When localization of the epileptic focus is uncertain, the epileptic activity generator may be more accurately identified with noninvasive imaging techniques which could also serve to guide stereo-electroencephalography electrode implantation. Since arterial spin labeling (ASL) has been demonstrated to be useful for the characterization of different diseases,1 it should be expected to detect perfusion changes related to the epileptic phenomena2 as well, with advantages over nuclear medicine protocols. The aim was to assess the diagnostic value of perfusion MRI with ASL in the identification of the epileptogenic zone, as compared with the results obtained with more established imaging tools. A good agreement between the ASL data and those from other investigation methods, including PET, electrical source imaging (ESI), and electrophysiological data, could provide evidence for its flexible utility in clinical assessment protocols for epilepsy. In 6 patients with drug-resistant focal epilepsy, standard video-EEG was performed to identify clinical seizure semeiology, and high-density EEG, ASL, and FDG-PET to noninvasively localize the epileptic focus. A standardized source imaging procedure, low-resolution brain electromagnetic tomography constrained to the individual matter, was applied to the averaged spikes of high-density EEG.3 Quantification of cerebral blood flow (CBF) maps from the ASL data was performed using the Buxton equation4 and statis- tically compared with a CBF template based on a group of 17 healthy subjects, while the standardized uptake value (SUV), a PET quantifier, was calculated as the ratio of tissue radioactiv- ity concentration at time t and injected dose, divided by body weight. The regions of interest identified using the Harvard- Oxford Atlas were used to calculate the mean values for current density (CD), CBF, and SUV in the same areas. In most of the patients, source in the interictal phase was associated with an area of hypoperfusion and hypometabolism. Conversely, in the patients presenting with early postictal discharges, the brain area identified by ESI as the generating zone appeared to be hyperperfused. The investigation allowed us to correctly identify the epileptogenic zone in 2 patients, in whom the results were confirmed by surgical resection and subsequent seizure freedom, 2 patients were excluded as surgery candidates, while the remaining 2 patients are waiting to be operated. As an innovative and more comprehensive approach to the study of epilepsy, the combined use of ESI, perfusion MRI, and PET may play an increasingly important role in the non-invasive evaluation of patients with refractory focal epilepsy. References 1. Alsop DC, Dai W, Grossman M, Detre JA. Arterial spin label- ing blood flow MRI: its role in the early characterization of Alzheimer’s disease. J Alzheimers Dis. 2010;20:871-880. 2. Altrichter S, Pendse N, Wissmeyer M, et al. Arterial spin-labeling demonstrates ictal cortical hyperperfusion in epilepsy secondary to hemimegalencephaly. J Neuroradiol. 2009;36:303-305. 3. Michel CM, Murray MM, Lantz G, Gonzalez S, Spinelli L, Grave de Peralta R. EEG source imaging. Clin Neurophysiol. 2004;115:2195-2222. 4. Buxton RB, Frank LR, Wong EC, Siewert B, Warach S, Edelman RR. A general kinetic model for quantitative perfu- sion imaging with arterial spin labeling. Magn Reson Med. 1998;40:383-396.
|Titolo:||Combining ESI, ASL and PET for quantitative assessment of drug-resistant focal epilepsy|
|Data di pubblicazione:||2013|
|Appare nelle tipologie:||04.02 Abstract in Atti di convegno|