RESUMEN
INTRODUCTION: In view of the discrepancy between the siting of electrodes and the effects on BAEP, we made a morphological study of 30 healthy volunteers, 15 men and 15 women. DEVELOPMENT: In each person we obtained the BAEP with the active electrode on the ear lobe ipsilateral to the stimulated ear and the reference ear successively at four different sites: vertex (Cz), high frontal (Fz), earlobe contralateral to the stimulated ear and the spinous process of the seventh cervical vertebra (CV7). The I, III and V waves were present in all cases and tests, followed in frequency by II, IV and VII. In Cz and Fz the first five deflections were almost always seen, and these are the most useful for neurodiagnosis. The waves of greatest amplitude were 1 in both sexes in the ear lobe and CV7 for Fz and Cz in men and V for women. Regarding the complex morphological variants, the greatest incidence in the III IV V complex was observed in Fz in both sexes. In CV7 there was a greater range of variants, as found by other workers, but with greater morphological separation of waves IV and V. They were infrequent in waves I II and VI VII and least common in Fz and Cz. CONCLUSION: We consider that the BAEP obtained with reference to Cz and Fz are ideal for interpretation, since there is greater constancy, global amplitude and morphological clarity of the first five deflections and less morphological complexity of the other waves.
Asunto(s)
Electrofisiología/métodos , Potenciales Evocados Auditivos del Tronco Encefálico/fisiología , Adolescente , Adulto , Vértebras Cervicales , Oído/fisiología , Electrodos , Femenino , Humanos , MasculinoRESUMEN
INTRODUCTION: In view of the discrepancy in the placement of electrodes and their effects on the auditory evoked potentials of the brainstem (PEAT), we made a statistical study of these potentials using four different sites for the reference electrode to determine the best position for it. SUBJECTS AND METHODS: The study was done in 30 healthy volunteers aged between 17 and 22 years, 15 men and 15 women. In each person successive measurements were made of the PEAT, with the reference electrode on the vertex (Cz), high frontal (Fz), ear lobe of the opposite side to that of the ear being stimulated and the spinal apophysis of the 7th cervical vertebra (CV). In all cases the active electrode was placed on the ipsilateral ear lobe of the ear being stimulated. After obtaining tables of the normal values for the latency and wave amplitude of waves I to VII in each electrode montage used, we made a study of sex differences and results from the other ear using Student's t test for paired data. RESULTS: No statistically significant differences were found between the latencies and amplitudes of the waves I to VII for the PEAT obtained with the montage used. CONCLUSIONS: From our results, we may conclude that the position of the reference electrode does not seem to be a major factor when obtaining PEAT. However, in view of the recordings made, we prefer the reference electrode to be at Cz or Fz when obtaining PEAT, since a clearer recording is obtained when these positions are used. Influence of the reference electrode on PEAT.
Asunto(s)
Estimulación Eléctrica , Electrodos , Potenciales Evocados Auditivos del Tronco Encefálico , Adolescente , Adulto , Femenino , Humanos , Masculino , Valores de ReferenciaRESUMEN
INTRODUCTION AND OBJECTIVE: In view of the disparity of data and methodology concerning medium (MAEP) and long latency (LAEP) acoustic evoked potentials, we have obtained tables of normal values using a reliable method and statistical study of these potentials in 30 healthy persons, in order to serve as a basis for clinical reference and for possible further studies. MATERIAL AND METHODS: In the MAEP we used the two types of stimuli most commonly employed, first a click and then a rising-plateau-falling tone (2-6-2). We observed that this did not affect the latency or amplitude of the different waves, although the best defined waves are obtained with tones. In the LAEP we always used a tone with rise-plateau-fall of 10-50-10, as recommended by the American Electroneurophysiological Society. In all cases the intensity was of 70 db, with rarefaction and masking of the contralateral ear with an intensity of 50 db. Self-adhesive electrodes were used for captation; the active one was placed on the ipsilateral ear lobe and the reference electrode in Cz for the LAEP. For the LAEP the lower filter was of 1 Hz and the higher of 70 Hz. In view of the variety of filters recommended, 10 Hz at the lower level and 500, 1000 and 2000 at the higher level were used successively for the MAEP. We observed that these did not affect the latency or amplitude of the waves, so these three values may all be used equally well. RESULTS AND CONCLUSIONS: In the inter-sexual study, no differences were seen between men and women. Nor were there significant differences between the acoustic evoked potentials on the right and left sides of the same person.