Imaging Review of the Temporal Bone: Part II. Traumatic, Postoperative, and Noninflammatory Nonneoplastic Conditions

Multiphysics Interaction Analysis of the Therapeutic Effects of the Sigmoid Sinus Wall Reconstruction in Patients with Venous Pulsatile Tinnitus

Sigmoid sinus wall dehiscence (SSWD) is an important etiology of venous pulsatile tinnitus (VPT) and is treated by sigmoid sinus wall reconstruction (SSWR). This study aimed to investigate the therapeutic effects of the different degrees of SSWR and the prognostic effect in patients with VPT. Personalized models of three patients with SSWD (control), 3/4SSWD, 1/2SSWD, 1/4SSWD, and 0SSWD were reconstructed. A multiphysics interaction approach was applied to elucidate the biomechanical and acoustic changes. Results revealed that after SSWR, the average pressure of venous vessel on the SSWD region reduced by 33.70 ± 12.53%, 35.86 ± 12.39%, and 39.70 ± 12.45% (mean ± SD) in three patients with 3/4SSWD, 1/2SSWD, and 1/4SSWD. The maximum displacement of the SSWR region reduced by 25.91 ± 30.20%, 37.20 ± 31.47%, 52.60 ± 34.66%, and 79.35 ± 18.13% (mean ± SD) in three patients with 3/4SSWD, 1/2SSWD, 1/4SSWD, and 0SSWD, with a magnitude approximately 10^-3 times that of the venous vessel in the SSWD region. The sound pressure level at the tympanum reduced by 23.72 ± 1.91%, 31.03 ± 14.40%, 45.62 ± 19.11%, and 128.46 ± 15.46% (mean ± SD). The SSWR region was still loaded with high stress in comparison to the surrounding region. The SSWR region of the temporal bone effectively shielded the high wall pressure and blocked the transmission of venous vessel vibration to the inner ear. Patients with inadequate SSWR still had residual VPT symptoms despite the remission of VPT symptoms. Complete SSWR could completely solve VPT issues. High-stress distribution of the SSWR region may be the cause of the recurrence of VPT symptoms.

Application value of a deep learning method based on a 3D V-Net convolutional neural network in the recognition and segmentation of the auditory ossicles

Objective

To explore the feasibility of a deep learning three-dimensional (3D) V-Net convolutional neural network to construct high-resolution computed tomography (HRCT)-based auditory ossicle structure recognition and segmentation models.

Methods

The temporal bone HRCT images of 158 patients were collected retrospectively, and the malleus, incus, and stapes were manually segmented. The 3D V-Net and U-Net convolutional neural networks were selected as the deep learning methods for segmenting the auditory ossicles. The temporal bone images were randomized into a training set (126 cases), a test set (16 cases), and a validation set (16 cases). Taking the results of manual segmentation as a control, the segmentation results of each model were compared.

Results

The Dice similarity coefficients (DSCs) of the malleus, incus, and stapes, which were automatically segmented with a 3D V-Net convolutional neural network and manually segmented from the HRCT images, were 0.920 ± 0.014, 0.925 ± 0.014, and 0.835 ± 0.035, respectively. The average surface distance (ASD) was 0.257 ± 0.054, 0.236 ± 0.047, and 0.258 ± 0.077, respectively. The Hausdorff distance (HD) 95 was 1.016 ± 0.080, 1.000 ± 0.000, and 1.027 ± 0.102, respectively. The DSCs of the malleus, incus, and stapes, which were automatically segmented using the 3D U-Net convolutional neural network and manually segmented from the HRCT images, were 0.876 ± 0.025, 0.889 ± 0.023, and 0.758 ± 0.044, respectively. The ASD was 0.439 ± 0.208, 0.361 ± 0.077, and 0.433 ± 0.108, respectively. The HD 95 was 1.361 ± 0.872, 1.174 ± 0.350, and 1.455 ± 0.618, respectively. As these results demonstrated, there was a statistically significant difference between the two groups (P < 0.001).

Conclusion

The 3D V-Net convolutional neural network yielded automatic recognition and segmentation of the auditory ossicles and produced similar accuracy to manual segmentation results.

Computed Tomography Density as a Bio-marker for Histologic Grade of Otosclerosis: A Human Temporal Bone Pathology Study

HYPOTHESIS

Computed tomography (CT) density measurement can be used to objectively distinguish otosclerosis from normal bone and to determine histologic grades of otosclerosis.

BACKGROUND

Otosclerosis can be seen on CT as subtle radiolucent areas. An objective radiologic measurement that corresponds to known otosclerosis pathology may improve diagnostic accuracy, and could be used as a radiologic biomarker for otosclerosis grade.

METHODS

A blinded, randomized evaluation of both histologic grade on histopathology slides and CT density measurement was performed on 78 human temporal bone specimens (31 with otosclerosis and 47 controls) that had undergone high-resolution multi-detector CT before histologic processing. Assessments were performed at 11 regions of interest (ROIs) in the otic capsule for each specimen.

RESULTS

The CT density measurement mean (Hounsfield Units) ± standard deviation for all ROIs (Nos. 1-9) was 2245 ± 854 for grade 0 (no otosclerosis, n = 711), 1896 ± 317 for grade 1 (inactive otosclerosis, n = 109), and 1632 ± 255 for grades 2 and 3 combined (mixed/active otosclerosis, n 35). There was a strong inverse correlation of CT density to histologic grade at ROIs Nos. 1-5 (ANOVA, p < 0.0001). The inter-rater reliability for CT density was very good (correlation coefficient 0.87, p < 0.05). ROC curves suggested a cut-off of 2,150HU to distinguish otosclerosis from normal bone, and 1,811HU to distinguish low grade from mixed/high grade otosclerosis.

CONCLUSIONS

In human temporal bone specimens, CT density may be used to distinguish normal bone from bone involved by otosclerosis. A higher histologic grade (i.e., indicating a more active otosclerotic focus) correlated with lower density.

Imaging of the Postoperative Temporal Bone

Evaluation of the postoperative temporal bone can be difficult given the complex anatomy of this region and the myriad surgical approaches for management of a variety of conditions. This article provides an understanding of common postsurgical changes of the temporal bone and their typical imaging appearances. Ultimately, greater radiologist knowledge of postoperative temporal bone imaging findings will help to serve patients and referring clinicians with prompt diagnosis and recognition of expected postintervention changes compared with postoperative complications and/or disease recurrence.

Diagnostic Performance of Conebeam CT Pixel Values in Active Fenestral Otosclerosis

BACKGROUND AND PURPOSE

Quantitative bone densitometry on multidetector CT of the temporal bone is a diagnostic adjunct for otosclerosis in its active (spongiotic) phase, but translating this technique to conebeam CT is limited by the technical variability of conebeam CT pixel values. The purpose of this study was to evaluate the performance of internally calibrated conebeam CT pixel value measurements that can enable the determination of active fenestral otosclerosis (otospongiosis).

MATERIALS AND METHODS

This study included 37 ears in 22 patients with a clinical diagnosis of otospongiosis in those ears and 35 ears in 22 control patients without the diagnosis. Temporal bone conebeam CT was performed. ROIs were set anterior to the oval window, in the lateral semicircular canal bone island, and in a nearby aerated space. Mean conebeam CT pixel values in these regions determined the relative attenuation ratio of the area anterior to the oval window normalized to normal otic capsule bone and air.

RESULTS

The relative attenuation ratio for cases of otospongiosis was significantly lower than that for controls (P < .001). Based on receiver operating characteristic analysis, the optimal cutoff relative attenuation ratio was 0.876, which had an accuracy of 97.2% for the diagnosis of otospongiosis.

CONCLUSIONS

Internally calibrated pixel value ratios in temporal bone conebeam CT can feasibly help diagnose active/spongiotic-phase fenestral otosclerosis in an objective manner.

Current Trends, Controversies, and Future Directions in the Evaluation and Management of Superior Canal Dehiscence Syndrome

Patients with superior canal dehiscence syndrome (SCDS) can present with a range of auditory and/or vestibular signs and symptoms that are associated with a bony defect of the superior semicircular canal (SSC). Over the past two decades, advances in diagnostic techniques have raised the awareness of SCDS and treatment approaches have been refined to improve patient outcomes. However, a number of challenges remain. First, there is currently no standardized clinical testing algorithm for quantifying the effects of superior canal dehiscence (SCD). SCDS mimics a number of common otologic disorders and established metrics such as supranormal bone conduction thresholds and vestibular evoked myogenic potential (VEMP) measurements; although useful in certain cases, have diagnostic limitations. Second, while high-resolution computed tomography (CT) is the gold standard for the detection of SCD, a bony defect does not always result in signs and symptoms. Third, even when SCD repair is indicated, there is a lack of consensus about nomenclature to describe the SCD, ideal surgical approach, specific repair techniques, and type of materials used. Finally, there is no established algorithm in evaluation of SCDS patients who fail primary repair and may be candidates for revision surgery. Herein, we will discuss both contemporary and emerging diagnostic approaches for patients with SCDS and highlight challenges and controversies in the management of this unique patient cohort.

CT of Skull Base Fractures: Classification Systems, Complications, and Management

As advances in prehospital and early hospital care improve survival of the head-injured patient, radiologists are increasingly charged with understanding the myriad skull base fracture management implications conferred by CT. Successfully parlaying knowledge of skull base anatomy and fracture patterns into precise actionable clinical recommendations is a challenging task. The authors aim to provide a pragmatic overview of CT for skull base fractures within the broader context of diagnostic and treatment planning algorithms. Laterobasal, frontobasal, and posterior basal fracture patterns are emphasized. CT often plays a complementary, supportive, or confirmatory role in management of skull base fractures in conjunction with results of physical examination, laboratory testing, and neurosensory evaluation. CT provides prognostic information about short- and long-term risk of cerebrospinal fluid (CSF) leak, encephalocele, meningitis, facial nerve paralysis, hearing and vision loss, cholesteatoma, vascular injuries, and various cranial nerve palsies and syndromes. The radiologist should leverage understanding of specific strengths and limitations of CT to anticipate next steps in the skull base fracture management plan. Additional imaging is warranted to clarify ambiguity (particularly for potential sources of CSF leak); in other cases, clinical and CT criteria alone are sufficient to determine the need for intervention and the choice of surgical approach. The radiologist should be able to envision stepping into a multidisciplinary planning discussion and engaging neurotologists, neuro-ophthalmologists, neurosurgeons, neurointerventionalists, and facial reconstructive surgeons to help synthesize an optimal management plan after reviewing the skull base CT findings at hand. Online supplemental material is available for this article. ^©RSNA, 2021.

Postoperative Imaging of the Temporal Bone

The anatomy of the temporal bone is complex, and postoperative imaging evaluation of this bone can be challenging. Surgical approaches to the temporal bone can be categorized didactically into tympanoplasty and ossicular reconstruction, mastoidectomy, and approaches to the cerebellopontine angle and internal auditory canal (IAC). In clinical practice, different approaches can be combined for greater surgical exposure. Postoperative imaging may be required for follow-up of neoplastic lesions and to evaluate unexpected outcomes or complications of surgery. CT is the preferred modality for assessing the continuity of the reconstructed conductive mechanism, from the tympanic membrane to the oval window, with use of grafts or prostheses. It is also used to evaluate aeration of the tympanic and mastoid surgical cavities, as well as the integrity of the labyrinth, ossicular chain, and tegmen. MRI is excellent for evaluation of soft tissue. Use of a contrast-enhanced fat-suppressed MRI sequence is optimal for follow-up after IAC procedures. Non-echo-planar diffusion-weighted imaging is optimal for detection of residual or recurrent cholesteatoma. The expected imaging findings and complications of the most commonly performed surgeries involving the temporal bone are summarized in this review. Online supplemental material is available for this article. ^©RSNA, 2021.

Beyond Tympanomastoidectomy: A Review of Less Common Postoperative Temporal Bone CT Findings

Postoperative temporal bone imaging after surgical procedures such as ossiculoplasty, tympanomastoidectomy, cochlear implantation, and vestibular schwannoma resection is often encountered in clinical neuroradiology practice. Less common otologic procedures can present diagnostic dilemmas, particularly if access to prior operative reports is not possible. Lack of familiarity with the less common surgical procedures and expected postoperative changes may render radiologic interpretation challenging. This review illustrates key imaging findings after surgery for Ménière disease, superior semicircular canal dehiscence, temporal encephalocele repairs, internal auditory canal decompression, active middle ear implants, jugular bulb and sigmoid sinus dehiscence repair, and petrous apicectomy.

Treatment of patients with glomus jugulare tumours (GJT) and its subjective effect on quality of life (QoL) measures

Cerebellopontine angle (CPA) tumours account for 6-10% of intracranial tumours. The most common CPA tumours are vestibular schwannomas (VS), also known as acoustic neuromas, benign tumours of the vestibulocochlear nerve. Less common but symptomatic skull base lesions are glomus jugulare tumours (GJT), of which approximately 40% are identified as CPA tumours. Initial symptoms for GJT may include hearing loss and tinnitus and progress to various cranial nerve dysfunctions. Three well-accepted treatment modalities for such tumours include surgical resection, radiotherapy and/or conservative management employing serial MR or CT imaging. Patients' quality of life may be impacted by different treatment methods, so treatment decisions should be client centered.

Skull Base-related Lesions at Routine Head CT from the Emergency Department: Pearls, Pitfalls, and Lessons Learned

Routine non-contrast material-enhanced head CT is one of the most frequently ordered studies in the emergency department. Skull base-related pathologic entities, often depicted on the first or last images of a routine head CT study, can be easily overlooked in the emergency setting if not incorporated in the interpreting radiologist's search pattern, as the findings can be incompletely imaged. Delayed diagnosis, misdiagnosis, or lack of recognition of skull base pathologic entities can negatively impact patient care. This article reviews and illustrates the essential skull base anatomy and common blind spots that are important to radiologists who interpret nonenhanced head CT images in the acute setting. The imaging characteristics of important "do not miss" lesions are emphasized and categorized by their cause and location within the skull base, and the potential differential diagnoses are discussed. An interpretation checklist to improve diagnostic accuracy is provided. ^©RSNA, 2019.

Active middle ear implantation: imaging in the pre-operative planning and post-operative assessment of the Vibrant SoundbridgeTM

Active middle ear implants augment sound waves and directly stimulate the middle ear structures. The most frequently utilised active middle ear implant is the Vibrant Soundbridge ^TM (VSB).CT plays a vital role in appropriate patient selection and surgical planning of active middle ear implant surgery. The VSB ^TM offers a number of options for implant placement. The ideal location is influenced by the patient's middle ear and mastoid anatomy as well as the type and severity of the hearing loss. CT provides important information on the surgical access to the middle ear and helps determine the most appropriate implant site by assessing the adjacent middle ear anatomy and the continuity of the ossicular chain. Post-operative active middle ear implant imaging may be indicated in the setting of poor auditory outcomes and when revision surgery is being considered so as to assess for suboptimal implant placement or migration.This pictorial review will describe the VSB ^TM middle ear device and explain the role of imaging in both the pre-operative and post-operative settings.

Traumatic Injury of the Petrous Part of the Temporal Bone: Keys for Reporting a Complex Diagnosis

Fractures of the petrous part of the temporal bone are a common lesion of the base of the skull; most of these fractures result from high-energy trauma. In patients with multiple trauma, these injuries can be detected on CT scans of the head and neck, where the direct and indirect signs are usually sufficient to establish the diagnosis. It is important to these fractures because the temporal bone has critical structures and the complexity of this region increases the risk of error unless special care is taken. This article reviews the key anatomical points, the systematization of the imaging findings, and the classifications used for temporal bone fracture. We emphasize the usefulness of identifying and describing the findings in relation to important structures in this region, of looking for unseen fractures suspected through indirect signs, and of identifying anatomical structures that can simulate fractures. We point out that the classical classifications of these fractures are less useful, although they continue to be used for treatment decisions.

Hearing disorders - findings on computed tomography and magnetic resonance imaging: pictorial essay

Hearing disorders are usually unilateral and are more common in women. They can be congenital or acquired, and hearing loss is categorized as sensorineural, conductive, or mixed. The onset of hearing loss can be progressive or sudden, and it is a common reason for seeking medical attention. In this context, computed tomography and magnetic resonance imaging have assumed critical roles in the search for an etiological diagnosis and in guiding the therapeutic approach. In this pictorial essay, we illustrate the common causes of hearing loss, discussing the possible differential diagnoses and highlighting the most relevant imaging findings.

Temporal bone contrast-enhanced high-resolution CT evaluation of pulsatile tinnitus after sigmoid sinus wall reconstruction

BACKGROUND

Sigmoid sinus wall reconstruction (SSWR) is a proven effective treatment for pulsatile tinnitus (PT) caused by sigmoid sinus wall dehiscence (SSWD) with or without sigmoid sinus diverticulum (SSD); however, comprehensive analysis of the postoperative imaging manifestations has not yet been reported.

PURPOSE

To analyze temporal bone computed tomography (CT) imaging features following SSWR in patients with PT.

MATERIAL AND METHODS

Following SSWR, temporal bone contrast-enhanced high-resolution CT (HRCT) images from 33 PT cases were retrospectively analyzed. Patients were divided into two groups based on follow-up interval: a short-interval group (≤18 months, 12 cases) and a long-interval group (>18 months, 21 cases). The mending material density and morphology was analyzed. Postoperative changes of the venous sinus were evaluated. Imaging manifestations of the normal temporal bone and mastoid air cells adjacent to the operative field were observed.

RESULTS

The order of CT values of mending materials was significantly lower in the short-interval group than in the long-interval group (Z = -4.716, P < 0.001); the incidence of complete newly remodeled cortical bone on the rim of the mending materials was significantly higher in the long-interval group than in the short-interval group ( P < 0.001). Eleven patients (33.3%) showed varying degrees of remnant SSWD. The mending materials and normal mastoid bone structure showed complete fusion (n = 12, 36.4%), partial fusion (n = 16, 48.5%), or complete separation (n = 5, 15.2%).

CONCLUSION

Temporal bone contrast-enhanced HRCT can be used to observe imaging features of the mending materials, venous sinus, adjacent normal temporal bone and mastoid air cells following SSWR.

Retrospective Review of Otic Capsule Contour and Thickness in Patients with Otosclerosis and Individuals with Normal Hearing on CT

BACKGROUND AND PURPOSE

Otosclerosis is commonly identified on CT as a focus of hypodensity in the otic capsule anterior to the oval window. However, otosclerosis can have a sclerotic phase approximating the density of normal bone, making diagnosis challenging. This study assesses differences in otic capsule contour and thickness anterolateral to the anterior margin of the oval window in patients with otosclerosis compared with individuals with normal hearing.

MATERIALS AND METHODS

Axial CT of 104 ears with clinically diagnosed otosclerosis and 108 consecutive ears of audiometrically normal individuals were retrospectively reviewed. Two radiologists independently evaluated the pattern of otosclerosis, otic capsule contour, and bone thickness on standardized axial images at the level of the oval window and cochleariform process. Measurements were made from the posterolateral margin of the cochlea to the apex of the otic capsule convex contour just anterolateral to the anterior margin of the oval window. In the absence of a convex contour, the sulcus between the oval window and the cochleariform process was identified, and measurement to the depth of the sulcus was used. Receiver operating characteristic analysis determined the best cutoff value of otic capsule thickness.

RESULTS

Mean otic capsule thickness (2 SDs) was 3.08 (0.93) mm and 1.82 (0.31) mm in patients with otosclerosis and individuals with normal hearing, respectively (P < .001), with excellent interobserver agreement. Otic capsule thickness of >2.3 mm had 96.2% sensitivity, 100% specificity, 100% positive predictive value, and 96.4% negative predictive value for otosclerosis. A bulging/convex contour of the otic capsule had 68.3% sensitivity, 98.1% specificity, 97.3% positive predictive value, and 76.3% negative predictive value.

CONCLUSIONS

Patients with otosclerosis have significantly thicker bone abutting the oval window than individuals with normal hearing.

Otosclerosis and Dysplasias of the Temporal Bone

Many bone dysplasias, some common and others rare, may involve the temporal bone causing conductive, sensorineural, or mixed hearing loss, vestibular dysfunction, or skull base foraminal narrowing, potentially affecting quality of life. Some conditions may affect only the temporal bone, whereas others may be more generalized, involving different regions of the body. High-resolution computed tomography may detect subtle osseous changes that can help define the type of dysplasia, and MR imaging can help define the degree of activity of lesions and potential associated complications.

ADC Benchmark Range for Correct Diagnosis of Primary and Recurrent Middle Ear Cholesteatoma

OBJECTIVES

Magnetic resonance imaging (MRI) and in particular diffusion-weighted imaging (DWI) have been broadly proven to be the reference imaging method to discriminate between cholesteatoma and noncholesteatomatous middle ear lesions, especially when high tissue specificity is required. The aim of this study is to define a range of apparent diffusion coefficient (ADC) values within which the diagnosis of cholesteatoma is almost certain.

METHODS

The study was retrospectively conducted on a cohort of 124 patients. All patients underwent first- or second-look surgery because primary or secondary acquired cholesteatoma was clinically suspected; they all had preoperative MRI examination 15 days before surgery, including DWI from which the ADC maps were calculated.

RESULTS

Average ADC value for cholesteatomas was 859,4 × 10-6 mm2/s (range 1545 × 10-6 mm2/s; IQR = 362 × 10-6 mm2/s; σ = 276,3 × 10-6 mm2/s), while for noncholesteatomatous inflammatory lesions, it was 2216,3 × 10-6 mm2/s (range 1015 × 10-6 mm2/s; IQR = 372,75 × 10-6 mm2/s; σ = 225,6 × 10-6 mm2/s). Interobserver agreement with Fleiss' Kappa statistics was 0,96. No overlap between two groups' range of values was found and the difference was statistically significant for p < 0.0001.

CONCLUSIONS

We propose an interval of ADC values that should represent an appropriate benchmark range for a correct differentiation between cholesteatoma and granulation tissue or fibrosis of noncholesteatomatous inflammatory lesions.

Additive value of "otosclerosis-weighted" images for the CT diagnosis of fenestral otosclerosis

Background Otosclerotic foci are usually seen as minute low-density lesions and this may be attributed to relatively low sensitivity on visual assessment using computed tomography (CT). Otosclerotic foci can be detected by using the accurate region of interest (ROI) setting, while small ROI settings by less-experienced radiologists may result in false negative findings. Purpose To evaluate the diagnostic ability of our proposed method ("otosclerosis-weighted" imaging [OWI]), which is based on reversing the density, compared with conventional CT (CCT) imaging alone. Material and Methods Temporal bone CTs of consecutive patients with otosclerosis were analyzed. Gender- and age-matched control participants were also included. All CT images were obtained using a 64-detector row scanner. OWI was obtained by extracting the temporal bone region using the threshold technique and reversing the density (black to white). Four independent radiologists took part in two reading sessions. In the first session, the observers read only CCT imaging. In the second session, they read OWI along with the CCT imaging. Sensitivity was assessed for the four readers. Results Thirty temporal bones of 25 patients with otosclerosis (3 men, 22 women; mean age, 53.9 ± 9.0 years) and 30 temporal bones of 30 control participants (4 men, 26 women; mean age, 44.0 ± 16.2 years) were included. For all observers, reading with a combination of the two methods was associated with a higher sensitivity (63.3-80.0%) than with conventional CT images alone (30.0-60.0%; P < 0.05, each). Conclusion Application of our proposed method based on threshold value may help detect foci of fenestral otosclerosis.

Unilateral Enlarged Vestibular Aqueduct Syndrome and Bilateral Endolymphatic Hydrops

Enlarged vestibular aqueduct (EVA) syndrome is a common congenital inner ear malformation characterized by a vestibular aqueduct with a diameter larger than 1.5 mm, mixed or sensorineural hearing loss that ranges from mild to profound, and vestibular disorders that may be present with a range from mild imbalance to episodic objective vertigo. In our study, we present the case of a patient with unilateral enlarged vestibular aqueduct and bilateral endolymphatic hydrops (EH). EH was confirmed through anamnestic history and audiological exams; EVA was diagnosed using high-resolution CT scans and MRI images. Therapy included intratympanic infusion of corticosteroids with a significant hearing improvement, more evident in the ear contralateral to EVA. Although most probably unrelated, EVA and EH may present with similar symptoms and therefore the diagnostic workup should always include the proper steps to perform a correct diagnosis. Association between progression of hearing loss and head trauma in patients with a diagnosis of EVA syndrome is still uncertain; however, these individuals should be advised to avoid activities that increase intracranial pressure to prevent further hearing deterioration. Intratympanic treatment with steroids is a safe and well-tolerated procedure that has demonstrated its efficacy in hearing, tinnitus, and vertigo control in EH.

Improvement in imaging common temporal bone pathologies at 3 T MRI: small structures benefit from a small field of view

AIM

To compare image quality and evaluate its clinical importance in common temporal bone pathologies of a pTX-SPACE (parallel transmit [pTX] three-dimensional turbo spin-echo with variable flip angle [SPACE]) magnetic resonance imaging (MRI) sequence improved for spatial resolution to a standard-SPACE sequence exhibiting the same scan time at 3 T.

MATERIALS AND METHODS

Thirty-four patients were examined using a standard-SPACE and resolution improved pTX-SPACE sequence at 3 T MRI. The signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and image quality were assessed. Diseases investigated were vestibular schwannoma (VS), intralabyrinthine schwannoma (ILS), inner ear malformations, labyrinthitis, temporal bone fractures, and situation after VS resection.

RESULTS

Edge definition, intratumoural pattern, discrimination of VS from the modiolus and edge definition of ILS, separability from the spiral lamina, and detectability within cochlear turns were improved on the pTX-SPACE sequence. Detectability of malformations, post-traumatic changes, and discrimination of the cochlear and facial nerve after VS resection was improved on the pTX-SPACE sequence. In labyrinthitis, pTX-SPACE was not superior to standard-SPACE. The SNR and CNR were significantly reduced for pTX-SPACE.

CONCLUSIONS

pTX-SPACE significantly improves the detectability of temporal bone diseases, in particular, VS, ILS, and post-VS resection.

Contralateral Cochlear Labyrinthine Concussion without Temporal Bone Fracture: Unusual Posttraumatic Consequence

Introduction. Labyrinthine concussion is a term used to describe a rare cause of sensorineural hearing loss with or without vestibular symptoms occurring after head trauma. Isolated damage to the inner ear without involving the vestibular organ would be designated as a cochlear labyrinthine concussion. Hearing loss is not a rare finding in head trauma that involves petrous bone fractures. Nevertheless it generally occurs ipsilateral to the side of the head injury and extraordinarily in the contralateral side and moreover without the presence of a fracture. Case Report. The present case describes a 37-year-old patient with sensorineural hearing loss and tinnitus in his right ear after a blunt head trauma of the left-sided temporal bone (contralateral). Otoscopy and radiological images showed no fractures or any abnormalities. A severe sensorineural hearing loss was found in his right ear with a normal hearing of the left side. Conclusion. The temporal bone trauma requires a complete diagnostic battery which includes a neurotologic examination and a high resolution computed tomography scan in the first place. Hearing loss after a head injury extraordinarily occurs in the contralateral side of the trauma as what happened in our case. In addition, the absence of fractures makes this phenomenon even more unusual.

Vestibular Aqueduct Measurements in the 45° Oblique (Pöschl) Plane

BACKGROUND AND PURPOSE

The 45° oblique (Pöschl) plane allows reliable depiction of the vestibular aqueduct, with virtually its entire length often visible on 1 CT image. We measured its midpoint width in this plane, aiming to determine normal measurement values based on this plane.

MATERIALS AND METHODS

We retrospectively evaluated temporal bone CT studies of 96 pediatric patients without sensorineural hearing loss. Midvestibular aqueduct widths were measured in the 45° oblique plane by 2 independent readers by visual assessment (subjective technique). The vestibular aqueducts in 4 human cadaver specimens were also measured in this plane. In addition, there was a specimen that had undergone CT scanning before sectioning, and measurements made on that CT scan and on the histologic section were compared. Measurements from the 96 patients' CT images were then repeated by using findings derived from the radiologic-histologic comparison (objective technique).

RESULTS

All vestibular aqueducts were clearly identifiable on 45° oblique-plane CT images. The mean for subjective measurement was 0.526 ± 0.08 mm (range, 0.337-0.947 mm). The 97.5th percentile value was 0.702 mm. The mean for objective measurement was 0.537 ± 0.077 mm (range, 0.331-0.922 mm). The 97.5th percentile value was 0.717 mm.

CONCLUSIONS

Measurements of the vestibular aqueduct can be performed reliably and accurately in the 45° oblique plane. The mean midpoint width was 0.5 mm, with a range of 0.3-0.9 mm. These may be considered normal measurement values for the vestibular aqueduct midpoint width when measured in the 45° oblique plane.