With over 100,000 operations per year performed in Germany alone, thyroid surgery is among the most common surgical procedures. and yet, variations in the anatomy and location of nerves and poor visibility during recurrent tumour operations are the most common reasons for N. recurrens paresis (damage to the vocal cord nerve) - a complication with serious consequences.

Over the past two decades, neuromonitoring has become invaluable as a way of locating and testing the function of the s N. laryngeus. Most hospitals would not want to be without it.

Neuromonitoring helps surgeons to locate the vulnerable vocal cord nerve and test its function. This is done by exciting the nerve by means of minute electric impulses from specific stimulation probes. When the probe tip touches tissue close to the nerve, it triggers an action potential which is carried to the target muscle by the intact nerve. At the target muscle (M. vocalis = vocal cord muscle), a compound muscle action potential (CMAP) is generated, which is recorded through electromyography and made visible and audible to the surgeon.

When introducing VANESSA to the market for the first time in January 2009, Dr. Langer Medical GmbH offered a system that permits continuous monitoring of the vocal nerve. This innovative method involves a stimulation electrode that is placed on the N. vagus during the entire operation. The permanent background stimulation enables the surgeon to notice any changes in the signal immediately and react accordingly, e.g. by avoiding strain on the nerve and thus preventing permanent damage.

Stimulation of the N. laryngeus recurrens produces a characteristic signal that is recorded by EMG. This gives the operating surgeon reliable visual and acoustic feedback on the location and function of the target nerve.

The action potential will not show if stimulation is not close enough to the target nerve, if the nerve has already been damaged or the patient is under the influence of muscle relaxants.

The electric pulse required for nerve stimulation is visible as an artefact in the electromyogram triggered, depending on the probe type and location. It is usually easily distinguished from genuine action potentials.