Development of ossification in the vertical semicircular canals: tomographic study.

PURPOSE: To describe the ontogeny of vertical semicircular canals using computed tomography. MATERIALS AND METHODS: We have studied 39 human fetuses aged between 17 and 38 weeks of development through multi-helicoidal CT. RESULTS: The first signs of ossification in the semicircular canals, superior and posterior, are from 19 weeks of development, through two primary ossification centers in each canal, which will take part in the formation of the outer cover oriented towards the middle and posterior brain fossae, respectively. In this process it must be added the intervention of the common branch. Internal bone covers are formed by ossification of the fossa subarcuata in the superior semicircular canal, and from the compact center of the labyrinthine capsule into the posterior canal. The tomographic study has allowed us to demonstrate how ossification follows a variable rate, establishing a period between 21 and 26 weeks where there are completely closed canals with others still open to the brain fossae. CONCLUSIONS: The tomographic study of the semicircular canals has enabled us to establish a critical period in its ossification that could explain the etiology of the congenital-type dehiscence.

Sinostosis cervical asociada a síndromes de Down y de Schneider. Implicaciones clínicas y médico-legales a propósito de un caso autópsico / Cervical synostosis associated with Down's syndrome and Schneider syndrome. Clinical and medico-legal implications of an autopsy case

Con ocasión de un caso de asociación entre síndrome de Down y sinostosis vertebral congénita que sufrió lesión medular traumática, se revisa la asociación de estos cuadros y sus implicaciones clínicas y forenses. La literatura no ha comunicado hasta ahora una asociación prevalente entre síndrome de Down y sinostosis cervicales. Ambos cuadros por separado propenden a la mielopatía cervical, bien de manera degenerativa, bien traumática. En consecuencia, la asociación de ambos debe verse como un factor de riesgo de daño medular o de manera espontánea o, sobre todo, después de traumatismos. En estos casos, la exploración radiológica debe ser exhaustiva incluyendo RMN ya que pueden existir lesiones medulares incluso ante traumatismos mínimos. En caso de fallecimiento, la autopsia medular es obligada ya que puede revelar lesiones subclínicas, clarificar la naturaleza y extensión de las lesiones medulares y esqueléticas, así como ayudar a establecer una mejor correlación anatomoclínica

This paper reviews the association of clinical symptoms and their clinical and forensic implications in a patient with Down's syndrome and congenital cervical synostosis who experienced a traumatic spinal cord injury. To date, no prevalent association between Down's syndrome and cervical synostosis has been reported in the literature. Given that both entities are prone to cause degenerative or traumatic cervical myelopathy, the combination of both conditions must be seen as a risk factor for spontaneous, and particularly traumatic, spinal cord damage. In these cases, radiological examination must be exhaustive, including MRI, given the possibility of spinal cord injury even after minimal trauma. In the event of death, spinal cord autopsy is mandatory as it may reveal subclinical lesions, clarify the nature and extension of the spinal cord and skeletal injuries and help to establish an improved anatomo-clinical correlation

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.

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.

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.

Defecto de cobertura del canal semicircular superior y su implicación clínica / Defect of the bony roof in the superior semicircular canal and its clinical implications

Introducción y objetivo: En la actualidad se desconoce la etiología del síndrome de dehiscencia del canal semicircular superior. Nuestro objetivo es analizar y discutir las distintas hipótesis sobre el origen de dicha patología. Métodos: En un estudio sobre 295 temporales se describe desde el punto de vista anatómico y radiológico un caso de una alteración parcial de la cobertura ósea del canal semicircular superior derecho y se compara con el temporal del otro lado. Resultados: Macroscópicamente el canal semicircular superior exhibe un deterioro de su cubierta ósea, constituida exclusivamente por su capa más interna o endostal que separa el canal del conducto semicircular superior. La reconstrucción en el plano Pöschl demuestra que aunque la cubierta está íntegra, su grosor disminuye a lo largo de la curvatura del canal hasta el defecto (0,6 a 0,3 mm).Conclusión: La presencia de defectos parciales en la cobertura ósea del canal semicircular superior con ausencia de sus capas externa y media, sumado a su menor grosor, hacen susceptible al canal para sufrir un segundo evento que podría causar su rotura pudiéndose convertir en una dehiscencia (AU)

Introduction and objective: The aetiology of the superior semicircular canal dehiscence is currently unknown. Our objective was to analyse and discuss different hypotheses about the origin of this pathology. Methods: In this study performed on 295 temporal bones, one case of partial alteration of the bony roof in the right superior semicircular canal was described from the anatomical and radiological points of view, and compared with the temporal bone on the other side. Results: Macroscopically, the superior semicircular canal shows deterioration in the bony roof, which consists exclusively of the inner or endosteal layer that separates the canal from the superior semicircular conduct. The Pöschl plane reconstruction showed a whole bony roof, but its thickness decreased from the canal curvature to the defect (from 0.6 to 0.3 mm). Conclusion: The presence of partial defects in the bony roof of the superior semicircular canal with absence of the external and middle layers, besides its lesser thickness, makes the canal susceptible to suffering a second event. This could produce its fracture and a dehiscence (AU)

[Defect of the bony roof in the superior semicircular canal and its clinical implications]. / Defecto de cobertura del canal semicircular superior y su implicación clínica.

INTRODUCTION AND OBJECTIVE: The aetiology of the superior semicircular canal dehiscence is currently unknown. Our objective was to analyse and discuss different hypotheses about the origin of this pathology. METHODS: In this study performed on 295 temporal bones, one case of partial alteration of the bony roof in the right superior semicircular canal was described from the anatomical and radiological points of view, and compared with the temporal bone on the other side. RESULTS: Macroscopically, the superior semicircular canal shows deterioration in the bony roof, which consists exclusively of the inner or endosteal layer that separates the canal from the superior semicircular conduct. The Pöschl plane reconstruction showed a whole bony roof, but its thickness decreased from the canal curvature to the defect (from 0.6 to 0.3mm). CONCLUSION: The presence of partial defects in the bony roof of the superior semicircular canal with absence of the external and middle layers, besides its lesser thickness, makes the canal susceptible to suffering a second event. This could produce its fracture and a dehiscence.