Auditory Evoked Response Test Strategies to Reduce Cost and Increase Efficiency: The Postauricular Muscle Response Revisited

Abstract

We describe a number of techniques in auditory evoked response (AER) testing for hearing loss which should decrease its cost and increase its efficiency, making its use in infant hearing screening more viable. We demonstrate the use of bit-stream averaging of the electrical signals from the head as a cheap alternative to analogue averaging and show that the average waveforms obtained are similar with both techniques. We demonstrate how the postauricular muscle response (PAMR) can be potentiated by lateral rotation of the eyes and argue that uncontrolled eye movements in previous studies have led to an unfounded belief that the PAMR is not stable. When eye rotation is used to potentiate the PAMR, the response becomes very stable and so large in most subjects that it is clearly visible in the raw traces. We also demonstrate that when the PAMR is potentiated by eye rotation, stable PAMR waveforms can be reliably obtained with tone bursts with frequencies up to and above 8 kHz and with sound levels within 30 dB of the subjective detection threshold. As a result the PAMR can be used to rapidly determine an objective audiogram in most subjects within minutes. Finally, we demonstrate a correlation technique for detecting the PAMR without waveform averaging and the need for an expensive computer. We are sure that a combination of these techniques can be used to increase the efficiency of AER screening for infant deafness and lower its cost dramatically.

The post-auricular muscle response: an objective electrophysiological method for evaluating hearing sensitivity

“…As reported previously by Patuzzi and O'Beirne (1999b) and Patuzzi and Thomson (2000), there was a significant increase in the PAMR amplitude and the number of subjects with a PAMR for monaural and binaural stimulation when subjects turned their eyes towards the recording electrodes compared to eyes front. This enhanced PAMR with eye turn is most likely due to increased muscle tone.…”

“…Consistent with previous studies (Yoshie & Okudaira, 1969;Gibson, 1974;Thornton, 1975;O'Beirne & Patuzzi, 1999;Patuzzi & Thomson, 2000), decreasing stimulus level produced later PAMR latencies and smaller PAMR amplitudes. However, even at low intensities, the PAMR was considerably larger than typical ABR responses for those subjects that had responses at these levels.…”

“…The fact that it has not been used for this purpose in the last twenty years is largely due to its perceived variability within and between subjects (Patuzzi & Thomson, 2000). This variability appears to result from factors such as muscle tone, head and eye position, subject state, and recording filter pass band.…”

“…PAMR is reduced when subjects are more relaxed (Gibson, 1974;Humphries et al, 1976) or asleep (Davis, 1976;Streletz et al, 1977). PAMR amplitude is increased by neck traction (Cody & Bickford, 1969), head lowering (Yoshie & Okudaira, 1969;Dus & Wilson, 1975), teeth gritting (Dus & Wilson, 1975;Gibson, 1978), propping the head forward (Yoshie & Okudaira, 1969;Thornton, 1975), pushing the head against a force (Clifford-Jones et al, 1979), or lateral eye movement (Patuzzi & O'Beirne, 1999b;Patuzzi & Thomson, 2000).…”

“…In contrast, Clifford-Jones et al (1979) found that PAMR was absent in only 2% of subjects. Recently, Patuzzi and colleagues found that PAMR can be reliably recorded in most adults when recording and stimulus parameters are optimal (O'Beirne & Patuzzi, 1999;Patuzzi & O'Beirne, 1999a,b;Patuzzi & Thomson, 2000).…”