The Comparion Of Slow Vertex Response Thresholds And Pure Tone Audiometry Thresholds

Objective: To explore characters of slow vertex response(SVR) stimulated by sound at different frequency and intensity, to compare the hearing threshold obtained by SVR and PTA and to discuss the application value of SVR in auditory threshold assessment of forensic medicine.Methods: 46 subjects (92 ears) with normal hearing were tested by PTA and SVR.By making N1waves and P1waves of SVR stimulated by sound at different intensity, three parameters( N1 latency,P2 latency and N1-P2 amplitude)were obtained to explore whether the parameters would change with the intensity decreasing. Paired t- test analysis was performed on the hearing thresholds of these subjects acpuired by SVR and PTA. The SVR-PTA diffference values at each frequency were also obtained. 25 subjects (40 ears) with sensorineural hearing loss were tested both by PTA and SVR. According to the thresholds of PTA, these ears were subdivided to mild, moderate and severe hearing loss groups, and rank sum test was performed on the thresholds of SVR and PTA for all the hearing loss groups. Then,the correlation between PTA thresholds and SVR thresholds was analysised and the mathematical models were established for predicting behavioral thresholds by the thresholds of SVR.Results:â‘ SVR waves were evoked clearly and stablely for 46 subjects with normal hearing. N1 and P2 latencies delayed gradually and N1-P2 amplitude declined with sound stimulus intensity descenting.â‘¡The thresholds of SVR were higher than those thresholds of PTA with a difference value between 5 dB HL and 10 dB HL. Besides, difference between the thresholds acquired with SVR and PTA had a tendency to become largger with frequency increasing, which indicated that SVR thresholds were much closer to PTA thresholds and represented subject's hearing level more accurately at low frequency.â‘¢At four test frequencies, the thresholds of SVR had high correlations with thresholds of PTA,and the correlation coefficient was respectively 0.971,0.976,0.957,0.928 . The liner regression equations had been established for predicting behavioral thresholds(Y=-3.582+1.020x at 0.5kHz;Y=-3.869+1.013x at 1 kHz;Y=-6.108+1.011x at 2kHz;Y=-5.671+1.022x at 4kHz). After back substitution test was analysised,we could conclude that the liner regression equation would be a easy method for estimating the behavior thresholds.Conclusions:â‘ In suitable conditions, SVR was a stable technology for hearing thresholds prediction, and the changing regularity of the parameters of SVR with sound stimulus intensity decreasing played an important part in auditory thresholds accessment.â‘¡The adjusted thresholds should be established at each frequency, when the thresholds of SVR would be used to predict the behavioral threshold for subjects with normal hearing.â‘¢The behavioral threshold can be well judged and evaluated by the liner regression equations established with SVR thresholds.