Psychophysical assessment of spatial spread of excitation in electrical hearing with single and dual electrode contact maskers

OBJECTIVE: To evaluate psychophysically the spatial spread of excitation in electrical hearing with a new dual contact masker and to investigate under which conditions it is possible to stimulate fibers in the immediate neighborhood of an electrode contact, which were not excited by neighboring electrode contacts. DESIGN: In this study a psychophysical forward masking paradigm with a dual contact masker was used to avoid off-site listening, the electrical analogue of off-frequency listening. The masker stimulus (300 msec) is presented nonsimultaneously on two electrode contacts, one on the apical side and another on the basal side of the probe contact, followed by a probe stimulus of 20 msec.Unmasked probe thresholds were compared with masked ones at a number of masker-probe distances, whereas growth of masking curves were measured for a fixed masker contact pair.Standard selectivity measurements (single contact masking) and the recovery of forward masking with one masker contact were included for comparison with existing methods.All experiments were carried out with six participants who use the Clarion CII device with a HiFocus I electrode array. RESULTS: For dual contact masking the amount of masking was significantly greater than for single contact masking and the width of the masking patterns was on average 1.1 mm broader than for single contact masking, resulting in a broad region of excitation, with masker-probe overlap for distances greater than 3 mm. Masking widths for dual and single contact masking were highly correlated.Growth of masking curves were highly nonlinear. They showed a strong elevation of the slope that starts for most subjects around the middle of the dynamic range or above. For 4 out of 6 subjects, no probe threshold was found above a masker amplitude of about 400-500 microA. The ratio of the maximum measurable masked probe thresholds and unmasked probe threshold ranged from 1.7 to 2.6 (S4 excluded).Recovery of masking functions follow an exponential decay. Time constants tau for the recovery process ranged from 21.6 msec to 114.9 msec. CONCLUSIONS: With a dual contact masker (1) off-site listening can be avoided, leading to larger estimates of the width of excitation patterns than in single contact masking, (2) it can be estimated for which stimulation level there is complete overlap of excitation patterns of adjacent electrode contacts, (3) it can be shown that stimulation of nerve fibers in the immediate neighborhood of an electrode contact which were not excited by neighboring electrode contacts is only possible if the probe stimulation amplitude is sufficiently high in comparison with amplitudes on neighboring contacts.     

AN UNUSUAL CASE OF LEFT PARADUODENAL HERNIA

Paraduodenal hernias are the commonest form of intra-abdominal hernia. We report on a rare paraduodenal hernia involving the duodenojejunal recess.     

Potent expansion of human natural killer T cells using alpha-galactosylceramide (KRN7000)-loaded monocyte-derived dendritic cells, cultured in the presence of IL-7 and IL-15

Natural killer T (NKT) cells have an extremely restricted T-cell receptor repertoire, in man consisting of a Valpha24 chain preferentially paired with a Vbeta11 chain, and play crucial roles in various immune responses. Characterization of circulating Valpha24(+)Vbeta11(+)-T cells is hampered by their low frequencies. The alpha-galactosylceramide KRN7000 was reported to be presented by CD1d to NKT cells. Since dendritic cells (DC) are potent antigen presenting cells, and have been shown to express CD1d, we analyzed whether these cells could efficiently mediate expansion of Valpha24(+)Vbeta11(+)-T cells. During a 7-day co-culture of peripheral blood mononuclear cells and KRN7000-loaded mature monocyte derived DC (moDC) in the presence of interleukin-7 (IL-7) and IL-15, we observed up to 76-fold expansion of Valpha24(+)Vbeta11(+)-T cells. The expanded Valpha24(+)Vbeta11(+)-T cells expressed the cytotoxic molecule granzyme B, showed negligible expression of Fas ligand and could be induced to express high levels of interferon-gamma, while retaining the capacity to produce IL-4. B cells, expressing CD1d, could also present KRN7000, but Valpha24(+)Vbeta11(+)-T cell expansion was only observed in the presence of IL-7 and/or IL-15. Considering the low frequency of circulating Valpha24(+)Vbeta11(+)-T cells, the present method for expansion of Valpha24(+)Vbeta11(+)-T cells using KRN7000-loaded mature moDC will be of value for the further characterization of this unique T cell subset.     

Pretreatment with follicle stimulating hormone promotes the numbers of human oocytes reaching metaphase II by in-vitro maturation

The objective of this study was to investigate the effect of follicle stimulating hormone (FSH) priming on the in-vitro maturation (IVM) of human oocytes from healthy ovaries using a chemically defined culture system. Seventeen patients donating oocytes for research received a truncated course of 600 IU FSH over 5 days and a further control group of nine patients received no FSH treatment. Mid-follicular phase cumulus-enclosed oocytes (n = 160) were aspirated from follicles < or =4 mm diameter under transvaginal ultrasound guidance and were cultured for 48 h in microdrops of medium containing 10 mIU/ml FSH and 100 mIU/ ml human chorionic gonadotrophin (HCG). The results demonstrated that human oocytes will efficiently undergo IVM under serum-free conditions. After mild FSH stimulation, a greater number of cumulus-enclosed oocytes was collected, and following culture, a lower rate of degeneration was observed. Significantly more oocytes completed nuclear maturation to metaphase II following FSH stimulation (71.1 versus 43.5%). In conclusion, a truncated course of FSH stimulation in vivo improved the oocyte maturation rate in vitro, giving a mean of 4.8+/- 0.7 metaphase II oocytes per patient compared with only 2.1+/-0.7 from control patients, thus yielding more mature oocytes for future IVF treatment.      

Laparoscopic fimbrioplasty: an evaluation of 35 cases

The aim of this prospective study was to assess the value of laparoscopic treatment of severe fimbrial occlusions. During a period of 52 months infertile patients with fimbrial lesions were treated by operative laparoscopy. Only those patients requiring incision of the tubal serosa (salpingostomy) were included, representing the most severe lesions. The most frequent cases, those patients requiring simple adhesiolysis and deagglutination of the fringes, were excluded. All tubal lesions were documented carefully. Positive Chlamydia trachomatis (CT) serology was found in 65.7% of the patients. All the patients were followed up for at least 2 years. Three patients lost to follow-up were defined as failures. The global conception rate was 74.3%. The intrauterine pregnancy rate was 51.4%, and the 'take home baby rate' was 37.1% (only the first pregnancy being taken into account). The ectopic pregnancy rate was 22.9%. A positive CT serology was found to have a significant influence on the outcome. It can be concluded that the laparoscopic approach provides results similar to those obtained by microsurgery for the treatment of severe fimbrial occlusions, and represents an acceptable alternative to in-vitro fertilization (IVF) in selected cases.      

Bilateral versus unilateral cochlear implantation in young children

Objectives

To compare the preverbal communication skills of two groups of young implanted children: those with unilateral implantation and those with bilateral implantation.

Material and methods

The study assessed 69 children: 42 unilaterally and 27 bilaterally implanted with age at implantation less than 3 years. The preverbal skills of these children were measured before and 1 year after implantation, using Tait Video Analysis that has been found able to predict later speech outcomes in young implanted children.

Results

Before implantation there was no significant difference between the unilateral group and the bilateral group. There was still no difference at 12 months following implantation where vocal autonomy is concerned, but a strongly significant difference between the groups for vocal turn-taking and non-looking vocal turns, the bilateral group outperforming the unilateral group. Regarding gestural turn-taking and gestural autonomy, there was a strongly significant difference between the two groups at the 12 month interval, and also a difference before implantation for gestural autonomy, the unilateral group having the higher scores. Multiple regression of non-looking vocal turns revealed that 1 year following implantation, bilateral implantation contributed to 51% of the variance (p < 0.0001), after controlling for the influence of age at implantation and length of deafness which did not reach statistical significance.

Conclusions

Profoundly deaf bilaterally implanted children are significantly more likely to use vocalisation to communicate, and to use audition when interacting vocally with an adult, compared with unilaterally implanted children. These results are independent of age at implantation and length of deafness.     

Evaluation of the benefit for cochlear implantees of two assistive directional microphone systems in an artificial diffuse noise situation

OBJECTIVE: People with cochlear implants have severe problems with speech understanding in noisy surroundings. This study evaluates and quantifies the effect of two assistive directional microphone systems compared to the standard headpiece microphone on speech perception in quiet surroundings and in background noise, in a laboratory setting developed to reflect a situation whereby the listener is disturbed by a noise with a mainly diffuse character due to many sources in a reverberant room. DESIGN: Thirteen postlingually deafened patients, implanted in the Leiden University Medical Centre with the Clarion CII device, participated in the study. An experimental set-up with 8 uncorrelated steady-state noise sources was used to test speech perception on monosyllabic words. Each subject was tested with a standard headpiece microphone, and the two assistive directional microphones, TX3 Handymic by Phonak and the Linkit array microphone by Etymotic Research. Testing was done in quiet at a level of 65 dB SPL and with decreasing signal-to-noise ratios (SNR) down to -15 dB. RESULTS: Using the assistive directional microphones, speech recognition in background noise improved substantially and was not affected in quiet. At an SNR of 0 dB, the average CVC scores improved from 45% for the headpiece microphone to 67% and 62% for the TX3 Handymic and the Linkit respectively. Compared to the headpiece, the Speech Reception Threshold (SRT) improved by 8.2 dB SNR and 5.9 dB SNR for the TX3 Handymic and the Linkit respectively. The gain in SRT for TX3 Handymic and Linkit was neither correlated to the SRT score with headpiece nor the duration of CI-use. CONCLUSION: The speech recognition test in background noise showed a clear benefit from the assistive directional microphones for cochlear implantees compared to the standard microphone. In a noisy environment, the significant benefit from these assistive device microphones may allow understanding of speech with greater ease.     

Identification Of Two New Pmp22 Mouse Mutants Using Large-Scale Mutagenesis And A Novel Rapid Mapping Strategy

In some alcohol-related pathologies of chronic alcoholism women are more vulnerable than men. A consecutive sample of 62 chronic alcoholics was studied, 18 females and 44 males, aged between 28 and 69 years to assess the incidence and distribution of peripheral neuropathy with regard to gender. All patients underwent clinical and neurological observations, laboratory tests, and electroneurography. Total lifetime dose of ethanol (TLDE) and other risk factors for neuropathy (disease duration, age, nutritional status) were calculated and correlated to sural nerve sensory-evoked potential (SEP) amplitude. In 42 patients (67.7%), we observed the presence of clinical and/or infraclinical neuropathy, mostly axonal, in 29 males (65.9%) and 13 females (72.2%). In women, compared to men, TLDE and disease duration were significantly inversely correlated to sural nerve SEP amplitude, i.e in women, SEP amplitude is significantly reduced in relation to TLDE and disease duration increase. These data indicate a higher sensitivity of females towards the toxic effects of ethanol, other than malnutrition, on peripheral nerve fibres.     

Optimizing the number of electrodes with high-rate stimulation of the clarion CII cochlear implant

OBJECTIVE: This blind crossover study evaluates the effect of the number of electrodes of the Clarion CII cochlear implant on speech perception in silence and in noise using a "high-rate" continuous interleaved sampling (CIS) strategy. MATERIAL AND METHODS: Nine users of this implant with 3-11 months of experience of an 8-channel CIS strategy [833 pulses per second (pps)/channel, 75 micros/phase] were fitted in a random order with 8-, 12- and 16-channel CIS strategies (+/- 1,400 pps/channel, 21 micros/phase). After 1 month of exclusive use of each strategy the performance was tested with consonant-vowel-consonant words in silence (sound only) and in speech-shaped background noise with signal-to-noise ratios (SNRs) of + 10, + 5, 0 and -5 dB. RESULTS: With "high-rate" strategies most patients' speech understanding in noise improved, although the optimum number of electrodes was highly variable. Generally, faster performers benefited from more active electrodes, whilst slower performers deteriorated. If each patient's optimal strategy was determined by a weighted sum of the test results at +10, + 5 and 0 dB SNR, the average phoneme score improved from 57% to 72% at a SNR of + 5 dB, and from 46% to 56% at a SNR of 0 dB. The average phoneme score in silence was approximately 85% for all strategies. CONCLUSION: We conclude that speech perception (especially in noise) can improve significantly with "high-rate" speech processing strategies, provided that the optimum number of electrodes is determined for each patient individually.