Ictal single photon emission computed tomography in epileptic auras

Area of Science:

• Neuroscience
• Epileptology
• Medical Imaging

Background:

• Accurate localization of the epileptogenic zone (EZ) is crucial for successful epilepsy surgery.
• Ictal single photon emission computed tomography (SPECT) is a tool used to identify hyperperfusion associated with seizures.
• The utility of ictal SPECT during isolated epileptic auras remains unclear.

Purpose of the Study:

• To evaluate the diagnostic yield of ictal SPECT injections performed during isolated epileptic auras.
• To determine if ictal SPECT can reliably localize the epileptogenic zone (EZ) in patients with focal epilepsy experiencing isolated auras.

Main Methods:

• Retrospective analysis of 26 ictal SPECT studies from 20 patients with focal epilepsy during isolated auras.
• Ictal interictal subtraction SPECT coregistered to MRI (SISCOM) was performed.
• Two blinded readers assessed images for hyperperfusion, lateralization, and localization, with results correlated to EZ localization, injection timing, and EEG findings.

Main Results:

• A dominant hyperperfusion area was identified in 53% of injections, with poor interobserver agreement (κ = 0.128).
• Correct lateralization to the EZ occurred in 35% of injections (κ = 0.46), but correct localization was achieved in only one patient (κ = 0.146).
• No significant differences were observed between temporal and extratemporal cases, nor was injection timing or ictal EEG change predictive of successful localization.

Conclusions:

• Ictal SPECT during isolated epileptic auras has a low yield for accurately localizing the epileptogenic zone (EZ).
• This method alone is insufficient for presurgical evaluation in such cases.
• Repeat ictal SPECT injections during seizures with clinical manifestations and concurrent EEG are recommended for improved diagnostic accuracy.