Ictal SPECT With Intra-arterial Injection

Early Ictal SPECT With Intra-arterial Injection to Localize the Ictal Onset Zone in Refractory Focal Epilepsy.

Ictal SPECT with intravenous injection in a cubital vein of a perfusion tracer is an established technique to localize the ictal onset zone during presurgical evaluation of refractory focal epilepsy. When seizures last less than 10 seconds, localizing information is often not obtained. Since it takes around 30 seconds before the tracer reaches the brain after intravenous injection, ictal hyperperfusion most likely has already switched to postictal hypoperfusion. In this study, we plan to inject the perfusion tracer in the aorta proximal to the cerebral arteries, which will allow a true ictal injection in patients with seizures of short duration.

In this study, the investigators will select one patient with refractory focal epilepsy with frequent seizures of short duration, which can not be localized with early ictal SPECT with intravenous injection in a cubital vein. An arterial catheter will be inserted. The right groin will be disinfected using an alcoholic disinfectant and locally anaesthetized. The artery in the groin, the femoral artery, will be punctured. A catheter is inserted in the artery and slided towards the heart. To determine the correct position of the catheter proximal to the cerebral arteries, a contrast agent will be injected, and at the same time radiographs will be taken. The catheter will be attached and taped in the groin. The patient will be monitored with video-EEG recording. During an epileptic seizure, the perfusion tracer 99m-Technetium Ethyl Cysteinate Dimer (99mTc- ECD) dissolved in 30 cc normal saline will be injected with a pressure injector over 2 seconds. After injection, the catheter will be removed and the ictal SPECT scan will be performed. Subtracted ictal SPECT images co-registered with MRI (SISCOM) will be obtained. The investigators plan to do this study in one patient in order to assess whether this procedure is logistically possible and to determine whether subtraction images of ictal SPECT with intra-arterial injection minus interictal SPECT with intravenous injection allows localization of the ictal onset zone.

The perfusion tracer 99m-Technetium Ethyl Cysteinate Dimer will be injected via an intra-arterial catheter by a pressure injector to obtain a subtracted ictal SPECT co-registered with MRI (SISCOM)

seizure free outcome will be assessed 1 year after epilepsy surgery and correlated with Subtracted ictal SPECT co-registered with MRI (SISCOM) results

Inclusion Criteria: Refractory unifocal epilepsy Early ictal SPECT with intravenous injection did not localize the ictal onset zone Several seizure per day, or clusters of several seizures per day Seizures are of short duration (i.e. less than 10-15 seconds) Patient asks for epilepsy surgery Exclusion Criteria: Renal failure Allergy to contrast agents Fever Anemia Usage of anticoagulants Pregnancy

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