MIDDLE LATENCY AUDITORY-EVOKED POTENTIALS - INTERINDIVIDUAL VARIABILITY

Middle latency auditory evoked potentials were studied in 40 adults (mean age 24.9+/-2.9 years; range: 19-34 years; 14 females, 26 males) with normal hearing. Latencies of wave V (early AEP), NO, PO, Na and Pa after monaural and binaural stimulation showed results with relative small standard deviations. However, the amplitudes (NO-PO, PO-Na, Na-Pa) and the amplitude ratio (PO-Na)/(Na-Pa) demonstrated clearly greater interindividual ranges and were more useful for intraindividual control measurements. In both, females and males, right-sided monaural stimulation and ipsilateral recording produced shorter average latencies and higher amplitudes than left-sided stimulus presentation (e.g. Pa-right: 28.26+/-3.53 ms; Pa-left: 30.17+/-3.33 ms; n=40). The middle latency auditory evoked potentials showed significant differences according to sex. These might be due to the smaller head circumference of the women. This should be considered when calculating normal values. Differences according to sex were more pronounced for the components V, NO, PO and Na than for the wave Pa. A classification of the middle latency auditory evoked potentials with and without myogen reflex responses showed no significant differences of latencies.