Computer-aided three-dimensional reconstruction of the osseous and membranous labyrinths

Summary In order to obtain an adequate knowledge of the stereoscopic anatomy of the temporal bone, it is very useful to make three-dimensional reconstructions of the bone. By using the histological sections of a human temporal bone processed for routine evaluation, we have undertaken computer-aided reconstruction of the osseous and the membranous labyrinths, as well as the inner ear sensory organs. Reconstructions were done either separately or simultaneously. Owing to the semitransparent display function of the computer system, it was possible to observe the reconstructed membranous labyrinth through the simultaneously reconstructed osseous labyrinth, and the sensory organs through the membranous labyrinth. The results were satisfactory for understanding the spatial relationships among these structures. We also attempted computer-aided measurements of the reconstructed sensory organs and calculated the length of the organ of Corti and the angle between the saccular and the utricular maculae.     

Three-dimensional reconstruction and measurement of the human membranous semicircular canal

The planar relationship of the human semicircular canals was determined by Blanks et al. at a series of points measured from the dissected bony labyrinth of the human skull. The relationship of membranous canal planes have not, however, been measured from the human temporal bone. We reconstructed 3 semicircular canals by computer-aided 3-dimensional analysis and measured the angles formed between pairs of 3 osseous and membranous canal planes of temporal bones. Five temporal bones in adults were used for this study. Results indicated angles formed between pairs of ipsi-lateral canal planes of both the bony and membranous labyrinth. Angles formed between the horizontal-anterior, anterior-posterior, and posterior-horizontal canal planes of the bony labyrinth were 89.64 +/- 1.82 (mean +/- SD), 90.95 +/- 1.25, and 94.02 +/- 3.77 degrees. The same angles measured from the membranous labyrinth were 90.12 +/- 2.64, 90.18 +/- 2.75, and 91.48 +/- 6.32 degrees. Differences between the angles formed between bony and membranous canal planes were 2.11, 6.05, and 3.26 degrees in the anterior, horizontal, and posterior canal. Pairs of membranous canal planes were nearly perpendicular without exception, but pairs of osseous canal planes had a larger deviation from 90 degrees. This suggested that membranous canals could successfully be constructed in adequate alignment for canal function in the large perilymphatic space within osseous semicircular canals.     

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.     

高分辨率CT容积重建对内耳畸形的诊断价值

目的：通过高分辨率CT（HRCT）容积重建（VR）对正常内耳形态的观察，探讨其对先天性内耳畸形的诊断价值。方法：对10例（20耳）无耳部疾患者（对照组）和7例（11耳）先天性内耳畸形患者（病变组）行HRCT扫描，利用容积漫游技术对内耳骨迷路重建。对照组观察内耳骨迷路的正常结构，病变组观察内耳畸形情况。结果：正常耳VR图像不但显示了内耳骨迷路的细微结构，而且还反映了各结构之间的关系；病变耳立体显示了畸形部位及程度。11耳患耳中Mondini型7耳次；前庭及半规管畸形3耳次；前庭导水管扩大7耳次，其中6耳次伴随其他畸形；内耳道畸形2耳次且均伴随其他畸形。11耳畸形中9耳HRCT横断面图像和平面重建（MPR）冠状位图像、VR图像均可以清晰地显示畸形的部位和程度，其中VR图像可以直观、立体地显示畸形的空间形态结构；2耳水平半规管短小畸形患者VR图像较断面图像更好地显示了畸形的部位和程度。结论：VR三维重建可以立体显示正常内耳骨迷路的形态，直观显示内耳畸形的程度及病变位置，对内耳畸形的诊断具有重要的辅助价值。     

Symposium: Cochlear implant, 1978—fact or supposition. Traumatic intracochlear electrode implantation

The success of intracochlear electrode implantation hinges on the ability of peripheral auditory neurons to survive long-term interface with an electrode array and prolonged electrical stimulation. Histopathological studies have been conducted on a series of neomycin sulphate otointoxicated cats to assess the long-term effects of electrode implantation on an impaired cochlea (analogous to potential human sensory deaf implant candidates). The results of these studies may be summarized as follows: 1. Long-term electrode implantation can be achieved without significant loss of primary auditory neurons using an electrode array embedded in Silastic which is molded to conform to the basal scala tympani if surgical implantation has not disrupted the basilar membrane or osseous spiral lamina. 2. A fibrous tissue matrix forms around the Silastic, displacing perilymph and effectively sealing the electrode at the round window preventing perilymph fistula. 3. While osteoneogenesis will occur whenever the periosteum of the bony labyrinth is disrupted, the molded Silastic sheathing prevents electrode displacement by small areas of new bone formations. 4. Traumatic electrode insertion, with fracture of the osseous spiral lamina or rupture of the basilar membrane, produces severe loss of neural elements in the region of injury and extensive new bone formation preventing satisfactory electrical stimulation. The findings suggest that long-term cochlear implantation is feasible in sensory deafened animals using Silastic sheathed electrode arrays which have been molded to conform to the basal scala tympani provided the integrity of the scala tympani, osseous spiral lamina and basilar membrane is maintained.     

Osseous tissue engineering with gene therapy for facial bone reconstruction

OBJECTIVE: Facial osseous defects remain a major functional and esthetic challenge for the head and neck surgeon. Tissue engineering may provide advantageous alternatives to conventional therapies. The objective of the study was to evaluate the efficacy of gene therapy in the repair of osseous facial defects. STUDY DESIGN: Blinded, controlled, prospective animal experiment. METHODS: Thirty adult athymic nude rats were divided into five groups of six animals. Three groups were used as control subjects. Two groups were treated with 3.75 x 10(8) viral particles containing recombinant type 5 adenoviral vectors. One group received viruses that coded for beta-galactosidase production, another received viruses that coded for bone morphogenetic protein (BMP-2) production. After 120 days rats were examined at necropsy with precise planimetry, histological analysis of new bone growth, and radio-densitometric analysis of bone thickness. RESULTS: Radio-densitometric measurements showed that BMP-2-treated nude athymic rats had significantly enhanced osseous repair compared with control subjects when evaluated by both radio-densitometry and histological examination. CONCLUSION: Gene therapy-treated, immunosuppressed rodents had an enhanced osteoinductive repair of a dorsal osseous nasal defect.     

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     

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.     

Audiovestibular phenotype associated with a COL11A1 mutation in Marshall syndrome

BACKGROUND: Marshall syndrome is a dominant disorder characterized by craniofacial and skeletal abnormalities, sensorineural hearing loss, myopia, and cataracts, and is associated with splicing mutations in COL11A1. OBJECTIVE: To determine the auditory and vestibular phenotypes associated with a COL11A1 splicing. DESIGN: Clinical otolaryngologic, audiologic, vestibular, and radiologic evaluations of the auditory and vestibular systems. SUBJECTS: Three affected individuals from a family cosegregating Marshall syndrome and a COL11A1 splice site mutation. RESULTS: The study subjects have progressive sensorineural hearing loss that is predominantly cochlear in origin and asymptomatic dysfunction of the central and peripheral vestibular systems. Computed tomography detected no malformations of temporal bone structures. CONCLUSIONS: The observed auditory and vestibular abnormalities are not caused by defective morphogenesis of the osseous labyrinth, but by more direct effects of the COL11A1 mutation on the membranous labyrinth and the central nervous system. The onset and degree of hearing loss associated with COL11A1 mutations are useful clinical features to differentiate Marshall syndrome from the phenotypically similar Stickler syndrome.     

Localization of type II, IX and V collagen in the inner ear.

Types II and IX collagen are traditionally considered cartilage collagens; however, within the inner ear, types II and IX collagen have a more diverse distribution. In the adult gerbil, type II collagen is the major fibrillar component. In the otic capsule it is present surrounding the osteocytes embedded and branching in the periosteal layer, in the cartilaginous rests of the enchondral layer, and in the endosteal layer bordering the membranous labyrinth. In the regions of the sensory cells, type II collagen is found in the osseous spiral lamina, the connective tissue of the spiral limbus, the subepithelial tissue of the maculae in the vestibule and the cristae in the ampullae, and in the spiral ligament. It is present in the non-cartilaginous and acellular structures of the tectorial membrane over the cochlear hair cells and the vestibular membrane lining the semicircular canals. Type IX collagen, when present, in all cases co-localizes with type II collagen but is found in more limited regions. It is found only in the cartilaginous rests of the enchondral bone, the tectorial membrane and the vestibular membrane. Type V-like collagen, a connective tissue collagen, is found to have a complementary localization to types II and IX collagen within the interstitial bone of the otic capsule, the osseous spiral lamina and the tectorial membrane, but it is absent from the vestibular membrane. This report is the first documenting the co-localization of types II and IX collagen.(ABSTRACT TRUNCATED AT 250 WORDS)     

Engineering a bone free flap for maxillofacial reconstruction: technical restrictions

Vascularisation is a key for success in bone tissue engineering. Creating a functional vascular network is an important concern so as to ensure vitality in regenerated tissues. Many strategies were developed to achieve this goal. One of these is cellular growth technique by perfusion bioreactor chamber. These new technical requirements came along with improved media and chamber receptacles: bioreactors (chapter 2). Some bone tissue engineering processes already have clinical applications but for volumes limited by the lack of vascularisation. Resorbable or non-resorbable membranes are an example. They are used separately or in association with bone grafts and they protect the graft during the revascularization process. Potentiated osseous regeneration uses molecular or cellular adjuvants (BMPs and autologous stem cells) to improve osseous healing. Significant improvements were made: integration of specific sequences, which may guide and enhance cells differentiation in scaffold; nano- or micro-patterned cell containing scaffolds. Finally, some authors consider the patient body as an ideal bioreactor to induce vascularisation in large volumes of grafted tissues. “Endocultivation”, i.e., cellular culture inside the human body was proven to be feasible and safe. The properties of regenerated bone in the long run remain to be assessed. The objective to reach remains the engineering of an “in vitro” osseous free flap without morbidity.     

The shortened cochlea: its classification and histopathologic features

INTRODUCTION: The term 'Mondini dysplasia' has been used to describe virtually any congenital abnormality of the osseous labyrinth resulting in confusion and seemingly contradictory observations and conclusions about this type of deformity. The purpose of this study is to histopathologically classify and describe temporal bones whose cochleas have less than 2.5 turns. METHODS: Of the 1800 temporal bones in our collection, 21 from 12 cases were found to have cochleas with less than 2.5 cochlear turns. Ages ranged from stillborn to 50 years. Temporal bones were harvested at autopsy, processed and embedded in celloidin. Sections were cut at a thickness of 20 microm and every 10th section stained with hematoxylin-eosin and examined using light microscopy. The number of turns, length of cochlea, integrity of cochlear base, length of modiolus, abnormalities of the semicircular canals and vestibule, enlargement of the vestibular aqueduct and middle ears were documented. Twenty-one temporal bones from age-matched patients without cochlear deformities were used as controls for modiolar length measurements. RESULTS: Malformation of the shortened cochlea was histopathologically classified into three groups as follows: (1) Common cavity, cochlear dysplasia (one ear)--severe dysplasia of the cochlea without a complete basal turn; (2) Mondini dysplasia (11 ears)--1.5 cochlear turns, a complete basal turn, an incomplete or absent interscalar septum and a complete bone at the base of the modiolus; and (3) Mondini-like dysplasia type A (five ears)--2 turns to the cochlea including a complete basal turn and complete bone at the base of the modiolus; and type B (four ears)--1.5-2 turns to the cochlea, hypoplasia of or a missing bone at the base of the modiolus (either with or without a communication between the internal auditory canal and the cochlea) and a complete basal turn. CONCLUSION: The range of congenital malformations in short cochlea is highly variable. Fundamental to the accurate evaluation of a labyrinthine anomaly, malformations of the inner ear should be classified according to the findings in the labyrinth. We suggest the use of common cavity cochlear dysplasia, Mondini dysplasia and Mondini-like dysplasia to describe these variable anomalies.     

Mastoid bone graft in implantology. A case report

INTRODUCTION: In implantology, autogenous bone remains currently a useful-material to rebuild horizontal and vertical osseous defects. Usually, it is the needed osseous volume that indicates the grafting procedure, intraoral one for small and middle volume and extraoral one for severely atrophied jaws. The originality of this case report is to show an alternative to usual grafting procedure borrowed from ENT surgeons: osseous mastoid graft. TECHNICAL NOTE: A 63-year-old patient with maxillary sinus pathology underwent during same surgical time maxillary sinus curetting and osseous grafting to finalize the dental treatment. DISCUSSION: Mastoid cortical bone is a source of bone usable in oral implantology. Its use has been proved to be reliable in oto-surgery. Mastoid bone harvesting implies the presence of ENT surgeon; it is nevertheless interesting to know this site from a biological point of view and because of its functional and economical aspects.     

Temporal bone density measurements using CT in otosclerosis

OBJECTIVE: To assess the bone density around the bony labyrinth in otosclerosis patients and to compare it to that of a control population. MATERIAL AND METHODS: This was a prospective case-control study. Ten patients with otosclerosis (mean age 42 years; range 24-55 years) and 33 control patients with vestibular schwannoma (mean age 46 years; range 20-71 years) were included. All patients underwent a clinical examination, audiometry and a CT scan comprising axial and coronal views of both temporal bones. In the otosclerosis group, audiometry showed unilateral involvement in six patients and bilateral hearing loss in four. The bone density was measured at the fissula ante fenestram (FAF) and at five other anatomical points on the bony labyrinth. RESULTS: In the control group, the bone density was similar at the six anatomical points. In the otosclerosis patients, the mean bone density at the FAF was lower than that in control patients (1649+/-99.1 vs 2049+/-13.4 HU; p < 0.01). For patients with FAF bone densities < 2000 HU, a correlation was observed between hearing threshold and FAF bone density. CONCLUSION: FAF bone density appears to be a good indicator of disease progression, and could serve as a follow-up and prognostic parameter.     

Transformation of the shape of the ethmoid bone during the course of life

The ethmoid bone undergoes significant changes in the course of life. The critical period is the time from 9 to 35 years of age. The changes in its shape depend upon the intensity of pneumatization of the ethmoid labyrinth and frontal sinus. If pneumatization of the labyrinth is excessive, the ethmoidal cells are not covered by the frontal bone. On the contrary, they are incorporated in the inferior floor of the anterior cranial fossa, resulting in a possible risk of penetration during surgical ethmoidectomy.     

Endolymphatic sac tumours: surgical management

BACKGROUND: Endolymphatic sac tumours (ELSTs) have been known as an individual tumour entity only since 1984. ELSTs may occur either solitarily and sporadically or as a hereditary manifestation associated with von Hippel-Lindau (VHL) disease. The latter association was first observed in 1992 and confirmed by molecular genetic analysis of the VHL gene. No consensual diagnostic and treatment strategy of ELST exists at present. METHODS: Based on imaging criteria in computed tomography, magnetic resonance imaging (MRI), and magnetic resonance angiography, we developed a staging system to classify ELST in a series of seven consecutive patients in an attempt to custom-tailor the surgical approach. Type A referred to tumours that were locally confined without temporal bone erosion or infiltration of the dura (n = 2); type B tumours showed evidence of bone infiltration of the osseous labyrinth and sensorineural hearing loss (n = 2); and in type C, the tumour further invaded the sigmoid sinus and jugular bulb (n = 3). Two patients suffered from VHL disease. RESULTS: In all patients, the tumour was completely removed. Stage-adapted surgical approaches included various transpetrosal procedures, from the translabyrinthine to the infratemporal approaches. The functional integrity of the facial nerve was maintained in all tumour stages, whereas the vestibulocochlear nerve could be preserved only in patients with type A tumours. Follow-up MRI demonstrated no local tumour recurrence during a postoperative observation period ranging from 4 to 38 months. CONCLUSION: Stage-based surgical strategy enables the complete removal of ELST with minor morbidity. Transmastoid approaches are most efficient for resection of the tumour matrix to prevent local recurrence.     

Anatomic basis for labyrinthine preservation during posterior fossa acoustic tumor surgery

Earlier diagnosis of acoustic tumors promises to increase our opportunity to identify patients with serviceable hearing. Critical to a posterior fossa transmeatal approach for acoustic tumor resection is preservation of the underlying labyrinth. Although the labyrinth has been recognized as a limiting factor in exposure of tumor in the internal auditory canal, few reports have detailed the microscopic surgical anatomy posterior to the internal auditory canal. An anatomic study was undertaken to determine consistent relationships between critical structures within the temporal bone relevant to hearing preservation surgery. The results of this study indicate that, whereas topographic landmarks are helpful for orientation, the more consistent relationship of the labyrinth to the vestibular aqueduct and singular canal allows a more accurate localization of the underlying labyrinth. Although the vestibule frequently prevents direct visualization of the transverse crest, a dissection based upon the microsurgical anatomy will maximize visualization of the lateral fundus while preserving the integrity of the labyrinth.     

Do extant elephants have superior canal dehiscence syndrome?

Conclusion: X-ray CT of an Asian elephant’s skull suggest that elephants do not have a labyrinthine 3^rd mobile window. This excludes the concept that elephants benefit from enhancement of bone conducted vibration by an extra opening of the labyrinth. This finding does not, however, exclude that elephants use bone conducted hearing for seismic detection, nor that other species may use an extra labyrinthine opening for improved detection of seismic signals. Objectives: In man, a pathologic extra opening of the bony labyrinth causes altered hearing with supranormal bone conduction. Theoretically, this variation in auditory performance could be advantageous for detection of seismic waves. Method: The skull of an adult Asian elephant was examined by X-ray computed tomography to investigate whether a natural ‘3^rd mobile window’ mechanism for enhanced sensitivity of body sounds exist in elephants. Results: Although the entire elephant’s skull was otherwise broadly aerated, the labyrinth areas were surrounded by dense bone.     

Haemangioma of the maxilla

Haemangioma involving the paranasal air sinuses is rare. It presents with severe epistaxis or bleeding due to dental extraction and may mimic malignancy. A case of haemangioma of the maxilla is presented and the diagnostic and operative difficulties together with a review of literature are discussed. Bucy and Capp (1930) described primary haemangioma of bone with special reference to X-ray diagnosis. Wyke (1949) was of the opinion that haemangiomas accounted for only 10 per cent of primary benign neoplasms of skull bones. Batsakis (1979) commented that haemangioma of bone accounted for seven per cent of all osseous neoplasms and that from a review of literature he had found no more than 40 such cases. Dahlin (1967) in a review of 3,947 cases of bone tumours, found 47 cases of osseous haemangioma out of which only three involved the upper jaw. Smith (1959) reported that only 10 cases of haemangioma of the maxilla had been published by 1959 and further isolated cases have been described by Sawhney et al. (1973), Pandhi et al. (1977) and Ahad and Chisti (1977).     

Morphological substantiation of surgical sanation of the ethmoidal labyrinth in patients with inflammatory pathology of frontal sinuses

This study had the objective of evaluating intraoperative characteristics of sanation surgery for the correction of structural elements of ethmoid bone in 131 patients presenting with frontitis. Moreover, it included histological examination of the resected tissues. It was shown that chronic frontitis is associated not only with serious morphological changes in mucous membrane of the respective frontal sinusis and along the entire length of ethmoidal labyrinth but also with necrobiotic processes in the ethmoid bone plates, depending on the state of the ostiomeatal complex. It is supposed that these findings may account for irregular or low effect of conservative therapy of chronic frontitis and confirm the necessity of surgical sanation of ethmoidal labyrinth with due regard for the state of the ostiomeatal complex.