Continuous, Simultaneous EEG and Event-Related Functional MRI of Epileptiform Discharges: A Powerful New Alternative to Spike-Triggered fMRI.
Abstract number :
1.194
Submission category :
Year :
2000
Submission ID :
3177
Source :
www.aesnet.org
Presentation date :
12/2/2000 12:00:00 AM
Published date :
Dec 1, 2000, 06:00 AM
Authors :
Louis Lemieux, Afraim Salek-Haddadi, Karsten Krakow, Philip Allen, Oliver Jospehs, Catherine A Scott, David R Fish, Institute of Neurology, London, United Kingdom; National Hosp for Neurology and Neurosurgery, London, United Kingdom.
RATIONALE: Studies of interictal events with EEG-triggered functional MRI (EEG/fMRI) have provided a non-invasive means of studying and localizing neural activity underlying EEG events. We have performed over 56 such experiments in 39 patients with frequent focal interictal spikes but EEG obliteration during image acquisition has limited such studies. A new method for continuous, simultaneous EEG and event-related fMRI acquisition with significant practical and methodological advantages has been developed. METHODS: EEG was monitored online with pulse artefact subtraction. Spike-triggered fMRI was used to acquire blood oxygen level dependent weighted images using gradient echo-plannar sequences. Volumes were acquired either post spike or at rest. In the second method, fMRI volumes were acquired continuously for up to 30 minutes. EEG was sampled simultaneously with on-line imaging and pulse artefact removal based on subtraction of running averages. Interictal discharges were identified and classified retrospectively and an event-related fMRI approach was used to analyze the data giving the spatio-temporal pattern of activation. RESULTS: Using spike-triggered fMRI significant focal concordant activations were demonstrated in approximately 50% of patients in whom spikes were recorded inside the scanner. In continuous EEG/fMRI, analysis of spike morphology and distribution confirmed lack of significant EEG distortion. Continuous EEG/fMRI also showed a well-defined activation consistent with previous EEG-triggered studies, scalp EEG and electrocorticography. The time course of activation was comparable in shape to normal brain activation. Variability in latency and undershoot amplitude was observed. CONCLUSIONS: Simultaneous and continuous EEG/fMRI acquisition combined with event-related fMRI is more flexible and powerful than the triggered approach. A wider range of patients with epilepsy can now be studied with EEG/fMRI. We anticipate that the new methodology will supersede current EEG/fMRI techniques and lead to important applications in many fields of neuroscience.