Trastornos específicos del lenguaje e hipoacusia / Specific language impairments and deafness

La posibilidad de que el trastorno específico del lenguaje (TEL) se observe en niños con hipoacusia se basa en la evidencia de que un porcentaje de niños con implante coclear (IC) no parecen beneficiarse de ese dispositivo y persisten en unas formas lingüísticas muy limitadas. Se discute el posible encaje del TEL en los niños con IC a partir de los criterios del TEL aceptados por la comunidad científica internacional. Se revisan algunas propuestas que tratan de describir el lenguaje y las conductas comunicativas de los niños sordos afectados de TEL. El panorama resultante es confuso, intratable por la cantidad de síntomas propuestos con un nivel bajo de especificidad. Se pone de relieve la confusión acerca del atributo de «específico» en estas propuestas: no existen síntomas lingüísticos específicos del TEL; «específico» se refiere a que el trastorno es primario, no consecuente a retraso cognitivo, a malformaciones de los órganos de la articulación, a limitaciones perceptivas, a enfermedad neurológica o a alteraciones cualitativas en la interacción social. Se revisan datos obtenidos de investigaciones en las que se compara el lenguaje de niños con IC y niños oyentes, de niños con IC con lenguaje limitado y sin esa limitación, etc. A partir de esos resultados se concluye que no es apropiado utilizar la expresión TEL para referirse al lenguaje limitado de algunos niños con IC y se proponen, simplemente como tentativa, unos criterios claros para la identificación de los niños con IC que persisten en un lenguaje muy limitado (AU)

The possibility that a Specific Language Impairment (SLI) may be observed in children with hearing loss is based on the evidence that a percentage of children with cochlear implant (CI) do not seem to benefit from that device, and only limited linguistic forms persist in them. The possibility of using the diagnosis SLI for children with CI is discussed. Criteria describing SLI accepted by the international scientific community was used for this purpose. The proposals that describe the language and communicative behaviours of children with hearing impairment affected with SLI are reviewed. The resulting picture is blurry and intractable, because of the amount of symptoms proposed with a low level of specificity. The confusion about the attribute of ‘specific’ in these proposals is emphasised. There are no specific linguistic symptoms of SLI, and ‘specific’ refers to the primary nature of impairment, not due to cognitive retardation, malformations of the organs of articulation, perceptual limitations, neurological disease, or qualitative alterations in social interaction. Data from research comparing the language of children with CI and hearing children, children with CI with limited language and without this limitation, etc. are revised. It is concluded from these results that the expression ‘SLI’ referring to limited language of some children with CI is not appropriate. Some clear criteria are tentatively proposed in order to identify children with CI who persist with a very limited language (AU)

Changes in utricular function during artificial endolymph injections in guinea pigs.

Various theories suggest endolymphatic hydrops may cause a rupture of the membranous labyrinth or may force open the utriculo-saccular duct, resulting in a sudden change in inner ear function. Here, we have used slow injections of artificial endolymph into either scala media or the utricle of anaesthetised guinea pigs to investigate the effects of hydrops. Vestibular function was continuously monitored in addition to the measurements of cochlear function developed in our laboratory (Brown et al. Hear Res, 2013). Scala media injection induced consistent functional changes, which occurred in two stages. Initial changes involved were associated with an increased hydrostatic pressure in scala media that only affected cochlear function. After 3-4 µl of endolymph had been injected, cochlear function spontaneously recovered, and was often shortly followed by a transient increase or decrease in utricular sensitivity, with the effects varying between animals. Endolymph injection directly into the utricle produced variable effects across animals, although in 2 experiments it produced similar changes as those observed for scala media injections, suggesting that the fluid pathway between scala media and the utricle was continuous in these animals. The mechanism underlying the sudden, spontaneous functional changes is not yet clear, but we tentatively suggest that in some cases it may be caused by the utriculo-saccular duct suddenly opening to alleviate an elevated hydrostatic pressure in the pars inferior, resulting in a change in utricular function due to an increase in its volume. These changes are comparable to the sudden or fluctuating functional changes in Ménière's sufferers, and support the hypothesis that endolymphatic hydrops can directly cause some symptoms of this syndrome.

Evolución de la otosclerosis hacia la implantación coclear / Evolution of otosclerosis to cochlear implantation

Introducción: La otosclerosis es una osteodistrofia de la cápsula laberíntica que produce hipoacusia de conducción. Si el proceso invade la cóclea, aparece una hipoacusia neurosensorial, siendo el implante coclear una buena alternativa en estos pacientes. Objetivo: Conocer el comportamiento de la otosclerosis en la implantación coclear. Material y métodos: Se revisó una base de datos de 250 pacientes intervenidos de implante coclear realizando un estudio retrospectivo sobre 13 pacientes con criterios clínicos, audiológicos y/o de imagen de otosclerosis bilateral. Se estudian los 26 oídos analizando la historia natural, cirugías previas, evolución hacia hipoacusia profunda, hallazgos en imagen mediante tomografía computarizada, complicaciones y resultados funcionales. Resultados: El 46% fueron mujeres y el 54% hombres con una edad media de 26 años al inicio de la hipoacusia conductiva. La cirugía del estribo fue llevada a cabo en 19 oídos (73%) a una edad media de 29 años y de estos en el 53% se realizó posteriormente un implante coclear. Los resultados de la tomografía computarizada muestran que en el 54% de los oídos existen signos de afectación radiológica en diferente grado. Se registraron un total de 3 complicaciones (23%): un fallo de implante coclear, una estimulación del nervio facial y un acúfeno bilateral. Al año de la implantación obtenemos un porcentaje promedio de aciertos en bisílabos del 80% y del 85% en frases en contexto abierto. Conclusiones: Pacientes que presentan una hipoacusia neurosensorial profunda bilateral secundaria a una otosclerosis se benefician extraordinariamente de la implantación coclear(AU)

Introduction: Otosclerosis is an osteodystrophy of the labyrinthine capsule producing conductive hearing loss. If the process invades the cochlea, a sensorineural hearing loss usually takes place. The cochlear implant is a good alternative in these patients. Objective: To ascertain the behaviour of cochlear implantation in otosclerosis. Material and methods: We reviewed a database of 250 patients that underwent cochlear implantation, performing a retrospective study of 13 patients with clinical, audiological and/or imaging findings of bilateral otosclerosis. The 26 ears were studied as to their natural history, previous surgeries, evolution to profound hearing loss, computed tomography images, complications and functional results. Results: Of the cases studied, 46% were female and 54% were men, with a mean age of 26 years at the onset of conductive hearing loss. Stapes surgery was performed in 19 ears (73%), with a mean patient age of 29 years, and 53% of them underwent cochlear implantation. Computed tomography results showed that there were signs of different degrees of radiological affectation in 54% of the ears. A total of 3 complications took place (23%): implant failure, overstimulation of the facial nerve and bilateral tinnitus were found. One year after implantation, the average percentages of correct 2-syllable words were 80% and 85% in open sentences. Conclusions: Patients having profound bilateral sensorineural hearing loss secondary to otosclerosis obtain great benefit from cochlear implantation(AU)

Blockage of reuniting duct in Meniere's disease.

CONCLUSION: The bony saccular orifice to the bony groove of the ductus reuniens (reuniting duct) could not be visualized in the Meniere's ear with significantly greater frequency compared with normal subjects, which suggests that the reuniting duct is affected by radio-opaque substances in CT findings. OBJECTIVE: This study investigated a more specific, objective, and simpler strategy to diagnose Meniere's disease by assessing the reuniting duct. SUBJECTS AND METHODS: We examined the ears of 12 patients with definitely diagnosed unilateral Meniere's disease in stage 3 based on Meniere's disease criteria proposed by the Committee on Hearing and Equilibrium of the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS), and the ears of 12 normal control subjects using three-dimensional (3D) cone beam CT. RESULTS: The bony groove of the reuniting duct between the saccule and cochlea was visualized in all control subjects. However, the bony saccular orifice to the bony groove could not be visualized in the lesional ear of Meniere's patients with significantly greater frequency compared with those of the contralateral non-lesional ears and control ears (p < 0.01). This orifice was not patent in 66.7% (8 of 12 ears) on the lesional side but all contralateral non-lesional ears of the patients and normal control ears were patent.

Estimating the operating point of the cochlear transducer using low-frequency biased distortion products.

Distortion products in the cochlear microphonic (CM) and in the ear canal in the form of distortion product otoacoustic emissions (DPOAEs) are generated by nonlinear transduction in the cochlea and are related to the resting position of the organ of Corti (OC). A 4.8 Hz acoustic bias tone was used to displace the OC, while the relative amplitude and phase of distortion products evoked by a single tone [most often 500 Hz, 90 dB SPL (sound pressure level)] or two simultaneously presented tones (most often 4 kHz and 4.8 kHz, 80 dB SPL) were monitored. Electrical responses recorded from the round window, scala tympani and scala media of the basal turn, and acoustic emissions in the ear canal were simultaneously measured and compared during the bias. Bias-induced changes in the distortion products were similar to those predicted from computer models of a saturating transducer with a first-order Boltzmann distribution. Our results suggest that biased DPOAEs can be used to non-invasively estimate the OC displacement, producing a measurement equivalent to the transducer operating point obtained via Boltzmann analysis of the basal turn CM. Low-frequency biased DPOAEs might provide a diagnostic tool to objectively diagnose abnormal displacements of the OC, as might occur with endolymphatic hydrops.

Efecto acústico inmediato de la fístula coclear en el cobaya / Immediate acoustic effect of the cochlear fistula in a guinen pig

Introducción y objetivos: Evaluar el efecto que tiene en la cóclea la cocleostomía así como la exposición de la estría vascular, valorándolo de manera objetiva por medio de las otoemisiones acústicas e inmediatamente a la intervención. Material y métodos: Abordaje submandibular al oído medio y cóclea del cobaya. Fresado de las rampas timpánica y vestibular de la primera espira así como exposición amplia de la estría vascular en la primera-segunda espira. Estudio de la función coclear por medio de otoemisiones acústicas de productos de distorsión. Conclusiones: El cobaya es un animal de experimentación idónea para el trabajo quirúrgico cuando se pretende monitorizar el estado funcional de la cóclea. La respuesta acústica es similar a la encontrada en otros mamíferos aunque la amplitud de la respuesta es algo inferior a lo referido en otros trabajos. La ausencia de manipulación intracoclear asegura la reducción de deterioro auditivo de acuerdo a los hallazgos en las diferentes maneras de estudio del producto de distorsión acústico. Resultados: Existe una reducción de la amplitud en los audiogramas de productos de distorsión para determinadas frecuencias (4 y 6 kHz). Estas son las de localización tonotópicamente próximas a las cocleostomías realizadas en la primera espira (al nivel de la escala vestibular y timpánica). La apertura de la cóclea sin realizar una manipulación intracoclear no ocasiona modificaciones severas en los resultados de los audiogramas de productos de distorsión ni en las curvas de crecimiento de la respuesta. La apertura lateral de la estría vascular minimizando la agresión al laberinto no provocó deterioro acústico significativo

Introduction and objectives: To Evaluate objectively the effect that cochleostomy has in the cochlea as well as the exposition of the estria vascularis, through acoustic otoemissions immediatly after surgery. Material and methods: Submandibular approach to the guinea pig’s middle ear and cochlea. Triming of the timpanic and vestibular first turns and wide exposition of the estria vascularis in the first and second turns. Study of cochlear function through acoustic otoemissions of distortion products. Conclusions: Guinea Pig is a perfect experimentation animal for surgical work when monitoring functional state of the cochlea. Its acoustic response is similar to the one found in other mammals thoug its response is lower than that reported in other papers. The lack of intracochlear manipulation ensures the lower decrease hearing loss deterioration regarding the findings in the different methods of studying the acousting distortion. Results: There is a decrease of amplitud in the audiograms of distortion for specific frequencies (4 and 6 KHz), located tonotopically near the cochleostomies carried out in the first turn (at the level of scala vestigularis and timpanic). Approadring the cochlea without intracochlear manipulation does not modify greathy the results of audiograms of distortion neither the growth slopes of the response. A lateral approach of the estric vascularis minimising the aggression to labrynth did not cause a significant acoustic deterioration

Sordera súbita. Hallazgos en la hemorragia coclear / Sudden deafness: findings in cochlear hemorrhage

La sordera súbita debida a hemorragia laberíntica es una entidad clínica relativamente poco frecuente, y puede ser el único hallazgo demostrable en el estudio de neuroimagen de la sordera súbita, bien como hecho aislado o ligado a una laberintitis, en forma de hiperintensidad laberíntica en secuencias potenciadas en T1 de la resonancia magnética (RM), sin objetivarse refuerzo laberíntico tras la administración de contraste. Presentamos un caso en el que la hemorragia coclear produjo una sordera súbita en una mujer de 22 años previamente asintomática. Revisamos la bibliografía y evaluamos el papel de la existencia de hiperintensidad en los estudios de RM craneal

Sudden deafness owing to labyrinth hemorrhage is a relatively rare clinical entity; labyrinth hemorrhage may be the only demonstrable finding in neuroimaging studies performed for sudden deafness, whether as an isolated finding or associated with labyrinthitis, manifesting as labyrinth hyperintensity in T1-weighted MRI sequences without enhancement after contrast administration. We present a case in which cochlear hemorrhage caused sudden deafness in a previously asymptomatic 22-year-old woman. We review the literature and evaluate the role of the presence of hyperintensity in cranial MRI

Effects of hyperbaric therapy on function and morphology of Guinea pig cochlea with endolymphatic hydrops.

OBJECTIVE: The objective of this study was to investigate the effect on experimental endolymphatic hydrops in guinea pigs after hyperbaric therapy. BACKGROUND: The histopathologic character of Ménière's disease is the presence of endolymphatic hydrops. Endolymphatic hypertension could be one of the factors resulting from endolymphatic hydrops. Some treatments of Ménière's disease are aimed toward preventing the endolymphatic hypertension. Exposure to pressure change has risen in recent years. METHODS: Thirty-two guinea pigs were operated on the right ears to induce endolymphatic hydrops by obliterating the endolymphatic sac through an extradural posterior cranial fossa approach. After 5 weeks' survival, 12 guinea pigs were put into a chamber with an absolute atmospheric pressure of 2.2 for 3 weeks (90 minutes once a day 5 times a week). We observed the morphologic and functional changes in guinea pig cochleae of the pressure group, 4-week hydrops group (n = 10), 8-week hydrops group (n = 10), and the normal group (n = 10). We measured the hearing threshold of the auditory brainstem response, the 70-dB SPL action potential (AP) latency, the ratio of 70-dB SPL summating potential magnitude to action potential magnitude (-SP/AP) of the electrocochleogram, and the maximum scala media area (SMA) ratio, respectively. RESULTS: The average 70-dB SPL-SP/AP magnitude of right ears (0.29 +/- 0.09) and the average maximum SMA ratio (2.23 +/- 0.20) in the pressure group were significantly less than that in the 8-week hydrops group (0.69 +/- 0.15 and 4.04 +/- 0.52, respectively) with the same survival time (p < 0.05). The results in the pressure group were almost as similar as that in the 4-week hydrops group (0.29 +/- 0.13 and 2.22 +/- 0.20, respectively) (p > 0.05). The average hearing threshold of ABR of right ears in the pressure group (36.67 +/- 14.30-dB SPL) was lower than that of the 8-week hydrops group (44 +/-1 4.30-dB SPL), but the difference was insignificant (p > 0.05). The average 70-dB SPL AP latency of right ears in the pressure group was not significantly different from those of the 8-week hydrops group, the 4-week hydrops group, or the normal group (p > 0.05). CONCLUSIONS: Our findings suggest hyperbaric therapy can significantly suppress the development of endolymphatic hydrops and improve cochlear function in guinea pigs. This study provided strong evidence for the development of pressure treatment of Ménière's disease without destroying the inner ear.

Correlation between hearing loss and scala media area in guinea pigs with long-standing endolymphatic hydrops.

HYPOTHESIS: Histologic analysis of the hydropic and normal guinea pig cochleae was undertaken to assess a potential correlation between the magnitude of endolymphatic hydrops and hearing loss. It was hypothesized that a greater correlation than previously reported might be found by looking at long-standing endolymphatic hydrops and high-frequency range hearing. BACKGROUND: Surgically induced endolymphatic hydrops in guinea pigs is the most widely used animal model for the study of human Ménière's Disease and recapitulates both endolymphatic hydrops and progressive sensorineural hearing loss. A strong correlation between the magnitude of hydrops and severity of hearing loss has been reported in the human condition, but not in the animal model. METHODS: Nine albino guinea pigs were each subjected to surgical obstruction of the endolymphatic sac and duct of the right ear. The left ears remained as internal histologic controls. Hearing was assessed from 2 kHz to 32 kHz by auditory brain stem response testing for 16 to 25 weeks after surgery. Histologic morphometry after the animals were killed was used to quantify both turn-specific and weighted overall hydrops. These measures were correlated with hearing loss in each animal at all tested frequencies. RESULTS: A statistically significant correlation between the magnitude of hydrops and the severity of hearing loss was observed for 2 kHz and 16 kHz. These frequencies correlated with both turn-specific hydrops and overall hydrops. However, turn-specific hydrops did not reliably correlate with the magnitude of hearing loss at anatomically appropriate frequency ranges. Where such a correlation did exist, it might well have been simply part of an expression of an overall correlation between hydrops and hearing loss. CONCLUSIONS: There may be a greater correlation between hydrops and hearing loss in guinea pigs with long-standing surgically induced hydrops than has previously been reported in animals with less advanced disease. These findings help to validate continued use of the model for hearing loss related to Ménière's Disease, verify the rationale of treatment modalities aimed at reducing hydrops in the human condition, and may indicate that efforts at reducing hydrops in such patients has benefits toward long-term hearing preservation.

Experimental studies of vibratory trauma of Corti's organ. I: Electrophysiological measurements.

In the present-day environment, vibration concomitant with noise is most frequently observed, but even though it is regarded as only a weak, additional traumatic factor affecting the organ of hearing. This opinion is contrary to a number of reports on the damage of the hearing organ caused by vibration in workers of various branches of industry. As experiments on humans are rather difficult, the harmful effect of vibration is usually examined on laboratory animals. In the majority of studies dealing with this problem the presence of noise (purposely or casually) was found in most cases. The aim of this study was to determine the effect of isolated long-term whole-body vibration and vertical sinusoidal shaking (10 Hz frequency, 5 mm amplitude, and 2 g acceleration) on Corti's organ. The study was carried out on young guinea pigs of both sexes. Eighty four animals (30 control and 54 experimental) with Preyer's reflex and without otoscopically detectable changes were used. A group of 18 animals was subjected to vibration in noiseless shaking apparatus for 30, 90 and 180 days. After a one-month rest, cochlear microphonics were performed under urethane anaesthesia. Our modification of the phase-sensitive detection method was used. Cochlear microphonics at frequencies of 260 Hz, 500 Hz, 1 kHz and 2 kHz was recorded from the apex of the cochlea and for 4 kHz and 8 kHz from the region of the round window. As the cochlear microphonics values showed significant individual differences, all experimental samples were examined by means of non-parametric tests. The outcome of the study demonstrated a gradual but considerable cochlear microphonics voltage decrease in the range to 2 kHz. This result pointed to the generation of vibration-induced damage in outer hair cells of the fourth and third turnings of the cochlea in the guinea pigs under study.

Changes in off-lesion endocochlear potential following localized lesion in the lateral wall.

Endocochlear potential (EP) was measured at various off-lesion sites after a small focal lesion was made in the lateral wall of the guinea pig cochlea. Lesions were produced by a photochemical reaction between systemically administered rose bengal and focused green light illumination. In 21 ears, continuous measurement for 30 min after onset of the reaction at turns apical or basal to the site of illumination revealed no significant changes in EP compared with the control value (p < 0.01). In another group of 43 ears, EP was measured at 3 days post-illumination. A significant decline was seen at every site located apical to the lesion (p < 0.001). Conversely, no significant change was measured at any site located basal to the lesion. These findings suggest that the decrease in EP assumes the form of a gradient from the lower to upper turns in the guinea pig cochlea.

Estudio descriptivo asobre la evolución madurativa de la función latencia-intensidad a la onda y su valor en el diagnóstico diferencial objetivo de las hipoacusias / Description study about the evolution madurative of the function latent-intensity to the wave and his value in the diferential diagnostic objective of the hypoacusias

El propósito del trabajo es el de estudiar la evolución madurativa de la función latencia-intensidad a la onda V, evaluar su valor en el diagnóstico diferencial objetivo de las hipoacusias, y también determinar su comportamiento en pacientes normales y con hipoacusia, obteniendo de esta forma myor conocimiento e información sobre esta función de los Potenciales Evocados Auditivos de Trono Cerebral (P.E.A.T.C). Las variables consideradas son evolución madurativa de la función latencia-intensidad a la onda V y valor en el diagnóstico diferencial objetivo de las hipoacusias. Se trabaja con una muestra constituída por 377 casos (oídos) con audición normal, hipocusia de conducción, coclear y retrocolear que se registran entre el mes de Enero del año 1991 hasta Mayo de 1997, en los archivos del Instituto de Neurociencias San Lucas de la ciudad de Rosario. El tipo de estudio es descriptivo, longitudinal y ex-post-facto. Las conclusiones a las que se arriban son que, la función latencia-intensidad estimada, muestra los cambios madurativos: los valores de latencia van disminuyendo desde el nacimiento hasta alcanzar los valores de latencia adultos. Estos se obtienen a la edad comprendida entre mayores de un ño y hasta dos años. La función latencia-intensidad presenta un desplazamiento en forma gradual y el comportamiento no se encuentra alterado debido a que el mismo es similar en todas las edades. El valor de la función latencia-intensidad estimada es el de poder utilizarla en el diagnóstico diferencial objetivo de las hipoacusias con un determinado nivel de confianza

Estudio descriptivo asobre la evolución madurativa de la función latencia-intensidad a la onda y su valor en el diagnóstico diferencial objetivo de las hipoacusias / Description study about the evolution madurative of the function latent-intensity to the wave and his value in the diferential diagnostic objective of the hypoacusias

El propósito del trabajo es el de estudiar la evolución madurativa de la función latencia-intensidad a la onda V, evaluar su valor en el diagnóstico diferencial objetivo de las hipoacusias, y también determinar su comportamiento en pacientes normales y con hipoacusia, obteniendo de esta forma myor conocimiento e información sobre esta función de los Potenciales Evocados Auditivos de Trono Cerebral (P.E.A.T.C). Las variables consideradas son evolución madurativa de la función latencia-intensidad a la onda V y valor en el diagnóstico diferencial objetivo de las hipoacusias. Se trabaja con una muestra constituída por 377 casos (oídos) con audición normal, hipocusia de conducción, coclear y retrocolear que se registran entre el mes de Enero del año 1991 hasta Mayo de 1997, en los archivos del Instituto de Neurociencias San Lucas de la ciudad de Rosario. El tipo de estudio es descriptivo, longitudinal y ex-post-facto. Las conclusiones a las que se arriban son que, la función latencia-intensidad estimada, muestra los cambios madurativos: los valores de latencia van disminuyendo desde el nacimiento hasta alcanzar los valores de latencia adultos. Estos se obtienen a la edad comprendida entre mayores de un ño y hasta dos años. La función latencia-intensidad presenta un desplazamiento en forma gradual y el comportamiento no se encuentra alterado debido a que el mismo es similar en todas las edades. El valor de la función latencia-intensidad estimada es el de poder utilizarla en el diagnóstico diferencial objetivo de las hipoacusias con un determinado nivel de confianza(AU)

Estudio descriptivo asobre la evolución madurativa de la función latencia-intensidad a la onda y su valor en el diagnóstico diferencial objetivo de las hipoacusias / Description study about the evolution madurative of the function latent-intensity to the wave and his value in the diferential diagnostic objective of the hypoacusias

El propósito del trabajo es el de estudiar la evolución madurativa de la función latencia-intensidad a la onda V, evaluar su valor en el diagnóstico diferencial objetivo de las hipoacusias, y también determinar su comportamiento en pacientes normales y con hipoacusia, obteniendo de esta forma myor conocimiento e información sobre esta función de los Potenciales Evocados Auditivos de Trono Cerebral (P.E.A.T.C). Las variables consideradas son evolución madurativa de la función latencia-intensidad a la onda V y valor en el diagnóstico diferencial objetivo de las hipoacusias. Se trabaja con una muestra constituída por 377 casos (oídos) con audición normal, hipocusia de conducción, coclear y retrocolear que se registran entre el mes de Enero del año 1991 hasta Mayo de 1997, en los archivos del Instituto de Neurociencias San Lucas de la ciudad de Rosario. El tipo de estudio es descriptivo, longitudinal y ex-post-facto. Las conclusiones a las que se arriban son que, la función latencia-intensidad estimada, muestra los cambios madurativos: los valores de latencia van disminuyendo desde el nacimiento hasta alcanzar los valores de latencia adultos. Estos se obtienen a la edad comprendida entre mayores de un ño y hasta dos años. La función latencia-intensidad presenta un desplazamiento en forma gradual y el comportamiento no se encuentra alterado debido a que el mismo es similar en todas las edades. El valor de la función latencia-intensidad estimada es el de poder utilizarla en el diagnóstico diferencial objetivo de las hipoacusias con un determinado nivel de confianza(AU)

Estudio descriptivo asobre la evolución madurativa de la función latencia-intensidad a la onda y su valor en el diagnóstico diferencial objetivo de las hipoacusias / Description study about the evolution madurative of the function latent-intensity to the wave and his value in the diferential diagnostic objective of the hypoacusias

El propósito del trabajo es el de estudiar la evolución madurativa de la función latencia-intensidad a la onda V, evaluar su valor en el diagnóstico diferencial objetivo de las hipoacusias, y también determinar su comportamiento en pacientes normales y con hipoacusia, obteniendo de esta forma myor conocimiento e información sobre esta función de los Potenciales Evocados Auditivos de Trono Cerebral (P.E.A.T.C). Las variables consideradas son evolución madurativa de la función latencia-intensidad a la onda V y valor en el diagnóstico diferencial objetivo de las hipoacusias. Se trabaja con una muestra constituída por 377 casos (oídos) con audición normal, hipocusia de conducción, coclear y retrocolear que se registran entre el mes de Enero del año 1991 hasta Mayo de 1997, en los archivos del Instituto de Neurociencias San Lucas de la ciudad de Rosario. El tipo de estudio es descriptivo, longitudinal y ex-post-facto. Las conclusiones a las que se arriban son que, la función latencia-intensidad estimada, muestra los cambios madurativos: los valores de latencia van disminuyendo desde el nacimiento hasta alcanzar los valores de latencia adultos. Estos se obtienen a la edad comprendida entre mayores de un ño y hasta dos años. La función latencia-intensidad presenta un desplazamiento en forma gradual y el comportamiento no se encuentra alterado debido a que el mismo es similar en todas las edades. El valor de la función latencia-intensidad estimada es el de poder utilizarla en el diagnóstico diferencial objetivo de las hipoacusias con un determinado nivel de confianza(AU)

Measurement of pressure and displacement of the membranous labyrinth in endolymphatic hydrops by the tensile test.

We measured the mechanical characteristics, particularly the strength of various regions of the membranous labyrinth by the penetration test with a specially designed machine. A load-displacement curve was drawn by the tensile test for the Reissner's and basement membranes. Additionally, a stress-strain curve was drawn. The modulus of elasticity was measured showing a straight line in the stress-strain curve: 1.5 x 10(2) mN/mm2 for Reissner's membrane and 9.3 x 10(2)-1.3 x 10(3) mN/mm2 for the basement membrane. Furthermore, the endolymphatic pressure was calculated at the point in time when the maximum strain as the limit of elasticity was 0.2. It was 81 Pa. The displacement of Reissner's membrane was 0.2 mm when the initial tension was taken as 0 in the formula, and that of the basement membrane was 3 to 37 microns when the initial tension was 0, 0.1, 0.2 and 0.3.

Is perilymphatic pressure altered in tinnitus?

Tinnitus is characterized by the continuous or intermittent auditory perception of various sounds (buzzing, whistling, etc.) in the absence of any external stimulus. Perilymphatic hyperpressure is one of the numerous mechanisms which could hypothetically be involved in tinnitus generation. In the present experiment, perilymphatic pressure was measured indirectly using the tympanic membrane displacement technique. Twenty-five tinnitus patients were investigated at 10, 15 and 20 dB above the acoustic reflex threshold with ipsilateral stimulation. The variables Vi (inward tympanic displacement), Vm (mean tympanic displacement) and their variations according to stimulus level were compared between tinnitus sufferers and age-matched or hearing-matched controls. Tympanic displacement was measured in sitting and supine positions so as to evaluate cochlear aqueduct patency. No systemic changes in response occurred in tinnitus patients, except at a high stimulation level, perhaps due to hearing impairment.

Endolymphatic hydrops in children.

Apart from clinical observations of Ménière's disease in children, there have only been a few histological descriptions of endolymphatic hydrops (EH) as an incidental finding in children. In this paper we report on the incidence of EH in temporal bones of children. One hundred eighteen temporal bones from 70 infants between newborn and 10 years (average age 12.9 months) were analyzed by light microscopy for EH of the cochlear duct, which was defined as a bulging of Reissner's membrane into the scala vestibuli in more than one turn of the cochlea. All endolymph spaces were carefully examined for factors such as an obliterated ductus reuniens which may have contributed to the development of EH. In 64 (54.2%) of the 118 temporal bones, a bulging of Reissner's membrane in the cochlear duct was found. In 65.6%, the bulging was confined to the apical turn and since the significance of isolated apical hydrops is controversial, we elected not to consider this group as having hydrops. Twenty (16.9%) bones met our criteria for a diagnosis of EH. Compared to the high incidence of bulging in the cochlear duct, fewer saccules and utricles were dilated. In approximately half of the temporal bones (49.2%), the ductus reuniens was collapsed. The ductus reuniens seems to be closed in its normal position and might open when pressure occurs due to an increasing volume of endolymph. If there is a permanent closure, EH may result. Our investigation does not indicate that EH is associated with a specific disease; however, where there were congenital anomalies the incidence of EH was higher.(ABSTRACT TRUNCATED AT 250 WORDS)

Daño auditivo inducido por ruido: revisión en 90 pacientes de alto riesgo / Noise induced injury. A 90 patients survey

Se estudiaron 90 pacientes expuestos a ambiente ruidoso, sin protección auditiva. Fueron clasificados en tres grupos: El primero con exposición hasta 60 decibeles, el segundo entre 60 y 90 decibeles y el tercero con exposición superior a los 90 decibeles. En el grupo I no se encontraron pacientes con daño auditivo. En el grupo 2 registro un 12.5 por ciento de incidencia de trauma acústico. En el grupo 3 se detectó un 46.6 por ciento de incidencia de trauma acústico. Con base en estos datos, concluimos que el daño auditivo tiene una relación directa con la intensidad del ruido. La susceptibilidad individual es otro factor determinante para el desarrollo de estas lesiones

Time course of endolymph volume increase in experimental hydrops measured in vivo with an ionic volume marker.

A new method has been developed to measure the cross-sectional area (CSA) of scala media in the living cochlea. The method has some advantages over histological methods, in which tissues may shrink or move during processing. In the present study, scala media CSA was measured in the second turn of guinea-pig cochleas in which endolymphatic hydrops was induced surgically. The area measurement method used an iontophoretic injection of a volume marker into scala media, during which the concentration of marker in endolymph was monitored with an ion-selective microelectrode. The measured marker concentration was inversely proportional to the CSA of endolymph. The marker we used was the anion arsenic hexafluoride (AsF6-), which was almost ideal for the purpose as it was retained well in endolymph. Area was measured in normal animals and in hydropic animals at times from 4 days to 16 weeks after endolymphatic duct obstruction. The results showed that hydrops develops within days of ablation of the endolymphatic duct. The degree of hydrops was compared with electrophysiological measures of function, including the endocochlear potential, action potential thresholds and the amplitudes of the cochlear microphonic, summating potential and action potentials. In the initial stages of hydrops development, electrophysiological changes were small. In contrast, there were marked functional changes between 8 and 16 weeks, when endolymph volume was no longer increasing. If the same is true for dysfunction in the ears of patients with Ménière's Disease, then it may not be possible to restore normal function simply by alleviating the hydrops.(ABSTRACT TRUNCATED AT 250 WORDS)