Neurology: New SPECT technique improves accuracy of epilepsy surgery

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A new technique, STATistical Ictal SPECT COregistered to MRI (STATISCOM) can accurately identify seizure localization before temporal lobe epilepsy (TLE) surgery and increase postsurgical seizure freedom in patients, according to the research published in the January issue of Neurology.

Subtraction Ictal SPECT COregistered to MRI (SISCOM), a tool for epilepsy surgery evaluation does not determine whether the ictal–interictal subtraction difference is statistically different from the expected random variation between two SPECT studies.

Elson So, MD, professor of neurology at the Mayo Clinic In Rochester, Minn., and colleagues developed a new statistical parametric mapping and MRI voxel-based method of analyzing ictal–interictal SPECT difference data, STATISCOM and compared it with SISCOM.

“About 10 percent of patients with epilepsy have very frequent seizures that are not controlled by medication and adversely affect their quality of life,” said So. “These patients should be evaluated for epilepsy surgery. In doing so, it is imperative that we can clearly and distinctively pinpoint seizure location in the brain.”

The investigators performed two serial SPECT studies in 11 healthy volunteers without epilepsy (control subjects). STATISCOM and SISCOM images from 87 consecutive patients who had ictal SPECT studies and subsequent temporal lobectomy were assessed by reviewers blinded to clinical data and outcome.

“STATISCOM correctly localized the TLE subtypes in 68 percent of patients compared with 24 percent by SISCOM; subgroup analysis of patients without lesions (as determined by MRI) showed superiority of STATISCOM (80 percent vs. 47 percent),” said So.

Moreover, the probability of seizure-free outcome was higher when STATISCOM correctly localized the TLE subtype than when it was indeterminate (81 percent vs. 53 percent), according to the researchers.

“If we are able to pinpoint seizure location with STATISCOM, and if that finding corresponds with the patient’s MRI and EEG studies, the likelihood of that patient benefiting from surgery is about twice greater than if the seizures cannot be localized with these means,” said So. “Thus, STATISCOM is a powerful tool that will help us improve surgical accuracy and increase the probability of seizure freedom in our patients.”