A new system for continuous recurrent laryngeal nerve monitoring.

Existing nerve monitoring devices in thyroid surgery are - except for one - mainly intermittently working nerve identification tools. We present a new vagal electrode which allows true continuous monitoring of the recurrent laryngeal nerve (RLN). The electrode was designed as a tripolar hybrid cuff electrode consisting of polyimide, gold and platinum layers embedded in a flexible silicon cuff which can be opened at the long side for introducing the nerve. It is fully implantable and atraumatic. The evoked potentials are sensed by standard thyroid electrodes. Real-time signal analysis and audio feedback are achieved by specially designed software. Homogeneous and stable signals were recorded throughout the operations. Thus real-time computer-based signal analysis was possible. Evoked potentials reached 300-900 mV. Mean time to place the cuff electrode was 5.5 min. The nerve was stimulated a mean of 63 min (range 55-99 min). No RLN lesions were detected postoperatively. The new vagal electrode was easy to handle and led to stable and reproducible signals. The stimulation current could be kept extremely low due to the special geometry of the electrode. It offers the possibility for uninterrupted, continuous laryngeal nerve monitoring in thyroid surgery. In an ongoing clinical trial its compatibility as an add-on for existing nerve monitoring devices is being tested.