The Laryngoscope C 2015 The American Laryngological, V
Rhinological and Otological Society, Inc.
Letter to the Editor
In Response to Treatment of Epilepsy by Stimulation of the Vagus Nerve From Head-And-Neck Surgical Point of View
Dear Editor: We ask Dr. Alberto Maria Saibene et al. to please accept our thanks for their analysis of our article.1 We thank the authors for their encouraging remarks and for having so clearly pointed out a number of issues that need to be addressed in order to clarify our discussion. We agree with these authors that ENT head-andneck surgeons should be more actively involved in vagus nerve stimulation (VNS) implantation. Our research began when we read a statement from the VNS physician’s manual: “The precise mechanism(s) by which the VNS Therapy System exerts its anticonvulsant action is unknown.”2 Logically, this implies that the precise mechanisms of the laryngeal side effects are also unknown. VNS delivers electric current inside the body. The stimulus currents are introduced into a nervous system with the goal of changing the transmembrane voltage. The electric current affects both excitable tissues: nerves and muscles.3,4 Our current research, unpublished at this time, aims to understand the VNS mechanism of action. Neural axons and whole nerves can be treated as an electrical cable with passive parameters that characterize it per unit length. Body tissues have dielectric properties, but they still have some conductivity and thus can be considered leaky dielectrics. Therefore, our initial step was to move the VNS electrodes as far from the larynx as possible. This approach worked very well, and we were able to reduce laryngeal side effects tremendously. For example, the overall incidence of hoarseness ranged between 12% and 100% in adults and between 8% and 53% in children treated using VNS.5 Our results for hoarseness are well below these ranges. In our departments, we had more pediatric patients than adults, so we dedicated our article to this group of patients. Epileptologists who took care of
our adult patients (we only had 14 of them) did not describe any communication problems between the programming device, and the generator; for all of these cases, the generator was implanted below the pectoralis muscle. Regarding possible damaging of the subclavian artery during tunneling, although the tunnel appears subcutaneously anterior to the clavicle and close to the sternum, the possibility of artery lesion is very remote. The implantation procedure manual states that surgical approach and technique may “vary with the preference of the implanting physician.”6 We were glad to have an opportunity to improve the surgical technique for implantation. MICHAEL VAIMAN, MD, PHD Department of Otolaryngology–Head and Neck Surgery Sackler Faculty of Medicine, Assaf Harofe Medical Center Tel Aviv University, Israel
GAD LOTAN, MD Department of Pediatric Surgery Sackler Faculty of Medicine, Assaf Harofe Medical Center Tel Aviv University, Israel
BIBLIOGRAPHY 1. Lotan G, Vaiman M. Treatment of epilepsy by stimulation of the vagus nerve from Head-and-Neck surgical point of view. Laryngoscope 2014. doi: 10.1002/lary.25064. Epub ahead of print. 2. VNS Therapy System Physician’s Manual. Houston, TX: Cyberonics; 2014: p. 228. 3. Plonsey R, Bar RC. Bioelectricity. A Quantitative Approach, 3rd ed. New York, NY: Springer; 2007. 4. Grimnes S, Martinsen OG. Bioimpedance and Bioelectricity Basics, 2nd ed. Oxford, UK: Elsevier; 2008. 5. Vagus nerve stimulation for epilepsy. Assessment report. MSAC application 1118. Medical Services Advisory Committee. Canberra, 2008. p. 36. 6. VNS Therapy System Physician’s Manual. Houston, TX: Cyberonics; 2014: p. 235.
DOI: 10.1002/lary.25169
Laryngoscope 125: September 2015
Vaiman and Lotan: Letter to the Editor
E327
Rhinological and Otological Society, Inc.
Letter to the Editor
In Response to Treatment of Epilepsy by Stimulation of the Vagus Nerve From Head-And-Neck Surgical Point of View
Dear Editor: We ask Dr. Alberto Maria Saibene et al. to please accept our thanks for their analysis of our article.1 We thank the authors for their encouraging remarks and for having so clearly pointed out a number of issues that need to be addressed in order to clarify our discussion. We agree with these authors that ENT head-andneck surgeons should be more actively involved in vagus nerve stimulation (VNS) implantation. Our research began when we read a statement from the VNS physician’s manual: “The precise mechanism(s) by which the VNS Therapy System exerts its anticonvulsant action is unknown.”2 Logically, this implies that the precise mechanisms of the laryngeal side effects are also unknown. VNS delivers electric current inside the body. The stimulus currents are introduced into a nervous system with the goal of changing the transmembrane voltage. The electric current affects both excitable tissues: nerves and muscles.3,4 Our current research, unpublished at this time, aims to understand the VNS mechanism of action. Neural axons and whole nerves can be treated as an electrical cable with passive parameters that characterize it per unit length. Body tissues have dielectric properties, but they still have some conductivity and thus can be considered leaky dielectrics. Therefore, our initial step was to move the VNS electrodes as far from the larynx as possible. This approach worked very well, and we were able to reduce laryngeal side effects tremendously. For example, the overall incidence of hoarseness ranged between 12% and 100% in adults and between 8% and 53% in children treated using VNS.5 Our results for hoarseness are well below these ranges. In our departments, we had more pediatric patients than adults, so we dedicated our article to this group of patients. Epileptologists who took care of
our adult patients (we only had 14 of them) did not describe any communication problems between the programming device, and the generator; for all of these cases, the generator was implanted below the pectoralis muscle. Regarding possible damaging of the subclavian artery during tunneling, although the tunnel appears subcutaneously anterior to the clavicle and close to the sternum, the possibility of artery lesion is very remote. The implantation procedure manual states that surgical approach and technique may “vary with the preference of the implanting physician.”6 We were glad to have an opportunity to improve the surgical technique for implantation. MICHAEL VAIMAN, MD, PHD Department of Otolaryngology–Head and Neck Surgery Sackler Faculty of Medicine, Assaf Harofe Medical Center Tel Aviv University, Israel
GAD LOTAN, MD Department of Pediatric Surgery Sackler Faculty of Medicine, Assaf Harofe Medical Center Tel Aviv University, Israel
BIBLIOGRAPHY 1. Lotan G, Vaiman M. Treatment of epilepsy by stimulation of the vagus nerve from Head-and-Neck surgical point of view. Laryngoscope 2014. doi: 10.1002/lary.25064. Epub ahead of print. 2. VNS Therapy System Physician’s Manual. Houston, TX: Cyberonics; 2014: p. 228. 3. Plonsey R, Bar RC. Bioelectricity. A Quantitative Approach, 3rd ed. New York, NY: Springer; 2007. 4. Grimnes S, Martinsen OG. Bioimpedance and Bioelectricity Basics, 2nd ed. Oxford, UK: Elsevier; 2008. 5. Vagus nerve stimulation for epilepsy. Assessment report. MSAC application 1118. Medical Services Advisory Committee. Canberra, 2008. p. 36. 6. VNS Therapy System Physician’s Manual. Houston, TX: Cyberonics; 2014: p. 235.
DOI: 10.1002/lary.25169
Laryngoscope 125: September 2015
Vaiman and Lotan: Letter to the Editor
E327
