Automated threshold detection for auditory brainstem responses: comparison with visual estimation in a stem cell transplantation study.

BACKGROUND: Auditory brainstem responses (ABRs) are used to study auditory acuity in animal-based medical research. ABRs are evoked by acoustic stimuli, and consist of an electrical signal resulting from summated activity in the auditory nerve and brainstem nuclei. ABR analysis determines the sound intensity at which a neural response first appears (hearing threshold). Traditionally, threshold has been assessed by visual estimation of a series of ABRs evoked by different sound intensities. Here we develop an automated threshold detection method that eliminates the variability and subjectivity associated with visual estimation. RESULTS: The automated method is a robust computational procedure that detects the sound level at which the peak amplitude of the evoked ABR signal first exceeds four times the standard deviation of the baseline noise. Implementation of the procedure was achieved by evoking ABRs in response to click and tone stimuli, under normal and experimental conditions (adult stem cell transplantation into cochlea). Automated detection revealed that the threshold shift from pre- to post-surgery hearing levels was similar in mice receiving stem cell transplantation or sham injection for click and tone stimuli. Visual estimation by independent observers corroborated these results but revealed variability in ABR threshold shifts and significance levels for stem cell-transplanted and sham-injected animals. CONCLUSION: In summary, the automated detection method avoids the subjectivity of visual analysis and offers a rapid, easily accessible http://axograph.com/source/abr.html approach to measure hearing threshold levels in auditory brainstem response.

Microsurgical access for cell injection into the mammalian cochlea.

The potential use of stem cells to repair hearing loss requires surgical access to the cochlea. Here we describe a microsurgical technique for cell injection into the mouse cochlea. Green fluorescent cells (ZsGreen-MCF10A cells) were successfully injected via a lateral wall cochleostomy into the scala media, scala tympani and scala vestibuli compartments of the cochlea. The effect of surgery on auditory function was investigated with auditory brainstem responses (ABR) to click and tone stimuli. A computerised signal-to-noise ratio detection method was developed to measure ABR thresholds in conjunction with visual inspection. Signal-to-noise ratio detection showed ABR thresholds in control mice were similar for click (33+/-7 dB) and tone stimuli (33+/-6 dB), in agreement with visual inspection (click 39+/-7 dB, tone 35+/-6 dB). The mean ABR threshold for combined click and tone stimuli was 15-45 dB greater after surgery with minimum hearing loss achieved with a small sized cochleostomy (< or =0.4mm) and by sibling matching to control mice (control 33+/-4 dB, surgery 48+/-3 dB). The microsurgical technique will provide a basis for future studies on the use of stem cells in the treatment of hearing loss.

Results of endoscopic resection followed by radiotherapy for primarily diagnosed adenocarcinomas of the paranasal sinuses.

BACKGROUND: Adenocarcinoma is the most frequent histological subtype of paranasal sinus malignancy diagnosed in Belgium. Classical treatment consists of an external surgical approach (lateral rhinotomy with medial maxillectomy or craniofacial resection) followed by radiotherapy. The role, possibilities, and limitations of endoscopic sinus surgery (ESS) are to date unknown. METHODS: We studied 44 patients with primary (not treated previously) adenocarcinoma treated with endoscopic sinus surgery and radiotherapy between 1992 and 2004. RESULTS: The median follow-up of the patients alive at the end of the study period was 36 months. For the 3-year follow-up, the overall survival, disease-specific survival, and local control rate were 81%, 91%, and 73%, respectively. Corresponding rates for the 5-year follow-up were 53%, 83%, and 62%. Union Internationale Contre le Cancer T classification did not appear to influence these results. CONCLUSIONS: Endoscopic sinus surgery followed by radiotherapy for primary adenocarcinoma of the paranasal sinuses gives oncological results comparable to those of standard external approaches.