Alterations of vestibular function in cochlear implantation

I am excited to report that this recently completed research topic has now been published as an e-book. Alterations of vestibular function in cochlear implantation is available for free download on the Frontiers of Neurology website. Up till today, the papers have received 17 276 views.

Alterations of Vestibular Function in Cochlear Implantation

Cochlear implantation has established itself as a cost-effective intervention for many patients with hearing loss. Electrode design has evolved in an attempt to preserve the fine structures of the cochlea, with many contributions in the literature on this topic. Unfortunately, the same cannot be said for the alterations that occur and those factors influencing vestibular function. More research is needed to address these issues, and this project was such an attempt.

This Research Topic aimed to investigate how the vestibular function is altered in cochlear implantation. The aim was to invite any scientific contribution where the vestibular function is investigated in cochlear implantation.

I would like to acknowledge my two co-editors, Ingo Todt and Anandhan Dhanasingh, for collaborating with me in selecting articles and managing the peer-review process. In the end, 13 papers were selected for publication. We are extremely great full for the interest and participation in this project. We received excellent contributions from renowned scientists all over the world.

Louis Hofmeyr
Ingo Todt
Ingo Todt
Anandhan Dhanasingh
Anandhan Dhanasingh

Frontiers is a leading Open Access Publisher and Open Science Platform. The journals are led and peer-reviewed by editorial boards of over 100,000 top researchers. It covers more than 900 academic disciplines and is of the largest and highest-cited publishers in the world. Their freely accessible research articles have received over 1 billion views and downloads and 1.6 million citations.

Alterations of vestibular function in cochlear implantation were published in the section, Frontiers of Neuro-otology under the guidance of Speciality editor, Prof Dr Michael Strupp. Frontiers of Neuro-otology resorts under the Journal Frontiers of Neurology. It had an impressive impact factor of 4.0 in 2020. In essence, this means that the journal articles in Neurology were cited an average of 4 times in other publications and works. Frontiers is the third most cited source in the world, demonstrating its impact and recognition.

A summary of some of the findings include:

  • a reduced risk of damage to vestibular function using the round window approach in CI surgery with flexible lateral wall electrode arrays in contrast to promontory drilling of a bony cochleostomy and using pre-curved electrode array types. This was also true in paediatric patients.
  • using the extended round window approach of electrode array insertion could affect the vestibular function negatively as evaluated by cVEMP (cervical vestibular evoked myogenic potential). cVEMP is used to assess the patient’s balance function by assessing their saccular function.
  • children with enlarged vestibular aqueduct (EVA) are more likely to have preserved saccular and utricular functions after CI surgery than children with “normal” ear anatomy due to minor pressure-related damage to those structures resulting from the EVA. It is generally assumed that the length of the electrode array that is inserted inside the cochlea could also affect the vestibular function
  • the reduced probability of vertigo when using flexible electrodes may not be clearly observed nor of the negative influence of the electrode insertion length
  • vestibular dysfunction reaches a plateau 4-months post-operatively after which there is no further deterioration or improvement in vestibular function. The long-term effect of the biological stressors on the degradation of vestibular function is still to be understood.
  • no difference in vestibular dysfunction in unilateral and sequentially implanted bilateral subjects following CI could be found. The video head impulse test (v-HIT) is a quick, non-invasive, and relatively cheap test to evaluate vestibular function compared to the caloric test. The other key reason to consider using v-HIT is its ability to test in the high-frequency range, which effectively looks at the body and gaze stabilisation.
  • the effectiveness of using v-HIT to select CI candidates that require caloric testing before cochlear implantation is of value. Also, looking at the saccades in addition to the gain values.
  • vestibular implants (VI) are currently under research to understand the safety and effectiveness of VI in restoring the vestibular function in patients with conditions like bilateral vestibulopathy and Meniere’s disease
  • electrically evoked cVEMPs can be present after cochlear and vestibular stimulation. By measuring the cVEMP following the direct electrical stimulation of the vestibular portion with VI, may stimulate the vestibular elements safely.
  • hearing preservation techniques in cochlear implantation are connected with vestibular protection, but the risk of vestibular damage is never eliminated completely. Quality of life (QoL) in older adults with a history of loss of balance and in patients with a history of Menière’s disease after cochlear implantation is an exciting topic.
  • there is a risk of falling in older adults after CI is high, and proper testing methodology to assess their vestibular function before and after the CI surgery is stressed. This may be streamlined for developing countries.
  • the hearing results and QoL benefits perceived by CI candidates with Menière’s disease is similar to regular CI candidates. Patients who undergo simultaneous CI and labyrinthectomy may experience worse QoL, luckily short-lasting.
  • a nicely photographed study of the vestibular space and the nerves associated with the vestibular organ using micro-computer tomography (μCT) and high radiation synchrotron phase-contrast images. The effects of surgical trauma are nicely explained.

As stated by Anandan Dhanasingh, testing the vestibular function periodically for many years following CI surgeries would help the CI community to learn more about the effect of CI surgery and other factors on the alteration of vestibular function. As editors of all these articles, we would like to encourage the readers to take their time to read these articles and to update their knowledge