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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 and patients.
Vagus nerve stimulation (VNS) is a treatment for uncontrolled epilepsy. VNS reduces the frequency and severity of epileptic seizures in some children. VNS involves insertion of a pulse generator, similar to a heart pacemaker, under the skin on the chest that sends intermittent electrical signals to the brain by stimulating the left vagus nerve in the neck. The pulse generator is programmed to stimulate in two ways. It is individually programmed to automatically stimulate in the background, typically ON for 30 seconds and OFF for 3 minutes. In addition, the pulse generator can be manually activated in between programmed stimulation times by the child or caregiver, by placing a provided magnet over the pulse generator and then removing it. This gives extra stimulation at pre-programmed settings.
It is not fully understood how VNS works, but the theory is that the VNS over time modulates nerve pathways involved in seizures. VNS works differently to antiepileptic medications and dietary treatments.
VNS is generally considered for children with epilepsy which significantly affects the life of the child and family, is not adequately controlled by antiepileptic medication, and is not treatable with surgery. Assessment by a paediatric neurologist experienced in comprehensive epilepsy management, including surgery, and VNS therapy is a prerequisite.
The vagus nerve is one of the cranial nerves, meaning a nerve that is connected directly to the brain. Output nerve fibres control muscles responsible for swallowing, coughing and voice sounds. Input nerve fibres transmit sensations and electrical feedback from the heart, lung, stomach and upper bowel to the brain. About 80% of the nerve fibres in the left vagus nerve are input fibres transmitting, from the body to the brain, and the output fibres have minimal heart connections, making the left vagus nerve a suitable "wire" into 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.
Children require referral from their neurologist or paediatrician to an epileptologist at the RCH for assessment of suitability. The child's seizure history, prior and current treatments, behaviour and past medical problems need to be reviewed. Alternative treatments are also discussed.
Families are fully informed about VNS before embarking on this form of treatment. The epileptologist and the epilepsy nurse specialist discuss realistic expectations of VNS, how VNS works, the surgical procedure, post operative care, advantages and disadvantages, continuing medication, the admission process and precautions. Families will meet with the neurosurgeon prior to planned surgery.
The child and family present to the Surgical Admissions reception on the 3rd floor on the morning of surgery. Usual medications are taken unless otherwise instructed by the 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, antiepileptic medications and wound care. Parents may accompany their child to the pre-theatre waiting area.
Implantation of the VNS pulse generator and lead wire 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 pulse generator 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 wrapped around the left vagus nerve. The VNS unit is tested prior to skin closure but then left off.
Diagrammatic View of insertion of VNS
Post-operative VNS insertion scars
Children are admitted to the Cockatoo Ward following surgery and usually stay in hospital for one or two nights. Fluids and antibiotics are given by intravenous drip for at least 24 hours. 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 and easy assessment of the wounds. No stich removal is required, as all stitches dissolve under the skin.
Antiepileptic medications remain unchanged.
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.
Neurosurgical follow up occurs shortly after discharge from hospital and assessment of wound site will occur at this visit. Regular appointments are scheduled with the neurologist, usually every 4 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.
VNS has been extensively studied in clinical trials around the world, including in children. The results vary depending on the patients studied and the design of the trial.
The following is our summary of the available data:
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.
Physical trauma to the pulse generator or lead wire, such as with rough sport or neck manipulation, can damage the device.
Equipment that may interfere with the stimulator should be avoided. These include strong magnets, hair clippers and loudspeakers. Some medical tests, such as MRI scans, can interfere with the device. Always tell health professionals that your child has a VNS implanted.
The neurologist or epilepsy nurse specialist should always be consulted prior to any medical imaging, diagnostic testing or surgical procedures, to ensure patient safety and device integrity. The pulse generator may need to be turned off temporarily and special precautions may need to be taken with anaesthesia, surgery or scanning.
*Always 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.
Funding for VNS in Australia is complex, and varies between states and centres. The VNS device and stimulating lead (NeuroCyberonics Prothesis® 102) actual cost is approximately $15,600. The VNS device contains a battery, which lasts between 7-10 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. Private health insurers should cover the cost of the device, as VNS Therapy is on the Australian Prosthesis List, but not the surgical procedure. Some public hospitals have allocated funds for VNS therapy in public patients whose epilepsy meets specific criteria. The specific funding issues that apply to families should be discussed with the treating neurologist.
The following company sites may be useful for further general information regarding VNS.