Interaction effect of tegmen tympani and superior semicircular canal statuses on the thickness of the roof of the glenoid fossa: a cross-sectional descriptive study.

PURPOSE: Homogeneous development of temporal bone structures is explained by their ontogenic origin; tegmen tympani (TT) and superior semicircular canal (SSC) are related with the glenoid fossa at the temporomandibular joint (TMJ). Therefore, our objective was to determine a possible relationship between TT status (dehiscence or integrity) and the roof of the glenoid fossa (RGF) thickness; SSC status has also been considered. METHODS: This cross-sectional descriptive study was conducted in two tertiary hospitals on 95 patients (109 ears) presenting hypoacusia, facial palsy, vertigo, tinnitus, and other single or combined symptoms, and submitted to a thin-section multidetector-row computed axial tomography (CT) scan. RESULTS: A significant interaction effect of TT × SSC statuses on RGF thickness was found (p = 0.049). A significant difference in RGF thickness was found only for SSC integrity status between TT integrity and TT dehiscence (p = 0.004). The TT dehiscence increased the risk for RGF dehiscence 12.047 times (p = 0.002). CONCLUSIONS: There is an interaction effect of the statuses of both TT and SSC on the thickness of the RGF, instead of an independent effect of the TT status. When RGF dehiscence is found, TT and SSC statuses should be assessed, to discard associated dehiscences.

Influence of Sex and Age on Posterior Semicircular Canal Thickness.

OBJECTIVE: The aim of this study is to determine whether sex and age influence posterior semicircular canal (PSC) thickness. METHODS: This observational study was conducted in 3 tertiary hospitals. The minimal distance between the PSC and the posterior cranial fossa (PSC thickness) was estimated by thin-section multidetector row computed axial tomography (CAT) scan of the temporal bones. Nonselected consecutive patients of all ages (607 temporal bones) were considered. RESULTS: A significant effect was only detected for sex (F = 5.418, p = 0.020); PSC thickness showed a higher mean value in women (mean difference ± SE: 0.224 ± 0.096 mm). A significant and negative r value was detected for males aged >45 years (-0.173, p = 0.026); in that group of patients, PSC thickness decreased as age increased (0.018 ± 0.008 mm/year). For females aged ≤45 years, a significant and positive r value was found (0.198, p = 0.022); in that group, PSC thickness increased as age increased (0.020 ± 0.008 mm/year). CONCLUSIONS: PSC thickness did not significantly evolve with age in young males (≤45 years) but it decreased from age 45 years onwards. On the other hand, PCS thickness increased with age in women until the age of 45 years and it did not significantly change in older females.

Explicación ontogénica para la asociación entre dehiscencia del tegmen tympani y dehiscencia del canal semicircular superior / Ontogenetic explanation for tegmen tympani dehiscence and superior semicircular canal dehiscence association

Objetivos: Analizar la ontogenia del canal semicircular superior y del tegmen tympani y determinar si hay factores embriológicos comunes que expliquen la dehiscencia asociada de ambos. Métodos: Se han analizado 77 series embriológicas humanas de edades comprendidas entre las 6 semanas y recién nacidos. Las preparaciones estaban cortadas en serie y teñidas con la técnica de tricrómico de Martins. Resultados: La prolongación tegmentaria del tegmen tympani y el canal semicircular superior se originan de la misma estructura, la cápsula ótica, y poseen el mismo tipo de osificación endocondral; mientras que la prolongación escamosa del tegmen tympani se desarrolla desde la escama del temporal y su osificación es de tipo directa o intramembranosa. En la osificación de la prolongación tegmentaria colaboran los núcleos de osificación de los canales semicirculares superior, externo y accesorio del tegmen, los cuales por crecimiento se extienden hasta la prolongación tegmentaria, este hecho sumado a que ambas estructuras comparten una capa común de periostio externo podría explicar la coexistencia de falta de cobertura ósea en el tegmen y en el canal. Conclusión: El desarrollo del canal semicircular y tegmen tympani podrían explicar las causas de la asociación de ambas dehiscencias (AU)

Objectives: To analyze the ontogeny of the superior semicircular canal and tegmen tympani and determine if there are common embryological factors explaining both associated dehiscence. Methods: We analyzed 77 human embryological series aged between 6 weeks and newborn. Preparations were serially cut and stained with Masson's trichrome technique. Results: The tegmental prolongation of tegmen tympani and superior semicircular canal originate from the same structure, the otic capsule, and have the same type of endochondral ossification; while the extension of the squamous prolongation of tegmen tympani runs from the temporal squama and ossification is directly of intramembranous type. The nuclei of ossification of the superior and external semicircular canals and accessory of tegmen collaborate in the ossification of the tegmental extension and by growth extend to the tegmental prolongation. This fact plus the fact that both structures share a common layer of external periosteum could explain the coexistence of lack of bone coverage in tegmen and superior semicircular canal. Conclusion: The development of the semicircular canal and tegmen tympani could explain the causes of the association of both dehiscences (AU)

Ontogenetic explanation for tegmen tympani dehiscence and superior semicircular canal dehiscence association. / Explicación ontogénica para la asociación entre dehiscencia del tegmen tympani y dehiscencia del canal semicircular superior.

OBJECTIVES: To analyze the ontogeny of the superior semicircular canal and tegmen tympani and determine if there are common embryological factors explaining both associated dehiscence. METHODS: We analyzed 77 human embryological series aged between 6 weeks and newborn. Preparations were serially cut and stained with Masson's trichrome technique. RESULTS: The tegmental prolongation of tegmen tympani and superior semicircular canal originate from the same structure, the otic capsule, and have the same type of endochondral ossification; while the extension of the squamous prolongation of tegmen tympani runs from the temporal squama and ossification is directly of intramembranous type. The nuclei of ossification of the superior and external semicircular canals and accessory of tegmen collaborate in the ossification of the tegmental extension and by growth extend to the tegmental prolongation. This fact plus the fact that both structures share a common layer of external periosteum could explain the coexistence of lack of bone coverage in tegmen and superior semicircular canal. CONCLUSION: The development of the semicircular canal and tegmen tympani could explain the causes of the association of both dehiscences.

Association Between Tegmen Tympani Status and Superior Semicircular Canal Pattern.

OBJECTIVE: Detecting and quantifying the possible association between tegmen tympani (TT) status and superior semicircular canal (SSC) pattern. DESIGN: Observational study. SETTING: Study conducted in three tertiary Spanish hospitals. PATIENTS: Nonselected consecutive patients of all ages (607 temporal bones). INTERVENTIONS: Thin-section multidetector row computed axial tomography (CAT scan) of the temporal bones. MAIN OUTCOME MEASURE: Thickness of SSC bone coverture adjacent to the middle fossa, and TT status as a dichotomous variable: dehiscence (TTD) or integrity (TTI). RESULTS: The observed SSC patterns were dehiscence (3.79%), papyraceous or thin (11.20%), normal (76.77%), thick (4.94%), and pneumatized (3.29%). The observed TT statuses were TTD (10.87%) and TTI (89.13%). TTD was associated with SSCD and papyraceous patterns, and TTI percentages were higher in normal and thick patterns (χ2 = 11.102; p = 0.001). The TTD probability was estimated as a function of SSC pattern and age by a multivariate binary logistics regression model (χ2 = 45.939; p < 0.001). CONCLUSION: SSC pattern was significantly associated with TT status. Age influenced this association. The risk for TTD increased by 4.1% per each year of increasing age, did not differ significantly for normal and thick patterns, and increased 12 times and 20 times for papyraceous and SSCD patterns, respectively.

Peculiaridades en el desarrollo del canal semicircular superior / Peculiarities in the development of the superior semicircular canal

Objetivos: Realizar un estudio sobre la ontogénesis del canal semicircular superior con el fin de describir sus peculiaridades. Métodos: Para ello se han analizado 76 series embriológicas humanas de edades comprendidas entre los 32 días (6 mm) y recién nacidos. Las preparaciones estaban cortadas en serie y teñidas con la técnica de tricrómico de Martins. Resultados: En el desarrollo del canal semicircular hemos observado una serie de peculiaridades, como: secuencia cronológica definida de su osteogénesis con un ritmo de osificación variable, cada núcleo de osificación interviene en la formación de una de sus cubiertas, el superior de la superficial y el inferior de la profunda; la aparición de una dehiscencia transitoria, y el cierre del canal por hueso de tipo laminar con un grosor mínimo de 0,1 mm. Conclusión: Las peculiaridades en el desarrollo del canal podrían explicar las causas del origen de la dehiscencia patológica del mismo, ya sean congénitas o adquiridas (AU)

Objective: Our objective was to study the ontogeny of the superior semicircular canal in order to describe its peculiarities. Methods: We analyzed 76 series of human embryos aged between 32 days (6 mm) and newborns. The samples were cut serially and stained using Martin's trichrome technique. Results: In semicircular canal development there were a number of peculiarities, such as: a defined chronological sequence of osteogenesis with a variable rate of ossification; the fact that each nucleus of ossification was involved in the formation of one of its covers (the upper in the superficial and the lower in the deep); the appearance of transitory dehiscence; and canal closure by means of bone with laminar pattern, with a minimum thickness of 0.1 mm. Conclusion: The peculiarities in canal development could explain the origin of pathological dehiscence in the canal, whether congenital or acquired (AU)

[Peculiarities in the development of the superior semicircular canal]. / Peculiaridades en el desarrollo del canal semicircular superior.

OBJECTIVE: Our objective was to study the ontogeny of the superior semicircular canal in order to describe its peculiarities. METHODS: We analyzed 76 series of human embryos aged between 32 days (6mm) and newborns. The samples were cut serially and stained using Martin's trichrome technique. RESULTS: In semicircular canal development there were a number of peculiarities, such as: a defined chronological sequence of osteogenesis with a variable rate of ossification; the fact that each nucleus of ossification was involved in the formation of one of its covers (the upper in the superficial and the lower in the deep); the appearance of transitory dehiscence; and canal closure by means of bone with laminar pattern, with a minimum thickness of 0.1mm. CONCLUSION: The peculiarities in canal development could explain the origin of pathological dehiscence in the canal, whether congenital or acquired.

Radiological patterns of the posterior semicircular canal.

OBJECTIVES: The identification and definition of the radiological patterns of the posterior semicircular canal (PSC), with a view to obtain readily applicable conclusions. DESIGN: The parietal morphology of the PSC has been studied by multi-slice helical computed tomography (Philips Brilliance 6). We have determined the distribution of the different types of bone cover of the PSC, taking some previously notified, standardised measurements of normality as reference. RESULTS: 318 patients have been analysed (604 petrous bone) by CT and we have distinguished five different radiological patterns: type or normal, thick, thin, pneumatised and dehiscent. The first three patterns, normal, thick and thin, have in common the existence of a compact bone interposed between PSC and posterior fossa, being in the normal pattern has a thickness of between 0.9 and 2.5 mm (327 cases, 54.13%), in the thick pattern is ≥2.6 mm (99 cases, 16.39%) and in the thin pattern is ≤1.2 mm (158 cases, 26.15%). The fourth pattern, pneumatised, is characterised by having retro labyrinthine cells between PSC and media fossa (19 cases, 3.14%). Finally, a dehiscent pattern was observed in 2 cases (0.3%). CONCLUSION: We describe five different radiological patterns: type or normal, thick, thin, pneumatised and dehiscent. The thin type (<0.5 mm or papyraceous type) and the dehiscent type would be subject to producing pathology, and in some cases the latter could be a consequence of the former.

Influencia de la existencia de una dehiscencia en un canal semicircular en el espesor óseo de los canales contralaterales / Effect of semicircular canal dehiscence on contralateral canal bone thickness

Objetivos: Determinar si la existencia de un canal semicircular superior o posterior dehiscente se asocia con el adelgazamiento de la cubierta ósea en el resto de los canales verticales (superior o posterior). Métodos: Se estudia mediante tomografía computarizada y se compara estadísticamente el espesor de los canales semicirculares superiores y posteriores contralaterales a una dehiscencia. Resultados: Cuando un canal semicircular superior presentaba una dehiscencia, el canal contralateral mostraba un adelgazamiento significativo de su espesor con una media de 0,5mm (DE:0,3mm). No sucede lo mismo con los posteriores que no modifican su grosor de 2,1mm (DE: 1,2mm; p=0,49).Cuando un canal semicircular posterior presentaba dehiscencia no se observó adelgazamiento significativo en los canales semicirculares superiores 1mm (DE:0,4), ni en el posterior contralateral 1,3mm (DE:0,3). Conclusión: La existencia de una dehiscencia del canal semicircular superior se asocia al adelgazamiento del hueso del canal del lado contrario, pero no de los canales semicirculares posteriores. No ocurre lo mismo si la dehiscencia es del canal semicircular posterior, que no altera de manera significativa el espesor del canal del lado contralateral ni en los superiores (AU)

Objectives: Our objective was to determine if the existence of dehiscence in the superior or posterior semicircular canal was associated with the thinning of the bone roof in the rest of the vertical canals (superior or posterior). Methods: The thickness of the superior and posterior semicircular canals contralateral to a dehiscence was studied using computerized tomography and compared statistically. Results: When a superior semicircular canal had a dehiscence, the contralateral canal showed a significant mean decrease in its thickness of 0.5mm (SD: 0.3mm). This was not the case if the dehiscence was in the posterior semicircular canal, where the thickness of 2.1 mm remained unchanged (SD: 1.2mm; P=0.49).When a posterior semicircular canal showed dehiscence, no significant thinning was shown in the superior semicircular (1mm; SD: 0.4) or in the posterior contralateral (1.3mm; SD: 0.3) canals. Conclusion: The existence of a dehiscence in the superior semicircular canal is associated with bone thinning in the canal on the opposite side, but not with the posterior semicircular canal. In contrast, if the dehiscence is in the posterior semicircular canal, contralateral and superior canal thickness is not modified (AU)

Congenital dehiscence in the posterior semicircular canal.

HYPOTHESIS: Posterior semicircular canal dehiscence (PSCD) may be of congenital origin. BACKGROUND: PSCD is characterized by the lack of bone coverage, which results in its lumen being exposed to the meninges of the posterior cranial fossa or to the gulf of the jugular vein. It has an incidence of 0.2%. Its presence has been associated with several well-defined entities, although a congenital origin has not been proven. METHODS: We have analyzed, from a macroscopic, microscopic, and radiologic (computed tomography) viewpoint, the right temporal bone of a 32-week-old human fetus that presented a defect in the bone coverage located in the rear. RESULTS: The macroscopic study showed a solution of continuity in the posterior semicircular canal, with elliptic morphology and smooth edges. This defect was 3.4 mm long with a width that varied between 0.67 mm in its apical portion and 1.42 in the basal portion. The radiologic study (computed tomography) showed the absence of bone coverage of the posterior semicircular canal, which was open to the intracranial space in the posterior fossa. Its histologic study showed good bone coverage of this canal at the expense of compact bone tissue. However, at the medial end, there is a lack of bone coverage, resulting in the lumen of the canal being open to the intracranial space. The bone edges of the defect did not present any osteoclast activity. CONCLUSION: The lack of bone coverage (dehiscence) of the posterior semicircular canal in a 32-week-old fetus suggests a congenital component of bony dehiscences of this canal. Even so, this single finding does not conclusively prove the congenital component, and the dehiscence is a finding that can be part of and not by itself a syndrome.

Effect of semicircular canal dehiscence on contralateral canal bone thickness.

OBJECTIVES: Our objective was to determine if the existence of dehiscence in the superior or posterior semicircular canal was associated with the thinning of the bone roof in the rest of the vertical canals (superior or posterior). METHODS: The thickness of the superior and posterior semicircular canals contralateral to a dehiscence was studied using computerized tomography and compared statistically. RESULTS: When a superior semicircular canal had a dehiscence, the contralateral canal showed a significant mean decrease in its thickness of 0.5mm (SD: 0.3 mm). This was not the case if the dehiscence was in the posterior semicircular canal, where the thickness of 2.1 mm remained unchanged (SD: 1.2 mm; P=.49). When a posterior semicircular canal showed dehiscence, no significant thinning was shown in the superior semicircular (1 mm; SD: 0.4) or in the posterior contralateral (1.3 mm; SD: 0.3) canals. CONCLUSION: The existence of a dehiscence in the superior semicircular canal is associated with bone thinning in the canal on the opposite side, but not with the posterior semicircular canal. In contrast, if the dehiscence is in the posterior semicircular canal, contralateral and superior canal thickness is not modified.

Radiological patterns of the bony roof of the superior semicircular canal.

OBJECTIVES: To study the radiological patterns of the bony roof of the superior semicircular canal with a view for obtaining readily applicable conclusions. DESIGN: 84 patients (163 petrous bones) have been studied by Multi-slice Helical Computed tomography (Philips Brilliance 6). We have determined the distribution of the different types of bone cover of the superior semicircular canal, taking some previously notified, standardised measurements of normality as reference. RESULTS: During the analysis of the roof of the superior semicircular canal, we have distinguished five different types, depending on their thickness and tomodensitometric aspect. Normal pattern in 121 cases (74.2 %), with a thickness of between 0.6 and 1.7 mm, papyraceous pattern or fine thickness ≤0.5 mm that appears in 23 of our cases (14.1 %), thick pattern ≥1.8 mm that we have observed in 11 cases (6.7 %), and pneumatised pattern in 5 cases (3.1 %), which is characterised by having supralabyerinthine cells. Finally, a dehiscent pattern was observed in three cases (1.8 %). CONCLUSION: We describe five patterns of superior semicircular canal roofs: normal, thick, papyraceous, pneumatised and dehiscent. The papyraceous type and the dehiscent type would be subject to producing pathology, and in some cases the latter could be a consequence of the former.

Influence of aging and menopause in the origin of the superior semicircular canal dehiscence.

OBJECTIVE: Determine if aging and menopause, known to be associated with bone resortion, also are associated with superior semicircular canal dehiscence. DESIGN: Observational study. SETTING: Study conducted in 3 tertiary Spanish hospitals. PATIENTS: Nonselected consecutive patients of all ages. INTERVENTIONS: Thin-section multi-detector row computed tomographic scan of the temporal bones. MAIN OUTCOME MEASURE: The minimum thickness of the bone covering the roof of the superior semicircular canal (SSC) measured in each temporal bone. The outcome was studied both as a continuous and as a dichotomous variable: thin (<0.6 mm) and normal (≥ 0.6 mm). RESULTS: Five hundred eighty-two ears of 312 patients were included in the study. Fifty-five percent of the sample were women. Patient's age ranged from 2 to 88 years. A 40-year age difference between ears was associated with a decreased thickness of bone covering the SSC of 0.10 mm, which is 10% of the average thickness of such bone. The thickness of the bone overlying the SSC of subjects younger than 45 years was an average of 1.14 mm (SD, 0.52 mm), whereas that of the subjects older than 45 years was equal to 1.02 mm (SD, 0.45 mm; p = 0.006). The percentage of ears with thin bone coverage of SSC was 7.1% in subjects younger than 45 years and 13.8% in those older than 45 years (p = 0.013). CONCLUSION: Our data support the hypothesis that there is a slight osteopenia of the roof of the superior semicircular canal associated with aging, and this effect seems to be more pronounced in menopausal women.