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.

Prognostic significance of electrophysiological tests for facial nerve outcome in vestibular schwannoma surgery.

OBJECTIVE: To assess the prognostic significance of pre-operative electrophysiological tests for facial nerve outcome in vestibular schwannoma surgery. METHODOLOGY: Retrospective study design in a tertiary referral neurology unit. We studied a total of 123 patients with unilateral vestibular schwannoma who underwent microsurgical removal of the lesion. Nine patients were excluded because they had clinically abnormal pre-operative facial function. Pre-operative electrophysiological facial nerve function testing (EPhT) was performed. Short-term (1 month) and long-term (1 year) post-operative clinical facial nerve function were assessed. RESULTS: When pre-operative facial nerve function, evaluated by EPhT, was normal, the outcome from clinical follow-up at 1-month post-operatively was excellent in 78% (i.e. HB I-II) of patients, moderate in 11% (i.e. HB III-IV), and bad in 11% (i.e. HB V-VI). After 1 year, 86% had excellent outcomes, 13% had moderate outcomes, and 1% had bad outcomes. Of all patients with normal clinical facial nerve function, 22% had an abnormal EPhT result and 78% had a normal result. No statistically significant differences could be observed in short-term and long-term post-operative facial function between the groups. CONCLUSION: In this study, electrophysiological tests were not able to predict facial nerve outcome after vestibular schwannoma surgery. Tumour size remains the best pre-operative prognostic indicator of facial nerve function outcome, i.e. a better outcome in smaller lesions.

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.

Stridor due to a bridge-like subglottic stenosis in a 10-week-old male infant.

We present an infant with post-intubation stridor caused by a bridge-like subglottic stenosis. At the age of 6 weeks he suffered from a RSV infection with the need for endotracheal intubation. At week 10 acute respiratory distress required a re-intubation. Flexible endoscopy was suggestive for laryngomalacia. Rigid endoscopy revealed a subglottic laterolateral mucosal bridge resulting in a doubling of the airway lumen. Histopathological examination showed a fibrinoid pseudomembrane. Follow up endoscopy showed a grade 1 posterior subglottic stenosis without respiratory compromise. This is the first case in the literature of an infant with a post-intubation bridge-like fibrinoid pseudomembranous subglottic lesion.

Automated high-throughput probe production for DNA microarray analysis.

DNA microarrays have become an established tool for gene expression profiling. Construction of these microarrays using immobilized cDNAs is a common experimental strategy. However, this is extremely laborious, requiring the preparation of hundreds or thousands of cDNA probes. To minimize this initial bottleneck, we developed a comprehensive high-throughput robotic system to prepare DNA probes suitable for microarray analysis with minimal user intervention. We describe an automated system using the MultiPROBE Nucleic Acid Purification Workstation to provide the liquid handling and other functions needed to optimize this process. We were able to carry out fully automated plasmid cDNA isolation, PCR assay setup, and PCR purification and also to direct the characterization and tracking of DNA probes during processing. Protocols began with the initial preparation of a plasmid DNA archive of bacterial stocks in parallel 96-well plates (192 samples/run) and continued through to the dilution and reformatting of chip-ready DNA probes in 384-well format. These and other probe production procedures and additional instrument systems were used to process fully a set of mouse cDNA clones that were then validated by differential gene expression analysis.

Sinonasal fibro-osseous hamartoma: case presentation and differential diagnosis with other fibro-osseous lesions involving the paranasal sinuses.

We present the case of a 2-year-old girl who was referred to the ENT Department of the Antwerp University with a bony obstruction of the left side of the nose. The lesion originated from the ethmoid roof and the middle turbinate and extended into the nasopharynx. A partial functional resection was performed using an endoscopic approach. A combination of clinical, radiographic and histological information permitted a diagnosis of a benign fibro-osseous lesion: sinonasal hamartoma. The benign nature of this tumor justified a conservative follow-up.