BACKGROUND AND OBJECTIVES: Cochlear dead region (CDR) is a region in the cochlear where hearing loss has occurred due to damage to the inner hair cells and/or neurons. Recently, a subjective test involving a pure-tone test in the presence of threshold-equalizing noise (TEN) was introduced to identify CDR. However, for uncooperative patients, such a subjective method would be unsuitable and objective methods would be needed instead to detect CDR. The acoustic change complex (ACC) is an evoked potential elicited by changes in the ongoing sound. In this study, we developed an objective method of identifying CDR by combining ACC response with a TEN test, namely the TEN-ACC test, and investigated its feasibility in normal-hearing listeners. SUBJECTS AND METHOD: Ten normal-hearing subjects participated in this study. All subjects underwent both behavioral TEN test and electrophysiological TEN-ACC test. The stimuli for the TEN-ACC test consisted of TEN and embedded pure tones with different frequencies/signals to noise ratios (SNRs). To identify the thresholds, the range SNR of stimulation was varied from 0 to 20 dB, in stages of 4 dB. RESULTS: The ACC responses of all subjects who participated in this study were well elicited by stimuli developed for the TEN-ACC test. We confirm that the pure-tones embedded in TEN elicited the objective ACC response. CONCLUSION: The results of this study suggest that the novel TEN-ACC test can be applied to evoke ACC in normal-hearing listeners. Future research should incorporate hearing-impaired listeners to determine the feasibility of the TEN-ACC test as an objective method to identify CDR.
Acoustics* ; Evoked Potentials ; Hair Cells, Auditory, Inner ; Hearing Loss ; Humans ; Methods ; Neurons ; Noise

PURPOSE: Total thyroidectomy with central lymph node dissection (CLND) is a treatment modality of choice for thyroid cancer. Hypocalcemia is the most common complication after total thyroidectomy. The aim of the current study was to determine the association between surgery-related clinical factors and postoperative hypocalcemia. METHODS: A prospective analysis was performed for 101 patients who underwent total thyroidectomy with CLND for papillary cancer from June 2013 to June 2014. Correlation between clinicopathologic factors and postoperative hypocalcemia was analyzed. RESULTS: Based on the postoperative day-2 calcium, 56 patients (55%) developed hypocalcemia and 45 patients (45%) were normal. No significant differences in histopathologic (tumor size, tumor focality, histologic type, number of retrieved lymph nodes, metastatic lymph node, thyroiditis, retrieved parathyroid gland) findings were observed between the hypocalcemia group and normal calcium group. Mean value of the postoperative day-0 parathyroid hormone (PTH) was significantly lower in the hypocalcemia group (hypoca1cemia group: 14.3+/-9.4 pg/mL; normal group: 25.0+/-16.4 pg/mL; P<0.001). In logistic regression analysis, postoperative PTH was a factor significantly affecting postoperative hypocalcemia (OR 0.93; CI: 0.90-0.97; P<0.001). In ROC analysis, the cut-off value of PTH was 19.965 (sensitivity 79%, specificity 58%), and area under the curve (AUC) was 0.709 (95% CI: 0.607-0.811). CONCLUSION: Postoperative PTH was a factor predicting hypocalcemia after total thyroidectomy with CLND. Use of postoperative PTH as a screening tool for prediction of postoperative hypocalcemia would be useful in management of patients with hypocalcemia.
Calcium ; Humans ; Hypocalcemia* ; Logistic Models ; Lymph Node Excision* ; Lymph Nodes* ; Mass Screening ; Parathyroid Hormone ; Prospective Studies ; ROC Curve ; Sensitivity and Specificity ; Thyroid Gland* ; Thyroid Neoplasms* ; Thyroidectomy* ; Thyroiditis