Localizing value of ictal-interictal SPECT analyzed by SPM (ISAS).
OBJECTIVE
The goal of neuroimaging in epilepsy is to localize the region of seizure onset. Single-photon emission computed tomography with tracer injection during seizures (ictal SPECT) is a promising tool for localizing seizures. However, much uncertainty exists about how to interpret late injections, or injections done after seizure end (postictal SPECT). A widely available and objective method is needed to interpret ambiguous ictal and postictal scans, with changes in multiple brain regions.


METHODS
Ictal or postictal SPECT scans were performed by using [99mTc]-labeled hexamethyl-propylene-amine-oxime (HMPAO), and images were analyzed by comparison with interictal scans for each patient. Forty-seven cases of localized epilepsy were studied. We used methods that can be implemented anywhere, based on freely downloadable software and normal SPECT databases (http://spect.yale.edu). Statistical parametric mapping (SPM) was used to localize a single region of seizure onset based on ictal (or postictal) versus interictal difference images for each patient. We refer to this method as ictal-interictal SPECT analyzed by SPM (ISAS).


RESULTS
With this approach, ictal SPECT identified a single unambiguous region of seizure onset in 71% of mesial temporal and 83% of neocortical epilepsy cases, even with late injections, and the localization was correct in all (100%) cases. Postictal SPECT, conversely, with injections performed soon after seizures, was very poor at localizing a single region based on either perfusion increases or decreases, often because changes were similar in multiple brain regions. However, measuring which hemisphere overall had more decreased perfusion with postictal SPECT, lateralized seizure onset to the correct side in approximately 80% of cases.


CONCLUSIONS
ISAS provides a validated and readily available method for epilepsy SPECT analysis and interpretation. The results also emphasize the need to obtain SPECT injections during seizures to achieve unambiguous localization.
McNally
Kelly A
KA
Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06520-8018, USA.
Paige
A LeBron
AL
Varghese
George
G
Zhang
Heping
H
Novotny
Edward J
EJ
Spencer
Susan S
SS
Zubal
I George
IG
Blumenfeld
Hal
H
D000293:Adolescent; D000328:Adult; D001931:Brain Mapping / Q000379:methods*; D004569:Electroencephalography / Q000706:statistics & numerical data; D004827:Epilepsy / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000601:surgery; D004833:Epilepsy, Temporal Lobe / Q000175:diagnosis / Q000000981:diagnostic imaging; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods* / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D019579:Neocortex / Q000000981:diagnostic imaging / Q000601:surgery; D011300:Preoperative Care; D012372:ROC Curve; D015203:Reproducibility of Results; D019690:Technetium Tc 99m Exametazime / Q000008:administration & dosage; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods* / Q000706:statistics & numerical data; D014743:Videotape Recording
D019690:Technetium Tc 99m Exametazime