Hearing threshold assessment post grommet insertion. Is it reliable?

Abstract

We aimed to investigate whether auditory brainstem response (ABR), assessed immediately after grommet insertion, was an accurate measure of hearing threshold. Ten children were recruited (20 ears). Patients underwent transient evoked otoacoustic emission (TEOAE) and ABR tests before and after grommet insertion under general anaesthetic. A third assessment was conducted at a six-week review, without anaesthetic or sedation. The hearing threshold in dB and the presence of TEOAE were recorded by senior audiologists. The results of each investigation were compared. At review, only 15 ABR and 17 TEOAE tests, of a possible 20, were recorded. Transient evoked otoacoustic emissions were recorded in 30 per cent of ears pre-operatively, 20 per cent of ears post-operatively and 82 per cent of ears at six-week review. The average ABR thresholds were 23.75 dB (range 10-45 dB) pre-operatively, 27.25 (range 15-40 dB) post-operatively and 15 dB (range 5-25 dB) at six-week review. Comparing pre- and post-operative assessment, decreased thresholds were seen in six ears and elevated thresholds in 11. Comparing the six-week review ABR with the post-operative ABR, 13 ears had decreased thresholds, by as much as 20 dB. Thresholds of 35 dB or greater were measured in six ears immediately after grommet insertion (maximum 40 dB). Threshold shifts of 15 dB or greater was observed in seven ears. The intra-subject variation was shown to be significant (p<0.001) when repeated measures analysis of variance was applied. We conclude that there is evidence that ABR can be inaccurate after grommet insertion, overestimating hearing thresholds. We believe that the mechanism by which the error is realised is temporary threshold shift.

Pediatric hearing assessment by auditory brainstem response in the operating room

“…Early studies reported improved hearing immediately after tube placement by ABR testing and justified the use of ABR testing in the OR [10,11]. Clinical studies in recent years have revealed significant discrepancies between ABR results obtained in the OR and those obtained in the follow-up period, raising a concern regarding the validity of ABR outcomes obtained in the OR [7][8][9]. It is argued that OR-ABR results may not reflect patients' real hearing thresholds, therefore, follow-up audiological evaluations should be performed when OR-ABR indicates a hearing loss.…”

“…They suggested that ABR thresholds following aspiration of middle ear fluid should be interpreted with caution. In 2007, Griffiths et al investigated whether the ABR, assessed immediately after tube insertion, was an accurate measure of hearing threshold [8]. Among the 10 subjects (20 ears) studied, threshold shifts of 15 dB or greater were observed in 7 ears after tube insertion.…”

The Role of Intraoperative Auditory Brainstem Response Testing for Infants and Difficult‐To‐Test Children

“…They recommended that follow-up testing should not be done until two to three weeks after fluid removal to better ensure resolution of middle ear disease. 6 Griffiths et al 7 prospectively performed transient evoked otoacoustic emissions and ABRs in 10 children immediately before, immediately after, and six weeks following tube insertion. Comparing the six-week review ABR with the postoperative ABR, 13 ears had decreased thresholds, by as much as 20 dB.…”

“…Griffiths et al7 prospectively performed transient evoked otoacoustic emissions and ABRs in 10 children immediately before, immediately after, and six weeks following tube insertion. Comparing the six‐week review ABR with the postoperative ABR, 13 ears had decreased thresholds, by as much as 20 dB.…”