1,720,997 research outputs found
The behaviour of wave V latency in cochlear hearing loss
No full textThe audiological approach to the early diagnosis of cerebellopontine angle tumours (APC) is based mainly on ABR. In present work, wave V latency has been studied in two groups of patients: 308 cochlear cases and 74 retrocochlear cases (APC surgically confirmed tumours), in order to increase the sensitivity and specificity of the diagnostic indexes I-V, IT5 and Delta V. Wave V latencies have been evaluated in relation to hearing loss at 2-4 kHz and audiometric profile. Both these factors show a highly significant positive correlation with the latency, which consequently increases proportionally to hearing loss and high-frequency audiometric loss. A multiple regression analysis was therefore used to analyse the effects from the two variables, and a correction factor was calculated to compensate the latency values for hearing loss and threshold configuration. The effects of such a correction on the clinical results consist mainly of a reduction in the rate of cochlear false-negative results, which corresponds to improving the ABR specificity
Influence of a CNS pathology on the electrocochleography response
No full textThis study analyzed 73 electrocochleographic recordings made in children with a normal hearing threshold, selected retrospectively from 1563 recordings made between 1973 and 1990. The aim of the study was to check the original findings for any correlation between the various response parameters which might be indicative of a pathological condition. Compound action potential (AP) latency and amplitude, presynaptic summation potential (SP) and cochlear microphonic (CM) amplitudes and AP rapid adaptation behavior were calculated and recordings were associated with clinical information on aetiologic diagnosis, otoscopic examination, impedance measurement data and the finding of any central nervous system (CNS) pathology. The trend of the amplitudes as a function of the intensity of all three potentials (input-output functions), CM and SP in particular, demonstrated unexpected scattered values especially towards the high intensities. This was found correlated to the presence of CNS pathology. The comparison between the two groups (with vs without CNS pathology) with the aid of the Student's t-test proved statically significant, especially for CM and SP amplitudes while rather less so for AP amplitude. In particular, all CM and SP amplitude values outside the confidence intervals (calculated as 95% of normal cases) revealed CNS pathology. It has been suggested that the influence of the CNS on cochlear function is due to a disturbed function of the olicocochlear bundle, which is known to have an inhibitory effect on cochlear dynamics; furthermore, there is also proof that it can be activated regardless of any ipso-and/or contra-lateral acoustic stimulation. The effects observed on the electrocochleography in cases with CNS disorders would thus be explained by an interruption of the olivocochlear bundle at the CNS level or a disruption of the CNS mechanism capable of controlling its activation
In tema di predimensionamento dei ponti a cassone in calcestruzzo armato ed in calcestruzzo armato precompresso
No full textCorrelazioni fra dati clinico-audiologici e potenziali evocati uditivi del tronco dell'encefalo
No full textClinical applicability of transient evoked otoacoustic emissions: identification and classification of hearing loss.
No full textThe study aimed at the development of a clinically applicable methodology that could: (1) discriminate transient evoked otoacoustic emission (TEOAE) recordings from normal hearing or hearing impaired individuals; (2) classify the nature of the hearing loss as conductive or as cochlear, and (3) define clear-cut TEOAE clinical criteria. A classification algorithm based on a multivariate discriminant analysis of fast Fourier transform data from recordings evoked by click stimuli of 50 +/- 2, 62 +/- 2, 68 +/- 2 and 80 +/- 2 dB SPL was used to discriminate 302 normal subjects from 383 subjects suffering from mild to moderate hearing losses. The best discriminant model (QDF80) produced a sensitivity of 93.8% and a specificity of 79.4%. When extra correlation criteria were serially applied to the classification outcome, the specificity was increased to 85.3%, but the sensitivity was marginally decreased to 91.7%. The classification of the correctly identified hearing-impaired cases yielded 93.8% identification of conductive and 75.1% identification of cochlear cases. A sensitivity analysis of the misclassified hearing-impaired cases suggested that the TEOAE spectra are well correlated with the 2-kHz but poorly correlated with the 4-kHz octave frequency
Contribution of age-related factors to the progression of non-syndromic hereditary hearing impairment
No full textQuantitative abnormalities in nystagmus induced by caloric stimulation in multiple sclerosis
No full textVestibular nystagmus induced by caloric stimulation (20 degrees and 44 degrees C) was evaluated in terms of duration, frequency and slow phase velocity in 80 patients suffering from clinically defined multiple sclerosis. Criteria of abnormality were established with reference to 3 confidence levels from normative data of a 15-subject control group. Abnormal data representative of vestibular hypo- and hyperreflexia were found ranging between 27 and 53% depending on different parameters and diagnostic criteria. Significant differences in occurrence of nystagmus abnormalities became evident by analyzing 6 different windows of the vestibular response. Different distributions of hypo- and hyperreflexia were observed in relation to the time-course of the normal cumulative response curve, as well as to different stimulus temperatures. For each subject the abnormal data of the 2 stimulated ears X 2 caloric stimulations X 6 analysis windows were cumulated, yielding an overall outcome of pathological results in 66% to 90% of the patients, depending on the different diagnostic criteria
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