## 3 Results
### Physiologic Measures  
#### 3.1.1 Distortion Product Otoacoustic Emissions  
Twelve of fourteen included studies used DPOAEs as a physiologic outcome measure. At a minimum, these studies analyzed DPOAEs at frequencies between 1000 to 3000 Hz before and after treatment. Combined, five of the fourteen articles assessed DPOAE measures at octave and inter-octave frequencies from 500 to 12,000 Hz; the remaining six articles evaluated DPOAE between 500 and 6000 Hz (see Table 3). When reported, changes in DPOAE amplitudes were inversely related to increased pure tone thresholds [16; 17; 18; 21]. More specifically, a hearing threshold increase of 20 dB corresponded with a 10 dB decrease in the DPOAE level, which agrees with other literature [18; 21; 26]. Larger DPOAE amplitudes within the first three days of ISSNHL onset were also shown to be a significant prognostic indicator for faster hearing improvement [16; 17]. A better hearing prognosis was noted for those with a larger DPOAE emission shortly following acute damage, even with considerably elevated hearing thresholds [32]. [PERSON] and colleagues [28] reported that patients with detectable DPOAEs at the initial follow-up evaluation had a significantly higher average hearing improvement in comparison with patients with no measurable DPOAE response at first evaluation; the sensitivity and specificity of DPOAE ability to predict hearing improvement on the seventh day of follow up reached 83% and 100%, respectively [35]. [PERSON] and colleagues found that three patients with intact DPOAEs upon presentation had an average improvement of 33 dB in their PTA at 500-2000 Hz in conjunction with steroid therapy, but, in contrast, five of seven patients with absent DPOAEs upon presentation had no improvement in hearing despite steroid therapy [35]. [PERSON] and colleagues reported that changes in DPOAEs and \begin{table}
\begin{tabular}{c c c} \hline \hline
**Article** &
\begin{tabular}{c} **Monitoring** \\ **Measurements** \\ \end{tabular} & **Monitoring Schedule** \\ \hline [PERSON] et al. (2018) [36] & DPOAEs 500–12,000 Hz & Before treatment and 15 th day of treatment \\ \hline \multirow{3}{*}{[PERSON] \& [PERSON] (2005) [24]} & DPOAEs 1000–3000 Hz & \\  & TEOAEs 500–5000 Hz & \\  & SOAEs (present/absent) & \\  & PTA & \\ \hline \multirow{3}{*}{[PERSON] \& [PERSON] (2006) [25]} & DPOAEs 1093–5500 Hz & Every day for maximum of 7 days during \\  & PTA & hospital admission; every other week or \\  & ASR & monthly following discharge \\  & VEMP & \\ \hline \multirow{3}{*}{[PERSON] \& [PERSON] (2010) [26]} & DPOAEs 1093–5500 Hz & Every day for maximum of 7 days during \\  & PTA & hospital admission; every other week or \\  & ABR & monthly following discharge \\ \hline \multirow{3}{*}{[PERSON] (2005) [27]} & DPOAEs 1000–4000 Hz & 3–9 examinations (average) performed \\  & TEOAEs 1000–4000 Hz & following symptom onset in intervals between \\  & PTA & 3 and 505 days (average of 53 days) \\ \hline \multirow{3}{*}{[PERSON] et al. (2008) [28]} & DPOAEs 1000–6000 Hz & \multirow{3}{*}{Day of hospital admission and on a weekly \\  & PTA & basis until hearing stabilized \\  & Tinnitus/Ear Fullness & \\ \hline \multirow{2}{*}{[PERSON], et al. (2001) [29]} & TEOAEs 500–5600 Hz & On admission, at least 2\(\times\) during admission, \\  & PTA & 8–10 days after admission \\ \hline \multirow{3}{*}{[PERSON] et al. (2011) [30]} & DPOAEs 593–6031 Hz & \multirow{3}{*}{First hospital visit \& one month post treatment} \\  & PTA & \\ \hline \multirow{3}{*}{[PERSON], et al. (1997) [4]} & DPOAEs 708–6299 Hz & \multirow{3}{*}{Every 2–7 days during course of treatment} \\  & TEOAEs 1000–1500 Hz & \\  & SOAEs 1000–6000 Hz & \\  & PTA & \\ \hline \end{tabular}
\end{table} 
Table 3: Monitoring procedures used by included studies. SOAE, spontaneous otoacoustic emissions. hearing were associated with one another when the PTA was greater than 55 dB HL, however, the two were not correlated for patients with a PTA of less than 55 dB HL [34].