Slow Cortical Potential Biofeedback & Epilepsy

Introduction 

Although perhaps not widely recognised, biofeedback training using Slow Cortical Potentials (SCP) can be a useful modality in the management of epilepsy. Until relatively recently, devices for SCP biofeedback were not commercially available. Now the NeXus range includes a high quality sensor as well as the DC-EEG amplifier technology to reliably capture and train with these signals as we will explain.

Connecting the SCP hardware with a NeXus 10 system

What is Epilepsy and how is it treated?

Epilepsy is a group of neurological conditions - often with unknown cause - characterised by recurrent seizures.  Approximately 600,000 people in the UK have a diagnosis of epilepsy and take anti-epileptic drugs. This is equivalent to approximately 1 in 103 people. The prevalence rate of epilepsy in the UK is approximately 9.7 per 1,000 or 0.97%.  

Studies suggest that one-fourth to one-third of new cases are considered drug-resistant or represent so called intractable epilepsy. They will have tried one or more drugs over a two year period and they are still experiencing seizures.  Although surgery might be an option, only about 12% of those with intractable epilepsy can be operated on for a variety of reasons. Overall it is suggested that 15-17% of persons with epilepsy can't be treated by standard interventions and become prime candidates for behavioural interventions.

Behavioural Interventions

In a behavioural medicine paradigm the epileptic seizures are conceived as behaviours that are influenced by their antecedents and their consequences. A neurological examination can be combined with a detailed "Seizure diary" that considers internal states, emotions, behaviours and cognitions as well as external events such as the behaviour of others. The aim is to increase self-awareness and knowledge about the early signs of seizure behaviour and to use a variety of training interventions to bring greater control into everyday life.

Slow Cortical Potentials?

Negative SCP’s appear in animals as well as humans before and during epileptic seizures

Slow Cortical Potentials represent a special type of signal that can be measured from the raw EEG.  These are very slowly changing, event-related, direct current shifts (baseline) of the electroencephalogram (DC-EEG) originating from the upper cortical layer.

They fact that these signals are very slow brain waves (lasting from 0.3 seconds up to several seconds) means that only a true DC-EEG amplifier can measure these. True DC-EEG means that there is no high-pass filter set at 1 Hz, 0.1 Hz or any lower frequency. The NeXus range of units has true DC-EEG amplifiers and there is no lower frequency limit.

The SCP signal can shift in either the positive direction or the negative direction. Negative SCP's appear in animals as well as humans before and during epileptic seizures which are followed by positive shifts after the seizures abate. This led to the hypothesis that epilepsy involves a deficit in regulating cortical hyperactivation.

The adoption of operant learning and behavioural principles have been used for some years now to develop a programme to control SCP's and hence teach patients to cope with seizures. SCP's are also relevant to ADHD and other conditions.

SCP Self Regulation

 The chart shows average negative and positive shifts over more than 50 trials. Negative shifts indicate cortical activation and positive shifts cortical de-activation

The chart shows average negative and positive shifts over more than 50 trials. Negative shifts indicate cortical activation and positive shifts cortical de-activation

NeXus Minicap is recommended for the SCP sensor

In using biofeedback the user learns over repeated trials to deliberately shift the SCP level.  In using a NeXus 10 or 32 system, typically the trainer will observe the EEG signal on one screen whilst the trainee will typically see an appropriate graphical feedback on a second screen. Strehl (2016) describes a protocol with three phases.  An initial 3 week period with one session per day is followed by an 8 week period of practice at home. This is followed by a further 2 weeks with daily sessions.

This biofeedback training is certainly not for beginners and trainers should be licensed psychologists qualified to conduct psychophysiological procedures.

For further information see

Ute Strehl  (2016)

"Biofeedback of Slow Cortical Potentials in Epilepsy"

in Biofeedback: A practitioners Guide. 4th Edition, Edited by MS Schwartz, F Andrasik. 2016 The Guilford Press

 

Derek JonesFixxl Ltd