title: BOLD signal increase preceeds EEG spike activity--a dynamic penicillin induced focal epilepsy in deep anesthesia.
abstract: In 40-60% of cases with interictal activity in EEG, fMRI cannot locate any focus or foci with simultaneous EEG/fMRI. In experimental focal epilepsy, a priori knowledge exists of the location of the epileptogenic area. This study aimed to develop and to test an experimental focal epilepsy model, which includes dynamic induction of epileptic activity, simultaneous EEG/fMRI, and deep anesthesia. Reported results are from seven pigs (23 +/- 2 kg) studied under isoflurane anesthesia (1.2-1.6 MAC, burst-suppression EEG) and muscle relaxant. Hypo- and hypercapnia were tested in one pig. Penicillin (6000 IU) was injected via a plastic catheter (inserted into the somatosensory cortex) during fMRI (GRE-EPI, TE = 40 ms, 300 ms/two slices, acquisition delay 1700 ms) in 1.5 T (N = 6). Epileptic spikes between acquisition artifacts were reviewed and EEG total power calculated. Cross-correlation between voxel time series and three model functions resembling induced spike activity were tested. Activation map averages were calculated. Development of penicillin induced focal epileptic activity was associated with linear increase and saturation up to approximately 10-20%, in BOLD activation map average. Its initial linear increase reached 2.5-10% at the appearance of the first distinguished spike in ipsilateral EEG in all six animals. Correlated voxels were located mainly in the vicinity of the penicillin injection site and midline, but few in the thalamus. In conclusion, development of focal epileptic activity can be detected as a BOLD signal change, even preceding the spike activity in scalp EEG. This experimental model contains potential for development and testing different localization methods and revealing the characteristic time sequence of epileptic activity with fMRI during deep anesthesia.
authors: Department of Diagnostic Radiology, University of Oulu, Kajaanintie 50, 90220 Oulu, Finland. Minna.Makiranta@oulu.fi
authors: Minna
authors: M
authors: Mäkiranta
authors: Jyrki
authors: J
authors: Ruohonen
authors: Kalervo
authors: K
authors: Suominen
authors: Jaakko
authors: J
authors: Niinimäki
authors: Eila
authors: E
authors: Sonkajärvi
authors: Vesa
authors: V
authors: Kiviniemi
authors: Tapio
authors: T
authors: Seppänen
authors: Seppo
authors: S
authors: Alahuhta
authors: Ville
authors: V
authors: Jäntti
authors: Osmo
authors: O
authors: Tervonen
mesh_terms: D000758:Anesthesia; D000818:Animals; D001931:Brain Mapping; D002560:Cerebrovascular Circulation / Q000187:drug effects / Q000502:physiology; D004569:Electroencephalography; D004828:Epilepsies, Partial / Q000139:chemically induced / Q000503:physiopathology*; D005260:Female; D006439:Hemodynamics / Q000502:physiology; D006935:Hypercapnia / Q000503:physiopathology; D008279:Magnetic Resonance Imaging; D010100:Oxygen / Q000097:blood*; D010406:Penicillins / Q000633:toxicity*; D013552:Swine
chemical_list: D010406:Penicillins; D010100:Oxygen