Only 0. In fact, careful monitoring of patients receiving VNS for up to three years has revealed no clinically relevant effects on cardiac function. If right-sided VNS is safe, the question remains if it is effective. In animal models, the answer is yes. In one study, a cuff electrode was implanted on the left or right cervical vagus nerve in two groups of rats.
The highest seizure stage attained within 15 minutes was rated by a blinded observer. In a later animal study, anesthetized pigs were implanted with a cuff electrode on the cervical vagus nerve and then spinal cord seizures were induced with a topical application of penicillin.
Cervical VNS, regardless of whether it was applied on the left[ 31 ] or right[ 32 ] side, significantly reduced this seizure activity. This has now been demonstrated clinically in three separate studies. McGregor and colleagues[ 17 ] published the first case report of patients who received right-sided VNS.
All three patients were children who had been implanted with a left-sided VNS system and had the system explanted due to postoperative infection. Although efficacy could not be determined in one of the patients because the system was removed before being initiated, the other two achieved significant seizure reductions from left-sided VNS. After several attempts at re-implanting the equipment on the left side only to fail because of the persistence of the infections, the physicians decided to attempt placement of the equipment on the right side.
The surgeries were uneventful; intraoperative lead tests were performed with no detectable effects on cardiac function. Subsequent Holter monitoring of the patients revealed no postoperative VNS-induced cardiac effects.
No detectable effects on respiration were observed in two patients; the third developed exercise-induced reactive airway disease which was unresponsive to medication. The right-sided system was explanted in this patient and the respiratory problem resolved. Notably, this was the only patient who did not achieve a good seizure response to right-sided VNS. Both the first two patients had significant seizure reductions with right-sided VNS, and continued treatment with no observable side effects.
The second clinical report of right-sided VNS involved another child who was originally receiving left-sided VNS that was subsequently removed due to postoperative infection. Intraoperative testing revealed significant bradycardia, but this was not seen postoperatively.
Holter monitoring revealed no cardiac effects as the VNS parameters were increased. Finally, in a third case report, two adult patients received right-sided VNS after surgical complications precluded the use of left-sided VNS. Intraoperative lead tests did not reveal any cardiac events. Holter monitoring was used in both patients when the devices were initiated and after subsequent amplitude increases.
In an interesting study, patients with left-sided VNS were studied with surprising results. After reviewing all of the preoperative data to determine a predictive variable, only one variable was independently correlated with complete seizure remission: lack of bilateral interictal epileptiform discharges. That is, left-sided VNS produced a seizure-free outcome only in patients who had lateralized interictal discharges.
Remarkably, when queried about the laterality of the discharges, the investigators reported that five of the six patients who had become seizure-free from left-sided VNS had discharges localized to the left ipsilateral hemisphere Janszky and Ebner, personal communication.
These case reports provide important clues that may have been long overlooked because of the reports from early animal research. Stimulation of the right-sided cervical vagus nerve appears to be feasible, both from a safety and efficacy perspective. Second, the laterality of VNS effects may be important for the ultimate goal of any epilepsy therapy: complete remission of seizures.
This laterality hypothesis has yet to be systematically tested, but it is intriguing to speculate that right-sided or even bilateral VNS might be viable alternatives in patients receiving sub-optimal results from left-sided VNS. The unique anatomy of the vagus nerve provides a convenient peripheral medium in which to influence the brain without the invasiveness of intracranial surgery.
While clinical efficacy is often modest, VNS has been successful, due in large part to patient acceptability, safety, and a low incidence of side effects. Future studies exploring the possible laterality of VNS effects, possibly leading to bilateral VNS, and further understanding of fiber selectivity may lead to improvements of the therapeutic effect, not only for epilepsy, but also for major depression and other future VNS indications.
Disclaimer: The authors of this paper have received no outside funding, and have nothing to disclose. National Center for Biotechnology Information , U. Journal List Surg Neurol Int v. Surg Neurol Int. Published online Jan Scott E. Author information Article notes Copyright and License information Disclaimer.
Krahl: ude. Received Dec 21; Accepted Dec This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
This article has been cited by other articles in PMC. Additionally, researchers are studying vagus nerve stimulation as a potential treatment for a variety of conditions, including headaches, rheumatoid arthritis, inflammatory bowel disease, bipolar disorder, obesity and Alzheimer's disease.
For most people, vagus nerve stimulation is safe. But it does have some risks, both from the surgery to implant the device and from the brain stimulation. Surgical complications with implanted vagus nerve stimulation are rare and are similar to the dangers of having other types of surgery. They include:. Some of the side effects and health problems associated with implanted vagus nerve stimulation can include:. For most people, side effects are tolerable. They may lessen over time, but some side effects may remain bothersome for as long as you use implanted vagus nerve stimulation.
Adjusting the electrical impulses can help minimize these effects. If side effects are intolerable, the device can be shut off temporarily or permanently. It's important to carefully consider the pros and cons of implanted vagus nerve stimulation before deciding to have the procedure.
Make sure you know what all of your other treatment choices are and that you and your doctor both feel that implanted vagus nerve stimulation is the best option for you. Ask your doctor exactly what you should expect during surgery and after the pulse generator is in place.
You may need to stop taking certain medications ahead of time, and your doctor may ask you not to eat the night before the procedure.
Before surgery, your doctor will do a physical examination. You may need blood tests or other tests to make sure you don't have any health concerns that might be a problem. Your doctor may have you start taking antibiotics before surgery to prevent infection.
Surgery to implant the vagus nerve stimulation device can be done on an outpatient basis, though some surgeons recommend staying overnight. The surgery usually takes an hour to an hour and a half.
You may remain awake but have medication to numb the surgery area local anesthesia , or you may be unconscious during the surgery general anesthesia. The surgery itself doesn't involve your brain. Two incisions are made, one on your chest or in the armpit axillary region, and the other on the left side of the neck. The pulse generator is implanted in the upper left side of your chest.
The device is meant to be a permanent implant, but it can be removed if necessary. The pulse generator is about the size of a stopwatch and runs on battery power. A lead wire is connected to the pulse generator.
The lead wire is guided under your skin from your chest up to your neck, where it's attached to the left vagus nerve through the second incision. Surgeons implant a device near the collarbone and run a wire to the vagus nerve. It is designed to change how brain cells work by giving electrical stimulation to certain areas involved in seizures.
The vagus nerve is part of the autonomic nervous system, which controls functions of the body that are not under voluntary control such as heart rate and breathing.
The vagus nerve sends information from the brain to other areas of the body. It also carries information from the body to the brain. Donate to Support Our Mission. This therapy does not cure epilepsy. VNS is used for people with refractory or drug-resistant epilepsy.
This means seizures are not controlled after trying at least 2 appropriate seizure medications. When considering VNS, ideally a person is first seen at a comprehensive epilepsy center to make sure that all options have been explored and that the procedure is right for them.
Referral will be sent if the group decides that VNS is the best option and you and your child agree. An appointment will be scheduled for you and your child to meet the doctor neurosurgeon and discuss the procedure. Then we schedule the surgery. Keep the wound clean and dry. Sutures stitches are self-absorbing and do not need to be removed. It is OK to wash the incision with soap and water after 3 days. Watch for redness, swelling or drainage from incision sites.
More detailed instructions will be given before discharge from the hospital. Neurology follow up: Patients may be scheduled for up to five appointments for follow-up in the Neurology clinic.
These appointments are about 2 weeks apart. The appointments are scheduled in order to gradually increase VNS settings to a therapeutic range.
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