesdue to cholesteatoma, the ossicles needto be removedOnly recently, KTP laser evaporationof cholesteatoma matrix has beendiscussedThe incus is removed by mobilising itwith a 2,5mm. 45° hook and rotating itlaterally, taking care not to injure theunderlying facial nerveThe malleus head is severed with amalleus nipper applied across its neck.The malleus nipper is held anteriorlybetween the thumb and index finger tostabilise it when the malleus head isdividedThe head of the malleus is removedleaving the tensor tympani tendonintactClear cholesteatoma from theepitympanumDetailed knowledge of facial nerveanatomy is crucial to avoid injury tothe nerve when drilling or removingcholesteatoma in the epitympanumThe tympanic and labyrinthinesegments and geniculum all lie in this12

very confined space and may bedehiscentThe tympanic segment lies in the floorof the anterior epitympanic recess (Fig22)TTVIInCogStRCPTTympETFigure 22: Anatomy of anteriorepitympanic recess: Facial nerve(VIIn); Tegmen tympani (TT); Cog;Supratubal recess StR; Cochleariformprocess (CP); Eustachian tube (ET)The cochleariform process is a fairlyconsistent landmark and the nerve liesdirectly superior to it; the semicanal ofthe tensor tympani is sometimesmistaken for the facial nerve; howeverthis canal ends at the cochleariformprocess (Figure 22)The cog is a bony process in theanterior epitympanum which extendsfrom the tegmen tympani and points tothe facial nerve (Figure 22)Figure 23 above shows the geniculateganglion and greater superficialpetrosal nerve once the Cog andcochleariform process have beendrilled awayfenestrating the posterior wall of theexternal auditory canalAvoid fenestrating the posterosuperiorcanal wallIdentifying the facial nerve along itscourse in the mastoid is the best way ofavoiding injury to the nerveMost injuries occur when the facialnerve has not been adequatelyvisualisedDuraVII.LSSCGSPTeTGGVII.TLSCFigure 23: View of epitympanum withcog and cochleariform process drilledaway: Tympanic (VII.T) andLabyrinthine (VII.L) segments of facialnerve and Geniculate Ganglion (GG)and Greater Superficial Petrosal nerve(GSP); Superior Semicircular Canal(SSC); Lateral Semicircular Canal(LSC); Dura; Tensor Tympani tendon(cut) (TeT)Key points: Completed closed mastoidoepitympanectomy(Figure 24)The posterior canal wall should not betoo thinAvoid drilling too far anteriorly whileexposing the facial nerve andFigure 24: Completed closedmastoidoepitympanectomy13

OssiculoplastyRefer to the chapter on ossiculoplasty andincus interposition for detailed surgicalsteps.The following conditions should be presentin order to proceed to an incusinterposition at the time of the primarysurgery (Figure 25)Malleus handle presentStapes superstructure intactFootplate mobileCholeasteatoma limited and could beremoved entirelyIncus free of cholesteatomaAnterior third or half of the eardrum ispreserved and defines the proper planeSecond-stage surgery is done at 6-12months to ensure stabilisation of the graftin cases of perforation; to verifyeradication of cholesteatoma; and to assesswhether there is good middle earventilation and whether eustachian tubedysfunction is presentFigure 25: Incus interpositionThe cartilage is cut into 2-3 thin pieces(use a new 10 or 20 #blade)These pieces are aligned so as toslightly overlap each otherTympanic membrane reconstructionRefer to chapter on Myringoplasty andtympanoplasty for detailed surgical stepsTemporalis fascia or cartilage isharvestedIf there is diseased middle ear mucosaor retraction of the pars tensa, thensilastic sheeting (1mm thickness) isintroduced into the tympanic cavityand protympanum to prevent adhesionsbetween the graft and the promontoryThe graft always lies medial to thehandle of malleus (if present);therefore a slit has to be made toaccommodate the tensor tendonWound closure and packingThe meatal skin flap is replaced andgelfoam pledgets are placedstrategically over the meatal skin flapand fascia to secure it over thetympanic sulcusThe external canal is packed with astrip of gauze impregnated withantibiotic ointmentAn easyflow drain or tube of a suctiondrain (without suction!) is placed in themastoid cavity through a separate skinincision and the wound is closed inlayersA mastoid pressure bandage is appliedfor 1 dayPosterior canal wall reconstructionConchal or tragal cartilage is used toreconstruct the posterosuperior canalwall14

Open Mastoidoepitympanectomy (MET)Skin incision: As for Closed METPeriosteal flap: A small periosteal flap ismade in order to preserve the soft tissue formyosubcutaneous occipital flapCanalplasty: As for Closed METInspection of middle ear and division ofincudostapedial joint: As for Closed METAntrotomyAs for Closed METWith Open MET you may already havelowered the posterosuperior canal wallMastoidectomy and epitympanectomyRadical exenteration and exteriorisationof all cell tracts, includingretrofacial, retrolabyrinthine, supralabyrinthine,and supratubal cell tractsA common error is not to saucerise thecavity; this limits exposure and createsa larger cavityThe more bone one removes, thesmaller the cavityIncomplete exenteration will result in adischarging cavityNever leave bony overhangsLower the facial ridge over the mastoidsegment of facial nerveA high facial ridge may cause adischarging mastoid cavityTherefore it is important to skeletonisethe facial nerve in order to lower thefacial ridge sufficientlyLower the facial ridge with a largediamond burr and continuous suctionirrigationSkeletonize the facial nerve, keepingthe nerve intact within the bonyfallopian canal, but lowering the boneto the level of the facial nerveThe course of the nerve can clearly beidentified inferior to the lateralsemicircular canal, anterior to theposterior canal, and along thestylomastoid periosteal fibres at thelevel of the digastric ridgeRemoval of mastoid tipRemoval of the mastoid tip will helpreduce the size of the cavity byallowing soft tissue to collapse into thecavityThe stylomastoid foramen is medial tothe digastric ridgeAnteriorly where it extends into theexternal ear canal, the drill thereforeremains lateral to the digastric ridgeThe mastoid tip is weakened when onedrills with a diamond drill lateral to thedigastric ridge to expose the muscle atits attachment along the mastoid tipand will develop a fracture lineA rongeur is used to remove themobilised mastoid tip by rotating itoutwardsThe remaining soft tissue attachmentcan be cut with scissors pointing to theboneTympanoplastySee chapter on Myringoplasty and tympanoplastyfor detailed technique. Notethat if the tympanic membrane and annulusare deficient then a tympanic sulcus isdrilled out with a small diamond burr inorder to support the fascial graftObliteration of mastoid cavityThe mastoid cavity is small afterexteriorisation of a poorly pneumatisedmastoid and does not require obliteration.However following exenteration of alltracts in a highly pneumatised mastoid, one15

may be left with a large cavity; in suchcases obliteration is necessary to create adry cavityMastoid obliteration with myosubcutaneousoccipital flapThis is an inferiorly-based flap basedon the occipital artery which is rotatedinto the mastoid cavity (Figure 26)Vicryl 2/0 sutures are used to suturethe flap to the exposed digastric muscleto hold the flap in place in the mastoidcavityMeatoplastyFailure to do a meatoplasty with an opencavity can lead to a chronic draining ear. Ameatoplasty is therefore routinelyperformed because for exteriorization andself-cleansingA # 11 blade is inserted into theexternal ear canal and is directedposterosuperiorly toward the sinoduralangle; the concha is incised throughboth skin and cartilage (Figure 27)Figure 26: Inferiorly-based myosubcutaneousoccipital flapThe flap comprises subcutaneous fasciaand muscleIt extends superiorly behind themastoidectomy cavity from the mastoidtip where it is pedicled; the pedicle hasto be kept wide (3.5cm) enough so thatblood supply is adequateThe tip of the flap is just below thelevel of the temporalis muscle; thelength is approximately 7.5cmElevate the retroauricular skin from thesubcutaneous fascia using electrocauteryUse a mastoid raspatory to elevate theflap from the boneMastoid emissary veins may beencountered; bleeding is stopped withbipolar coagulation and/or diamonddrilling of the bony foramen with alarge diamond burr without irrigationFigure 27: Initial incisionHold the skin with forceps and usingcurved scissors, separate the skin fromthe conchal cartilage; it is important todirect the curvature of the scissorstowards the cartilage and not upwardstowards the skin as this may injure theskinOnce sufficient cartilage has beenexposed, excise cartilage circumferentiallywith tympanoplastyscissors; this results in 2 crescentshapedpieces of cartilage (Figure 28)The opening is approximately the sizeof the surgeon’s finger16

Gelfoam is placed medially in the earcanalGauze impregnated with Terracortrilointment is used to fill the lateralportion of the mastoid cavity and earA mastoid pressure dressing is appliedPostoperative care (Figure 30)Figure 28: Exposing cartilage, andillustrating cartilage to be removedThe conchal skin flaps are inverted byplacing 2/0 Vicryl sutures through theskin flaps and suturing them to thetemporal muscle superiorly and to themastoid soft tissues inferiorly. It maybe necessary to place more sutures toimprove the shape of the meatalopening (Figure 29)Mastoid drain removed after 24hoursMastoid pressure bandage removedafter 24hoursSutures/clips removed after 7-10 daysRibbon gauze with Terracortil ischanged every 2 weeks for 2 monthsAfter the ribbon gauze has beenremoved, topical eardrops (e.g.Otosporin) are applied for 2-4weeksFigure 30: Epithelialised mastoidcavity and meatoplasty 4 weeks aftersurgeryFigure 29: Completed meatoplastyIt is important that there are noexposed edges of the cartilage as thiscan lead to perichondritisWound closure and packingThe retroauricular wound is closed intwo layers using 2/0 Vicryl forsubcutaneous tissue and skin clips or3/0 Nylon for the skin. An easy-flowdrain may be insertedPostoperative ImagingCT cannot accurately definecholesteatoma postoperatively, becausethe CT attenuation of cholesteatoma isnot specific enough to differentiate itfrom granulation tissue or effusionNon-EPI MRI has better tissuedifferentiation for cholesteatoma andhas a high sensitivity and specificityfor cholesteatomas measuring >5mmThe senior author (T.L) recommendsroutine imaging, ideally with non- EPIdiffusion weighted MRI, at 1 & 3 yearsfollowing closed mastoidoepitympa-17

nectomy when there is concern aboutrecurrent or residual cholesteatomaReferencesFisch U, May J. Tympanoplasty, Mastoidectomy,and Stapes Surgery. New York:Thieme; 1994Jindal M, Riskalla A, Jiang D, Connor S,O'Connor AF. A systematic review ofdiffusion-weighted magnetic resonanceimaging in the assessment of postoperativecholesteatoma. Otol Neurotol 2011; 32(8):1243-9AcknowledgementsThis guide is based on the text by ProfFisch (Tympanoplasty, Mastoidectomy,and Stapes Surgery) and personalexperience of Prof Linder, as well ascourse material for the temporal andadvanced temporal bone courses conductedannually by Prof Fisch and Prof Linder atthe Department of Anatomy, University ofZurich, SwitzerlandAuthorTashneem Harris MBChB, FCORL,MMED (Otol), Fisch InstrumentMicrosurgical FellowENT SpecialistDivision of OtolaryngologyUniversity of Cape TownCape Town, South Africaharristasneem@yahoo.comSenior AuthorThomas Linder, M.D.Professor, Chairman and Head ofDepartment of Otorhinolaryngology,Head, Neck and Facial Plastic SurgeryLucerne Canton Hospital, Switzerlandthomas.linder@ksl.chEditorJohan Fagan MBChB, FCORL, MMedProfessor and ChairmanDivision of OtolaryngologyUniversity of Cape TownCape TownSouth Africajohannes.fagan@uct.ac.zaTHE OPEN ACCESS ATLAS OFOTOLARYNGOLOGY, HEAD &NECK OPERATIVE SURGERYwww.entdev.uct.ac.zaThe Open Access Atlas of Otolaryngology, Head &Neck Operative Surgery by Johan Fagan (Editor)johannes.fagan@uct.ac.za is licensed under a CreativeCommons Attribution - Non-Commercial 3.0 UnportedLicense18