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Biomedical subjects

S Burdo

Publications and source records attributed to S Burdo.

10 recordsLinked to original sources
PubMed2006

Auditory cortical responses in patients with cochlear implants.

Currently, the most commonly used electrophysiological tests for cochlear implant evaluation are Averaged Electrical Voltages (AEV), Electrical Advisory Brainstem Responses (EABR) and Neural Response Telemetry (NRT). The present paper focuses on the study of acoustic auditory cortical responses, or slow vertex responses, which are not widely used due to the difficulty in recording, especially in young children. Aims of this study were validation of slow vertex responses and their possible applications in monitoring postimplant results, particularly restoration of hearing and auditory maturation. In practice, the use of tone-bursts, also through hearing aids or cochlear implants, as in slow vertex responses, allows many more frequencies to be investigated and louder intensities to be reached than with other tests based on a click as stimulus. Study design focused on latencies of N1 and P2 slow vertex response peaks in cochlear implants. The study population comprised 45 implant recipients (aged 2 to 70 years), divided into 5 different homogeneous groups according to chronological age, age at onset of deafness, and age at implantation. For each subject, slow vertex responses and free-field auditory responses (PTAS) were recorded for tone-bursts at 500 and 2000 Hz before cochlear implant surgery (using hearing aid amplification) and during scheduled sessions at 3rd and 12th month after implant activation. Results showed that N1 and P2 latencies decreased in all groups starting from 3rd through 12th month after activation. Subjects implanted before school age or at least before age 8 yrs showed the widest latency changes. All subjects showed a reduction in the gap between subjective thresholds (obtained with free field auditory responses) and objective thresholds (obtained with slow vertex responses), obtained in presurgery stage and after cochlear implant. In conclusion, a natural evolution of neurophysiological cortical activities of the auditory pathway, over time, was found especially in young children with prelingual deafness and implanted in preschool age. Cochlear implantation appears to provide hearing restoration, demonstrated by the sharp reduction of the gap between subjective free field auditory responses and slow vertex responses threshold obtained with hearing aids vs. cochlear implant.

Acoustic Stimulation↗
PubMed2005

Normative findings of electrically evoked compound action potential measurements using the neural response telemetry of the Nucleus CI24M cochlear implant system.

One hundred and forty-seven adult recipients of the Nucleus 24 cochlear implant system, from 13 different European countries, were tested using neural response telemetry to measure the electrically evoked compound action potential (ECAP), according to a standardised postoperative measurement procedure. Recordings were obtained in 96% of these subjects with this standardised procedure. The group results are presented in terms of peak amplitude and latency, slope of the amplitude growth function and ECAP threshold. The effects of aetiological factors and the duration of deafness on the ECAP were also studied. While large intersubject variability and intrasubject variability (across electrodes) were found, results fell within a consistent pattern and a normative range of peak amplitudes and latencies was established. The aetiological factors had little effect on the ECAP characteristics. However, age affected ECAP amplitude and slope of the amplitude growth function significantly; i.e., the amplitude is higher in the lowest age category (15-30 years). Principal component analysis of the ECAP thresholds shows that the thresholds across 5 electrodes can be described by two factors accounting for 92% of the total variance. The two factors represent the overall level of the threshold profiles ('shift') and their slopes across the electrode array ('tilt'). Correlation between these two factors and the same factors describing the T- and C-levels appeared to be moderate, in the range of 0.5-0.6.

Action Potentials↗
PubMed2004

Occurrence of del(GIB6-D13S1830) mutation in Italian non-syndromic hearing loss patients carrying a single GJB2 mutated allele.

Molecular screening for GJB2 (connexin 26) mutations represents the standard diagnostic approach for the genotype definition of non-syndromic deafness. Nevertheless, a single GJB2 pathogenic mutation is detectable in a relevant number of cases, therefore failing to explain the phenotype. We aimed at assessing the occurrence of the recently described del(GIB6-D13S1830) mutation, occurring in the connexin 30 gene, in a group of Italian hearing-impaired patients carrying a single GJB2 mutated allele. A total of 59 non-syndromic hearing loss (NSHL) patients were screened for GJB2 mutations. Among these, nine NSHL patients were found to be heterozygous for a single GJB2 mutation. These patients, heterozygotes for different GJB2 mutated alleles (35delG, L90P, M34T, V153I), together with 11 additional 35delG/neg cases previously described, were studied for the presence of the del(GIB6-D13S1830) mutation. Two double heterozygotes del(GIB6-D13S1830)/35delG were identified. In both cases the degree of hearing loss was profound. Furthermore, GJB2 molecular screening led to the identification of a novel change (T55G) occurring in compound heterozygosity with the V37I mutation. In conclusion, our data suggest a significant frequency of del(GIB6-D13S1830) mutation in Italian hearing-impaired subjects (10% of unexplained GJB2 heterozygotes) similar to that reported in other European countries.

Connexin 26↗
PubMed2002

Exploring the clinical and epidemiological complexity of GJB2-linked deafness.

GJB2 mutation analysis was performed in 179 unrelated subjects with sporadic or familial hearing loss (HL). Among 57 families, 18 showed a vertical transmission of HL, the disease being present in two or three generations. Besides 155 nonsyndromic cases, 24 patients presenting with extra-auditory clinical signs were included in the molecular study. GJB2 mutation analysis was also performed in 19 subjects with an anamnestic history of perinatal risks factors for acquired HL. The 35delG mutation accounted for 22.1% of analyzed chromosomes in sporadic cases and 39.4% in familial cases; 35delG prevalence reached 41% in autosomal recessive and 44.4% in pseudodominant pedigrees. Two novel GJB2 mutations were identified in compound heterozygosity with 35delG allele (D159V, 284ins/dup[CACGT]). Two 35delG homozygous subjects were identified among HL cases classified as environmental in origin. Four patients 35delG heterozygous (35delG/V95M, 35delG/L90P, 35delG/167delT, and 35delG/?) and two homozygous presented with extra-auditory clinical signs involving different organs (skin, vascular system, hemopoietic lineages, and thyroid). In a high proportion of 35delG heterozygous HL patients (52%), no second GJB2 mutation was detected. The reported data highlight the complexity of the genetic epidemiology of GJB2-linked deafness, further enlarging the spectrum of situations in which GJB2 mutation analysis should be performed. The presence of extra-auditory signs in a significant portion of GJB2-mutated patients suggests the possibility that GJB2 loss of function could contribute to clinical phenotypes presenting in association with deafness. This hypothesis deserves further investigation. The failure to identify a presumed partnering GJB2 mutation in a high proportion of deaf patients remains a challenging problem to be clarified.

Amino Acid Sequence↗
PubMed1989

[Evoked potentials of the brain stem in normal and pathologic conditions: experience with 692 adult subjects].

The main purpose of the study of evoked potentials has always been to objectively evaluate hearing thresholds in uncooperative subjects and it has become increasingly important in recent years with the introduction of auditory brainstem responses (ABR). Reading the ABR is relatively simple in terms of "audiometry" since it is based on the absence, or presence, of a marker peak wave V. Besides the strictly audiometric uses, study of the bioelectric brainstem complex even makes it possible to obtain important information regarding retrocochlear dysfunction. However, reading the response is not so simple for the otoneurologist since it is not based only on the observation of the absence or presence in order to compare the normal values obtained in homogeneous groups. For the above reason auditory brainstem response testing was performed on 692 subjects in order to define the normal values as well as any characteristic patterns for various audiological pathologies. For all subjects auditory brainstem responses were recorded mono-aurally with clicks of alternating polarity, 11 and 31 pps, at an intensity of 120 dB SPLpe. Use was made of ipsilateral stimulus derivations. Only for the right ear was absolute wave V latency measured at 100 and at 80 dB SPLpe. The amplifier of the bioelectric signal was set at a sensitivity of 20 microvolts with passing filters of 100 and 2000 Hz. Absolute latency, conduction time, symmetry indexes (IT I-V and ITV) and the shift in latency at the two stimulation cadences were statistically processed for homogeneous groups. Thus standards for normality were obtained. The results have shown that the following biological variables are to be taken into consideration: sex, age for males and type of deafness. The indexes most reliable in identifying a retrocochlear dysfunction proved to be: morphological completeness, central I-V conduction times and the two symmetry indexes IT I-V and ITV which are considered complementary. Again in terms of identifying a retrocochlear dysfunction, and in case of an incomplete response, the test can be interpreted thanks to the so-called minor responses which only take into account the absolute wave V latency. However, wave V latency behaviour is rather similar to what has been found in conductive hearing-loss. Finally, in cochlear deafness it was found that response did not vary with a variation in degree of deafness since the results produced were similar to those of normal hearing subjects except in those cases where there was a delay in the appearance of wave I.

Adult↗
PubMed1979

[Stereophonic apparatus: our hearing aid test].

The authors wanted to verify the advantages produced by binaural amplification in the loudness and in the speech identification. To value the improvement in speech identification they used the Jerger's test (1976); and to value the loudness improvement they measured, gain characteristics of the aid with monoaural and binaural amplification. They executed the test on 50 hearing aid users, chosen among 10 and 84 years old, suffering from sensorineural bilateral hearing loss between 40 and 80 dB. It results that : 1. The gain obtained by the use of binaural amplification is 5 dB lower than the one obtained by monoaural. 2. The binaural amplification permits a remarkable advantage in speech identification, the advantage is directly proportionated to deafness. The authors conclude that the described test is valid, simple and that it is possible to apply it by cheap instruments.

Adolescent↗
PubMedDate not supplied

[Temporal bone metastasis of adenocarcinoma of the breast: personal observations and a review of the literature].

A single case of temporal bone metastases from breast carcinoma is reported and its clinical features and main instrumental diagnostic characteristics are described. Although this is quite rare the possibility cannot be neglected when making diagnosis should the clinical features and test results suggest such an expansive process of the temporal bone. In fact, although extremely limited, treatment is strictly linked to proper and early diagnosis.

Breast Neoplasms↗