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Localizing value of ictal-interictal SPECT analyzed by SPM (ISAS).
Kelly A McNally1, A LeBron Paige, George Varghese
1Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06520-8018, USA.
Epilepsia
|September 9, 2005
Summary
Ictal single-photon emission computed tomography (SPECT) accurately localizes epilepsy seizure onset regions. This method, ictal-interictal SPECT analyzed by SPM (ISAS), is reliable even with late injections, unlike postictal SPECT.
Area of Science:
- Neuroscience
- Radiology
- Epileptology
Background:
- Neuroimaging aims to pinpoint epilepsy seizure onset zones.
- Single-photon emission computed tomography (SPECT) during seizures (ictal SPECT) shows promise for localization.
- Interpreting late or postictal SPECT scans remains challenging due to potential changes in multiple brain regions.
Purpose of the Study:
- To develop and validate an objective, widely available method for interpreting ambiguous ictal and postictal SPECT scans in epilepsy.
- To assess the utility of Statistical Parametric Mapping (SPM) for analyzing SPECT data to localize seizure onset.
- To compare the efficacy of ictal versus postictal SPECT for precise seizure localization.
Main Methods:
- Forty-seven epilepsy cases underwent ictal or postictal SPECT using [99mTc]-HMPAO, with images compared to interictal scans.
- A novel method, ictal-interictal SPECT analyzed by SPM (ISAS), was employed using freely available software and normal SPECT databases.
- SPM statistically analyzed difference images to identify a single region of seizure onset.
Main Results:
- Ictal SPECT, analyzed with ISAS, successfully identified a single, unambiguous seizure onset region in 71% of mesial temporal and 83% of neocortical epilepsy cases, with 100% accuracy.
- Postictal SPECT, even with early injections, showed poor single-region localization due to widespread perfusion changes.
- However, postictal SPECT could lateralize seizure onset to the correct hemisphere in approximately 80% of cases by assessing overall decreased perfusion.
Conclusions:
- The ictal-interictal SPECT analyzed by SPM (ISAS) method is validated, readily available, and effective for epilepsy SPECT analysis and interpretation.
- The findings underscore the importance of obtaining SPECT injections precisely during seizures for unambiguous localization.
- ISAS offers an objective approach to interpreting SPECT scans, aiding in the precise localization of epilepsy foci.