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Biomedical subjects

Thomas Lenarz

Publications and source records attributed to Thomas Lenarz.

At least 37 records · Page 2Linked to original sources
PubMed2005

Substance distribution in a cochlea model using different pump rates for cochlear implant drug delivery electrode prototypes.

Several studies using animals have shown the protective effects of neurotrophic factors (NF) on spiral ganglion cells (SGC). This is of particular importance since the number of SGCs is considered to be among the factors defining the efficacy of cochlear implants. A device for local inner ear treatment is therefore of great interest. As described previously, we modified a Contour(TM) cochlear implant electrode, to examine the inbuilt canal to be used for fluid release [Paasche, G., Gibson, P., Averbeck, T., Becker, H., Lenarz, T., Stöver, T., 2003. Technical report: modification of a cochlear implant electrode for drug delivery to the inner ear. Otol. Neurotol. 24, 222-227]. In the present study, three different electrode prototypes with openings of the delivery channel at various locations along the electrode array were examined to determine distribution of dye in a cochlea model over time. We compared dye delivery with: (a) release of the dye at the tip, (b) release of the dye at the tip and the side of the electrode, and (c) release of the dye only at the side of the electrode (6 mm from the tip). A mechanical pump was used to drive the system at pump rates of 100, 10, and 1 microl/h. Dye concentration changes along the length of the whole cochlea were investigated. Mean values for all experimental conditions show that the distribution along the array is fastest with two outlets whereas the distribution via a single outlet at the side of the electrode array is not considered to be sufficient. The established experimental setup provides the possibility of investigating prototypes of a fluid based drug delivery system for the treatment of inner ear pathologies in combination with electrical stimulation.

Animals↗
PubMed2005

The use of buccal smears for a non-invasive screening of the 35delG mutation of the Connexin-26 gene in hearing impaired young children.

OBJECTIVES: Recent advances in genetic research indicate that about 50% of congenital deaf patients have a genetic background, with mutations in the Connexin-26 gene being the most frequent one. Screening methods for the genetic cause of deafness have so far mostly been based on the use of peripheral whole blood as DNA source. The use of buccal smears for the genetic screening of deaf patients presents an interesting alternative to drawing blood, especially in young children. In order to validate this method, we compared results from buccal smears from very young deaf children (age<or=3 years) and deaf patients older than 3 years with the results from blood samples deriving from the same patients. METHODS: The detection of the 35delG mutation in the Connexin-26 gene was chosen to demonstrate the method's feasibility. Blood and buccal smears were collected for genetic analysis from 29 very young deaf children (Group 1: age<or=3 years) and 31 deaf patients older than 3 years (Group 2) during their clinical pre-evaluation for cochlear implantation. Genomic DNA was isolated from blood as well as from buccal smears. Yield of both sources was determined by photometric evaluation of the isolated DNA concentration. Genomic DNA isolated from blood and buccal smears was then submitted to PCR-mediated site-directed mutagenesis followed by BS1 YI restriction and electrophoresis. The results for 35delG detection in DNA originating from blood were compared to those of buccal smears. RESULTS: Quantitative DNA analysis showed that both sources provided adequate amounts of DNA for PCR. No significant difference was found between Group 1 and Group 2 considering either the DNA amount isolated from blood or from buccal smears. In all 60 patients, DNA isolated from blood revealed the same results concerning the presence of the 35delG mutation as DNA originating from buccal smears. CONCLUSIONS: This study demonstrates that buccal smears are an adequate, reliable source of genomic DNA providing material for genetic tests that can especially help to avoid drawing blood from very young children for the genetic screening of deafness.

Adolescent↗
PubMed2005

Preservation of residual hearing with cochlear implantation: how and why.

CONCLUSIONS: Hearing may be conserved in adults after implantation with the Nucleus Contour Advance perimodiolar electrode array. The degree of hearing preservation and the maximum insertion depth of the electrode array can vary considerably despite a defined surgical protocol. Residual hearing combined with electrical stimulation in the same ear can provide additional benefits even for conventional candidates for cochlear implantation. OBJECTIVES: We present preliminary results from a prospective multicentre study investigating the conservation of residual hearing after implantation with a standard-length Nucleus Contour Advance perimodiolar electrode array and the benefits of combined electrical and acoustic stimulation. MATERIAL AND METHODS: The subjects were 12 adult candidates for cochlear implantation recruited according to national selection criteria. A "soft" surgery protocol was defined, as follows: 1-1.2-mm cochleostomy hole anterior and inferior to the round window; Nucleus Contour Advance electrode array inserted using the "Advance-off-stylet" technique; and insertion depth controlled by means of three square marker ribs left outside the cochleostomy hole. These procedures had been shown to reduce insertion forces in temporal bone preparations. Variations in surgical techniques were monitored using a questionnaire. Pure-tone thresholds were measured pre- and postoperatively. Patients who still retained thresholds <90 dB HL for frequencies up to 500 Hz were re-fitted with an in-the-ear (ITE) hearing aid. Word recognition was tested in quiet and sentence perception in noise for the cochlear implant alone and in combination with an ipsilateral hearing aid. RESULTS: Hearing threshold level data were available for 12 patients recruited from 6 of the centres. Median increases in hearing threshold levels were 23, 27 and 33 dB for the frequencies 125, 250 and 500 Hz, respectively. These median increases include the data for two patients who had total loss of residual hearing due to difficulties encountered during surgery. "Cochlear view" X-ray images indicated that the depth of insertion varied between 300 and 430 degrees, despite modest variations in the length of the electrode inserted (17-19 mm). The insertion angle had some influence on the preservation of residual hearing at frequencies of 250-500 Hz. Six of the 12 patients retained sufficient hearing for effective use of an ipsilateral ITE hearing aid (< or = 80 dB HL at 125 and 250 Hz; < or = 90 dB HL at 500 Hz). Word recognition scores in quiet were improved from 10% to 30% with the cochlear implant plus ipsilateral hearing aid in 3 patients who had at least 3 months postoperative experience. Signal:noise ratio thresholds for sentence recognition were improved by up to 3 dB. Patients reported that they experienced greatly improved sound quality and preferred to use the two devices together.

Adult↗
PubMed2005

A psychophysical forward masking comparison of longitudinal spread of neural excitation in the Contour and straight Nucleus electrode arrays.

The objective of the study was to compare the widths of forward masking profiles in subjects implanted with the Nucleus 24 Contour or straight electrode array. The Contour array is typically positioned closer to the modiolus than the straight array. Subjects were fourteen postlingually hearing-impaired adults with severe-profound hearing loss, seven used the Contour array and seven used the straight array. Forward masking profiles were measured at three positions along the array (apical, mid, and basal) using maskers at the 15% loudness level. It was hypothesized that masking profile widths would be more sensitive to differences in distance from the neural structures using low-level maskers. Masking width was calculated at the 50% point of the masking peak amplitude. There were no significant differences in masking widths between Contour and straight array subject groups. Current levels for hearing thresholds and maximum comfortable listening levels were significantly lower for the Contour array subjects.

Acoustic Stimulation↗
PubMed2005

Amplitude-mapping effects on speech intelligibility with unilateral and bilateral cochlear implants.

OBJECTIVE: A study was conducted examining the effects of amplitude-mapping adjustments on speech intelligibility with bilateral cochlear implant users, for both unilateral and bilateral device use. The main motivation for this study was the consideration that bilateral loudness summation may result in sounds becoming too loud if no adjustments are made to standard monaural amplitude-mapping functions (maps) when used bilaterally. In that case, reductions of the stimulation levels may be needed. The objective was to assess the impact of such adjustments on speech intelligibility in noise and in quiet. DESIGN: Four different maps were compared in eight bilateral users of the Nucleus 24 system. Each map variation was taken home for 1 week and used bilaterally. After each week, the map used was tested both unilaterally and bilaterally using an adaptive speech-in-noise test and bilaterally for low-level speech in quiet. For the tests in noise, both speech and noise were presented from the same loudspeaker placed directly in front of the listener (S0N0). One of the maps evaluated was a standard clinical map, fitted as if only one ear were to be used. The three other maps used stimulation levels that were reduced more near the maximal stimulation levels, near thresholds, or else by a similar amount over the entire dynamic range. RESULTS: The data showed a modest but statistically significant decrease in performance when stimulation levels were lowered. This was true both in noise and in quiet. For level reductions corresponding to binaural loudness summation effects, the performance decrease was on the order of 1 to 2 dB. Altering the slope of the map had relatively little effect on performance. Comparison of unilateral with bilateral performance using the same map (i.e., no compensation for bilateral loudness summation) and with speech and noise both presented from in front of the listeners showed a modest but statistically significant improvement in the bilateral condition. CONCLUSIONS: Using higher stimulation levels in amplitude-mapping functions can improve both monaural and binaural speech perception performance in quiet and in noise, even when the slope of the acoustic to electrical amplitude-mapping function is held constant (i.e., when the electrical signal-to-noise ratio remains constant). The results in noise can be understood if we assume that the relation between electrical stimulation levels and loudness grows faster at higher stimulation levels. When comparing the monaural better ear with binaural performance in noise (S0N0) by using the same map, that is to say, when no adjustments were made in the bilateral condition for bilateral loudness summation, an average signal-to-noise ratio benefit of 1.4 dB was found in the bilateral condition. These findings indicate that when fitting bilateral devices clinically, although binaural performance may decrease slightly if levels need to be reduced to compensate for binaural loudness summation, the binaural S0N0 advantage over the better ear will offset this. Consequently, performance with both ears after adjustment is likely to remain at least as good as for the better ear alone without level adjustment, even in the S0N0 condition where binaural advantages are minimized.

Acoustic Stimulation↗
PubMed2005

Inner ear abnormalities in patients with Goldenhar syndrome.

OBJECTIVE: The objective of this study is to investigate the inner ear malformations in patients with Goldenhar syndrome and to hypothesize the potential embryopathogenesis of these malformations. STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral center. PATIENTS: Fourteen patients with Goldenhar syndrome. INTERVENTIONS: Each patient underwent hearing tests and high-resolution computed tomography (CT) of the temporal bone. In six patients, magnetic resonance imaging of the temporal bone also was performed. RESULTS: Among the 14 patients with Goldenhar syndrome, 13 had outer and middle ear anomalies and 5 (36%) had inner ear malformations, including one case of common cavity. CONCLUSIONS: Our observations regarding inner ear anomalies in Goldenhar syndrome correlate with the reported cases in the literature and may help to hypothesize the embryological origin of these malformations, which can caused by an early developmental arrest in the fourth gestational week. Specialists evaluating patients with Goldenhar syndrome should be aware of the possibility of inner ear malformations, which could be diagnosed earlier with appropriate imaging studies.

Adult↗
PubMed2005

Evaluation of the advance off-stylet insertion technique and the cochlear insertion tool in temporal bones.

OBJECTIVE: The concept and design of new cochlear implant electrodes is a challenging process. To evaluate new electrode designs, we present a study that uses a microgrinding procedure to evaluate damage to the microstructures of the cochlea resulting from the insertion procedure. In this study, we compared different insertion techniques with the Contour electrode with Softip for placement inside the cochlea and any resulting damage. METHODS: Twenty-five fresh frozen human temporal bones were used to compare electrode insertion characteristics with three insertion techniques (i.e., conventional insertion, Advance Off-Stylet performed manually, and Advance Off-Stylet performed with insertion tool) and two prototype variants of the Contour electrode with Softip (referred as Softip I and Softip II in this article). Five temporal bones were used for each arm of the study: Softip I electrode and conventional insertion; Softip I electrode and manual Advance Off-Stylet insertion; Softip I electrode and Advance Off-Stylet insertion with an early experimental insertion tool; Softip II prototype electrode and manual Advance Off-Stylet insertion; and Softip II prototype and Advance Off-Stylet insertion with a prototype insertion tool. The temporal bones were dehydrated and embedded in epoxy and used for the microgrinding procedure. Resulting images were documented and compared with conventional radiographic images. RESULTS: Our results showed that, especially when using the conventional insertion technique with Softip I electrode arrays, basilar membrane perforations were observable. Using the prototype insertion tool, good placement of the electrode array but also two basilar membrane perforations (one with each type of electrode) were observed. In contrast, the Advance Off-Stylet insertion technique did not show basilar membrane perforation with Softip I and II electrodes and resulted in reliable perimodiolar placement of the arrays. CONCLUSION: Using microgrinding of temporal bones, the Advance Off-Stylet insertion technique was proven to enable more atraumatic insertions of Contour electrodes with Softip and to provide very reliable perimodiolar placements.

Basilar Membrane↗
PubMed2005

Comparison of a paired or sequential stimulation paradigm with advanced bionics' high-resolution mode.

OBJECTIVE: Simultaneous stimulation on two channels was investigated with respect to fully sequential stimulation while controlling for the number of channels and the stimulation rate used. STUDY DESIGN: Only subjects having at least 6 months' experience with conventional Clarion speech coding strategies (CIS, PPS, or SAS) were included. A counterbalanced cross-over design was used to compare the paired stimulation paradigm to the sequential stimulation paradigm. SETTING: The investigation was a prospective, within-subject, repeated-measures experiment. PATIENTS: The study group consisted of 13 postlingually deafened adult subjects. INTERVENTIONS: The following programs were evaluated: 1) 16-channel paired stimulation with 5000 pps per channel; 2) 16-channel sequential stimulation with 2500 pps per channel; and 3) 8-channel sequential stimulation with 5000 pps per channel. MAIN OUTCOME MEASURES: Speech perception tests in quiet and noise, Quality Assessment Questionnaire. RESULTS: On average, both sequential stimulation programs showed comparable results, whereas the program with paired stimulation, on average, provided poorer performance. Several subjects showed a remarkable drop in performance when changing from sequential to paired mode. Although a few subjects showed better performance in quiet when using paired stimulation, they still had poorer performance in noise. A weak trend was found linking the difference between program levels in paired or in sequential stimulation paradigm to the difference in performance with these two settings. CONCLUSION: Results indicate that for all subjects in this group sequential stimulation is more appropriate than paired stimulation. Subjective reports, as well as formal speech perception testing, show that the difference between the two paradigms is pronounced, especially when evaluating in the presence of background noise, the test condition more representative of everyday listening.

Adolescent↗
PubMed2004

Diagnostic relevance of beta2-transferrin for the detection of cerebrospinal fluid fistulas.

OBJECTIVE: The beta(2)-transferrin assay is a specific method to identify cerebrospinal fluid (CSF). Hitherto, this test has not been widely used for the routine screening of patients with suspected CSF leakage. The purpose of this study was to investigate the clinical relevance of the identification of beta(2)-transferrin by comparing the test results with other diagnostic measures and intraoperative findings. DESIGN: Case series. PATIENTS: Retrospective analysis of 182 patients tested once or multiple times for beta(2)-transferrin. MAIN OUTCOME MEASURES: Information was obtained regarding different diagnostic procedures applied to diagnose CSF leakage. The effectiveness of those diagnostic measures was compared. RESULTS: The main indication to test for beta(2)-transferrin was posttraumatic rhinorrhea (25%), followed by spontaneous (22%) and postsurgical (22%) rhinorrhea. In 35 of 205 cases, beta(2)-transferrin was detected in the tested specimens. Thirteen of these required surgical intervention for treatment of the CSF fistula, and the leakage site was identified in all of them. Taking all results into consideration, the highest correlation was observed between the beta(2)-transferrin assay, intrathecal fluorescein application, and surgical exploration. CONCLUSIONS: The beta(2)-transferrin assay is a reliable method for confirming suspected CSF and should be used as a primary screening method in all patients with suspected CSF leakage. Although less invasive, the beta(2)-transferrin assay almost matches the high sensitivity achieved by exploratory surgery and intrathecal application of fluorescein. However, the possibility of bias should be carefully considered, and in particular, negative results should be critically compared with clinical symptoms and with results from other diagnostic procedures.

Adolescent↗
PubMed2004

Limitations of titanium dioxide and aluminum oxide as ossicular replacement materials: an evaluation of the effects of porosity on ceramic prostheses.

BACKGROUND: Because the performance of titanium dioxide (TiO2) has not yet been assessed in the unique environment of the middle ear, its role as an ossicular replacement prototype in the form of a total ossicular replacement prosthesis (TORP) was tested and compared with aluminum oxide (Al2O3), once considered to be a suitable implant material. METHODS: Ossiculoplasty was performed by implanting TORPs into the tympanic cavities of rabbits. After an implantation period of 28, 84, or 300 days, the petrous bones were extracted, whereby the biocompatibility of the prostheses was examined using light microscopy and scanning electron microscopy to determine morphologic changes in situ. Proper implant placement and functionality was tested via manual manipulation. RESULTS: Mucosa was seen covering most of the implants by day 84. Inflammatory cells were not observed in any of the specimens examined. The macroporous TiO2 TORPs were subjected to osseous infiltration, material dissolution, and fragmentation, whereas the microporous TiO2 implants were subjected to an increasing frequency of fissure formations. The Al2O3 prostheses demonstrated signs of material dissolution by producing encapsulated aggregates during the experimental trial period. CONCLUSIONS: Neither the macroporous nor microporous oxide ceramics were able to withstand the oscillatory stress to which they were continually subjected. Although porosity allows for the rapid integration of an implant material into a biological environment, its properties are not suited to fulfill the requirements of strength and long-term stability, which are demanded of middle ear prostheses.

Aluminum Oxide↗
PubMed2004

Benefits of bilateral electrical stimulation with the nucleus cochlear implant in adults: 6-month postoperative results.

OBJECTIVE: To evaluate the benefits of bilateral electrical stimulation for hearing-impaired adult subjects using the Nucleus 24 cochlear implant in a multicenter study, and to compare and quantify performance on speech perception measures in quiet and in noise and localization ability for unilateral and bilateral cochlear implant use. DESIGN: : Repeated single subject measures were carried out for each subject, with each subject serving as their own control. Assessment of unilateral and bilateral listening conditions for performance on tests of speech comprehension and sound localization were performed. Speech comprehension measures were performed in quiet at 0 degree azimuth and in the presence of background noise simultaneously presented from the same speaker and spatially separated by 90 degrees, at S+45 degrees N45 degrees and at S-45 degrees N+45 degrees . Test materials included Freiburger monosyllabic words, Oldenburger sentences, and the Hochmair-Schulz-Moser sentences. Tests of localization were performed in the horizontal plane with 12 speaker locations 30 degrees apart using a shortened sentence stimulus from the Hochmair-Schulz-Moser sentences at two possible presentation levels of 55 and 70 dB sound pressure level for assessment of directionality. The binaural advantage provided by bilateral stimulation was calculated with respect to each ear separately, classified as either the better or poorer performing ear for each speech material in quiet and in noise test conditions. For localization of sound, the binaural advantage was compared with left and right ears separately. Paired comparisons for performance data in all conditions were carried out by considering measurements for each subject in different conditions as paired observations and applying the Student's t test to determine the statistical difference between the data sets. SETTING: Tertiary referral centers with a cochlear implant program. PATIENTS: Thirty-seven profoundly hearing-impaired adults were enrolled in the study, 22 simultaneously and 15 sequentially bilaterally implanted. All patients received the Nucleus 24 cochlear implant and used the Nucleus SPrint or ESPrit 3G speech processor, with the vast majority using the ACE speech coding strategy. RESULTS: For spatially separated speech in noise conditions, an interaural performance advantage for the ear closest to the speech source (i.e., with a superior signal to noise ratio) compared with that for the ear closest to the noise source (i.e., with an inferior signal to noise ratio) is consistently demonstrated regardless of whether it is the better or poorer performing ear closest to the speech signal. This is referred to as a significant binaural head-shadow benefit, resulting in a mean improvement between -10 dB and -11.4 dB in the critical signal to noise ratio required for 50% speech comprehension for the Olden-burger sentences and a mean improvement in the maximum score of 42% to 55% for the ear closest to the speech signal over the ear farthest away for the Hochmair-Schulz-Moser sentences. Bilateral stimulation is always observed to provide a performance advantage over the unilateral listening condition for either ear when ipsilateral to the noise source. In addition, as demonstrated by approximately half the subjects tested in noise with the Hochmair-Schulz-Moser sentences, a performance advantage of bilateral stimulation may be observed over the better ear alone when positioned ipsilateral to the speech signal, which is referred to as a binaural squelch effect. On average, for the group, this resulted in a statistically significant improvement in speech comprehension scores of 8% in the bilateral listening condition compared with the scores for the better ear alone. Through assessment of comprehension of coincidental speech in noise and speech in quiet, a significant benefit of binaural redundancy was noted for the group for Oldenburger sentence scores in noise and in quiet compared with unilateral scores for either ear and for the Freiburger monosyllabic words in quiet in comparison with the better ear alone scores. Binaural stimulation also led to a significant improvement in localization ability over either monaural condition, with the root mean square degrees of error reduced by 38 degrees compared with that observed for unilateral stimulation. CONCLUSION: Similar to what has been observed for bilateral acoustic stimulation in the past, bilateral electrical stimulation provides the foundation for the potential advantages of the head-shadow effect, providing a binaural head-shadow benefit and binaural auditory processing such as binaural redundancy and binaural squelch effects, all of which combine to lead to improved speech comprehension over unilateral listening conditions. The combination of improved speech comprehension and improved localization ability made available through bilateral electrical stimulation provides the necessary foundation to further assist the hearing-impaired listener to better cope with communication in the everyday listening situation both in noise and in quiet.

Adolescent↗
PubMed2004

Evaluation of the neural response telemetry (NRT) capabilities of the nucleus research platform 8: initial results from the NRT trial.

The purpose of this study was to evaluate the performance of the new features of the Nucleus Research Platform 8 (RP8), a system developed specifically for research purposes The RP8 consists of a research implant, a speech processor and a new NRT software (NRT v4), and includes comparisons of the different artefact-cancellation methods, NRT threshold, and recovery function measurements. The system has new artefact-suppression techniques and new diagnostic capabilities; their performance has been verified in animal experiments. In this study, NRT data were collected from 15 postlingually deafened adult cochlear implant patients intraoperatively and up to 6 months postoperatively after switch-on. The initial investigation in two clinics in Europe focused primarily on the enhanced NRT capabilities Results from the trial in two European clinics indicate that NRT measurements can be obtained with lower noise levels. A comparison of the different artefact-cancellation techniques showed that the forward-masking paradigm implemented in the Nucleus 3 system is still the method of choice. The focus of this report is on recovery function characteristics, which may give insight into auditory nerve fiber properties with regard to higher stimulation rates.

Adolescent↗
PubMed2003

Functional MR imaging of the auditory cortex with electrical stimulation of the promontory in 35 deaf patients before cochlea implantation.

BACKGROUND AND PURPOSE: Promontory testing is used for preoperative assessment of the auditory pathway before cochlear implantation. This method depends on patient cooperation and cannot be used in children or disabled persons. Promontory stimulation during functional MR imaging (fMRI) provides a new and objective method to test the integrity of the auditory pathway. To evaluate the method, we performed this prospective study in deaf adult patients. METHODS: fMRI of the auditory pathway with electrical stimulation of the promontory was performed in 35 profoundly deaf patients, bilaterally in seven. For safe stimulation inside the MR environment, a specially designed nerve stimulator was used. We acquired nine sections parallel to the sylvian fissure by using an echo-planar pulse sequence (1.5 T). To evaluate the number of pixels in the auditory cortex, areas were counted and the minimum confidence level (p(st) value) was determined. The auditory pathway was called intact when the minimal p(st) value was 10(-5) or when the minimal p(st) value was 10(-4) in at least five activated pixels. RESULTS: Images in 85% of patients reporting an auditory sensation showed activation of the contralateral auditory cortex. In the group of patients reporting no hearing sensation, images in 75% did not show activation. CONCLUSION: This method can prove the intactness of the auditory pathway and help the surgeon in decision making before cochlear implantation. However, a negative finding should not be interpreted as indicating a nonfunctioning auditory pathway. Additional technical refinements and experience are needed to further improve this method.

Adult↗
PubMed2002

Virtual endoscopy of the middle ear: experimental and clinical results of a standardised approach using multi-slice helical computed tomography.

Virtual endoscopy (VE) enables non-invasive 3D endoluminal imaging of the middle ear by post-processing of CT data. To optimise the clinical application a standardised approach was evaluated in normal and pathologic cases. Data acquisition was performed using multi-slice helical CT in 20 normal patients and 15 patients with malformation or trauma. Virtual endoscopy of the tympanic cavity and 3D images of the ossicles were generated using surface and volume rendering. Qualitative assessment of the representation of anatomical structures was performed in normal patients. In 15 pathological cases the diagnostic benefit was evaluated by comparing the 3D images to the 2D images and intra-operative findings. In all 35 cases 3D imaging was possible using the standardised approach. The ossicular chain as well as the bony and soft tissue structures of the tympanic cavity were visualised in 20 normal patients. In 7 of 8 patients with malformation and 1 of 7 patients with trauma the original diagnosis was changed by 3D imaging. Standardisation and evaluation of the method in normal patients is essential as it enhances the diagnostic reliability. Virtual endoscopy facilitates understanding of the complex anatomy of the middle ear. In cases of suspected malformation and confirmed trauma it is helpful for diagnosis and surgical planning.

Adolescent↗
PubMed2002

Falsely low serum prolactin in two cases of invasive macroprolactinoma.

The differential diagnosis of tumors at the base of the skull comprises meningiomas, neurinomas, gliomas, metastatic carcinomas, chordomas, epidermoids, and pituitary adenomas. About half of the pituitary adenomas are prolactinomas which are unique in a sense that medical therapy causes rapid tumor shrinkage and symptomatic improvement. We report on two patients in which the diagnosis of an invasive macroprolactinoma was masked by apparently low prolactin levels caused by a high-dose hook effect in the chemiluminometric assay. The first case a 49 year old male with impairment of hearing on the left side was presented in the Department of Otorhinolaryngology. A massive invasively growing tumor was demonstrated on a cranial MRI. Endocrine tests revealed normal pituitary function and normoprolactinemia. The patient underwent debulking surgery, occipitocervical fusion because of destruction of the first cervical vertebra and subsequent irradiation. The histopathological diagnosis was invasive prolactinoma. A repeat prolactin (PRL) sample, which was assayed using serial dilutions, revealed a real PRL level of 89,700 ng/ml. Dopamine agonist therapy was initiated under which PRL levels declined in parallel with tumor size. The second case a 40 year old male was presented with acute visual loss. Cranial MRI showed a large tumor at the base of the skull. Based on a transnasal biopsy, the preliminary diagnosis was a poorly differentiated carcinoma for which emergency irradiation was performed. Endocrine tests demonstrated partial hypopituitarism and moderate hyperprolactinemia. Hydrocortisone was substituted and dopamine agonist therapy was started because of moderate hyperprolactinemia. The final histopathological diagnosis was invasive prolactinoma. A repeat PRL sample assayed in serial dilution demonstrated an apparent rise in PRL with a maximum value of 6,460 ng/ml. Under dopamine agonist therapy, PRL declined to normal values, tumor size decreased and cranial nerve palsies disappeared. The apparently falsely low prolactin levels in the initial work-up of both patients were caused by a high-dose hook effect in the PRL assay. Serial dilutions of serum PRL samples is, therefore, mandatory in the diagnostic work-up of patients with large invasive tumors at the base of the skull. This avoids unnecessary aggressive and dangerous treatment like surgery or radiotherapy in cases where pharmacological treatment may be the choice.

Adult↗
PubMed2002

Results from a European clinical investigation of the Nucleus multichannel auditory brainstem implant.

OBJECTIVE: This study was designed to investigate the perceptual benefits and potential risks of implanting the Nucleus(R) multichannel auditory brainstem implant. DESIGN: Between September 1992 and October 1997 a total of 27 subjects received a Nucleus 20- or 21-channel Auditory Brainstem Implant (ABI). All subjects involved in the trial had bilateral acoustic tumour as a result of neurofibromatosis type 2 (NF2) resulting in complete dysfunction of the VIIIth nerve. The study used each subject as their own control without a preoperative baseline because residual hearing, if existing, was destroyed at surgery by tumour removal. A battery of speech tests was conducted to evaluate each patient's performance and communication abilities. Tests were conducted, where possible, in the auditory-only, visual-only, and auditory-visual conditions at 3 days postoperatively (baseline), at 3-mo intervals for the first year and every 12 mo thereafter. A subjective performance questionnaire was administered together with an extensive neurological examination at each test interval. RESULTS: 27 subjects involved in this trial were successfully implanted with a Nucleus ABI. One subject died 2 days postoperatively due to a lung embolism unrelated to the device. Twenty-six subjects underwent device activation and all but one patient received auditory sensation at initial stimulation (96.2%). On average 8.6 (+/-4.2) of the available 21 electrodes were used in the patients' MAPs. Performance evaluation measures showed that the majority of users had access to auditory information such as environmental sound awareness together with stress and rhythm cues in speech that assist with lipreading. Although most subjects did not achieve any functional auditory-alone, open-set speech understanding, two subjects from this series (7.4%) did receive sufficient benefit to be able to use the ABI in conversation without lipreading. CONCLUSIONS: Although the medical risks and surgical complexity associated with ABI device implantation are far greater than those for a cochlear implant, the clinical results from this trial show that the Nucleus multichannel ABI is capable of providing a significant patient benefit over risk ratio for subjects suffering loss of hearing due to bilateral retrocochlear lesions.

Acoustic Stimulation↗
PubMed2002

Cost-benefit analysis of pediatric cochlear implantation: German experience.

HYPOTHESIS: To explore, from the payers' perspective, the cost-benefit ratio of pediatric cochlear implantation for congenitally deaf and prelingually deafened children compared with children with hearing aids. The study should verify the hypothesis that educational and associated costs increase with age at implantation and that these can be below costs for children with hearing aids. METHODS: Children who received implants at the Medical University of Hanover at different ages (Group 1, 0-1.9 yr; Group 2, 2-3.9 yr; Group 3, 4-6.9 yr) were compared with deaf children using hearing aids (Group 4). Sick funds were the payers for direct and indirect costs, and public authorities were the payers for educational costs. Educational settings were used to measure for benefits. All costs related to the hearing deficiency were included up to the age of 16 years on the basis of 1999 currency values. A scenario analysis was used to explore the impact of variation of costs and discount rates. RESULTS: Total costs for the three age groups of children with implants were from euro 138,000 (approximately US$113,100) to euro 177,000 (approximately US$152,700), compared with euro 160,000 (approximately US$138,000) for hearing aid users. CONCLUSION: This study supports the view that pediatric cochlear implantation provides positive cost-benefit ratios compared with hearing aid users, depending on the age at implantation. Implantation is strongly recommended from the payers' perspective for children implanted before the age of 2 years.

Child↗