Ingo Todt

Normative data for P1/N1-latencies of vestibular evoked myogenic potentials induced by air- or bone-conducted tone bursts

OBJECTIVE The response characteristics of acoustically elicited vestibular evoked myogenic potentials (VEMPs) largely depend on the stimuli applied. A tone-burst stimulation of 500 Hz seems to be clinically most appropriate because those VEMPs can be elicited at the lowest stimulus intensity possible. The aim of the present paper was to describe normative data for tone-burst evoked VEMPs. METHODS VEMPs of 64 healthy subjects were recorded ipsilaterally during air- or bone-conducted tone burst stimulation. The EMG of the tonically activated sternocleidomastoid muscle was recorded ipsilaterally by surface electrodes. Averages were taken for P1/N1-latencies and -amplitudes of male and female volunteers within 3 different age groups. RESULTS The latencies did not show any significant differences between female and male volunteers or between air- and bone-conducted stimulation. The latencies did also not show any significant difference among the 3 age groups. The limits for normal latencies (mean + 2 SD) are, therefore, 20.3 ms for P1 and 28.0 ms for N1. Although the P1/N1-amplitudes were decreased with increasing age, the tonic muscle activity was not significantly different between the age groups. CONCLUSIONS The present findings strongly suggest the evaluation of VEMP latencies by using normative values obtained exactly with the same stimulus parameters. SIGNIFICANCE Normative data as described in the present study are required to detect isolated saccular defects which are indicative of a vestibular disorder.

Does the surgical approach in cochlear implantation influence the occurrence of postoperative vertigo

Objective To investigate the impact of different cochleostomy techniques on vestibular receptor integrity and vertigo after cochlear implantation. Study Design Retrospective cohort study. Subjects A total of 62 patients (17 to 84 years of age) underwent implantation via an anterior or round window insertion approach. Methods Two groups of cochlear implant patients were compared with respect to their pre- and postoperative vestibular function and the occurrence of postoperative vertigo. The data were related to the different cochleostomy techniques. The patients were tested by a questionnaire (dizziness handicap inventory, DIH), caloric irrigation (vestibulo-ocular reflex, VOR) for the function of the lateral SCC and by vestibular evoked myogenic potential (VEMP) recordings for saccular function. RESULTS: Significant differences of postoperative VEMP responses (50% vs 13%) and electromystagmography (ENG) results (42.9% vs 9.4%) were found with respect to the 2 different insertion techniques. The number of patients with vertigo after the surgery as evidenced by DHI (23% vs 12.5%) was significantly different. Conclusion The used round window approach for electrode insertion should be preferred to decrease the risk of loss of vestibular function and the occurrence of vertigo.

Management of posttraumatic vertigo

OBJECTIVE: To evaluate patients after blunt trauma of the head, neck, and craniocervical junction (without fractures) with vertigo and to report the results of treatment after extensive diagnostics. STUDY DESIGN: Prospective study of consecutive new cases with vertigo after trauma at different periods of onset. During 2000–2002, 63 patients were examined and treated. SETTING: Regional trauma medical center for the greater Berlin Area, tertiary referral unit. RESULTS: The primary disorders included labyrinthine concussion (18), rupture of the round window membrane (6), and cervicogenic vertigo (12). The secondary disorders included otolith disorders (5), delayed endolymphatic hydrops (12), and canalolithiasis (9). The patients were free of vertigo symptoms (except cervicogenic and otolith disorder) after treatment, which consisted of habituation training, medical and surgical therapy options. The follow-up was 1 year. CONCLUSION: Posttraumatic vertigo can be treated with a high success rate once the underlying disorder has been identified. The extent of the neurotological test battery determines the precision and quality of diagnostics. Surgical measures should be an integral part of treatment modalities if conservative treatment is not effective. SIGNIFICANCE: Minor trauma of the head, neck, and craniocervical junction can have major impact on the vestibular system at different sites. Patients need to be carefully diagnosed, even if the onset of vertigo occurs a few weeks or months after the initial trauma.

Loss of saccular function after cochlear implantation: the diagnostic impact of intracochlear electrically elicited vestibular evoked myogenic potentials.

Cochlear implant surgery has become a successful procedure for deaf patients to restore their hearing again. Some of the patients, however, complain of persisting dizziness after the surgery which can have a major impact on their quality of life. Neurotological tests of the vestibular system were applied in a total of 18 cochlear implantees pre- and postoperatively. In addition, vestibular evoked myogenic potentials were evoked intraoperatively to investigate possible interferences of the electrically stimulated cochlear implant electrode (eVEMP) with vestibular receptor cells of the saccule in more detail. After cochlear implantation, the saccular function was impaired in the majority of the patients. However, eVEMPs could be recorded intraoperatively in all patients by intracochlear, high-level electrical stimulation via the cochlear implant electrode. In essence, acute, short-term dizziness after cochlear implantation seems to result primarily from a transient vestibular deficit of various origins. In contrast to this, chronic, persisting dizziness after cochlear implant surgery is largely based on a dysfunction of the saccular macula which is an integral component of the otolith system. This saccular impairment is induced most likely by the insertion trauma of the cochlear implant electrode when advancing it into the inner ear. A possible coactivation of the inferior vestibular nerve by the electrical stimulation might play an additional role in the pathogenesis of the persisting postsurgical dizziness.

Comparison of different vibrant Soundbridge audioprocessors with conventional Hearing aids

Objective To compare the functional gain of different Symphonix Soundbridge audioprocessors (HF-processor and D-processor) to preoperatively fitted conventional hearing aids of patients with mild to severe sensorineural hearing loss in the high-frequency range. Study design In a prospective study, the Symphonix Soundbridge (HF-processor and D-processor) fitting results were evaluated and compared with conventional hearing aids. Postoperative air and bone conductances, the functional gain of warble-tone measurements, speech audiometric, and subjective outcome testing (Abbreviated Profile of Hearing Aid Benefit questionnaire) were studied. Setting Tertiary referral center. Patients Five patients (ages, 54–69 yr) with mild to severe sensorineural deafness in the high-frequency range, but no progression of hearing loss during the last two years, were initially fitted with the so-called HF-processor, then subsequently fitted with the D-processor, which was a fully digital one. Results One year after implantation of the Symphonix Soundbridge device, unchanged, stable air and bone conductances were found (except for one minor change). Over the whole frequency range (0.5–8.0 kHz), a mean gain of 16.1 dB (HF-processor), 27.1 dB (D-processor), and 15.2 dB (hearing aid) was found. The Symphonix Soundbridge device with different audioprocessors led to improved hearing in speech audiometric testing. The data show a significant improvement of hearing compared with conventional hearing aids in quiet, and a better functional gain in noise for the Symphonix Soundbridge system. The Abbreviated Profile of Hearing Aid Benefit questionnaire also revealed that the implant resulted in significant differences compared with conventional hearing aids in almost all subcategories. Conclusion The Symphonix Soundbridge device can improve the hearing benefit of moderately to severely hearing handicapped patients—particularly in those with a high-frequency hearing loss—when compared with the conventional hearing aids of these patients, as evidenced by objective and subjective measurements. The Symphonix Soundbridge D-processor showed further improvements and resulted in an additional hearing benefit that was superior to that of the previously fitted HF-audioprocessor. This is owing to the refinements and upgrades in audioprocessor technology.

First European Multicenter Results With a New Transcutaneous Bone Conduction Hearing Implant System: Short-Term Safety and Efficacy

Objective To investigate safety and efficacy of a new transcutaneous bone conduction hearing implant, over a 3-month follow-up period. Study Design Prospective, single-subject repeated-measures design in which each subject serves as his/her own control. Setting Departments of Otolaryngology at 4 hospitals in Germany and Austria. Patients Subjects were 12 German-speaking adults who suffered from conductive or mixed hearing loss. The upper bone conduction threshold limit was set to 45 dB HL at frequencies between 500 Hz and 4 kHz. Intervention Implantation of a transcutaneous bone conduction hearing implant. Main Outcome Measures Subjects’ speech perception (word recognition scores and SRT50%) and audiometric thresholds (air conduction, bone conduction and sound field at frequencies 500 Hz to 8 kHz) were assessed preoperatively, 1 month postoperatively and 3 months postoperatively. The subjects were monitored for adverse events and given a questionnaire to assess their satisfaction levels. Results Speech perception as measured by word recognition scores and SRT50% improved on average about 78.8% and 25 dB HL, respectively, 3 months after implantation. Aided thresholds also improved postoperatively at all tested frequencies and continued to improve from 1 to 3 months postoperatively. Air conduction and bone conduction thresholds showed no significant changes, confirming that subjects’ residual unaided hearing was not deteriorated by the treatment. Only minor adverse events were reported and resolved by the end of the study. Conclusion The new transcutaneous bone conduction implant was demonstrated to be safe and effective in adults up to 3 months of device use.

MRI scanning and incus fixation in vibrant soundbridge implantation.

Objective: Presentation of patient data after Vibrant Sound-bridge (VS) implantation/explantation with respect to magnetic resonance imaging (MRI) compatibility and stability of incus fixation of the implant. Study design: In a retrospective case review, we report on two patients who had to be diagnosed by cranial MRI scans after previous implantation of a VS. Moreover, in one of these cases, the incus was removed after explantation of the VS because of a peripheral hearing loss. This enabled a microscopic evaluation of the incus. At the long process of the incus, the floating mass transmitter (FMT) has been fixed for 4 years. Setting: Tertiary referral center. Subjects: Two patients who fulfilled, at the time of implantation, the criteria for implantation of a VS. Results: In both cases, no demagnetization of the external magnet nor of the FMT were found. Device function after the MRI scans were normal. Pure-tone audiometric thresholds remained unchanged after the MRI scanning and the scanning-related magnetic forces. In both cases, the FMT fixation of the incus was found to be regular. In one case, the fixation was checked by an additional tympanoscopy 1 year after the implantation, and in the other case it was assessed by recording the functional gain of the VS (which was normal) after the MRI scanning. One patient complained about a transient hyperacuity due to the loudness during the MRI scanning procedure. MRI scans showed a blackening of the implant area with spherical distortions of the picture. Conclusion: Although MRI scanning (at 1.5 tesla [T]) with the FMT in place did not lead to adverse effects in the two patients, systematic in vitro studies are required to determine a possible magnetization threshold that could impair the VS function when MRI scans are applied in those patients. The microscopically observed erosions of the long process of the incus after 4 years of FMT clamp fixation show similarities to findings after stapes revision surgery. However, this limited experience in one case does not allow us to make conclusions on the long-term stability of the incus fixation.

Vestibular evoked myogenic potentials induced by intraoperative electrical stimulation of the human inferior vestibular nerve.

Vestibular evoked myogenic potentials (VEMPs) can be recorded from sternocleidomastoid muscle (SCM) in clinical practice. The aim of the present study was to investigate VEMPs upon direct electrical stimulation of the human inferior vestibular nerve to evidence the vestibulocollic reflex arch and their saccular origin, respectively. Seven subjects were stimulated at the inferior (IVN) and superior (SVN) vestibular nerve. The EMG signals of the SCM were recorded. These recordings were compared to air- and bone-conduction evoked VEMPs with respect to latency and shape. All subjects showed normal VEMPs upon acoustic stimulation with a latency of 12.8+/-1.4 ms for P13, and 22.7+/-2.0 ms for the N23 pre-operatively. Upon direct electrical stimulation of the IVN, the mean latency of the positive peak was 9.1+/-2.2 and 13.2+/-2.3 ms for the negative one. No contralateral SCM response was found. Electrical stimulation of the SVN did not result in any EMG response of the SCM. The study shows experimental evidence of the vestibulocollic reflex by direct electrical stimulation of the human IVN for the first time. The method can be utilized to map VIIIth nerve subdivisions and to intraoperatively monitor IVN integrity in a real-time mode.

Vestibular dysfunction of patients with mutations of Connexin 26

The gap junctional network of the inner ear plays an important role in cochlear ionic homoeostasis. Mutations of connexin 26 can induce different types of hearing loss and even deafness. Therefore, it is hypothesized that gap junctions of the human vestibular organ are functionally impaired by mutations of connexin 26. In a prospective, nonrandomized study, the functional status of the semicircular canals and the otolith organs was assessed in one homozygous and six heterozygous carriers of connexin 26 mutations. Five out of seven patients (71.4%) had pathological vestibular evoked myogenic potentials, indicating a loss of saccular function. The utricular function (as tested by subjective haptic vertical) and the function of the semicircular canals (as tested by recording the vestibuloocular reflex) were largely normal. Thus, connexin 26 mutations can be associated with saccular defects of the vestibular receptors.

Indications and Candidacy for Active Middle Ear Implants

Currently, there are two active middle ear implants available commercially: the Vibrant Soundbridge system and the Carina system. A third active middle ear implant, the Esteem, is under clinical evaluation. All devices are indicated for patients with moderate-to-severe hearing loss. Because active middle ear implants are directly coupled to middle ear structures, many of the problems that patients with conventional hearing aids report, such as acoustic feedback, occlusion, and irritation of the outer ear canal, are avoided. In addition, AMEI patients perform well in background noise. However, indications for AMEIs are selective and candidates should be carefully evaluated before surgery. Before considering an AMEI, patients should be provided with conventional hearing aids. Only when benefit is insufficient and audiological selection criteria are met is further candidacy evaluation indicated. Since Colletti described coupling the Vibrant Soundbridge directly onto the round window membrane in 2006, the indications for the Vibrant Soundbridge have expanded and the VSB is implanted in patients with conductive and mixed hearing losses. Patients have often undergone middle ear surgery before. Especially mixed hearing loss cases with 30-60 dB HL sensorineural hearing impairment and 30-40 dB HL air-bone gaps may be helped by this new application.