Diagnostic Potential of Distortion Product Otoacoustic Emissions in Noninvasive Assessment of Elevated Intracranial Pressure: Different Patterns of DPOAE Alterations in the Guinea Pig

Table 2

Mean and range of ICP-induced DPOAE level changes (ΔDP), range of the standard deviation during elevated ICP (SD_ICP), and number of valid intervals for different frequencies 𝑓₂. Mean_ΔDP, range_ΔDP, and  range_SDICP  are given in dB SPL. See Section 2.3 for calculations and inclusion criteria. Significant changes are indicated by an asterisk.

(a) First pattern of DPOAE level alterations attributed to altered sound transmission. Note that there is a significant DPOAE level decrease only at 𝑓₂ = 2 kHz

	𝑓2 = 2 kHz	𝑓2 = 4 kHz	𝑓2 = 8 kHz	𝑓2 = 12 kHz	𝑓2 = 16 kHz
MeanΔDP	−3.17*	−0.69	−0.13	+0.20	−0.53
RangeΔDP	−8.05–+1.13	−4.42–+1.43	−1.26–+1.28	−0.63–+2.51	−1.55–+0.61
RangeSDICP	0.83–1.66	0.35–2.06	0.34–0.74	0.36–1.33	0.21–1.13
Number of valid intervals	10	12	14	14	13

(b) Second pattern of DPOAE level alterations that might be attributed to reduced CoBF. Note the pronounced DPOAE level decrease at all measured frequencies and the much larger SD_ICP

	𝑓2 = 2 kHz	𝑓2 = 4 kHz	𝑓2 = 8 kHz	𝑓2 = 12 kHz	𝑓2 = 16 kHz
MeanΔDP	−2.80	−7.66	−9.76	−11.47	−12.36
RangeΔDP	−1.53–−3.98	−1.97–−13.46	−3.67–−14.25	−5.25–−22.18	−4.44–−21.36
RangeSDICP	3.83–7.36	3.74–12.84	3.00–10.24	7.27–17.51	5.25–13.56
Number of valid intervals	4	5	5	5	5