The left and right vagus nerves are part of the autonomic nervous system, which regulates a number of functions that are not under voluntary control, e.g. heart rate, breathing rate and digestion. In recent years, stimulation of the left vagus nerve (known as vagus nerve stimulation, or VNS) has successfully been used as an alternative/additional treatment for certain people who are resistant to anti-epileptic drugs (AEDs). VNS is administered using a device implanted under the skin of the left-hand-side of the chest, with a wire that runs to the nerve where it passes through the neck. The device is then set to give bursts of electrical stimulation to the nerve at regular time intervals.

Scientists believe that VNS might be more effective if it could be administered on-demand, just before the onset of a seizure, rather than at standard time intervals. However, this would require a piece of equipment that either predicts seizures or detects them very early, and this currently doesn't exist. Researchers at Aalborg University, in Denmark, have been exploring whether the electrical behaviour of the left vagus nerve (recorded using a vagal electoneurogram (VENG)), relative to heart activity, can be used to indicate impending seizure activity.

The group used 14 anaesthetised animal models for the study. Six were treated with a simple saline solution (and served as controls), whilst the remaining eight received a convulsant known as pentylenetetrazol (PTZ). Using complex analysis of the VENG recordings, a cardiac-related vagus electroneurogram (CrVENG) profile was produced for each model. Changes in these profiles were taken as indicators of seizure activity.

Using this method, the researchers successfully detected seizures in all of the PTZ-treated models, before they developed tonic seizures. The controls did not develop seizures, and thus no seizures were detected in these animals.

These results suggest that is indeed possible to detect seizures early using CrVENG in anaesthetised animals. The next step will be to evaluate the method in awake, freely moving animals, and eventually in humans. If successful, a device that detects CrVENG changes and administers VNS accordingly could be developed to treat epilepsy in the future.

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Seizure prediction is a large area of epilepsy research, and scientists the world over are trying to identify the precise events in the brain that lead to a seizure. A detectable, recordable pre-seizure ('preictal) state would have enormous implications for seizure prevention therapy.

On 23-24 September 2010, Epilepsy Research UK held its eighth international expert workshop, entitled 'Preictal Phenomena', in Oxford. Forty-five researchers from the US, Europe and Asia came together for two days to share their ideas about the events that take place in the brain just prior to a seizure.

The event was a resounding success with discussions flowing freely; but the number of different ideas raised highlighted just how complex epilepsy is and how much work there is to be done before a definitive pre-seizure state is identified.

The presentations and discussions from the workshop are now being written up for inclusion in a special edition of the journal Epilepsy Research. We anticipate that this will be published in March/April 2011.