Surgical strategy for refractory epilepsy secondary to porencephaly: ictal SPECT may obviate the need for intracranial electroencephalography. Patient series

BACKGROUND Surgical treatment of intractable epilepsy caused by porencephaly can be difficult because of poorly localizing or lateralizing electroclinical findings. The authors aimed to determine whether noninvasive evaluations are sufficient in these patients. OBSERVATIONS Eleven patients were included in this study. The porencephalic cyst was in the left middle cerebral artery (MCA) area in 9 patients, the left posterior cerebral artery area in 1 patient, and the bilateral MCA area in 1 patient. Interictal electroencephalography (EEG) revealed multiregional, bilateral, interictal epileptiform discharges in 5 of 11 patients. In 6 of 10 patients whose seizures were recorded, the ictal EEG was nonlateralizing. Nine patients underwent ictal single-photon emission computed tomography (SPECT), which revealed lateralized hyperperfusion in 8 of 9 cases. Fluorodeoxyglucose positron emission tomography (FDG-PET) was useful for identifying the functional deficit zone. No patient had intracranial EEG. The procedure performed was hemispherotomy in 7 patients, posterior quadrant disconnection in 3 patients, and occipital disconnection in 1 patient. A favorable seizure outcome was achieved in 10 of 11 patients without the onset of new neurological deficits. LESSONS Ictal SPECT was useful for confirming the side of seizure origin when electroclinical findings were inconclusive. Thorough noninvasive evaluations, including FDG-PET and ictal SPECT, enabled curative surgery without intracranial EEG. Seizure and functional outcomes were favorable.

How to Inject Ictal SPECT? From Manual to Automated Injection

BackgroundSuccessful surgery depends on the accurate localization of epileptogenic zone before surgery. Ictal SPECT is the only imaging modality that allows identification of the ictal onset zone by measuring the regional cerebral blood flow at the time of injection. The main limitations of ictal SPECT in epilepsy are the complex methodology of the tracer injection during a seizure. To overcome these limitations, we present the main features of the first automated injector for ictal SPECT (epijet, LemerPax; La Chapelle -sur-Erdre; France). In this study we compared traditional manual injection with automated injection for ictal SPECT in122 patients with drug-resistant epilepsy. MethodsThe study included 55 consecutive prospective patients with drug-resistant epilepsy undergoing injection with the automated injector. The control group was our retrospective database of a historic pool of 67 patients, injected manually from 2014-2016. Calculated annual exposure/radioactive dose for operators was measured. Injection time, seizure focus localization with ictal SPECT, as well as repeated hospitalizations related to fails injections were compared in these two groups of patients. ResultsThere were no differences in the average injection time with epijet (13 s) compared with the traditional manual injection (14s). The seizure focus was successfully localized with ictal SPECT with epijet in 44/55 (80%) patients and with manual injection in 46/67 (68%) patients (p=0.694). Repeated studies were required in 16/67 (23%) patients in the manual injection group compared to 4 patients (7%) in the epijet group (p=0.022). Calculated annual exposure/dose for operators of 0.39 mSv/year and administered dose error inferior to 5% are other advantages of epijet. ConclusionThe first results using epijet are promising in adjustment of the injection dose, reducing the rate of radiation exposure for patients and nurses, maintaining the same injection time and allowing high SPECT accuracy. These preliminary results support the use of an automated injection system to inject radioactive ictal SPECT doses in epilepsy units.

Use of Innovative SPECT Techniques in the Presurgical Evaluation of Patients with Nonlesional Extratemporal Drug-Resistant Epilepsy

Up to 30% of patients with epilepsy may not respond to antiepileptic drugs. Patients with drug-resistant epilepsy (DRE) should undergo evaluation for seizure onset zone (SOZ) localization to consider surgical treatment. Cases of drug-resistant nonlesional extratemporal lobe epilepsy (ETLE) pose the biggest challenge in localizing the SOZ and require multiple noninvasive diagnostic investigations before planning the intracranial monitoring (ICM) or direct resection. Ictal Single Photon Emission Computed Tomography (i-SPECT) is a unique functional diagnostic tool that assesses the SOZ using the localized hyperperfusion that occurs early in the seizure. Subtraction ictal SPECT coregistered to MRI (SISCOM), statistical ictal SPECT coregistered to MRI (STATISCOM), and PET interictal subtracted ictal SPECT coregistered with MRI (PISCOM) are innovative SPECT methods for the determination of the SOZ. This article comprehensively reviews SPECT and sheds light on its vital role in the presurgical evaluation of the nonlesional extratemporal DRE.

Investigation of networks underlying hyperkinetic seizures utilizing ictal SPECT

ObjectiveTo study neural networks involved in hyperkinetic seizures (HKS) using ictal SPECT.MethodsWe retrospectively identified 18 patients with HKS evaluated at the Cleveland Clinic between 2005 and 2015 with video-EEG monitoring and ictal SPECT. Semiology was confirmed by the consensus of 2 epileptologists' independent reviews and classified as type 1, 2, or 3 HKS. SPECT data were analyzed by 2 independent physicians using a z score of 1.5. Ictal hyperperfusion patterns for each group were analyzed visually and with SPM. Spatial normalization to Montreal Neurological Institute space for each patient’s data was performed, followed by flipping of data from patients with left-sided ictal onset to the right side. Finally, an average z score map for each group was calculated.ResultsVisual analysis and SPM identified different patterns of ictal hyperperfusion in the 3 subtypes of HKS. Type 1 seizures showed hyperperfusion in a more anteriorly located network involving the anterior insula, orbitofrontal cortex, cingulate, and anterior perisylvian region and rostral midbrain. Type 2 seizures were associated with hyperperfusion in a more caudally located network involving the orbitofrontal cortex, cingulate (middle and posterior), basal ganglia, thalami, and cerebellum. Type 3 seizures showed a mixed pattern of SPECT hyperperfusion involving the temporal pole and anterior perisylvian region.ConclusionsEach of the 3 different semiologic subtypes of HKS is associated with distinct patterns of hyperperfusion, providing further insight into the neural networks involved. This knowledge may inform placement of invasive EEG electrodes in patients with HKS semiology undergoing presurgical evaluation.