Vagal Nerve Stimulation
- What is vagal nerve stimulation?
- Who is vagal nerve stimulation for?
- What does the vagus nerve do?
- History of VNS
- What does a vagal nerve stimulator look like?
- What is involved prior to vagal nerve stimulation?
- What happens during the admission for insertion of a vagal nerve stimulator?
- Does it work?
- What side effects or problems can occur?
- Environmental Precautions
- What is the cost of a Vagal Nerve Stimulator?
- References and links
The text on this page is abstracted from Cyberonics physician and patient information as well as published reviews and clinical studies. Photographs reproduced with permission from Cyberonics.
What is vagal nerve stimulation?
Vagal nerve stimulation (VNS) is a potential treatment for uncontrolled seizures. The aim of vagal nerve stimulation is to reduce the frequency and intensity of seizures. It involves insertion of a device, similar to a cardiac pacemaker, under the skin on the chest that will send intermittent electrical signals to the brain by stimulating the left vagus nerve in the neck. The device stimulates in two ways. It is individually programmed to automatically stimulate; typically the stimulator activates ON for 30 seconds and OFF for 3 minutes. In addition, the device can be manually activated in between programmed stimulation times; the patient or caregiver places a magnet over the stimulator and then removes it, this giving extra stimulation at pre-programmed settings.
It is not fully understood how VNS works, but the theory is that the stimulation alters nerve pathways that lead to a seizure.
Who is vagal nerve stimulation for?
Vagal nerve stimulation is generally only considered for a child with epilepsy who has seizures not controlled by medication and who is not a candidate for surgery. Assessment by a paediatric neurologist experienced in epilepsy management and monitoring of VNS is a prerequisite.
What does the vagus nerve do?
The vagus nerve is one of the cranial nerves, meaning a nerve that is connected directly to the brain. Output (movement) nerve fibres control muscles responsible for swallowing, coughing and voice sounds. Input (sensation) nerve fibres transmit taste sensations and electrical feedback from the heart, lung and stomach to the brain. About 80% of the nerve fibres in the left vagus nerve are input (sensory) fibres transmitting from the body to the brain.
History of VNS
Researchers discovered brain wave patterns of animals were altered when the brain was stimulated electrically and this led to the development of brain stimulation as a treatment for seizures. The left vagus nerve serves as a "wire" to the brain and avoids the need for wires to be inserted directly in the brain.
The first VNS device was implanted in 1988 in the United States of America. Regulatory approval as an adjunct therapy in reducing seizure frequency was granted in 1994 in Europe and 1997 in USA. The first implant in Australia was in 1994 and regulatory approval by the Therapeutic Goods Administration (Australia) was granted in April 2000. More than 20,000 people worldwide have had a VNS implanted, 5,500 of this number being under 18 years of age. In Australia since 1994, a total of 146 people have had a VNS implant, 66 of this number being children. The device has been replaced in 13 adults and 5 children following battery end of life.
What does a vagal nerve stimulator look like?
What is involved prior to vagal nerve stimulation?
- Initial assessment
All children and families require a referral from their neurologist or paediatrician to the Children’s Epilepsy Program (CEP) for assessment of suitability. Elements of the child’s seizure history, treatment, behaviour and past medical problems need to be reviewed. Alternative treatments are also discussed.
- Education
Families must be fully informed about VNS before embarking on this form of treatment. The paediatric neurologist and the epilepsy nurse specialist discuss at length the broad aims of VNS, how VNS works, the surgical procedure, post operative care, advantages and disadvantages, continuing medication, the admission process, ongoing management at home and precautions. Additional information is available in the form of video, written material and formal "one on one" discussions. The Epilepsy Nurse Specialist provides ongoing support and reinforcement of education sessions. Families will meet with the neurosurgeon prior to intended surgery.
What happens during the admission for insertion of a vagal nerve stimulator?
- Pre-operation
The child and family are admitted to the Neuroscience Unit (6 West) on the morning of the scheduled surgery. Usual medications are taken unless otherwise instructed by your neurologist. The anaesthetist assesses the child and routine blood tests are performed. Post-operative care is discussed with medical and nursing teams, particularly relating to pain management, oral intake, seizure management and documentation, antiepileptic medications, wound care and any other issues that may need clarifying. Parents may accompany children to the pre-theatre waiting area.
- The surgical procedure
The implantation of the VNS device requires an operation, which usually takes two hours. Children require a general anaesthetic and at least an overnight stay in hospital. Two incisions are made to implant the stimulator device and lead wire, one horizontally on the left side of the chest below the collar bone (clavicle) and one vertically in a skin fold on the left side of the neck. The stimulator with lead wire connection is inserted under the skin on the upper left chest wall. The lead wire is passed under the skin and the contacts are attached to the left vagus nerve.
Diagramatic View of insertion of VNS
The device is tested prior to wound closure and maybe programmed initially to deliver the lowest amount of stimulation. Stimulation is usually programmed to occur for 30 seconds every 5 minutes.
- Surgical procedure photographs
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Post operation
Post-operative VNS insertion scars
Children return to the Neuroscience Unit following the surgery and usually stay in hospital for one or two nights. Frequent assessment of child’s conscious state and vital signs are made initially. Fluids are given by intravenous drip until the child is tolerating oral diet and fluids.
Regular assessment of the child’s comfort continues throughout the hospital stay and oral pain killers are administered as required. Most children have minimal pain that is controlled by paracetamol. Oral pain killers continues at home as necessary.
The two wound sites are covered with a clear waterproof dressing which allows for normal bathing habits and easy assessment of the wounds. No stich removal is required, as all stitches dissolve under the skin.
Antiepileptic medications remain unchanged, unless reviewed by the neurologist.
The VNS is turned on 10 days post insertion.
The scars will be quite reddened initially and will fade to white with time, depending on individual healing processes. In some people, scars on the chest remain red and may thicken and become raised.
- Follow up
- Regular appointments are scheduled with the neurologist, usually every 2 weeks initially. During these visits the functioning of the VNS is checked, seizure history noted and the stimulating parameters increased, as tolerated, towards settings which are usually effective.
Neurosurgical follow up occurs shortly after discharge from hospital and assessment of wound site will occur at this visit.
Does it work?
VNS has been extensively studied in clinical trials around the world, including in children. The results vary somewhat in different centres, depending on the patients studied.
The following is our summary of the available data:
- About 50% of patients gain a significant improvement in seizures
- Less than 10% of patients become seizure free and most continue taking antiepileptic medication
- Results are similar across all seizure types and syndromes, although there is some suggestion that children with Lennox-Gastaut syndrome and other severe epilepsies may respond better
- Termination of complex partial or secondarily generalised seizures, prolonged seizures, or seizure clusters is possible in some patients
- Currently there is no way to predict response to VNS
- Many patients have improvements in mood, alertness and overall quality of life, even in the absence of significant seizure improvement
- Seizure reduction is often not evident for several months
- Over time there may be a continued decline in seizures in many patients. 25% may have a reduction in seizure frequency at 3 months, increasing to 50% after 2 years
What side effects or problems can occur?
- The most common side effects reported are: hoarse voice, pain or tingling in the throat or neck, cough, headache and ear pain. These effects are generally related to stimulation settings and settle over time or after reduction of stimulation.
- Less common side effects possibly associated with stimulation are difficulty sleeping, weight change, shortness of breath, vomiting, facial flushing, dizziness and irritability
- Swallowing problems and rarely aspiration may occur in some disabled children with feeding difficulties and reflux
- Wound breakdown, wound infection and device damage are rare but potentially serious complications
- Cessation of heart beat has been reported in 4 adults undergoing VNS implantation, during the intraoperative lead test this has not been reported in children
Our experience with VNS at the Royal Children's Hospital
We reviewed the outcome of VNS in 12 children aged 6-16 years who were implanted with VNS devices between 1998-2000. Duration of VNS therapy was 2.6 to 5.3 years. Eight children had multiple-daily seizures, including 4 with drop attacks and 3 with recurrent bouts of status requiring hospitalisation.
VNS was removed in 2 children because of behaviour disturbance in one and weight loss and discomfort in another. Of the 10 patients who continue with VNS therapy 4 have had >50% seizure reduction, 3 have had 30-40% seizure reduction, and 3 have had no real change in seizures. Drop attacks ceased in 2 and status requiring hospitalisation ceased in 3. No child is totally seizure-free and only 1 had medication reduced. All five NCP100 devices were replaced at 3 years for diminished efficacy.
Environmental Precautions
Equipment that may interfere with the stimulator should be avoided. These include strong magnets, hair clippers and loudspeaker magnets. Some medical tests, such as MRI scans, can also interfere with the device and it is always recommended that the neurologist or epilepsy nurse specialist be consulted prior to any medical diagnostic testing.
*Avoid areas where pacemaker warning signs are posted.
The magnet provided for manual stimulation may damage credit cards, mobile phones, computer disks, televisions and other items affected by strong magnetic fields. Care should be taken to store magnet away from these types of equipment.
What is the cost of a Vagal Nerve Stimulator?
The VNS device and stimulating lead (NeuroCyberonics Prothesisﾮ 102) actual cost is approximately $15,600. The VNS device contains a battery, which lasts between 10-12 years depending on the programmed output current and frequency of stimulation. The replacement cost of a VNS device with a new battery is approximately $11,600.
Some private health insurance companies will cover the cost of the device and the surgery. Families with private health cover should contact their insurance provider to ascertain their level of cover. It is helpful to quote the following rebate code for the Vagal Nerve Stimulator - TB 130. A problem exists currently in that there is no specific CMBS item number for the procedure of inserting the stimulator. This would need to be discussed with the doctor and health insurer.
For non-private Victorian patient's, several public Melbourne hospitals have allocated funds for VNS therapy available through a DHS grant. These funds are limited to non-private patients whose epilepsy meets specific criteria. The specific funding issues that apply to families should be discussed with the treating Neurologist.
Commercial Links
The following company sites may be useful for further general information regarding VNS.
- Cyberonics, Inc. (manufacturer of the VNS device)
http://www.vnstherapy-international.com/
- Distributer in Australia - Aurora Bioscience
Selected References
Original Controlled Trials of VNS
- Ben-Menachem E et al. Vagus Nerve Stimulation for Treatment of Partial Seizures: 1. A Controlled Study of Effect on Seizures. Epilepsia 1994; 35: 616-26. [PubMed]
- Ramsey RE et al. Vagus Nerve Stimulation for Treatment of Partial Seizures: 2. Safety, Side Effects, and Tolerability. Epilepsia 1994; 35: 627-36. [PubMed]
- George R et al. Vagus Nerve Stimulation for Treatment of Partial Seizures: 3. Long-Term Follow-Up on First 67 Patients Exiting a Controlled Study. Epilepsia 1994; 35: 637-43.[PubMed]
- The Vagus Nerve Stimulation Study Group. A randomized controlled trial of chronic vagus nerve stimulation for treatment of medically intractable seizures. Neurology 1995; 45: 224-30. [PubMed]
- Ben-Menachem E et al. Evaluation of refractory epilepsy treated with vagus nerve stimulation for up to 5 years. Neurology 1999; 52: 1265-7. [PubMed]
VNS Studies in Children
- Murphy JV et al. Adverse Events in Children Receiving Intermittent Left Vagal Nerve Stimulation. Pediatr Neurol 1998;19:42-3. [PubMed]
- Parker APJ et al. Vagal Nerve Stimulation in Epileptic Encephalopathies. Pediatrics 1999; 103:778-82. [PubMed]
- Murphy JV and the Pediatric VNS Study Group. Left vagal nerve stimulation in children with medically refractory epilepsy. J Pediatrics 1999;134:563-6. [PubMed]
- Helmers SL et al. Vagus nerve stimulation therapy in pediatric patients with refractory epilepsy: retrospective study. J Child Neurol 2001;16:843-8. [PubMed]
- Frost M et al. Vagus nerve stimulation in children with refractory seizures associated with Lennox-Gastaut syndrome. Epilepsia 2001;42:1148-52. [PubMed]
- Nagarajan L et al. VNS therapy in clinical practice in children with refractory epilepsy. Acta Neurol Scand 2002;105:13-7. [PubMed]
- Wheless JW and Maggio V. Vagus nerve stimulation therapy in patients younger than 18 years. Neurology 2002;59(Suppl 4):S21-5. [PubMed]
- Murphy JV et al. Vagal nerve stimulation in refractory epilepsy: the first 100 patients receiving vagal nerve stimulation at a pediatric epilepsy center. Arch Pediatr Adolesc Med 2003;157:560-4. [PubMed]
Reviews of VNS
- Boon P et al. Cost-benefit of vagus nerve stimulation for refractory epilepsy. Acta Neurol Belg 1999;99:275-80. [PubMed]
- Valencia I et al. Vagus nerve stimulation in pediatric epilepsy: a review. Pediatr Neurol 2001;25:368-76. [PubMed]
- Ben-Menachem E. Vagus-nerve stimulation for the treatment of epilepsy. Lancet Neurology 2002;1:477-82. [PubMed]