Dr. Dirk Arnold (Jena, DE), Gerhard Förster (Gera, DE), Prof. Dr. Andreas Müller (Gera, DE), Kassandra Walluks (Jena, DE), Jan-Philipp Praetorius (Jena, DE), Bianca Hoffmann (Jena, DE), Marc Thilo Figge (Jena, DE), Justin Perkins (London, GB), Orlando Guntinas-Lichius (Jena, DE), Gerd Fabian Volk (Jena, DE)
Abstract text (incl. figure legends and references)
Introduction
This presentation reports on biocompatibility and functionality of a laryngeal pacemaker (LP) system for treatment of bilateral vocal fold paresis by electrical stimulation of the posterior cricoarytenoid muscle (PCA) and of electromyography (EMG) electrodes for recording the myoelectric activity of the stapedius muscle (SM) in long-term trials. The contraction of the PCAs opens the vocal folds during inspiration and the SM contracts during loud sounds (stapedius reflex). The two systems were implanted in different ways.
Material & Methods
The LP system consists of a stimulation unit and 2 linear electrodes (silicone coated) with spiral tips, screwed into both PCAs in 18/22 (4 controls) adult female Merino sheep. The left recurrent laryngeal nerve was cryo-damaged and after 6 months of recovery, PCA stimulation was conducted (6 months) in 10/18 (8 shams) sheep.
The EMG electrodes were made of silicone-coated platinum/iridium wires with a contact area of Ø 1 mm. Two of them were placed at the SM belly in another 10 sheep. Control measurements were done after 1, 3 and 6 months. Finally, the sheep of both experiments were euthanized and the PCAs or SMs were collected for histological examinations (H&E and Azan staining).
Results
The implanted LP electrodes activated the PCAs reliably for 12 months. EMG recordings were possible for 6 months. A 0.5 mm thick fibrous encapsulation was present around the LP electrodes in the PCA, which was characterized by deposits of collagen, atrophy of muscle fibers, and aggregation of macrophages. An encapsulation of the stapedius EMG electrodes was not detected.
Conclusion
The PCA scars are likely caused by mechanical stress (intramuscular), which did not occur around the superficially placed EMG electrodes. The results confirmed both the performance and the safety of the 2 evaluated implantable devices in sheep, which proved itself to be a valid animal model for both types of testing.