Epilepsy Detection and Monitoring - Quantitative EEG Analysis Methods and Clinical Applications - page 141

CHAPTER 6
Epilepsy Detection and Monitoring

Nicholas K. Fisher, Sachin S. Talathi, Alex Cadotte, and Paul R. Carney

Epilepsy is one of the world's most common neurological diseases, affecting more
than 40 million people worldwide. Epilepsy's hallmark symptom, seizures, can have
a broad spectrum of debilitating medical and social consequences. Although
antiepileptic drugs have helped treat millions of patients, roughly a third of all
patients are unresponsive to pharmacological intervention.
As our understanding of this dynamic disease evolves, new possibilities for
treatment are emerging. An area of great interest is the development of devices that
incorporate algorithms capable of detecting early onset of seizures or even predict-
ing them hours before they occur. This lead time will allow for new types of
interventional treatment. In the near future a patient's seizure may be detected and
aborted before physical manifestations begin. In this chapter we discuss the algo-
rithms that will make these devices possible and how they have been implemented
to date. We investigate how wavelets, synchronization, Lyapunov exponents, prin-
cipal component analysis, and other techniques can help investigators extract infor-
mation about impending seizures. We also compare and contrast these measures,
and discuss their individual strengths and weaknesses. Finally, we illustrate how
these techniques can be brought together in a closed-loop seizure prevention system.

6.1 Epilepsy: Seizures, Causes, Classification, and Treatment

Epilepsy is a common chronic neurological disorder characterized by recurrent,
unprovoked seizures [1, 2]. Epilepsy is the most common neurological condition in
children and the third most common in adults after Alzheimer's and stroke. The
World Health Organization estimates that there are 40 to 50 million people with
epilepsy worldwide [3]. Seizures are transient epochs due to abnormal, excessive, or
synchronous neuronal activity in the brain [2]. Epilepsy is a generic term used to
define a family of seizure disorders. A person with recurring seizures is said to have
epilepsy. Currently there is no cure for epilepsy. Many patients' seizures can be con-
trolled, but not cured, with medication. Those resistant to the medication may
become candidates for surgical intervention. Not all epileptic syndromes are life-
long conditions; some forms are confined to particular stages of childhood. Epilepsy

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