Abstracts

Rationale: To evaluate the role of combined structural and functional imaging including EEG fMRI and functional mapping with fMRI to guide resections in focal epilepsy. Methods: Five patients with refractory focal epilepsy and frontal lobe lesions undergoing pre-surgical evaluation were studied with multi-modal imaging including EEG fMRI in the resting state at 3 Tesla, functional mapping with fMRI at 3 Tesla and FDG PET, prior to investigation with intracranial EEG.Results: In all cases, structural MRI revealed a lesion in the frontal cortex. In three patients, eloquent cortex mapped with fMRI was colocalised with IED-correlated BOLD signal change and four patients have undergone intracranial recording confirming eloquent cortex mapped with fMRI as well as the seizure onset zone. Case 1: MRI showed left frontal focal cortical dysplasia (FCD) anterior to the motor cortex mapped with motor fMRI. No interictal epileptiform discharges (IED) were recorded during EEG-fMRI. Invasive EEG monitoring and stimulation confirmed seizure onset in the FCD, anterior to motor cortex. Lesionectomy resulted in seizure control and no deficit. Case 2: MRI showed FCD in the right post-central gyrus adjacent to primary motor cortex mapped with fMRI. No IED were recorded during EEG-fMRI. Invasive EEG monitoring confirmed seizure onset in the FCD, but hip flexion on stimulation in the same location precluded resection. Case 3. MRI showed probable FCD in the left superior frontal gyrus with FDG PET hypometabolism in the same area. EEG-fMRI showed significant IED-correlated BOLD signal change bilaterally, posterior to primary motor cortex mapped on motor fMRI. Intracranial EEG recordings and stimulation are planned. Case 4. MRI revealed atrophy and FDG PET showed hypometabolism in the right frontal lobe. EEG fMRI showed significant IED-correlated BOLD signal activation in the right medial frontal gyrus. Motor fMRI mapped motor cortex to posterior to the IED-correlated clusters. Intracranial recording showed frequent IED in the same location as the IED-correlated clusters and a seizure onset zone involving the right medial frontal and prefrontal cortices. Case 5. MRI showed FCD in the left inferior frontal gyrus. EEG-fMRI showed significant IED correlated BOLD signal activation in the left superior temporal gyrus and left pre-central gyrus. Intracranial recording localised the seizure onset zone within the area of focal cortical dysplasia. Language areas mapped by fMRI did not colocalise with the seizure onset zone. Resection of the FCD was carried out, and seizures were reduced by 75%. Post-operative psychometry was unchanged. Conclusions: Multimodal structural and functional brain imaging provides useful data for planning intracranial EEG recordings and neocortical resections in focal epilepsy. (supported by UK Medical Research Council Grant no.G0306067)