Endoscopic trans-eustachian tube approach: identifying the precise landmarks, a novel radiological and anatomical evaluation

PURPOSE

The endoscopic trans-eustachian approach (ETETA) is a less invasive approach to the infratemporal fossa (ITF), providing superior exposure compared to traditional transcranial approaches. The anatomy of the pharyngotympanic (eustachian) tube and adjacent neurovascular structures is complex and requires in-depth knowledge to safely perform this approach. We present a cadaveric and radiological assessment of critical anatomic considerations for ETETA.

METHODS

Six adult cadaveric heads were dissected alongside examination of 50 paranasal sinus CT scans. Key anatomic relationships of the pharyngotympanic tube and adjacent structures were qualitatively and quantitatively evaluated. Descriptive statistics were performed for quantitative data.

RESULTS

Anatomical and radiological measurements showed lateralization of the pharyngotympanic tube allows access to the ITF. The pharyngotympanic tube has bony and cartilaginous parts with the junction formed by the sphenoid spine and foramen spinosum. The bony part and tendon of the tensor tympani muscle were located at the posterior genu of the internal carotid artery. The anterior and inferior wall of the carotid canal was located between the horizontal segment of the internal carotid artery and petrous segment of the cartilaginous pharyngotympanic tube.

CONCLUSION

The combination of preoperative radiographic assessment and anatomical correlation demonstrates a safe and effective approach to ETETA, which allowed satisfactory visualization of ITF. The morphological evaluation showed that the lateralization of the pharyngotympanic tube and related structures allowed a surgical corridor to reach the ITF. Endoscopic surgery through the pharyngotympanic tube is challenging, and in-depth understanding of the key anatomic relationships is critical for performing this approach.

Endoscopic Endonasal Approach to the Ventral-Medial Portion of Posterior Paramedian Skull Base: A Morphometric Perspective of Surgical and Radiologic Anatomy

OBJECTIVE

This study aims to provide morphometric analysis of endoscopic endonasal approach (EEA) to the ventral-medial portion of posterior paramedian skull base. Furthermore, it aims to investigate the surgical exposure obtained through EEA with and without eustachian tube (ET) removal, emphasizing the role of contralateral nostril (CN) access.

METHODS

Five fresh adult head specimens were prepared for dissection. A predissection and a postdissection computed tomography study was performed. A surgically oriented classification into 4 regions was used: 1) tubercular region; 2) occipital condyle region; 3) parapharyngeal space (PPhS) region; and 4) jugular foramen (JF) region. The Student t-test was used to compare angulations and measures of EEA with access from the ipsilateral and CN, respectively, with and without ET removal.

RESULTS

EEA to the ventral-medial portion of posterior paramedian skull base encompasses 2 medial trajectories (transtubercular and transcondylar) and 2 lateral pathways to the PPhS and JF. The CN access, without removal of the ET, allows a complete exposure of the petrous and intrajugular portion of the JF and superior PPhS without exposition of the parapharyngeal segment of internal carotid artery. The ipsilateral nostril approach with ET removal allows to obtain a wider exposure, reaching the medial sigmoid part of the JF. No significant differences exist in regard to transtubercular and transcondylar approaches.

CONCLUSIONS

This study suggests that EEA to posterior paramedian skull base allows the realization of a corridor directed to the jugular tubercle, occipital condyle, medial PPhS, and ventral-medial JF. The CN approach with ET preservation can expose the petrous and intrajugular parts of the JF and PPhS. Case series are needed to demonstrate benefits and drawbacks of these approaches.

Evaluation of the relationship of chronic otitis media with the Körner's septum, auditory tube angle, and tubotympanic angle

PURPOSE

This study aimed to evaluate the relationships between chronic otitis media (COM) and the characteristics of Auditory tube (Eustachian) angle (ATa), tubotympanic angle (TTa), and Körner's septum (KS).

METHODS

A retrospective research was conducted between January 2019 and October 2019. The computed tomography (CT) results and medical files of 210 patients were evaluated. According to CT results and medical files, the patients were evaluated regarding the presence of COM, KS, ATa, and TTa.

RESULTS

There were 113 (53.81%) males and 97 (46.19%) females in the study group, and the mean age of the patients was 42.05 ± 10.77 years. The frequency of the KS was significantly higher in patients who were diagnosed with COM (35.66% vs. 7.41%, p < 0.001). The patients diagnosed with COM were found to have a narrower ATa and a wider TTa than the patients who were not diagnosed with COM. ATa was narrower and TTa was wider in patients with KS. The presence of KS and higher TTa value were considered as risk factors for COM (p < 0.001, p < 0.001, respectively) CONCLUSION:  Our findings indicate that ATa was narrower, TTa was wider and KS was more frequent in patients with COM. Analysis of risk factors demonstrated that increased TTa and the presence of KS were associated with increased risk for COM.

Dimensions and position of the Eustachian tube in Humans

Eustachian tube (ET) dysfunction is one of the causes for chronic otitis media. To develop new therapies such as stents to facilitate middle ear ventilation, a better knowledge on dimensions and positions of the ET in individual patients is necessary. Cone beam CT scans of 143 patients were retrospectively investigated. Parameters such as lengths of the ET and its cartilaginous and bony parts, diameters, angles as well as distance of the ostium from the nasal conchae were determined and evaluated for side, gender and age specific differences. The average length of the cartilaginous and bony tubes was smaller in women than men. The average deviation from the horizontal plane was 1.7° larger on the left side (35.4°) compared to the right side (33.7°). Tools to manipulate the ET or to insert stents into the ET should cover angles from at least 42° to 64°. The distance of the pharyngeal orifices from the conchae nasalis inferior increased with age, becoming most prominent above 70 years of age. This investigation provides necessary information to develop stents for human application and tools for safe positioning of the stents.

The extended bundle of the tensor veli palatini: Anatomic consideration of the dilating mechanism of the Eustachian tube

OBJECTIVE

The aim of this study was to analyze the topographical structures of the muscles surrounding the Eustachian tube.

MATERIALS AND METHODS

We conducted macroscopic and histological studies of 24 halves of 12 heads from Japanese cadavers.

RESULTS

The main findings were as follows: 1) the infero-lateral muscle bundles of the tensor veli palatini didn't turn medially at the pterygoid hamulus but were distributed laterally and continuous with the buccinator; 2) the tensor veli palatini attached laterally to the membranous part of the Eustachian tube; 3) the superior pharyngeal constrictor was not only adjacent to the buccinator at the pterygomandibular raphe but also had muscular continuation with it laterally and 4) some bundles of the superior pharyngeal constrictor adhered with the palatine aponeurosis.

CONCLUSION

We believe that the cooperation of the muscles contributes to the dilating mechanism of the Eustachian tube, due to the complex topographical structures of the surrounding muscles: the tensor veli palatini, the levator veli palatini, the superior pharyngeal constrictor and the buccinator.

[Surgical anatomy, technique and application of endoscopic endonasal transpterygoid approach in skull base surgery]

OBJECTIVE

To identify the landmarks of transpterygoid approach and to report its application in a series of cases.

METHODS

Two silicon-injected adult cadaveric heads(4 sides) were dissected by performing an endoscopic endonasal transpterygoid approach after CT scanning for imaging guidance. High-quality pictures were obtained. This approach was used to treat twelve patients with skull base lesions including 3 spontaneous cerebrospinal fluid (CSF) leaks in the lateral recess of the sphenoid sinus, 2 neurofibromas and 2 Schwannomas involving the pterygopalatine fossa and infratemporal fossa, 1 dermoid cyst involving the middle fossa and infratemporal fossa, 1 invasive fungal sinusitis invading the middle fossa base, 1 basal cell adenoma in the upper parapharyngeal space, 1 chondrosarcoma in the parasellar region and 1 adenoid cystic carcinoma. Clinical records were reviewed.

RESULTS

In terms of approach dissection, important landmarks, such as the sphenopalatine foramen and artery, vidian canal and nerve, foramen rotundum and maxillary branch of trigeminal nerve, foramen ovale and mandibular branch of trigeminal nerve, as well as pterygoid segment of Eustachian tube were identified. In terms of clinical data, three patients with spontaneous CSF leak underwent repair. Six patients with benign lesions underwent complete tumor resection. In the patient with invasive fungal disease, thorough debridement was undertaken and antifungal drug was administered for one month. For these benign skull base lesions, there was no recurrence during the follow-up period. In the patient with chondrosarcoma, most of the tumor was removed in the first operation, and was followed by two endoscopic operations because of fast growth of the tumor. Final control was achieved with chemotherapy and radiation. In the patient with adenoid cystic carcinoma, tumor recurred five years after surgery, and was reoperated.

CONCLUSION

An understanding of the landmarks of the transpterygoid approach is paramount for surgically dealing with disease located within and adjacent to the region of the pterygoid process of the sphenoid bone. The endoscopic endonasal transpterygoid approach is feasible and safe in selected patients with skull base lesions.

An expanded combined evidence approach to the Gavialis problem using geometric morphometric data from crocodylian braincases and Eustachian systems

The phylogenetic position of the Indian gharial (Gavialis gangeticus) is disputed--morphological characters place Gavialis as the sister to all other extant crocodylians, whereas molecular and combined analyses find Gavialis and the false gharial (Tomistoma schlegelii) to be sister taxa. Geometric morphometric techniques have only begun to be applied to this issue, but most of these studies have focused on the exterior of the skull. The braincase has provided useful phylogenetic information for basal crurotarsans, but has not been explored for the crown group. The Eustachian system is thought to vary phylogenetically in Crocodylia, but has not been analytically tested. To determine if gross morphology of the crocodylian braincase proves informative to the relationships of Gavialis and Tomistoma, we used two- and three-dimensional geometric morphometric approaches. Internal braincase images were obtained using high-resolution computerized tomography scans. A principal components analysis identified that the first component axis was primarily associated with size and did not show groupings that divide the specimens by phylogenetic affinity. Sliding semi-landmarks and a relative warp analysis indicate that a unique Eustachian morphology separates Gavialis from other extant members of Crocodylia. Ontogenetic expansion of the braincase results in a more dorsoventrally elongate median Eustachian canal. Changes in the shape of the Eustachian system do provide phylogenetic distinctions between major crocodylian clades. Each morphometric dataset, consisting of continuous morphological characters, was added independently to a combined cladistic analysis of discrete morphological and molecular characters. The braincase data alone produced a clade that included crocodylids and Gavialis, whereas the Eustachian data resulted in Gavialis being considered a basally divergent lineage. When each morphometric dataset was used in a combined analysis with discrete morphological and molecular characters, it generated a tree that matched the topology of the molecular phylogeny of Crocodylia.

[Conductive hearing loss caused by eustachian tube dysfunction according to the data of functional computed tomography]

The paper deals with computed tomography (CT) diagnosis of Eustachian tube dysfunction. A functional multislice spiral (MS) CT protocol has been first elaborated for the Eustachian tube. Twenty-three patients with unilateral conductive hearing loss and Eustachian tube dysfunction were examined. The normal functional anatomy of the Eustachian tube was evaluated on the side without evidence of pathology in 23 patients. Functional MSCT showed that the cartilaginous portion of the Eustachian tube opened partially and closed completely in 9 patients. Ten patients were found to have steady changes in the cartilaginous portion of the Eustachian tube. The developed method could confirm the cause of conductive hearing loss and optimally define a treatment policy.

Can you hear me now? Understanding vertebrate middle ear development

The middle ear is a composite organ formed from all three germ layers and the neural crest. It provides the link between the outside world and the inner ear, where sound is transduced and routed to the brain for processing. Extensive classical and modern studies have described the complex morphology and origin of the middle ear. Non-mammalian vertebrates have a single ossicle, the columella. Mammals have three functionally equivalent ossicles, designated the malleus, incus and stapes. In this review, I focus on the role of genes known to function in the middle ear. Genetic studies are beginning to unravel the induction and patterning of the multiple middle ear elements including the tympanum, skeletal elements, the air-filled cavity, and the insertion point into the inner ear oval window. Future studies that elucidate the integrated spatio-temporal signaling mechanisms required to pattern the middle ear organ system are needed. The longer-term translational benefits of understanding normal and abnormal ear development will have a direct impact on human health outcomes.

Magnetic resonance imaging illustrating change in the Ostmann fat pad with age

A retrospective analysis of 35 skull base patients with no history of eustachian tube dysfunction who had magnetic resonance imaging at our institution between 2006 and 2007 was conducted. The fat pad of Ostmann surface area, the eustachian tube medial cartilage, and the tensor veli palatini muscle surface area were measured in all scans. The change in anatomic structures with age was compared and showed no parameter changes except for the Ostmann fat pad, which decreased in size with age (correlation coefficient = 0.0629). There was no statistical significance between males and females in all parameters.

Functional anatomy of the Eustachian tube

The Eustachian tube (ET) is divided in 3 portions: a bony portion, a cartilaginous portion, and a junctional portion. From an anatomical-functional point of view, the bony portion of ET is the region of ventilation and clearance of secretions, and is lined by pseudostratified, ciliated, columnar epithelium, with an anti-gravitational direction of the drainage. The ET in the bony portion is in a state of forced opening. The cartilaginous portion is instead the heart of this dynamic system tube, because the mechanism of opening and closing of the tube is at this level. ET is normally closed, and it opens only during swallowing, being essential for good functioning of the middle ear, because it provides ventilation from the nasopharynx to the middle ear, and, at the same time, clearance of secretions from the middle ear-mastoid unit to the nasopharynx. Moreover, the ET protects the middle ear against nasopharyngeal pressure variations, ascending secretions, and microorganisms. The ability to develop all these functions makes the tube a complex organ.

[Specific features of the bony auditory tube in young children]

The study was designed to characterize protympanum topography and the state of the bone component of eustachian tube by examining cadaveric temporal bone preparations from young children. Serial temporal bone sections cut in different planes were available for comprehensive examination of the anterior tympanum. Results of the study may be useful for planning surgical intervention for the treatment of the diseased middle ear in the early childhood.

A surgical approach to the lateral compartment of the equine guttural pouch in the standing horse: Modification of the forgotten “Garm technique”

The objective of this study was to evaluate the feasibility, efficacy and complications following lavage and drainage of the lateral compartment (LC) of the equine guttural pouch (GP) using a modified Garm's technique (MGT). In an ex vivo study (study 1), six cadaver heads were examined to assess the anatomical limits of the surgical approach and whether vital structures might be damaged. This was followed by an in vivo study (study 2) in which a lavage/drainage tube was placed for 3 days into each LC of four standing horses using the MGT. In both studies, the procedure offered direct access into the LC and indirect access into the medial compartments of the GP. In study 1, the MGT provided a rostroventral point of access allowing drainage of the LC, with no obvious iatrogenic damage. In study 2, the MGT permitted lavage of the entire GP in three healthy horses and one horse with mild GP empyema. The only major complication was development of emphysema of the lateral wall of one LC, with secondary collapse of the mucous membrane. The time for secondary wound healing was 12-14 days. The MGT can be performed safely in standing horses and may be of value in providing access for lavage and drainage in horses with mild GP empyema.

[Study of morphological alterations in pharyngeal ostium of Eustachian tube and its surrounding tissue and its association with SOM]

OBJECTIVE

To observe the morphological alterations in pharyngeal ostium of Eustachian tube and its surrounding tissues and its correlation with secretory otitis media.

METHOD

72 volunteers (144 ears) as control group, 89 patients (151 ears) as SOM group, all were observed for the shape of pharyngeal opening of auditory tube and the morphological changes of its surrounding structures.

RESULT

Statistic difference was found between the shape of pharyngeal ostium of eustachian tube of adult patients with SOM and that of control group, but for children, there was no difference. It indicated that there was a difference between adult and children in morphological changes of pharyngeal ostium of eustachian tube when suffered from SOM.

CONCLUSION

Morphological changes of pharyngeal ostium of eustachian tube play an important role in the genesis and development of adult SOM . The primary change in children patients is the inflammation of nasopharynx, then is the hypertrophy of adenoid and tubal tonsil. Nasopharyngeal-fibroscope is a very useful tool in the diagnosis and treatment of SOM.

Measurement of Angle and Length of the Eustachian Tube on Computed Tomography Using the Multiplanar Reconstruction Technique

OBJECTIVE

To compare the anatomic features of the eustachian tube (ET) between children with and without otitis media with effusion (OME) and with adults.

METHODS

The angle and length of the ET in children with OME (54 ears, OME children) and without OME (50 ears, normal children), as well as those of normal adults (90 ears), were measured on computed tomography using the multiplanar reconstruction technique.

RESULTS

The angles of ET in the OME children group, the normal children group, and the normal adult group were 20.4 +/- 3.5 degrees and 21.2 +/- 4.8 degrees , 19.9 +/- 3.4 degrees and 20.0 +/- 3.6 degrees , and 27.3 +/- 2.7 degrees and 27.3 +/- 2.8 degrees on the right and the left sides, respectively. There was no significant difference between the right and the left side in any group (P = .541, P = .952, P = .978). The lengths of ET in the OME children group, the normal children group, and the normal adult group were 37.2 +/- 3.0 mm (mean +/- SD) and 37.6 +/- 3.2 mm, 37.5 +/- 3.3 mm and 38.0 +/- 3.2 mm, and 42.5 +/- 2.8 mm and 42.9 +/- 2.9 mm on the right and the left sides, respectively. There was no significant difference between the right and left sides in any group (P = .670, P = .597, and P = .545). Both the angles and lengths were significantly greater in the normal adult group than in either the OME children group or the normal children group (one-way analysis of variance and Fisher's protected least significant difference tests, P < .05), but there was no significant difference in either the angle or length of the ET between the OME and normal children groups (P > .05). In the OME and normal children groups, the angle was observed to constantly increase with age, and the values were found to be within the range of the adult size in all the patients older than 7.5 years and 7.7 years in the OME children group and the normal children group, respectively. As well as the angle, the lengths were observed to constantly increase with age, but the increase appeared to be greater at a younger age (until approximately 3 to 4 years) than at an older age, and the values were found to be within the range of the adult size in all the patients older than 6.8 years and 7.7 years in the OME children group and the normal children group, respectively.

CONCLUSION

The angle and length of the ET are more horizontal and shorter in infants than in adults. However, there is no statistical difference between the angle and length of the ET in infants with and without OME. These results lead us to believe that a short and horizontal ET may not be a main etiologic factor related to high susceptibility to OME in infants and children.

CONTRAST-ENHANCED COMPUTED TOMOGRAPHIC IMAGING OF THE AUDITORY TUBE IN MESATICEPHALIC DOGS

Computed tomography after contrast medium injection was performed in three mesaticephalic canine cadavers to image the auditory tube. Cadavers were positioned in lateral recumbency for imaging. A myringotomy incision was made in the left tympanic membrane of each dog, and contrast medium was infused into the ear canal and middle ear through a balloon-tip catheter. With this method, contrast medium filled the left bulla and auditory tube in all three cadavers. Computed tomography following contrast medium injection was effective for evaluation of the canine auditory tube. Future studies are required to determine the usefulness, as well as the safety, of this procedure in the evaluation of the auditory tube in other breeds of dogs as well as dogs with otitis

Aeration of Prussak's Space Is Independent of the Supradiaphragmatic Epitympanic Compartments

HYPOTHESIS

This study's aim was to find out how well various microdissection approaches reveal the basic anatomy of the epitympanum, especially the pathways of aeration to Prussak's space, without the help of serial sections, which many find difficult to interpret.

BACKGROUND

The basic studies where made during the latter half of the 19th and the first half of the 20th century. Conflicting concepts have later been published, and doubtful information has been included even in textbooks.

METHODS

We have studied 145 temporal bones via microdissection to record the state of the soft tissue structures of the epitympanum, particularly upon Prussak's space with its boundaries. A normal surgical otomicroscope was used in the evaluation, and the findings were recorded via black and white and/or color photography; for recent cases, a digital video camera was used.

RESULTS

The epitympanic diaphragm separates the large upper floor compartments from the small, laterally placed lower floor unit. The latter consists of Prussak's space and the posterior pouch, at times also of the lower lateral attic. The tympanic isthmus connects the upper unit to the medial tympanum. Defects in the diaphragm create additional airways to the upper unit, in 29% via the tensor fold and in 19% via the lateral incudomalleal fold. In only 7% was there a small opening in the roof of Prussak's space connecting it to the upper unit. Effective aeration of Prussak's space was independent of the upper floor compartments.

CONCLUSION

Microdissection is a reliable and sufficient method for teaching epitympanic anatomy. All important structures can be identified and defects in the epitympanic diaphragm verified. Data obtained via serial sections are invaluable in research but not essential in the training of ear surgeons. The two-floor structure of the epitympanum with an independent aeration of the two units should be the starting point for all anatomy teaching.

Guttural pouches, brain temperature and exercise in horses

Selective brain cooling (SBC) is defined as the lowering of brain temperature below arterial blood temperature. Artiodactyls employ a carotid rete, an anatomical heat exchanger, to cool arterial blood shortly before it enters the brain. The survival advantage of this anatomy traditionally is believed to be a protection of brain tissue from heat injury, especially during exercise. Perissodactyls such as horses do not possess a carotid rete, and it has been proposed that their guttural pouches serve the heat-exchange function of the carotid rete by cooling the blood that traverses them, thus protecting the brain from heat injury. We have tested this proposal by measuring brain and carotid artery temperature simultaneously in free-living horses. We found that despite evidence of cranial cooling, brain temperature increased by about 2.5 degrees C during exercise, and consistently exceeded carotid temperature by 0.2-0.5 degrees C. We conclude that cerebral blood flow removes heat from the brain by convection, but since SBC does not occur in horses, the guttural pouches are not surrogate carotid retes.

What is new in otitis media?

The "wait and see" approach in acute otitis media (AOM), consisting of postponing the antibiotic administration for a few days, has been advocated mainly to counteract the increased bacterial resistance in respiratory infections. This approach is not justified in children less than 2 years of age and this for several reasons. First, AOM is an acute inflammation of the middle ear caused in about 70% of cases by bacteria. Redness and bulging of the tympanic membrane are characteristic findings in bacterial AOM. Second, AOM is associated with long-term dysfunction of the inflamed eustachian tube (ET), particularly in children less than 2 years of age. In this age group, the small calibre of the ET together with its horizontal direction result in impaired clearance, ventilation and protection of the middle ear. Third, recent prospective studies have shown poor long-term prognosis of AOM in children below 2 years with at least 50% of recurrences and persisting otitis media with effusion (OME) in about 35% 6 months after AOM. Viruses elicit AOM in about 30% of children. A prolonged course of AOM has been observed when bacterial and viral infections are combined because viral infection is also associated with ET dysfunction in young children. Bacterial and viral testing of the nasopharyngeal aspirate is an excellent tool both for initial treatment and recurrence of AOM. Antibiotic treatment of AOM is mandatory in children less than 2 years of age to decrease inflammation in the middle ear but also of the ET particularly during the first episode. The best choice is amoxicillin because of its superior penetration in the middle ear. Streptococci pneumoniae with intermediary bacterial resistance to penicillin are particularly associated with recurrent AOM. Therefore the dosage of amoxicillin should be 90 mg/kg per day in three doses. In recurrent AOM with beta-lactamase-producing bacilli, amoxicillin should be associated with clavulanic acid at a dose of 6.4 mg/kg per day. The duration of the treatment is not established yet but 10 days is reasonable for a first episode of AOM. OME may be a precursor initiating AOM but also a complication thereof. OME needs a watchful waiting approach. When associated with deafness for 2-3 months in children over 2 years of age, an antibiotic should be given according to the results of the bacterial resistance in the nasopharyngeal aspirate. The high rate of complications of tympanostomy tube insertion outweighs the beneficial effect on hearing loss. The poor results of this procedure are due to the absence of effects on ET dysfunction. Pneumococcal vaccination has little beneficial effects on recurrent AOM and its use in infants needs further studies. Treatment with amoxicillin is indicated in all children younger than 2 years with a first episode of AOM presenting with redness and bulging of the tympanic membrane. Combined amoxicillin and clavulanic acid should be given in patients with beta-lactamase-producing bacteria. The duration of treatment is estimated to be at least 10 days depending on the findings by pneumo-otoscopy and tympanometry. Bacterial and viral testing of the nasopharyngeal aspirate is highly recommended particularly in children in day care centres as well as for regular follow-up. The high recurrence rate is due to the long-lasting dysfunction of the eustachian tube and the immune immaturity of children less than 2 years of age.

Laser interferometry measurements of middle ear fluid and pressure effects on sound transmission

An otitis media with effusion model in human temporal bones with two laser vibrometers was created in this study. By measuring the displacement of the stapes from the medial side of the footplate, the transfer function of the middle ear, which is defined as the displacement transmission ratio (DTR) of the tympanic membrane to footplate, was derived under different middle ear pressure and fluid in the cavity with a correction factor for cochlear load. The results suggest that the DTR increases with increasing frequency up to 4k Hz when the middle ear pressure was changing from 0 to 20 or -20 cm H20 (e.g., +/-196 daPa) and fluid level was increasing from 0 to a full middle ear cavity. The positive and negative pressures show different effects on the DTR. The effect of fluid on DTR varies between three frequency ranges: f < 1k, between 1k and 4k, and f > 4k Hz. These findings show how the efficiency of the middle ear system for sound transmission changes during the presence of fluid in the cavity and variations of middle ear pressure.

Eustachian Tube Function and the Middle Ear

Eustachian tube dysfunction has been linked to causing middle ear pathology. One of the sequelae seen is tympanic membrane retraction. Concern occurs when this physiological state becomes chronic, leading to adhesive otitis media followed by debris collection and fulminate cholesteatoma. This chapter explores the role the eustachian tube plays in regulating middle ear and mastoid aeration, the causes of eustachian tube dysfunction, and the treatment of this disorder.

Autophony in Patients with Patulous Eustachian Tube

OBJECTIVE

To investigate the contribution of anatomical factors, such as the caliber of the patent eustachian tube (ET) and the volume of the middle ear cavity, on vocalized sound transmission to the inner ear.

METHODS

Model experiment using artificial middle ear.

RESULTS

In the present model experiment, sound transmission from the pharynx to the inner ear under patulous conditions was affected by the caliber of the ET and by the mastoid volume, especially in the low-frequency region, that is, a larger caliber of the ET and smaller mastoid volume resulted in greater sound transmission from the pharyngeal space to the inner ear.

CONCLUSION

Patulous symptoms may be more distressful in patients with poorly developed mastoid cavity than in those with well-aerated mastoid under similar conditions of patulous ET.

Endoscopic examination of the eustachian tube: a step-by-step approach

OBJECTIVE

The aim of this study was to develop a step-by-step approach for endoscopic examinations of the eustachian tube on awake patients and to report anatomic and functional findings.

STUDY DESIGN

Prospective study.

SETTING

University hospital.

PATIENTS

Convenience sample of seven individuals without a history of ear disease.

INTERVENTION

Diagnostic transnasal-transpharyngeal videoendoscopy of the eustachian tube with 30- and 70-degree rigid Hopkins rod endoscopes, 2.5- and 0.8-mm, 0-degree flexible fiber endoscopes performed under local anesthesia in 12 eustachian tubes.

MAIN OUTCOME MEASURES

Utility of the various endoscopes for the diagnosis in the different parts of the eustachian tube; quality of vision and the patient's comfort during the procedure.

RESULTS

The 2.5-mm flexible endoscope was most useful for examination of the pharyngeal ostium and the cartilaginous lumen of the tube. The isthmus region could only be passed using an 0.8-mm fiberscope. In all cases, it was possible to insert the endoscope into the middle ear cavity. Eleven of the 12 tube examinations showed normal findings. The mobility of the tubal cartilage could be visualized with sufficient quality. In 50% of all examinations, application of local anesthesia via a tube catheter was necessary to make the procedure tolerable.

CONCLUSION

The presented approach allows an assessment of both anatomic and functional changes to the eustachian tube in awake patients. The assessment of middle ear structures is limited. To ensure a comfortable and safe procedure, the use of topical anesthesia in a supine position and, in certain cases, additional anesthesia via eustachian tube catheter is recommended.

Sectional anatomy of auditory tube

BACKGROUND AND PURPOSE

The auditory tube connects the tympanic cavity with nasopharynx. Due to its structure and position it is difficult to demonstrate the auditory tube in its whole length, and to study its topography on anatomical specimens. The purpose of our study was to present sectional anatomy of auditory tube in order to facilitate understanding of its structure and topography.

MATERIALS AND METHODS

We utilised serial sections of cadaveric head in four planes: transverse, oblique, frontal and sagittal.

RESULTS

The osseous part of the auditory tube was demonstrated on transverse sections, and most of the cartilaginous part on oblique sections of head and neck. The tensor veli palati muscle was found to consist of bilaminar muscle sheet: the outer part originating from the skull base and the inner part originating from lateral cartilaginous lamina and membranous part of the tube. Topographic relations seen on four section planes were described in detail.

CONCLUSION

The structure, course and topography of auditory tube are well demonstrated on sectional images. Detailed knowledge of sectional anatomy of the auditory tube is important for interpretation of corresponding computerised tomographic and magnetic resonance images, and in understanding the disorders and diseases affecting middle ear and mastoid.

Variations in the tensor veli palatini muscle with special reference to its origin and insertion

OBJECTIVE

Previous research on the tensor veli palatini muscle (TVP) has produced conflicting descriptions of its functions and topographical relationships with other orofacial structures. The goal of this study was to describe the morphology of the TVP in a systematic and comprehensive manner.

METHODS

One hundred nineteen sides of 77 human heads from donated cadavers were partially dissected under a binocular microscope. Histological examination of the hard tissue-muscle interfaces was also undertaken.

RESULTS

There were two adjacent origins of the TVP: the cranial base origin (CB origin) and the auditory tube cartilage origin (AT origin). The CB origin always lay anterior to the AT origin and there was no septum or loose tissue between the two muscular laminae leading from these origins. The muscle fibers converged on a central tendinous plate in the muscle belly, which gradually became a common tendon that rounded the pterygoid hamulus before inserting into the palatine aponeurosis. Notably, secondary insertions were found on the maxillary tuber (33.6%) and/or in the submucosal tissue near the palatoglossal arch (37.8%). Maxillary insertions were almost exclusively associated with an AT origin that was wide as or wider than the CB origin. Histological observations confirmed that the hamulus acted purely as a pulley and suggested that a connecting band to the tensor tympani had no or few functions of an intermediate tendon.

CONCLUSIONS

The TVP appears to act as the dilator tubae and that this function can be maintained by preserving or reconstructing the maxillary insertion during push-back surgery, even if hamulotomy is necessary.

Finite element analysis of active Eustachian tube function

The inability to open the collapsible Eustachian tube (ET) has been related to the development of chronic otitis media. Although ET dysfunction may be due to anatomic and/or mechanical abnormalities, the precise mechanisms by which these structural properties alter ET opening phenomena have not been investigated. Previous investigations could only speculate on how these structural properties influence the tissue deformation processes responsible for ET opening. We have, therefore, developed a computational technique that can quantify these structure-function relationships. Cross-sectional histological images were obtained from eight normal adult human subjects, who had no history of middle ear disease. A midcartilaginous image from each subject was used to create two-dimensional finite element models of the soft tissue structures of the ET. ET opening phenomena were simulated by applying muscle forces on soft tissue surfaces in the appropriate direction and were quantified by calculating the resistance to flow (Rv) in the opened lumen. A sensitivity analysis was conducted to determine the relative importance of muscle forces and soft-tissue elastic properties. Muscle contraction resulted in a medial-superior rotation of the medial lamina, stretching deformation in the Ostmann's fatty tissue, and lumen dilation. Variability in baseline Rv values correlated with tissue size, whereas the functional relationship between Rv and a given mechanical parameter was consistent in all subjects. ET opening was found to be highly sensitive to the applied muscle forces and relatively insensitive to cartilage elastic properties. These computational models have, therefore, identified how different tissue elements alter ET opening phenomena, which elements should be targeted for treatment, and the optimal mechanical properties of these tissue constructs.

Relationship of petrous temporal bone pneumatization to the eustachian tube lumen

OBJECTIVES/HYPOTHESIS

Objectives were to determine the incidence of petrous apex pneumatization and to define the relationship between a pneumatized petrous temporal bone and the eustachian tube lumen.

STUDY DESIGN

Retrospective study with institutional review board approval including only adult patients.

METHODS

One hundred head computed tomography (ct) scans and 204 petrous temporal bone CT scans performed at a tertiary teaching hospital were reviewed. The two senior authors (s.h.s., p.c.s.) independently reviewed the petrous temporal bone CT scans for grade of pneumatization. Pneumatized CT scans were then reviewed for the presence of a direct communication with the eustachian tube lumen. Significance was determined using the chi test and Pearson correlation of ranks.

RESULTS

The incidence of peritubal cells opening into the eustachian tube anterior to the tympanic orifice was 92%.

CONCLUSION

The direct communication of peritubal cells with the bony eustachian tube may play a role in the development of persistent cerebrospinal fluid rhinorrhea after cerebellopontine angle surgery.

Postnatal change on the location of Ostmann's fatty tissue in the region lateral to Eustachian tube

OBJECTIVE

To delineate a possible role of protective function by Ostmann's fatty tissue (OF) in the lateral region to Eustachian tube (ET).

STUDY DESIGN

Morphometric and histopathological examination on human temporal bones.

METHODS

OF in the region lateral to the cartilaginous portion of the ET between the ET lumen and the tensor veli palatini muscle (TVP) was studied histopathologically and morphometrically by analyzing a series of vertically cut histologic sections for the ET structures. Sections were obtained from 25 individuals with age ranging from 33 gestational weeks to 38 years at the time of their death.

RESULTS

In fetus and neonates, the region lateral to ET was filled with mesenchyme. OF appeared first in this region at 2-3 weeks postnatally, and increased in volume with development of the ET. In the cases of older children and adults (Group-B), the ratio of the volume of OF in the region to that of ET lumen (OF/L) was significantly higher in the posterior half than in the anterior half of the cartilaginous portion of ET. However, in the cases of infants and younger children (Group-A), there was no significant difference in the ratio between the two regions. In the posterior half of the cartilaginous portion of ET, OF/L was significantly higher in Group-B than in Group-A, while in the anterior half, there was no significant difference in the ratio between two age groups (Group-A and B).

CONCLUSIONS

In Group-B, the dominant OF in the area of the posterior half of the cartilaginous region, which includes the narrowest portion of ET, may be responsible for restoring the ET lumen back to its closed static condition after active tubal opening by contraction of TVP. This is thought to be important for protection of the middle ear. On the other hand, in Group-A, poor OF near the narrowest portion of ET may cause insufficient restoration of the ET lumen and increased risk of developing otitis media (OM).

Relevance of the pharyngotympanic tube

The auditory (Eustachian) tube connects the middle ear with the nasopharynx. This conduit permits equalisation of pressure between the middle ear and the throat. Balanced pressure allows the eardrum to vibrate freely as sound waves strike it. The auditory tube is also a potential anatomical route whereby opportunistic pathogens may migrate from the nose and throat to the middle ear. Eustachian tube (ET) function is disturbed in children with cleft palate, thereby rendering them susceptible to chronic otitis media with effusion (OME) and temporary conductive deafness. ET obstruction follows in these patients, and is thought to be related to the inability of the tensor veli palatini (TVP) to function properly. This anatomical overview reviews the clinical importance of the ET in the normal population and children with cleft palate.

Postnatal changes in the connective tissue in the region lateral to the eustachian tube: possible relationship to tube function

In order to delineate the possible role of connective tissue (CT) in the region lateral to the eustachian tube (ET) between the ET lumen and the tensor veli palatini muscle (TVPM), we studied the postnatal changes in the CT in histologic sections of human ET. In fetuses and neonates, the lateral region was filled with mesenchyme. Loose collagenous CT appeared first at 2 weeks of age, and in subjects older than 4 years of age, the collagen formed dense, meshlike structures attaching to both the subepithelial CT layer of the ET and the tendonlike membrane of the TVPM. Along the long axis of the ET, those attachments were distributed mainly in the region at the posterior part of the cartilaginous portion of the ET. Attachments to the subepithelial CT layer of the ET were distributed mainly in the upper half of the region. The dense, meshlike collagenous CT might help the ET to be opened by drawing the lateral wall of the ET lumen through inferolateral movement of the tendonlike membrane of the TVPM when the TVPM contracts. It may work to open mainly the parts that include the narrowest portion of the ET, and also the upper aspect of the ET lumen. Incomplete development of this structure in infants may be one of the factors associated with dysfunction in ET opening.

Difference in attachment of the tensor veli palatini muscle to the eustachian tube cartilage with age

To test a hypothesis that ventilation of the eustachian tube (ET) varies with age, we investigated the relationship between age and the attachment of the tensor veli palatini muscle (TVPM) to the lateral lamina of the ET cartilage in 12 normal human temporal bones obtained from individuals 3 months to 81 years old. We used computer-aided 3-dimensional reconstruction and measurement methods. We found that the length of the TVPM attachment and its ratio to the length of the ET, especially that of the cartilaginous portion of the ET, increases with age from infancy to adulthood, and decreases with age from young adulthood to later life. These findings are thought to be related to postnatal development and aging. The possibility of differences in ventilation function with age is discussed.

Diseases of the guttural pouches

Guttural pouches are unique anatomic structures in Equidae. Conditions affecting the guttural pouches present with clinical signs that are not observed in other domestic species, and treatment of some of these conditions can be challenging. This article describes the anatomy and examination of the guttural pouches and reviews the presenting signs and treatment of the more common conditions affecting them, including empyema, tympany, mycosis, and stylohyoid arthropathy.

Functional anatomy of the tensor veli palatini muscle and Ostmann's fatty tissue

This study examined morphological features of the tensor veli palatini muscle (TVPM) and Ostmann's fatty tissue that may be important for eustachian tube (ET) ventilation. Histologic sections through the midcartilaginous ET from 17 human temporal bone-ET specimens (age range. 3 months to 88 years) were used to assess 1) the presence or absence of attachment of the TVPM fibers to either the perichondrium of the ET cartilage lateral lamina (LL) or a tendinous membrane along the medial margin of the TVPM, 2) the angular relationship between the TVPM fibers and the vertical axis of the ET lumen, and 3) the location of the TVPM and Ostmann's fatty tissue. The TVPM fibers were attached to the LL perichondrium in 14 cases; an attachment was absent in 3 cases because of fatty atrophy of the TVPM. However, the TVPM fibers were inserted into the tendonlike membrane in all cases. The angle of insertion of TVPM fibers into the membrane was significantly more acute (relative to the vertical ET axis) in the inferior aspect than in the superior aspect of the membrane both in young children (3 months to 4 years; mean +/- SD, 39.0 degrees +/- 15.1 degrees superiorly to 23.8 degrees +/- 17.0 degrees inferiorly) and in older subjects (8 to 88 years, 30.4 degrees +/- 11.6 degrees superiorly to 15.7 degrees +/- 11.2 degrees inferiorly; t-test, p < .001). The location of Ostmann's fatty tissue accompanied the TVPM throughout the cartilaginous ET. These data suggest that contraction of the TVPM moves the LL inferolaterally to open the superior aspect more than the inferior aspect of the lumen and that Ostmann's fatty tissue will limit the opening of the ET lumen, especially that of its inferior aspect.

The muscular compliance of the auditory tube: a model-based survey

OBJECTIVES

The role of the paratubal muscles, especially the medial pterygoid muscle, still is unclear. The aim of this study was to define the function of the medial pterygoid muscle concerning the muscular compliance of the auditory tube.

METHODS

High-resolution cross-sectional T1 magnetic resonance imaging data of one of the authors' paratubal structures were used, a new functional 3-D model of the auditory tube and its related structures visualized by the Hamburg VOXEL-MAN digital image system.

RESULTS

Functional 3-D reconstructions of the paratubal structures reveal that the medial pterygoid muscle is acting as a movable hypomochlion of the tensor veli palatini muscle. Contraction of the medial pterygoid muscle increases and relaxation decreases the force of the tensor veli palatini muscle on the distal part of the auditory tube. Hence, the opening pressure of the auditory tube is moderated by the action of the medial pterygoid muscle.

CONCLUSION

The influence of the medial pterygoid muscle on the opening pressure of the auditory tube may have an impact on the diagnosis and therapy in patients with patent auditory tube as well as the middle ear pathology in patients with cleft palate.

The eustachian tube. Update on anatomy, development, and function

Central to many pathologic conditions affecting the middle ear is the failure of the ET to perform its functions of regulation of middle ear pressure, clearance of middle ear secretions, and protection of the middle ear space. Recent advances in radiologic imaging and fiberoptic endoscopes have allowed a more detailed description of the structure and function of this area. Hopefully, with the knowledge gained from advances in this area, more effective medical treatment options for common otologic problems, such as otitis media, will become available.

Anomaly of the eustachian tube and its associated structures in patients with multiple congenital malformation: a histopathological and morphometric study

Two temporal bone-eustachian tube (ET) specimens; one from a 1-day-old female newborn with Townes Syndrome (Case 1) and the other from a 15-year-old female with oral-facial-digital syndrome (Case 2) were studied histopathologically and morphometrically. Both specimens had anomalies of the ET and its associated structures as compared with eight age-matched control cases without anomaly (six cases for Case 1 and two cases for Case 2, respectively). Case 1 had a weak attachment of the tensor veli palatini muscle (TVPM) to a poorly developed lateral lamina (LL) of the ET cartilage, a large voluminous medial lamina (ML) of the ET cartilage, a small voluminous ET lumen with a few ridges of mucosal folds, poorly developed ET glands and a poorly developed levator veli palatini muscle (LVPM). Case 2 had a short and longitudinally elongated ET lumen that was insufficiently covered with a poorly developed ML and LL and an aberrant course of the LVPM. Both cases were accompanied by a mild inner ear anomaly (slightly shortened cochlea). We discuss the implications of the observed anomalies with regard to functional and clinical issues. In particular, we speculate that these ET anomalies may closely be related to potential ET dysfunction with high susceptibility to otitis media.

Functional anatomy of levator veli palatini muscle and tensor veli palatini muscle in association with eustachian tube cartilage

The anatomic relationships among the levator veli palatini muscle (LVPM), the tensor veli palatini muscle (TVPM), and the eustachian tube (ET) cartilage were investigated by computer-aided 3-dimensional reconstruction and measurement methods. The study used 13 normal temporal bone-ET specimens obtained from 13 individuals (range of age at death, 3 months to 88 years). This study revealed several anatomic features of the anterior cartilaginous portion of the ET. First, the LVPM is always located inferolateral to the inferior margin of the medial lamina (ML) of the ET cartilage. Second, the LVPM has a large cross-sectional area throughout the extent of the anterior cartilaginous portion of the ET. Third, although the LVPM lies close to the ML of the ET cartilage (0.44+/-0.16 mm in children and 1.02+/-0.58 mm in adults), there is no region of attachment. Finally, the TVPM is not attached to the lateral lamina (LL) of the ET cartilage of the anterior quarter of the cartilaginous portion. Accordingly, it could be assumed that the most anterior cartilaginous portion of the ET is opened primarily by the contraction of the LVPM, which causes a superior-medial rotation of the ML. Furthermore, since the contraction time of the LVPM is reported to be longer than that of the TVPM, the anterior cartilaginous portions of the ET may remain open, even after the middle to posterior cartilaginous portions are closed after relaxation of the TVPM. This process would produce a pumping action of the ET in the direction from the middle ear to the pharyngeal side. The pumping function may be beneficial to clearance of the middle ear.

Do the tensor tympani and tensor veli palatini muscles of man form a functional unit? A histochemical investigation of their putative connections

The discussion among anatomists and otolaryngologists about the muscles originating from the Eustachian tube and the connections between the tensor tympani and tensor veli palatini muscles started in the 1860s. From then on, a considerable number of contradictory hypotheses and data have been presented. However, before discussing whether or not these two muscles form a functional unit, interest should focus on the question of whether it is even possible. The cartilaginous portion of the Eustachian tube with all muscles originating from it, including the whole tensor tympani muscle, was dissected from five perfusion-fixed cadavers and removed in toto. Complete longitudinal serial sections of 10 microm were made in the axis of the tensor tympani muscle. Sections were alternatingly stained according to Cason's and Maskar's techniques. The macroscopic aspect (under the operating microscope) of a tendinous connection between the two muscles under consideration could be proven by the histochemical methods used in all cases. Based on our findings and the literature reviewed we are convinced that the tensor tympani and tensor veli palatini muscles of man constitute a functional unit. This represents an important step forward towards the understanding of the possible functions the tensor tympani muscle serve in man.

Estimated locations of the narrowest portion of the eustachian tube lumen during closed and open states

To morphologically evaluate the location of the narrowest portion of the eustachian tube (ET) lumen during closed and open states, we used computer-assisted 3-dimensional reconstruction methods to investigate 13 normal human temporal bone–ET specimens obtained from 13 individuals 3 months to 81 years old. On the basis of recent endoscopic observations, we assumed that the site of minimum circumference of the ET lumen represents the site of minimum cross-sectional area during the open state. We tested the hypothesis that the location of the narrowest site of the ET lumen in the closed state is not identical to the site of minimum circumference of the ET lumen. Confirmation of this hypothesis would imply that the site of greatest constriction shifts with contraction of the tensor veli palatini muscle. In 11 of 13 cases, both the site of minimum cross-sectional area and the site of minimum circumference of the ET lumen were located in the cartilaginous portion of the ET, near the anterior margin of the junctional portion. In the 2 remaining cases, the site of minimum circumference was located in the junctional portion of the ET, whereas the site with the narrowest cross-sectional area stayed in the cartilaginous portion. The site of minimum circumference shifted significantly in the direction of the tympanic orifice of the ET, relative to the site of minimum cross-sectional area (p < .01). The average distance between these sites was 2.01 ± 1.75 mm. There was no significant difference between children (n = 6) and adults (n = 7). The so-called isthmus portion of the ET, located between the cartilaginous and bony portions, has been considered traditionally as the narrowest site through the entire ET. However, our results suggest that the narrowest portion of the ET lumen is located in the cartilaginous portion in both closed and open states.

[The thin sectional anatomy and MRI of the eustachian tube]

OBJECTIVE

To provide the sectional anatomic data for clinical imaging diagnosis of the eustachian tube.

METHOD

9 cadaver eustachian tube were sectioned on transverse, coronal and sagittal planes using plastination, comparing with the MRI of the eustachian tube.

RESULT

The coronal and transversal images clearly delineates the anatomical details of the eustachian tube and its fascia and muscles and their relationship, the fibrocartilaginous tube is posteromedial; its upper margin is curled outward to form the roof of the cartilaginous tube. Anteriorly and laterally, the eustachian tube is closed by the salpingopharyngeal fascia extending along the inferior surface of the eustachian tube to or its floor. The tensor veli palatini anterolateral and the levator veli palatini muscle posterolateral and inferior. The submucosal fascia is medial to the levator veli palatini muscle, the pharyngobasilar fascia is between the tensor and levator veli palatini muscles; the fascia of Weber Liel is lateral to the tensor veli palatini muscle.

CONCLUSION

The cartilaginous portion, muscle and fascia of the eustachian tube could be displayed clearly on MRI. The thin sections of the eustachian tube can be directly compared with the MR images, providing valuable information to image diagnosis of the nasopharyngeal diseases.

Surfactant proteins A and D in Eustachian tube epithelium

Surfactant protein (SP) A and SP-D are collectins that have roles in host defense. The Eustachian tube (ET) maintains the patency between the upper airways and the middle ear. Dysfunction of local mucosal immunity in ET may predispose infants to recurrent otitis media. We recently described preliminary evidence of the expression of SP-A and SP-D in the ET. Our present aim was to establish the sites of SP-A and SP-D expression within the epithelium of the ET in vivo. With in situ hybridization, electron microscopy, and immunoelectron microscopy, the cells responsible for SP-A and SP-D expression and storage were identified. SP-A expression was localized within the ET epithelium, and the protein was found in the electron-dense granules of microvillar epithelial cells. Being concentrated in the epithelial lining, only a few cells revealed intracellular SP-D, and it was not associated with granules. The SP-A and SP-D immunoreactivities in ET lavage fluid, as shown by Western blot analyses, were similar to those in bronchoalveolar lavage fluid. We propose that there are specialized cells in the ET epithelium expressing and secreting SP-A and SP-D. SP-A and SP-D may be important for antibody-independent protection of the middle ear against infections.

The genetics of otitis media

There is significant evidence from epidemiologic, anatomic, physiologic, and immunologic studies that susceptibility to recurrent episodes of acute otitis media (OM) and persistent OM with effusion is largely genetically determined. The genetics of OM are most likely complex, i.e., many genes are probably contributing to the overall phenotype. The knowledge of a hereditary component has important implications because closer surveillance of children at risk for OM could result in earlier detection and treatment. Further, once OM susceptibility genes have been identified it may be possible to develop molecular diagnostic assays that could enable the clinician to identify the child at high risk for OM and to develop more focused treatments in the future.