Effect of Cochlear Implantation on Vestibular Evoked Myogenic Potentials and Wideband Acoustic Immittance.
Gabrielle R Merchant, Kyli M Schulz, Jessie N Patterson and 2 others
PMID 32032225WHAT IT FOUND
In ears with cochlear implants, bone-conducted VEMP responses were more often present than air-conducted responses, especially in eye responses, and low-frequency sound absorbance was reduced in ears with absent air-conducted but present bone-conducted responses.
Key findings
01Bone-conducted VEMP responses were more often present than air-conducted VEMP responses in ears with cochlear implants, and this difference was statistically significant for ocular VEMP but not cervical VEMP.
02Ears with cochlear implants had lower cervical and ocular VEMP amplitudes than normal-hearing ears.
03The largest low-frequency absorbance reductions in implant ears occurred in ears with absent air-conducted but present bone-conducted cervical VEMP responses.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
Only 37 ears were analysed, 27 with cochlear implants and 10 normal-hearing ears, and the authors state the study was likely underpowered. All cochlear implant ears were tested after implantation, with an average of 11.7 years since implantation, so pre-implantation VEMP and absorbance values were not available for within-person comparison. Air-bone gaps could not be quantified in the implant ears because none had measurable bone-conduction thresholds at any frequency on behavioural audiometry. Individual absorbance responses varied widely; some implant ears looked normal-like and some showed increased absorbance rather than stiffening. The study could not adequately analyse etiology, surgical approach, insertion depth, or implant type because of small numbers and unknown etiologies. Dizziness or imbalance was captured only as a yes/no self-report, not as an objective balance outcome. Standard 226 Hz tympanometry did not distinguish the groups, so routine tympanometry may not reveal these mechanical changes.
Declared interests
The work was supported by the National Institutes of Health under award numbers P20GM109023, T35 DC 008757, and R03DC015318.
The easy way to misread this
Do not read an absent air-conducted VEMP in a cochlear implant recipient as proof of vestibular loss. The study found that some ears had absent air-conducted but present bone-conducted VEMPs and reduced low-frequency absorbance, which could reflect mechanical stiffening rather than confirmed vestibular damage.