Cineroentgenographic and electromyographic studies of Eustachian tube function

Magnetic Resonance Imaging of the Eustachian Tube and the Paratubal Structures in Patients with Unilateral Acquired Cholesteatoma

OBJECTIVES

This study aimed to compare the Eustachian tube (ET) and the paratubal structures between the two sides in subjects with unilateral acquired cholesteatoma and a healthy contralateral ear to determine if there are anatomical differences.

MATERIALS AND METHODS

Of the 217 patients with cholesteatoma evaluated, 36 patients with unilateral cholesteatoma were included in the study. All of the patients had a healthy contralateral ear with no history of surgery. Nine different paratubal parameters were measured through contrast-enhanced magnetic resonance imaging (MRI). The measurements of the ear with cholesteatoma were compared with those of the healthy ear.

RESULTS

The bimucosal thickness of the ET lumen, the mucosal thickness of the pharyngeal orifice, the lengths and diameters of the tensor veli palatini muscle and the levator veli palatini muscle, the diameter of the pharyngeal orifice of the ET, the diameter of the lateral pharyngeal recess mucosal thickness, and the diameter between the posterior border of the inferior nasal concha and the pharyngeal orifice of the ET were measured in MRI scans. No statistically significant difference was observed between the healthy ear and the ear with cholesteatoma for any of the parameters measured (p>0.05).

CONCLUSION

We did not observe any anatomical differences in the measurements of the ET and the paratubal structures on MRI scans. Although ET dysfunction is considered to be the leading etiologic factor in acquired cholesteatoma, the ET and the paratubal structures may not exhibit an anatomic difference between the ear with cholesteatoma and the healthy contralateral ear.

Functional evaluation of paratubal muscles using electromyography in patients with chronic unilateral tubal dysfunction

Eustachian tube dysfunction is closely related to the development of otitis media and result from several factors including inflammation within the nasal cavity and nasopharynx, adenoid hypertrophy, cleft palate and nasopharyngeal carcinoma. To some extent, eustachian tube dysfunction may be related to weakness of the paratubal muscles, such as the tensor veli palatini and levator veli palatini muscles. The aim of the study is to find out myogenic factors in eustachian tube dysfunction using electromyography (EMG), and to evaluate the clinical feasibility of EMG. Ten patients with unilateral eustachian tube dysfunction were included in this study. The healthy side of each patient was used as a control. EMG tests on paratubal muscles were conducted under the view of a 30° endoscope or fiberoptic laryngoscope. EMG on the tensor veli palatini showed decreased amplitudes on the affected side in one patient during phonation. EMG on the levator veli palatini showed decreased amplitudes on the affected side in two patients during both deglutition and phonation, one patient during phonation only, and two patients during deglutition only. The only patient who had decreased amplitude on EMG of the tensor veli palatini also had decreased amplitude on EMG of the levator veli palatini. In conclusion, although it is generally accepted that the tensor veli palatini plays a major role in opening the eustachian tube, reduced activity of the levator veli palatini may be related to eustachian tube dysfunction. When assessing eustachian tube function, EMG is useful for evaluating myogenic factors.

Timing of tensor and levator veli palatini force application determines eustachian tube resistance patterns during the forced-response test

OBJECTIVES

The forced-response test (FRT) is used to assess eustachian tube (ET) function in patients with middle ear disease (otitis media). This test often documents a dynamic pattern of luminal dilation and constriction during swallowing which can be quantified as a function relating active tubal resistance with time. The goal of this study is to use a generalized finite element model (FEM) to test the hypothesis that the relative timing of muscle force application by the tensor veli palatini muscle (mTVP) and levator veli palatini muscle (mLVP) on the ET determines the form of active resistance functions.

METHODS

Seven resistance waveforms were obtained during the FRT in five adult subjects. A 2D FEM of the ET was constructed from an adult histological specimen and viscoelastic tissue mechanical properties were specified based on measurements obtained in each subject. Least-squared regression routines were used to vary the timing and magnitude of mTVP and mLVP force applications to the ET in order to match the active resistance functions recorded during the FRT.

RESULTS

Variation of muscle force timing and magnitude in the FEM simulations reproduced the seven active resistance waveforms with high fidelity. Early application of mTVP force in combination with mLVP force produced a waveform characterized by an initial dilation (low resistances) followed by lumen constriction (higher resistances), while delayed mTVP force application caused an initial lumen constriction followed by dilation.

CONCLUSIONS

These results indicate that the active resistance waveforms observed during the FRT reflect differences in the temporal pattern of mLVP and mTVP force application to the ET and emphasize that, like the mTVP, the mLVP functionally interacts with the ET. Results also indicate that in normal adults contraction of the mLVP promotes lumen constriction and that the initial lumen constriction is highly sensitive to the relative delay timing of mTVP and mLVP force application.

The evaluation of the tensor veli palatini muscle function with electromyography in chronic middle ear diseases

Although there are several factors affecting the pathogenesis of chronic otitis, the pathological process has not been entirely defined yet. One of the theories suggested for the development of middle ear diseases is tubal dysfunction. The aim of the study is to analyze the function of the tensor veli palatini (TVP) muscle electromyographically in chronic middle ear pathologies and to evaluate the role of this muscle in eustachian tube dysfunction and pathogenesis of associated middle ear diseases by comparing with the results of healthy individuals.

STUDY DESIGN

A prospective, controlled, clinical trial. We enrolled 24 patients with chronic middle ear pathologies into our study and 18 controls without any previous ear problem. Electromyographic (EMG) needle was inserted into the TVP muscles in all patients transnasally. Functions of the TVP muscle were analyzed by using the amplitudes of the motor unit potential (MUP) and MUP durations detected on EMG. MUP amplitudes and MUP durations were compared statistically in all groups. When the mean MUP amplitudes and durations obtained from TVP muscles of all ears from the patient group were compared to the mean MUP amplitudes and durations obtained from healthy individuals, no statistically significant difference was observed between sick ears and control ears. Values obtained from the sick ears needed to be compared with mean values obtained from the control group separately, since absence of statistically significant difference cannot mean that we should ignore individual muscle dysfunction. The results we obtained from our study support that in the formation of different middle ear pathologies, myogenic defects in the eustachian tube have limited effects, except for existence of a predisposing factor like palate pathology. In all patients with chronic middle ear disease it is not appropriate to expect functional muscle dysfunction, however evaluation of TVP muscle function correctly may be helpful for bringing up the underlying possible muscle and nerve pathologies not in all patients.

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.

Descriptive anatomy of the human auditory tube

The aim of this study was to correlate current morphologic data relating to the lumen of the auditory tube. Four methods were used: dissection under the operating microscope; microendoscopy of the tubal lumen; optical and electron microscope histology; and MR or CT imaging. The auditory tube consists of two unequal cones, a small posterior third, fixed and osseous (protympanum), and a mobile fibrocartilaginous anterior two-thirds, both joined by the tubal isthmus, a short constriction which is pseudosphincteric at endoscopy. The tensor veli palatini muscle (TVPM) and the levator veli palatini muscle (LVPM) are the chief muscles that vary the tubal lumen of the fibrocartilaginous portion, which is collapsed at rest. CT and especially MR imaging allows their observation in static conditions. Serial histologic sections reveal the continuity between the TVPM and the tensor tympani muscle. The main cartilage framing the lumen varies in shape according to the level surveyed. The tubal mucosa is lined with an epithelium combining ciliated and mucus cells, involved in mucociliary drainage and gas exchanges in the auditory tube. These morphologic elements represent a basis for study of tubal physiology and for planning treatment in dysfunctions of the auditory tube.

Quantitative analysis of gas losses and gains in the middle ear

Quantitative analysis of the amount of gas entering and leaving the middle ear (ME) was performed in patients with central perforation or with ventilating tubes. Patients were divided into a 'balanced pressure group' (BP) where pressure remained close to atmospheric throughout the measuring period and an 'unbalanced pressure group' (UBP) where pressure decreased continuously throughout measurements. The rate of gas gain was 41.0 +/- 19.9 microl/h (mean +/- SD, n = 17) in the BP group, significantly higher than in the UBP group (21.4 +/- 9.6 microl/h, n = 8). The rate of gas loss was 34.8 +/- 17.7 and 36.1 +/- 15.9 microl/h in the BP and UBP groups, respectively. Deglutition frequency was 27 +/- 13.4 deglutition/h in the BP group, significantly higher than the deglutition frequency of the UBP group (16 +/- 8.9 deglutition/h). It seems that the amount of gas entering the ME per deglutition is rather stable and does not change significantly with ME pressure level. Negative ME pressure may result from decreased gas gain rate due to increased intervals between deglutitions and loss of interdependence between the rate of gas entering and leaving the ME.

Middle ear gas composition and middle ear aeration

Partial pressures of the gases in the middle ears of 14 guinea pigs were measured continuously on-line with a specially designed mass spectrometer. The average values were carbon dioxide 67.55 mm Hg, oxygen 48.91 mm Hg, and nitrogen 596.54 mm Hg. These values confirm earlier measurements and show that the gas composition of the middle ear differs basically from that of air and resembles that of venous blood. These findings are indicative of bilateral diffusion between the middle ear cavity and the blood. We propose that under physiologic as well as under pathologic (ie, atelectatic) conditions, the gas content of the middle ear is also controlled by diffusion. This mechanism fits well with the fluctuating character of atelectatic ears. Thus, a negative middle ear pressure could be secondary to excessive loss of gases through increased and excessive diffusion, although additional mechanisms are probably also involved. A likely contributing factor is poor pneumatization of the mastoid, with consequent absence of a physiologic pressure regulation mechanism by its pneumatic system.