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Vagus nerve stimulation
About vagus nerve stimulation (VNS) therapy for epilepsy
Vagus nerve stimulation therapy is a treatment for patients whose epilepsy is difficult to control. The treatment involves an operation and can result in patients gaining more control over their seizures.
Approximately 60% of patients on vagus nerve stimulation therapy experience fewer seizures or attacks of significantly shorter duration or reduced severity. Between 30% and 40% of these patients achieve at least 50% reduction in their number of seizures. However it must be stated that approximately 40% of patients undergoing vagus nerve stimulation therapy gain no benefit whatsoever.
How does vagus nerve stimulation therapy work?
The vagus nerve is one of 12 main nerves that connects the brain to other structures in the body. One of its functions is to control speech and swallowing. It so happens that the part of the brain from which the vagus nerve arises is thought to be involved in producing the uncontrolled electrical discharges that result in seizures.
Research has shown that if small electrical pulses are applied to the vagus nerve to travel backwards into the brain, such pulses may stop or disrupt seizure-related discharges. As the pulses may also affect speech and swallowing by travelling forwards along the vagus nerve, they are delivered not continuously but in bursts of a few seconds separated by longer intervals. The bursts are nevertheless frequent enough to reduce the build-up of seizure activity. If a seizure has already started, the patient or relative can also hold a magnet on the skin over the stimulator device to deliver a longer more powerful burst of stimulation which may abort the seizure.
Potential benefits of vagus nerve stimulation therapy
The following list highlights the reported benefits from vagus nerve stimulation. However, not all patients may experience the same benefits. Some patients may not experience a change in their seizure frequency, but may have shorter duration attacks and a quicker recovery.
- It can reduce the number of seizures
- It can reduce the duration and severity of a seizure
- It can reduce the time it takes to recover from a seizure
- It is relatively safe and has been used in over 16,000 patients worldwide
- It is non pharmacological (does not involve taking medication) and therefore does not have drug side effects such as tiredness.
- Patients may feel less depressed and brighter
- It is easy to use
Procedures and equipment involved in vagus nerve stimulator implantation
Patients with epilepsy considered potentially suitable for vagus nerve stimulation are normally referred by their epilepsy specialist to the Neurostimulator Clinic. Such patients require extensive investigation to confirm the nature of their seizures, to check that their seizures are of a severity likely to benefit from vagus nerve stimulation and to check that there is not some alternative surgical treatment that would be more suitable in certain cases.
The surgery is performed under general anaesthetic and involves a small incision at the left side of the neck to allow the electrode to be attached to the left vagus nerve.
A second incision is made usually just below the left collar bone where the pulse generator (battery) sits underneath the skin. The electrode is then connected to the pulse generator and switched on to its lowest setting (this is too low for the patient to feel or to be effective and is simply to ensure everything is working correctly).
For more details about the surgery and programming of the vagus nerve stimulation, please click here - this link will take you to another website about VNS therapy.
Programming the vagus nerve stimulator
Click here for information about how the device is programmed.
Frequently asked questions
Please click here to find out answers to your questions about vagal nerve stimulation.
