Foramen tympanicum, or foramen of Huschke: pathologic cases and anatomic CT study.
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BACKGROUND AND PURPOSE: A persistent foramen tympanicum, or foramen of Huschke, is an anatomic variation of the tympanic portion of the temporal bone due to a defect in normal ossification in the first 5 years of life. The foramen is located at the anteroinferior aspect of the external auditory canal (EAC), posteromedial to the temporomandibular joint (TMJ). We sought to define its prevalence, location, and size on high-resolution spiral CT (HRCT). METHODS: We prospectively examined 102 consecutive HRCT studies of the temporal bone (204 ears). HRCT was performed by using 120 kV, 400 mAs, an ultra-high-resolution filter, 0.6-mm section thickness, 0.3-mm section increment, 728 x 728 matrix, and 160-mm field of view. We noted the size and location of the foramen tympanicum relative to the tympanic membrane and calculated its prevalence. Patients with focally decreased tympanic bone thickness of <1 mm at the anteroinferior EAC (between the 3- and 6-o'clock positions) were considered separately. RESULTS: We found a foramen tympanicum was found in six (4.6%) of 130 ears. Mean axial diameter was 4.2 mm, and mean sagittal diameter was 3.6 mm. Focally reduced bone thickness in the same location was found in 45 (35%) ears, with a female preponderance (P = .003). CONCLUSION: HRCT is sensitive for detection of the foramen tympanicum because of its thin sections, high spatial resolution, and multiplanar capabilities. Awareness of this anatomic entity may be useful in evaluating patients with transient otorrhea in whom no otologic cause (e.g., ear infection, TMJ disease) is identified. (+info)
Retinal growth in foveated teleosts: nasotemporal asymmetry keeps the fovea in temporal retina.
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Fish retinas continue to grow throughout life by adding neurons at the margin, with the result that cells born at a peripheral site are steadily displaced toward the center of the enlarging retina. This presents a functional problem for fish with specialized temporal areas such as a fovea--how to reconcile continual growth with the maintenance of a temporal location for the fovea. One possibility is that the retina grows asymmetrically, with most new retina added nasally, relatively little temporally. I have tested this hypothesis by evaluating retinal growth in marine teleosts from 15 families, both foveated and unfoveated. The pattern of growth was revealed by exploiting the fact that each new generation of ganglion cells sends its axons into the optic nerve as a cohort; small grains of the carbocyanine dye 1,1'-dioctadecyl-3,3,3',3'-tetramethyl-indocarbocyanine were applied to various sites in the cross section of the optic nerves of adults, and the retrogradely labeled cell bodies in the retina were visualized in whole-mounts. The labeled cells lay in annuli, each one a generation of ganglion cells. Representatives of seven of the families showed clearly asymmetric growth: the labeled annuli were close together on the temporal side and more distant nasally, the embryonic fissure curved from its ventral origin toward the temporal side, and in six of these families, labeled fibers from temporal retina skirted the fovea. Members of the other eight families, without specialized areas, had more symmetric retinal growth: labeled annuli were equally spaced on all sides, the embryonic fissure was vertical, and there were no skirting fibers. The following hypothesis is supported: the retina grows asymmetrically, and maintains the area for acute vision oriented toward the anterior field. (+info)
Current multiplanar imaging of the stapes.
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PURPOSE: CT analysis of the stapes is difficult in the axial plane (AP), because of its oblique orientation. Oblique axial reformations could provide a more precise analysis of the stapes in normal and pathologic conditions. MATERIALS AND METHODS: CT of the temporal bone was performed in 31 patients. Only the normal side was examined in the AP and oblique axial plane (OAP), in the plane of the stapes superstructure. Conspicuousness of each stapes component was evaluated in both planes by 2 independent readers. Reproducibility between the 2 readers (R1 and R2) and comparison of conspicuousness between the AP and the OAP in the analysis of the stapes crura were evaluated. The normal position of the stapes arch in relationship to the footplate was determined in the OAP by using biometric landmarks. RESULTS: Conspicuousness of the stapes crura was increased by using OAP. The conspicuousness of the anterior crus was enhanced in 38% with the OAP according to R1 (P < .05) and 32% according to R2 (P < .05). The conspicuousness of the posterior crus was enhanced in 35% with the OAP according to R1 (P < .05), but not significantly enhanced in 22% with the OAP according to R2 (P = .095). Analysis of conspicuousness of the stapes crura was reproducible according to the kappa test. A perpendicular line to the footplate intersecting its midportion crosses the stapes head and the long process of the incus in the OAP in normal patients. CONCLUSION: OAP could enhance the CT analysis of the stapes and provide useful biometric landmarks in pathologic conditions. (+info)
CT-demonstrated transcalvarial channels diagnostic of dural arteriovenous fistula.
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MR imaging-evident intraosseous channels associated with the presence of a dural arteriovenous fistula have been described in the literature. We describe these channels in relation to a case of dural arteriovenous fistula seen on CT. The presence of this subtle sign should be sought, and the area reviewed in all CT evaluations of patients with pulsatile tinnitus. (+info)
Three-dimensional CT of Eagle's syndrome.
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This case report presents three-dimensional computed tomography (3D-CT) findings in the diagnosis of Eagle's syndrome that is characterized with an elongated styloid process or a calcified stylohyoid ligament causing craniofacial or cervical pain. We have performed 3D-CT in three patients suspected to have this condition. Coronal images were taken in two patients and axial images in one patient with a spiral CT scanner. 3D-CT images were then produced. The length of the styloid process in the case suspected of right elongated styloid process was 45.6 mm (left styloid process, 37 mm). In the second case suspected of left elongated styloid process, the length of the left styloid process was 41.1 mm (right styloid process, 40.2 mm). In the last case suspected of right elongated styloid process, the length of the right styloid process was 40.6 mm (left styloid process, 38.9 mm). 3D-CT is a valuable diagnostic tool in the diagnosis of Eagle's syndrome because of its ability to facilitate accurate measurement of the length of the styloid process. (+info)
Rare osteodysplasia of the temporal bone.
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Temporal bone osteodysplasia can produce many different symptoms, such as involvement restricted to the temporal bone or impairment of other bones. We consider, in this study two entities that are rare osteodysplasia cases, which are osteopetrosis and Camurati-Engelmann disease, the latter being extremely rare. We present two cases of benign form of osteopetrosis (Albers-Schulenburg's disease), a patient of 11 years old and another one of 48 years old, both male, and a patient of 28 years old, female, with Camurati-Engelmann's disease. The facial palsy was a manifestation in two of the patients. We discuss some aspects about the clinical manifestations, radiological findings, as well as differential diagnostic and therapy in view of the complications of the diseases. (+info)
Microscopic anatomy of the carotid canal and its relations with cochlea and middle ear.
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The knowledge of the relations between the noble and vital structures of temporal bone is still a great challenge for the otologic surgeon. The microscopic anatomic studies of the temporal bone are one of the greatest help to prevent lesions during surgical intervention. AIM: To study the anatomic correlations between the carotid canal and the cochlea, and the occurrence of dehiscence of the carotid canal in the middle ear tympanic cavity. MATERIAL AND METHODS: Microscopic study of 122 human temporal bones. RESULTS: The average distance between the carotid canal and the cochlea were: the shortest distance, 1.05 mm; basal turn, 2.04 mm; middle turn, 2.32 mm; and apical turn, 5.70 mm. The occurrence of dehiscence of the carotid canal inside the tympanic cavity was 35.2%. CONCLUSION: The small distances between the cochlea and carotid canal, and the high incidence of dehiscence in the tympanic cavity remind us that anatomical knowledge of the temporal bone is required for the best qualification of otologists. (+info)
Osteoprotegrin knockout mice demonstrate abnormal remodeling of the otic capsule and progressive hearing loss.
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OBJECTIVES: The otic capsule, when compared with other bones in the body, is unique in that it undergoes no significant remodeling of bone after development. We previously demonstrated that osteoprotegerin (OPG), which inhibits formation and function of osteoclasts, is produced at high levels in the inner ear of normal mice and secreted into the perilymph from where it diffuses into the surrounding otic capsule bone through a lacunocanalicular system. To test our hypothesis that the high level of OPG may be important in the inhibition of otic capsule remodeling, we studied the light microscopic histology of the otic capsule in OPG knockout mice for evidence of abnormal remodeling of bone. We also tested the hearing in OPG knockout mice to determine whether OPG and its influence on surrounding bone is important for auditory function. METHODS: Temporal bone histopathology and pathophysiology were compared in homozygous OPG knockout mice and C57BL/6 (B6) mice, the background strain for the knockouts. Auditory function in age-matched animals from each group was evaluated at approximately 4-week intervals from 8 to 21 weeks using frequency-specific auditory brainstem responses (ABR) and distortion product otoacoustic emissions (DPOAE). After each of the last three evaluations, the cochleae from one mouse of each group were harvested, processed, and examined by light microscopy. RESULTS: Osteoprotegerin knockout mice demonstrated abnormal remodeling of bone within the otic capsule with multiple foci showing osteoclastic bone resorption and formation of new bone. Such changes were not seen in the age-matched B6 controls. The active bone remodeling process in the knockout animals showed many similarities to otosclerosis seen in human temporal bones. Over the time period that we monitored, auditory function was significantly and progressively compromised in the knockout animals relative to B6 controls. At the earliest age of test (8 wk), the loss was apparent as a mild, high-frequency reduction in sensitivity by ABR. In contrast, DPOAE losses in the knockouts were substantial even at 8 weeks, and by 21 weeks, these losses exceeded our equipment limits. Results of ABR testing showed hearing sensitivity changes in the animals of the background strain were confined largely to the high frequencies, whereas OPG knockouts demonstrated substantial low-frequency shifts in addition to those at high frequencies. CONCLUSIONS: The histopathological and pathophysiological findings in OPG knockout mice support the hypothesis that OPG is important in the inhibition of bone remodeling within the otic capsule and the maintenance of normal auditory function. This mouse may provide a valuable animal model of human otosclerosis. (+info)