Biomedical subjects

Marek Polak

Publications and source records attributed to Marek Polak.

14 recordsLinked to original sources

PubMed2006

Revision cochlear implantation for facial nerve stimulation in otosclerosis.

OBJECTIVE: To find if patients experiencing postsurgical facial nerve stimulation caused by underlying disease process (ie, otosclerosis) can improve their hearing performance with their cochlear implant by reimplantation and by an optimal programming strategy. DESIGN: Retrospective analysis. SETTING: Academic tertiary referral center. PATIENTS: Two cochlear otosclerosis patients with resistant facial nerve stimulation (FNS). Both patients were initially implanted with Nucleus 22 devices (Cochlear Corporation, Englewood, Colo) and they developed FNS after a period of use. Owing to the decreasing number of active electrodes, concurrent decreases in speech understanding occurred. INTERVENTIONS: Various programming approaches were used to address the FNS. Both subjects ultimately received Nucleus 24 devices. One was reimplanted in the same ear, and the other was implanted in the opposite ear. Both have been followed up for 8 months following the reimplantation. MAIN OUTCOME MEASURES: Cochlear implant programming levels, cochlear implant performance, and facial nerve stimulation. RESULTS: The FNS was managed for more than 3 years through optimized programming. However, the FNS progressed until performance dropped below acceptable levels. Reimplantation was believed to be the only option for improvement. After reimplantation and programming, both subjects showed immediate improvement in speech discrimination. One user increased his consonant-nucleus-consonant word score from 12% preoperatively to 42%, and the other's performance increased from 0% to 86%. CONCLUSIONS: Our results suggest that having more programming options with newer devices is critical in otosclerotic or ossified users who experience FNS. Also, reimplantation may be a useful tool to improve performance.

Cochlear Implantation↗

PubMed2006

Glutathione ester protects against hydroxynonenal-induced loss of auditory hair cells.

OBJECTIVE: Test the ability of glutathione monoethyl ester (GSH(e)) to protect auditory hair cells against the ototoxic effects of 4-hydroxy-2,3-nonenal (HNE). STUDY DESIGN AND SETTING: Organ of Corti explants were either untreated or treated with one of a series of four concentrations of GSH(e) for one day, then exposed to HNE. Counts of FITC-phalloidin-labeled hair cells determined both HNE ototoxicity and GSH(e) otoprotection. RESULTS: HNE was toxic to hair cells at physiologically relevant levels, eg, 400 muM, and GSH(e) provided a significant level of protection against HNE ototoxicity (P < 0.05) at all levels tested, ie, 1.16 to 9.3 mM. CONCLUSION: GSH(e) protects auditory hair cells from damage and loss initiated by a naturally occurring ototoxic molecule, ie, HNE (a by-product of oxidative stress). SIGNIFICANCE: Treatment with GSH(e) may be an effective therapy to protect the cochlea against the adverse effects of traumas (eg, electrode insertion) that generate oxidative stress.

Aldehydes↗

PubMed2006

Triamcinolone acetonide protects auditory hair cells from 4-hydroxy-2,3-nonenal (HNE) ototoxicity in vitro.

CONCLUSION: Triamcinolone acetonide crystalline suspension (e.g. Volon A) was not ototoxic to the auditory hair cells present within organ of Corti explants and protected them from an ototoxic molecule, i.e. 4-hydroxy-2,3-nonenal (HNE), that is produced within the organ of Corti as a result of oxidative stress-induced damage. OBJECTIVES: To test the corticosteroid, triamcinolone acetonide, for ototoxicity and otoprotective capacity in organ of Corti explants. MATERIALS AND METHODS: Organ of Corti explants excised from 4-day-old rats were the test system, HNE was the ototoxin challenge. Hair cell integrity counts were performed with fluorescent microscopy on fixed explants stained with FITC-labeled phalloidin. Statistical significance was set at p<0.05. RESULTS: Triamcinolone acetonide did not affect hair cell integrity in the organ of Corti explants and it provided a high level of protection of hair cells against the ototoxic effects of a damaging level of HNE as determined by hair cell density counts.

Aldehydes↗

PubMed2006

D-JNKI-1 treatment prevents the progression of hearing loss in a model of cochlear implantation trauma.

HYPOTHESES: 1) Hearing loss caused by electrode insertion trauma has both acute and delayed components; and 2) the delayed component of trauma-initiated hearing loss can be prevented by a direct delivery of a peptide inhibitor of the c-Jun N-terminal kinase cell death signal cascade, that is, D-JNKI-1, immediately after the electrode insertion within the cochlea. BACKGROUND: Acute trauma to the macroscopic elements of the cochlea from electrode insertion is well known. The impact of trauma-induced oxidative stress within injured cochlear tissues and the efficacy of drugs (e.g., D-JNKI-1) to prevent apoptosis of damaged hair cells is not well defined. METHODS: Hearing function was tested by pure-tone evoked auditory brainstem responses (ABRs) and distortion products of otoacoustic emissions (DPOAEs). D-JNKI-1 in artificial perilymph (AP) or AP alone was delivered into the scala tympani immediately after electrode trauma and for 7 days. Controls were nontreated contralateral and D-JNKI-1-treated ears without electrode insertion trauma. RESULTS: There was no increase in the hearing thresholds of either the contralateral control ears or in the D-JNKI-1 without trauma animals. There was a progressive increase in ABR thresholds and decrease in DPOAE amplitudes after electrode insertion trauma in untreated and in AP-treated cochleae. Treatment with D-JNKI-1 prevented the progressive increase in ABR thresholds and decrease in DPOAE amplitudes that occur after electrode insertion trauma. CONCLUSION: Hearing loss caused by cochlear implant electrode insertion trauma in guinea pigs has both acute and delayed components. The delayed component can be prevented by treating the cochlea with D-JNKI-1.

Analysis of Variance↗

PubMed2006

Use of neural response telemetry measures to objectively set the comfort levels in the Nucleus 24 cochlear implant.

Cochlear implant programming necessitates accurate setting of programming levels, including maximum stimulation levels, of all active electrodes. Frequently, clinical techniques are adequate for setting these levels; however, they are sometimes insufficient (e.g., very young children). In the Nucleus 24, several methods have been suggested for estimation of comfort levels (C levels) from neural response telemetry (NRT); however, many require co-application of clinical measurements. Data was obtained from 21 adult Nucleus 24 recipients to develop reliable predictions of C levels. Multiple regression analysis was performed on NRT threshold, slope of the NRT growth function, age, length of deafness, length of cochlear implant use and electrode impedance to examine predictive ability. Only the NRT threshold and slope of the growth function measures were significant predictors yielding R2 values from 0.391 to 0.769. Results demonstrated that these measures may provide an alternative means of estimating C levels when other clinical measures are unavailable.

Adult↗

PubMed2005

Cochlear temperature correlates with both temporalis muscle and rectal temperatures. Application for testing the otoprotective effect of hypothermia.

CONCLUSIONS: During systemic hypothermia, the internal temperature of the rat cochlea correlates best with the temporalis muscle and rectal temperatures. These positive correlations will be used in future studies to assess the efficacy of mild and moderate hypothermia to protect hearing against the progressive loss caused by electrode insertion in a clinically relevant model of cochlear implantation trauma. OBJECTIVE: To monitor the internal temperature of the cochlea during induced systemic hypothermia using a reference tissue instead of an internal cochlear temperature probe. MATERIAL AND METHODS: The temperatures of the cochlea, brain, temporalis muscle and rectum were determined during periods of normothermia (37 degrees C), mild (33 degrees C) and moderate (30 degrees C) hypothermia and slow rewarming in anesthetized adult Fisher rats. These values were compared using statistical analysis to establish the best correlations between the temperature of the cochlea and the temperature at the three other temperature measurement sites. RESULTS: The strongest correlations with the internal temperature of the cochlea during the induction of mild-to-moderate hypothermia were obtained for the temperatures of the ipsilateral temporalis muscle and rectum.

Animals↗

PubMed2005

Pattern of hearing loss in a rat model of cochlear implantation trauma.

HYPOTHESIS: Trauma caused by cochlear implant electrode insertion is attributable to the combination of direct physical trauma and the delayed cell death of oxidative stress-injured auditory sensory cells. BACKGROUND: Histologic evaluation of cochlear implant electrode trauma has demonstrated that the extent of sensory cell losses is proportional to the degree of injury. However, the impact of delayed oxidative stress within injured cochlear tissues and the progressive loss of injured hair cells by way of apoptosis are at present unknown. METHODS: Laboratory rats were evaluated for hearing acuity before and after electrode insertion, before and after round window membrane incision only. Hearing was measured before trauma or incision and over the next 7 days. Objective measurements of hearing function were distortion products of otoacoustic emissions (DPOAEs) in the frequency range of 2 to 32 kHz and tone-burst (i.e., 4-32 kHz) evoked auditory brain stem responses (ABRs). RESULTS: For the experimental cochleae, there were progressive increases in ABR thresholds and decreases in ABR amplitudes. The amplitude of the DPOAEs in the experimental cochleae also showed progressive decreases. For the contralateral control and round window membrane surgical control ears, there were no significant changes in either DPOAE or ABR thresholds. CONCLUSION: These results document a progressive loss of hearing acuity postimplantation and strongly suggest that electrode insertion trauma generated oxidative stress within injured cochlear tissues.

Animals↗

PubMed2005

Facial nerve stimulation after cochlear implantation.

OBJECTIVES: This study was designed to compare the incidence and nature of facial nerve stimulation (FNS) in patients receiving cochlear implants (CI) manufactured by Cochlear Corporation, Advanced Bionics Corporation, and MedEl. STUDY DESIGN: Retrospective chart review at a tertiary referral center. METHODS: The charts of 600 patients who received CIs from 1993 to 2003 with at least 1 year of follow-up were reviewed for significant FNS (FNS on at least 1 channel at functional stimulation levels). Data collected included age, sex, etiology of deafness, device type, electrode, FNS onset after initial stimulation, number and location of electrode contacts causing FNS, and loudness level at which FSN occurred. Nucleus straight and perimodiolar electrodes were also compared. RESULTS: Thirty-nine of 600 (6.5%) patients had FNS on at least one channel, (MedEl 3 of 43 [7.0%], Nucleus 29 of 440 [6.6%], and Clarion 7 of 117 [6.0%]). The incidence of FNS in Nucleus perimodiolar electrodes (16 of 250 [6.4%]) was similar to straight electrodes (13 of 190 (6.8%]), as was the mean number of electrodes causing FNS per patient (11 vs. 12). However, straight electrodes caused stimulation at significantly softer perceived loudness levels than perimodiolar electrodes (P < .0001). CONCLUSIONS: In this large series of CI FNS, the overall incidence of FNS is consistent with previous reports. All devices had a similar incidence of FNS, but perimodiolar electrodes produced FNS only at significantly higher loudness levels than straight electrodes, making them preferable for patients at risk for FNS receiving Nucleus devices.

Adolescent↗

PubMed2005

Mild hypothermia protects auditory function during cochlear implant surgery.

OBJECTIVE/HYPOTHESIS: Loss of auditory function after cochlear implant (CI) electrode insertion occurs in two stages in the laboratory rat. An immediate loss is followed by a progressive loss over 7 days. Similar stages of acute and progressive neuronal loss occur after trauma in the central nervous system where hypothermia has been shown to have a protective effect. We hypothesize that hypothermia has a similar protective effect against loss of auditory function caused by CI electrode insertion trauma. METHODS: Thirty rats underwent surgery in one cochlea; the contralateral ear was an unoperated control. In the normothermia group, CI electrode insertion trauma was generated with rectal temperature maintained at 37 degrees C throughout the experiment. In the mild hypothermia group, electrode trauma was generated with rectal temperature lowered to 34 degrees C. In the surgical control group, mock surgery was performed at 37 degrees C. Multiple frequency auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) testing of all ears was performed before surgery, immediately afterward, and on postoperative days 3, 5, and 7. RESULTS: Both ABR and DPOAE testing demonstrated partial loss of auditory function after electrode insertion trauma. However, the hypothermia group had significantly less functional loss in the immediate stage and no significant loss in the progressive stage. CONCLUSION: Mild hypothermia protects auditory function during CI electrode insertion.

Animals↗

PubMed2005

Microdebriders used in functional endoscopic sinus surgery: secondary analysis and validation of a new tissue model.

OBJECTIVES/HYPOTHESIS: To validate a previously reported in vitro tissue model for microdebrider comparison and determine which microdebrider, tissue type, blade type, and suction strength is most efficient. Specifically, the goal of the secondary analysis is to expand on the results of the preliminary analysis by increasing the sample size, and introduce an aspiration efficiency score (AES) to facilitate microdebrider comparison. STUDY DESIGN: Prospective randomized comparison. METHODS: A prospective randomized comparison of the Diego Powered Dissector and XPS 3000 Powered ENT System was conducted using a soft tissue and a firm tissue model. In addition to evaluating tissue aspiration with straight and angled blades, clogging rates and clearance times were measured. Both standard wall suction and liposuction were used. Basic statistical analysis, a one-way analysis of variance, and a post hoc Student's t test were performed to compare outcomes. RESULTS: With standard wall suction, the microdebriders were equivalent for the overall microdebrider comparison. For the ''head to head'' comparison with standard wall suction, the devices were also equivalent when using the straight blades, but the XPS 3000 aspirated more tissue when using the angled blades. With liposuction, the XPS 3000 and liposuction independently aspirated more tissue but clogged more often compared with the Diego PD and regular suction. The aspiration efficiency of soft tissue (oysters) and straight blades was superior compared with firm tissue (scallops) and angled blades. For the ''head to head'' comparison with liposuction, the XPS 3000 aspirated more tissue regardless of tissue type, but the Diego PD clogged less with firm tissue (scallops). Overall, the AES favored the XPS 3000, soft tissue (oysters), straight blades, and liposuction. CONCLUSION: Our tissue model represents a reliable and reproducible means of microdebrider comparison. Statistically significant differences between the Diego PD and XPS 3000, as well as between tissue types, blade types, and suction strengths, are reported. Using these results, microdebrider manufacturers can adopt similar tissue models, expand on the current AES, and include other commercially available microdebrider devices to test and report product performance to the consumer. Perhaps an optimal open to closed ratio or liposuction pressure can be determined that yields the greatest tissue aspiration with the fewest number of clogs.

Animals↗

PubMed2004

Evaluation of hearing and auditory nerve function by combining ABR, DPOAE and eABR tests into a single recording session.

In this article, we describe an efficient method for testing both auditory receptor and auditory nerve function in a single recording session. Auditory receptor function is tested in response to pure tone, tone burst and click acoustic stimuli (i.e. distortion products of otoacoustic emissions, DPOAE; and auditory-evoked brainstem responses, ABR). The function of the auditory neurons and nerve is measured in response to direct electric current stimulation (i.e. electrically evoked auditory brainstem responses, eABR). All measurements were obtained from anesthetized laboratory rats during single recording sessions using hardware and software stimulation and analysis programs developed by Intelligent Hearing Systems, Miami, FL.

Acoustic Stimulation↗

PubMed2004

Further prospective findings with compound action potentials from Nucleus 24 cochlear implants.

The purpose of this study was to gain greater understanding of compound action potential (CAP) specific characteristics including: slope of the growth function, P1-N1 amplitude, threshold and latencies of P1 and N1 measured in cochlear implant users. Experienced adult subjects underwent behavioral threshold (T) measurement and electrically elicited stapedial reflex (eSR) recording, followed by CAP measurements on six selected electrodes. Based on the electrically elicited stapedial reflex threshold (eSRT), maximum stimulation level for each measured electrode was set. Relationships among the three thresholds of the above measures and maximum CAP P1-N1 amplitude and slope of the growth function were statistically evaluated for each measured electrode. Threshold of the CAP response showed relationships of similar strength with eSRT and T (r=0.69 and 0.61, respectively). For both slope of the growth function and CAP P1-N1 amplitude, a statistically significant relationship with cochlear place was found. Both specific characteristics of CAP measurement for the most apical electrodes were roughly double those for the most basal electrode (alpha=0.05). This may be partially explained by cochlear anatomy and is consistent with prior mammalian and human studies showing increasing density and survival of spiral ganglion cells in the regions corresponding to intracochlear electrode placement from basal to apical electrodes (90-360 degrees ).

Action Potentials↗

PubMed2002

Cochlear implants in children--a review.

Over the past two decades, cochlear implantation has become a widely accepted treatment of deafness in children. Over 20,000 children have received cochlear implants worldwide. Hearing, language and social development outcomes have been positive. We review current issues in cochlear implantation, candidacy, evaluation, surgery, habilitation, ethics and outcomes.

Child↗

PubMedDate not supplied

Reliability of the University of Miami chronic rhinosinusitis staging system.

BACKGROUND: The aim of this study was to determine the interrater reliability and correlation between computed tomography (CT) and endoscopic components of the University of Miami (UM) Chronic Rhinosinusitis Staging System (UMCRSS), a comprehensive staging system for chronic rhinosinusitis (CRS). METHODS: A prospective analysis of 55 patients undergoing endoscopic sinus surgeryfor CRS was performed. The population consisted of 28 men and 27 women, with a mean age of 45.9 years. All patients underwent staging, via the CT and endoscopic components of the UMCRSS in the operating room, by three examiners. The reliability of the system and all of its components was determined by kappa-coefficient analysis, comparing the data from all three examiners. Correlation between the CT and endoscopic arms was analyzed by Pearson's product moment coefficient. RESULTS: Interrater reliability for the CT arm (kappa = 0.83) and endoscopic arm (kappa = 0.74 for the revision population, and kappa = 0.72 for the primary surgery population) were found to be significant. Endoscopic staging established significant correlation with CT staging (Pearson's r2 = 0.40; p < 0.0001 overall, 0.57, p < 0.0001 for revision, and 0.42, p < 0.0001 for primary cases). CONCLUSION: The UMCRSS is a comprehensive and reliable staging system with very strong and positive correlation between the CT and endoscopic components.

Adolescent↗