Comparison of tympanometric volume measurement with temporal bone CT findings in the assessment of mastoid bone pneumatization in chronic otitis media patients.

OBJECTIVE: Since mastoid bone aeration is a pressure buffer for the middle ear, it can be accepted as a prognostic factor for tympanoplasty. Temporal bone computed tomography (TBCT) is a primary method for estimating mastoid aeration. However, due to the risk of radiation and its high cost, there is a need for a more straightforward, faster, and more reliable method in non-complicated chronic otitis media cases (COM). Tympanometric volume measurement might be used for this purpose. This study investigated tympanometric volume measurement's reliability in showing mastoid bone aeration by comparing tympanometric volume measurement with TBCT aeration grading. PATIENTS AND METHODS: Preoperative tympanometric volume measurements were performed in patients who underwent audiological examination and temporal computerized tomography (CT) with the diagnosis of COM and sequela of COM without discharge for the last three months and were indicated for surgery. CT was classified into six grades: grade 0: there is no aeration, sclerotic mastoid; grade 1: pneumatization only in the mastoid antrum; grade 2: <25% pneumatization; grade 3: 25-50% pneumatization; grade 4: >50 pneumatization, grade 5: full pneumatization. Averages of tympanometric volume values were determined according to CT degrees. RESULTS: 48 left and 52 right ears (n: 100) of 81 patients, 24 females and 57 males, were included in the study. The mean age was 37.69±13.38. Mastoid pneumatization grades of patients were 32 grade 0, 23 grade 1, 16 grade 2, 14 grade 3, 11 grade 4, and 4 grade 5, respectively. Each grade's mean tympanometric volume (mL) was grade 0: 1.1594, grade 1: 1.6991, grade 2: 2.2250, grade 3: 3.0471, grade 4: 4.0327, and grade 5: 2.9775. CONCLUSIONS: There is a statistically significant relationship between tympanometrically measured ear volume and mastoid degrees of pneumatization on temporal bone tomography. As the degree of mastoid aeration increases, the tympanometric volume also increases. According to the results of this study, tympanometric air volume can be used reliably in the preoperative evaluation of mastoid bone aeration in cases of simple COM without ear drainage.

An inter-observer assessment of mastoid pneumatization and degree classification using sigmoid sinus: comparing two levels of temporal bone computed tomograms.

BACKGROUND: The degree of mastoid pneumatization of the temporal bone (TB) has been implicated in the pathogenesis of TB diseases and surgical implications, and planning of a few otologic surgeries. However, there is lack of consensus in the classification of the degree of pneumatization. This study aimed to suggest a simple, quick, and less-burden classification system for assessing and rating the degree of pneumatization by comparing two levels of TB computed tomographs (CTs) using the SS as a reference in an inter-observer assessment among otologists. METHODS: This was a randomized pilot survey among otologists. A questionnaire consisting of different axial CTs of TB taken at two levels: the level of malleoincudal junction (MIJ) and the level of lateral semicircular canal (LSCC), with different pneumatization patterns, was used to assess participants' impressions of the degree of pneumatization. The terms "hypo-," "moderate," "good," and "hyper-" pneumatization were listed as options to rate their impressions on the degree of mastoid pneumatization of the TB images using the SS as a reference structure. Likert scale was used to assess their level of agreement or disagreement with using SS as a reference in evaluating mastoid pneumatization. RESULTS: Participants who correctly rated images taken at the level of LSCC according to their respective degree of pneumatization were significantly higher (p < 0.05) regardless of their year of experience compared to those that correctly rated corresponding images taken at the level of MIJ. A 76% positivity in their level of agreement with the use of sigmoid sinus in evaluating mastoid pneumatization was observed on the Likert-scale chart. CONCLUSION: Findings from this study suggest that evaluating air cells around the SS at the level of LSCC on CTs could be easier in assessing and classifying the degree of mastoid pneumatization.

Statistical classification methods for estimating sex based on five skull traits: A nonmetric assessment using 3D CT models.

Five cranial nonmetric traits for sex estimation for sex estimation are classified by score according to geometry. The population of origin is one of the factors influencing cranial nonmetric traits. Moreover, among the five cranial traits, the robust traits for estimating sex varied across population. The aim of this study is to suggest the most useful method for sex estimation and demonstrate the need of a suitable method for each population. One-hundred thirty-five three-dimensional skull images from 21st century Korean autopsy cadavers were evaluated using the ordinal scoring system of five cranial nonmetric traits as outlined in Buikstra & Ubelaker (1994). All scores of each trait were analyzed by linear discriminant and decision tree analyses for sex estimation. The frequency of each trait was analyzed and compared to populations from other studies. The accuracy for both sexes was 88.1% by discriminant analysis and 90.4% by decision tree. The traits with the highest accuracy were the glabella and mastoid process in both discriminant analysis and decision tree. Sex estimation in modern Korean cadavers using the cranial nonmetric method was shown to be highly accurate by both discriminant analysis and decision tree. When comparing the pattern of frequency scores in this study with those of other populations, the pattern of trait scores for estimating sex was different for each population, even among populations in the same Asian region, which suggests the need for methods suited for specific populations.

Postoperative radiological assessment of the mastoid facial canal in cochlear implant patients in correlation with facial nerve stimulation.

OBJECTIVES: To correlate the radiological assessment of the mastoid facial canal in postoperative cochlear implant (CI) cone-beam CT (CBCT) and other possible contributing clinical or implant-related factors with postoperative facial nerve stimulation (FNS) occurrence. METHODS: Two experienced radiologists evaluated retrospectively 215 postoperative post-CI CBCT examinations. The mastoid facial canal diameter, wall thickness, distance between the electrode cable and mastoid facial canal, and facial-chorda tympani angle were assessed. Additionally, the intracochlear position and the insertion angle and depth of electrodes were evaluated. Clinical data were analyzed for postoperative FNS within 1.5-year follow-up, CI type, onset, and causes for hearing loss such as otosclerosis, meningitis, and history of previous ear surgeries. Postoperative FNS was correlated with the measurements and clinical data using logistic regression. RESULTS: Within the study population (mean age: 56 ± 18 years), ten patients presented with FNS. The correlations between FNS and facial canal diameter (p = 0.09), wall thickness (p = 0.27), distance to CI cable (p = 0.44), and angle with chorda tympani (p = 0.75) were statistically non-significant. There were statistical significances for previous history of meningitis/encephalitis (p = 0.001), extracochlear-electrode-contacts (p = 0.002), scala-vestibuli position (p = 0.02), younger patients' age (p = 0.03), lateral-wall-electrode type (p = 0.04), and early/childhood onset hearing loss (p = 0.04). Histories of meningitis/encephalitis and extracochlear-electrode-contacts were included in the first two steps of the multivariate logistic regression. CONCLUSION: The mastoid-facial canal radiological assessment and the positional relationship with the CI electrode provide no predictor of postoperative FNS. Histories of meningitis/encephalitis and extracochlear-electrode-contacts are important risk factors. KEY POINTS: • Post-operative radiological assessment of the mastoid facial canal and the positional relationship with the CI electrode provide no predictor of post-cochlear implant facial nerve stimulation. • Radiological detection of extracochlear electrode contacts and the previous clinical history of meningitis/encephalitis are two important risk factors for postoperative facial nerve stimulation in cochlear implant patients. • The presence of scala vestibuli electrode insertion as well as the lateral wall electrode type, the younger patient's age, and early onset of SNHL can play important role in the prediction of post-cochlear implant facial nerve stimulation.

Radiologic Assessment of the Sinonasal Tract, Nasopharynx and Mastoid Cavity in Patients with SARS-Cov-2 Infection Presenting with Acute Neurological Symptoms.

BACKGROUND: Acute neurological sequela in patients with COVID-19 infection include acute thromboembolic infarcts related to cytokine storm and post infectious immune activation resulting in a prothrombotic state. Radiologic imaging studies of the sinonasal tract and mastoid cavity in patients with COVID-19 infection are sparse and limited to case series. In this report, we investigate the radiologic involvement of nasal cavity, nasopharynx, paranasal sinuses, and mastoid cavity in patients with SARS-CoV-2 infection who presented with acute neurological symptoms. METHODS: Retrospective review of medical records and neuroradiologic imaging in patients diagnosed with acute COVID-19 infection who presented with acute neurological symptoms to assess radiologic prevalence of sinus and mastoid disease and its correlation to upper respiratory tract symptoms. RESULTS: Of the 55 patients, 23 (42%) had partial sinus opacification, with no evidence for complete sinus opacification. The ethmoid sinus was the most commonly affected (16/55 or 29%). An air fluid level was noted in 6/55 (11%) patients, most commonly in the maxillary sinus. Olfactory recess and mastoid opacification were uncommon. There was no evidence of bony destruction in any of the studies, Cough, nasal congestion, rhinorrhea, and sore throat were not significantly associated with any radiological findings. CONCLUSION: In patients who present with acute neurological symptoms, COVID-19 infection is characterized by limited and mild mucosal disease within the sinuses, nasopharynx and mastoid cavity. LEVEL OF EVIDENCE: 4.

Preoperative risk assessment for predicting the opening of mastoid air cells in lateral suboccipital craniotomy for microvascular decompression.

OBJECTIVE: Opening of mastoid air cells (MACs), a complication of lateral suboccipital craniotomy for microvascular decompression (MVD), might cause cerebrospinal fluid (CSF) leakage and meningitis. Only a few studies have investigated the association of degree of MAC development and actual opening of MACs. The present study focused on preoperative risk assessment for predicting the opening of MACs. PATIENTS AND METHODS: The study included 204 consecutive patients who underwent MVD at our hospital between January 2014 and December 2018. We retrospectively collected clinical and neuroimaging data from electronic medical charts and discharge summaries. MACs were classified into four types according to neuroimaging data. Postoperative computed tomography (CT) was used to assess patients with and without CSF leakage into MACs. RESULTS: No CSF leakage was observed into types 1 and 2 MACs, but it was noted in 14 of 46 patients (30 %) with type 3 and 44 of 58 patients (76 %) with type 4 MACs. Opening of MACs during surgery could not be recognized in 33 (57 %). CSF rhinorrhea was noted in 1 of the 58 patients with CSF leakage into MACs and meningitis was not noted. CONCLUSION: Patients with types 3 and 4 MACs have a high risk of CSF leakage. Complete prevention of mild symptoms, such as ear obstruction, is challenging even if opened MACs are sealed, but serious complications, such as CSF rhinorrhea and meningitis, can be avoided. For cases in which preoperative CT reveals a high risk of opening of MACs, preventive closure should be performed.

The radioanatomical assessment of the Körner's septum.

PURPOSE OF THE STUDY: Körner's septum (KS) is a developmental remnant formed at the junction of mastoid and temporal squama, representing the persistence of the petrosquamosal suture. During mastoid surgery, it could be taken as a false medial wall of the antrum so that the deeper cells might not be explored. The aim of the study was to assess a Körner's septum prevalence and to analyze its topography. METHODS: The study was performed on 80 sets of cone-beam computed tomography (CBCT) images of temporal bone (41 male, 39 female, 160 temporal bones). Körner's septum was identified and its thickness was measured on axial sections at three points: at the level of superior semicircular canal (SCC), at the level of head of malleus (HM) and at the level of tympanic sinus (TS). RESULTS: KS was encountered at least in one point of measurements in 50 out of 80 sets of CBCT images (62.5%). The average thickness at the level of SCC was 0.87 ± 0.34 mm, at the level of HM was 0.99 ± 0.37 mm and at the level of TS was 0.52 ± 0.17 mm. CONCLUSIONS: Körner's septum is a common structure in the temporal bone-air cell complex. It is more often encountered in men. In half of the patients, it occurs bilaterally. However, in most of the cases it is incomplete with anterior and superior portions being the most constant.

Population Statistics Approach for Safety Assessment in Robotic Cochlear Implantation.

HYPOTHESIS: Descriptive statistics with respect to patient anatomy and image guidance accuracy can be used to assess the effectiveness of any system for minimally invasive cochlear implantation, on both an individual patient and wider population level. BACKGROUND: Minimally invasive cochlear implantation involves the drilling of a tunnel from the surface of the mastoid to cochlea, with the trajectory passing through the facial recess. The facial recess anatomy constrains the drilling path and places prohibitive accuracy requirements on the used system. Existing single thresholds are insufficient for assessing the effectiveness of these systems. METHODS: A statistical model of the anatomical situation encountered during minimally invasive drilling of the mastoid for cochlear implantation was developed. A literature review was performed to determine the statistical distribution of facial recess width; these values were confirmed through facial recess measurements on computed tomography (CT) data. Based on the accuracy of a robotic system developed by the authors, the effect of variation of system accuracy, precision, and tunnel diameter examined with respect to the potential treatable portion of the population. RESULTS: A facial recess diameter of 2.54 ±â€Š0.51 mm (n = 74) was determined from a review of existing literature; subsequent measurements on CT data revealed a facial recess diameter of 2.54 ±â€Š0.5 mm (n = 23). The developed model demonstrated the effects of varying accuracy on the treatable portion of the population. CONCLUSIONS: The presented model allows the assessment of the applicability of a system on a wider population scale beyond examining only the system's ability to reach an arbitrary threshold accuracy.

Assessment of Mastoid Function with Magnetic Resonance Imaging after Canal Wall Up Cholesteatoma Surgery.

OBJECTIVE: To use magnetic resonance imaging (MRI) to assess the extent of mastoid opacification after canal wall up (CWU) cholesteatoma surgery. MATERIALS AND METHODS: Thirty-five children in whom post-operative MRI had been obtained after CWU surgery. Cholesteatoma confined to the meso- and/or epi-tympanum was removed using a transcanal approach (n=18). More extensive disease required a combined approach tympanomastoidectomy (CAT, n=17). Mastoid opacification was assessed in both ears by a neuroradiologist blind to surgical details using an ordinal scale from 0 (no opacification) to 6 (completely opacified). The primary outcome measure was presence of normal mastoid ventilation, defined by evaluation of non-operative ears as a score ≤2. The presence of normal ventilation, as well as the raw opacification scores, were compared according to type of cholesteatoma surgery: 1) transcanal, with no mastoidectomy and 2) CAT. RESULTS: Mastoid ventilation was normal in 18 post-operative ears (51%). There was no significant difference in the proportion of normally ventilated mastoids in the CAT (n=17) and transcanal (n=18) groups (p=0.318; Fisher's exact). However, mastoid opacification scores were significantly higher in the CAT group than in the transcanal group (p=0.036; Mann-Whitney U). CONCLUSION: The mastoid frequently fails to become normally ventilated after cholesteatoma surgery. Subgroup analysis suggests cortical mastoidectomy does not increase the likelihood of normal mastoid ventilation after CWU cholesteatoma surgery. MRI provides a non-invasive tool to assess mastoid function, which contributes to the current debate on optimum surgical strategies for management of the mastoid in cholesteatoma surgery. Further research will determine whether this measure of mastoid health correlates with risk of recurrent cholesteatoma.

Assessment of mastoid air cell size versus sigmoid sinus variables with a tomography-assisted digital image processing program and morphometry.

We assessed the mastoid air cell size and variables of the sigmoid sinus in healthy ears and ears with chronic otitis media (COM). Thirty-eight patients with unilateral COM [15 with cholesteatoma (COM/+) and 23 without cholesteatoma (COM/-)], and 20 subjects with healthy ears, were included in the study. Assessment was performed using a quantitative digital image processing computed tomography (CT) program, and the volume of the mastoid bone was measured using the morphometric method of Cavalieri. In both COM/+ and COM/- patients the sigmoid to suprameatal spine distance and mastoid size were greater on the healthy side than on the diseased side ( p<0.05). The distance and area were significantly greater in the healthy control subjects than in either the healthy or the diseased ears of the patients with COM ( p<0.05). In the healthy ears of COM patients, there was significant correlation between the sigmoid to suprameatal spine distance and air cell size and mastoid volume ( p<0.05). In the diseased ears of COM patients, this correlation was absent ( p>0.05). The sigmoid sinus shape was of the half-moon type (62%), protrusive type (22%) and saucer type (16%). The digital image processing CT program allowed us to estimate the individual area of the air and soft tissue filled mastoid air cells. The mastoid size in both intact and disease ears of COM patients was smaller than in the healthy controls. The mastoid size may be determined genetically. However, environmental factors such as infection may also affect the mastoid size. Therefore, both genetic and environmental factors may be related to COM as far as the size of the mastoid air cells is concerned.

An assessment of the value of the preoperative computed tomography scans prior to otoendoscopic 'second look' in intact canal wall mastoid surgery.

'Second look' surgery following primary intact canal wall mastoid surgery for cholesteatoma is considered mandatory for most cases in modern otological practice. The morbidity of the second look can be reduced by the use of the rigid otoendoscope. Forty-three patients undergoing 'second look' surgery were studied with an average age of 24.7 years. Prior to surgery a computed tomography (CT) scan was performed to assess the anatomy and pneumatisation of the cavity. The mean interval between primary and secondary surgery was 16 months and in all cases CT scans were performed within 6 months of 'second look' surgery. The presence of an opaque mastoid did not correlate with residual or recurrent cholesteatoma. The sensitivity of CT in diagnosing residual or recurrent cholesteatoma was 42.9% with a specificity of 48.3% and a predictive value of 28.6%. These results are explained by the fact that it is radiologically impossible to differentiate between recurrence, scar tissue or fluid with a CT scan. Nevertheless it was possible to inspect the cavity with the otoendoscope even in the presence of an opaque mastoid whether due to scar tissue or residual/recurrent cholesteatoma.

Computerized assessment of the mastoid air cell system.

There have been many arguments on the development of pneumatization of temporal bone. However, a technique for direct volume measurement from high resolution computed tomography has never been reported. The aim of this paper is to develop a technique by using digital image processing to measure the volume of the mastoid air cell system. Forty three ears of 26 healthy subjects (13 males and 13 females) without a history of chronic or exudative otitis media, clear signs of Meniere's disease, severe sensorineural hearing impairment or malformation of temporal bone were eligible for enrolment in this study. Using a digital image processing technique, only the black air cells and tympanic cavity on the CT films are easily selected. Then, after image processing, only areas of these extracted black pneumatized parts are calculated. Consequently, the volume of pneumatized parts of temporal bone could be calculated separately as total volume and as partial volume that divided by several CT planes. The average volume of pneumatization in 43 temporal bones was 5.97 ml. However, since the volume of pneumatization in the temporal bone has traditionally been estimated by analyzing areas on X-ray films, the new method described in this study is significant for its ability to directly measure the volume of pneumatization in the temporal bone.

Preoperative assessment of the implantable middle ear pump system using CT scans and conventional X-rays of the temporal bone.

A completely implantable micropump system for drug delivery has recently been developed. After implantation in the temporal bone, this microdosage system enables application of drugs into the middle ear and round window area. Successful application of this new technology depends upon a suitable fit of the micropump within the patient's temporal bone. To obtain information about the fit before surgery, we analyzed 50 cadaver temporal bone specimens before total mastoidectomy, using conventional X-ray and spiral CT scans for water volume determination. Spiral CT is a feasible method for preoperative planning of the surgical implantation of the implantable middle ear micropump system (TI-DDS). The best parameter for a preoperative judgment is the volume of the mastoid cavity, as determined by CT. Implantation may be recommended when the mastoid volume, as measured by CT, is greater than 6.6 ml. To be certain that the implantable drug delivery system will be implantable, a cut-off value of 9.3 ml seems to be advisable. Spiral CT imaging is of great value as a tool for testing implantation preoperatively. The imaging is accomplished in approximately 30 seconds. Our preliminary results with cadaveric temporal bones are encouraging. Further studies are needed in order to transfer the results to a clinical implantation situation.

Suture closure in the human chondrocranium: CT assessment.

PURPOSE: To chronicle the development of ossification centers, sutures, and synchondroses in the chondrocranium throughout childhood by using computed tomography (CT). MATERIALS AND METHODS: One hundred eighty-nine children (age range, newborn to 18 years; median age, 4.0 years) without skull base deformity were referred for cranial CT. The closure of 18 sutures and synchondroses was graded. RESULTS: In the occipital bone at birth, six components were identified. The Kerckring ossicle rapidly fused to the supraoccipital bone within the 1st month. At age 1-3 years, the posterior and anterior intraoccipital synchondroses began to fuse. The occipitomastoidal, petro-occipital, and spheno-occipital synchondroses remained partially open into the teenage years. In the sphenoid bone at birth, 13 ossification centers were identified; most assimilated into the sphenoidal body during the first 2 years. Pneumatization of the sphenoid sinus appeared at age 1-2 years and advanced posteriorly over the next 3-5 years. CONCLUSION: The complex process of skull base development is chronicled, which provides CT standards for judgment of the patterns and timing of sutural or synchondrosal closure.

[Assessment of the volume of the mastoid air cell system using digital image processing].

There has been a great deal of controversy concerning the development of pneumatization in the temporal bone. Many reports on the size of the mastoid air cell system have been discussed a planimetric X-ray method, however, there have been no techniques for direct volume measurement based on high-resolution computed tomography (CT). Discussion of the relationship between ear disease and pneumatization of the temporal bone requires three-dimensional measurement of the temporal bone in vivo. Recently, we developed such a technique by using digital image processing to measure the volume of the mastoid air cell system. With this technique, only the air cells and tympanic cavity, with a grey scale level similar to air outside the skull were easily selected on the CT films. Then, after image processing called "thresholding", only the areas and volumes of these extracted pneumatized parts were calculated. The volumes of the pneumatized parts of the temporal bone were calculated separately as partial volumes divided by several CT planes. The sum of the partial volumes was calculated as the total volume of the aerated cavity. This technique also made it possible to reconstruct a three-dimensional (3D) model of the air cell system for visual presentation. CT images of 43 normal temporal bones were analyzed. The average volume temporal bone pneumatization (including air cells and tympanic cavity) was about 6ml. There were no differences between pneumatization on the two sides in either sex. Comparisons of partial volumes of pneumatization in the temporal bone revealed that the volumes of portions including the tympanic cavity and its surrounding air cells and those of the antrum and its surrounding air cells were larger than those of other portions. 3D models of the air cell system revealed a variety of shapes. These findings indicated that this technique is not only useful for quantitative analyses but for easy subjective morphological analyses.