Objective evaluation of intracochlear electrocochleography: repeatability, thresholds, and tonotopic patterns

Introduction

Intracochlear electrocochleography (ECochG) is increasingly being used to measure residual inner ear function in cochlear implant (CI) recipients. ECochG signals reflect the state of the inner ear and can be measured during implantation and post-operatively. The aim of our study was to apply an objective deep learning (DL)-based algorithm to assess the reproducibility of longitudinally recorded ECochG signals, compare them with audiometric hearing thresholds, and identify signal patterns and tonotopic behavior.

Methods

We used a previously published objective DL-based algorithm to evaluate post-operative intracochlear ECochG signals collected from 21 ears. The same measurement protocol was repeated three times over 3 months. Additionally, we measured the pure-tone thresholds and subjective loudness estimates for correlation with the objectively detected ECochG signals. Recordings were made on at least four electrodes at three intensity levels. We extracted the electrode positions from computed tomography (CT) scans and used this information to evaluate the tonotopic characteristics of the ECochG responses.

Results

The objectively detected ECochG signals exhibited substantial repeatability over a 3-month period (bias-adjusted kappa, 0.68; accuracy 83.8%). Additionally, we observed a moderate-to-strong dependence of the ECochG thresholds on audiometric and subjective hearing levels. Using radiographically determined tonotopic measurement positions, we observed a tendency for tonotopic allocation with a large variance. Furthermore, maximum ECochG amplitudes exhibited a substantial basal shift. Regarding maximal amplitude patterns, most subjects exhibited a flat pattern with amplitudes evenly distributed over the electrode carrier. At higher stimulation frequencies, we observed a shift in the maximum amplitudes toward the basal turn of the cochlea.

Conclusions

We successfully implemented an objective DL-based algorithm for evaluating post-operative intracochlear ECochG recordings. We can only evaluate and compare ECochG recordings systematically and independently from experts with an objective analysis. Our results help to identify signal patterns and create a better understanding of the inner ear function with the electrode in place. In the next step, the algorithm can be applied to intra-operative measurements.

Using a Bone Conduction Hearing Device as a Tactile Aid

BACKGROUND

With the advent of cochlear implants, tactile aids for the profoundly deaf became obsolete decades ago. Nevertheless, they might still be useful in rare cases. We report the case of a 25-year-old woman with Bosley-Salih-Alorainy Syndrome and bilateral cochlear aplasia.

METHODS

After it was determined that cochlear or brainstem implants were not an option and tactile aids were not available anymore, a bone conduction device (BCD) on a softband was tried as a tactile aid. The usual retroauricular position and a second position close to the wrist, preferred by the patient, were compared. Sound detection thresholds were measured with and without the aid. Additionally, three bilaterally deaf adult cochlear implant users were tested under the same conditions.

RESULTS

At 250-1000 Hz, sounds were perceived as vibrations above approximately 45-60 dB with the device at the wrist. Thresholds were approximately 10 dB poorer when placed retroauricularly. Differentiation between different sounds seemed difficult. Nevertheless, the patient uses the device and can perceive loud sounds.

CONCLUSIONS

Cases where the use of tactile aids may make sense are probably very rare. The use of BCD, placed, e.g., at the wrist, may be useful, but sound perception is limited to low frequencies and relatively loud levels.

Otosclerosis under microCT: New insights into the disease and its anatomy

Purpose

Otospongiotic plaques can be seen on conventional computed tomography (CT) as focal lesions around the cochlea. However, the resolution remains insufficient to enable evaluation of intracochlear damage. MicroCT technology provides resolution at the single micron level, offering an exceptional amplified view of the otosclerotic cochlea. In this study, a non-decalcified otosclerotic cochlea was analyzed and reconstructed in three dimensions for the first time, using microCT technology. The pre-clinical relevance of this study is the demonstration of extensive pro-inflammatory buildup inside the cochlea which cannot be seen with conventional cone-beam CT (CBCT) investigation.

Materials and Methods

A radiological and a three-dimensional (3D) anatomical study of an otosclerotic cochlea using microCT technology is presented here for the first time. 3D-segmentation of the human cochlea was performed, providing an unprecedented view of the diseased area without the need for decalcification, sectioning, or staining.

Results

Using microCT at single micron resolution and geometric reconstructions, it was possible to visualize the disease's effects. These included intensive tissue remodeling and highly vascularized areas with dilated capillaries around the spongiotic foci seen on the pericochlear bone. The cochlea's architecture as a morphological correlate of the otosclerosis was also seen. With a sagittal cut of the 3D mesh, it was possible to visualize intense ossification of the cochlear apex, as well as the internal auditory canal, the modiolus, the spiral ligament, and a large cochleolith over the osseous spiral lamina. In addition, the oval and round windows showed intense fibrotic tissue formation and spongiotic bone with increased vascularization. Given the recently described importance of the osseous spiral lamina in hearing mechanics and that, clinically, one of the signs of otosclerosis is the Carhart notch observed on the audiogram, a tonotopic map using the osseous spiral lamina as region of interest is presented. An additional quantitative study of the porosity and width of the osseous spiral lamina is reported.

Conclusion

In this study, structural anatomical alterations of the otosclerotic cochlea were visualized in 3D for the first time. MicroCT suggested that even though the disease may not appear to be advanced in standard clinical CT scans, intense tissue remodeling is already ongoing inside the cochlea. That knowledge will have a great impact on further treatment of patients presenting with sensorineural hearing loss.

Case Report: Fremitus Nystagmus in Superior Canal Dehiscence Syndrome

Superior canal dehiscence syndrome (SCDS) is a structural bony defect of the roof of the superior semi-circular canal into the middle cranial fossa and is responsible for the creation of a third window, which alters the dynamics of the inner ear. During humming, vibratory waves entering the vestibulum and cochlea are re-routed through the dehiscence, leading to stimulation of the otolithic and ampullary vestibular organs. This is responsible for the torsional-vertical nystagmus known as “fremitus nystagmus”. In this case report, we video-document a rare case of fremitus nystagmus and its resolution after plugging of the superior semi-circular canal.

How Good Are We in Evaluating a Bedside Head Impulse Test?

OBJECTIVES

Clinicians performing a horizontal head impulse test (HIT) are looking for a corrective saccade. The detection of such saccades is a challenge. The aim of this study is to assess an expert's likelihood of detecting corrective saccades in subjects with vestibular hypofunction.

DESIGN

In a prospective cohort observational study at a tertiary referral hospital, we assessed 365 horizontal HITs performed clinically by an expert neurootologist from a convenience sample of seven patients with unilateral or bilateral deficient vestibulo-ocular reflex (VOR). All HITs were recorded simultaneously by video-oculography, as a gold standard. We evaluated saccades latency and amplitude, head velocity, and gain.

RESULTS

Saccade amplitude was statistically the most significant parameter for saccade detection (p < 0.001).The probability of saccade detection was eight times higher for HIT toward the pathological side (p = 0.029). In addition, an increase in saccade amplitude resulted in an increased probability of detection (odds ratio [OR] 1.77 [1.31 to 2.40] per degree, p < 0.001). The sensitivity to detect a saccade amplitude of 1 degree was 92.9% and specificity 79%. Saccade latency and VOR gain did not significantly influence the probability of the physician identifying a saccade (OR 1.02 [0.94 to 1.11] per 10-msec latency and OR 0.84 [0.60 to 1.17] per 0.1 VOR gain increase).

CONCLUSIONS

The saccade amplitude is the most important factor for accurate saccade detection in clinically performed head impulse tests. Contrary to current knowledge, saccade latency and VOR gain play a minor role in saccade detection.

Stroke Prediction Based on the Spontaneous Nystagmus Suppression Test in Dizzy Patients: A Diagnostic Accuracy Study

OBJECTIVE

Failure of fixation suppression of spontaneous nystagmus is sometimes seen in patients with vestibular strokes involving the cerebellum or brainstem; however, the accuracy of this test for the discrimination between peripheral and central causes in patients with an acute vestibular syndrome (AVS) is unknown.

METHODS

Patients with AVS were screened and recruited (convenience sample) as part of a prospective cross-sectional study in the emergency department between 2015 and 2020. All patients received neuroimaging, which served as a reference standard. We recorded fixation suppression with video-oculography (VOG) for forward, right, and left gaze. The ocular fixation index (OFI) and the spontaneous nystagmus slow velocity reduction was calculated.

RESULTS

We screened 1,646 patients reporting dizziness in the emergency department and tested for spontaneous nystagmus in 148 patients with AVS. We analyzed 56 patients with a diagnosed acute unilateral vestibulopathy (vestibular neuritis) and 28 patients with a confirmed stroke. There was a complete nystagmus fixation suppression in 49.5% of patients with AVS, in 40% of patients with vestibular neuritis, and in 62.5% of patients with vestibular strokes. OFI scores had no predictive value for detecting strokes; however, a nystagmus reduction of less than 2 °/s showed a high accuracy of 76.9% (confidence interval 0.59-0.89) with a sensitivity of 62.2% and specificity of 84.8% in detecting strokes.

CONCLUSIONS

The presence of fixation suppression does not rule out a central lesion. The magnitude of suppression was lower compared to patients with vestibular neuritis. The nystagmus suppression test predicts vestibular strokes accurately provided that eye movements are recorded with VOG.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that in patients with an AVS, decreased fixation suppression recorded with VOG occurred more often in stroke (76.9%) than in vestibular neuritis (37.8%).

Quantifying a Learning Curve for Video Head Impulse Test: Pitfalls and Pearls

Objective: The video head impulse test (vHIT) is nowadays a fast and objective method to measure vestibular function. However, its usability is controversial and often considered as a test performed by experts only. We sought to study the learning curve of novices and to document all possible mistakes and pitfalls in the process of learning.

Methods: In a prospective cohort observational study, we included 10 novices. We tested their ability to perform correctly horizontal head impulses recorded with vHIT. We assessed vHITs in 10 sessions with 20 impulses per session giving a video instruction after the first session (S1) and individual feedback from an expert for session 2 (S2) up to session 10 (S10). We compared VOR gain, the HIT acceptance rate by the device algorithm, mean head velocity, acceleration, excursion, and overshoot between sessions.

Results: A satisfying number of accepted HITs (80%) was reached after an experience of 160 vHITs. Mean head velocity between sessions was always in accepted limits. Head acceleration was too low at the beginning (S1) but improved significantly after the video instruction (p = 0.001). Mean head excursion and overshoot showed a significant improvement after 200 head impulses (p < 0.001 each).

Conclusions: We showed that novices can learn to perform head impulses invHIT very fast provided that they receive instructions and feedback from an experienced examiner. Video instructions alone were not sufficient. The most common pitfall was a low head acceleration.

[Dizziness and vertigo in a tertiary ENT emergency department]

BACKGROUND

Although vestibular symptoms are amongst the most frequent reasons for seeking emergency medical help, many patients remain undiagnosed.

OBJECTIVE

In this cross-sectional study, we investigated the spectrum of vertigo and dizziness in a tertiary ear, nose, and throat (ENT) emergency department (ED). Furthermore, we investigated the attendant symptoms, clinical signs, and the diagnostic tests performed.

METHODS

We screened all ED reports from 01/2013 to 12/2013 for adult patients with vestibular symptoms referred to the ENT department.

RESULTS

In total, we found 2596 cases with reported vestibular symptoms in the ED as a main or accompanying complaint. Of these, 286 were referred to the ENT specialist directly (n = 98) or via other major medical specialties (n = 188). Benign paroxysmal positional vertigo (BPPV) was the most frequent diagnosis in our study (n = 46, 16.1%), followed by vestibular neuritis (n = 44, 15.4%), otitis media (n = 20, 7%), and 9 patients (3.1%) had an ischemic stroke or a transient ischemic attack. In 70 (24.5%) cases, dizziness was not further specified.

CONCLUSION

BPPV is the most frequent diagnosis seen in the ED; however, physicians need to document nystagmus more precisely and perform diagnostic tests systematically, in order to make an accurate diagnosis. To avoid misdiagnoses, ED physicians and ENT specialists should be able to recognize central signs in patients with an acute vestibular syndrome. Every fourth patient does not receive a definitive diagnosis. Diagnostic ED workup for patients with dizziness needs further improvement.

[Conservative and surgical management of chronic Rhinosinustitis]

Chronic rhinosinusitis is a common complex medical condition associated with high therapy costs and quality of life impairment. The European Position Paper on Rhinosinusitis and Nasal Polyps (EPOS) 2012 delineates the current standard of management of the patient with chronic rhinosinusitis for both defined disease forms: with and without polyps. Medical history and endoscopic or CT findings are needed for the correct diagnosis. Therapy of chronic rhinosinusitis aims at achieving a local disease control and reducing patients' symptoms. The center point of conservative therapy of both forms is the topical application of steroids together with nasal saline irrigations. In case of persistence of symptoms or in severe chronic rhinosinusitis with polyps, different local application methods of steroids or short systemic steroid cures should be considered. In case of insufficient disease control with conservative treatment, functional endoscopic sinus surgery is the accepted as “gold standard”. Purpose of the surgical management is opening of the sinus ostia in order to improve sinus ventilation and mucociliary clearance as well as to facilitate a wide distribution of topical drugs. Due to technical advances, endoscopic sinus has been reported to be a safe and effective procedure.

Radiation dose reduction in postoperative computed position control of cochlear implant electrodes in lambs - An experimental study

OBJECTIVE

Cochlear implants (CI) are standard treatment for prelingually deafened children and postlingually deafened adults. Computed tomography (CT) is the standard method for postoperative imaging of the electrode position. CT scans accurately reflect electrode depth and position, which is essential prior to use. However, routine CT examinations expose patients to radiation, which is especially problematic in children. We examined whether new CT protocols could reduce radiation doses while preserving diagnostic accuracy.

METHODS

To investigate whether electrode position can be assessed by low-dose CT protocols, a cadaveric lamb model was used because the inner ear morphology is similar to humans. The scans were performed at various volumetric CT dose-indexes CTDIvol)/kV combinations. For each constant CTDIvol the tube voltage was varied (i.e., 80, 100, 120 and 140kV). This procedure was repeated at different CTDIvol values (21mGy, 11mGy, 5.5mGy, 2.8mGy and 1.8mGy). To keep the CTDIvol constant at different tube voltages, the tube current values were adjusted. Independent evaluations of the images were performed by two experienced and blinded neuroradiologists. The criteria diagnostic usefulness, image quality and artifacts (scaled 1-4) were assessed in 14 cochlear-implanted cadaveric lamb heads with variable tube voltages.

RESULTS

Results showed that the standard CT dose could be substantially reduced without sacrificing diagnostic accuracy of electrode position. The assessment of the CI electrode position was feasible in almost all cases up to a CTDIvol of 2-3mGy. The number of artifacts did not increase for images within this dose range as compared to higher dosages. The extent of the artifacts caused by the implanted metal-containing CI electrode does not depend on the radiation dose and is not perceptibly influenced by changes in the tube voltage. Summarizing the evaluation of the CI electrode position is possible even at a very low radiation dose.

CONCLUSIONS

CT imaging of the temporal bone for postoperative electrode position control of the CI is possible with a very low and significantly radiation dose. The tube current-time product and voltage can be reduced by 50% without increasing artifacts. Low-dose postoperative CT scans are sufficient for localizing the CI electrode.

How reliable and safe is full-body low-dose radiography (LODOX Statscan) in detecting foreign bodies ingested by adults?

OBJECTIVE

Foreign body ingestion is common and potentially lethal. This study evaluates the use of low-dose Statscans (LODOX) in emergency departments.

DESIGN

This comparative cross-sectional study retrospectively assessed 28289 digital chest x-rays and 2301 LODOX scans performed between 2006 and 2010 at a tertiary emergency centre. The radiographic appearance, image quality and location of ingested foreign bodies were evaluated in standard digital chest and LODOX radiography. The mean irradiation (μSv) and cumulative mean radiation dose per patient with the ingested foreign body were calculated according to literature-based data, together with the sensitivity and specificity for each modality.

RESULTS

A total of 62 foreign bodies were detected in 39 patients, of whom 19 were investigated with LODOX and 20 with conventional digital chest radiography. Thirty-three foreign bodies were located in the two upper abdominal quadrants, 21 in the lower quadrants-which are not visible on conventional digital chest radiography-seven in the oesophagus and one in the bronchial system. The sensitivity and specificity of digital chest radiography were 44.4% and 94.1%, respectively, and for the LODOX Statscan 90% and 100%, respectively. The calculated mean radiation dose for LODOX investigations was 184 μS, compared with 524 μS for digital chest radiography.

CONCLUSIONS

LODOX Statscan is superior to digital chest radiography in the diagnostic work-up of ingested foreign bodies because it makes it possible to enlarge the field of view to the entire body, has higher sensitivity and specificity, and reduces the radiation dose by 65%.

Limitations of balloon sinuplasty in frontal sinus surgery

Balloon sinuplasty is a tool that is used to treat selected patients with paranasal sinus pathologies. No studies have investigated the aetiology of failed access to the frontal sinus. The aim of our study was to specify the intraoperative technical failure rate and to analyse the aetiology of the failed access to predict potential technical difficulties before surgery. We retrospectively analysed the charts of patients who underwent balloon sinuplasty from November 2007 to July 2010 at three different ENT-Centres. CT-analysis of the patients with failed access was performed. Of the 104 frontal sinuses, dilation of 12 (12%) sinuses failed. The anatomy of all failed cases revealed variations in the frontal recess (frontoethmoidal-cell, frontal-bulla-cell or agger-nasi-cell) or osteoneogenesis. In one patient, a lymphoma was overlooked during a balloon only procedure. The lymphoma was diagnosed 6 months later with a biopsy during functional endoscopic sinus surgery. In complex anatomical situations of the frontal recess, balloon sinuplasty may be challenging or impossible. In these situations, it is essential to have knowledge of classical functional endoscopic sinus surgery of the frontal recess area. The drawbacks of not including a histopathologic exam should be considered in balloon only procedures.

[Tracheobronchial foreign body in children. Is anamnesis alone enough to indicate tracheobronchoscopy?]

From 1989-1993 we performed rigid bronchoscopies in 86 children in whom foreign body aspirations were suspected. In 72 cases, foreign bodies were identified in the tracheobronchial tree. In the remaining 14, no foreign body was found. Boys outnumbered girls. The most common type of foreign body was a peanut. The predilection of the foreign body was to fall into the right main bronchus. If the history indicated foreign body aspiration, a chest x-ray was not found to be necessary except for forensic interest.

[Rare malignant laryngeal tumors]

Six rare malignant tumors were found in a group of 136 laryngeal malignancies accessioned between 1990 and 1992. The other 130 neoplasms were squamous cell carcinomas. One case each of an adenocarcinoma, a mucoepidermoid carcinoma and an undifferentiated carcinoma of nasopharyngeal type were of epithelial origin; a case of a malignant fibrous histiocytoma, a chondrosarcoma and a plasmacytoma were of mesenchymal origin. The clinical presentations, histological findings, and therapy employed in the six cases are discussed and the available literature reviewed.