ISPUB.COM The Internet Journal of Neurology Volume 21 Number 1 DOI: 10.5580/IJN.54164 1 of 6 Assessing The Autonomic Effect Of Vagal Nerve Stimulation With Low Level Lasers By Heart Rate Variability C Machado, Y Machado, M Chinchilla, Y Machado, H Foyaca-Sibat Citation C Machado, Y Machado, M Chinchilla, Y Machado, H Foyaca-Sibat. Assessing The Autonomic Effect Of Vagal Nerve Stimulation With Low Level Lasers By Heart Rate Variability. The Internet Journal of Neurology. 2019 Volume 21 Number 1. DOI: 10.5580/IJN.54164 Abstract Vagus nerve stimulation (VNS) has been approved to treat refractory epilepsy, and for other conditions. The invasive nature of the electrical stimulus, which requires surgical implantation of electrodes around the cervical vagus nerve, is a technical limitation. The low-level laser therapy (LLLT) is actually considered a non-invasive technique, and has been increasingly used in diverse areas of medical practice. We developed a pilot study using LLLT for VNS in normal subjects, and assessing its effect on the autonomic nervous system (ANS) by the heart rate variability (HRV) methodology. Fifteen normal participants from 22 to 46 years, divided in three groups of 5 subjects each, paired in age and gender, were studied applying VNS using LLLT by lasers of different frequencies: RED Laser (in 5 subjects); VIOLET Laser (5 subjects); and RED/VIOLET Laser (5 subjects). The study included three experimental conditions: Basal record (10 minutes), VNS (10 minutes), and Post-VNS (10 minutes). The LF/HF ratio was considered, because it provides a measurement of the parasympathetic/sympathetic balance. When the RED laser was used for VNS there was a predominance of the parasympathetic activity. On the contrary, the stimulus with VIOLET laser provoked a sympathetic prevalence. Similarly, to the stimulus with the RED laser, when the RED/VIOLET laser was applied there was a predominance of the parasympathetic activity. As a conclusion, this study showed that VNS using LLLT is a non- invasive and safe method, and should be considered for future protocols to recover prasympathetic/sympathetic nervous system balance in different conditions. INTRODUCTION Electrical stimulation of the cervical vagus nerve has been approved for the treatment resistant epilepsy. In Europe and the USA for over 15 years has been used to treat about 50,000 epilepsy patients.(1-4) Vagus nerve stimulation (VNS) is also an approved therapy for treatment of resistant depression, and has been investigated as a potential therapy for a wide range of conditions including heart failure, Alzheimer's disease, obesity, chronic pain, inflammation, and tinnitus.(5-13) It is interesting that VNS has proven effective in pilot studies for the treatment of heart failure. Heart failure is a leading cause of mortality and it is estimated that 50% of people die within 5 years of diagnosis. Heart failure is characterized by decreased parasympathetic and increased sympathetic nerve activity. Therefore, if VNS can be shown to influence this autonomic balance toward parasympathetic predominance it could provide a method to correct imbalance in heart failure patients, and in other diseases.(7, 8, 14-18) On the other hand, the use low-level laser therapy (LLLT) is actually considered a non-invasive technique, and has been also increasingly used in diverse areas of medical practice, such as prevention of tissue death, pain relief, reduction of inflammation, regenerative medicine, traumatic brain injury, , spinal cord injury, and stroke, autism, etc.(19-25) One factor that may hinder larger trials of VNS is the invasive nature of VNS. VNS requires surgical implantation of a bipolar electrode around the cervical vagus nerve and implantation of a generator subcutaneously in the thoracic wall. This is associated with technical and surgical complications including wound infection, cardiac arrhythmia under test stimulation and electrode malfunction [9]. In addition, side effects include hoarseness, dysphagia, cough