Dimensions of the sinus tympani and its surgical access via a retrofacial approach

Radioanatomical evaluation of the subtympanic sinus in children under five years old and its clinical implications - high resolution computed tomography study

PURPOSE

This study aimed to evaluate subtympanic sinus (STS) and its vicinity in high-resolution computed tomography (HRCT) scans of children under five years old with non-diseased temporal bones.

MATERIAL AND METHOD

We divided the whole group into children under 24 months of age (first stage of pneumatisation development) and between 25 and 60 (second stage). We have determined the width of the entrance to STS, depth of the STS, type in relation to facial nerve according to Anschuetz classification, the pneumatisation of posterior and medial air cell tracts, and jugular bulb position. All the HRCTs (280 temporal bones) were analyzed according to the multiplanar reconstruction protocol with symmetrization.

RESULTS

STS's mean width and depth were 2.71 ± 0.60 mm and 3.26 ± 1.11 mm, respectively. The most common STS type was type A (59.3%), followed by type B (30.7%) and type C (10%). The posterior air cell tract (retrofacial cells) was present in 39.3%. The medial air cell tract (hypotympanic cells) was present in 30.7% The jugular bulb position affected the final shape of STS in 17.5%.

CONCLUSION

The results support the necessity of the classification for the STS. Our study may help with surgical planning regarding endoscopic ear procedures and gives a broader understanding of how pneumatization or jugular bulb might correlate with the final shape of the retrotympanum. The historical remarks track the term's origin for clarity in research and respect for earlier investigators.

Impact of Sigmoid Sinus Anatomy on Assessing the Feasibility of the Retrofacial Access to the Entire Jugular Fossa Before Surgery

BACKGROUND AND OBJECTIVES

The jugular fossa (JF) is a challenging area for surgical approaches because of its complex anatomy and proximity to neurovascular structures. The study evaluates the feasibility of the neuronavigated microsurgical transmastoid extended infralabyrinthine extradural retrofacial approach (mTEIER-A) in human head specimens for accessing the entire intraosseous JF in relation to the position of the sigmoid sinus (SS), horizontal angle of attack, and size of the SS.

METHODS

The mTEIER-A was performed on human head specimens. Before dissection, the position of the SS, horizontal angle of attack, and size of the SS were measured on tilted axial high resolution computed tomography scans; after dissection, access to the lateral aspect of the JF on dissected human head specimens and on postoperative high-resolution computed tomography scans was examined. The position of the SS was classified relative to a predefined reference line, and the feasibility of retrofacial access was documented.

RESULTS

SS positions located medial to the reference line (P1) and horizontal angles >12.5° significantly enhance retrofacial access to the lateral aspect of the JF, whereas the size of the SS has a limited impact.

CONCLUSION

Depending on the position of the SS and the horizontal angle of access, mTEIER-A provides sufficient retrofacial access to the lateral aspect of the JF. These findings emphasize the need for precise preoperative planning and suggest that mTEIER-A could minimize the need for more invasive approaches, potentially reducing related morbidity. Further clinical studies are recommended to validate these findings.

The posterior-inferior recess of the sinus tympani, an anatomical novelty

BACKGROUND

The anatomy of the retrotympanum is highly variable, and surgical access is challenging. In the medial retrotympanum, a descending series of recesses are found: the posterior tympanic sinus, the sinus tympani (ST), and the subtympanic sinus (STS). Most of the previous anatomical studies of the ST evaluated it as a single depression of variable width and depth, without recesses, just on axial sections.

METHOD

The ST was evaluated bilaterally in all the anatomical planes on a lot of 100 cases. Two sagittal anatomical types of the ST were defined and counted: type 0 (saccular ST), with absent postero-inferior recess (PIR) of the ST, and type 1, ST with PIR (bowl-shaped ST).

RESULTS

In 200 sides, 144 type 0 ST (72 %) and 56 types 1 (PIRs) of the ST were found (28 %). On the right/left sides the type 0 ST was found in 74 %/70 % and the type 1, with PIR, in 26 %/30 %. There were no significant correlations between sex and the ST types on both sides. In the general lot, bilaterally symmetrical types 0 were found in 68 %, bilaterally symmetrical types 1 in 24 %, and the bilaterally asymmetrical combination 0+1 in just 8 %.

CONCLUSIONS

The PIR of the ST is not a scarce anatomical variation in the retrotympanum. It is hidden deep to the ST and difficult to access through the middle ear. It also could retain residual cholesteatoma. A retrofacial approach could access the PIR of the ST if no other anatomical limitations occur.

Surreptitious Area of Middle Ear - the Sinus Tympani

Sinus tympani is one of the hidden space in the retrotympanic area of middle ear which is commonly invaded by cholesteatoma and known for recidivism. Conventional surgical approaches sometimes fail to access deep sinuses and eradicate the disease. The aim of our study was to measure endoscopic depth of Sinus tympani in Indian Population. Total of 30 patients underwent mastoid exploration and intraoperatively depth of Sinus Tympani was measured using a 0.5 mm calibrated probe with 30 degree rigid Hopkins endoscope. Endoscopic depth in the present study ranges between 2.5 and 5.5 mm. It was higher in right ear in case of females however no significant difference were seen in males and females on left side. It is difficult to clear disease from Sinus Tympani because of its inaccessible location. Sinus Tympani can also show variations in terms of its depth further making difficult to clear disease.

Radiologic evaluation and clinical assessment of facial sinus in adults and children - computed tomography study

OBJECTIVE

The facial sinus is a recess of the lateral retrotympanum located between the chorda tympani (ChT) and facial nerve (FN). Chronic otitis media with cholesteatoma often spreads from the pars flaccida to the facial sinus (FS). In stapedotomy, if an unfavorable ChT type is encountered, there is a need for removal of bone between the ChT and FN. The aim of the study was to assess FSs in adults and children according to Alicandri-Ciufelli classification, to measure FS width and depth in computed tomography scans, evaluate the correlation between measurements and different types of facial sinuses, and provide a clinical context of these findings.

METHODS

Cone Beam Computed Tomography (CBCT) of 130 adults and High Resolution Computed Tomography of 140 children were reviewed. The type of facial sinus was assessed according to Alicardi-Ciufelli's classification in different age groups. Width of entrance to facial sinus (FSW) and depth of FS (FSD) were evaluated among age groups.

RESULTS

Type A of FS is dominant in both adult and children populations included in the study. The average depth of FS was 2.31±1.43 mm and 2.01±0.90 in children and adults respectively. The width of FS was 3.99±0.69 and 3.39±0.98 in children and adults respectively. The depth of FS (FSD) presented significant deviations (ANOVA, p<0.05) among all three types and age groups. In 116/540 (21.5%) cases the value of FSD was below 1 mm.

CONCLUSION

The qualitative classification of facial sinuses into types A, B and C, introduced by Alicandri-Ciufelli and al. is justified by statistically significant differences of depth between individual types of tympanic sinuses. Type A sinuses may be extremely shallow (<1 mm - As) or normal (>1 mm - An). Preoperative assessment of CT scans of the temporal bones gives crucial information about type and size of facial sinus. It may increase the safety of surgeries in this area and play a role in choosing an optimal approach and surgical tools.

Examination of sinus tympani, subtympanic sinus, and facial sinus with MicroCT

This study aimed to determine sinus tympani, subtympanic sinus (STS), facial sinus (FS) morphologies, and type distributions. Type distributions were based on their relations with the facial nerve (FN). A total of 20 right and 20 left temporal dry bones without physical deformation were scanned with a MicroCT device. All measurements were made using MicroCT programs from sections in the axial plane. For the FS, the average depth was measured as 3.485 mm without any classification, and 29 of the 40 bones had Type C radiological morphology. The mean depth for all sinus tympanicus was 2.646 mm, and 22 of the 40 bones had Type B morphology. For the STS, 29 out of 40 samples had no contact with the FN; regardless of the classification, the average depth was measured as 2.376 mm. We reveal the depths of the tympanic cavities and their relationship with the FN. The results of this study may benefit clinicians performing retrotympanum surgeries.

Sinus tympani revisited for planning retrofacial approach-radiologic study in pneumatized temporal bones and its surgical implications

BACKGROUND AND PURPOSE

Retrofacial approach (RFA) is an access route to sinus tympani (ST) and it is used in cholesteatoma surgery, especially when type C ST is encountered. It may also be used to gain an access to stapedius muscle to assess the evoked stapedius reflex threshold. The primary object of this study was to evaluate the morphology of sinus tympani and its relationship to facial nerve (FN) and posterior semicircular canal (PSC) in context of planning retrofacial approach in pneumatized temporal bones.

METHODS

CBCT of 130 adults were reviewed. The type of sinus tympani was assessed according to Marchioni's classification. Width of entrance to sinus tympani (STW), depth of ST (STD), distance between the posterior semicircular canal and facial nerve (F-PSC), distance between the latter plane to the floor of ST at the right angle (P-ST) were measured at level of round window (RW) and pyramidal ridge (PR).

RESULTS

All of the bones were well-aerated and classified in Dexian Tan pneumatization group 3 or 4. Type B of ST is dominant (70.8%) in adult population with no history of inflammatory otologic diseases, followed by type C (22.7%) and then type A (6.5%). The depth of ST (STD) presented significant deviations (ANOVA, p < 0.05) among all three types. STW reaches greater values on the level of PR. F-PSC does not correlate with type of ST. In over 75% of examined type C sinus tympani the distance P-ST was less than 1 mm.

CONCLUSIONS

The qualitative classification of the sinus tympani into types A, B and C, introduced by Marchioni is justified by statistically significant differences of depth between individual types of tympanic sinuses. The STW distance reaches greater values inferiorly-it may suggest that RFA should be performed in infero-superior manner rather than opposite direction. Preoperative assessment of temporal bones CT scans gives very important information about size of sinus tympani and distance between FN and PSC.

Cochlear Implantation: The use of OTOPLAN Reconstructed Images in Trajectory Identification

OBJECTIVES

This study aimed to define the best electrode trajectory line in cochlear implant (CI) surgery using the OTOPLAN (otology planning software) reconstructed 3D model and to investigate the surgical distance of the retro-facial approach as a direct access to the round window.

METHODS

Computed tomography (CT) scans of the normal temporal bone were included for analysis in this study. OTOPLAN reconstruction was used to build 3D models with specific ear structures for study analysis.

RESULTS

Twenty-five scans were included; the average age at the time of CT scan was 6.8±12 years. Twelve scans (48%) were right-sided and thirteen (52%) were left-sided. The best trajectory line to the round window was identified in all scans. The retro-facial approach was the optimal approach for 52% of cases (13/25). In all scans, the safe distance from the facial nerve were in favor of the retro-facial approach (P = 0.0011).

CONCLUSION

The OTOPLAN reconstructed imaging provided a good analysis of the retro-facial approach and helped in planning the surgical trajectory line towards the round window. Additionally, calculation of the surgical distance can help the surgeon compare the retro-facial approach to the standard facial recess for preoperative planning. These findings may help in robotic surgery.

On the radiologic anatomy of pediatric sinus tympani: HRCT study

OBJECTIVE

Sinus tympani (ST) is considered the most constant among retrotympanic recesses but it is of great anatomical variability in shape and relation to mastoid portion of facial nerve. ST is difficult to access when clearing the cholesteatoma or serving as a window for cochlear implantation. The objective was to describe morphology of ST and assess feasibility of retrofacial approach in children under 5 years old.

METHODS

HRCT images of 150 children were reviewed. The type of sinus tympani was assessed according to Marchioni's classification. Width of entrance to sinus tympani (STW), depth of ST (STD), distance between the posterior semicircular canal and facial nerve (F-PSC), distance between the latter plane to the floor of ST at the right angle (P-ST) were measured. Width (HS-SS) and length (ML) of mastoid process were also measured.

RESULTS

From 300 temporal bones analyzed, the most common type of ST was type B (59.3%), followed by type C (34.3%) and type A (6.3%). The average depth of ST was 3.38±1.04 mm (1.32-8.24 mm) and mean value of F-PSC (width of retrofacial approach) was 4.91±0.75. The depth of ST (STD) presented significant deviations (ANOVA, p<0.05) among all three types. The value of ML increased with age (very high correlation).

CONCLUSION

Deep tympanic sinus (type C) is more frequent in children than in adult populations and it may suggest that pneumatization may affect the development of tympanic sinus final shape. Retrofacial approach can be used in selected pediatric patients after HRCT analysis.

Analysis of tympanic sinus shape for purposes of intraoperative hearing monitoring: a microCT study

PURPOSE

Sinus tympani is the space in the retrotympanum, with variable morphology. Computed tomography is a common tool to investigate sinus tympani anatomy. During cochlear implantation or tympanoplasty, electrocochleography can be used for hearing monitoring. In such a surgical strategy the electrode is placed in the round window's region throughout posterior tympanotomy. Common accessible needle-shaped electrodes using is difficult in achieving intraoperative stabilization. The aim of the study is to assess the dimensions and shape of sinus tympani, basing on the micro computed tomography scans for purposes of establishing the possible new electrocochleography electrode shape.

MATERIALS AND METHODS

Sixteen fresh frozen cadaveric temporal bones were dissected. MicroCT measurements included the depth and the width of sinus tympani, width of facial canal with stapedius muscle chamber. Obtained data were analyzed statistically with the use of RStudio 1.3.959 software.

RESULTS

The highest average width of sinus tympani amounted for 2.68 mm, depth measured at the round window plane for 3.19 mm. Width of facial canal with stapedius muscle chamber highest average values at the round window plane- 3.32 mm. The lowest average minimum and maximum values were calculated at the 1 mm above the round window plane. The highest average posterior tympanotomy width was 2.91 mm.

CONCLUSIONS

The shape of the tympanic sinus is like a trough with the narrowest and deepest dimensions in the middle part. The ST shape and dimensions should be taken into account in constructing the ECochG electrode, designed for optimal placement through posterior tympanotomy approach.

[Round window implantation of vibrant soundbridge through a retrofacial approach]

Objective:To investigate the specific retrofacial approach for application of vibrant soundbridge （VSB） to the round window （RW） in patients with complex congenital ear malformation. Methods:The clinical information of four patients with congenital ear malformation were retrospectively analyzed. VSB were implanted unilaterally in these four patients via a retrofacial approach. During the operation, it is difficult to reach the RW via a classic posterior tympanotomy pathway, due to the mastoid portion of FN positioned anteriorly severely. So the round window niche was identified through a retrofacial pathway and the round window vibroplasty was completed. Results:All four patients received the round window vibroplasty successfully via retrofacial approach. Satisfied auditory benefit were confirmed after surgery. Compared with the preoperative data, clear improvements in both hearing threshold and the speech discrimination score were confirmed after VSB activation. Neither intraoperative nor postoperative surgical complications was observed in all patients. Conclusion:During the round window vibroplasty, when it was unable to access the RW through the classic facial recess pathway due to the aberrant facial nerve， the retrofacial approach could be a valid and feasible alternative approach.

A retrofacial approach of round window vibroplasty during Vibrant Soundbridge implantation for patients with congenital ear malformation

OBJECTIVE

To describe the specific retrofacial surgical approach for application of Vibrant Soundbridge (VSB) to the round window (RW) in patients with congenital ear malformation.

METHODS

Four patients with congenital ear malformation were implanted with VSB unilaterally through a retrofacial approach in present study. During the operation, the round window niche was identified through a retrofacial pathway and the floating mass transducer (FMT) was attached to the RW inferiorly.

RESULTS

Satisfied outcomes were confirmed after surgery. No intraoperative or postoperative surgical complications were observed in all patients.

CONCLUSION

When the facial nerve was aberrant or it was unable to access the RW through the classic facial recess pathway during the round window vibroplasty, the retrofacial approach could be a valid and feasible alternative approach.

Quantitative three-dimensional computed tomography analysis of sinus tympani volume in temporal bones with petrous apex pneumatization

OBJECTIVE

To investigate the association between sinus tympani volume and petrous apex pneumatization in this retrospective-archival temporal bone computed tomography study.

METHODS

We included 46 temporal bones with pneumatized petrous apex from 26 patients and 52 temporal bones without petrous apex pneumatization from 26 other patients. Using OsiriX software for MacOS (version 3.8.1, Pixmeo), we measured the volumes from three-dimensional sinus tympani models and compared the sinus tympani volumes and depths between the temporal bones with and without pneumatized petrous apex.

RESULTS

Among 150 patients totally reviewed, 26 (17.3%) had petrous apex pneumatization. The median sinus tympani volume was 16.05 (5.6-59.7) mm³ in temporal bones with pneumatized petrous apex and 8.7 (1.76-59.7) mm³in temporal bones without. The sinus tympani volume was significantly greater in temporal bones with pneumatized petrous apex compared to those without (p < 0.001). Additionally, temporal bones with pneumatized petrous apex had a significantly deeper sinus tympani [median depth = 2.17 (0-3.04) mm] compared to the temporal bones without [median depth = 1.69 (0-3.73) mm] (p = 0.045). We found that petrous apex pneumatization was associated with deeper and larger sinus tympani.

CONCLUSION

Patients with pneumatized petrous apex had a greater sinus tympani volume associated with the increased risk of residual cholesteatoma.

Sinus Tympani Endoscopic Anatomy

OBJECTIVE: The sinus tympani has been the focus of clinical interest because of its tendency to be invaded by cholesteatoma, its visual obscurity, and the lack of a straightforward surgical approach by which it can be addressed. This study was undertaken to describe the microscopic as well as the endoscopic anatomy of the sinus tympani.

STUDY DESIGN AND SETTING: Thirty temporal bones harvested from cadavers were dissected using an operating microscope and telescopes with different angles and 2.7- and 4-mm diameters, fitted with a videocamera. Images were transmitted to a computer screen. Precise measurements were made after scaling the distances with the digital image processing.

RESULTS: Marked variation in size and shape was the rule. It was found that the sinus tympani is bounded laterally by a constant ledge of bone anterior to the facial nerve. It was deep, extending posterior to the facial nerve in 6 specimens. The telescopes (30° to 70°) enabled the surgeon to see this region clearly because the orifice plane was more or less perpendicular to the axis of the external auditory canal.

CONCLUSION: The study emphasizes the importance of removal of this lateral lip of bone to expose the orifice of the sinus tympani. This should be complemented with the use of a 30° endoscope (1.7 mm in canal-up and 4.0 mm in canal-down technique) for better visualization and cleaning of this hidden area.

Posterior Sinus of the Middle Ear

Objectives:

This study defines the anatomy of the posterior sinus of the middle ear and its relationship with the sinus tympani.

Methods:

Fifty-one temporal bone plugs harvested from human cadavers were studied. The depth and width of the posterior sinus, its relationship to surrounding structures, and the structure that separates it from the sinus tympani were studied.

Results:

The posterior sinus, positioned just posterior to the oval window, was 1 mm or less in depth, and the width of the opening 1.5 mm or less. A ridge of bone from the floor of the middle ear separated the posterior sinus from the sinus tympani in 82% of specimens. In 10% a sheet of bone separated the two sinuses, and in 8% the sinus tympani and posterior sinus formed one confluent recess.

Conclusions:

This is the first study that describes the anatomy of the posterior sinus of the middle ear. This sinus is separated from the more inferiorly located sinus tympani by a ridge of bone, not by the ponticulus as was previously thought, and it is no larger than 1 mm in depth and 1.5 mm in width. The results from this study give the otologic surgeon knowledge of middle ear anatomy that he or she can use when removing cholesteatoma, granulation tissue, or retracted epithelium from the posterior tympanum.

The Feasibility of the Retrofacial Approach to the Pediatric Sinus Tympani

OBJECTIVE: To investigate the feasibility of the retrofacial approach to the pediatric sinus tympani (ST).

STUDY DESIGN AND SETTING: Five pediatric cholesteatoma cases, 10 pediatric and 24 adult normal specimens were studied retrospectively using high-resolution CT measurements in our university hospital. The normal pediatric and adult specimens also underwent temporal bone dissections. CT measurements included the depth (d-ST) and the width (w-ST) of ST, the distance (F-PSC) from the facial canal to the posterior semicircular canal, and the distance (P-ST) from the depth of ST on a line perpendicular to the F-PSC line.

RESULTS: There were no significant differences in any measurements between pediatric and adult normal specimens and between pediatric diseased and normal specimens ( P > 0.05). The retrofacial approach performed in pediatric specimens was no more complex than in adult specimens. F-PSC>3.0 mm and P-ST<2.0 mm provided an accessible approach to the pediatric ST.

CONCLUSION: The retrofacial approach can be used in selected pediatric cases.

SIGNIFICANCE: This approach plays its individual role to eradicate cholesteatoma in a difficult-to-reach pediatric ST.

Anatomic Limitations of Posterior Exposure of the Sinus Tympani

OBJECTIVE: The sinus tympani is a challenging area for the otologic surgeon to access and from which to remove the disease process. Recently, a posterior approach to the sinus tympani through the mastoid was proposed as an alternative technique in cases of deep sinus tympani.

STUDY DESIGN AND SETTING: The posterior approach was performed by dissecting the triangular bony area formed by the facial nerve, lateral semicircular canal, and posterior semicircular canal in 8 temporal bone specimens.

RESULTS: The edges of the triangle on the facial nerve and lateral semicircular canal were almost constant at 5 mm. The edge on the posterior semicircular canal was about 4 mm.

CONCLUSION: It is possible to expose the sinus tympani from the posterior by careful dissection through this triangle, which has almost constant dimensions.

Endoscopic anatomy of the middle ear

Good knowledge of anatomy is fundamental for every surgeon. Middle ear anatomy is really complex and sometimes is challenging for otologists, who need to explore every single compartment for a radical removal of pathology. With introduction of the endoscope in middle ear surgery, anatomy of middle ear spaces has become wider and clearer due to a better magnification and to the possibility to look "behind the corner". This article is a review of the state-of-art of endoscopic middle ear anatomy with description of every compartment, with particular attention to ventilation pathways and middle ear folds.

Superior mesotympanic sinus

OBJECTIVES

This study of the posterior tympanum was performed to better define the anatomy of this complex area of the middle ear. A sinus previously not described was examined.

METHODS

The posterior tympanum of 49 temporal bones was studied by microscopic techniques. The sinus depth, the opening into the sinus, and the relationship of the facial nerve to the sinus were documented.

RESULTS

A sinus lying in the superior part of the posterior tympanum was discovered: the superior mesotympanic sinus. The depth of the sinus was from 0.5 to 2 mm, and it was present in 42 of the 49 specimens (86%). The superior border of the sinus is the facial nerve, which was dehiscent in 9 cases.

CONCLUSIONS

The surgeon can remove disease with more confidence from the tympanum if he or she knows that disease may harbor in this sinus, and that injury to the facial nerve must be avoided.

Pyramidal eminence and subpyramidal space: an endoscopic anatomical study

OBJECTIVES/HYPOTHESIS

To describe retrotympanic endoscopic anatomy, especially the pyramidal eminence and contiguous spaces.

STUDY DESIGN

This was an anatomical study on a prospective case series.

METHODS

The anatomy of the retrotympanum was studied by endoscopy in nine patients affected by cholesteatoma who underwent tympanomastoid surgery and in six temporal bone dissections.

RESULTS

Pneumatization of the sinus tympani and posterior tympanic sinus or both, noted in 12 ears out of 15, may give rise to a recess beneath the pyramidal eminence, which we have called the subpyramidal space. This space can manifest with a variable degree of depth, shape, or extent depending on the shape and dimensions of the pyramidal eminence.

CONCLUSIONS

Endoscopic exploration of the middle ear may guarantee a very good exposure of retrotympanic structures, allowing detailed anatomical descriptions of hidden areas. Improvement in our knowledge of the anatomy may decrease the possibility of residual disease during cholesteatoma surgery.

Surgical Anatomy of Anterior and Retrofacial Approaches to Sinus Tympani

OBJECTIVES

To define anatomic parameters indicating or limiting the use of anterior and retrofacial accesses to sinus tympani (ST).

MATERIAL

Anatomic study (30 temporal bones).

MAIN OUTCOME MEASURE

The profundity of the ST, the distance between the sigmoid sinus and facial nerve (SS-F), the distance from posterior semicircular canal to the facial nerve, and the capacity of adequate visualization of the ST.

RESULTS

Sinus tympani depth was significantly smaller (<or=0.83 mm) when visualization was possible by anterior approach. Measurements of SS-F greater than 10 mm and ST profundity greater than 1 mm indicated accessibility of posterior approach.

CONCLUSION

Posterior extension of ST and the relation SS-F were the most important measures when the surgical accessibility of the ST was envisaged. Sinus tympani can be accessed through an anterior approach when the depth is less than 1 mm or by means of a posterior access when profundity is 1 mm or greater and the relation of SS-F is 10 mm or greater.

Efficacy of the KTP Laser in the Treatment of Middle Ear Cholesteatoma

OBJECTIVE

To evaluate whether ancillary use of the KTP (potassium titanyl phosphate) laser can diminish the rate of residual disease in intact canal wall cholesteatoma surgery.

STUDY DESIGN

Prospective controlled parallel group study.

SETTING

Two neighboring district general hospitals, one with a KTP laser and one without.

PATIENTS

All patients undergoing staged intact canal wall surgery for cholesteatoma.

INTERVENTION

Staged intact canal wall surgery for cholesteatoma.

MAIN OUTCOME MEASURE

Presence or absence of residual disease at the second stage operation, performed at least 12 months after the first operation.

RESULTS

Thirty-three patients underwent treatment without and 36 underwent treatment with the laser. Ten patients without laser treatment had residual disease, whereas one patient had residual disease after laser treatment (p = 0.003). After adjustment using logistic regression, treatment still has a significant effect on outcome (p = 0.013). The number needed to treat is four.

DISCUSSION

Ancillary use of the KTP laser in cholesteatoma surgery is a treatment that significantly improves complete removal of disease.

A New Method of Studying the Anatomy of the Posterior Tympanum

The anatomic position of the posterior tympanum compromises direct visualization and investigation of its structures. Therefore, assessment of its anatomy is limited, and surgical removal of disease in this area remains a challenge. In this article, the author describes a new method that can be used to fully expose, visualize, and measure the structures in the posterior tympanum, thereby allowing for further definition of the anatomy and, in turn, refinement of surgical techniques for the removal of disease in this portion of the middle ear. The new technique involves removal of the anterior canal bone and its overlying tissues to eliminate the mechanical barriers to the posterior tympanum, which allows for direct visualization and measurement of the posterior tympanic structures. This method has three primary advantages over other methods used to study the posterior tympanum. First, observations of the anatomy can be made under direct visualization. Second, this method permits investigators to study the anatomy and the relationships between structures of the posterior tympanum as they occur in their normal unaltered state. Third, this method allows for wide anterior access to the posterior tympanum, thereby making scientific research into its anatomy possible. Information obtained from future studies of this method can help further refine surgical techniques for removal of disease from the posterior tympanum.

High-resolution computed tomographic study of the retrotympanum. Anatomic correlations

The aim of this study was to define the imaging of the retrotympanum precisely by means of high-resolution CT. Based on 66 scans of petrous bones performed in 49 patients observed in an otologic department, several retrotympanic structures were studied: the pyramidal eminence, ponticulus, subiculum, chordal ridge, tympanic sinus of Proctor, sinus tympani and recess of the facial n. The variations in morphology and depth were noted as well as the relationship between the pyramid and the facial canal. In a second phase the same anatomic structures were studied in 24 temporal bones removed from embalmed cadavers and investigated with the same radiologic technique. Anatomic correlations were made for six temporal bones to confirm the general applicability of our radiologic hypotheses. In CT the pyramidal eminence was visualised in 100% of cases, the chordal ridge in 52%, the ponticulus in 63% and the subiculum in 57%. As regards the different recesses, the sinus tympani was visualised in 95% of cases, the posterior tympanic sinus of Proctor in 38%, the fossula of Grivot in 47% and the facial recess in 80%. The mean depth of the sinus tympani was 2.7 mm and that of the tympanic sinus of Proctor was 1.65 mm; the fossula of Grivot was assessed as 2.1 mm and the facial recess as 2.2 mm. A better knowledge of these sinuses and their variations will aid the surgeon, particularly in a posterior tympanotomy or a retro-facial approach.