EEG-triggered functional MRI of interictal epileptiform activity in patients with partial seizures

EEG-triggered functional MRI (fMRI) offers the potential to localize the ge nerators of scalp EEG events, such as interictal epileptiform discharges, u sing a biological measurement as opposed to relying solely on modelling tec hniques. Although recent studies have demonstrated these possibilities in a small number of patients, wider application has been limited by concerns a bout patient safety, severe problems due to pulse-related artefact obscurin g the EEG trace, and lack of reproducibility data. We have systematically s tudied and resolved the issues of patient safety and pulse artefact and now report the application of the technique in 24 experiments in 10 consecutiv e patients with localization-related epilepsy and frequent interictal epile ptiform discharges (spikes or spike wave), At least two experiments were pe rformed for each patient, In each experiment, 10- or 20-slice snapshot grad ient-echo planar images were acquired similar to 3.5 s after a single typic al epileptiform discharge (activation image) and in the absence of discharg es (control image). Between 21 and 50 epileptiform discharges were sampled in each experiment, The significance of functional activation was tested us ing the t test at 95% confidence on a pixel-by-pixel basis, Six of the 10 p atients showed reproducible focal changes of the blood oxygen level-depende nt (BOLD) signal, which occurred in close spatial relationship to the maxim um of the epileptiform discharges in the concurrent EEG. No reproducible fo cal BOLD signal changes were observed in the remaining four patients, In co nclusion, LEG-triggered fMRI is now a sufficiently developed technique to b e more widely used in clinical studies, demonstrating that it can reproduci bly localize the brain areas involved in the generation of spikes and spike wave in epilepsy patients with frequent interictal discharges.