26 February 2015
While many patients’ seizure tendency subsides spontaneously or is well controlled on antiepileptic medication, one-third of all patients with epilepsy continue to have frequent seizures despite medical treatment. One increasingly established surgical option for treating such patients is vagus nerve stimulation (VNS).
Vagus nerve stimulation devices have been implanted worldwide. The procedure is not normally curative - patients usually continue to have seizures and to be on medication - but most studies report that around two-thirds of patients enjoy a major reduction in the frequency or severity of their attacks.
VNS works by sending electrical pulses along the vagus nerve in the neck on its route to the brain. When they reach the brain the pulses suppress the seizure activity that arises in certain brain areas. These pulses are delivered by an electrode surgically implanted in the neck and connected under the skin to a battery-powered generator like a heart pacemaker.
A general anaesthetic is required but the operation can be performed as a day case. Afterwards, regular clinic appointments are required to adjust the strength of stimulation to suit the individual patient. The implanted battery lasts around five years but can be replaced as a day case procedure under local anaesthetic.
We have found that the main advantage of VNS is that it potentially works for all seizure types and is generally well tolerated. It does not tend to cause the typical side effects of antiepileptic drugs, it results in no sedation and if anything tends to improve mood and suppress appetite.
The disadvantages are that it can cause intermittent hoarseness of the voice, which can normally be adjusted to a level that patients find tolerable, and is not as likely to be curative as other surgical treatments for epilepsy. However, these other treatments involve major brain surgery and are only suitable for patients with certain types of seizure.
With the inception of NHS England commissioning for specialist procedures, there are now clear criteria for suitability for VNS (Commissioning Policy: Vagal Nerve Stimulation - NHS Commissioning Board, April 2013). The typical patient has several seizures a month of a severity that impacts upon their lives in a major way.
Patients or their relatives interested in learning more about vagus nerve stimulation may discuss the matter with their neurologist who will know of the local UK centre that runs a VNS service.