Ictal-interictal single photon emission computed tomography with coregistration to magnetic resonance imaging (SISCOM) hyperperfusion, in addition to invasive electroencephalogram, provides clues in terms of epilepsy lateralization, according to a study published in Seizure.

A total of 67 patients who underwent surgical resection at the Cleveland Clinic Epilepsy Center in Ohio, and who had a presurgical SISCOM evaluation, were enrolled. All patients were seizure free for at least 1 year after their surgical resection procedure. Blinded and independent neurologists reviewed the SISCOM analyses for localization of basal ganglia (BG), thalamic (TN), and cerebellar (CH) hyperperfusion.

The investigators compared subcortical activation, or an increased ictal uptake vs the interictal uptake, and epilepsy characteristics between patients. In addition, the researchers calculated the specificity, sensitivity, and positive and negative predictive value for correct lateralization of the epilepsy side for each region of interest.

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The range of the proportion of patients with BG hyperperfusion, TN hyperperfusion, and CH hyperperfusion were 37.3% to 73.9%, 31.3% to 68.1%, and 13.5% to 29%, respectively. Compared with nonmotor seizures, there was a significant difference with BG and TN coactivation in terms of seizures with elementary motor signs (P =.016) and automatisms (P =.015).

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In addition, a significant difference was found with TN activation and patients with elementary motor signs vs nonmotor seizures (P =.016). The most optimal predictive positive value for correct lateralization of the epilepsy side for a threshold of 1.5 was with BG/CH coactivation in 89% of patients. Thresholds of 2.0 and 2.5 obtained BG/TN coactivation in 88% and BG activation in 82%, respectively.

Limitations of this study include its small sample size, recruitment of patients from a single center, and the lack of a healthy control group.

The researchers suggest that “to reach a good level of confidence, different thresholds and subcortical regions should now be analyzed” in future research.


Aupy J, Wongwiangjunt S, Wang ZI, Wu G, Alexopoulos A. Subcortical SISCOM hyperperfusion: Should we pay more attention to it? Seizure. 2018;62:43-48.