Imaging of cortical spreading depression by EIT: implications for localization of epileptic foci

Abstract

Severe epileptics may require curative neurosurgery. Sometimes focus localization requires recording with electrodes inserted deep into the brain, which may cause death or permanent neurological damage. Since epileptic seizures are associated with marked changes in cerebral impedance, we propose that EIT with sub-dural electrodes (inserted between the brain and skull) could provide a superior and less dangerous method for the localization of epileptic foci. The purpose of these experiments was to determine whether EIT could be used to localize the origin of seizure activity. In terms of impedance characteristics, an appropriate model is cortical spreading depression in the animal brain. Six rabbits were anaesthetized and paralysed and the brain exposed. EIT images and DC potentials were recorded from an array of 16 electrodes on the brain during cortical spreading depression induced by DC stimulus. Cortical spreading depression could be localized by EIT with an accuracy of 8.7% +/- 6.4% (mean +/- SD) of electrode array diameter. The errors in localization appeared to be distributed randomly. In a phantom of similar geometry, the error was 5% after correction for a systematic component. Results are sufficiently encouraging that we intend to extend this study to human patients.

Determination of Optimal Parameters and Feasibility for Imaging of Epileptic Seizures by Electrical Impedance Tomography: A Modelling Study Using a Realistic Finite Element Model of the Head

“…Impedance changes during spreading depression (SD) were therefore considered to integrate these data. SD has already been used as a model for epilepsy since it has similar impedance characteristics (Boone et al, 1994) and probably is due to the same cell processes (Leao, 1944). The real and imaginary component of the resistivity have been measured separately in anesthetized rabbits during SD at frequencies between 5Hz and 50kHz (Ranck Jr, 1964).…”

Real-time imaging of cerebral infarction in rabbits using electrical impedance tomography

“…EIT has the potential to provide a uniquely useful new imaging method in clinical or experimental neuroscience, 4 enabling the imaging of epileptic seizures 5 and bloodflow changes during cortical evoked activity 6 in humans, and of cortical spreading depression 7,8 and fast neuronal depolarization 9,10 in anaesthetized animals. Furthermore, its noninvasiveness and the fact that it does not involve ionizing radiation make EIT a potential method of continuous monitoring.…”

Use of 3-D magnetic resonance electrical impedance tomography in detecting human cerebral stroke: a simulation study

“…Classical examples are the visual and auditory stimulations, migraines, strokes and epilepsy (Boone et al, 1994;Holder et al, 1999;Sadleir and Fox, 2001;Towers et al, 2000). Although the effects of these conditions vary in their magnitude and duration, each one tends to affect a particular area of the brain.…”