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.

Genetic Heterogeneity and Core Clinical Features of NOG-Related-Symphalangism Spectrum Disorder.

OBJECTIVES: To better distinguish NOG-related-symphalangism spectrum disorder (NOG-SSD) from chromosomal 17q22 microdeletion syndromes and to inform surgical considerations in stapes surgery for patients with NOG-SSD. BACKGROUND: Mutations in NOG cause a variety of skeletal syndromes that often include conductive hearing loss. Several microdeletions of chromosome 17q22 lead to severe syndromes with clinical characteristics that overlap NOG-SSD. Isolated deletion of NOG has not been described, and therefore the contribution of NOG deletion in these syndromes is unknown. METHODS: Two families with autosomal dominant NOG-SSD exhibited stapes ankylosis, facial dysmorphisms, and skeletal and joint anomalies. In each family, NOG was evaluated by genomic sequencing and candidate mutations confirmed as damaging by in vitro assays. Temporal bone histology of a patient with NOG-SSD was compared with temporal bones of 40 patients diagnosed with otosclerosis. RESULTS: Family 1 harbors a 555 kb chromosomal deletion encompassing only NOG and ANKFN1. Family 2 harbors a missense mutation in NOG leading to absence of noggin protein. The incus-footplate distance of the temporal bone was significantly longer in a patient with NOG-SSD than in patients with otosclerosis. CONCLUSION: The chromosomal microdeletion of family 1 led to a phenotype comparable to that due to a NOG point mutation and much milder than the phenotypes due to other chromosome 17q22 microdeletions. Severe clinical findings in other microdeletion cases are likely due to deletion of genes other than NOG. Based on temporal bone findings, we recommend that surgeons obtain longer stapes prostheses before stapes surgery in individuals with NOG-SSD stapes ankylosis.