Intraoperative recordings of electromyogenic responses from the human stapedius muscle.

Following surgical implantation of a cochlear implant, the external processor must be programmed individually, which is typically achieved by behavioral measurements, with the user indicating the perceived loudness between the threshold and the maximum comfort levels (MCLs). However, the stapedius reflex measurement could be used instead, as the basis for programming the fitting maps. The electrically evoked stapedius reflex threshold is known to have a high correlation with the MCLs and thus is used as an objective tool to determine the MCL, especially in children and non-cooperative patients. Previous studies demonstrated that the electromyogenic (EMG) activity of the stapedius muscle could be measured to determine stapedius reflex responses. The objective of this study was to demonstrate that intraoperative EMG recordings from the stapedius muscle could be performed with an EMG recording electrode designed for chronical implantation. Ten adult subjects with single sided deafness (SSD) participated in this study. The study was split up into a pre-, intra- and postoperative phase. In the preoperative phase the subjects were screened for the presence of the acoustic stapedius reflex by using a standard tympanometer in the ear to be implanted, while the contralateral ear was stimulated acoustically. During the intraoperative phase an EMG recording electrode was placed in the stapedius muscle and EMG responses were recorded during acoustical and electrical stimulation. The surgical procedure consisted of two interconnected procedures: A classical surgical approach for cochlear implantation with two additional surgical steps, and the temporary placement of an EMG recording electrode in the stapedius muscle made through an opening in the pyramidal eminence, allowing EMG recordings. The postoperative phase was used to evaluate the preservation of the stapedius reflex postoperatively at 1- and 6-months with contralateral acoustic and ipsilateral electrical stimulation. The EMG recording electrode could successfully be placed in the stapedius muscle in all subjects and was able to reliably record EMG signals from the stapedius muscle elicited by acoustic and electrical stimulation. Overall, EMG recordings were obtained intraoperatively in all subjects tested (8 out of 8 subjects). Contralateral acoustic stapedius reflexes were obtained in 6 out of 8 subjects and ipsilateral electrical stapedius reflex in 7 out of 8 subjects. In the postoperative phase, the preservation of the postoperative reflex was observed in 6 out of 10 subjects 1-month after surgery and in 8 out of 10 subjects 6-months after surgery. The study showed that intraoperative EMG recordings from the stapedius muscle can be performed with an EMG recording electrode designed for chronical implantation. The minimally invasive procedure is promising; in particular with regard to the future perspective of measurements in the long-term with an integrated closed-loop self-fitting system.

Comparison of electrophysiological parameters between perimodiolar and lateral wall electrodes in paediatric cochlear implant users.

PURPOSE: (1) To compare the in vivo impedances of electrical contacts of the Nucleus Contour Advance (CA) perimodiolar electrodes and the Nucleus Slim Straight (SS) lateral wall electrodes. (2) To compare the relation between the electrode contact impedances and the behavioural T-/C-levels for both types of electrodes. METHODS: Retrospective case review in two quaternary otologic referral centres was performed. Data on the impedance of the electrode contacts and the T-/C-levels have been collected from 70 consecutive paediatric CI patients. RESULTS: (1) SS electrodes show significantly higher impedance values of the contacts compared to the CA electrodes. This can be explained by differences in the active surface of the electrode contacts and is true for the whole electrode arrays. (2) There are significant negative correlations observed between the impedances of the electrode contacts and the behaviourally measured T-/C-levels. (3) The strength correlation between the electrode impedances and the behavioural T-/C-levels is significantly higher and the T-/C-level variability is lower for the perimodiolar CA electrodes than for the lateral wall SS electrodes. CONCLUSIONS: There exist significant differences in the contact impedance between different cochlear implant electrode arrays. These differences could influence the implant programming parameters and should be considered in any protocols related to automatic implant programming based on objective measures. The predictive value of the electrode impedances for the behavioural T-/C-levels is higher for the perimodiolar CA electrodes than for the lateral wall SS electrodes.

Jugular bulb diverticulum dehiscence towards the vestibular aqueduct in a patient with otosclerosis.

OBJECTIVES: To demonstrate the need for computed tomography imaging of the temporal bone before considering revision stapes surgery in patients with recurrent or residual conductive hearing loss. CASE REPORT: We report the case of a high-riding jugular bulb with an associated jugular bulb diverticulum, which was dehiscent towards the vestibular aqueduct, in a patient with confirmed otosclerosis who did not experience hearing improvement after stapedotomy. CONCLUSION: This case demonstrates the usefulness of temporal bone computed tomography in the evaluation of patients with otosclerosis in whom stapedotomy has not improved hearing. In such patients, revision surgery to address residual hearing loss would eventually prove unnecessary and avoidable.

Diffusion-weighted magnetic resonance imaging of the temporal bone.

This paper summarizes the value of diffusion-weighted magnetic resonance imaging in the evaluation of temporal bone pathology. It highlights the use of different types of diffusion-weighted magnetic resonance imaging in the different types of cholesteatoma, prior to first stage surgery and prior to second look surgery. The value of diffusion-weighted magnetic resonance imaging in the evaluation of pathology of the apex of the petrous bone and the cerebellopontine angle is also discussed.

Long-term follow up after bony mastoid and epitympanic obliteration: radiological findings.

OBJECTIVE: The canal wall up bony obliteration technique lowers the incidence of recurrent cholesteatoma, but carries the potential risk of obliterating residual cholesteatoma. The objective of this study was to report long-term follow-up radiological findings after performing a canal wall up bony obliteration technique procedure, in order to detect residual and/or recurrent cholesteatoma. PATIENTS: Fifty-one patients presenting with a cholesteatoma or a troublesome cavity were operated upon using the canal wall up bony obliteration technique, and were evaluated by follow-up imaging a mean of 76.4 months post-operatively (range, 53.8-113.6 months). INTERVENTION: All patients were evaluated with high resolution computed tomography and magnetic resonance imaging (including delayed contrast, T1-weighted imaging and non-echo-planar, diffusion-weighted imaging). RESULTS: Imaging revealed the presence of one residual, one recurrent and one congenital petrosal apex cholesteatoma. On high resolution computed tomography, completely obliterated mastoid filled with bone was observed in 74.5 per cent (38/51) of patients, and an aerated middle-ear cavity in 64.7 per cent (33/51). High resolution computed tomography clearly detected any associated soft tissue present in the middle-ear cavity (18/51) and in the obliterated mastoids (13/51), but could not characterise this tissue. Non-echo-planar, diffusion-weighted magnetic resonance imaging clearly identified all three cholesteatomas, and differentiated them from other associated soft tissues. No cholesteatoma was found within the obliterated mastoids. CONCLUSION: Long-term follow up indicated that the canal wall up bony obliteration technique is a safe method with which to treat primary and recurrent cholesteatoma and to reconstruct unstable cavities. Soft tissue was found quite often in the middle ear and obliterated mastoids. High resolution computed tomography identified its presence but could not further characterise it. However, non-echo-planar, diffusion-weighted magnetic resonance imaging succeeded in differentiating soft tissues, enabling detection of residual or recurrent cholesteatoma after a canal wall up bony obliteration technique procedure.

Detection of rare nonsynonymous variants in TGFB1 in otosclerosis patients.

Otosclerosis is one of the most common forms of hearing loss in the European population. We have identified a SNP in the TGFB1 (transforming growth factor beta 1) gene that is associated with susceptibility to otosclerosis. The protective allele of this variant, with isoleucine at position 263 of the protein, is more biologically active than the risk allele, which has a threonine in this position. Because recent studies have shown that not only common, but also rare variants can be involved in complex diseases, we performed DNA sequence analysis of the exons and intron-exon boundaries of TGFB1 in 755 otosclerosis patients and 877 control samples. We found 3 different nonsynonymous variants (E29, A29 and I241) in four otosclerosis patients, but no such changes were found in controls. In silico analysis shows that these variations could influence TGF-beta1 function and activity. Taking into account that most rare missense alleles are thought to have a biological effect, the data suggest that multiple rare amino acid changing variants in TGF-beta1 may contribute to susceptibility to otosclerosis.

Magnetic resonance imaging of cholesteatoma: an update.

OBJECTIVE: To report on the value and limitations of new MRI techniques in pre- and post-operative MRI of cholesteatoma. The current value of magnetic resonance imaging (MRI) in diagnosing congenital, acquired, and post-operative recurrent or residual cholesteatoma is described. METHODOLOGY AND RESULTS: High resolution computed tomography (HRCT) is still considered the imaging modality of choice for detecting acquired or congenital middle ear cholesteatoma. However, MRI may provide additional information on the delineation and extension of cholesteatoma and on potential complications. Detecting post-operative residual or recurrent cholesteatoma with HRCT was shown to be inaccurate due to the technique's low sensitivity and specificity. CONCLUSIONS: Recently, improvements in MRI techniques have led to a more accurate diagnoses of cholesteatoma using delayed contrast enhanced T1-weighted imaging and diffusion-weighted imaging.

Imaging of intralabyrinthine schwannomas: a retrospective study of 52 cases with emphasis on lesion growth.

BACKGROUND AND PURPOSE: Only a few case reports and small series of intralabyrinthine schwannomas (ILSs) have been reported. The purpose of this study was to assess prevalence, MR characteristics, location, clinical management, and growth potential/patterns of ILSs in the largest series reported. MATERIALS AND METHODS: Lesion localization, MR characteristics, lesion growth, and clinical management were reviewed in 52 patients diagnosed with an ILS between February 1991 and August 2007 in 2 referral centers. The number of ILSs and vestibulocochlear schwannomas in the cerebellopontine angle/internal auditory canal was compared to assess the prevalence. RESULTS: ILSs most frequently originate intracochlearly, are hyperintense on unenhanced T1-weighted images, enhance strongly after gadolinium administration, and are sharply circumscribed and hypointense on thin heavily T2-weighted 3D images. The scala tympani is more frequently or more extensively involved than the scala vestibuli. Follow-up MR imaging, available in 27 patients, showed growth in 59% of subjects. Growth was seen from the scala tympani into the scala vestibuli and from the scala vestibuli to the saccule and vice versa. Twelve lesions were resected, and the diagnosis of ILS histopathologically confirmed. CONCLUSION: ILSs can account for up to 10% of all vestibulocochlear schwannomas in centers specializing in temporal bone imaging, grow in more than 50%, and are most frequently found intracochlearly, often anteriorly between the basal and second turn. Cochlear ILSs most often originate in the scala tympani and only later grow into the scala vestibuli. Growth can occur from the cochlea into the vestibule or vice versa through the anatomic open connection between the perilymphatic spaces in the scala vestibuli and around the saccule.

Single-shot, turbo spin-echo, diffusion-weighted imaging versus spin-echo-planar, diffusion-weighted imaging in the detection of acquired middle ear cholesteatoma.

Diagnosis of acquired middle ear cholesteatoma on MR imaging is mostly done on late postgadolinium T1-weighted MR images and/or echo-planar (EPI) diffusion-weighted (DWI) MR images. We describe the appearance of a case of a complicated attical middle ear cholesteatoma on single-shot (SS) turbo spin-echo (TSE) DWI compared with EPI-DWI. This case suggests a higher reliability of SS TSE-DWI in the diagnosis of acquired middle ear cholesteatoma.

Acoustic neuroma ingrowth in the cochlear nerve: does it influence the clinical presentation?

We examined the clinical presentation in patients with a histologically proven ingrowth of the cochlear nerve by acoustic neuroma to see whether this differs from what is known from large acoustic neuroma series. In total, 85 acoustic neuromas had an en bloc dissection to study histologically the relation between the cochlear nerve and the acoustic neuroma. In 21 of these 85 specimens, there was histologic proof of invasion of the cochlear nerve by the tumor. For 13 of these 21 tumors, sufficient clinical data could be retrieved to describe the clinical presentation in these patients. We collected clinical data such as age, sex, presenting symptoms, duration of symptoms, tone audiograms, tumor size measurements and volumetric calculations, and latency interval data I-V of brain stem evoked response audiometry and calculated whether there was any correlation among those data. We also compared these clinical data with the data from some large acoustic neuroma series. No clear difference could be shown between the clinical presentation of acoustic neuroma patients with cochlear nerve ingrowth and the clinical presentations in large acoustic neuroma series. This outcome favors the theory that the hearing impairment in acoustic neuroma patients is mainly the result of compression on the vessels of the cochlea and/or on the cochlear nerve.

Belgian experience with the Vibrant Soundbridge prosthesis.

The Belgian Experience with the Vibrant Soundbridge Prosthesis. The authors present the first results obtained with 13 patients implanted with the Vibrant Soundbridge, a semi-implantable electromagnetic hearing device. The first patient was implanted in October 1998. The results show that there were no significant modifications of the hearing thresholds after implantation. The average functional gain was 30 dB in tonal audiometry and 25.6 dB in vocal audiometry. All the patients are satisfied with the device and wear it daily.

CT and MR imaging of congential abnormalities of the inner ear and internal auditory canal.

The embryology of the inner ear must be known as many of the inner ear malformations present as a result of the arrest during the various stages of embryology. These malformations are described in this "embryologic" perspective and specific names for certain malformations are no longer used. Both CT and MR can be used to look at inner ear malformations but often both techniques are complementary. However, CT is preferred when associated middle- or external ear malformations must be excluded. Magnetic resonance is preferred when subtle changes in the membranous labyrinth or abnormalities of the nerves in the internal auditory canal must be visualised. The CT and MR technique must however be adapted as more and more subtle congenital malformations can only be seen when the right technique is used. The heavily T2-weighted gradient-echo or fast spin-echo MR techniques are mandatory if malformations of the inner ear must be excluded. The purpose of this paper is to describe the techniques used to study these patients and to give an overview of the most frequent and important congenital malformations which can be found in the inner ear and internal auditory canal/cerebellopontine angle.

Prognostic value of magnetic resonance imaging findings in hearing preservation surgery for vestibular schwannoma.

OBJECTIVE: The purpose of this study was to determine whether three magnetic resonance imaging (MRI) findings (tumor size, extension to the fundus, intralabyrinthine signal intensity) have a predictive value to hearing preservation in vestibular schwannoma surgery. STUDY DESIGN: A retrospective study was conducted of preoperative high-resolution MR images in a series of consecutive hearing preservation attempts for vestibular schwannomas. PATIENTS: Twenty-six consecutive records of patients with an acoustic tumor removed via a retrosigmoid transcanal approach were analyzed, and the MR images were reviewed blindly and compared with postoperative hearing. SETTING: The study took place in a tertiary referral center. Imaging Techniques: The MR sequences used in this study were unenhanced and gadolinium-enhanced T1-weighted spin-echo images and gradient echo images (3DFT-CISS). MAIN OUTCOME MEASURES: The predictive value of three MRI signs was analyzed: tumor size, lateral extension of the tumor (with and without obliteration of the fundus), and the maintenance of, or decrease in, the intralabyrinthine signal intensity on the affected side in comparison with the signal intensity on the opposite normal side as seen on 3DFT-CISS images. RESULTS: The tumor size in ears in which hearing was preserved averaged 15 mm and was 17 mm in those cases where hearing was not preserved. Hearing was preserved in 50% of ears when the tumor did not extend to the fundus but in only 33% when the fundus was obliterated by tumor. A "normal" intralabyrinthine signal on CISS images (being an isointense signal when compared with the contralateral unaffected ear) was followed by hearing preservation in 82% of ears, whereas in cases where the intralabyrinthine signal was low, hearing was preserved in only 20%. This correlation was statistically significant (p < 0.05). CONCLUSION: The intralabyrinthine signal intensity on 3DFT-CISS gradient-echo images is a valuable additional tool for determining candidacy for hearing preservation surgery. In two cases with preoperative decrease in signal intensity of the intralabyrinthine fluids, control MRI after surgery showed spontaneous recovery of normal intralabyrinthine signal intensity. The authors hypothesize that vascular compression in the internal auditory canal by the tumor is responsible for the observed intralabyrinthine signal decrease.

Giant congenital intracranial epidermoid tumor: a case report.

A case of a large epidermoid tumor in a middle-aged woman with limited symptomatology is reported. Intracranial epidermoid tumors are slow growing and benign lesions. Although the treatment of choice consists in complete resection, partial removal may be preferred in some very extended cases presenting with minimal symptomatology because of the lower morbidity involved. This case illustrates a key-hole approach via a retrolabyrinthine route with preservation of all labyrinthine structures, including the endolymphatic sac and duct. The epidermoid was partially removed by extensive intracapsular debulking under endoscopic control with the aim of decreasing cerebral compression. All cranial nerve functions were preserved and the 6 month postoperative imaging has remained unchanged over a 2-year long follow-up period. The literature regarding this rare pathology is also reviewed.

New developments in cochlear implants.

Essential to improve the performance with cochlear implants is a better control of the electrode-nerve interface. The long-term stability of the electrode characteristics has to be guaranteed. Most important herein is to have a low and stable electrical impedance and to prevent fibrosis. Results of electrode coating and fibrosis-inhibiting products are described. To assess the properties of the electrode-nerve interface such as stimulation threshold, spatial selectivity and channel interaction, the electrically evoked compound action potential is measured. The measurement paradigm and the first results are described. Models of auditory nerve response to electrical stimulation can be used as a tool for cochlear implant fitting. A simple model is proposed and its predictions are compared with measured responses.