Abstract
Objective: To assess, for the first time in a human with a long-term vestibular loss, a modified approach to the ampullae and the feasibility of evoking a VOR by ampullar stimulation. Materials and methods: Peroperative stimulation of the ampullae, using the ampullar approach, was performed under full anesthesia during cochlear implantation in a 21-year-old female patient, who had experienced bilateral vestibular areflexia and sensorineural hearing loss for almost 20 years. Results: The modified ampullar approach was performed successfully with as minimally invasive surgery as possible. Ampullar stimulation evoked eye movements containing vectors congruent with the stimulated canal. As expected, the preliminary electrophysiological data were influenced by the general anesthesia, which resulted in current spread and reduced maximum amplitudes of eye movement. Nevertheless, they confirm the feasibility of ampullar stimulation. Conclusion: The modified ampullar approach provides safe access to the ampullae using as minimally invasive surgery as possible. For the first time in a human with long-term bilateral vestibular areflexia, it is shown that the VOR can be evoked by ampullar stimulation, even when there has been no vestibular function for almost 20 years. This approach should be considered in vestibular surgery, as it provides safe access to one of the most favorable stimulus locations for development of a vestibular implant.
Highlights
This study shows, for the first time in a human with a long-term vestibular loss, the modified ampullar approach with minimally invasive surgery and the feasibility of ampullar stimulation
There is an important difference between this human subject and subjects in previous research: previous subjects still had some residual function, or bilateral vestibulopathy was induced by canal plugging or ototoxic medication prior to implantation (Gong and Merfeld, 2002; Lewis et al, 2002, 2010; Wall et al, 2002; Merfeld et al, 2006, 2007; Della Santina et al, 2007; Gong et al, 2008; Tang et al, 2009; Dai et al, 2010, 2011; Davidovics et al, 2011; Rubinstein et al, 2011)
This study shows that a VOR can be evoked by electrically stimulating the ampullae under general anesthesia, in a human with a long-term vestibular loss, and in whom galvanic stimulation did not elicit any response during vestibular testing pre-operatively
Summary
For more than a decade, research has been conducted into development of an invasive vestibular prosthesis (vestibular implant) (Gong and Merfeld, 2000, 2002; Lewis et al, 2002, 2010; Wall et al, 2002; Della Santina et al, 2007; Merfeld et al, 2007; Wall et al, 2007; Gong et al, 2008; Fridman et al, 2010; Davidovics et al, 2011; Guyot et al, 2011a), since non-invasive vestibular prostheses present many drawbacks in restoring vestibular function (Janssen et al, 2010). Electrically stimulated nerve branch (Gong and Merfeld, 2000, 2002; Lewis et al, 2002, 2010; Wall et al, 2002; Della Santina et al, 2007; Merfeld et al, 2007; Wall et al, 2007; Fridman et al, 2010; Davidovics et al, 2011; Guyot et al, 2011a). The ideal stimulus site should be a location with a well-considered compromise between three basic requirements: 1. To be close to the vestibular nerve, in order to give selective stimulation and have as little crosstalk as possible
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