ABSTRACT
Introduction: In a previous manuscript from our research group, the concept of vestibular co-stimulation was investigated in adult subjects who received a cochlear implant (CI). Despite what literature reports state, no signs of vestibular co-stimulation could be observed. Results: In this case report, it was described how a woman, who previously underwent a neurectomy of the left vestibular nerve and suffers from bilateral vestibulopathy (BVP), reported improved balance whenever her CI on the left was stimulating. Unexpectedly, the sway analyses during posturography indeed showed a clinically relevant improvement when the CI was activated. Discussion: Vestibular co-stimulation as a side effect of CI stimulation could not be the explanation in this case due to the ipsilateral vestibular neurectomy. It is more likely that the results can be attributed to the electrically restored auditory input, which serves as an external reference for maintaining balance and spatial orientation. In addition, this patient experienced disturbing tinnitus whenever her CI was deactivated. It is thus plausible that the tinnitus increased her cognitive load, which was already increased because of the BVP, leading to an increased imbalance in the absence of CI stimulation.
ABSTRACT
OBJECTIVE: The objective is to evaluate the influence of the presentation rate on intraoperative ECAP thresholds in cochlear implant users. DESIGN: The design was data on the ECAP thresholds (t-NRT) as well as the behavioural T- and C-levels have been collected in CI patients of a quaternary otologic referral centre. Measurements of the tNRT thresholds were performed intraoperatively for 250 Hz and 80 Hz presentation rates and correlated to the stabilised T- and C-levels measured at the 5th fitting session, 4-6 months after surgery. STUDY SAMPLE: There was a study sample of 35 consecutive CI patients. All patients were users of the Nucleus 24RECA (Freedom) or Nucleus CI512 cochlear implants with the Contour Advance-of-Stylet electrode. RESULTS: The result showed that the t-NRT thresholds were higher for the 250 Hz pulse rate typically used during the intraoperative stimulation under general anaesthesia than for the 80 Hz rate used typically during the postoperative fitting sessions. This difference was more pronounced for the basal electrodes where it exceeded 10 current levels (CL). Pearson's correlation coefficients between the t-NRT-measurements and the stabilised T- and C-levels r ranged between 0.34 and 0.47. CONCLUSION: In conclusion, the magnitude of the ECAP thresholds (t-NRT) recorded intraoperatively depends significantly on the stimulus presentation rate.
Subject(s)
Cochlear Implants , Evoked Potentials, Auditory , Monitoring, Intraoperative/methods , Adult , Child , Child, Preschool , Humans , Infant , Middle AgedABSTRACT
OBJECTIVE: To evaluate the postoperative changes of the basic electrophysiological and psychophysical parameters in cochlear implant (CI) patients: the impedance of the electrode contacts, the electrically-evoked compound action potential (ECAP) thresholds and the T/C levels. STUDY DESIGN AND SETTING: Retrospective case review in a quaternary otologic referral centre. MATERIALS AND METHODS: Data on the impedance of the electrode contacts, the ECAP thresholds and the T/C levels were collected in 20 consecutive CI patients divided into 2 groups. Group 1 comprised 10 prelingually deaf children implanted before the age of 18 months, and group 2 comprised 10 postlingually deaf adults (average age of 58 years). All patients were users of the Nucleus 24RECA (Freedom, Contour advance off-stylet electrode) CI. RESULTS AND CONCLUSIONS: (1) The mid-portion and the apical electrodes showed a decrease in the impedance values between the 1st and the 6th postoperative months and stabilization in the later course. Impedance of the most basal electrodes grew during the first postoperative months and stabilized later on, but remained higher than the impedance of the mid-portion and the apical electrodes. (2) The neural response telemetry threshold values tended to decrease within the first 3 months after surgery to reach a plateau afterwards. (3) The behavioural threshold levels remained generally stable, except for the basal electrodes where a decrease could be observed. The hearing comfort levels showed an increase during the first 6 months of the implant use and remained stable afterwards.
