The easy way to achieve perfect symmetry in bilateral implantations

By: Oticon Medical
Date: 8 April 2021

In recent years, the number of patients who have benefited from bilateral cochlear implantations has increased substantially thanks to an expansion of indications and an increase in awareness in several countries around the world. However, bilateral implantations can present some challenges, for example regarding cosmetic appearance and achieving perfect symmetry with right-left placement of implants. The Neuro Processor Indicator is a new surgical tool specifically designed to achieve this symmetry. Physicians from the Hannover Medical School (Germany) appreciated how it can support surgeons in their clinical practice when handling bilateral cochlear implantations.

The importance of symmetry

Cochlear implant systems need to provide a number of benefits including high levels of reliability and safety, as well as the best possible audiological outcomes. Cosmetic aspects are often underestimated as relevant outcomes, yet recipients of bilateral implantation expect devices to be positioned symmetrically. Psychological studies show how symmetry has a positive and significant influence on the perception of beauty¹. Simply put, humans are biologically programmed to find symmetry beautiful. As asymmetry between the two implant locations can be visible and may lead to dissatisfaction that cannot easily be addressed, precise surgical planning of symmetrical incisions and implant sites is required. This is especially relevant for pediatric implantation as skull growth can magnify any initial asymmetry.

Until now, surgeons have had limited solutions available to address the need for symmetry. Some use a “mirror template” and trace and fold a transparent operative drape to copy the location on the opposite side². This technique works especially well in simultaneous bilateral implantation. However, it cannot be easily used to manage sequential bilateral implantation.

“Offering a tool that enhances symmetry between the two ears – or gives the surgeon the possibility to accurately align the two sides – is a huge advantage,” comments Prof. Andreas Büchner, Head of Research at the German Hearing Center (Hannover, Germany).

The Neuro Processor Indicator
- Perfect symmetry and positioning

To achieve symmetry in all implantation cases, Oticon Medical has created the Neuro Processor Indicator. This is a reusable surgical tool made of stainless steel that is used to select the position of the implant before surgery and to identify this position during surgery. The angle markings, on both sides of the tool (shown as 1–4 in Fig.1), are relative to orbitomeatal line and represent different implant positions (lower or higher on the skull). The Neuro Processor Indicator reproduces the shape of the Neuro 2 sound processor, with an extra 1 cm in width. This extra width ensures sufficient distance from the implant to the sound processor to allow optimal signal transfer from the Oticon Medical Streamer XM to the sound processor.

To use the Neuro Processor Indicator, follow the steps below:

1. Place the Neuro Processor Indicator behind the pinna (Fig.2). 
2. Align the anterior edge of the Neuro Zti implant indicator against the posterior edge of the Neuro processor Indicator. 
3. Mark the position of the posterior edge of the Neuro Processor Indicator on the skin. The angle markings help to position the implant at the desired angle, relative to the orbitomeatal line. 
4. Mark the contour of the implant receiver. 
5. Proceed to the skin flap incision at the posterior edge of the pinna.

Bilateral implantations
- For symmetry and selecting the best position

The Neuro Processor Indicator ensures that the distance from the pinna is optimal. Its angle markings serve two purposes. First, they ensure right-left symmetry by tracking the angle in relationship to the orbitomeatal line. In sequential bilateral implantations, the tool allows the surgeon to document the position of the first implant (angle) so it can be used for the second implant. 

Second, the angle markings show different possible implant positions. The patient and professional can choose the angle marking that matches their cosmetic requirements and best fits the head shape. The angle marking 1 is the highest on the skull and represents the largest angle from the orbitomeatal line.

Prof. Thomas Lenarz, ENT department director (Hannover Medical School, Germany), comments, “For bilateral implantations, it is necessary that we place the implant in the same position on both sides. Any help to do this properly is of course useful. It will probably also save time”.

Watch this 3-minute video introducing the Neuro Processor Indicator, with the full interview with Thomas Lenarz and Andreas Büchner.

Unilateral implantations
- For correct positioning

The Neuro Processor indicator should also be used in unilateral implantations. This will ensure that the sound processor and implant do not overlap. It can also enhance the patient’s wearing comfort, for example if the patient wears glasses, and enable optimal signal transmission from the Oticon Medical Streamer XM to the sound processor.

Using the Neuro Processor Indicator provides many benefits and is recommended for all Oticon Medical Neuro Zti implant surgeries.

1. Rhodes G. The evolutionary psychology of facial beauty. Annu Rev Psychol 2006;57:199-226.
2. Hallwachs AJ, Weinstein JE, Reilly BK. Cochlear implant symmetry via template. Int J Pediatr Otorhinolaryngol 2018;105:40-42.