Epilepsy is the most common serious neurological condition in the UK. Up to 80% of people with epilepsy have their seizures controlled by anti epileptic drugs (AEDs) but this leaves 20% who still experience seizures. Brain surgery may be considered but this is only appropriate for a small number of people.
For the remainder, alternative therapies are needed and Vagus Nerve Stimulation has been suggested by some as a treatment. Although not yet universally recognised as a valid method of treatment for epilepsy, it has received a lot of interest in the UK.
WHAT IS VAGUS NERVE STIMULATION?
Vagus Nerve Stimulation (VNS) is, as the name implies, a mild electrical stimulation of a nerve called the vagus nerve which carries information to the brain. It has been suggested that this treatment can reduce seizure frequency in some people with epilepsy.
HOW DOES VNS WORK?
The Vagus Nerve is one of the many nerves carrying messages to and from the brain. It is thought that the nerve fibres in the vagus nerve, which carry information from the organs of the body to the brain are connected to areas of the brain believed to be involved in producing seizures. Epileptic seizures are caused by normally well-organised brain waves becoming completely disorganised. It has been suggested that stimulation of the vagus nerve may be able to intercept this abnormal brain activity.
HOW IS THE VAGUS NERVE STIMULATED?
A small generator, rather like a pacemaker, sends a pattern of stimulation to the vagus nerve through a special lead. The generator and the lead are implanted during an operation under general anaesthetic usually lasting between one and two hours. The generator is placed under the skin in the upper left chest and the lead is attached to the left vagus nerve in the lower left side of the neck. The generator can be programmed with different frequencies of stimulation chosen by the doctor to meet the needs of the individual. The generator is powered by a single battery, which usually lasts between 36 and 60 months. When the battery is depleted the generator has to be removed and replaced with a new one.
DOES THE INDIVIDUAL THEMSELVES HAVE ANY CONTROL OVER THE STIMULATION PATTERN?
Some people with epilepsy experience an aura before the epileptic seizure occurs (which is in fact the start of the seizure) and in these instances a special magnet can be used to manually activate the generator. By passing the magnet over the generator a burst of stimulation is sent to the vagus nerve which in some instances may prevent the seizure developing any further.
ARE THERE ANY SIDE EFFECTS?
VNS is still a fairly new form of treatment and as yet the long-term profile of side effects has not been established. Acutely, when the vagus nerve is actually being stimulated, most people complain of a tingling in the neck or hoarseness. Some have reported throat pain, ear pain or tooth pain and sometimes a choking sensation. Having the intensity or duration of the stimulation adjusted by the doctor may lessen these sensations in some patients. For those people who have a high intensity stimulation these symptoms may exist continually, not solely when the nerve is being stimulated; however, they should disappear when the intensity is adjusted. Very high intensity stimulation may cause vomiting and nausea but again this should cease when the intensity has been reduced.
HOW SUCCESSFUL IS THIS FORM OF TREATMENT?
As yet only a small number of people have been treated by this method and of these only a few have achieved a significant decrease in seizure frequency. Only as more people try out this alternative treatment and only when more research is carried out will we know what place it holds in the treatment of epilepsy.