Radiological assessment of the sinus tympani: temporal bone HRCT analyses and surgically related findings

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.

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.

Evaluation of Medial Retrotympanum by High-Resolution Computed Tomography and Endoscopy - A Descriptive Study

The aim of this study was to determine and compare the capability of the High-Resolution Computed Tomography (HRCT) and endoscope in detecting hidden areas of medial retrotympanum in cases with chronic otitis media (COM). Per-operative endoscopic evaluation of structures in medial retrotympanum was done in 74 patients suffering from COM and was compared with pre-operative HRCT of the temporal bone in 50 patients. HRCT revealed type-A Sinus Tympani (ST) in 61.2%, type-B in 34.7%, and type-C in 4.1% of the patients; endoscope could reveal type-A in 71.6%, type-B in 25.7% and type-C in 1.4% of the patients. Ponticulus was discovered in 84.1%, subiculum in 100%, finiculus in 97.3% and sinus subtympanicus (SST) in 100% of the cases using endoscope. HRCT could detect ponticulus in 38.6% and subiculum in 4.0% of the cases. HRCT could not very clearly detect finiculus and SST. HRCT could not differentiate the content of the ST as compared with endoscopy. HRCT is a useful diagnostic tool in predicting the presence and type of ST, but its accuracy in detecting SST, finer bony ridges of ponticulus, subiculum, and finiculus and the contents is poorer than endoscope.

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.

Accuracy of High-Resolution Computed Tomography Compared to High-Definition Ear Endoscopy to Assess Cholesteatoma Extension

OBJECTIVE

To correlate radiographic evidence of cholesteatoma in the retrotympanum with intraoperative endoscopic findings in cholesteatoma patients and to evaluate the clinical relevance of radiographic evidence of cholesteatoma in the retrotympanum.

STUDY DESIGN

Case series with chart review.

SETTING

Tertiary referral center.

METHODS

Seventy-six consecutive cases undergoing surgical cholesteatoma removal with preoperative high-resolution computed tomography (HRCT) were enrolled in this study. A retrospective analysis of the medical records was conducted. The extension of cholesteatoma regarding different middle ear subspaces, into the antrum and mastoid were reviewed radiologically in preoperative HRCT and endoscopically from surgical videos. Additionally, facial nerve canal dehiscence, infiltration of the middle cranial fossa, and inner ear involvement were documented.

RESULTS

Comparison of radiological and endoscopic cholesteatoma extension revealed statistically highly significant overestimation of radiological cholesteatoma extension for all retrotympanic regions (sinus tympani 61.8% vs 19.7%, facial recess 69.7% vs 43.4%, subtympanic sinus 59.2% vs 7.9%, and posterior sinus 72.4% vs 4.0%) and statistically significant overestimation for mesotympanum (82.9% vs 56.6%), hypotympanum (39.5% vs 9.2%), and protympanum (23.7% vs 6.6%). No statistically significant differences were found for epitympanum (98.7% vs 90.8%), antrum (64.5% vs 52.6%), and mastoid (26.3% vs 32.9%). Statistically significant radiological overestimation of facial nerve canal dehiscence (54.0% vs 25.0%) and invasion of tegmen tympani (39.5% vs 19.7%) is reported.

CONCLUSION

Radiologic cholesteatoma extension in different middle ear subspaces is overestimated compared to the intraoperative extension. The preoperative relevance of radiological retrotympanic extension might be limited in the choice of approach and transcanal endoscopic approach is always recommended first.

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.

"Leave me alone": anatomical structures and variations seen on computed tomography of the temporal bone

The anatomical structure of the temporal bone is quite complex. There are a great number of anatomical variations that are often confused with temporal bone pathologies, especially fractures. It is important that radiologists and surgeons be able to recognize such variations.

The Effect of Anteriorly Located Sigmoid Sinus on Postoperative Hearing Gains: A Case-Control Study

There are many studies on the effects of temporal bone anatomical variations on a mastoid pneumatization. Considering the effects of the anatomic variations on mastoid pneumatization, it is considered that many anatomic variations may affect graft success rates and postoperative hearing threshold gains. We aimed to evaluate the effects of various anatomic variations on postoperative hearing gains among patients undergoing tympanoplasty. This retrospective cohort study conducted in a tertiary-care university hospital. This study enrolled 57 patients who underwent primary type 1 tympanoplasty operation using the temporal muscle fascia. The patients were divided into two groups as those with an anteriorly located sigmoid sinus (group 1), and no anatomic variation (group 2). Airway gain values at the frequency range of 250 Hz-8000 Hz and pure tone average (PTA) value were calculated preoperatively and at postoperative sixth month. The gains attained by the patient groups with anatomic variations were compared with group 2. There were significant differences between Group 1 and Group 2 in terms of the airway frequencies of 250, 500, 2000, 4000 Hz, and PTA value. We detected a lesser postoperative hearing gain in patients with an anteriorly located SS. We believe that anatomic variations that may affect middle ear and mastoid cavity may also affect postoperative hearing gain.

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.

Limits in endoscopic ear surgery

BACKGROUND

In recent decades, endoscopic ear surgery (EES) has been rapidly evolving, expanding its boundaries from the middle ear to the lateral skull base. Nonetheless, the advantages of the endoscopic technique are associated with a number of intrinsic limitations.

METHODS AND OBJECTIVE

A narrative review was conducted to investigate the current limits of EES, analyzing the different otologic and skull base surgery procedures.

RESULTS

Limitations of EES can be divided into general and procedure-related. General limitations have been extensively described in the literature and are related to the bidimensional image provided by the endoscope, as well as the one-handed surgical technique and its implications in the management of bleeding. Procedure-related limits are continuously evolving and are also discussed in the present review.

CONCLUSION

Although endoscope use is intrinsically associated with general limitations, these have been systematically overcome by the refinement of the surgical technique as a consequence of the increasing surgical experience gained over the last 20 years. The main limits of EES are currently associated with specific procedure- and disease-related situations. This review describes the general limitations and their management, as well as the current limits in the endoscopic management of various otologic diseases, from the external ear to the lateral skull base.

Computational Optimization of Notch Spacing for a Transnasal Ear Endoscopy Continuum Robot

This paper presents a computational framework to optimize the visual coverage attainable by a notched-tube continuum robotic endoscope inside the middle ear cavity. Our framework combines anatomically-accurate geometric (mesh) models of the middle ear with a sampling-based motion planning algorithm (RRT) and a ray-casting procedure to quantify what regions of the middle ear can be accessed and visualized by the endoscope. To demonstrate the use of this framework, we run computer simulations to investigate the effect of varying the distance between each pair of consecutive flexure elements (i.e., notches) in our robotic endoscope.

Endoscopic Management of Primary Acquired Cholesteatoma

Endoscopic ear surgery is increasingly accepted as a primary modality for cholesteatoma surgery. A major advantage is the enhanced visualization of the middle ear in traditionally poorly accessible locations by the microscope. We discuss novel techniques for selective mastoid obliteration when a canal wall down mastoidectomy is necessary. Postoperatively, indications for non-echo planar diffusion-weighted imaging MRI versus second-look surgery are discussed. Finally, outcome data for endoscopic versus microscopic ear surgery are reviewed, which show equivalent outcomes regarding residual and recurrent disease, similar rates of complications, decreased pain, and shorter healing time.

The relationships among mastoid air cell development, tympanic sinus depth, and residual disease after surgery in children with congenital cholesteatoma

Background: Mastoid development, tympanic sinus depth, and residual disease after surgery for congenital cholesteatoma are probably related, but these relationships have not been examined in detail.Aims/objectives: This study aimed to clarify the relationships between the abovementioned factors. Materials and Methods: The subjects were 31 patients with congenital cholesteatoma (stage III or IV in Potsic's staging system) that underwent mastoidectomy. The cross-sectional area of the mastoid air cells was measured as described previously. Tympanic sinus depth was classified into A-C using Marchioni et al.'s system.Results: Patients with deep tympanic sinuses or residual disease exhibited significantly greater mastoid air cell development. However, little residual disease was found in the mastoid air cells. Conversely, residual disease was observed more frequently in the patients with deep tympanic sinuses.Conclusions and significance: After surgery for congenital cholesteatoma, residual disease is more likely to occur in patients with marked mastoid growth, possibly because they have deep tympanic sinuses. Cases in which congenital cholesteatoma spreads to the mastoid air cells are classified as stage IV in Potsic's system, but our findings indicate that invasion into a deep tympanic sinus is more important than invasion into the mastoid air cells.

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.

Supratubal recess and sinus tympani: CT analysis of middle ear hidden areas

Background

High-resolution computed tomography (HRCT) magnifies the role of preoperative imaging for detailed middle ear anatomy particularly its hidden area. The purpose of the current study was to assess the sinus tympani (ST) and supratubal recess (STR) by HRCT, to create CT classification of the STR depth, and to study the relationship between ST types and the new STR grades.

Results

In HRCT of non-pathological temporal bones of 100 subjects (200 ears), measurements of the STR and ST were calculated, registered, and analyzed. The depth of the STR was classified into grade 1 with depth less than 3 mm, grade 2 with depth ranged between 3 and 5 mm, and grade 3 with depth more than 5 mm. The mean STR length, width, and height were 4.17 ± 0.86, 3.55 ± 0.65, and 3.64 ± 0.7 mm, respectively, while the ST mean length and width of were 2.52 ± 0.5 and 1.82 ± 0.78 mm, respectively, without significant differences between either sexes or sided. The ST types were found to be type A in 56 ears (28%), type B in 142 ears (71%), and type C in 2 ears (1%). The STR grading was grade 1 in 12 ears (6%), grade 2 in 160 ears (80%), and grade 3 in 28 ears (14%) without significant relationship between ST types and STR grading (P = 0.3).

Conclusion

The current study provided reliable and applicable methods of CT assessment of STR and ST that can help to predict the degree of surgical visibility of the ST and STR during ear surgery.

Facial sinus endoscopic evaluation, radiologic assessment, and classification

OBJECTIVES

To describe facial sinus anatomy from an endoscopic perspective and present a radiologic classification.

METHODS

Facial sinus was studied by endoscopy and high-resolution computed tomography (HRCT) scan in 39 temporal bones that underwent exclusive transcanal endoscopic approach. A radiomorphologic classification based on the relationship between the facial sinus and the mastoid portion of the facial nerve is created as follows. In type A facial sinus, the pneumatization of the facial sinus did not extend medially or posteriorly to the mastoid portion of the facial nerve. In type B facial sinus, the pneumatization extended posteriorly to the mastoid portion of the facial nerve. In type C facial sinus, the pneumatization extended posteriorly and medially to the mastoid portion of the facial nerve.

RESULTS

In all the specimens that underwent HRCT (n = 31), facial sinus could be identified, and its depth classified, in relation to the facial nerve. In this group, 58% type A, 29% type B, and 13% type C facial sinuses were identified. In all the specimens (n = 39), the facial sinus could be assessed by means of an exclusive endoscopic transcanal approach, and anatomical variants of the chordiculus, previously known as chordal ridge, could be described: ridge (39%), bridge (18%), incomplete (15%), and absent (28%).

CONCLUSION

Endoscopic exploration of the retrotympanum guarantees a very good exposure of the facial sinus, allowing detailed anatomic descriptions of its conformation and relationships with other structures. Improvement in our knowledge of its anatomy might decrease the possibility of residual disease during cholesteatoma surgery. Angled endoscopes (e.g. 45 °, 70 °) can guarantee a better view of the facial sinus.

LEVEL OF EVIDENCE

NA. Laryngoscope, 128:2397-2402, 2018.

Through the Eustachian Tube and Beyond: A New Miniature Robotic Endoscope to See Into The Middle Ear

This paper presents a novel miniature robotic endoscope that is small enough to pass through the Eustachian tube and provide visualization of the middle ear (ME). The device features a miniature bending tip previously conceived of as a small-scale robotic wrist that has been adapted to carry and aim a small chip-tip camera and fiber optic light sources. The motivation for trans-Eustachian tube ME inspection is to provide a natural-orifice-based route to the ME that does not require cutting or lifting the eardrum, as is currently required. In this paper, we first perform an analysis of the ME anatomy and use a computational design optimization platform to derive the kinematic requirements for endoscopic inspection of the ME through the Eustachian tube. Based on these requirements, we fabricate the proposed device and use it to demonstrate the feasibility of ME inspection in an anthropomorphic model, i.e. a 3D-printed ME phantom generated from patient image data. We show that our prototype provides > 74% visibility coverage of the sinus tympani, a region of the ME crucial for diagnosis, compared to an average of only 6.9% using a straight, non-articulated endoscope through the Eustachian Tube.