Reduction in Extraocular Muscle Cross-sectional Area and Correlation With Extraocular Motility and Diplopia Following Teprotumumab for Thyroid Eye Disease.

PURPOSE: To quantify changes in extraocular muscle (EOM) cross-sectional areas (CSA) on orbital imaging in patients with thyroid eye disease before and after teprotumumab treatment, and assess for correlation with clinical outcomes. METHODS: This retrospective study included thyroid eye disease patients treated with teprotumumab who had pre- and post-treatment CT imaging. Reformatted oblique coronal images were created for each orbit in a plane perpendicular to the optic nerve. EOM CSA measurements were performed by 2 radiographic reviewers and averaged. Primary outcomes included change in ratio of total EOM to orbit CSA, and of each individual muscle group to orbit CSA, before and after treatment. Secondary outcomes included subanalysis based on age (≥40, <40 years) and Clinical Activity Score (CAS) (≥4, <4), and comparison with clinical outcomes including CAS, Hertel exophthalmometry, Gorman diplopia score, and extraocular motility. RESULTS: Forty-eight orbits of 24 patients (16 female, mean age 57.9 years) were included. There was a significant reduction in the total EOM to orbit CSA ratio ( p < 0.01) and for each individual rectus muscle to orbit CSA ratio ( p < 0.01 for all groups). Total EOM to orbit CSA ratios were reduced for 21 patients (87.5%); this was statistically significant in 13 patients (54.2%). There was significant improvement in CAS, proptosis, diplopia, and EOM motility ( p < 0.01 for all categories). There was a significant correlation between reduction of EOM CSA, and reduction of diplopia ( p < 0.01) and EOM motility ( p < 0.01). CONCLUSIONS: EOM CSA is significantly reduced following treatment with teprotumumab, and correlates with clinical findings including improvement in extraocular motility and diplopia.

"Transcanal view" computed tomography reformat: Applications for transcanal endoscopic ear surgery.

PURPOSE: Transcanal endoscopic ear surgery (TEES) is an increasingly used surgical approach for otologic surgeries, but no en face preoperative imaging format currently exists. We aim to assess the utility of a transcanal high resolution computed tomography (HRCT) reformat suitable for TEES preoperative planning. MATERIALS AND METHODS: Preoperative HRCTs of patients with middle ear pathologies (cholesteatoma, otosclerosis, and glomus tympanicum) who underwent TEES were obtained. Axial image series were rotated and reformatted -90 or +90 degrees for left and right ear surgeries, respectively, where additional rotation along the left-right axis was performed to align the transcanal series with the plane of the external auditory canal. Quantitative measurements of middle ear structures were recorded. Consecutive transcanal reformatted sections were then reviewed to identify critical middle ear anatomy and pathology with corresponding TEES cases. RESULTS: The aforementioned methodology was used to create three transcanal view HRCTs. The mean left-right axis degree of rotation was 4.0 ± 2.2 degrees. In the cholesteatoma transcanal HRCT, areas of cholesteatoma involvement in middle ear compartments (e.g. epitympanum) and eroded ossicles were successfully identified in the corresponding case. In the otosclerosis transcanal HRCT, areas for potential otosclerotic involvement were visualized such as the round window as well as a low-hanging facial nerve. In the glomus tympanicum transcanal HRCT, the span of the glomus tympanicum was successfully visualized in addition to a high riding jugular bulb. CONCLUSION: A transcanal HRCT reformat may aid preoperative planning for middle ear pathologies. This novel reformat may help highlight patient-specific anatomy.

Case 292.

History A 24-year-old right-handed woman presented to a neuro-ophthalmology clinic in Massachusetts in the summer with acute binocular diplopia when looking down and to the left, which started about 1 month earlier. Her medical history was notable for Raynaud syndrome, recurrent streptococcal pharyngitis, and an allergy to amoxicillin. Three days prior to developing diplopia, she presented to an outside emergency department due to fever, chills, and back pain. She received ciprofloxacin for presumed urinary tract infection based on urinalysis, which demonstrated few bacteria and was negative for leukocyte esterase, nitrites, and white blood cells. She then presented again to an outside emergency department for diplopia evaluation. Initial MRI and MR angiography of the brain at that time did not demonstrate any relevant findings, and the patient was referred to our department for neuro-ophthalmic evaluation, where she was seen 4 weeks later. Neuro-ophthalmic examination revealed 20/20 visual acuity in both eyes, and a right hypertropia in left gaze, downgaze and right head tilt, with right eye excyclotorsion. There were no ocular signs of myasthenia gravis or thyroid eye disease, nor did the patient report ocular or systemic symptoms. She denied recent travel. High-spatial-resolution MRI of the brain and orbit were performed (Figs 1, 2).

Case 292: Lyme Neuroborreliosis.

History A 24-year-old right-handed woman presented to a neuro-ophthalmology clinic in Massachusetts in the summer with acute binocular diplopia when looking down and to the left, which started about 1 month earlier. Her medical history was notable for Raynaud syndrome, recurrent streptococcal pharyngitis, and an allergy to amoxicillin. Three days prior to developing diplopia, she presented to an outside emergency department due to fever, chills, and back pain. She received ciprofloxacin for presumed urinary tract infection based on urinalysis, which demonstrated few bacteria and was negative for leukocyte esterase, nitrites, and white blood cells. She then presented again to an outside emergency department for diplopia evaluation. Initial MRI and MR angiography of the brain at that time did not demonstrate any relevant findings, and the patient was referred to our department for neuro-ophthalmic evaluation, where she was seen 4 weeks later. Neuro-ophthalmic examination revealed 20/20 visual acuity in both eyes, and a right hypertropia in left gaze, downgaze and right head tilt, with right eye excyclotorsion. There were no ocular signs of myasthenia gravis or thyroid eye disease, nor did the patient report ocular or systemic symptoms. She denied recent travel. High-spatial-resolution MRI of the brain and orbit were performed.

Visual field and orbital computed tomography correlation in dysthyroid optic neuropathy due to thyroid eye disease.

Purpose: The pathogenesis of dysthyroid optic neuropathy (DON) in thyroid eye disease (TED) is thought to be compression of the apical optic nerve by hypertrophied extraocular muscles. We correlated worsening DON to the area occupied by extraocular muscles.Methods: Records of adults with TED DON evaluated from 1/1/2013 to 1/1/2018 were retrospectively reviewed. Each patient's visual field with the worst mean deviation (MD) was selected. Orbit CT scans were reviewed. Reformatted oblique coronal images were created perpendicular to the optic nerve. The cross-sectional area (CSA) of the orbit and each muscle group was measured and expressed as ratios of the CSA of the orbital apex. Univariate and multivariate analysis was performed for predictors of HVF MD.Results: 34 orbits with TED DON were analyzed. On orbital CT, the superior muscle complex occupied 15% of the apex (range 6-26%), inferior 18% (range 6-33%), lateral 10% (range 4-18%), medial 17% (range 8-27%), and all combined 61% (range 28-80%). Increasing total muscle area and superior complex area correlated with worsening MD. In multivariate linear regression, the superior muscle complex remained a significant predictor of MD (p = 0.01) over total muscle area (p = 0.25).Conclusions: Enlargement of extraocular muscles is common in TED, but DON occurs in only 6%. Our findings demonstrate that as DON worsens, as quantified by visual field MD, the superior muscle complex crowds the apex. This is consistent with the typical inferior visual field findings seen in TED DON. Hypertrophy of the superior rectus and levator palpabrae superioris complex may be predictive of worsening DON.

Normalization of ADC does not improve correlation with overall survival in patients with high-grade glioma (HGG).

Mixed reports leave uncertainty about whether normalization of apparent diffusion coefficient (ADC) to a within-subject white matter reference is necessary for assessment of tumor cellularity. We tested whether normalization improves the previously reported correlation of resection margin ADC with 15-month overall survival (OS) in HGG patients. Spin-echo echo-planar DWI was retrieved from 3 T MRI acquired between maximal resection and radiation in 37 adults with new-onset HGG (25 glioblastoma; 12 anaplastic astrocytoma). ADC maps were produced with the FSL DTIFIT tool (Oxford Centre for Functional MRI). 3 neuroradiologists manually selected regions of interest (ROI) in normal appearing white matter (NAWM) and in non-enhancing tumor (NT) < 2 cm from the margin of residual enhancing tumor or resection cavity. Normalized ADC (nADC) was computed as the ratio of absolute NT ADC to NAWM ADC. Reproducibility of nADC and absolute ADC among the readers' ROI was assessed using intra-class correlation coefficient (ICC) and within-subject coefficient of variation (wCV). Correlations of ADC and nADC with OS were compared using receiver operating characteristics (ROC) analysis. A p value 0.05 was considered statistically significant. Both mean ADC and nADC differed significantly between patients subgrouped by 15-month OS (p = 0.0014 and 0.0073 respectively). wCV and ICC among the readers were similar for absolute and normalized ADC. In ROC analysis of correlation with OS, nADC did not perform significantly better than absolute ADC. Normalization does not significantly improve the correlation of absolute ADC with OS in HGG, suggesting that normalization is not necessary for clinical or research ADC analysis in HGG patients.

Transcanal endoscopic infracochlear vestibular neurectomy: A pilot cadaveric study.

PURPOSE: Effective operative approaches for the treatment of refractory vertigo in Meniere's disease are invasive. Vestibular neurectomy can preserve hearing and has been shown to be effective; however, current approaches require an extensive craniotomy. Transcanal endoscopic approaches to the internal auditory canal (IAC) with cochlear preservation have been recently described and may offer a minimally invasive approach to selectively sectioning the distal vestibular nerves while preserving residual hearing. MATERIALS AND METHODS: Three cadaveric human heads were imaged using high resolution computed tomography (CT). Anatomic analysis of preoperative CT scans showed adequate diameters (>3 mm) of the infracochlear surgical corridor for access to the IAC. A transcanal endoscopic approach was attempted to section the vestibular nerve. Post-operative CT scans were assessed to define the operative tract, determine cochlear preservation and assess cochlear and facial nerve preservation. RESULTS: Transcanal endoscopic approach was successfully performed (n = 3) using 3 mm-diameter, 14 cm-length 0°, 30°, and 45° endoscopes and microsurgical drills. In all cases the tympanomeatal flap and ossicular chain remained intact. Internal auditory canalotomy was performed using angled instruments and confirmed in real time via lateral skull base navigation. The vestibular nerves were readily identified and sectioned with preservation of the facial and cochlear nerves. Post-procedure CT showed no violation of the cochlea. CONCLUSION: A transcanal, infracochlear approach to the IAC may permit a minimally invasive approach to distal vestibular neurectomy in cadavers with appropriate anatomy.

Association of Ear Anomalies and Hearing Loss Among Children With 22q11.2 Deletion Syndrome.

OBJECTIVE: To identify inner and middle ear anomalies in children with 22q11.2 deletion syndrome (22q11DS) and determine associations with hearing thresholds. STUDY DESIGN: Retrospective study. SETTING: Two tertiary care academic centers. METHODS: Children presenting with 22q11DS between 2010 and 2020 were included. Temporal bone imaging with computed tomography or magnetic resonance imaging was reviewed by 2 neuroradiologists. RESULTS: Twenty-two patients (12 female, 10 male) were identified. Forty-four ears were evaluated on imaging. There were 15 (34%) ears with abnormal semicircular canals, 14 (32%) with abnormal vestibules, 8 (18%) with abnormal ossicles, 6 (14%) with enlarged vestibular aqueducts, 4 (9.1%) with abnormal facial nerve canals, and 4 (9.1%) with cochlear anomalies. There were 25 ears with imaging and audiometric data. The median pure tone average (PTA) for ears with any structural abnormality was 41.0 dB, as compared with 28.5 dB for ears without any structural abnormality (P = .21). Of 23 ears with normal imaging, 6 (26%) had hearing loss in comparison with 13 (62%) of 21 ears with abnormalities (P = .02). Total number of anomalies per ear was positively correlated with PTA (Pearson correlation coefficient, R = 0.479, P = .01). PTA was significantly higher in patients with facial nerve canal anomalies (P = .002), vestibular aqueduct anomalies (P = .05), and vestibule anomalies (P = .02). CONCLUSIONS: Semicircular canal, ossicular, vestibular aqueduct, and vestibular anomalies were detected in children with 22q11DS, especially in the setting of hearing loss. Careful evaluation of anatomic anomalies is needed prior to surgical intervention in these patients.

Anatomy of the Orbit.

Each orbit is a complex structure housing the globe, multiple cranial nerves, muscles, vascular structures, which support the visual sense. Many of these structures have been delineated in careful detail by anatomists but remain beyond the resolution of conventional imaging techniques. With the advances of higher resolution MR, surface coil usage, and thinner section computed tomographic images, the ability to resolve these small structures continues to improve, allowing radiologists to provide more detailed anatomic descriptions for preoperative and pretreatment planning.

Pediatric Single-Sided Deafness: A Review of Prevalence, Radiologic Findings, and Cochlear Implant Candidacy.

OBJECTIVE: To characterize the prevalence, imaging characteristics, and cochlear implant candidacy of pediatric patients with single-sided deafness (SSD). METHODS: An audiometric database of patients evaluated at a large tertiary academic medical center was retrospectively queried to identify pediatric patients (<18 years old) with SSD, defined as severe to profound sensorineural hearing loss in one ear and normal hearing in the other. Medical records of identified patients were reviewed to characterize the prevalence, etiology, and cochlear implant candidacy of pediatric patients with SSD. RESULTS: We reviewed audiometric data obtained from 1993 to 2018 for 52,878 children at our institution. 191 (0.36%) had the diagnosis of SSD. Cochlear nerve deficiency (either hypoplasia or aplasia) diagnosed on MRI and/or CT was the most common etiology of SSD and was present in 22 of 88 (25%) pediatric SSD patients with available imaging data. 70 of 106 (66%) pediatric SSD patients with available imaging had anatomy amenable to cochlear implantation. CONCLUSIONS: Pediatric SSD is a rare condition and the most common etiology based on radiology is cochlear nerve deficiency. High resolution imaging of the temporal bone is essential to determine cochlear nerve morphology prior to consideration of cochlear implantation.

Clinical Perineural Invasion and Immunotherapy for Head and Neck Cutaneous Squamous Cell Carcinoma.

OBJECTIVES/HYPOTHESIS: To describe outcomes of advanced head and neck cutaneous squamous cell carcinoma (cSCC) with clinical perineural invasion (cPNI) treated with immune checkpoint inhibitor (ICI) therapy, and to describe post-treatment radiographic findings in the context of clinical response to treatment using a new grading system. STUDY DESIGN: Retrospective chart review. METHODS: Retrospective chart review was performed for 11 patients treated with ICI for head and neck cSCC with cPNI of large named nerves. The primary outcome was response to treatment as defined by radiographic and clinical evidence. Clinical responses were defined as improvement in symptoms of neuropathic pain, hypoesthesia, nerve weakness, or decrease in visible tumor. Imaging studies were graded based on a new classification system for perineural invasion and reviewed by two neuroradiologists since RECISTv1.1 is inadequate to adjudicate response in these patients. RESULTS: Nine (82%) patients had radiographic perineural disease control on ICI. Eight patients had improved radiographic perineural disease and one had stable disease. Of these, complete resolution of radiographic evidence of perineural disease was seen in only one patient. Seven (64%) patients had clinical responses, with either improved or stable radiographic disease. CONCLUSIONS: ICI therapy is a viable treatment option for head and neck cSCC with cPNI. Radiographic and clinical evidence of response correlate well, with improvement in neuropathic pain being the most sensitive clinical marker of response. Even with favorable findings on repeat imaging and stable clinical course, complete resolution of perineural thickening and enhancement is rare. A grading system for classifying changes in perineural disease over time is proposed. LEVEL OF EVIDENCE: 4 Laryngoscope, 132:1213-1218, 2022.

A Subset of Intracanalicular Vestibular Schwannomas Demonstrates Minimal Growth Over a 10-Year Period.

OBJECTIVE: Vestibular schwannomas (VS) commonly undergo magnetic resonance imaging (MRI) surveillance, but long-term data to support the ideal frequency is limited. Herein, we aim to investigate intracanalicular VS growth predictors and long-term growth rates (GR). STUDY DESIGN: Retrospective chart review. SETTING: Two tertiary care centers. PATIENTS: Sporadic intracanalicular VS with initial conservative management and at least two sequential MRIs. INTERVENTION: Serial MRI. MAIN OUTCOME MEASURES: VS were categorized by baseline internal auditory canal tertile sublocalization (fundus, midpoint, porus) and size (≤100, 100-200, >200 mm3). Throughout follow-up, volumetric GR (mm3/yr) were determined (baseline-3 yrs, 3-5 yrs, 5-10 yrs) and treatment rates were assessed. RESULTS: Ninety-nine intracanalicular VS were identified (mean follow-up of 6.1 ±â€Š4.5 yrs). Mean GR before 5-year follow-up were comparable for baseline tertile involvement and size. After 5-year follow-up, mean GR of VS involving the fundus at baseline were lower than those involving the midpoint and fundus (6.17 ±â€Š21.16 and 119.74 ±â€Š117.57 mm3/yr, respectively; p = 0.034). Mean GR of VS with less than or equal to 100 mm3 at baseline (-7.29 ±â€Š25.44 mm3/yr) were lower than those with 100 to 200 mm3 (86.55 ±â€Š103.99 mm3/yr; p = 0.011) and more than 200 mm3 (45.70 ±â€Š35.71 mm3/yr; p = 0.031). Vestibular schwannomas involving the midpoint and fundus had greater treatment rates compared with VS involving only the fundus (p < 0.001). CONCLUSIONS: Baseline tertile involvement and size may predict long-term intracanalicular VS growth where fundal tumors or those less than or equal to 100 mm3 exhibit little long-term growth. Extending surveillance after 5-year follow-up may be reasonable for fundal VS.

Otopathologic and Computed Tomography Correlation of Internal Auditory Canal Diverticula in Otosclerosis.

INTRODUCTION: Internal auditory canal (IAC) diverticula, also known as IAC cavitary lesions or anterior cupping of the IAC, observed in otopathologic specimens and high-resolution computed tomography (CT) scans of the temporal bone are thought to be related to otosclerosis. Herein, we examined the usefulness of CT scans in identifying diverticula and determined whether IAC diverticula are associated with otosclerosis on otopathology. METHODS: One hundred five consecutive specimens were identified from the National Temporal Bone Hearing and Balance Pathology Resource Registry. Inclusion criteria included the availability of histologic slides and postmortem specimen CT scans. Exclusion criteria included cases with severe postmortem changes or lesions causing bony destruction of the IAC. RESULTS: Ninety-seven specimens met criteria for study. Of these, 42% of the specimens were from male patients, and the average age of death was 77 years (SD = 18 yr). IAC diverticula were found in 48 specimens, of which 46% were identified in the CT scans. The mean area of the IAC diverticula was 0.34 mm 2 . The sensitivity and specificity of detecting IAC diverticula based on CT were 77% and 63%, respectively. Overall, 27% of specimens had otosclerosis. Histologic IAC diverticula were more common in specimens with otosclerosis than those without (37.5% versus 16%; p = 0.019). Cases with otosclerosis had a greater mean histologic diverticula area compared with nonotosclerosis cases (0.69 mm 2 versus 0.14 mm 2 ; p = 0.001). CONCLUSION: IAC diverticula are commonly found in otopathologic specimens with varied etiologies, but larger diverticula are more likely to be associated with otosclerosis. The sensitivity and specificity of CT scans to detect IAC diverticula are limited.

Motion degradation in optic nerve MRI: A randomized intraindividual comparison study of eye states.

PURPOSE: MRI is a powerful tool for optic nerve assessment, but image quality can be degraded by artifacts related to ocular motion. The purpose of this investigation was to evaluate the effect of undergoing MRI with eyes open versus closed on the degree of motion degradation affecting the optic nerves. METHOD: Patients undergoing 3 Tesla orbital MRI were randomized to undergo the coronal STIR sequence with eyes open and focused on a standardized fixation point, blinking as needed, or with eyes closed. The sequence was then performed again with the other instruction set. Two neuroradiologists rated the intraorbital optic nerves for motion artifact on a 5-point scale (higher numbers reflecting greater motion artifact) in 2 locations of each nerve. Differences were evaluated by the clustered Wilcoxon signed rank test. RESULTS: Seventy-seven orbits were included. Interrater reliability was high (weighted kappa = 0.78). The anterior intraorbital optic nerves were rated with less motion artifact when eyes were open and focused during acquisition than when closed (p = 0.006), but this was not the case for the posterior intraorbital optic nerve (p = 0.69). For example, at the anterior intraorbital optic nerve, motion artifact of mean grade better than 2 was seen in 60% of eyes-open vs. 32% of eyes-closed acquisitions, while mean grade 4 or worse was seen in 4% of eyes-open vs. 12% of eyes-closed acquisitions. CONCLUSION: Undergoing orbital MRI with eyes open and focused rather than closed reduces motion artifact at the anterior intraorbital segment of the optic nerve.

Transcanal Computed Tomography Views for Transcanal Endoscopic Lateral Skull Base Surgery: Pilot Cadaveric Study.

Objective Transcanal endoscopic operative approaches provide for a minimally invasive surgical portal to the lateral skull base. Traditional preoperative imaging evaluation involves computed tomography (CT) acquisition in the axial and coronal planes that are not optimized for the transcanal surgical corridor. Herein, we describe a novel CT-based "transcanal view" for preoperative surgical planning and intraoperative navigation. Study Design Present study is a cadaveric imaging study. Methods Cadaveric temporal bones ( n = 6) from three specimens underwent high-resolution CT (0.625 mm slice thickness). Using three-dimensional (3D) Slicer 4.8, reformatted "transcanal" views in the plane of the external auditory canal (EAC) were created. Axial and coronal reformats were used to compare and measure distances between anatomic structures in the plane of the EAC. Results The degree of oblique tilt for transcanal CT reformats was 6.67 ± 1.78 degrees to align the EAC in axial and coronal planes. Anticipated critical landmarks were identified easily using the transcanal view. Mean values were 8.68 ± 0.38 mm for annulus diameter, 9.5 ± 0.93 mm for isthmus diameter, 10.27 ± 0.73 mm for distance between annulus and isthmus, 2.95 ± 0.13 mm for distance between annulus and stapes capitulum, 5.12 ± 0.35 mm for distance between annulus and mastoid facial nerve, and 19.54 ± 1.22 mm for EAC length. Conclusion This study is the first to illustrate a novel "transcanal" CT sequence intended for endoscopic lateral skull base surgery. Future studies may address how incorporation of a transcanal CT reformat may influence surgical decision making.

Three-dimensional (3D) Printed Vestibular Schwannoma for Facial Nerve Tractography Validation.

OBJECTIVES: Predicting the course of cranial nerve (CN) VII in the cerebellopontine angle (CPA) on preoperative imaging for vestibular schwannoma (VS) may help guide surgical resection and reduce complications. Diffusion MRI based tractography has been used to identify cranial nerve trajectory, but intraoperative validation of this novel approach is challenging. Currently, validation is based on operative report descriptions of the course of cranial nerves, but yields a simplified picture of the three-dimensional (3D) course of CN VII. In this study, we investigate the accuracy of tractography with detailed patient-specific 3D-printed VS tumors. DESIGN: Retrospective case review. SETTING: Tertiary referral center. PARTICIPANTS: Twenty adult VS surgical candidates. MAIN OUTCOME MEASURES: We compared tractography with intraoperative 3D course of CN VII. The surgeons were blinded to tractography and drew the intraoperative course of the CN VII on a patient specific 3D-printed tumor model for detailed comparison with tractography. RESULTS: Of 20 patients, one was excluded due to subtotal removal and inability to assess CN VII course. In the remaining 19 patients, 84% (16/19) tractography was successful. In 94% of tumors with tractography (15/16), the intraoperative description of CN VII course matched the tractography finding. The maximum distance, however, between tractography and intraoperative course of CN VII was 3.7 mm ±â€Š4.2 mm. CONCLUSION: This study presents a novel approach to CN VII tractography validation in VS. Although descriptions of CN VII intraoperatively match tractography, caution is warranted as quantitative measures suggest a clinically significant distance between tractography and CN VII course.

Temporal bone histopathology: Superior semicircular canal dehiscence.

OBJECTIVES: To present a histopathological case of a 91-year-old woman who was diagnosed with superior semicircular canal dehiscence postmortem. METHODS: The patient was a registered donor with the National Temporal Bone Donor Program at the NIDCD National Temporal Bone, Hearing and Balance Pathology Resource Registry. Computed tomography imaging was performed on each temporal bone. The temporal bones were decalcified with ethylenediaminetetracetate and embedded in celloidin, and tissue sections were stained with hematoxylin and eosin. Horizontal sections were taken through the left temporal bone, and vertical sections were taken through the right temporal bone. RESULTS: Histopathological sections taken through the right temporal bone demonstrated no bone between the membranous wall of the superior semicircular canal and the middle fossa dura. There was no histopathological evidence of superior semicircular canal dehiscence in the left temporal bone; however, a small dehiscence would not be identified on horizontal sections. Microcavitations were observed in the common crus of the left temporal bone. CONCLUSION: This reports describes the case of a woman who was diagnosed with superior semicircular canal dehiscence postmortem. The presence of microcavitations in the temporal bone is consistent with osteoclastic activity, which may play a role in the development of superior canal dehiscence.

The Cochlear Cleft: CT Correlation With Histopathology.

OBJECTIVE: To show the histologic correlate of the cochlear cleft, a small low density focus just anterior to the oval window seen on computed tomography (CT) in three temporal bone specimens. PATIENTS: Three temporal bone specimens donated to the National Temporal Bone Registry from patients aged 34 weeks gestation, 42 years, and 89 years with cochlear clefts seen on CT were studied. INTERVENTION: Review and comparison of postmortem high-resolution CT and temporal bone histopathology MAIN OUTCOME MEASURE:: Correlation of CT findings with temporal bone histopathology. RESULTS: The cochlear cleft visible on CT as a pericochlear lucency anterior to the oval window corresponds to fatty marrow in areas of incomplete endochondral ossification of the otic capsule. The cochlear cleft is distinct from the fissula ante fenestram and can be present in adults. CONCLUSION: In these three cases, the cochlear cleft represents an area of fatty marrow from incomplete ossification of the otic capsule and can be present in adults. Care should be taken when interpreting temporal bone CT to avoid mistaking the cochlear cleft for true pathology (otosclerosis) of the temporal bone.