Correlation of Ictal/Interictal SPECT subtraction with MEG and EEG

Objectives Neuroimaging is routinely used in the diagnosis and treatment of patients with epilepsy. In patients with refractory epilepsy neuroimaging and its data analysis play a crucial role in their clinical evaluation and surgical planning. We undertook a study to assess the correlation between SPECT, MEG, and EEG in four patients undergoing pre-surgical workup for refractory epilepsy.

Methods All patients pre-surgical workup included the following exams; SPECT ictal and interictal imaging with subtraction, MEG, and EEG. Subtraction SPECT scans were graded as lateralizing to hemispheres and/or localizing to lobe at 1, 2, or 3 standard deviations (SD). MEG was graded on convincing spikes with strong correlation with EEG, or localizing with or without EEG. Correlations between modalities were then determined to be strong, moderate or weak.

Results Where SPECT is positive at >2SD, there is high correlation with MEG and EEG. Where SPECT is positive a 1 SD, there is weak correlation with MEG and EEG. When SPECT is non-localizing, but appears to be hemispheric only, there is no correlation with MEG and EEG.

Conclusions Combined comparison of SPECT, MEG and EEG for the evaluation of patients with refractory epilepsy as part of their surgical workup can more convincingly localize an epileptogenic focus. Determining and defining correlations between SPECT, MEG and EEG may lead to more positive patient outcomes.