Utricular and saccular volumetry in human temporal bones

Brazilian Society of Otology task force - Otosclerosis: evaluation and treatment

OBJECTIVES

To review and provide evidence-based recommendations for the diagnosis and treatment of otosclerosis.

METHODS

Task force members were educated on knowledge synthesis methods, including electronic database search, review and selection of relevant citations, and critical appraisal of selected studies. Articles written in English or Portuguese on otosclerosis were eligible for inclusion. The American College of Physicians' guideline grading system and the American Thyroid Association's guideline criteria were used for critical appraisal of evidence and recommendations for therapeutic interventions.

RESULTS

The topics were divided into 2 parts: 1) Diagnosis - audiologic and radiologic; 2) Treatment - hearing AIDS, pharmacological therapy, stapes surgery, and implantable devices - bone-anchored devices, active middle ear implants, and Cochlear Implants (CI).

CONCLUSIONS

The pathophysiology of otosclerosis has not yet been fully elucidated, but environmental factors and unidentified genes are likely to play a significant role in it. Women with otosclerosis are not at increased risk of worsening clinical condition due to the use of contraceptives or during pregnancy. Drug treatment has shown little benefit. If the patient does not want to undergo stapedotomy, the use of hearing aids is well indicated. Implantable systems should be indicated only in rare cases, and the CI should be indicated in cases of profound deafness.

First evidence of the link between internal and external structure of the human inner ear otolith system using 3D morphometric modeling

Our sense of balance is among the most central of our sensory systems, particularly in the evolution of human positional behavior. The peripheral vestibular system (PVS) comprises the organs responsible for this sense; the semicircular canals (detecting angular acceleration) and otolith organs (utricle and saccule; detecting linear acceleration, vibration, and head tilt). Reconstructing vestibular evolution in the human lineage, however, is problematic. In contrast to considerable study of the canals, relationships between external bone and internal membranous otolith organs (otolith system) remain largely unexplored. This limits our understanding of vestibular functional morphology. This study combines spherical harmonic modeling and landmark-based shape analyses to model the configuration of the human otolith system. Our approach serves two aims: (1) test the hypothesis that bony form covaries with internal membranous anatomy; and (2) create a 3D morphometric model visualizing bony and membranous structure. Results demonstrate significant associations between bony and membranous tissues of the otolith system. These data provide the first evidence that external structure of the human otolith system is directly related to internal anatomy, suggesting a basic biological relationship. Our results visualize this structural relationship, offering new avenues into vestibular biomechanical modeling and assessing the evolution of the human balance system.

Endolymphatic space is age-dependent

Knowledge of the physiological endolymphatic space (ELS) is necessary to estimate endolymphatic hydrops (ELH) in patients with vestibulocochlear syndromes. Therefore, the current study investigated age-dependent changes in the ELS of participants with normal vestibulocochlear testing. Sixty-four ears of 32 participants with normal vestibulocochlear testing aged between 21 and 75 years (45.8 ± 17.2 years, 20 females, 30 right-handed, two left-handed) were examined by intravenous delayed gadolinium-enhanced magnetic resonance imaging of the inner ear (iMRI). Clinical diagnostics included neuro-otological assessment, video-oculography during caloric stimulation, and head-impulse test. iMRI data analysis provided semi-quantitative visual grading and automatic algorithmic quantitative segmentation of ELS volume (3D, mm³) using a deep learning-based segmentation of the inner ear's total fluid space (TFS) and volumetric local thresholding, as described earlier. As a result, following a 4-point ordinal scale, a mild ELH (grade 1) was found in 21/64 (32.8%) ears uni- or bilaterally in either cochlear, vestibulum, or both. Age and ELS were found to be positively correlated for the inner ear (r(64) = 0.33, p < 0.01), and vestibulum (r(64) = 0.25, p < 0.05). For the cochlea, the values correlated positively without reaching significance (r(64) = 0.21). In conclusion, age-dependent increases of the ELS should be considered when evaluating potential ELH in single subjects and statistical group comparisons.

Comprehensive vestibular evaluation in patients with Otosclerosis: a case control study

Aim

Otosclerosis is one of the common otologic diseases. The mechanism and the probable site of vestibular involvement are not yet fully understood. The present study aimed to perform a comprehensive vestibular evaluation in patients with otosclerosis, compared to the cases without otosclerosis.

Materials and methods

patients underwent a comprehensive cochleovestibular evaluation, including audiometry, ocular and cervical vestibular evoked myogenic potential (o-VEMP and c-VEMP), video head impulse (vHIT) and caloric tests. The results were compared with those obtained from the non-otosclerosis control group.

Results

A total of 61 individuals were included in the study who were divided into two groups of the case (50.82%) and control (49.18%). The results showed that there was a significant difference in the mean vHIT gain between the case and control groups (P < 0.05). However, the mean gain was still within the normal range. Besides, the patients with otosclerosis had significant bilateral or unilateral weaknesses according to caloric test results. Moreover, their o-VEMP and c-VEMP results were significantly abnormal as well (P < 0.05).

Conclusion

Based on the results of the present study, the vestibular system even in asymptomatic cases, is affected by otosclerosis. Furthermore, it seems that the otolithic system has a higher chance of involvement, compared to the semicircular canals.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12070-022-03147-5.

Quantitative analysis of the biomechanical response of semicircular canals and nystagmus under different head positions

The semicircular canals (SCCs) in the vestibular system can sense angular motion of the head, which performs a crucial role in maintaining the human's sense of balance. The different spatial orientations of the head affect the response of human SCCs to rotational movement. In this study, we combined the numerical model of bilateral human SCCs with vestibulo-ocular reflex experiments, and quantitatively investigated the responses of SCCs to constant angular acceleration when the head was in different left-leaning positions, including the head tilted 0°, 15°, 30°, 45°, 60°, 70°, 80°, and 90° to the left. The results showed that the vertical nystagmus slow-phase velocity (SPV) and the corresponding maximal cupula shear strain at the crista surface rose with an increase in the left-leaning angle of the head, reached a maximum at the position of the head tilted approximately 70° to the left, and then decreased gradually. Both the horizontal nystagmus SPV and the corresponding maximal cupula shear strain at the crista surface were the largest under the position of the head tilted 0° to the left, and decreased gradually as the left-leaning angle of the head increased. The numerical results of cupula shear strain at the crista surface in bilateral SCCs can quantitatively explain the combined effects of each SCC's excitation or inhibition on volunteers' nystagmus SPV under different head positions. In addition, a fluid-structure interaction investigation revealed that different left-leaning head positions changed the endolymphatic pressure gradient distribution in SCCs, which determined the transcupular pressure, cupula shear strain at the crista surface, and nystagmus SPV.

IE-Map: a novel in-vivo atlas and template of the human inner ear

Brain atlases and templates are core tools in scientific research with increasing importance also in clinical applications. Advances in neuroimaging now allowed us to expand the atlas domain to the vestibular and auditory organ, the inner ear. In this study, we present IE-Map, an in-vivo template and atlas of the human labyrinth derived from multi-modal high-resolution magnetic resonance imaging (MRI) data, in a fully non-invasive manner without any contrast agent or radiation. We reconstructed a common template from 126 inner ears (63 normal subjects) and annotated it with 94 established landmarks and semi-automatic segmentations of all relevant macroscopic vestibular and auditory substructures. We validated the atlas by comparing MRI templates to a novel CT/micro-CT atlas, which we reconstructed from 21 publicly available post-mortem images of the bony labyrinth. Templates in MRI and micro-CT have a high overlap, and several key anatomical measures of the bony labyrinth in IE-Map are in line with micro-CT literature of the inner ear. A quantitative substructural analysis based on the new template, revealed a correlation of labyrinth parameters with total intracranial volume. No effects of gender or laterality were found. We provide the validated templates, atlas segmentations, surface meshes and landmark annotations as open-access material, to provide neuroscience researchers and clinicians in neurology, neurosurgery, and otorhinolaryngology with a widely applicable tool for computational neuro-otology.

Vestibular Aging Process from 3D Physiological Imaging of the Membranous Labyrinth

There is no three-dimensional (3D) technique to study the microanatomical structures of the in vivo 3D vestibular membranous labyrinth. Recent two MRI methods using a contrast agent can only depict the low-resolution imaging of endolymphatic hydrops. Therefore, we provide the new precise volume rendering algorithms to create the in vivo 3D vestibular membranous labyrinth images from high-resolution temporal bone low-dose CT data. We also ascertain whether the created 3D microstructure images are reliable in anatomical findings. Secondary, we will analyze the age-related changes of the vestibular membranous labyrinth. These created 3D membranous vestibular images were almost consistent with the appearance, dimensions, areas, and angles from those acquired in previous histological works. The age-related image changes showed the enlarged saccule in females, the enlarged utricle in males, and the dilated tendency of the lateral semicircular duct. These results may correlate to the findings of the previous physiological works on cervical and ocular vestibular evoked myogenic potentials, and gait studies. The age-related balance disorders may be associated with the enlargement of each membranous organ in the vestibule. This new imaging technique now enables visualizing microanatomical changes in the in vivo membranous vestibulum, and these created 3D images may suggest physiological information.

[The subjective perception of the vertical-a valuable parameter for determination of peripheral vestibular disorder in Menière's disease in the chronic phase?]

The perception of verticality is mainly based on utricular afferent signals and central processing of the transmitted signals. However, there are also extracranial receptors that make a considerable contribution to the perception of verticality. With the subjective visual vertical (SVV) for the utricle and the subjective trunk vertical (STV), two different parameters are available that are not fully understood in terms of their response to physiologic and pathologic changes. The aim of this work was to determine SVV and STV under certain positions of the head and trunk as well as under the influence of Menière's disease (MD) as a chronic vestibular disease. In a prospective clinical study, 26 patients with MD and 39 healthy volunteers were recruited. Subjects were examined with C‑SVV glasses and with the three-dimensional trunk excursion chair, while head and torso positions were varied. In both groups, SVV determination is clearly more accurate with an earth-vertical head alignment than with a lateral head tilt (right: MM and control group: p = 0.001; left: MM p = 0.001, control group p = 0.000). If the torso is deflected laterally and the head is held straight, the SVV is significantly more accurate (left p = 0.003, right p = 0.015). The SRV was not affected by the presence of unilateral MD, while pathologic SVV values, if present, indicated the affected side. The results of our study support the assumption that in addition to SVV, SRV is an independent parameter for verticality perception and differs from the SVV in terms of lateralizing a peripheral vestibular deficit. These results suggest that the STV may depend not only on utricular function but also on extracranial afferent signals, and not be significantly altered by the presence of a hydropic peripheral vestibular lesion.

Current evidence of peripheral vestibular symptoms secondary to otitis media

BACKGROUND

The association between otitis media and vestibular symptoms has been hypothesized in the past. Thus, in this study, we aimed to critically analyze (based in a systematic review of the literature) whether patients who have otitis media are at greater risk of developing vestibular impairment or not.

METHODS

We performed a systematic review of the literature and identified potentially relevant articles reporting vestibular symptoms and results of vestibular function tests in patients with otitis media through searches of the PubMED, Web of Science, Scopus, and Google Scholar databases. The quality of the final set of records was assessed using the "Newcaste-Ottawa Scale".

RESULTS

Of the 2334 records searched, 43 met our inclusion and exclusion criteria, and those included 2250 patients. The records comprised 20 longitudinal studies, 21 cross-sectional studies, and 2 case reports. Regarding the type of otitis media studied, 25 examined vestibular impairment in otitis media with effusion, 6 acute otitis media, and 12 chronic otitis media. Results of anamnesis, clinical exams, and several vestibular function tests are reported and critically discussed.

CONCLUSION

Most studies evaluating the association between otitis media and vestibular symptoms have potential methodological flaws. Clinical evidence suggests that patients with otitis media have increased chances for having vestibular symptoms, delayed acquisition of developmental milestones, and abnormalities in several vestibular function tests as compared with controls. Future studies with rigorous methodology aiming to assess the clinical significance (and prognostic factors) of the association between otitis media and vestibular impairment are warranted. Key message Several studies demonstrated long-term sequelae secondary to otitis media. However, the evidence supporting those assumptions are based in low-quality evidence. Thus, better structured studies are warranted to better understand the clinical relevance of such association.

Tumarkin-like phenomenon as a sign of therapeutic success in benign paroxysmal positional vertigo

ABSTRACT Objective: To describe an unusual patient reaction to maneuvers used in the treatment of posterior canal benign paroxysmal positional vertigo (PC-BPPV) that we termed the “Tumarkin-like phenomenon”. Methods: At a private practice, 221 outpatients were diagnosed and treated for PC-BPPV. The treatment consisted of performing the Epley or Semont maneuvers. At the end of these maneuvers, when assuming the sitting position, the patients’ reactions were recorded. Results: Thirty-three patients showed a Tumarkin-like phenomenon described by a self-reported sensation of suddenly being thrown to the ground. In the follow-up, this group of patients remained without PC-BPPV symptoms up to at least 72 hours after the maneuvers. Conclusion: The occurrence of a Tumarkin-like phenomenon at the end of Epley and Semont maneuvers for PC-BPPV may be linked with treatment success.

Evaluation of the otolith function using c/oVEMPs in patients with Ménière's disease

Background

Cervical and ocular vestibular evoked myogenic potentials (c/oVEMPs) reflect otolith function. Up-to-date, there are no published reports on the systemic evaluation of otolith function in Ménière’s Disease (MD) nor are there any reports on the differences in VEMPs between patients with early and late stage MD. The aim of this study was to evaluate the difference in c/oVEMPs between patients with MD and normal controls, as well as between patients with early and late stage MD.

Methods

Thirty patients with unilateral MD and thirty healthy subjects (as normal controls) were prospectively enrolled. c/oVEMPs using 500 Hz tone-burst stimuli were performed. VEMP tests were repeated 3 times on each subject to ensure reliability and reproducibility of responses. VEMPs were defined as present or absent. Abnormal VEMP was defined by lack of VEMP response.

Results

In the control group, abnormal cVEMPs and oVEMPs responses were detected in 6.67 and 3.34 % respectively. In MD patients (20 with early stage MD [ES-MD], 10 with late stage MD [LS-MD]), abnormal cVEMPs and oVEMPs responses were detected in 40 and 16.7 % respectively. More patients with MD showed abnormal responses in c/oVEMPs as compared to the control group (p < 0.05). cVEMPs was more often abnormal as compared to oVEMPs in MD patients (p < 0.05). There was a significant difference in abnormal cVEMP responses between ES-MD patients (25 %) and LS-MD patients (70 %) (p < 0.05). Difference in abnormal oVEMP responses (ES-MD, 5 %; LS-MD, 40 %) was significant (p < 0.05).

Conclusion

An increased occurrence of abnormal c/oVEMP recordings appeared in MD patients, possibly as a result of hydrops of the otolith. cVEMPs were more often abnormal in MD patients as compared to oVEMPs, suggesting that saccular dysfunction may be more common than utricular dysfunction. Furthermore, o/cVEMP abnormalities in the LS-MD group were significantly higher than those in the ES-MD group, suggesting the trend that otolith damage is gradually increasing with the aggravation of cochlear injury in MD.

Modulation of muscle sympathetic nerve activity by low-frequency physiological activation of the vestibular utricle in awake humans

We recently showed that selective stimulation of one set of otolithic organs-those located in the utricle, sensitive to displacement in the horizontal axis-causes a marked entrainment of skin sympathetic nerve activity (SSNA). Here, we assessed whether muscle sympathetic nerve activity (MSNA) is similarly modulated. MSNA was recorded via tungsten microelectrodes inserted into cutaneous fascicles of the common peroneal nerve in 12 awake subjects, seated (head vertical, eyes closed) on a motorised platform. Slow sinusoidal accelerations-decelerations (±4 mG) were applied in the X (antero-posterior) or Y (medio-lateral) direction at 0.08 Hz. Cross-correlation analysis revealed partial entrainment of MSNA: vestibular modulation was 32 ± 3 % for displacements in the X-axis and 29 ± 3 % in the Y-axis; these were significantly smaller than those evoked in SSNA (97 ± 3 and 91 ± 5 %, respectively). For each sinusoidal cycle, there were two peaks of modulation-one associated with acceleration as the platform moved forward or to the side and one associated with acceleration in the opposite direction. We believe the two peaks reflect inertial displacement of the stereocilia within the utricle during sinusoidal acceleration, which evokes vestibulosympathetic reflexes that are expressed as vestibular modulation of MSNA as well as of SSNA. The smaller vestibular modulation of MSNA can be explained by the dominant modulation of MSNA by the arterial baroreceptors.

Clinical Value of Vestibular Evoked Myogenic Potential in Assessing the Stage and Predicting the Hearing Results in Ménière's Disease

Objectives

Our goal was to find the clinical value of cervical vestibular evoked myogenic potential (VEMP) in Ménière's disease (MD) and to evaluate whether the VEMP results can be useful in assessing the stage of MD. Furthermore, we tried to evaluate the clinical effectiveness of VEMP in predicting hearing outcomes.

Methods

The amplitude, peak latency and interaural amplitude difference (IAD) ratio were obtained using cervical VEMP. The VEMP results of MD were compared with those of normal subjects, and the MD stages were compared with the IAD ratio. Finally, the hearing changes were analyzed according to their VEMP results.

Results

In clinically definite unilateral MD (n=41), the prevalence of cervical VEMP abnormality in the IAD ratio was 34.1%. When compared with normal subjects (n=33), the VEMP profile of MD patients showed a low amplitude and a similar latency. The mean IAD ratio in MD was 23%, which was significantly different from that of normal subjects (P=0.01). As the stage increased, the IAD ratio significantly increased (P=0.09). After stratification by initial hearing level, stage I and II subjects (hearing threshold, 0-40 dB) with an abnormal IAD ratio showed a decrease in hearing over time compared to those with a normal IAD ratio (P=0.08).

Conclusion

VEMP parameters have an important clinical role in MD. Especially, the IAD ratio can be used to assess the stage of MD. An abnormal IAD ratio may be used as a predictor of poor hearing outcomes in subjects with early stage MD.

Dilated dysplastic vestibule: a new computed tomographic finding in patients with large vestibular aqueduct syndrome

OBJECTIVE

Large vestibular aqueduct syndrome (LVAS) is one of the most common anomalies of the inner ear. The purpose of our study was to evaluate the vestibule for associated aberrations. In particular, we assessed the vestibular volume in patients with LVAS, compared it to an age-matched control population, and evaluated the relationship between the size of the vestibular aqueduct and the vestibule.

METHODS

We reviewed studies of high-resolution computed tomography of temporal bone of 24 consecutive patients with LVAS (15 girls and 9 boys; average age, 8.1 years). Of these, 21 patients had bilateral LVAS and 3 patients had unilateral LVAS. Each ear was evaluated for the size of the vestibular aqueduct and the volume of the vestibule. Similar measurements were obtained in an age-matched control population (28 girls and 18 boys; average age, 8.3 years).

RESULTS

The volume of the vestibule was found to be significantly enlarged in patients with LVAS compared to the control population (right ear, P < 0.0001; left ear, P < 0.0001). A linear correlation could be established between an enlarged vestibular aqueduct and corresponding increase in the volume of the vestibule (right side, P < 0.01; left side, P < 0.01).

CONCLUSION

A dilated dysplastic vestibule is a consistently associated finding in patients with LVAS.

Membranous labyrinth volumes in normal ears and Ménière disease: a three-dimensional reconstruction study

OBJECTIVES

The purpose of this study was to determine the normal volume ranges of cochlear duct, saccule, and utricle, and to assess endolymphatic hydrops in Ménière disease.

STUDY DESIGN

Retrospective temporal bone study.

METHODS

Three-dimensional (3-D) images of membranous labyrinth were reconstructed from 31 normal temporal bones, six temporal bones from three patients with bilateral Ménière disease, and 16 temporal bones from eight patients with unilateral Ménière disease. Volumes of each part of membranous labyrinth were measured in each temporal bone group after 3-D reconstruction.

RESULTS

The mean volumes and upper normal volume limits (over the 95% confidence interval) of the cochlear duct, saccule, and utricle were 7.67 and 9.77 mm(3), 2.42 and 3.68 mm(3), and 10.65 and 16.45 mm(3), respectively. All three patients with bilateral Ménière disease showed endolymphatic hydrops (excess of volume over normal limits) in both ears. Of eight patients with unilateral Ménière disease, five had no symptom in the contralateral ear, whereas three patients had histories of progression from unilateral to bilateral Ménière disease 13-21 years after the initial onset. All of the diseased and three of eight contralateral ears showed endolymphatic hydrops. In contrast, no hydrops was observed in any part of the membranous labyrinth in asymptomatic ears.

CONCLUSIONS

Our findings suggest that cochleosaccular hydrops is a sensitive finding in Ménière disease. In addition, the volume data obtained from this study could be useful as a standard value for the assessment of hydrops in diagnostic imaging of the inner ear in Ménière disease.

Perioperative Recordings of Vestibular-Evoked Myogenic Potentials in Otosclerosis

OBJECTIVES

The aim of the present study was to investigate saccular function in patients with otosclerosis. Furthermore, the influence of stapedotomy on the vestibular-evoked myogenic potentials (VEMPs) should be demonstrated.

STUDY DESIGN

Prospective study.

SETTING

Tertiary referral center.

METHODS

Bone-conducted tone-burst-evoked VEMPs were measured in 23 patients (25 ears) with unilateral or bilateral otosclerosis preoperatively and postoperatively.

RESULTS

Preoperatively, VEMPs could be recorded in 11 ears (44%). There was no statistically significant correlation among the extent of preoperative sensorineural hearing loss, age, and VEMP measurements. Postoperatively, VEMPs were found in 14 ears (56%). In three cases (12%), VEMPs reappeared after surgery. The rare cases of preoperative vertigo could not be correlated to the nonappearance of VEMPs.

CONCLUSION

Stapedotomy surgery does not influence VEMPs, implying that the saccular receptors are not injured by surgery. Moreover, in some cases, the elicitability of VEMPs was improved by stapedotomy surgery. Seemingly, otosclerosis can influence the generation of VEMPs most probably due to an involvement of the otolith organ's saccular receptors. No correlation was found between the clinical occurrence of vertigo and the elicitability of VEMPs.

Assessment of imaging studies used with radiosurgery: a volumetric algorithm and an estimation of its error

✓ The Gamma Knife has played an increasingly important role in the neurosurgical treatment of patients. Intracranial lesions are not removed by radiosurgery. Rather, the goal of treatment is to induce tumor control. During planning, the creation of dose–volume histograms requires an accurate volumetric analysis of intracranial lesions selected for radiosurgery. In addition, an accurate follow-up imaging analysis of tumor volume is essential for assessing the results of radiosurgery. Nevertheless, sources of volumetric error and their expected magnitudes must be properly understood so that the operator may correctly interpret apparent changes in tumor volume. In this paper, the authors examine the often-neglected contributions of imaging geometry (principally image slice thickness and separation) to overall volumetric error.

One of the fundamental sources of volumetric error is that resulting from the geometry of the acquisition protocol. The authors consider the image sampling geometry of tomographic modalities and its contribution to volumetric error through a simulation framework in which a synthetic digital tumor is taken as the primary model. Because the exact volume of the digital phantom can be computed, the volume estimates derived from tomographic “slicing” can be directly compared precisely and independently from other error sources. In addition to providing empirical bounds on volumetric error, this approach provides a tool for guiding the specification of imaging protocols when a specific volumetric accuracy, or volume change sensitivity, for particular structures is sought a priori.

Using computational geometry techniques, the volumetric error associated with image acquisition geometry was shown to be dependent on the number of slices through the region of interest (ROI) and the lesion volume. With a minimum of five slices through the ROI, the volume of a compact lesion could be calculated accurately with less than 10% error, which was the predetermined goal for the purposes of computing accurate dose–volume histograms and determining follow-up changes in tumor volume.

Accurate dose–volume histograms can be generated and follow-up volumetric assessments performed, assuming accurate lesion delineation, when the object is visualized on at least five axial slices. Volumetric analysis based on fewer than five slices yields unacceptably larger errors (that is, > 10%). These volumetric findings are particularly relevant for radiosurgical treatment planning and follow-up analysis. Through the application of this volumetric methodology and a greater understanding of the error associated with it, neurosurgeons can better perform radiosurgery and assess its outcome.

Volume of components of labyrinth: magnetic resonance imaging study

OBJECTIVE

To determine total inner ear fluid volume and cochlear and semicircular canal/vestibule volumes of a normal population to form a base for dimensional abnormalities of inner ear structures.

STUDY DESIGN

Cross-sectional.

SETTING

Academic otology and radiology practices.

PATIENTS

Twenty-nine healthy volunteers (13 male patients and 16 female patients with an average age of 31 yr) without any known history of intrauterine infection or any exposure to ototoxic agents and no abnormality at physical examination from the standpoint of hearing loss were included.

INTERVENTIONS

Twenty-nine volunteers underwent magnetic resonance imaging of the temporal region by means of thin-section T2-weighted sequences. The images were evaluated by the radiologist for the presence of any gross configurational abnormality. Fluid volume of each inner ear and components of labyrinth (cochlea, semicircular canals/vestibule) were calculated with the help of an online work station.

MAIN OUTCOME MEASURE

To determine the volume of components of the labyrinth and total inner ear fluid, which may form a base for future studies about sensorineural hearing loss.

RESULTS

The volumes of total inner ear fluid, cochlea, and semicircular canals/vestibule were calculated. The mean and standard deviation of total inner ear fluid volume, cochlear volume, and semicircular canal/vestibule volume were obtained for each volunteer. Results were assessed with the help of statistical tests.

CONCLUSION

There was no statistically significant difference between right and left inner ear fluid volumes of male and female subjects. There was also no statistical difference between right and left inner ear volumes when age and sex were not concerned. During evaluation of volumes according to sex, the difference between right and left inner ear fluid volumes was also assessed. Left semicircular canal/vestibule volume of female subjects were found to be higher than that of male subjects. The difference between right and left semicircular canal/vestibule volumes of female subjects was higher than the difference between right and left semicircular canal/vestibule volumes of male subjects.

ENT and speech disorders in children with Down's syndrome: an overview of pathophysiology, clinical features, treatments, and current management

Down's syndrome is the most commonly occurring genetic abnormality, involving about 1 in 600 births. The increasing life expectancy of individuals with Down's syndrome has revealed the presence of several unexpected pathological processes. Among these, ENT disorders hold an important place because of their high incidence and severity. Accurate knowledge of the pathophysiology underlying ENT disorders (facial dysmorphism, ear abnormalities, upper airway abnormalities, and immunodeficiency) allow an understanding of the reasons for the development of the upper airway obstruction, obstructive sleep apnea syndrome, subglottic stenosis, deafness, speech delay, and ENT infections that occur frequently in these children. Early screening and specific treatment may allow some of the long-term sequelae to be avoided, or at least their prognosis to be improved. In order to help health care professionals in their daily practice, this review makes a series of recommendations to allow them to develop a master plan for the ENT management of children with Down's syndrome. In children with Down's syndrome, ENT disorders occur frequently and are often severe. They develop owing to craniofacial, functional, and immune system abnormalities. Early screening and treatment allow improvements in long-term outcomes.

Inner ear fluid volumes and the resolving power of magnetic resonance imaging: can it differentiate endolymphatic structures?

Magnetic resonance imaging (MRI) can accurately recognize minute volumes as small as 1 mm3. The volumes of the utricle and saccule of the inner ear are within the resolving power of MRI, but these structures cannot be recognized because the endolymph and perilymph signals are identical. To clarify the interpretation and description of inner ear structures on MRI, we measured and calculated the volumes of the perilymphatic and endolymphatic spaces of the human ear. We found the total volume of the bony labyrinth to be approximately 192.5 mm3 (endolymph, 34.0 mm3; perilymph, 158.5 mm3).

Volumetric and dimensional analysis of the guinea pig inner ear

The objective of this study was to provide accurate volumetric data on the fluid spaces and soft tissue in the guinea pig inner ear by measuring all histologic serial sections by means of Metamorph Imaging Software at 400x to 1,000x magnification. The total endolymph volume of the inner ear was 4.691 mm3, of which 1.501 mm3 was in the cochlea, 3.090 mm3 in the vestibular labyrinth, and 0.100 mm3 in the endolymphatic duct and sac. The total perilymph volume was 15.938 mm3, of which 8.867 mm3 was in the cochlea and 7.071 mm3 in the vestibular labyrinth. The volume of the organ of Corti per millimeter length increased toward the apex, but the volumes of the stria vascularis, spiral ligament, and spiral limbus decreased. The volume of the macula utriculi was larger than that of the macula sacculi. The measurement of the luminal surface area of the stria vascularis was 3.944 mm2, and that of the vestibular dark cells was 5.772 mm2.

Three-dimensional reconstruction of the membranous vestibular labyrinth in the toadfish, Opsanus tau

Membranous vestibular labyrinths from the oyster toadfish, Opsanus tau, were fixed, dissected from the animal, stained, and embedded in rectangular blocks of clear histological resin. Photomicrographs of complete embedded labyrinths were taken from six orthogonal directions and used to construct three-dimensional (3D) geometrical models of the semicircular canals, ampullae, utricular vestibule and common crus. Membraneous ducts and ampullae were modeled using a set of cross-sectional elliptical curves laced together to generate curved tubular models of each structure. The ensemble of these curved tubes was used to generate a complete 3D reconstruction of the outside surface of the membranous labyrinth. When viewed from six orthogonal directions, reconstructions closely matched the embedded tissue. Dimensions of the reconstruction and histological sections were compared to measurements of fresh tissue taken from the same animals prior to fixation and used to correct the reconstructions for tissue shrinkage. Results provide estimates of the endolymphatic volumes, local cross-sectional areas and elliptical eccentricities as well as 3D orientations of the geometric canal planes relative to the skull. Ten micrometer histological sections of the material were also prepared to measure wall thickness in various regions of the labyrinth.

The influence of semicircular canal morphology on endolymph flow dynamics. An anatomically descriptive mathematical model

The classic Steinhausen/Groen mathematical description of endolymph flow in a toroidal semicircular canal is extended to the case where the size, shape, and curvature of the canal lumen change continuously through the duct, utricle, and ampulla. The resulting second-order differential equation has three coefficients, unlike the equation of a torsion pendulum, which has only two. The salient anatomical parameters which determine endolymph motion are: the length of the central streamline occupying the center of the canal lumen; the area enclosed by this streamline as projected into the plane of rotation; the average inverse cross-sectional area of the lumen (taken around the central streamline); and the average inverse squared cross-sectional area, weighted by a local wall shape factor. These parameters are evaluated and the average displacement of the face of the cupula is estimated for the human, guinea pig, and rat, based on new anatomical data presented in companion papers. The model predicts that the dynamic range of human average cupula motion lies between 520 A and 10 microns.

Morphometric comparison of endolymphatic and perilymphatic spaces in human temporal bones

To measure the endolymphatic and perilymphatic spaces, we used human temporal bones (horizontal serial sections) under two selection criteria: absence of otological pathology, and absence of artifact in the membranous labyrinth (boundary between endolymphatic and perilymphatic spaces) maintaining an intact structural integrity. Under magnified projection, the area of scala tympani, scala vestibuli, scala media, vestibular endolymphatic space, and vestibular perilymphatic space were measured separately, using a microcomputer digitizing tablet. Three repeated measurements were obtained and averaged. The mean total labyrinthine fluid space was 204.5 mm3; the mean total endolymphatic space was 38.1 mm3 and mean total perilymphatic space 166.4 mm3. The mean total vestibular fluid space was 120.9 mm3 and mean total cochlear fluid space 83.6 mm3. In the vestibule, the perilymphatic space occupied 74.8%, and the endolymphatic space, 25.2%, whereas 90.8% of the cochlear fluid space was occupied by perilymph.

Dimensions of the horizontal semicircular duct, ampulla and utricle in rat and guinea pig

The dimensions of the membranous labyrinth partly determine the mechanical operation of the semicircular canal system. This study provides, for the first time, extensive measures in individual specimens of the sizes, cross-sectional shapes and areas of the horizontal semicircular duct, ampulla and utricle in the rat and the guinea pig. The membranous labyrinths were fixed in Karnovsky's fixative, exposed, photographed, sectioned, oriented perpendicular to the line of sight and then measured using a calibrated graticule in the eye piece of an operating microscope. As well as the expected size differences between these species, there are major differences in the shape of the utricle.

Comparative morphometry of mammalian otolith organs

The endolymphatic volume of the utricle and the saccule and the surface area of the saccular macula were measured in eight mammalian species, including humans. The results confirmed that all measurements increased slowly but consistently correlating with increases in body weight. However, differences in these endolymphatic volumes or macular surface areas might also be influenced by functional characteristics among different species rather than simply reflecting geometrical comparability.

Fluctuating hearing loss and recurrent vertigo in otosclerosis. An audiologic and temporal bone study

This report summarizes audiologic and temporal bone findings in a 47-year-old white female with recurrent attacks of vertigo, tinnitus, and bilateral hearing loss. A series of audiograms, obtained over a 15-year period, showed a fluctuating mixed (sensorineural and conductive) hearing loss with a relatively flat configuration in the left ear and a relatively stable, mild sensorineural loss with a sloping contour in the right ear. Temporal bone studies revealed the existence of otosclerotic foci bilaterally. In the left ear, the otosclerotic focus has grown close to the utricular and lateral ampullary nerves, displaced and ankylosed the stapedial footplate, invaded the endosteal zone (1,000-2,000 Hz area), and deformed the lateral cochlear wall. In the right ear, the otosclerotic invasion was limited to the inferior portion on the promontory (vestibular cecum) and round window niche.