The History of MED-EL Electrode Arrays

One of the main parts of the implant in a cochlear implant system is the electrode. Electrodes send electrical pulses to the nerve cells within the cochlea. It sounds simple, right? But if they just send signals to the cochlea then why do we have so many different electrode arrays? What is a good electrode design? To learn more, let’s take a journey through the history of MED-EL electrodes.

Designed for Structure Preservation

As we showed in our photographic tour of the cochlea, a normal cochlea is lined with thousands of nerve structures. Keeping these cells intact is one of the best ways to ensure hearing performance both today and in the future.

From the very beginning, MED-EL has pioneered the design and creation of electrode arrays designed specifically to preserve these nerve structures. Here are some highlights from MED-EL’s history of electrode development, starting with one of the very first MED-EL electrode arrays introduced in 1989:

1989: Signature Electrode Features

When MED-EL was founded in 1989, the first of our electrode arrays incorporated two signature electrode features: wave-shaped wires and a free-fitting design. Both of these make for a flexible electrode that can maximize the preservation of the cochlea during a structure-preservation surgery.

The components of an electrode array. From bottom to top: an electrode wire, an electrode wire after the wave shaping, an electrode contact in the middle of an electrode wire, and a contact on the very tip of an electrode wire.

The wave-shaped wires increase the flexibility of the electrode array, and the free-fitting design means that the electrode array can naturally fit to the curves of each individual cochlea.

1994: Complete Cochlea Coverage

In 1994, the first 31.5mm electrode array was introduced by MED-EL. This is special because 31.5mm is the length of the average cochlea. So, an electrode that is 31.5mm long can reach all the way to the very top of the average cochlea. This means it can stimulate the whole length of the cochlea including the nerve cells responsible for the very lowest frequencies of sound.

An electrode array filled with wave-shaped wires and contacts is soft and flexible.

1996: 12-Channel Electrodes

Today, all MED-EL electrode arrays use 12 channels of stimulation. The very first 12-channel electrode, the Standard, was introduced in 1996.

Why do we have 12 channels? The number of channels in an electrode array is a topic that’s talked about a lot in our industry. Often, people believe that more channels makes for better performance. However, research has shown that the optimal number of channels is 12. This is because if channels are placed too close together they can both stimulate the same nerve fibers and therefore create the same sound, 12 channels mean that each channel can be placed to stimulate only a very specific area of the cochlea and therefore not interfere with other channels. Also, this space between each channel (for example, 2.4mm in the Standard electrode) also makes the electrode more flexible.

How the Standard 31.5mm electrode array might look when fully inserted into an average cochlea.

2004: FLEX-Tip Design

A new era of structure preservation started in 2004, when we introduced the FLEX-Tip design for our electrode arrays.

The FLEX-Tip makes an electrode array especially flexible.

The secret to the FLEX-Tip is that the very tip of the electrode array (the first five channels) have only one electrode contact. This makes the tip even smaller and more flexible, so that it can fit better into the tiniest curves at the top of the cochlea.

2011: Expanding Range

In 2011, we expanded our electrode range by introducing the FLEX 28. It’s a 28 mm electrode that uses the FLEX-Tip. Just like a 31.5mm electrode is important because it can be fully inserted into a cochlea of average length, a 28mm electrode array is important because this length is designed to be used in 96% of all typical cochleae.

The tip of a MED-EL electrode array as it fits into a model cochlea. (photo courtesy of Helge Rask-Andersen, MD, Uppsala University Hospital, Uppsala, Sweden)

2013: Electrodes for All

Because we want our cochlear implants to work for everyone, we introduced the FORM series of electrodes. These are designed especially for people whose cochlea is an unusual shape, so that they can still benefit from the closest to natural hearing that our electrodes provide.

FORM series electrode arrays

2018: Individualized Solutions

In 2018 we welcomed a new era in electrodes: Individualized cochlear implants. First, we extended our electrode portfolio even more with the FLEX26 electrode array, meaning we now offer 10 different electrode arrays for cochlear implants—more than any other implant manufacturer.

Advanced new software allows an individualized approach to electrode arrays

Then we introduced OTOPLAN, a surgical planning software that uses incredibly detailed 3D visualization to help surgeons choose the ideal electrode based on the individual anatomy. With this personalized approach to electrodes, our recipients can get the best coverage for their cochlea and enjoy closest to natural hearing.

Want to learn more about the important role that electrodes play in MED-EL cochlear implants? Then discover how they help us mimic natural hearing so you can enjoy closest to natural hearing.

Last updated September 9, 2021