The effects of monoaural and binaural stimulation on middle latency auditory evoked responses
*Correspondencia: Dra. Margarita Minou Báez Martín. Laboratorio de Neurofisiología Clínica. Centro Internacional de Restauración Neuroló- gica, CIREN. Ave. 25, # 15.805, e/ 158 y 160. Cubanacán, Playa. CP 12100 Ciudad de la Habana, Cuba.
Fax: (537) 332420, 336020, 336339.
E-mail: cineuro@neuro.sld.cu, minou@neubas.sld.cu
Introduction. Middle latency evoked potentials include a series of evoked responses which encompass/include myogenic potentials (which translate the existence of sonomotor reflexes), and others which are clearly of neurogenic origin. The latter are the most useful from the clinical point of view. Objective. To evaluate the effects of monoaural (MA) and binaural (BA) stimulation on middle latency auditory evoked potentials. Patients and methods. We studied 15 healthy people, aged between 18 and 52 years, in whom Cz recording electrodes had been fitted to both short-circuited external ears with Fpz as earth. The stimuli used were alternate clicks of condensation and rarefication of 90 dBHL, first BA and them MA. The auditory evoked response from the brain stem was also recorded. Results. We found more stability of most of the components evaluated during biauricular stimulation. All subjects had Pa waves and 93% had Pb waves. Statisti- cally significant differences were only found for the amplitude of Po and Pa (BA against RE) (Wilcoxon test, p< 0.05). Conclusion. The use of BA stimulation to obtain middle latency evoked potentials is more useful for study of the more rostral parts of the auditory path, since its components are more stable.
Objetivo Evaluar los efectos de la estimulación monoaural (MA) y binaural (BA) sobre el potencial evocado auditivo de latencia media.
Pacientes y métodos Estudiamos 15 sujetos sanos, con edades comprendidas entre 18 y 52 años, a los cuales se colocaron electrodos de registro en Cz, referidos a ambas orejas cortocircuitadas y Fpz como tierra. Los estímulos aplicados fueron clics alternos de condensación y rarefacción de 90 dBHL, primero BA y luego MA. Se registró además la respuesta evocada auditiva de tallo cerebral.
Resultados Constatamos una mejor estabilidad de la mayor parte de los componentes evaluados durante la estimulación biauricular. El 100% de los sujetos presentaron onda Pa y el 93% onda Pb, y detectamos diferencias estadísticamente significativas sólo para la amplitud de Po y Pa (BA frente a OD) (test de Wilcoxon, p< 0,05).
Conclusión El empleo de la estimulación BA para la obtención del potencial evocado auditivo de latencia media resultó de mayor utilidad para el estudio de las porciones más rostrales de la vía auditiva, dada la mayor estabilidad de sus componentes.
