How reliable is visual assessment of the electrically elicited stapedius reflex threshold during cochlear implant surgery, compared with tympanometry?
OBJECTIVE
To assess the reliability of visually assessed thresholds of the electrically elicited stapedius reflex, recorded during cochlear implant surgery, compared with intra-operative tympanometric threshold assessment. Intra-operatively recorded electrically elicited stapedius reflex thresholds vary considerably, and differ from those measured post-operatively by means of impedance changes (i.e. using tympanometry). Thus, any confounding effect of different intra-operative techniques and visual assessment inaccuracies should be excluded.


METHODS
Both techniques (i.e. visual observation and tympanometry) were performed intra-operatively in six patients, and threshold values were compared.


RESULTS
Recorded electrically elicited stapedius reflex thresholds were very similar for both techniques. Visually assessed thresholds were slightly higher in some cases and lower in others, compared with tympanometric thresholds.


CONCLUSIONS
There was almost no difference between reflex thresholds measured with the two different techniques under the same intra-operative conditions. Therefore, we conclude that differences between intra- and post-operative thresholds are not due to the use of different measuring techniques. The main reason for such differences is probably the influence of intra-operative narcotics on reflex thresholds.
Department of Otorhinolaryngology, Head and Neck Surgery, University of Rostock, Rostock, Germany. hans-wilhelm.pau@med.uni-rostock.de
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Pau
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Ehrt
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Just
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Sievert
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Dahl
D000158:Acoustic Impedance Tests / Q000379:methods; D002648:Child; D019929:Cochlear Implantation / Q000379:methods; D004558:Electric Stimulation; D004566:Electrodes; D006801:Humans; D016343:Monitoring, Intraoperative / Q000379:methods*; D012022:Reflex, Acoustic / Q000502:physiology*; D015203:Reproducibility of Results; D012684:Sensory Thresholds / Q000502:physiology; D013198:Stapedius / Q000502:physiology*