Vagus Nerve Stimulator
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Some children who have epilepsy might benefit from the Vagus Nerve Stimulator (VNS). The small device — about the size of a pacemaker — is implanted in a child’s upper chest. The VNS sends programmed electrical signals to the vagus nerve, the only nerve in the body that extends from the brain to the neck, chest and abdomen. The electrical stimulation that the VNS delivers can help reduce the frequency of a child’s seizures.
Seizure Types
The VNS can be useful for treating children who have partial and generalized seizures, atonic seizures and tonic clonic seizures.
Side Effects
Possible side effects of VNS therapy include:
- Change in voice quality while the VNS sends its electrical signals
- Hoarseness
- Cough or tickling in throat
Side effects associated with the surgical placement of the device also can occur.
More Information
What Is a Vagus Nerve Stimulator (VNS)?
If antiseizure medications are unsuccessful in reducing the frequency and severity of seizures, the implantation of a Vagus Nerve Stimulator (VNS) might be recommended. In 1998, the Food and Drug Administration approved the VNS for patients who have intractable epilepsy. About the size of a pacemaker, a VNS sends programmed electrical signals to the vagus nerve in the neck, stimulating the nerve and thus helping to prevent epileptic seizures.
How Does a VNS Work?
A battery-operated generator is implanted below the skin on the left anterior chest wall. See our VNS animated illustration to get a better idea of how the device operates. A neurosurgeon attaches electrodes from the device to the left vagus nerve (the VNS implantation does not involve surgery on the brain).
Implantation of a VNS usually requires an overnight hospital stay. A neurosurgeon makes a small incision in a child’s upper chest and places the VNS and connecting wires under the skin. The wires connect to a stimulating electrode, which is placed on the vagus nerve. Using an external programmer, we then program the VNS for a particular rate and intensity of stimulation. Usually, your physician modifies the programmed settings for a few weeks to determine which is most effective.
After implantation, the VNS generator is programmed by a health-care provider to deliver an appropriate dose of electrical stimulation. The current is gradually increased, typically at one- to two-week intervals, until the target therapeutic dose is reached. There’s also the possibility of providing additional stimulation (which can be self-administered or given by a caregiver) by placing — or swiping — a magnet over the chest where the generator is implanted. This magnetic activation of the VNS generator will stop or shorten a seizure in approximately 25 percent of patients who receive the implant. Every few years, the VNS battery must be surgically replaced.
Who Might Benefit From a VNS?
Although a VNS has been shown to reduce the frequency of seizures, it does not usually eliminate them. Your neurologist will evaluate the frequency, severity and side effects of your child’s seizures before recommending treatment.
Children who have failed to respond to antiepileptic drugs (such as carbamazine, phenytoin, valporic acid, neurontin, phenobarbitol or mysoline) might benefit from a VNS. Often, a VNS is combined with such medications, which might allow for a decreased dosage and fewer corresponding side effects. There are no stringent age limits for the surgery.
Thus far, outcome data demonstrate that about one-third of patients experience major improvement in seizure control; one-third experience enough improvement that they feel it was beneficial to get the device; and one third have no improvement in their seizures. VNS therapy typically doesn’t provide immediate control; it can take weeks or months to see a response. A one-year trial of the device is reasonable for determining the level of benefit it will provide. To date, VNS effectiveness seems to continue over time.
What Are the Risks and Side Effects of a VNS?
Implanting a VNS has very few side effects. General risks are the same as those associated with all surgical procedures, including infection, bleeding or reactions to anesthesia. These complications are rare. Hoarseness and throat pain when the stimulation is active are the most commonly reported side effects.
