Volume of Mastoid Pneumatization: Three-Dimensional Reconstruction with Ultrahigh-Resolution Computed Tomography

Interpretation of the nine-step test for Eustachian tube function should consider mastoid cavity volume

INTRODUCTION

The modified nine-step test is a classical method for evaluating Eustachian tube function. However, clinical interpretation of the increased maximal difference in middle ear pressure (mdMEP) in the modified nine-step test is unknown. We hypothesised that the different reservoir effects of the mastoid cavity can bias the results of the modified nine-step test.

METHODS

A total of 108 consecutive participants (216 ears) were retrospectively screened. Of these, 55 participants (82 ears) who met the inclusion/exclusion criteria were enrolled. The volumetric results of the mastoid cavity, parameters of the modified nine-step test (mdMEP, middle ear pressure, tympanic membrane compliance), and demographic data were analysed.

RESULTS

A significant negative correlation was found between mdMEP and mastoid cavity volume (R = .467, p < .001). Ears with mdMEP >70 daPa showed poor pneumatization in the mastoid cavity, with volumes less than 3000 mm3 (10th percentile of all ears analysed). Ears with mastoid cavity volumes lower than the 25th percentile showed a significantly higher mdMEP (p < .001). Patients with mastoid cavity volumes higher than the 75th percentile were significantly younger (p < .001). Multivariate regression analysis for mdMEP showed a good fit (R = .854) using factors including middle ear pressure, admittance and, most importantly, the reciprocal of mastoid volume (Beta = 0.752, p < .001).

CONCLUSIONS

The mdMEP, the main parameter of the modified nine-step test, was negatively correlated with the mastoid cavity volume. Therefore, the results of the modified nine-step test should be interpreted with consideration of mastoid cavity volume.

The association between high jugular bulb and mastoid pneumatization in adults

Purpose

The purpose of this study was to analyze the relationship between the degree of high jugular bulb (HJB) and mastoid pneumatization using high-resolution computed tomography (HRCT).

Methods

Between April 2019 and June 2022, HRCT of the temporal bone was retrospectively analyzed in 1,025 patients. By excluding the other coexistent pathologies, 113 patients with HJBs were recruited for the study. The degree of the HJBs were defined as follows: Grade I, JB situated between inferior annulus of tympanic membrane and cochlear basal turn (CBT). Grade II, JB situated between CBT and lateral semicircular canal (LSC). Grade III, JB situated above LSC. The volume of mastoid pneumatization was based on HRCT images using a 3D reconstruction.

Results

There were 32 male and 81 female subjects (mean age, 41.2 ± 14.0 years; age range, 18-80 years). The male group included 16 Grade I, 28 Grade II and 6 Group III HJB subjects. The female group included 38 Grade I, 62 Grade II and 31 Group III HJB cases. In the different groups of HJB, the mastoid cell volume differences were also not statistically significant (p = 0.165). In the classification, Grade II was most common (90/181, 49.7%).

Conclusion

This study found no correlation between mastoid air cell volume and HJB, suggesting that HJB may not affect the mastoid air cell development and disease occurrence. These data must be considered exploratory, requiring more extensive cross-sectional studies.

Imaging of Alternobaric Facial Palsy: An Etiologic Hypothesis

OBJECTIVE

To report a case of alternobaric facial palsy (AFP) with a hyperpneumatized temporal bone and to review the relevant literature in order to propose a new facet of AFP pathogenesis.

METHODS

A patient with a hyperpneumatized temporal bone was found to have recurrent episodes of facial palsy associated with air travel. Systematic review of PubMed, Cochrane Library, and Embase characterized all articles related to transient facial palsy associated with altitude changes or diving with a focus on demographics and imaging findings.

RESULTS

A 25 year-old male was referred for recurrent facial palsy associated with commercial air travel. Imaging demonstrated a hyperpneumatized and well-aerated temporal bone. Total air cell volume was calculated to be 8.59 cc on the affected side. A systematic review of the literature identified 49 cases of AFP. Mean age was 34 years old and 80% were male. Twelve cases had imaging of the temporal bone for evaluation, of which 85% demonstrated at least 1 area of hyperpneumatization. Hyperpneumatization was most frequently encountered in the mastoid, zygomatic root, and inferior petrous apex.

CONCLUSION

Hyperpneumatization of the temporal bone is critical to AFP etiology as it predicts higher middle ear pressure, if atmospheric pressure changes cannot be equilibrated, via reduced efficacy of normal tympanic membrane pressure buffering. This hypothesis helps to better account for the rarity of the condition and male preponderance.

Application of symmetry evaluation to deep learning algorithm in detection of mastoiditis on mastoid radiographs

As many human organs exist in pairs or have symmetric appearance and loss of symmetry may indicate pathology, symmetry evaluation on medical images is very important and has been routinely performed in diagnosis of diseases and pretreatment evaluation. Therefore, applying symmetry evaluation function to deep learning algorithms in interpreting medical images is essential, especially for the organs that have significant inter-individual variation but bilateral symmetry in a person, such as mastoid air cells. In this study, we developed a deep learning algorithm to detect bilateral mastoid abnormalities simultaneously on mastoid anterior-posterior (AP) views with symmetry evaluation. The developed algorithm showed better diagnostic performance in diagnosing mastoiditis on mastoid AP views than the algorithm trained by single-side mastoid radiographs without symmetry evaluation and similar to superior diagnostic performance to head and neck radiologists. The results of this study show the possibility of evaluating symmetry in medical images with deep learning algorithms.

Effects of mastoid and middle-ear volume on graft success and hearing outcomes in paediatric tympanoplasty

Objective

To examine the effects of mastoid and middle-ear volume on the anatomical and functional success of type 1 tympanoplasty in paediatric patients.

Methods

This study included 45 paediatric patients who underwent type 1 cartilage tympanoplasty. Patients’ demographic data, pre- and post-operative audiological evaluation results, and post-operative graft status were evaluated. Middle-ear and mastoid cavity volumes were calculated (in cubic centimetres) using temporal bone high-resolution computed tomography. Middle-ear and mastoid cavity volume values were compared between patients with and without post-operative anatomical and functional success.

Results

Anatomical success was achieved in 82.2 per cent of patients (n = 37), and functional success in 68.9 per cent (n = 31). When anatomical success and failure groups were compared, a statistically significant difference was found in mean mastoid volume (p = 0.037), while there was no significant difference in relation to mean middle-ear volume (p = 0.827). The comparison of functional success and failure groups revealed no significant difference in mean mastoid volume (p = 0.492) or middle-ear volume (p = 0.941).

Conclusion

The study showed that mastoid pneumatisation volume affects surgical success in paediatric tympanoplasty.

Anatomical Variations of the Epitympanum and the Usable Space for Middle Ear Implants Analyzed With CT-assisted Imaging Using a Tablet-based Software

OBJECTIVE

To evaluate interindividual anatomical variations of the epitympanum and the usable space for implantation of active middle ear implants (AMEI) as well as the usefulness of a tablet-based software to assess individual anatomy on computed tomography (CT) scans.

PATIENTS

CT scans of 126 patients, scheduled for cochlea implantation (50.8% men; 0.6-90.0 yr) without middle ear malformations or previous middle ear surgery and with slice thickness ≤0.7 mm were analyzed.

MAIN OUTCOME MEASURES

Since no standardized measurements to assess the size of the epitympanum are available, relevant distances were defined according to anatomical landmarks. Three independent raters measured these distances using a tablet-based software. Interrater correlation was computed to evaluate the quality of the measurement process. Descriptive data were analyzed for validation and for evaluation of interindividual anatomical variations. Influence of age and sex on the taken measurements was assessed.

RESULTS

No relevant correlation between age or sex and the anatomy of the epitympanum was found. Interrater correlation ranged from Spearman's ρ = 0.3-0.9 and there were significant differences between individual rater results for various combinations. Descriptive data revealed high interindividual anatomical variance of the epitympanum, especially regarding the distance between incus and skull base.

CONCLUSION

The reported descriptive data regarding the anatomy of the epitympanum emphasizes the importance of preoperative planning, especially since the height of the epitympanum showed great interindividual variance potentially limiting implantation of AMEIs. The herein used tablet-based software seems to be convenient for preoperative assessment of individual anatomy in the hand of otosurgeons.

Performance of deep learning to detect mastoiditis using multiple conventional radiographs of mastoid

Objectives

This study aimed to compare the diagnostic performance of deep learning algorithm trained by single view (anterior-posterior (AP) or lateral view) with that trained by multiple views (both views together) in diagnosis of mastoiditis on mastoid series and compare the diagnostic performance between the algorithm and radiologists.

Methods

Total 9,988 mastoid series (AP and lateral views) were classified as normal or abnormal (mastoiditis) based on radiographic findings. Among them 792 image sets with temporal bone CT were classified as the gold standard test set and remaining sets were randomly divided into training (n = 8,276) and validation (n = 920) sets by 9:1 for developing a deep learning algorithm. Temporal (n = 294) and geographic (n = 308) external test sets were also collected. Diagnostic performance of deep learning algorithm trained by single view was compared with that trained by multiple views. Diagnostic performance of the algorithm and two radiologists was assessed. Inter-observer agreement between the algorithm and radiologists and between two radiologists was calculated.

Results

Area under the receiver operating characteristic curves of algorithm using multiple views (0.971, 0.978, and 0.965 for gold standard, temporal, and geographic external test sets, respectively) showed higher values than those using single view (0.964/0.953, 0.952/0.961, and 0.961/0.942 for AP view/lateral view of gold standard, temporal external, and geographic external test sets, respectively) in all test sets. The algorithm showed statistically significant higher specificity compared with radiologists (p = 0.018 and 0.012). There was substantial agreement between the algorithm and two radiologists and between two radiologists (κ = 0.79, 0.8, and 0.76).

Conclusion

The deep learning algorithm trained by multiple views showed better performance than that trained by single view. The diagnostic performance of the algorithm for detecting mastoiditis on mastoid series was similar to or higher than that of radiologists.

Volumetric analysis of the maxillary, sphenoid and frontal sinuses: A comparative computerized tomography based study

OBJECTIVE

To study volume characteristics of the maxillary, sphenoid and frontal sinuses among healthy Caucasians adults, using computed tomography (CT) scans.

METHODS

A retrospective, case series study in a single academic center, CT scans of 201 consecutive adult subjects, performed between January and September 2014, were reviewed for the volume and dimensions of the paranasal sinuses. Patients with documented sinus pathology or lack of pneumatization were excluded. The study population was subdivided by gender and age (50 men age 25-64; 51 men age ≥65; 50 women age 25-64, and 50 women age ≥65).

RESULTS

The mean volume of maxillary, sphenoid and frontal sinuses in the four groups were 12.75±4.38 cc; 4.00±1.99 cc and 2.92±2.57 cc, respectively. In both genders, older patients demonstrated a significantly lower volume of the maxillary and sphenoid sinuses (14.81±3.96 cc vs. 11.82±4.28 cc and 4.84±1.97 vs. 3.84±1.89 cc respectively; p<0.001). No age related difference was found in the frontal sinus. Males had significantly larger sinus volumes than females (p<0.001): maxillary 14.38±(4.64) vs. 12.23±(3.82) cc, sphenoid 4.74±(2.06) vs. 3.55±(1.73) cc, frontal 3.74±(2.97) vs. 3.21±(2.79) cc. No synergistic effect of age and gender was found.

CONCLUSION

Volumes of the paranasal sinuses correlates with age and gender. Age related volume degeneration is expected in the maxillary and sphenoid sinuses. This volume reduction may influence future surgical and therapeutic approaches in the geriatric population.

Pneumatization of Mastoid Air Cells, Temporal Bone, Ethmoid and Sphenoid Sinuses. Any Correlation?

The aim of this study is to assess the pneumatization of the paranasal sinuses (PNS) and other parts of temporal bone such as mastoid air cells and to investigate if there was any association between the aeration of these structures among the three major ethnic groups in Malaysia (Malay, Chinese, Indian) as this would be representative of Asia. A retrospective review of 150 computed tomography (CT) scans of PNS and temporal bones was done and analysed. The pneumatization of each area was obtained and compared using statistical analysis. Patients with a history of previous medical or surgical problems in the intended areas were excluded from the study. The pneumatization of the mastoid air cells and other temporal bone parts were noted to be symmetrical in more than 75 %. There was a positive correlation between the pneumatization of mastoid air cells and that of the sphenoid sinus. The prevalence of Agger nasi, Haller's and Onodi cells was observed to be significantly higher in the Chinese group. Preoperative assessment of the temporal bone and PNS with CT scan may be helpful in the evaluation of their anatomical landmark and decrease the possibility of surgical complications related to 3D structures.

Temporal bone Pneumatization in Otosclerosis

Objectives

To determine whether there is a difference in the pneumatization of temporal bones with otosclerosis versus normal temporal bones.

Methods

A retrospective study of 46 ears from 24 adult patients with otosclerosis and 64 ears from 47 adult patients in a control group. The study group included temporal bone CT scans available from patients with otosclerosis. The control group consisted of patients who had temporal bone CTs for reasons likely unrelated to a history of middle ear disease. Data were obtained with a virtual reality system that allows three-dimensional manipulation and analysis.

Results

The temporal bone pneumatization for the otosclerosis group was 4.82 ± 2.27 cm3 vs 6.06 ± 2.71 cm3 for the control group. Two-sample t test analysis revealed no statistical significance ( P = 0.059) between pneumatization in the control vs otosclerosis groups.

Conclusion

There is no difference in temporal bone pneumatization between patients with otosclerosis and a control population. Therefore, temporal bone pneumatization by itself is not an adequate explanation for the apparent protective effect of otosclerosis against otitis media. © 2008 American Academy of Otolaryngology-Head and Neck Surgery Foundation. All rights reserved.

A quantitative method for the evaluation of three-dimensional structure of temporal bone pneumatization

Temporal bone pneumatization has been included in lists of characters used in phylogenetic analyses of human evolution. While studies suggest that the extent of pneumatization has decreased over the course of human evolution, little is known about the processes underlying these changes or their significance. In short, reasons for the observed reduction and the potential reorganization within pneumatized spaces are unknown. Technological limitations have limited previous analyses of pneumatization in extant and fossil species to qualitative observations of the extent of temporal bone pneumatization. In this paper, we introduce a novel application of quantitative methods developed for the study of trabecular bone to the analysis of pneumatized spaces of the temporal bone. This method utilizes high-resolution X-ray computed tomography (HRXCT) images and quantitative software to estimate three-dimensional parameters (bone volume fractions, anisotropy, and trabecular thickness) of bone structure within defined units of pneumatized spaces. We apply this approach in an analysis of temporal bones of diverse but related primate species, Gorilla gorilla, Pan troglodytes, Homo sapiens, and Papio hamadryas anubis, to illustrate the potential of these methods. In demonstrating the utility of these methods, we show that there are interspecific differences in the bone structure of pneumatized spaces, perhaps reflecting changes in the localized growth dynamics, location of muscle attachments, encephalization, or basicranial flexion.

Pressure equilibration in the penguin middle ear

CONCLUSIONS

King penguins have a venous structure in the form of a corpus cavernosum (CC) in their middle ear (ME) submucosa. The CC may be viewed as a special organelle that can change ME volume for pressure equilibration during deep-sea diving it is a pressure regulating organelle (PRO). A similar CC and muscles also surround the external ear (EE) and may constrict it, isolating the tympanic membrane from the outside. A CC was previously found also in the ME of marine diving mammals and can be expected to exist in other deep diving animals, such as marine turtles.

OBJECTIVES

Marine animals require equalization of middle ear (ME) pressure when diving hundreds or thousands of meters to catch prey. We investigated what mechanism enables king penguins to protect their ME when they dive to great depths.

MATERIALS AND METHODS

Biopsies and serial sections of the ME and the EE of the deep diving king penguin (Aptenodytes patagonicus) were examined microscopically.

RESULTS

It was demonstrated that the penguin ME has an extensive network of small and large submucosal venous sinuses. This venous formation, a corpus cavernosum, can expand and potentially 'flood' the ME almost completely on diving, thus elevating ME pressure and reducing the ME space. The EE has a similar protective mechanism.

The mastoid as a functional rate-limiter of middle ear pressure change

INTRODUCTION

The physiological function of the mastoid air cell system (MACS) with respect to middle ear (ME) pressure-regulation remains controversial because predictive mathematical models and experimental data to formulate and test hypotheses are lacking.

OBJECTIVE

A mathematical description of MACS volume effects on the rate of ME pressure change is presented; the agreement between published data and model prediction is examined for consistency with the hypothesis that the MACS acts as a functional rate-limiter of ME pressure change, and an explanation for the relationship between MACS volume and otitis media is discussed.

METHODS

The mathematical description shows that the value of a single, free parameter, termed the "MACS buffering efficiency" (M) determines if MACS volume affects the rate of ME pressure change caused by diffusive gas exchange. The MACS serves no rate-limiting function for M=0, acts as a gas sink for M>1 and acts as a gas reserve (rate-limiter) for M<1.

RESULTS

Fitting the model equation to published adult human data yielded an estimate for M of 0.2. This implies that larger MACS volumes are associated with lesser rates of change in ME pressure caused by diffusive gas exchange and lesser required frequencies of effective Eustachian tube openings to maintain near ambient ME pressures.

CONCLUSION

If well-controlled studies confirm M<1 for children and adults, larger MACS volumes will increase the time required to develop sufficient ME underpressures to cause otitis media by hydrops ex vacuo during transient or prolonged periods of Eustachian tube dysfunction.

Morphometric examination of the paranasal sinuses and mastoid air cells using computed tomography

BACKGROUND

The paranasal sinuses and mastoid air cells vary considerably in size and shape from person to person. The main structures are pneumatic. In this study, we investigated the relationship between right and left sides and evaluated the volume changes according to age and sex.

METHODS

Of all patients attending the radiology department, 91 cases without paranasal sinuses and mastoid air cells pathology (i.e., inflammation, operation or trauma) were selected for evaluation. Axial computed tomography (CT) scans were obtained for both paranasal sinuses and temporal bones. In all scans, the volumes of each area (maxillary sinus, frontal sinus, sphenoid sinus and mastoid air cell) were calculated and analyzed statistically.

RESULTS

The volumes of paranasal sinuses and mastoid air cells increased with age and women had a lower mean volume. There was a positive correlation between right-left and ipsilateral structures (paranasal sinuses and mastoid air cells).

CONCLUSIONS

These results are helpful in understanding the normal and pathological conditions of the paranasal sinuses and the mastoid air cells.

Volume variation of mastoid pneumatization in different age groups: a study by three-dimensional reconstruction based on computed tomography images

Although there have been some reports that measured the size of mastoid pneumatization, only a few studies have reported the age-related variations in the mastoid air cell system using three-dimensional (3D) reconstruction techniques of computed tomography (CT) images. We performed a retrospective, cross-sectional study. A 3D reconstruction based on CT images was performed on 199 ears of 102 patients (age range 6-84 years) without otologic disease by a surface-rendering algorithm. The results showed that mastoid pneumatization continued to grow until the third decade. Thereafter, it declined slowly, and then rapidly after the seventh decade. No statistically significant difference was found between male and female or between right and left sides. There was a significant difference between the larger and smaller sides of individuals. The volume measurement technique based on the 3D reconstruction technique reported here is widely available, highly accurate and easy to perform.

Mastoid and Tympanic Membrane as Pressure Buffers: A Quantitative Study in a Middle Ear Cleft Model

HYPOTHESIS

The tympanic membrane (TM) and mastoid air cells are measurable pressure buffers of the middle ear (ME).

BACKGROUND

Pressure homeostasis of the ME is maintained approximately atmospheric by mechanisms that neutralize (buffer) pressure fluctuations, two of which are the TM and mastoid.

MATERIALS AND METHOD

Negative pressures were induced by volume changes in an artificial ME model. Those were recorded directly while using a rigid or a flexible TM with "mastoids" of various sizes.

RESULTS

In the rigid TM model, the volume changes correlated linearly with the induced pressures and were confirmed to fit Boyle's law. In the flexible TM model, the pressure/volume correlation was nonlinear up to -50 mmH2O, where the TM was maximally displaced (approximately 25 mm3), became rigid, and constituted 75%, 41%, and 33% of the buffering gained in tandem with the "mastoid" in a model having a "mastoid" of 0, 5, and 10 mL, respectively. Altogether, a large "mastoid" required a greater volume change than a small one to induce the same pressure.

CONCLUSIONS

The mastoid air volume "dilutes" pressure changes relatively to its size: the volume change required to alter a given pressure in an average (6 mL) mastoid is six-fold that which is needed in a small (1 mL) mastoid. ME volume reduction by TM retraction buffer negative ME pressures. This maximal ME volume change is constant for a "normal" TM. Therefore, it is the ME with the small mastoid that is most vulnerable to pressure changes and may develop compensatory buffering mechanisms, e.g., additional TM retraction (atelectasis) and/or ME volume reduction by fluid accumulation.

Aeration following intact canal wall mastoidectomy

This study examines the prevalence and extent of re-aeration of the mastoid cavity following intact canal wall (ICW) mastoidectomy. Temporal bone computed tomography scans from patients with prior unilateral ICW mastoidectomy were identified. Three-dimensional volume reconstruction of the temporal bone was performed to measure aeration bilaterally. Thirty-five scans were analyzed; 16 (46%) showed good aeration in the operated ear and 19 showed poor aeration. The aeration (volume) in the surgical ears and the contralateral ears was significantly less than that in subjects without a history of ear disease. Those with poor aeration were more likely to require additional surgery. For temporal bone pairs with greater volume in the operated ear, the average difference was 1.3 cm3. Surgical creation of a mastoid cavity does not produce a large increase in aeration as compared with the contralateral ear. Following surgery, mastoid opacification may presage recurrent disease. Routine use of mastoidectomy in an attempt to improve aeration is not advocated.

Clinical significance of incidental magnetic resonance image abnormalities in mastoid cavity and middle ear in children

OBJECTIVE

Magnetic resonance imaging of the head may reveal incidental findings in paranasal sinuses. The purpose of this study was to discover whether similar changes could be identified in the mastoid cavity and middle ear as well.

METHODS

A group of 50 children undergoing magnetic resonance imaging of the head for suspected intracranial pathology were prospectively gathered. Their parents completed a questionnaire concerning each child's medical history connected with acute otitis media. Otoradiologists evaluated the pictures for mastoid cavity and middle ear and paranasal sinus abnormalities.

RESULTS

In six (12%) children, magnetic resonance imaging detected abnormalities resembling acute inflammatory changes, although none had had acute otitis media during the preceding last 3 months. Abnormalities detected in the paranasal sinuses were not correlated with abnormalities in the mastoid cavity and middle ear.

CONCLUSIONS

High signal intensity in magnetic resonance images from the mastoid cavity and middle ear may be incidental and without any clinical significance. These findings must be interpreted together with knowledge of the child's medical condition and clinical examination of the ears.