Temporal Bone Computed Tomography Scans Research Articles

Three‐Dimensional Anatomic Analysis of Surgical Landmarks for Middle Fossa Approach

Objectives: The middle fossa approach needs the surgeon to have a 3-dimensional anatomic knowledge of internal auditory meatus (IAM), which is located underneath the middle fossa bony plate. Our purpose was to describe microsurgical anatomy of the middle fossa approach using temporal bone computed tomography (CT) 3-dimensional (3D) reconstruction. Methods: Thirty CT images of the temporal bone from patients aged between 20 and 60 years were selected. The inclusion criterion was a radiologically normal temporal bone CT scan. 3D-reconstructed images were obtained using high-resolution axial temporal bone CT scans. IAM, semicircular canal (SCC), cochlea, tympanic segment of the facial nerve (FN), geniculate ganglion (GG), and malleus were reconstructed. The length and angle among these structures was measured. Results: The mean lengths between the center of IAM and bony surface of middle cranial fossa at the Porus level was 7.7 mm (±1.0). The mean length between the superior of point of IAM of porus and GG was 15.4 mm (±1.5). The mean length between superior of point of IAM of porus and medial end of cochlear basal turn 9.9 mm (±0.9). Angle between the axis of SCC and the axis of tympanic segments of FN was 105.9° (±5.4). The mean angle between the axis of SCC and axis of IAM was 47.2° (±6.5) The mean angle between the axis of IAM and axis of tympanic segments of FN 59.6° (±10.9), The mean angle of 3-point malleus handle, GG, superior point of IAM of porus level was 113.8° (±9.8). Conclusions: The understanding of the 3D relationship in the microsurgical structure will help decide the drilling point for the IAM in case of lack of bony landmarks.

Middle Cranial Fossa Dehiscence as an Incidental Finding on CT

Objectives: Determine the prevalence of middle cranial fossa (MCF) dehiscence on computed tomography (CT) scans and establish its increase with age. Methods: All high-resolution temporal bone CT scans completed at a tertiary care center from 2011 to 2013, ordered by 1 otologist for any reason, were reviewed. Scans showing soft tissue, fluid, trauma, or previous operations were excluded. A total of 183 patients (296 ears) were reviewed blinded for age. The MCF floor was divided into 7 regions and systematically inspected. Ages of the patients were subsequently extracted from the medical record. Results: Logistic regression analysis confirmed increasing MCF dehiscence with age ( P < .05, odds ratio [OR] 1.07, R = 0.584). Overall ages (1-88 years; average 38.5 years), 32% of MCF floors were dehiscent at any one site. For age 60 years and over, 55% were dehiscent. For 226 paired ears, if one ear was dehiscent, there was a 66% chance the other ear was dehiscent as well. Superior canal dehiscence (SCD) was seen in 7% of all patients, and only in combination with MCF dehiscence. SCD occurred in 16% of dehiscent ears. The most common sites were directly above the malleus head and above the additus ad antrum (36% and 28%, respectively). Conclusions: The incidence of MCF dehiscence increases with age. Over all ages, approximately 32% of ears show dehiscence. Over 60 years, approximately 55% show dehiscence. The increase of dehiscence with age is statistically significant. The most common sites along the MCF floor are in the epitympanum over the malleus head and additus ad antrum.

Novel Radiographic Measurement Algorithm Demonstrating a Link between Obesity and Lateral Skull Base Attenuation

Objectives: (1) Describe a validated measurement instrument to quantify tegmen thickness on computed tomography (CT) images. (2) Compare tegmen thickness in 3 groups: patients with spontaneous cerebrospinal fluid (CSF) leaks, obese controls, and nonobese controls. Methods: Retrospective review from 2005 to present. Patients with a diagnosis of spontaneous CSF otorrhea and dedicated temporal bone CT scans were included. Matched obese (body mass index [BMI] >30) and nonobese (BMI <30) controls were selected from a pool of cochlear implant candidates. The tegmen was measured radiographically in all patients at pre-defined points. Independent, blinded measurements were made by 3 of the authors and compared for interrater validity. Results: Ninety-nine patients were measured: 39 in the CSF group (BMI 35.9), 29 in the obese group (BMI 34.6), and 31 in the nonobese group (BMI 24.2). The CSF group had a significantly thinner aggregate tegmen thickness (0.82 mm ± 0.19) compared with both obese controls (0.99 mm ± 0.18, P = .007) and nonobese controls (1.26 mm ± 0.2, P < .001). Obese controls were thinner than non obese controls ( P < .001). Signs/symptoms of benign intracranial hypertension (BIH) were most commonly found in the CSF group. No other factors significantly affected thickness. Good to excellent correlation of measurements was found between all 3 raters. Conclusions: This is the first study to (1) quantify lateral skull base thickness and (2) significantly correlate obesity with lateral skull base attenuation. Obese spontaneous CSF leak patients may have even greater attenuation of their skull base than matched obese controls. This finding may further support theories that an additional process, such as BIH, may play an important pathophysiologic role in skull base thinning.

Prevalence and range of GJB2 and SLC26A4 mutations in patients with autosomal recessive non‑syndromic hearing loss.

The frequency and distribution of genetic mutations that cause deafness differ significantly according to ethnic group and region. Zhejiang is a province in the southeast of China, with an exceptional racial composition of the population caused by mass migration in ancient China. The purpose of the present study was to investigate the prevalence and spectrum of gap junction‑β2 (GJB2), solute carrier family26 (anion exchanger) member4 (SLC26A4) and GJB3 mutations in patients with autosomal recessive non‑syndromic hearing loss (ARNHL) in this area. A total of 176unrelated pediatric patients with ARNHL were enrolled in the study. A genomic DNA sample was extracted from the peripheral blood. Polymerase chain reaction was employed, and the products were sequenced to screen for mutations in GJB2. In addition, a SNaPshot sequencing method was utilized to detect four hotspot mutations in SLC26A4 (IVS7‑2A>G and c.2168A>G) and GJB3 (c.538C>T and c.547G>A). All patients were subjected to a temporal bone computed tomography scan to identify enlarged vestibular aqueducts (EVA). In total, 14different mutations, including two new mutations (p.W44L and p.D66N) of GJB2, were detected. The most common pathogenic mutation of GJB2 was c.235delC (15.1%), followed by c.176_191del16 (1.7%), c.299_300delAT (1.7%), c.508_511dup (0.85%) and c.35delG (0.28%) of the total alleles. Mutation analysis of SLC26A4 demonstrated that 13.6% (24/176) of patients carried at least one mutant allele. The patients with EVA (84.2%) had SLC26A4 mutations, and 31% had homozygous mutations. Only one patient carried a heterozygous mutation of GJB3 (c.538C>T). Compared with the other regions of China, in the present population cohort, the prevalence and spectrum of mutations in GJB2 was unique, and in patients with EVA the frequency of a homozygous mutation in SLC26A4 was significantly lower. These findings may be of benefit in genetic counseling and risk assessment for families from this area of China.

Three-dimensional Anatomical Analysis of Surgical Landmarks for the Middle Cranial Fossa Approach.

This study describes the microsurgical anatomy of the middle cranial fossa approach using temporal bone three-dimensional (3D) computed tomography (CT) reconstruction, which should contribute to determining the drilling point for the internal auditory meatus (IAM) when bony landmarks are absent. Thirty temporal bone CT scans were reviewed retrospectively. We measured the shortest and longest distances to IAM from the petrous ridge, and measured the angle between the facial nerve and various labyrinth structures. Three-dimensional reconstructed images were obtained using high-resolution axial temporal bone CT (0.7-mm-thick slices, FOV 90×90, KVp 120, 305mA, width 2,800, and level 800). The mean shortest and longest distances to IAM from the petrous ridge were 5.22 and 10.1mm, respectively. The mean distance to the IAM from the cochlea was 9.91mm. The mean angle between the IAM and superior semicircular canal was 47.21°, which was more acute than previously reported. The mean angle between the IAM and geniculate ganglion (GG) and external auditory canal was 113.8°, and the mean distance from the GG to the IAM was 15.44mm. Understanding the 3D relationships among the microsurgical structures will help to decide the drilling point for the IAM when bony landmarks are absent. A preoperative evaluation might be useful for preserving important neurovascular structures while approaching the middle fossa.

Familial Superior Canal Dehiscence Syndrome

The etiology of superior canal dehiscence (SCD) involving the arcuate eminence is not completely understood, but genetic factors may play a role. One hypothesis is that patients are born with a defect of the superior canal, and an acute event (such as head trauma) or progressive loss of bone (eg, due to dural pulsations) may result in the onset of SCD symptoms. Familial SCD has only been briefly mentioned in the literature to date. We report 3 families that each had 2 members with SCD syndrome. We found that first-degree relatives presented with similar complaints and that temporal bone computed tomography scans between relatives showed very similar skull base topography and anatomic SCD defects. The presence of symptomatic SCD among first-degree relatives and similar skull base topography suggests that genetics may play a role in the etiology of SCD.

Volumetry and analysis of anatomical variants of the anterior portion of the petrous apex outlined by the kawase triangle using computed tomography.

Background Anterior petrosectomy has become an increasingly used approach for petroclival lesions. This study measures the volume and the anatomical variants of the anterior portion of the petrous apex outlined by the Kawase triangle using computed tomography (CT). Methods This was a transversal retrospective study. We assessed the anterior petrous apex portion outlined by the Kawase triangle in consecutive patients > 18 years of age from CT scans of temporal bone stored in an archive system. The volumetry was performed on a workstation. Results A total of 154 petrosal apex were analyzed in 77 patients (36 men). The average volume of the region outlined by the Kawase triangle was 1.89 ± 0.52 cm(3). The volume average in men was 2.01 ± 0.58 cm(3), and the average in women was 1.79 ± 0.41 cm(3). Intra- and interobserver agreement were both excellent, and there was little variance. Nineteen petrous apex demonstrated anatomical variations. In 18 cases it was pneumatized, and in one case a vascular or nerve-like structure was identified, a report we did not find in the literature. Conclusion The volumetry of the petrous apex anterior portion outlined by the Kawase triangle can be made by CT with excellent intra- and interobserver agreement and reproducibility. There are anatomical variants in this region that are relevant to surgery.

A two-cycle prospective audit of temporal bone computed tomography scan requests: improving the clinical applicability of radiology reports

Radiologists require accurate clinical information to formulate reports. This is particularly relevant to computed tomography of the temporal bone, in which previous surgery can mimic disease. The information provided with temporal bone computed tomography scan requests was evaluated. The study aimed to minimise inappropriate requests and improve the clinical value of reports. A two-cycle prospective audit was undertaken using a proforma designed on the basis of national guidelines. Following the first cycle (in which the requests and reports of 100 scans were evaluated), new guidelines and training were implemented. A follow-up audit (of 50 scans) was then performed. Following intervention, the percentage of clinically relevant reports increased from 52 to 94 (p < 0.01), whilst unnecessary or inappropriate scan requests decreased from 11 to 2 per cent (p < 0.05). Optimising the clinical value of temporal bone computed tomography scan requests will have positive implications for patient care, time management and cost. The quality of the clinical information provided can have a significant impact on the clinical value of radiology reports, and can mean that unnecessary irradiation is avoided.

Down syndrome: An electrophysiological and radiological profile

To assess the hearing status of trisomy 21 patients by analyzing electrophysiological and radiological findings of any correlation between hearing impairment and major or minor inner ear malformations. Prospective radiological and electrophysiological study. A group of 34 ears of Down syndrome subjects and 20 ears of a volunteer age- and sex-matched control group of 10 normal subjects were studied electrophysiologically by means of otoacoustic emissions and auditory brainstem response. Temporal bone computed tomography (CT) scans were carried out in both groups; radiological findings were compared. Inner ear structure measurements were applied attempting to disclose subtle bony labyrinthine anomalies. The findings from both groups were statistically analyzed employing the t test. The rate of sensorineural hearing loss (SNHL) in Down syndrome group was 41%. Temporal bone CT scans showed no ossicular malformation in all Down syndrome cases. Major inner ear abnormalities were disclosed in 5.8%; they corresponded to two cases of lateral semicircular canal dysplasia detected on CT images by visual inspection. The application of various inner ear structure measurements increased the overall detection rate of common inner ear malformations to 47%. A statistically significant correlation was found between hearing level and vestibule length (P = .009) and internal auditory canal length (P = .028). Vestibular aqueduct width was correlated to different otic abnormalities. SNHL is mainly secondary to the underestimated subtle inner ear malformations that are adequately demonstrated by adopting standardized inner ear structure measurements on petrous bone imaging. Vestibular height and internal auditory canal length were correlated to SNHL. 3b.

Genetic mutations in nonsyndromic deafness patients of Chinese minority and han ethnicities in Yunnan, China

BackgroundEach year in China, 30,000 babies are born with congenital hearing impairment. However, the molecular etiology of hearing impairment in the Yunnan Province population where more than 52 minorities live has not been thoroughly investigated. To provide appropriate genetic testing and counseling to these families, we investigated the molecular etiology of nonsyndromic deafness in this population.MethodsUnrelated students with hearing loss (n = 235) who attended Kunming Huaxia secondary specialized school in Yunnan enrolled in this study. Three prominent deafness-related genes, GJB2, SLC26A4 and mtDNA 12S rRNA, were analyzed. High-resolution temporal bone computed tomography (CT) scan examinations were performed in 100 cases, including 16 cases with SLC26A4 gene variants, and 37 minorities and 47 Han cases without any SLC26A4 gene mutation.ResultsThe GJB2 mutation was detected in 16.67% (7/42) of minority patients and 17.62% (34/193) of Chinese Han patients (P > 0.05). 235delC was the hotspot mutation in nonsyndromic hearing loss (NSHL) patients, whereas 35delG was not found. The 431_450del19 mutation was detected for the first time in Han NSHL patients, which resulted in a premature stop codon and changed the protein. The SLC26A4 mutation was found in 9.52% (4/42) of minority patients and 9.84% (19/193) of Han Chinese patients (P > 0.05). The frequencies of mtDNA 12S rRNA mutation in minority and Han Chinese patients were 11.90% (5/42) and 7.77% (15/193; P > 0.05), respectively. Sixteen (16/23, 69.57%) patients with SLC26A4 mutations received temporal bone CT scan, and 14 patients were diagnosed with enlarged vestibular aqueducts (EVAs); the other 2 patients had normal inner ear development. The ratio of EVA in the minorities was 14.63% (6/41).ConclusionsIn this study, a total of 35.74% deaf patients showed evidence of genetic involvement, based on either genetic screening or family history; 17.45%, 9.79%, and 8.51% of the patients were determined to have inherited hearing impairment caused by GJB2, SLC26A4, and mtDNA 1555A > G mutations. There was no significant difference in deafness associated gene mutational spectrum and frequency between the Yunnan minority and Han patients.

Computed tomography demonstrates abnormalities of contralateral ear in subjects with unilateral sensorineural hearing loss

PurposePrior studies have associated gross inner ear abnormalities with pediatric sensorineural hearing loss (SNHL) using computed tomography (CT). No studies to date have specifically investigated morphologic inner ear abnormalities involving the contralateral unaffected ear in patients with unilateral SNHL. The purpose of this study is to evaluate contralateral inner ear structures of subjects with unilateral SNHL but no grossly abnormal findings on CT. Materials and methodsIRB-approved retrospective analysis of pediatric temporal bone CT scans. 97 temporal bone CT scans, previously interpreted as “normal” based upon previously accepted guidelines by board certified neuroradiologists, were assessed using 12 measurements of the semicircular canals, cochlea and vestibule. The control-group consisted of 72 “normal” temporal bone CTs with underlying SNHL in the subject excluded. The study-group consisted of 25 normal-hearing contralateral temporal bones in subjects with unilateral SNHL. Multivariate analysis of covariance (MANCOVA) was then conducted to evaluate for differences between the study and control group. ResultsCochlea basal turn lumen width was significantly greater in magnitude and central lucency of the lateral semicircular canal bony island was significantly lower in density for audiometrically normal ears of subjects with unilateral SNHL compared to controls. ConclusionAbnormalities of the inner ear were present in the contralateral audiometrically normal ears of subjects with unilateral SNHL. These data suggest that patients with unilateral SNHL may have a more pervasive disease process that results in abnormalities of both ears. The findings of a cochlea basal turn lumen width disparity >5% from “normal” and/or a lateral semicircular canal bony island central lucency disparity of >5% from “normal” may indicate inherent risk to the contralateral unaffected ear in pediatric patients with unilateral sensorineural hearing loss.

High and dehiscent jugular bulb: clear and present danger during middle ear surgery

Internal jugular vein is anatomic continuation of cranial dural sinuses in the neck region. During the course of skull base the first enlarged segment of jugular vein is described as jugular bulb. The aim of this study is to evaluate the jugular bulb abnormalities and define the risk of high and dehiscent jugular bulb injury during middle ear surgery. This is a retrospective radiologic study of 1,010 patients (2,020 temporal bones) with various ear symptoms who had high resolution temporal bone computed tomography scans between 2007 and 2011. High jugular bulb was seen in 308 (15.2 %) temporal bones. Jugular bulb dehiscence was encountered in 153 (7.5 %) temporal bones. High jugular bulb and jugular bulb dehiscence were more common in the right ears and females. Forty-one (2 %) temporal bones revealed high and dehiscent jugular bulb which can be vulnerable during middle ear surgery. High and dehiscent jugular bulb was more common in the right ears and males. Male predominance becomes more significant in the left ears. Of the 308 temporal bones with high jugular bulb, 87 (28.2 %) also had coexisting carotid canal dehiscence. High and dehiscent jugular bulb is an important anatomic variation that can result in catastrophic outcomes during middle ear surgery. Our series show that 2 % of patients can be considered in the "high-risk" group. Precise assessment of the preoperative computed tomography scans by both the radiologist and the ENT surgeon is of utmost importance. Preoperative awareness will minimize morbidity and mortality.

Prevalence of radiologic superior canal dehiscence in normal ears and ears with chronic otitis media

Although labyrinth fistulae are caused mostly by cholesteatoma, they can occur in long-standing chronic otitis media (COM) without cholesteatoma. We aimed to compare the prevalence of radiologic SCD on computed tomography (CT) between normal ears and contralateral COM ears in patients with unilateral COM and to assess the prevalence of superior canal dehiscence (SCD) according to the age. Case series with comparison performed at a tertiary care academic referral center. We retrospectively reviewed consecutive temporal bone CT scans of 759 patients with unilateral COM between 2009 and 2011. The mean (± standard deviation) age was 48 years (±14 years). Images were independently evaluated by two otologists, and the bone overlying the superior canal was characterized as normal, suspicious, or definite SCD. The prevalence (3.4%) of definite SCD in COM ears was significantly higher than that (0.3%) in normal ears. The prevalence (6.6%) of suspicious or definite SCD in COM ears was also higher than that (1.2%) in normal ears. There was no correlation between the prevalence of SCD and age in either normal or COM ears. All of the normal ears with suspicious or definite SCD also showed contralateral suspicious or definite SCD (bilateral involvement). Our present findings suggest that the COM is related to the presence of SCD. The roof of the temporal bone may become thin by the failure of postnatal bone development and susceptible to chronic brain pulsation and pressure exerted by the temporal lobe in COM ears.

Congenital Cytomegalovirus Is the Second Most Frequent Cause of Bilateral Hearing Loss in Young French Children

In children with congenital cytomegalovirus (cCMV), greater than 50% of symptomatic newborns and 8.5% to 18% of asymptomatic newborns will have hearing loss, either present at birth or delayed in onset. This prospective study was undertaken to evaluate the extent of cCMV among causes of hearing loss in French children younger than 3 years and to assess their characteristics in relation to cCMV status. Children younger than 3 years with hearing loss were prospectively enrolled. Cytomegalovirus polymerase chain reaction (PCR) assays were performed on dried blood spots from these children’s Guthrie cards and considered positive when CMV presence was confirmed. Brain computed tomography (CT) or magnetic resonance imaging and temporal bone CT scans were obtained. Normal hearing, mild loss, moderate loss, severe loss, and profound loss were defined when the child was able to hear a stimulus of 0 to 20, 21 to 40, 41 to 70, 71 to 90, and 91 dB or greater, respectively. Results of genetic analysis of the connexin 26 (GJB2) and connexin 30 (GJB2) genes were recorded. The prevalence of cCMV infection was estimated together with its 95% confidence interval. Of 114 eligible children, 100 with bilateral hearing loss were enrolled at a median age of 15 months and included in the analysis. Hearing loss in the best ear was not recorded for 2 children and was mild in 1 child, moderate in 22 children, severe in 16, and profound in 59. Results of brain and temporal bone imaging were available for 77 children and genetic analysis of the GJB2 and GJB2 genes for 55 children. Cytomegalovirus PCR was positive in 8 children, and cCMV infection prevalence was 8.0% (95% confidence interval, 2.7%–13.3%). Prevalence of cCMV was 13.7% (n = 8) in the 59 children with profound bilateral hearing loss, a significant association (P = 0.02). Children with cCMV were significantly more likely to have delayed development (P = 0.027) and abnormalities on the brain CT scan (P = 0.0005). Two of the 8 children with cCMV had at least 1 other risk factor for hearing loss, including neonatal intensive care unit stays or familial history of hearing loss. None of the 8 children with cCMV were born prematurely, but 4 had a small birth weight for their gestational age, and 1 child had microcephaly. In 2 children, the diagnosis of cCMV infection had been made before inclusion in the study. For the other 6 children, the diagnosis of cCMV was made retrospectively because of the positive CMV PCR result. In 61 patients (71.8%), the origin of hearing loss was genetic. Mutations of GJB2 and/or GJB2 genes were found in 22 patients (25.9%). In 1 patient (1.2%), hearing loss was due to a mutation in the otoferlin gene. In 13 patients (15.3%), a syndromic origin included Waardenburg syndrome, Usher syndrome, Angelman disease, mucopolysaccharidosis, and another metabolic disease. In 8 patients (9.4%), a malformation was found in the temporal bone on CT scan that was considered genetic. A genetic origin also was highly probable in 10 with a history of 1 family member with hearing loss before age 40 years and consanguineous parents in 7. Prematurity was the cause of hearing loss in 6 children (7.1%). Congenital CMV was present in 8 (9.4%) of the 85 patients with a complete workup and was the second most common individual cause of bilateral hearing loss after connexin mutations. The prevalence of cCMV indicates only the proportion of cCMV among French children with bilateral hearing loss and not the prevalence of cCMV in the total population of children with hearing loss. Because universal neonatal hearing screening is underway in France, it may be possible to diagnose cCMV in infants with confirmed hearing loss and to implement early intervention with antiviral treatment.

Does microtia predict severity of temporal bone CT abnormalities in children with persistent conductive hearing loss?

This study aimed to determine the spectrum of temporal bone computed tomography (CT) abnormalities in children with conductive hearing loss (CHL) with and without microtia. From 1993 to 2008, a total of 3396 pediatric records including CHL were reviewed at our institution and revealed 180 cases of persistent CHL, 46 of whom had diagnostic temporal bone CT examinations. All of these examinations were systematically reviewed by two pediatric neuroradiologists, working in consensus, who had 5 and 18 years, respectively, of dedicated pediatric neuroradiology experience. Of the 46 children, 16 were boys and 30 were girls (age: 0.2-16 years; mean: 5 years). Also, 21 (46%) children had microtia and 25 (54%) children did not, as determined by clinical evaluation. External auditory canal atresia/stenosis (EAC-A/S) was the most common anomaly in both microtia and non-microtia groups. Two or more anomalies were observed in 18/21 children with microtia. The frequency of EAC-A/S was greater in children with microtia versus those without it (86% versus 32%, respectively; P = 0.0003). Syndromic diagnoses were also significantly more frequently made in children with microtia versus those without microtia (76% versus 20%, respectively; P = 0.0001). Temporal bone CT scans were normal in 10 children (22%) with persistent CHL. Microtia is an important finding in children with CHL. EAC and middle ear/ossicle anomalies were significantly more frequently seen in children with microtia, and multiple anomalies and bilateral microtia were more common in children with syndromic associations. These findings highlight the importance of understanding the embryological development of the temporal bone. The presence of one anomaly should raise suspicion of the possibility of other anomalies, especially in the setting of microtia. Bilateral microtia and multiple anomalies should also raise suspicion of genetic syndromes.

First stage in predicative measure for transnasal transsphenoidal approach to petrous apex cholesterol granuloma

This study evaluates the feasibility of the transsphenoidal approach to petrous apex cholesterol granuloma based on the petrous angle. This is the angle centered at the vomer, extending between the medial aspect of the C3 segment of the internal carotid artery and the occipital protuberance. The aim of this study is to determine the average petrous angle in a population of normal computed tomography scans. Retrospective review at the University of Cincinnati Medical Center. Two of the authors independently reviewed 400 consecutive normal temporal bone computed tomography scans obtained between September and December of 2009. All scans had slice thickness of 1.25 mm at 0.6-mm intervals. Axial images parallel to the orbitomeatal plane were analyzed, and the petrous angle was measured bilaterally. Interrater reliability was tested on 50 of the computed tomography scans. A total of 400 temporal bones were reviewed. The mean and median petrous angle was 17.7 and 16.5 degrees, respectively. Eleven (2.8%) had an angle ≤ 10.0, 331 (82.8%) between 10.1 to 20.0, and 58 (14.5%) ≥ 20.1. The interrater variability was highly correlated (r = 0.912, P < .005). Normative data on consistent petrous apex radiographic landmarks are important for assessing the feasibility of the transphenoidal approach to the petrous apex for cholesterol granuloma drainage. Based on a large population of normal computed tomography scans, the majority of temporal bones (82.8%) have a petrous angle ranging between 10.0 and 20.0 degrees.

Surgical and radiologic anatomy of a cochleostomy produced via posterior tympanotomy for cochlear implantation based on three-dimensional reconstructed temporal bone CT images

In this study, we evaluated the surgical and radiologic anatomy of a cochleostomy produced via posterior tympanotomy for cochlear implantation (CI). Twenty computed tomography (CT) images of the temporal bone from patients aged between 20 and 60years were selected. The inclusion criterion was a radiologically normal temporal bone CT scan. Three-dimensional (3D) reconstructed images were obtained using high-resolution axial temporal bone CT scans. Eight points were used to evaluate the surgical anatomy of the posterior tympanotomy and cochleostomy. The length of lines between the points and the angles between the lines were measured. The mean length of line AB (superior-inferior length of the posterior tympanotomy for CI) was 6.48±0.26mm, while line AC (width of the chorda tympani and facial nerves) was 3.60±0.2mm. The mean angle of ABC (angle at which the chorda tympani nerve branched from the facial nerve) was 18.40°±1.05°. The mean length of line AD (distance from the facial ridge to the point of cochleostomy) was 9.58±0.47mm. 3D imaging of the facial recess and round window can be used to identify the facial recess before surgery. This may help to avoid injury to the chorda tympani nerve during posterior tympanotomy, and make it easier to insert the electrode array during CI by creating a large enough posterior tympanotomy to avoid injury to the facial nerve, which can cause immediate or delayed facial palsy.

Molecular Epidemiology and Functional Assessment of Novel Allelic Variants of SLC26A4 in Non-Syndromic Hearing Loss Patients with Enlarged Vestibular Aqueduct in China

BackgroundMutations in SLC26A4, which encodes pendrin, are a common cause of deafness. SLC26A4 mutations are responsible for Pendred syndrome and non-syndromic enlarged vestibular aqueduct (EVA). The mutation spectrum of SLC26A4 varies widely among ethnic groups. To investigate the incidence of EVA in Chinese population and to provide appropriate genetic testing and counseling to patients with SLC26A4 variants, we conducted a large-scale molecular epidemiological survey of SLC26A4.MethodsA total of 2352 unrelated non-syndromic hearing loss patients from 27 different regions of China were included. Hot spot regions of SLC26A4, exons 8, 10 and 19 were sequenced. For patients with one allelic variant in the hot spot regions, the other exons were sequenced one by one until two mutant alleles had been identified. Patients with SLC26A4 variants were then examined by temporal bone computed tomography scan for radiological diagnosis of EVA. Ten SLC26A4 variants were cloned for functional study. Confocal microscopy and radioisotope techniques were used to examine the membrane expression of pendrin and transporter function.ResultsOf the 86 types of variants found, 47 have never been reported. The ratio of EVA in the Chinese deaf population was at least 11%, and that in patients of Han ethnicity reached at least 13%. The mutational spectrum and mutation detection rate of SLC26A4 are distinct among both ethnicities and regions of Mainland China. Most of the variants caused retention of pendrin in the intracellular region. All the mutant pendrins showed significantly reduced transport capability.ConclusionAn overall description of the molecular epidemiological findings of SLC26A4 in China is provided. The functional assessment procedure can be applied to identification of pathogenicity of variants. These findings are valuable for genetic diagnosis, genetic counseling, prenatal testing and pre-implantation diagnosis in EVA families.

Microsurgical Localization of the Cochlea in the Extended Middle Fossa Approach

Objective In the extended middle fossa approach, a portion of the petrous bone known as Kawase's rhomboid can be drilled to expose the posterior fossa through a middle fossa corridor. During this bony resection, the cochlea is placed at risk. The objective of this study was to objectively detail the position of the cochlea in relation to reliable surgical landmarks. Methods Eleven cadaveric specimens were dissected-including six cadaveric heads and five dry temporal bones by means of an anterior petrosectomy with skeletonization of the cochlea. Three anatomic measurements describing the location of the cochlea in relation to the extrapolated intersection of the greater superficial petrosal nerve (GSPN) and facial nerve were recorded. These measurements were then correlated with thin-cut temporal bone computed tomography scans from 25 patients with morphologically normal inner ears. Results In the cadaveric specimens, the anterior border of the membranous basal turn of the cochlea was located an average of 7.56 mm (6.4 to 8.9 mm) anterior to the extrapolated junction of the GSPN and facial nerve, as measured along the course of the GSPN. The medial border of the membranous cochlea (medial margin of basal turn) was located an average of 8.2 mm (6.9 to 8.9 mm) medial to the extrapolated junction of the GSPN and facial nerve, as measured along the course of the facial nerve. The average maximum distance from the extrapolated junction of the GSPN and facial nerve to the membranous cochlea was 9.3 mm (8.2 to 10.3 mm). These anatomic measurements correlated well with radiologic measurements of the same parameters. Conclusion When drilling Kawase's rhomboid, it is useful to locate the extrapolated junction of the GSPN and the facial nerve. Drilling of the anteromedial petrous bone outside of a radius of 12.5 mm from the extrapolated junction of GSPN and facial nerve appears to be associated with a low degree of risk to the cochlear apparatus.

Cochlear implantation in children with cochlear nerve deficiency: A report of nine cases

ObjectiveCochlear implantation for children with cochlear nerve deficiency remains controversial, as the presence of the cochlear nerve has been central to the success of cochlear implantation. This study sought to investigate whether there is any benefit from cochlear implantation for children with cochlear nerve deficiency. MethodsNine children with cochlear nerve deficiency and bilateral prelingual profound sensorineural hearing loss were included in this study. Inner ear and internal auditory canal structures were evaluated using magnetic resonance imaging and temporal bone computed tomography scans. Meaningful auditory integration scales, categories of auditory performance scores, speech intelligibility ratings and pure tone average threshold with cochlear implantation were measured for evaluation of hearing and speech performance. ResultsOnly four (44.4%) children had a significant improvement in pure tone average threshold with the cochlear implant device (77.5dBHL, 45dBHL, 51.3dBHL and 68.8dBHL). No child achieved sufficient speech intelligibility or perception ability during a follow-up of at least one year after surgery. ConclusionsThe decision to perform cochlear implantation in children with cochlear nerve deficiency must be undertaken with caution as it has limited effectiveness and uncertain cost-benefit.