Retrospective Analysis of the Association of a Small Vestibular Aqueduct with Cochleovestibular Symptoms in a Large, Single-Center Cohort Undergoing CT.

BACKGROUND AND PURPOSE: Temporal bones in some patients with Ménière disease have demonstrated small vestibular aqueducts; however, the prevalence and clinical importance of small vestibular aqueducts remain unclear in patients without Ménière disease. This study correlates the presence of a small vestibular aqueduct with cochleovestibular symptoms. MATERIALS AND METHODS: Consecutive temporal bone CTs in adults from January to December 2020 were reviewed. The midpoint vestibular aqueduct size in the 45°-oblique Pöschl view was measured by 2 reviewers independently in 684 patients (1346 ears). Retrospective chart review for the clinical diagnosis of Ménière disease, the presence of cochleovestibular symptoms, and indications for CT was performed. RESULTS: Fifty-two of 684 patients (7.6% of patients, 62/1346 ears) had small vestibular aqueducts. Twelve patients (15/1346 ears) had Ménière disease. Five of 12 patients with Ménière disease (5 ears) had a small vestibular aqueduct. There was a significant correlation between a small vestibular aqueduct and Ménière disease (P < .001). There was no statistical difference between the small vestibular aqueduct cohort and the cohort with normal vestibular aqueducts (0.3-0.7 mm) regarding tinnitus (P = .06), hearing loss (P = .88), vertigo (P = .26), dizziness (P = .83), and aural fullness (P = .61). CONCLUSIONS: While patients with Ménière disease were proportionately more likely to have a small vestibular aqueduct than patients without Ménière disease, the small vestibular aqueduct was more frequently seen in patients without Ménière disease and had no correlation with hearing loss, vertigo, dizziness, or aural fullness. We suggest that the finding of a small vestibular aqueduct on CT could be reported by radiologists as a possible finding in Ménière disease, but it remains of uncertain, and potentially unlikely, clinical importance in the absence of symptoms of Ménière disease.

Retrospective Review of Midpoint Vestibular Aqueduct Size in the 45° Oblique (Pöschl) Plane and Correlation with Hearing Loss in Patients with Enlarged Vestibular Aqueduct.

BACKGROUND AND PURPOSE: Vestibular aqueduct measurements in the 45° oblique (Pöschl) plane provide a reliable depiction of the vestibular aqueduct; however, adoption among clinicians attempting to counsel patients has been limited due to the lack of correlation with audiologic measures. This study aimed to determine the correlation between midpoint vestibular aqueduct measurements in the Pöschl plane in patients with an enlarged vestibular aqueduct with repeat audiologic measures. MATERIALS AND METHODS: Two radiologists independently measured the midpoint vestibular aqueduct diameter in the Pöschl plane reformatted from CT images in 54 pediatric patients (77 ears; mean age at first audiogram, 5 years) with an enlarged vestibular aqueduct. Four hundred nineteen audiograms were reviewed, with a median of 6 audiograms per patient (range, 3-17; mean time between first and last audiograms, 97.4 months). The correlation between midpoint vestibular aqueduct size and repeat audiologic measures (pure tone average, speech-reception threshold, and word recognition score) using a linear mixed-effects model was determined. RESULTS: The mean midpoint vestibular aqueduct size was 1.78 mm (range, 0.81-3.46 mm). There was excellent interobserver reliability with intraclass correlation coefficients for the 2 readers measuring 0.92 (P < .001). Each millimeter increase in vestibular aqueduct size was associated with an increase of 10.5 dB (P = .006) in the pure tone average, an increase of 14.0 dB (P = .002) in the speech-reception threshold, and a decrease in the word recognition score by 10.5% (P = .05). CONCLUSIONS: Midpoint vestibular aqueduct measurements in the Pöschl plane are highly reproducible and demonstrate a significant correlation with audiologic data in this longitudinal study with repeat measures. These data may be helpful for clinicians who are counseling patients with an enlarged vestibular aqueduct using measurements obtained in the Pöschl plane.

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.

Comparison of Intraoperative Sonography and Histopathologic Evaluation of Tumor Thickness and Depth of Invasion in Oral Tongue Cancer: A Pilot Study.

BACKGROUND AND PURPOSE: For primary squamous cell carcinoma of the oral tongue, accurate assessment of tumor thickness and depth of invasion is critical for staging and operative management. Currently, typical imaging modalities used for preoperative staging are CT and MR imaging. Intraoperatively, CT or MR imaging cannot provide real-time guidance, and assessment by manual palpation is limited in precision. We investigated whether intraoperative sonography is a feasible technique for assessment of tumor thickness and depth of invasion and validated its accuracy by comparing it with histopathologic evaluation of the resected specimen. MATERIALS AND METHODS: Twenty-six patients with squamous cell carcinoma of the oral tongue who underwent tumor resection by a single surgeon between March 31, 2016, and April 26, 2019, were prospectively identified. Intraoperative sonography was obtained in planes longitudinal and transverse to the long axis of the tumor. Twenty-two patients had archived images that allowed measurements of tumor thickness and depth of invasion sonographically. Two patients had dysplasia and were excluded. The remaining 20 patients had histologic tumor thickness and histologic depth of invasion measured by a single pathologist. RESULTS: The mean sonographic tumor thickness was 7.5 ± 3.5 mm, and the mean histologic tumor thickness was 7.0 ± 4.2 mm. Mean sonographic depth of invasion and histologic depth of invasion were 6.6 ± 3.4 and 6.4 ± 4.4 mm, respectively. There was excellent correlation between sonographic and histologic measurements for both tumor thickness and depth of invasion with Pearson correlation coefficients of 0.95 (95% CI, 0.87-0.98) and 0.95 (95% CI, 0.87-0.98), respectively. CONCLUSIONS: Intraoperative sonography can provide reliable, real-time assessment of the extent of tongue tumors.

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.

Optimization of Quantitative Dynamic Postgadolinium MRI Technique Using Normalized Ratios for the Evaluation of Temporomandibular Joint Synovitis in Patients with Juvenile Idiopathic Arthritis.

BACKGROUND AND PURPOSE: MR imaging has been shown to be useful in the diagnosis of juvenile idiopathic arthritis of the temporomandibular joint. Prior MR imaging approaches have relied mainly on the subjective interpretation of synovial enhancement as a marker for synovial inflammation. Although, more recently, several attempts have been made to quantify synovial enhancement, these methods have not taken into account the dynamic enhancement characteristics of the temporomandibular joint and the effect of sampling time. Our aim was to develop a clinically feasible, reproducible, dynamic, contrast-enhanced MR imaging technique for the quantitative assessment of temporomandibular joint synovitis in patients with juvenile idiopathic arthritis and to study the effect of sampling time on the evaluation of synovitis. MATERIALS AND METHODS: This was a retrospective study of all patients who had dynamic, contrast-enhanced coronal T1 3T MR imaging through the temporomandibular joint at our institution between January 1, 2015, and July 8, 2016. Patients in this cohort included those with a history of juvenile idiopathic arthritis and control patients who underwent MR imaging for other routine, clinical purposes. Synovial enhancement was calculated for each temporomandibular joint using 3 different types of equations termed normalization ratios. The enhancement profiles generated by each equation were studied to determine which provided the best discrimination between affected and unaffected joints, was the least susceptible to sampling errors, and was the most clinically feasible. RESULTS: A ratio of synovial enhancement (defined as the difference between the postgadolinium and the pregadolinium T1 signal of the synovium) to the postgadolinium signal of the longus capitis provided the best discrimination between affected and unaffected joints, the least susceptibility to sampling error, and was thought to be the most clinically feasible method of quantification of synovial inflammation. Additional synovial enhancement ratios studied did not provide the same level rates of discrimination between the affected and unaffected joints and were thought to be too temporally variable to provide reliable clinical use. CONCLUSIONS: We provide a robust, reproducible, dynamic gadolinium-enhanced MR imaging technique for the quantitative assessment of temporomandibular joint synovitis in patients with juvenile idiopathic arthritis.

Measurement for Detection of Incomplete Partition Type II Anomalies on MR Imaging.

BACKGROUND AND PURPOSE: Incomplete partition type II of the cochlea, commonly coexisting with an enlarged vestibular aqueduct, can be a challenging diagnosis on MR imaging due to the presence of a dysplastic spiral lamina-basilar membrane neural complex, which can resemble the normal interscalar septum. The purpose of this study was to determine a reproducible, quantitative cochlear measurement to assess incomplete partition type II anomalies in patients with enlarged vestibular aqueducts using normal-hearing ears as a control population. MATERIALS AND METHODS: Retrospective analysis of 27 patients with enlarged vestibular aqueducts (54 ears) and 28 patients (33 ears) with normal audiographic findings who underwent MR imaging was performed. Using reformatted images from a cisternographic 3D MR imaging produced in a plane parallel to the lateral semicircular canal, we measured the distance (distance X) between the osseous spiral lamina-basilar membrane complex of the upper basal turn and the first linear signal void anterior to the basilar membrane. RESULTS: The means of distance X in patients with normal hearing and prospectively diagnosed incomplete partition type II were, respectively, 0.93 ± 0.075 mm (range, 0.8-1.1 mm) and 1.55 ± 0.25 mm (range, 1-2.1 mm; P < .001). Using 3 SDs above the mean of patients with normal hearing (1.2 mm) as a cutoff for normal, we diagnosed 21/27 patients as having abnormal cochleas; 4/21 were diagnosed retrospectively. This finding indicated that almost 20% of patients were underdiagnosed. Interobserver agreement with 1.2 mm as a cutoff between normal and abnormal produced a κ score of 0.715 (good). CONCLUSIONS: Incomplete partition type II anomalies on MR imaging can be subtle. A reproducible distance X of ≥1.2 mm is considered abnormal and may help to prospectively diagnose incomplete partition type II anomalies.

Trochlear Groove and Trochlear Cistern: Useful Anatomic Landmarks for Identifying the Tentorial Segment of Cranial Nerve IV on MRI.

BACKGROUND AND PURPOSE: The trochlear groove and trochlear cistern are anatomic landmarks closely associated with the tentorial segment of cranial nerve IV. The purposes of this study were to describe the MR imaging appearances of the trochlear groove and trochlear cistern and to test our hypothesis that knowledge of these anatomic landmarks facilitates identification of cranial nerve IV in routine clinical practice. MATERIALS AND METHODS: For this retrospective study, consecutive MR imaging examinations of the sinuses performed in 25 patients (50 sides) at our institution were reviewed. Patient characteristics and study indications were recorded. Three readers performed independent assessments of trochlear groove, cistern, and nerve visibility on coronal images obtained by using a T2-weighted driven equilibrium radiofrequency reset pulse sequence. RESULTS: Interobserver agreement was 78% for visibility of the trochlear groove, 56% for the trochlear cistern, and 68% for cranial nerve IV. Following consensus review, the trochlear groove was present in 44/50 sides (88%), the trochlear cistern was present in 25/50 sides (50%), and cranial nerve IV was identified in 36/50 sides (72%). When the trochlear groove was present, cranial nerve IV was identified in 35/44 sides (80%), in contrast to 1/6 sides (17%) with no groove (P = .0013). When the trochlear cistern was present, cranial nerve IV was identified in 23/25 sides (92%), in contrast to 13/25 sides (52%) with no cistern (P = .0016). CONCLUSIONS: The trochlear groove and trochlear cistern are anatomic landmarks that facilitate identification of cranial nerve IV in routine clinical practice.

Plunging ranula with prestyloid parapharyngeal space, masticator space, and parotid gland extension.

Plunging ranula with prestyloid parapharyngeal space, masticator space, and parotid gland extension. INTRODUCTION: Ranulas develop from mucous extravasation secondary to sublingual gland duct obstruction or trauma. Plunging ranula usually dive into the submandibular space. METHODS: This is the first reported case of a plunging ranula with direct extension to the prestyloid parapharyngeal space, masticator space, and parotid gland with avoidance of the submandibular space. RESULTS: The patient presented with a tender parotid mass, of which the differential is broad, including parotitis, parotid malignancy, metastatic malignancy, lymphoma, as well as other infectious etiologies. When an intraoral component is not identified, other differential considerations would be thyroglossal duct cyst, branchial cleft cyst, parathyroid cyst, cervical thymic cyst, dermoid cyst, cystic hygroma, or benign teratoma. CONCLUSION: The case is unique due to ranula extension into multiple spaces. For optimal treatment, the sublingual gland along with its tract and contents needs to completely removed.

Spectrum of Third Window Abnormalities: Semicircular Canal Dehiscence and Beyond.

Third window abnormalities are defects in the integrity of the bony structure of the inner ear, classically producing sound-/pressure-induced vertigo (Tullio and Hennebert signs) and/or a low-frequency air-bone gap by audiometry. Specific anatomic defects include semicircular canal dehiscence, perilabyrinthine fistula, enlarged vestibular aqueduct, dehiscence of the scala vestibuli side of the cochlea, X-linked stapes gusher, and bone dyscrasias. We discuss these various entities and provide key examples from our institutional teaching file with a discussion of symptomatology, temporal bone CT, audiometry, and vestibular-evoked myogenic potentials.

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.

Optimal Virtual Monochromatic Images for Evaluation of Normal Tissues and Head and Neck Cancer Using Dual-Energy CT.

BACKGROUND AND PURPOSE: Dual-energy CT is not used routinely for evaluation of the head and neck, and there is no consensus on the optimal virtual monochromatic image energies for evaluating normal tissues or head and neck cancer. We performed a quantitative evaluation to determine the optimal virtual monochromatic images for visualization of normal tissues, head and neck squamous cell carcinoma, and lymphadenopathy. MATERIALS AND METHODS: Dual-energy CT scans from 10 healthy patients and 30 patients with squamous cell carcinoma were evaluated at different virtual monochromatic energy levels ranging from 40 to 140 keV. The signal-to-noise ratios of muscles at 6 different levels, glands (parotid, sublingual, submandibular, and thyroid), 30 tumors, and 17 metastatic lymph nodes were determined as measures of optimal image quality. Lesion attenuation and contrast-to-noise ratios (compared with those of muscle) were evaluated to assess lesion conspicuity. RESULTS: The optimal signal-to-noise ratio for all the tissues was at 65 keV (P < .0001). However, tumor attenuation (P < .0001), attenuation difference between tumor and muscles (P = .03), and lesion contrast-to-noise ratios (P < .0001) were highest at 40 keV. CONCLUSIONS: The optimal image signal-to-noise ratio is at 65 keV, but tumor conspicuity compared with that of muscle is greatest at 40 keV. Optimal evaluation of the neck may be best achieved by a multiparametric approach, with 65-keV virtual monochromatic images providing the best overall image quality and targeted use of 40-keV virtual monochromatic images for tumor evaluation.

Different spectral hounsfield unit curve and high-energy virtual monochromatic image characteristics of squamous cell carcinoma compared with nonossified thyroid cartilage.

BACKGROUND AND PURPOSE: The attenuation of normal nonossified thyroid cartilage can be similar to that of head and neck squamous cell carcinoma on CT. We compared dual-energy CT spectral Hounsfield unit attenuation characteristics of nonossified thyroid cartilage with that of squamous cell carcinoma to determine the optimal virtual monochromatic image reconstruction energy levels for distinguishing tumor from normal nonossified thyroid cartilage. MATERIALS AND METHODS: Dual-energy CT scans from 30 patients with histopathology-proved squamous cell carcinoma at different primary sites (laryngeal and nonlaryngeal) and 10 healthy patients were evaluated. Patients were scanned with a 64-section single-source scanner with fast-kilovolt (peak) switching, and scans were reconstructed at different virtual monochromatic energy levels ranging from 40 to 140 keV. Spectral attenuation curves of tumor and nonossified thyroid cartilage were quantitatively evaluated and compared. Any part of the tumor invading the cartilage, when present, was excluded from ROI analysis to avoid cross-contamination from areas where there could be a mixture of cartilage and invading tumor. RESULTS: Normal nonossified thyroid cartilage had a characteristic, predictable spectral attenuation curve that was different from that of tumors. The greatest difference in attenuation of nonossified cartilage compared with tumor was on virtual monochromatic images of ≥95 keV (P < .0001), with sharp contrast between the relatively high attenuation of nonossified cartilage compared with that of tumor. CONCLUSIONS: Head and neck squamous cell carcinoma has significantly different attenuation on virtual monochromatic images of ≥95 keV, compared with nonossified thyroid cartilage.

CT Findings in the External Auditory Canal after Transcanal Surgery.

BACKGROUND AND PURPOSE: Middle ear surgery is often performed through the external auditory canal, and the CT appearance of the external auditory canal after transcanal middle ear surgery can mimic erosive pathology such as carcinoma, external auditory canal cholesteatoma, or necrotizing external otitis. We reviewed the CT findings in a group of patients following transcanal surgery to highlight this potential pitfall in interpretation. MATERIALS AND METHODS: Twenty-seven temporal bones in 25 patients with a history of a transcanal approach to the middle ear and available postoperative CT imaging were identified. Images were assessed for changes along or involving the walls of the external auditory canal, including widening, irregularity, bony defects, and soft tissue opacification. RESULTS: Osseous changes along the floor of the external auditory canal were demonstrated in 25 of 27 (92.6%) temporal bone CT scans. Similar changes were present in the superior and anterior walls of the external auditory canal in 21 and 18 temporal bones, respectively. The anterior wall was the most common site for complete bony defects (10 of 27 temporal bones). The posterior wall was the least often involved, with osseous changes in 15 of 27 temporal bones and bony defects in 3 cases. Soft tissue thickening was seen most commonly along the floor. No patient was found to have a superimposed pathologic process of the external auditory canal. CONCLUSIONS: CT findings in the external auditory canal after transcanal surgery include thinning, irregularity and/or flattening of the bone, soft tissue thickening, and bony wall defects. Although these changes may be subtle, they may mimic pathology and should be included in the differential diagnosis of osseous abnormality of the external auditory canal.

Imaging findings in auto-atticotomy.

BACKGROUND AND PURPOSE: An acquired attic cholesteatoma may spontaneously drain externally into the external auditory canal, leaving a cavity in the attic with the shape of the original cholesteatoma but now filled with air, a phenomenon referred to as "nature's atticotomy" or auto-atticotomy. We describe and quantify the CT appearance of the auto-atticotomy cavity as it pertains to the appearance of the scutum and the lateral attic wall. MATERIALS AND METHODS: Twenty-one patients with erosion of the scutum and loss of the lower attic wall on MDCT were identified during a 5-year span. Images were assessed for measureable widening of the space between the ossicles and the lower lateral attic wall in the axial and coronal planes. Three measurements of the lateral attic were made on the axial images. Findings were compared with the same measurements in 20 control subjects. RESULTS: The 21 patients had a characteristic blunting of the scutum with loss of the lower lateral attic wall and widening of the lateral attic, consistent with an auto-atticotomy. There was a statistically significant (P < .001) widening of the lateral attic dimensions in the axial plane in the patients with auto-atticotomy. CONCLUSIONS: Spontaneously evacuated cholesteatoma may mimic a surgical atticotomy on MDCT. Scutal erosion and attic enlargement with a smoothly contoured bony remodeling of the lower lateral attic wall in a patient with no history of surgery suggest that a cholesteatoma was previously present and spontaneously drained.

A venous cause for facial canal enlargement: multidetector row CT findings and histopathologic correlation.

An enlarged facial nerve canal can be a seen in both pathologic and nonpathologic processes. The purposes of this report are the following: 1) to present a rare cause of bony facial nerve canal enlargement, due to an enlarged vein, with high-resolution MDCT and histopathologic correlation; and 2) to discuss the vascular anatomy that gives rise to this variant.

Comparison of 45 degrees oblique reformats with axial reformats in CT evaluation of the vestibular aqueduct.

BACKGROUND AND PURPOSE: Measurement of the vestibular aqueduct on CT scans of the temporal bone is important for the detection of large vestibular aqueduct syndrome; typically this is done in the axial plane. We sought to determine the usefulness of reformats performed in the 45 degrees oblique plane for evaluating the vestibular aqueduct. In addition, we provide reference measurements for the vestibular aqueduct in the 45 degrees oblique plane. MATERIALS AD METHODS: We selected 15 subjects referred for reasons other than sensorineural hearing loss, and without radiographic evidence of abnormality of the inner ear. Two neuroradiologists independently evaluated both axial and 45 degrees oblique images for ease in visualizing the vestibular aqueduct. Then, one of the readers (B.O.) performed reference measurements of the diameter at the mouth and midpoint of the aqueduct. RESULTS: Combining the results of both observers, we judged 82% of vestibular aqueducts as well-defined or easily traced on 45 degrees oblique views, whereas we judged only 55% as well-defined or easily traced on axial views. The difference in the degrees of visualization between the 45 degrees oblique and axial reformats was significant for observer 1 (P =.022) and observer 2 (P =.001). Intraobserver agreement about the visibility of the aqueduct was higher on the 45 degrees oblique than the axial views: (kappa = 0.682, SE = 0.171) for 45 degrees oblique reformats; (kappa = 0.480, SE = 0.145) for axial reformats. On the 45 degrees oblique reformats, the mean external aperture dimension of the vestibular aqueduct was measured as 0.616 +/- 0.133 mm, and the postisthmic segment had a mean width of 0.482 +/- 0.099 mm. CONCLUSIONS: The 45 degrees oblique plane gives a more reliable depiction of the vestibular aqueduct than the axial plane in CT evaluation of the temporal bone. This technique can be useful in cases of borderline enlargement of the vestibular aqueduct.

Unusual CT appearance in an odontogenic keratocyst of the mandible: case report.

An expansile lesion in the body of the left mandible had high attenuation (225 HU) on nonenhanced CT scans. Histologic examination revealed an odontogenic keratocyst with no evidence of mineralization or calcification within the lesion. The high attenuation was considered to be due to highly concentrated protein of thick, viscous keratin in the lumen of the keratocyst.

Anomalous facial nerve canal with cochlear malformations.

BACKGROUND AND PURPOSE: Anteromedial "migration" of the first segment of the facial nerve canal has been previously identified in a patient with a non-Mondini-type cochlear malformation. In this study, several patients with the same facial nerve canal anomaly were reviewed to assess for the association and type of cochlear malformation. METHODS: CT scans of the temporal bone of 15 patients with anteromedial migration of the first segment of the facial nerve canal were collected from routine departmental examinations. In seven patients, the anomalous course was bilateral, for a total of 22 cases. The migration was graded relative to normal as either mild/moderate or pronounced. The cochlea in each of these cases was examined for the presence and size of the basilar, second, and apical turns. The turns were either absent, small, normal, or enlarged. The CT scans of five patients with eight Mondini malformations were examined for comparison. RESULTS: The degree of the facial nerve migration was pronounced in nine cases and mild/moderate in 13. All 22 of these cases had associated cochlear abnormalities of the non-Mondini variety. These included common cavity anomalies with lack of definition between the cochlea and vestibule (five cases), cochleae with enlarged basilar turns and absent second or third turns (five cases), and cochleae with small or normal basilar turns with small or absent second or third turns (12 cases). None of the patients with Mondini-type cochlear malformations had anteromedial migration of the facial nerve canal. CONCLUSION: Anteromedial migration of the facial nerve canal occurs in association with some cochlear malformations. It did not occur in association with the Mondini malformations. A cochlea with a Mondini malformation, being similar in size to a normal cochlea, may physically prohibit such a deviation in course.