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A Technique for Implantation of a 3-Dimensional Penetrating Electrode Array in the Modiolar Nerve of Cats and Humans
Arunkumar N. Badi, MD;
Todd Hillman, MD;
Clough Shelton, MD;
Richard A. Normann, PhD
Arch Otolaryngol Head Neck Surg. 2002;128:1019-1025.
Background We believe that direct intraneural stimulation of the modiolar nerve
using an array of electrodes will have lower thresholds, offer greater frequency
selectivity and more stimulation sites, and have a greater frequency representation
than conventional cochlear implants.
Objectives To describe a potential auditory prosthesis based on electrical stimulation
of the modiolar cochlear nerve and to report the development of a surgical
approach in human and animal models.
Design Cadaveric human and animal studies conducted in temporal bones indicated
that an array of penetrating microelectrodes could be implanted in the modiolar
nerve. Cat studies using anesthesia were performed to develop the surgical
procedure in an animal model. Nerve viability was assessed by measurement
of electrically evoked auditory brainstem responses at different stages of
the surgery.
Subjects Two fresh cadaveric human temporal bones, 3 cat cadavers, 1 pig cadaver,
and 6 anesthetized cats were used in the experiments.
Results We were able to implant arrays containing 20 microelectrodes in the
human modiolar nerve after exposure by a modified extended facial recess approach.
In animals, the modiolar nerve was accessed by the transbulla and the middle
fossa approach. The cat was chosen as the appropriate animal model, and the
transbulla approach was selected. The round window was exposed by ventral
access to the bulla and after cochleostomy; drilling the modiolar bone exposed
the modiolar nerve. The mean ± SD diameter of the exposed nerve in
cats was 1.64 ± 0.07 mm (n = 9), and the mean ± SD exposed length
was 2.50 ± 0.11 mm (n = 9); this is adequate to accommodate 20 microelectrodes.
The electrically evoked auditory brainstem responses indicated nerve survival
during and after the surgery.
Conclusions The surgical technique allows implantation of up to 20 microelectrodes
in the cat and human modiolar nerve. The nerve survives the surgical procedure.
This work enables studies in the electrophysiological properties and consequences
of long-term implantation.
From the Department of Bioengineering, The University of Utah (Drs
Badi and Normann), and the Division of Otolaryngology–Head and Neck
Surgery, School of Medicine, The University of Utah (Drs Hillman and Shelton),
Salt Lake City.
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