Biomedical Engineering Reference
In-Depth Information
Chapter 9
Functional Neuroimaging of Spike-Wave Seizures
Joshua E. Motelow and Hal Blumenfeld
Abstract
Generalized spike-wave seizures are typically brief events associated with dynamic changes in brain phys-
iology, metabolism, and behavior. Functional magnetic resonance imaging (fMRI) provides a relatively
high spatiotemporal resolution method for imaging cortical-subcortical network activity during spike-
wave seizures. Patients with spike-wave seizures often have episodes of staring and unresponsiveness
which interfere with normal behavior. Results from human fMRI studies suggest that spike-wave seizures
disrupt specific networks in the thalamus and frontoparietal association cortex which are critical for nor-
mal attentive consciousness. However, the neuronal activity underlying imaging changes seen during
fMRI is not well understood, particularly in abnormal conditions such as seizures. Animal models have
begun to provide important fundamental insights into the neuronal basis for fMRI changes during spike-
wave activity. Work from these models including both fMRI and direct neuronal recordings suggest
that, in humans, specific cortical-subcortical networks are involved in spike-wave, while other regions are
spared. Regions showing fMRI increases demonstrate correlated increases in neuronal activity in animal
models. The mechanisms of fMRI decreases in spike-wave will require further investigation. A better
understanding of the specific brain regions involved in generating spike-wave seizures may help guide
efforts to develop targeted therapies aimed at preventing or reversing abnormal excitability in these brain
regions, ultimately leading to a cure for this disorder.
Key words:
Epilepsy, absence seizures, petit mal, fMRI, BOLD, EEG, rat, WAG/Rij, barrel cortex,
thalamus, laser Doppler flowmetry, cerebral blood flow, CBF.
1. Introduction
The study of epilepsy can shed light on both normal and
abnormal brain physiology. Generalized epileptic events such as
absence seizures, with their characteristic spike-and-wave dis-
charge (SWD), create transient and heterogeneous changes in
neural activity throughout the brain. Dynamic functional imag-
ing, with adequate temporal and spatial resolution, is an optimal
