Effect of Tympanostomy Tube Placement on Intraoperative Auditory Brainstem Response

Background Intraoperative auditory brainstem response (ioABR) testing under general anesthesia is commonly performed on children when sleep-deprived ABR and behavioral testing are not reliable or feasible. Several studies have reported potential confounding results when tube insertion is combined with ABR testing. Purpose This article evaluates whether a temporary threshold shift (TTS) occurs following placement of tympanostomy tubes (TTs) in children who undergo ioABR testing. Research Design A case-control prospective study. Patients scheduled for combined TT and ioABR procedures were enrolled into this study. Study Sample Twenty children (38 ears), ranging in age from 6 months to 10.5 years, were enrolled. Data Collection and Analysis ABR thresholds for tone bursts with center frequencies of 2 and 4kHz were compared before and after tube insertion. The indication for surgery, comorbidities, and status of the middle ear were also recorded. A paired t -test was used to determine statistical significance. Results Data collection did not necessarily indicate suctioning and tube placement were causing a TTS; however, fluid present in the middle ear space prior to TT placement appeared to influence results. Although a paired t -test did not show statistically significant differences in ABR thresholds between groups of individuals with and without fluid and before and after tube placement, 50% of patients with mucoid fluid (two out of four patients) were noted to have 10dB or greater worsening in ABR thresholds in two out of six ears. Twenty-nine percent of patients with serous fluid (two out of seven patients) were noted to have at least a 10dB worsening in ABR threshold in 2 out of 10 ears. Further testing is needed to confirm these trends. Conclusion This pilot study indicates that children with mucoid or serous fluid may experience worse ABR thresholds following TT insertion. ioABR testing immediately after TT tube placement and in the presence of middle ear fluid should be interpreted with caution. Additional studies with a larger sample size are needed to confirm these results.