Acoustic responses of the human middle ear

Measurements on human cadaver ears are reported that describe sound transmission through the middle ear. Four response variables were measured with acoustic stimulation at the tympanic membrane: stapes velocity, middle-ear cavity sound pressure, acoustic impedance at the tympanic membrane and acoustic impedance of the middle-ear cavity. Measurements of stapes velocity at different locations on the stapes suggest that stapes motion is predominantly ‘piston-like’, for frequencies up to at least 2000 Hz. The measurements are generally consistent with constraints of existing models. The measurements are used (1) to show how the cavity pressure and the impedance at the tympanic membrane are related, (2) to develop a measurement-based middle-ear cavity model, which shows that the middle-ear cavity has only small effects on the motion of the tympanic membrane and stapes in the normal ear, although it may play a more prominent role in pathological ears, and (3) to show that inter-ear variations in the impedance at the tympanic membrane and the stapes velocity are not well correlated.     

The Value of Measuring Eustachian Tube Aeration on Temporal Bone CT in Patients with Chronic Otitis Media

Objectives

To evaluate that the cross-sectional area of the air space in the Eustachian tube (ET) on computed tomography (CT) images could be useful for predicting the postoperative aeration of the middle ear.

Methods

The patient group consisted of 80 patients (80 ears) with chronic otitis media and who underwent middle ear surgery from 2006-2007 and who were followed up for more than 1 yr. The control group consisted of 100 ears of 50 individuals with normal tympanic membranes and who underwent CT for other causes (such as tinnitus or hearing loss). The largest cross-sectional areas of the aerated ET were measured on the coronal images of the temporal bone CT by a single otologist using the computer-based "Region of Interest" picture archiving and communications system. The patient group was divided into two subgroups, 1) those with good postoperative aeration and 2) those with poor postoperative aeration. The largest cross-sectional areas of the aerated ETs were compared between the patients and the controls, and between the patients with good aeration and the patients with poor aeration.

Results

The mean cross-sectional areas significantly differed between the patient group and the control group, and between the good and poor aeration subgroups (P<0.05 each). The mean area of the poor aeration subgroup was smaller than that of the control group (P<0.05), but the mean area of the good aeration subgroup did not significantly differ from that of the controls.

Conclusion

The cross-sectional area of the aerated ET, as measured on the preoperative coronal images of temporal bone CT scans, may be useful for predicting the postoperative condition of the tympanic cavity.     

镫骨环韧带固定对中耳传声的影响——有限元模型研究

目的　有限元模型分析镫骨环韧带固定对中耳传声的影响。方法　依据1例成年男性颞骨标本Micro-CT扫描数据,建立正常成人中耳有限元模型。通过调整镫骨环韧带的杨氏模量,建立镫骨环韧带固定的有限元模型。计算一定声压刺激下鼓膜与镫骨底板振幅,进而反映建立镫骨环韧带固定时对中耳传声的影响。结果　有限元模型计算结果显示：镫骨环韧带固定时,镫骨底板振动显著减小达47 dB,而对鼓膜振动影响不明显。结论  有限元模型理论分析,镫骨环韧带固定对中耳传声的影响接近于临床观察结果,但需进一步与颞骨实验研究结果对照。深入认识中耳传声机制,为临床耳硬化症提供基础数据。     

Association of abnormal appearance of tympanic membrane with minimal temporal bone pneumatization. A cadaver study

The association of abnormal tympanic membrane appearance with minimal pneumatization of the temporal bone was studied in 28 unilateral formalin-fixed cadaver specimens. The photographic appearance of each tympanic membrane was judged by seven otolaryngologists, and a normalcy score determined. The normalcy score of the tympanic membranes had a weak association (tau = 0.27, p less than 0.05) with pneumatization volume, as determined by computed tomography. The same trend, though not statistically significant, was found with pneumatization area determined by lateral radiographs. For cross-sectional surveys, the otitis media condition is probably best identified by a combination of indicators: bilateral extent of pneumatization as assessed by computed tomography, bilateral appearance of the tympanic membranes, and a history of otitis media.     

How to reliably evaluate middle ear diseases? Comparison of different methods of post-processing based on multislice computed tomography examination

CONCLUSIONS: Multislice computed tomography (MSCT) virtual endoscopy was useful in evaluating mainly post-traumatic and postoperative cases. In other pathological conditions axial images and MPR reformations were most useful. OBJECTIVES: Evaluation of cross-sectional images, multiplanar 2-D reformations, 3-D reconstructions and virtual endoscopy (VE) in assessment of the middle ear in inflammatory diseases, trauma, otosclerosis and tumours. Comparison of each method and correlation with surgical findings. MATERIALS AND METHODS: Investigations were carried out in 80 patients with middle ear pathology. In each case MSCT of the petrous bone was performed. In addition to cross-sectional native scans, frontal and sagittal images were achieved using MPR reconstructions. 3-D volume rendering (VR) and VE images were also generated. The value of native scans information, 2-D, 3-D reconstructions and VE of the tympanic cavity structures was assessed in comparison to intraoperative findings. RESULTS: MPR reconstructions were most useful in the assessment of skull base trauma, skull base tumours and in cases of chronic middle ear inflammation. Highly vascularized tumours, disruption of ossicular chain and stapes prosthesis were best evaluated on 3-D reconstructions. Axial images proved to be the best for otosclerosis interpretation.     

3D-CT highly useful in diagnosing foreign bodies in the paraesophageal orifice

Multislice computed tomography (CT) enables rapid, easy construction of 3-dimensional CT images (3D-CT), aiding diagnostic imaging. 3D-CT is reported to be highly useful in diagnosing temporal bone disorders, in otorhinolaryngology, especially abnormal shape and the ossicular chain of the auditory ossicles and facial bone fractures. Given the complexity of laryngeal anatomy, 3D-CT is useful in diagnosing the extent of infiltration of laryngeal cancer and in examining vocal cord movement, which is difficult to evaluate by conventional CT, magnestic resonance imaging (MRI), and fiberscopy. Among patients seen for a suspected foreign body between June 2002 and May 2003, we chose 3 in whom laryngoscopy at the first examination could not detect a foreign body but in whom symptoms and findings suggested such presence in the paraesophageal orifice. In all 3 cases, 3D-CT imaging showed the size, length, location, and direction of the foreign body, providing information useful for the surgical approach.     

Computerized tomography: features of roentgeno-anatomy of the temporal bone

Normal X-ray and computed-tomography anatomy of the temporal bone are presented. It is indicated that computed tomography has certain advantages over routine X-ray methods because it allows simultaneous visualization of bone structures and soft tissues of the temporal bone. The anatomical picture of every compartment of the tympanic cavity as seen in CT and visual features of different structures of the temporal bone as related to the tomographic section plane are described in detail. In addition to the clinical advantages, CT is superior to standard X-ray methods in terms of radiation safety of the lens. CT data help to understand correctly the nature of pathological formations in the temporal bone and to apply adequate and effective therapeutic measures.     

Evaluation of the Dresden Tympanoplasty Model (DTM)

The training of microsurgical motor skills is essentiell for surgical education if the interests of the patient are to be safeguarded. In otosurgery the complex anatomy of the temporal bone and variations necessitate a special training before performing surgery on a patient. We therefore developed and evaluated a simplified middle ear model for acquiring first microsurgical skills in tympanoplasty.The simplified tympanoplasty model consists of the outer ear canal and a tympanic cavity. A stapes model is placed in projection of the upper posterior tympanic membrane quadrant at the medial wall of the simulated tympanic cavity. To imitate the annular ligament flexibility the stapes is fixed on a soft plastic pad. 41 subjects evaluated the model′s anatomical analogy, the comparability to the real surgical situation and the general model properties the using a special questionnaire.The tympanoplasty model was very well evaluated by all participants. It is a reasonably priced model and a useful tool in microsurgical skills training. Thereby, it closes the gap between theoretical training and real operation conditions.     

Imaging of a congenital perilymphatic fistula

A 7-year-old boy with a history of purulent meningitis and watery rhinorrhea was studied using computed tomography (CT) and magnetic resonance imaging (MRI). He had a common cavity in the left inner ear. With high-resolution heavily T2-weighted MRI, leakage of the inner ear fluid into the middle ear at the oval window area through a congenital perilymphatic fistula could be visualized. Surgery to close the fistula showed a perforation in the stapes footplate.     

High-resolution petrous bone imaging using multi-slice computerized tomography

Multi-slice computerized tomography (MSCT) is considered to provide superior image quality. We defined a data acquisition protocol for high-resolution (HR) temporal bone imaging using MSCT and assessed its impact on data acquisition and post-processing (PP). The data acquisition protocol was defined in cadaveric phantom studies performed by MSCT and subsequently applied to 38 patients referred for temporal bone assessment. The parameters image quality and diagnostic value of MSCT data were assessed for the cross-sectional source images as well as for 2-dimensional (2D) reformations and 3-dimensional (3D) reconstructions by 3 radiologists by comparison with incremental HR scans of 17 patients with suspected middle ear disorders. The data acquisition protocol yielded HR images with an excellent detail resolution and a comparable image quality of cross-sectional scans and related orthogonal reformations. MSCT achieved higher scores for image quality and diagnostic value (p < 0.001, t-test) than incremental HR CT with regard to both 2D and 3D reconstructions. MSCT improves the image quality of HR cross-sectional scans as well as that of 2D and 3D PP techniques in petrous bone imaging. The radiation exposure of the eye lenses is increased by MSCT as gantry angulation is not yet possible in the helical scan mode.     

Office-based endoscopic procedure for diagnosis in conductive hearing loss cases using OtoScan Laser-Assisted Myringotomy

OBJECTIVES/HYPOTHESIS: In conductive hearing loss (HL), even though preoperative examinations including audiometry, tympanometry, and computed tomography (CT) scan are applied, exploratory tympanotomy is necessary to make an exact diagnosis of ossicular interruption and stapes fixation. Precise preoperative diagnosis would be useful for patient counseling, surgical indications, and planning. The advantages of office-based OtoScan laser-assisted myringotomy (LAM), which makes a circular and non-hemorrhagic perforation, prompted us to investigate other uses of LAM in addition to ventilation and drainage of the tympanic cavity. To make presurgical diagnosis in conductive HL, endoscopes with an outer diameter of 1.7 or 1.9 mm were used to inspect the middle ear pathology through perforations with a diameter of 2 mm made by LAM. METHODS: In the outpatient clinic, a circular perforation with a diameter of 2 mm was made in the tympanic membrane with LAM. An endoscopic view of the ossicular chain through a 70degrees angled tip endoscope held immediately to the outer side of the perforation was obtained to diagnose conduction disturbance loci in conductive HL cases. RESULTS: Ossicular chain abnormalities were easily and safely detected by clean endoscopic views obtained through a nonhemorrhagic circular perforation. When necessary, insertion of the tip of the endoscope into the tympanic cavity provided additional views of epitympanum. CONCLUSION: We suggest that transtympanic endoscopy through the perforation made by LAM is an effective and safe office-based procedure for diagnosis in conductive HL cases and could be an alternative procedure to replace exploratory tympanotomy.     

CT scans and 3D reconstructions of Florida manatee (Trichechus manatus latirostris) heads and ear bones

The auditory anatomy of the Florida manatee (Trichechus manatus latirostris) was investigated using computerized tomography (CT), three-dimensional reconstructions, and traditional dissection of heads removed during necropsy. The densities (kg/m3) of the soft tissues of the head were measured directly using the displacement method and those of the soft tissues and bone were calculated from CT measurements (Hounsfield units). The manatee's fatty tissue was significantly less dense than the other soft tissues within the head (p<0.05). The squamosal bone was significantly less dense than the other bones of the head (p<0.05). Measurements of the ear bones (tympanic, periotic, malleus, incus, and stapes) collected during dissection revealed that the ossicular chain was overly massive for the mass of the tympanoperiotic complex.     

Computed tomography in the evaluation of acquired stenosis in the neonate

We studied the feasibility of computed tomographic evaluation of the neonatal airway. Three neonatal larynges, removed at necroscopy, were examined by computed tomography. Good resolution of soft tissue, cartilage and airway lumen was obtained in these small specimens. On the basis of these findings two neonates with acquired subglottic stenosis were examined by endoscopy, soft tissue airway radiographs, and computed tomography. Measurements of radiation dose revealed that a computed tomographic study delivered 36% of the mean tissue dose of standard image intensifier fluoroscopy. Computed tomography and fluoroscopy both demonstrated the degree and length of this stenosis accurately. An advantage of CT over conventional imaging procedures was better definition of the cross sectional area of the airway.     

The condition of the auditory tube in patients with chronic purulent otitis media as shown by computed tomography

Computed tomography (CT) was made in 25 patients with otitis media purulenta chronica (OMPC). Of them 17 patients had meso- or mesoepitympanitis and 8 patients had the history of radical operations on the ear. At first, CT was made of the temporal bone without contrast medium, then with instillation of the contrast medium through the external acoustic meatus and tympanic cavity into the auditory tube. Native computer tomograms of the temporal bones of 43 persons without any middle ear pathology were used as control. Non-contrast computer tomograms showed air in the lumen of the bone part of the auditory tube of all the examinees. It was impossible to obtain the image of the cartilage part of the auditory tube. None of 25 OMPC patients showed the signs of peritubal pneumatisation while it was registered in 14 healthy controls. By CT data, 14 of 17 patients with perforative OMPC had passable auditory tube even in aggravated inflammatory process, 3 of them had unpassable one. All 8 patients after radical operation had unpassable auditory tube. Thus, the method of contrast computer tomography determines passability of the auditory tube in the direction from the tympanic cavity to the nasopharynx and specifies the level of obstruction that is important to know before hearing improving operations of tympanoplasty type. Evaluation of the drainage function of the auditory tube basing on the time of evacuation of the contrast medium from the tympanic cavity to the nasopharynx was declared useless.     

High-resolution computed tomography of the temporal bone: its role in the evaluation of middle ear disease

High-resolution computed tomography (CT) was performed on the temporal bones of 93 patients in conjunction with pluridirectional tomography. The majority of the patients were scanned on the prototype Pfizer 0200 FS second-generation scanner, modified to meet the demands of high-resolution scanning. Images from this relatively economical scanner are almost comparable to those obtainable with the GE CT/T 8800 scanner in spatial and contrast resolution. CT scans of the temporal bone were found to be more sensitive than pluridirectional tomography in visualizing fractures and soft tissue masses in the middle ear, including fluid levels and tympanic membrane swelling. It is concluded that high-resolution CT of the temporal bone will probably soon entirely replace pluridirectional tomography.     

Visualization of the middle ear with high resolution computed tomography and superfine fiberoptic videomicroendoscopy

Ten temporal bone blocks were dissected from fresh postmortem specimens from patients succumbing to diseases unrelated to the ears. A superfine fiberoptic videomicroendoscope (SFV) was introduced through the eustachian tube into the middle ear, and middle ear structures were visualized. The cadaver temporal bone blocks were also studied with high-resolution computed tomography (HRCT). When HRCT gave good results SFV did not succeed well and vice versa. However, SFV provided topographic anatomical information of the middle ear structures while HRCT gave cross-sectional images of the anatomy of the tympanic cavity. The different types of information obtained by the two imaging technologies supplement each other and were found to improve diagnosis in such cases as external ear canal atresia. Received: 22 July 1997 / Accepted: 28 October 1997     

Modelling of components of the human middle ear and simulation of their dynamic behaviour

In order to get a better insight into the function of the human middle ear it is necessary to simulate its dynamic behaviour by means of the finite-element method. Three-dimensional measurements of the surfaces of the tympanic membrane and of the auditory ossicles malleus, incus and stapes are carried out and geometrical models are created. On the basis of these data, finite-element models are constructed and the dynamic behaviour of the combinations tympanic membrane with malleus in its elastic suspensions and stapes with annular ligament is simulated. Natural frequencies and mode shapes are computed by modal analysis. These investigations showed that the ossicles can be treated as rigid bodies only in a restricted frequency range from 0 to 3.5 kHz.     

Congenital Stapes Anomalies with Normal Eardrum

Objectives

A non-progressive and conductive hearing loss with normal eardrum, but no history of trauma and infection, is highly suggestive of a congenital ossicular malformation. Among ossicular anomalies, stapes anomaly is the most common. The purpose of this study is to describe patterns of stapes anomaly and to analyze its surgical outcome with special reference to its patterns.

Methods

We conducted a retrospective case review. The subjects comprised 66 patients (76 ears) who were decisively confirmed by the exploratory tympanotomy as congenital stapes anomalies without any anomalies of the tympanic membrane and external auditory canal. The preoperative and postoperative audiological findings, temporal bone computed tomography scan, and operative findings were analyzed.

Results

There were 16 anomalous patterns of stapes among which footplate fixation was the most common anomaly. These 16 patterns were classified into 4 types according to the status of stapes footplate. Successful hearing gain was achieved in 51 out of 76 ears (67.1%) after surgical treatment.

Conclusion

Footplate fixation was usually bilateral, whereas stapes anomalies associated with other ossicular anomaly were usually unilateral. The success of the surgical treatment of stapes anomaly might depend on its developmental status of the footplate. Stapes anomalies were detected without any fixed patterns, therefore, it is quite possible to detect a large variety of patterns in future.     

High-resolution Petrous Bone Imaging Using Multi-slice Computerized Tomography

Multi-slice computerized tomography (MSCT) is considered to provide superior image quality. We defined a data acquisition protocol for high-resolution (HR) temporal bone imaging using MSCT and assessed its impact on data acquisition and post-processing (PP). The data acquisition protocol was defined in cadaveric phantom studies performed by MSCT and subsequently applied to 38 patients referred for temporal bone assessment. The parameters image quality and diagnostic value of MSCT data were assessed for the cross-sectional source images as well as for 2-dimensional (2D) reformations and 3-dimensional (3D) reconstructions by 3 radiologists by comparison with incremental HR scans of 17 patients with suspected middle ear disorders. The data acquisition protocol yielded HR images with an excellent detail resolution and a comparable image quality of cross-sectional scans and related orthogonal reformations. MSCT achieved higher scores for image quality and diagnostic value (p &lt; 0.001, t-test) than incremental HR CT with regard to both 2D and 3D reconstructions. MSCT improves the image quality of HR cross-sectional scans as well as that of 2D and 3D PP techniques in petrous bone imaging. The radiation exposure of the eye lenses is increased by MSCT as gantry angulation is not yet possible in the helical scan mode.