Study On Auditory Steady-state Response

Brain injury,especially brain stem injury has a high mortality and morbidity.In clinical practice,the objective means to assess the degree of brain injury in coma patients,such as whether the brain has died,whether there is rescue value,whether it can wake up,etc.,has important guiding significance for follow-up treatment.In recent years,auditory steady-state response(ASSR)has been regarded as a convenient and valid electrophysiological technique,which can be used in hearing tests,anesthesia monitoring,neurological assessment and other clinical aspects.Evoked by an auditory stimulus such as the amplitude modulation tone,ASSR behaves like a periodic electrical activity whose frequency is determined by the stimulation modulation rate.In this thesis,taking ASSR as a research object,an ASSR acquisition and detection system was proposed,and the existing results of ASSR were summarized from the perspective of meta-analysis.Based on the above analysis,ASSR was proposed as an objective evaluation index for the prognosis of clinical coma patients,and the corresponding prognosis evaluation model was established.Firstly,the ASSR experimental system was set up,by designing four groups of experiments,with a total of twelve paradigms.ASSR experiments were performed on twenty-six normal hearing adults who met the inclusion criteria.The electroencephalograph(EEG)data of normal subjects were processed and summarized to explore the basic factors influencing of the ASSR response.As the previous ASSR experimental study focused on the data collection rather than the detection of the signal,in this study,based on the theory of signal detection,the ASSR detection problem was modeled as detecting a sinusoidal signal from noise without the knowledge of amplitude and phase,and a quadrature matched filter method was employed.The recorded ASSR data were used to verify the efficiency of the proposed method.The results showed that the proposed method had high accuracy and reliability.Secondly,in this thesis the meta-analysis method was used to synthesize the results of the existing ASSR research literatures.ASSR has been mainly used as a means of hearing test,and there is no consistent conclusion for the threshold difference and correlation between the thresholds measured by ASSR and those by conventional behavior hearing test,i.e.pure tone audibility test.In this context,the mean threshold difference and Pearson correlation coefficient between the ASSR threshold and the PTA threshold in patients with hearing loss were merged,to explore the reliability of ASSR as an objective audiometry for patients with hearing loss.The results showed that the ASSR threshold and the PTA threshold had a high correlation,and the average difference between the two was small,which implied that ASSR can be used as an objective listening evaluation tool.Lastly,the proposed ASSR EEG acquisition and detection system was used to evaluate the prognosis of coma patients,as the advantages of ASSR such as its extensive intracranial origin,high frequency-specificity,and the close relation between auditory pathway and brainstem function.Thirty-two patients who met the inclusion criteria received the ASSR experiments,combined with the patients’ clinical data.The arousing of ASSR was analyzed combined with prognosis results,to evaluate the predictive accuracy of ASSR for the prognosis of coma patients.According to the predicted probabilistic results of three different logistic regression models,it was showed that 40 Hz and 80 Hz ASSR can be used as indicators of poor prognosis,with high prediction accuracy.