J Korean Neurol Assoc.  1997 Aug;15(4):762-774.

The Usefulness of Ictal SPECT in Preoperative Localization of Neocortical Epileptic Foci

• Bae HJ
• Nam HW
• Lee SK

Abstract

RATIONALE: Studies on ictal SPECT as a method of presurgical evaluation in neocortical epilepsy have been rare and inadequate. We evaluated the accuracy in the localization of epileptic foci with ictal SPECT in neocortical epilepsy and tried to find out the determining factors of its accuracy.
METHODS
We performed ictal SPECT 66 times with 99m-Tc-HMPAO in 56 patients, who received video-EEG monitoring and had electroclinical features of neocortical epilepsy. Invasive monitoring was performed in 28 patients & epileptic surgery was done in 31. Their results were also used to help determine the location of epileptic foci. In 54 of 66 scans data about injection time and temporal relationship of HMPAO injection to the onset and secondary generalization of seizures were available.
RESULTS
Frontal lobe epilepsy(FLE) was most common(35%) followed by lateral temporal lobe epilepsy(28%), occipital lobe epilepsy(11%), parietal lobe epilepsy(9%), and etc. Ictal SPECT demonstrated unilateral hyperperfusion in 53 of 66 scans (80.3 %) which were concordant with electroclinical lateralization in 48 of 53 (90.6 %). Localized hyperperfusion was evident in 42 of 66 scans (63.6 %) which were concordant with electroclinical localization in 33 of 42(78.6 %). Correctly localized hyperperfusion or correctly-lateralized but diffuse hyperperfusion were detected in 37 of 54 scans in which data about injection time were available. The mean injection time was 32.1 seconds. In 16 scans ictal SPECT showed no hyperperfusion or falsely localized/lateralized hyperperfusion. Their mean injection time was 41.6 seconds. The difference of injection time between two groups was not significant(p-value=0.07), but there was a tendency that the mean injection time of the former group was earlier than that of the latter group. We had chances to perform ictal SPECT repeatedly in 8 patients under the similar conditions. The fact that earlier injection improved the accuracy of ictal SPECT in 6 patients supports the importance of early injection. In 48 studies with ictal injection, only 11 scans gave no or incorrect information of the localization or lateralization of epileptic foci. But, in 6 studies with postictal injection, 5 scans was not helpful. The difference between two groups was statistically significant(p<0.05). The presence of focal lesion, the location of epileptic foci, or secondary generalization did not influence the accuracy of ictal SPECT.
CONCLUSIONS
Our data suggest that ictal SPECT in neocortical epilepsy is useful in localization of epileptic foci. Whether injected ictally or postictally and the injection time from seizure onset seems to influence the accuracy of ictal SPECT in neocortical epilepsy.

MeSH Terms

Epilepsy
Frontal Lobe
Generalization (Psychology)
Humans
Occipital Lobe
Parietal Lobe
Seizures
Technetium Tc 99m Exametazime
Temporal Lobe
Tomography, Emission-Computed, Single-Photon*
Technetium Tc 99m Exametazime