Three-dimensional reconstruction of the human semicircular canals and measurement of each membranous canal plane defined by Reid's stereotactic coordinates

OBJECTIVES: Equations for estimating the planar relationships of the human semicircular canals were devised by Blanks et al from a dissected bony labyrinth in a human skull. However, a similar study on the membranous semicircular canal planes has never been published. METHODS: In this study, the angle between each membranous canal plane and Reid's stereotactic horizontal plane was measured on serial histologic sections of 7 temporal bones from Japanese adults. We reconstructed the 3 semicircular canals by computer-aided 3-dimensional analysis. The angles between each pair of both bony and membranous canal planes were measured. RESULTS: In the bony labyrinth, the angles between the 2 canal planes of the lateral-anterior, anterior-posterior, and lateral-posterior pairs were 90.51 degrees +/- 2.98 degrees (mean +/- SD), 91.70 degrees +/- 1.85 degrees, and 94.52 degrees +/- 3.32 degrees, respectively. The angles between the 2 membranous canal planes of the lateral-anterior, anterior-posterior, and lateral-posterior pairs were 90.05 degrees +/- 4.74 degrees, 91.03 degrees +/- 2.93 degrees, and 91.92 degrees +/- 5.22 degrees, respectively. CONCLUSIONS: The data from our study of the membranous labyrinth showed that the angles between each canal plane and the others were much closer to 90 degrees than was found by Blanks et al for the bony labyrinth.     

经岩骨入路手术中迷路保护的显微解剖学基础

目的 为经岩骨入路手术中保护迷路提供显微解剖学资料。方法 模拟幕上下联合经岩骨入路的手术操作,在手术显微镜下对１０具（２０侧）福尔马林固定的成人带颈头颅标本进行解剖,并观测骨迷路及其与重要结构间的解剖关系。结果 骨迷路为一块包绕膜迷路的质地致密、色泽亮丽的骨质,并构成乳突气房的内侧边界。磨削骨半规管透过菲薄的骨质显示暗蓝色的膜半规管即为“蓝线”。测量骨迷路与周围结构的距离有较大的个体差异,其中后半     

Geometry of the semicircular canals of the chinchilla (Chinchilla laniger)

The orientations of the semicircular canals determines the response of the canals to head rotations and, in turn, the brain's ability to interpret those motions. The geometry of chinchillas' semicircular canals has never been reported. Volumetric representations of three chinchilla skulls were generated using a microCT scanner. The centroids of each semicircular canal lumen were identified as they passed through the image slices and were regressed to a plane. Unit vectors normal to the plane representing canal orientations were used to calculate angles between canal pairs. Pitch and roll maneuvers required to bring any canal into the horizontal plane for physiologic investigation were calculated. The semicircular canals of the chinchilla were found to be relatively planar. The horizontal canal was found to be oriented 55.0 degrees anteriorly upward. Pairs of ipsilateral chinchilla canals were not orthogonal and contralateral synergistic pairs were not parallel. Despite this arrangement, the canal plane unit normal vectors were organized to respond with approximately equal overall sensitivity to rotations in any direction. The non-orthogonal chinchilla labyrinth may provide an opportunity to determine whether the frame of reference used by the central vestibular and oculomotor system is based on directions of afferent maximum sensitivity or prime directions.     

Corrosion casts of the temporal bone

This paper compares the size of the bony labyrinth in infants to that in adults. Fusible metal was injected in dried temporal bones and after the overlying bone was removed by dissolving in weak acid, the semicircular canals and cochlea were measured and compared. A summary of the method of preparation is also included.     

Quantitative study of the vestibular sensory epithelium in cochleosaccular dysplasia.

BACKGROUND: Cochleosaccular dysplasia is the most common pathologic finding seen in children with profound congenital sensorineural hearing loss. There has been no quantitative study on the peripheral vestibular system in cochleosaccular dysplasia. OBJECTIVE: To investigate quantitatively the extent of pathologic changes of the vestibular sensory epithelium in cochleosaccular dysplasia. SUBJECTS AND METHODS: Thirteen temporal bones with congenital deafness from 10 individuals were selected for this study from the temporal bone collection of University of Minnesota that showed suitable pathologic findings for the histopathologic criteria of cochleosaccular dysplasia. Age-matched normal control temporal bones were also selected. The vestibular hair cells including types I and II hair cells were counted separately in the saccular macula, utricular macula, and three cristae of the semicircular canals using Nomarski microscopy. RESULTS: The hair cell densities of types I and II hair cells in the macula of the saccule in cochleosaccular dysplasia were significantly decreased compared with the data of normal subjects. Both types I and II hair cells in the utricular macula and the cristae of the three semicircular canals in cochleosaccular dysplasia were well preserved, and no significant difference was observed between findings of cochleosaccular dysplasia and normal controls in the utricle and the three semicircular canals. CONCLUSIONS: In cases with cochleosaccular dysplasia, the neurosensorial hair cells of the saccule were affected; however, the osseous labyrinth, the membranous utricle, and the semicircular canals were normal. Further studies should be performed to establish the pathogenesis of cochleosaccular dysplasia in humans.     

Planer orientation of the bilateral semicircular canals in dizzy patients

Objective

Recent development of 3-dimensional analysis of eye movement enabled to detect the eye rotation axis, which is used to determine the responsible semicircular canal(s) in dizzy patients. Therefore, the knowledge of anatomical orientation of bilateral semicircular canals is essential, as all 6 canals influence the eye movements.

Subjects and methods

Employing the new head coordinate system suitable for MR imaging, we calculated the angles of semicircular canal planes of both ears in 11 dizzy patients who had normal caloric response in both ears.

Results

The angles between adjacent canal pairs were nearly perpendicular in both ears. The angle between the posterior canal planes and head sagittal plane was 51° and significantly larger the angle between the anterior canal planes and head sagittal plane, which was 35°. The angle between the horizontal canal plane and head sagittal plane was almost orthogonal. Pairs of contralateral synergistic canal planes were not parallel, forming 10° between right and left horizontal canal planes, 17° between right anterior and left posterior canal planes and 19° between the right posterior and left anterior canal planes.

Conclusion

Our measurement of the angles of adjacent canal pairs and the angle between each semicircular canal and head sagittal plane coincided with those of previous reports obtained from CT images and skull specimens. However, the angles between contralateral synergistic canal planes were more parallel than those of previous reports.     

The Age-Related Orientational Changes of Human Semicircular Canals

ObjectivesSome changes are found in the labyrinth anatomy during postnatal development. Although the spatial orientation of semicircular canals was thought to be stable after birth, we investigated the age-related orientational changes of human semicircular canals during development.MethodsWe retrospectively studied the computed tomography (CT) images of both ears of 76 subjects ranged from 1 to 70 years old. They were divided into 4 groups: group A (1–6 years), group B (7–12 years), group C (13–18 years), and group D (>18 years). The anatomical landmarks of the inner ear structures were determined from CT images. Their coordinates were imported into MATLAB software for calculating the semicircular canals orientation, angles between semicircular canal planes and the jugular bulb (JB) position. Differences between age groups were analyzed using multivariate statistics. Relationships between variables were analyzed using Pearson analysis.ResultsThe angle between the anterior semicircular canal plane and the coronal plane, and the angle between the horizontal semicircular canal plane and the coronal plane were smaller in group D than those in group A (P<0.05). The JB position, especially the anteroposterior position of right JB, correlated to the semicircular canals orientation (P<0.05). However, no statistically significant differences in the angles between ipsilateral canal planes among different age groups were found.ConclusionThe semicircular canals had tendencies to tilt anteriorly simultaneously as a whole with age. The JB position correlated to the spatial arrangement of semicircular canals, especially the right JB. Our calculation method helps detect developmental and pathological changes in vestibular anatomy.     

Particulate Matter in the Posterior Semicircular Canal

The pathoetiology of benign paroxysmal positional vertigo (BPPV) is controversial. Particulate matter within the posterior semicircular canal has been identified intraoperatively in patients with BPPV but has also been reported in non-BPPV patients at the time of translabyrinthine surgery (Parnes LS, McClure JA. Free-floating endolymphatic particles: a new operative finding during posterior semicircular canal occlusion. Laryngoscope 1992;102:988-92; Schuknecht HF, Ruby RRF. Cupulolithiasis. Adv Otorhinolaryngol 1973;20:434-43; Kveton JF, Kashgarian M. Particulate matter within the membranous labyrinth: pathologic or normal? Am J Otol 1994;15:173-6). The nature of the particulate matter remains unknown. The purpose of this study was to prospectively examine the posterior semicircular canal of patients with and without a clinical history of BPPV for the presence of particulate matter. Seventy-three patients without BPPV symptoms undergoing labyrinthine surgery (vestibular schwannoma excision or labyrinthectomy) and 26 patients with BPPV undergoing the posterior semicircular canal occlusion procedure were compared. Additionally, 70 archived temporal bones without a history of BPPV were examined microscopically for the presence of particulate matter within the lumen of the membranous labyrinth. No particles were observed intraoperatively in any of the 73 patients without a history of BPPV. Particulate matter was observed in 8 of 26 patients at the time of the posterior semicircular canal occlusion procedure for intractable BPPV. Of the 70 temporal bones examined, 31 did not show significant postmortem changes and also did not demonstrate cupulolithiasis or canalithiasis. Particulate matter from within the membranous posterior semicircular canal was removed from one patient at the time of posterior semicircular canal occlusion for intractable BPPV symptoms and was examined by scanning electron microscopy. The particulate matter appeared morphologically consistent with degenerating otoconia. These data show a statistically significant association between the presence of particles within the posterior semicircular canal in this study and the symptom complex of BPPV.     

Angles between left and right vertical semicircular canals

To clarify anatomical relationships between the left and right vertical semicircular canal (SCC), we measured angles between the left and right posterior SCCs, and angles between left and right anterior SCCs. Subjects were T2 images of axial magnetic resonance imaging (MRI) in 50 patients reporting headaches. The mean angle between the left and right posterior SCC was 92.6 degrees (S.D. = 11.7) and that between the left and right anterior SCC was 76.1 degrees (S.D. = 10.4). These results suggest that angles between the left and right vertical semicircular canals are not always 90 degrees, and interindividual differences in the relationship between canal planes are great, indicating a need for discretion in analyzing peripheral nystagmus.     

The caloric stimulus. Temperature generation within the temporal bone

Temperature measurements were performed on isolated cadaveric temporal bones subjected to caloric irrigation of the external meatus. This was undertaken in an attempt to clarify the pathways of heat transfer involved in thermal stimulation of the temporal bone. On average, the maximum temperature change produced across the lateral semicircular canal was 0.47 degrees C, occurring 74 s after the start of the 30-s irrigation. Temperature changes of approximately 1.5 degrees C were found to occur in the air of the middle ear cleft, indicating significant heat transfer by the process of natural convection. By comparison, removal of the bony ridge joining the external meatus with the inner ear had little effect on the temperature generated across the lateral semicircular canal. It is therefore considered that natural convection within the middle ear cleft plays an important role in caloric stimulation of the vestibular labyrinth. This view is supported by the observation that there is a lack of a direct solid connection between the outer ear and lateral limb of the lateral semicircular canal.     

CT of the temporal bone in the study of the inner ear structures in detection of the causes of neurosensory hypoacusis

Computed tomograms of the inner ear structures (n=175) of 150 patients (age 0-75 years) with unaffected temporal bones were studied in detail. It is shown that polyposition CT of the temporal bone is a non-invasive method of visualization of the osseous labyrinth structures: cochlea, vestibule, semicircular canals, aqueducts of the labyrinth and internal acoustic meatus which are reflected on tomograms in 100% cases irrespective of the patient age. Their age-related features are analysed. CT imaging was made in 65 patients with neurosensory hypoacusis of inherited and acquired genesis. The following causes of neurosensory hypoacusis and deafness were revealed: congenital malformation of the labyrinth of Mondini type, common cavity of the labyrinth, cochlear hypoplasia, dysplasia of the vestibule and semicircular canals, a wide aqueduct of the vestibule, stenosis of the internal acoustic meatus, bulboform enlargement of the inner acoustic meatus, neurinoma (schwannoma) of the hearing nerve, Langerhans-cell histiocytosis with affection of the labyrinth capsule, atypical cholesteatoma. The detected changes in the inner ear structures determine further treatment policy.     

Heat radiation--an essential factor of heat transport in caloric vestibular tests? Current experimental findings]

According to the accepted theory, in vestibular testing the caloric stimulus is transported from the auditory canal to the lateral semicircular canal by heat conduction via the bone. Some findings, however, are not consistent with this concept, e.g. the short latency of the vestibular response, and the fact that removing of the osseous bridge does not stop the transport of heat to the semicircular canal. Physically there are three modes of heat transport: conduction, convection, and radiation. So far, only the first two have been discussed with regard to vestibular calorization, however, they fail to explain the findings mentioned above. We carried out experiments on 10 cadaveric temporal bone specimens in order to evaluate the possible effect of heat radiation. With experimental conditions strictly regulated (specimens kept in climate box, 37 degrees C, saturated humidity, standardized irrigation of the auditory canal with 50 ml of water of 50 degrees C in 15 sec., temperature measured by thermistors at selected points of the specimen), the deviation in repeated experiments was within 0.1 degree C. In normal temporal bones a spreading of heat along the osseous structures was found in accordance with heat conduction via the bone. Then the bony bridge between posterior frame of the tympanic membrane and the lateral canal was removed along with the tegmen tympani, leaving the auditory canal and labyrinth connected only by a small anterior-inferior strut. The rise of temperature in the lateral canal, however, was not delayed and reduced, as expected, but faster and greater than in the original situation. If, now, a reflecting shield was inserted in the cleft between tympanic membrane and labyrinth the heat transfer was dramatically reduced. A similar effect could be achieved in the intact middle ear by a shield or by filling the cavity with gel. Convection as means of heat transport could be excluded. The experiments show that heat transport in the vestibular calorization is a complex process, which besides heat conduction involves radiation as an essential factor. This explains a number of experimental and clinical findings that, so far, had been unclear.     

Conduction of thermal stimuli in the human temporal bone

Temperature changes at different locations in the labyrinth were measured in human temporal bone preparations after syringing with water. In order to simulate physiological conditions, the preparations were placed in a water bath at 37 degrees C. The maximum temperature changes in the horizontal semicircular canal after syringing with temperatures symmetrical to body temperature (44 degrees or 30 degrees C) were found to be clearly asymmetrical (with mean values of 0.6 and -0.3K). From measurements in the external auditory meatus, findings showed that the reference temperature was 34 degrees C in front of the tympanic membrane, which explains the asymmetry recorded. Measurements at different locations showed that the temperature first changes in the regions of the ampullae of the horizontal and the superior semicircular canals. In the vestibule the onset and decay of the temperature change is delayed. The time courses of the temperature difference between locations demonstrate that the temperature difference across the horizontal semicircular canal, which would be responsible for any convective effect in the endolymph, is of shorter duration than the absolute temperature change, which would be responsible for any temperature-mediated volume changes.     

Imaging of ancient Egyptian mummies’ temporal bones with digital volume tomography

The radiographic imaging of ancient Egyptian mummies has always been of great interest. Computed tomography is the method of choice to demonstrate bony pathologies with high quality. As digital volume tomography (DVT) is an extension of panoramic tomography with a very high resolution, its qualities were evaluated by examination of temporal bones of Egyptian mummy skulls. Ten Egyptian mummy skulls from the Zoological Collection Marburg, estimated 1,700–5,000?years of age, from Abydos, Philae, Theben-West and Sakkarah, were examined by DVT (3D Accuitomo, Morita, Japan). Through a rotation 360° of the X-ray source around the region of interest, a cylinder of 3?×?4?cm was captured as a three-dimensional volume. The gained data were analyzed with the help of special software on a PC. The angles of the axial, coronal and sagittal sections were arbitrarily changed to represent single structures with high resolution of 0.125?mm to analyze specific anatomical structures. In all skulls, conditions of the temporal bone and its anatomical structures were evaluated and normal as well as pathological findings evaluated in detail. The analysis of special landmarks such as the ossicular chain, cochlea, external, and internal auditory canal, facial nerve canal, and semicircular canals showed an intact ossicular chain in six temporal bones, while only isolated and dislocated ossicles were found in eight temporal bones. Besides one dehiscence of the superior semicircular canal in one temporal bone which might have led to vertigo and deafness at lifetime, all other findings were normal. Fragments of foreign bodies additionally found in the labyrinth, external ear canal and intracranially were attributed to postmortem damage. Digital volume tomography extends the imaging possibilities of CT for paleoradiological evaluation of temporal bones. With its high resolution, geometric accuracy, reconstruction capabilities, rapidness, and comparably low costs, even small bony pathologies are precisely demonstrated in a limited area. Investigations of larger numbers of specimen might reveal further details of ancient history for further interdisciplinary investigation of anthropologists, Egyptiologists, otolaryngologists, and radiologists.     

Correlation of high-resolution computed tomography and gross anatomic sections of the temporal bone: II. Vestibular apparatus

High-resolution computed tomography (CT) of isolated temporal bones was performed in the transaxial, coronal, and sagittal planes at 1.5-mm intervals. The temporal bones were then sectioned at 2.0-mm intervals in planes parallel to the CT scans. The structures making up the vestibular apparatus were identified, and the planes in which each is best visualized were selected for the illustrations. The vestibule, oval window, tympanic cavity, and tympanic portion of the facial nerve are best seen in the transaxial and coronal planes; the arch of the superior semicircular canal in the transaxial plane and its limbs in the coronal plane; the arch of the posterior semicircular canal in the coronal and sagittal planes and its limbs in the transaxial plane; and the common crus in the sagittal plane. The horseshoe-shaped lateral semicircular canal is displayed in the transaxial plane, and the relationship of its lateral limb to the tympanic segment of the facial nerve is best demonstrated in the sagittal plane. The ampullae of all three canals can be appreciated equally well in all three planes.     

New insight into the bony labyrinth: A microcomputed tomography study

Objectives

To visualize and quantify the morphology and mineralization of the developing fetal human bony labyrinth, using 3D-microcomputed tomography (3D-μCT) imaging.

Methods

Eleven right temporal bones from late second and third trimester fetuses were used in this prospective pilot study. After fixation in 10% formalin solution, all samples underwent a microcomputed tomography (μCT) scan, permitting the 3D imaging of the bony labyrinth as well as the quantitative assessment of mineral density, angular distances and dimensions of inner ear components the progression of ossification was precised with histological observations.

Results

Our findings show different rates of growth among the semicircular canals, the vestibular aqueduct, the oval window, the round window and the cochlea. The final sizes of the cochlea and round window are achieved at 23 weeks of gestation, with heights of 5 mm and 2 mm, respectively. The oval window reaches adult size at 35 weeks, whereas the vestibular aqueduct will attain adult size after birth. An increasing degree of torsion of each semicircular canal is observed during fetal development. The superior semicircular canal achieves adult size at 24 weeks, before the posterior and the lateral canals (25 weeks). The time-course of ossification and mineralization observed in structures and confirmed by histology.

Conclusions

During this developmental period poorly studied until now, our findings suggest that each part of the bony labyrinth follows distinct growth and ossification kinetics trajectories, some of these reaching their adult size only after birth.     

Transport of heat in caloric vestibular stimulation. Conduction, convection or radiation?

Experiments in temporal bone specimens were carried out under strictly controlled conditions: temperature (37 degrees C) and humidity kept constant; standardized irrigation of the external ear canal by an automated system (in 15 s, 50 ml of water, 11 degrees C above temperature of specimen), thermistor probes of 0.2 mm diameter placed in different parts of the specimens. In the intact temporal bone such an irrigation causes a rise in temperature with a gradient from the external ear canal across the bony bridge to the lateral semicircular canal as expected with heat conduction. After removal of the bony bridge, which is the main route for heat conduction, the rise in temperature in the lateral semicircular canal is greater and faster than in the intact specimen. This effect again is drastically reduced by placing a reflecting shield between tympanic membrane and labyrinth. In the intact middle ear inserting a reflecting shield or filling the cavity with gel also reduces the heat transfer to the labyrinth, although the bony routes for heat conduction are left untouched. The experiments prove that radiation plays an important part in heat transfer in caloric stimulation.     

Surgical anatomy guidelines for the extended transtemporal approach to the cerebellopontile angle

The extended middle fossa approach to the cerebello-pontine angle was practiced in ten human temporal bones, and the topographical relations of essential structures were studied by exposure of the bony labyrinth. After identification of the greater superficial petrosal nerve and the grey line of the superior semicircular canal landmarks were defined in order to localize the vertical crest (Bill's bar), the ampulla of the superior semicircular canal, the intralabyrinthine part of the facial nerve, the cochlea, and the internal carotid artery. The advantages of the extended middle fossa approach for the preservation of the labyrinthine and cochlear structures together with the safe identification of the facial and cochleo-vestibular nerves are emphasized.     

内耳CT形态学测量方法的探讨

目的 寻找准确、可行的内耳CT形态学测量方法 ,评价不同测量者之间的一致性.方法 对60例外、中、内耳结构正常者的颢骨高分辨力CT图像进行多平面重组(multi-planarreforamtions,MPR),在显示耳蜗最大剖面的MPR图像上测量耳蜗的高度和宽度,在可完整地显示半规管形态的MPR图像上测量各个半规管所环绕的骨岛面积.对两位测量者的结果 进行统计学分析.结果 MPR获得了良好的耳蜗和半规管的影像解剖学显示.配对t检验显示两位测量者的结果 之间差异无统计学意义(P值均>0.05),相关分析表明二者所测结果 之间具有良好的一致性(r值均>0.9).其中耳蜗高度(x±s,下同)为(4.26±0.28)mm,耳蜗宽度为(7.03±0.39)mm,前半规管环绕骨岛面积为(25.49 ±3.84)mm<'2>,后半规管环绕骨岛面积为(20.07 ±2.93)mm<'2>,外半规管环绕骨岛面积为(11.50±1.94)mm<'2>.结论MPR可分别显示内耳各结构的中轴层面,在此基础上的测量具有良好的可重复性,可提供可靠的内耳形态学参数.