Учебники / Middle Ear Mechanics in Research and Otology Huber 2006

Tympanic membrane blunting may include a spectrum of pathology ranging from an abnormal contour limited to the anterior sulcus to lateralization of the entire tympanic membrane giving rise to a false fundus. Some authors also consider complete external canal stenosis as a severe form of blunting. Tympanic membrane blunting can be recognized clinically by the following features: the absence of the normal acute angle at the anterior sulcus, or rounding along the anterior or inferior margin of the tympanic membrane. In more severe cases normal landmarks such as the malleus profile are lost and the tympanic membrane may be smaller than normal, have a convex contour or a blind sac appearance. There is always a conductive hearing loss.

The prevention and treatment of tympanic membrane blunting requires adherence to several important principles of reconstruction. The fascia graft must be anchored or secured in several locations including both anterior and posterior annulus as well as the malleus. Methods to encourage early epithelialization of the graft and bony canal must be used to preventgraftthickeningormigration.Thetechniquepresentedhereisareliable procedure to address the problem of tympanic membrane blunting.

2. Methods

Inordertocorrectabluntedanteriorannulusorlateralizedtympanicmembrane, the area of abnormal tissue must be completely excised. If there is any doubt about the condition of the remaining tympanic tissue it is removed.E ortstopreservetheepitheliumandexcisetheunderlyingfibrosis are usually unproductive. After excision, there is an area of absent skin in the bony canal adjacent to the tympanic defect. This can be a large part of the bony canal when the entire tympanic membrane is lateralized.

Thekeystosuccessfulcorrectionofthebluntingaretoanchorthefas-

178cia graft and to re-epithelialize the denuded bony canal and graft. The two main anchors to secure the temporalis fascia graft are the anterior bony annulus and the malleus handle. The fascia graft must be large enough to reach underneath the tympanic perforation and far anterior under the anterior annulus to reach the Eustachian tube opening. The superior edge offasciaispositionedmedialtothemalleushandle.Thefasciaissupported by gelfoam placed in the middle ear.

Thin split thickness skin grafts are best to re-epithelialize the exposed areas. These are obtained by a free hand technique from the upper arm near the axilla. A straight razor blade is used to obtain thin skin grafts approximately 2cm by 4cm in size. One or more of these grafts may be obtainedasneeded.The skin inthis area isthinwith few hairs, easy to access,

and leaves a hidden and cosmetically acceptable scar. A dermatome is not necessary and usually results in a graft that is too thick. The thin skin is placed on a backing of rayon cloth with a thin layer of antibiotic ointment. This serves as a support for the placement and initial healing of the skin graft. The rayon must be removed postoperatively in the clinic within two weeks or a foreign body reaction may occur.

Placement of the split thickness skin graft with its backing is important. The most critical placement is at the anterior sulcus, where a strip of skin is tucked tightly into the anterior angle, covering both the anterior bony wall and the fascia tympanic graft. Other strips of split thickness skin graft with their rayon backing are placed around the circumference of the canal to cover all areas without epithelium. The strips are cut so that the skincoversalloftherayonandtherearenogapsincoverage.Slightoverlap of the skin strips is acceptable because the overlapping skin will slough. If anyareasarenotcovered,orcoveredonlywiththerayonbacking,thereisa risk of granulation development with the end result of recurrent fibrosis.

In order to hold the grafts in place, gelfoam soaked with antibiotic solution is placed on top of the rayon backing for the skin grafts near the reconstructed tympanic membrane. The remainder of the external canal is packed with a ribbon of ¼ inch gauze with antibiotic ointment. All of the packing including the gauze and rayon skin graft backing is removed between postoperativeday 10and14.After packingremovalantibioticdrops are given for ten days. Follow up visits one month and two months after surgery insure that healing is progressing properly. If the skin graft does not take in some areas, excess granulation tissue is controlled with silver nitrate cautery.

3. Results

Six patients with tympanic membrane blunting as their primary pathol- 179 ogy were treated from 2000–2006. Patients with congenital aural atresia, acquired stenosis of the external canal due to trauma or infection, cholesteatoma of the middle ear or external canal or those with active chronic

otitis media were excluded from this study.

Five of the six patients gave a history of previous tympanoplasty surgery. The technique used for their surgeries whether overlay, underlay or other, was not known. In two of these patients the previous surgery was several years before their initial visit and hearing seemed to worsen after a periodofotorrhea.Thesixthpatienthadahistoryofchronicmyringitisfor more than four years treated intermittently with oral and topical medications.Atpresentationallpatientshadnotympanicperforationorotorrhea.

The preoperative and postoperative audiograms from all the patients were reviewed.HearingresultsarereportedaccordingtotheAmericanAcademy ofOtolaryngologyHeadandNeckSurgerycommitteeonhearingandequilibrium guidelines[1]. The pure tone averages for air and bone conduction at 0.5,1,2,3 kHz for each audiogram determined the air bone gap. Preoperative hearing results showed conductive hearing loss in all patients. The postoperative audiograms were at least six weeks after surgery and showed varyingdegreesofimprovement.ThreepatientshadclosureoftheA–Bgap to 10dB or less, one to 15 dB and two to less than 30 dB. All the results are shown in Table 1.

Table 1 Prev Surg= previous surgery, Hx Otorrhea= history of otorrhea, PreOP A–B gap, PostOp A–B gap= preoperative and postoperative air bone gap in dB.

The postoperative position of the tympanic membrane was normal in all patientswithrecreationoftheanteriorsulcus.Inpatient4,thereconstructed tympanic membrane appeared thicker than normal and the malleus profile was not distinct. It is suspected that tympanosclerosis a ecting the ossicular chain as well as the tympanic membrane resulted in limited improvementintheairbonegap.Patient6hadahistoryofcholesteatomaand underwent re-exploration of the middle ear. No recurrence was found and no explanation for her residual conductive loss was found.

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4. Discussion

Causes of blunting or lateralization of the tympanic membrane have been described previously. In his review of 48 cases, Plester[2] found blunting to be a complication of the onlay technique of tympanoplasty. He found anterior angle fibrosis but also deep penetration of a fold of epithelium into subepithelial tissue and even cholesteatoma in some cases. He concluded that blunting was a nearly unavoidable problem with the onlay method. Bluntingwasalsofoundtobeacomplicationoflateralonlaytympanoplasty by Segal et.al [3] in their seven cases. The incidence of iatrogenic tympanic membrane blunting may be decreasing with the increase in use of the underlay technique and cartilage grafting methods[4]. In their series of four-

teen cases, Sperling[5] found that nine occurred after previous tympanoplasty and four after atresia surgery all in children. The only adult case of lateralizationoccurredwithoutprevioussurgery.Theyalsonotetheoverlap of pathology with other conditions such as external canal stenosis and external canal as well as middle ear cholesteatoma. The cases in this study follow this pattern with five of six having previous tymanoplasty surgery, although it is not known whether the overlay technique was used. Cases of aural atresia, external canal stenosis and external canal or middle ear cholesteatoma were excluded in this study. In many of these cases the same operative techniques for reconstruction can be applied with success, but outcomes vary depending on the pathology.

Blunting can be the end result of a chronic inflammatory condition of the tympanic membrane and adjacent skin of the bony canal. These patientshaveamoistthinlayerofgranulationtissuereplacingtheepithelium which is refractory to most topical treatments and persists for years with gradual distortion of the anterior annulus and development of conductive hearing loss. This has been called chronic myringitis or chronic external otitis, but is clearly an unusual complication of these conditions and may represent a di erent pathologic process. The one patient in our study who did not have previous surgery falls into this category. It is also interesting to note that infection or inflammation may have played a role in the tympanic blunting of at least two of the patients with previous tympanoplasty. Both went several years with stable hearing but developed a noticeable drop in hearing after a period of otorrhea.

The techniques for treating tympanic membrane blunting vary. The underlay technique with various ways to anchor the fascia have been described[5,6,7]. This is almost always followed by skin grafting of denuded bone and fascia, usually using split thickness grafts. The abnormal skin and underlying fibrosis is usually excised and discarded, but Sperling[5]

describesatechniqueofskinpreservationwiththinningtoremovefibrosis 181 using a laser. He also augments this with fascia covered in split thickness

skin. The fascia is split so that a tongue of the graft is placed along the anterior bony canal while the remainder lies under the anterior annulus. A method using a cartilage-perichondrium composite graft from the tragus has also been suggested instead of temporalis fascia. This technique uses a full thickness skin graft and silastic sheeting to cover exposed canal bone[4].

5. Conclusion

Tympanic membrane blunting is an uncommon but frustrating complication of tympanoplasty surgery. It can also occur spontaneously as the end resultofachronicinflammationofthetympanicmembrane.Thetechnique presented here utilizing a well anchored underlay fascia graft with properly placed split thickness skin grafts can reliably correct this problem.

References

1.No author, Committee on Hearing and Equilibrium guidelines for the evaluation of results of treatment of conductive hearing loss. Otolaryngol Head Neck Surg 113(3) (1995) pp. 186–187

2.Plester D., Pusalker A., The anterior tympanic angle: the aetiology, surgery and avoidance of blunting and annular cholesteatoma. Clin Otolaryngol Allied Sci 6(5) (1981) pp. 323–328

3.Segal S., Winerman I., Man A., Surgical correction of the lateralized eardrum. J Larngol Otol 95 (1981) pp. 675–678

4.Boone R., Dornho er J., Surgical Correction of the Lateralized Tympanic Membrane. Laryngoscope 112(8) (2002) pp. 1509–1511

5.SperlingN.,KayD.,DiagnosisandManagementoftheLateralizedTympanicMembrane. Laryngoscope 110(12) (2000) pp. 1987–1993

6.Farrior J.B., The anterior tympanomeatal angle in tympanoplasty: surgical techniques for the prevention of blunting. Laryngoscope 93(8) (1983) pp. 992–997

7.Gyo K., Hato N., Shinomori Y., Hakuba N., Lateralization of the tympanic membrane as a complication of canal wall down tympanoplasty: a report of four cases. Otol Neurotol 24(2) (2003) pp. 145–148

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THE INTACT OSSICULAR CHAIN IN CHOLESTEATOMA SURGERY

John Hamilton, FRCS, Gloucestershire Hospitals Trust

John Hamilton, Dept of Otolaryngology, Gloucestershire Hospitals NHS Foundation Trust, Great Western Road, Gloucester, GL1 3EE, United Kingdom,

Phone: + 44 8454 226207, Email: john.hamilton@dial.pipex.com

A prospective parallel group study was performed of hearing outcomes in ears undergoing primary cholesteatoma surgery using a laser-assisted intact canal wall technique.

Group A had a continuous ossicular chain. Group B had a disrupted chain with an intact stapes superstructure onto which an ossiculoplasty had been performed.

The four frequency air-bone gap was calculated for each operated ear.

The Belfast Rules of Thumb were also used to calculate a dichotomous measure of whether the operated ear would provide useful hearing.

61 patients underwent surgery resulting in an intact chain. The median air-bone gap in this group was 15dB HL. 82% satisfied the requirements of the Belfast Rules.

84 patients underwent surgery requiring an ossiculoplasty onto an intact stapes. The median air-bone gap in this group was 20 dB HL. 50% satisfied the Belfast Rules.

The two groups are statistically discernible by both outcome measures (P<0.001, 183 Mann-Whitney ; P< 0.0002, χ2, ν = 1 respectively).

Preservationoftheossicularchainprovidesbetterhearingthananyreconstructed chain after cholesteatoma surgery. Moreover, the requirements of hearing preservation influence the entire surgical technique for the treatment of cholesteatoma.

1. Introduction

At the second MEMRO conference in Boston in 1999, an analysis of the longtermaudiologicalresultsofossiculoplastyincholesteatomasurgeryby HamiltonandRobinsonshowedthat,althoughtherewasasmalldeterioration in results for all ossiculoplasties in the first five years after surgery, the

longtermresultsremainedstable.Themostimportantdeterminantofboth the long term and immediate outcome of ossiculoplasty was the state of the ossicular chain after removal of cholesteatoma.

Preservationoftheintactossicularchainwasshowntoprovidemarkedly better results than any reconstruction of the chain, whether onto the capitulum or stapes footplate1.

In view of this finding, it was determined to preserve the ossicular chain in all patients undergoing cholesteatoma surgery who presented with the chain intact.

There are three di culties with this stratagem.

The most testing problem arises because cholesteatoma can be firmly adherent to the ossicles. Under this circumstance, the use of conventional steel instruments to remove disease is liable to cause movement of the ossicles, with the potential transfer of damaging energy into the cochlea. To minimize the risk of permanent sensorineural hearing loss and yet remove thecholesteatoma,theossicleshithertohavebeensacrificedalongwiththe adherent disease.

Thefibre-guided,visiblelightlaserhasprovidedthemeansforpreser- vation of the ossicular chain despite adherent cholesteatoma. This instrument uses a glass optical fibre to deliver light energy to the disease. The light energy vaporizes the cholesteatoma without causing any movement of the ossicles.

A second problem is that cholesteatoma can grow medial to the ossicular chain so that it can be di cult to identify. The fibre-guide laser solves thisdi cultyaswell,astheopticalfibreprovidesthemeanstoconductthe vaporising energy around corners. In di cult cases the action of the laser can be monitored with the use of a small otological mirror. In extreme cases the laser light can be reflected o the mirror onto the disease on the far side of the ossicle.

184 The third problem is the tendency of the disease to recur de novo by retraction. This problem does not directly a ect hearing results but may necessitate further surgery in the event that cholesteatoma should recur. If the ossicular chain is preserved intact and draped by epithelium, as in an “open” mastoid cavity, there is a high risk of keratinizing epithelium retractingbehindtheepitympanicregionofthechain.Tominimisethisrisk, it is prudent to shield the epitympanic part of the chain by preservation of theearcanalwall.Thisstudyisthereforerestrictedtopatientsinwhomthe ear canal has been preserved.

The distributions of the hearing results, as measured by the air-bone gap, were assessed by the Mann-Whitney U-test.

The distributions of the hearing results as measured by the Belfast rules were assessed by the Chi Square test with Yates correction.

3. Results

61 patients underwent cholesteatoma surgery resulting in an intact canal wall and an intact chain. The median air-bone gap in this group was 15dB HL with a range of 2.5–30 dB HL.

84 patients underwent cholesteatoma surgery resulting in an ossiculoplasty inthepresenceof anintactcanalwall. The medianair-bone gapin this group was 20 dB HL with a range of 7–55 dB HL.

The raw data are shown in figure 1. The cumulative distribution of each group is shown so that the two groups can be clearly distinguished.

The two groups are statistically discernible (z = 5.57 P<0.001, MannWhitney)

Patient benefit as assessed by the Belfast Rules of Thumb is a more stringenttestofaudiometricoutcome.Fiftyoftheintactchaingroup(82%) satisfied the requirements of this test. Forty of the ossiculoplasty group (50%) satisfied this test (see figure 2). The two groups are also statistically di erent when measured by this outcome ( χ2 = 14.22, ν = 1, P<0.0002)

4. Conclusions

This investigation has confirmed the hypothesis, suggested by the study presented at the Second Middle Ear Mechanics meeting in Boston in 1999, that preservation of the ossicular chain provides better hearing than any reconstructed chain after cholesteatoma surgery.

Comparison of the median outcomes may suggest that the improvement in middle ear function with chain preservation is “small”. This evaluation ignores the stringent constraints required of a reconstructed middle ear to be part of a functionally useful ear. To benefit the patient the ear must have good cochlear and middle ear function and any loss of cochlear function sti ens the demands on middle ear reconstruction. In this con-

186text, any procedure which improves middle ear function, even if only by a “small” amount, is important: a 12 dB cochlear loss combined with a 20dB conductive loss may result in an air conduction threshold which does not provide the patient with any benefit. The same cochlear loss with a 15dB conductivelosswouldberegardedasusefultothepatient.Inthisstudythe 5dBimprovementinconductivehearingissu cienttoincreasetherateof useful hearing from 50% to 82%.

The desire to consistently preserve the ossicular chain in cholesteatomasurgeryresultsinanobligationtoadoptaveryparticularsurgicaltechnique,in whichboth the useof a fibre-guidedlaser and thepreservationof the ear canal wall are necessary.

This perspective is entirely new in cholesteatoma surgery: instead of being a mere afterthought at the end of the surgical procedure, the requirements of hearing preservation now influence the entire surgical technique for the treatment of cholesteatoma.

Fig. 1 Cumulative distribution of audiological assessment of middle ear function (airbone gap) for ears with intact chain and ears with ossiculoplasty onto intact stapes at the end of cholesteatoma resection with intact canal wall.

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