Ictal brain hyperperfusion contralateral to seizure onset: the SPECT mirror image.
OBJECTIVE
Ictal single-photon emission computed tomography (SPECT) may help localize the seizure-onset zone (SOZ) by detecting changes in regional cerebral blood flow induced by epileptic discharges. This imaging method also reveals hyperperfusions in areas of seizure propagation, including the hemisphere contralateral to the SOZ. We have studied the occurrence, the topography, and the clinical value of such contralateral ictal hyperperfusion areas (HPAs).


METHODS
We examined data from presurgical evaluations of 36 consecutive patients with pharmacoresistant partial epilepsy of various localizations. Ictal and interictal SPECT examinations were made with 99mTc-ECD, and the scans were processed for coregistration, normalization, subtraction, and merging with MRI images.


RESULTS
Contralateral HPAs were observed in 72% of the patients: 50% of mesiotemporal epilepsy cases with hippocampal sclerosis, 85.7% of the other mesiotemporal epilepsies, 85.7% of neocortical lateral temporal epilepsies, and 87.5% of extratemporal epilepsies. Contralateral HPAs were usually symmetrical to the SOZ, forming a mirror image, observed in 57.1% of the patients. They could be slightly asymmetrical in mesiotemporal epilepsies, perhaps because of the particular anatomic pathways linking temporal lobes. In neocortical epilepsies, they were located in the cortex homotopic to the SOZ.


CONCLUSIONS
We show that the symmetrical nature of the mirror image usually does not disturb SPECT interpretation. It can confirm the location of the SOZ (11 patients) and even occasionally improve the precision of its definition (nine patients) by restraining several potential SOZ-related HPAs to a single one or by permitting a restricted localization of the SOZ in a large HPA.
Huberfeld
Gilles
G
Epileptology Unit, INSERM U739, Cortec & Epilepsie, Faculté de Médecine, Hopital Pitié Salpêtrière, Paris, France. gilles.huberfeld@chups.jussieu.fr
Habert
Marie-Odile
MO
Clemenceau
Stéphane
S
Maksud
Philippe
P
Baulac
Michel
M
Adam
Claude
C
D001921:Brain / Q000098:blood supply* / Q000000981:diagnostic imaging* / Q000601:surgery; D001931:Brain Mapping / Q000379:methods*; D003545:Cysteine / Q000031:analogs & derivatives; D004569:Electroencephalography / Q000379:methods; D004827:Epilepsy / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery; D004833:Epilepsy, Temporal Lobe / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery; D005500:Follow-Up Studies; D007839:Functional Laterality / Q000502:physiology*; D006624:Hippocampus / Q000473:pathology / Q000503:physiopathology; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000706:statistics & numerical data; D009434:Neural Pathways / Q000000981:diagnostic imaging / Q000503:physiopathology; D015609:Organotechnetium Compounds; D011300:Preoperative Care; D012039:Regional Blood Flow / Q000502:physiology; D012189:Retrospective Studies; D012598:Sclerosis; D012640:Seizures / Q000000981:diagnostic imaging*; D013702:Temporal Lobe / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods / Q000706:statistics & numerical data*; D014743:Videotape Recording
D015609:Organotechnetium Compounds; C059659:technetium Tc 99m bicisate; D003545:Cysteine