Summary: Centromedian thalamic nucleus is an intralaminar nucleus with vast connectivity to cerebral cortex and basal ganglia. It receives afferents from the brain stem through the central tegmental tract and is part of the diffuse thalamic projection system. Because the reticulothalamic system has been related to initiation and propagation of epileptic activity (centroencephalic theory of epilepsy), deep brain stimulation has been proposed to interfere with seizure genesis or propagation. Centromedian thalamic nucleus is a large nucleus laying nearby the anatomical references for stereotaxis and therefore a convenient surgical target to approach. Electrodes are implanted in the anterior ventral lateral part of the nucleus (parvocellular area), guided by intraoperative recruiting responses elicited by unilateral 6 to 8 Hz electrical stimulation delivered through the deep brain stimulation electrode. Therapeutic stimulation is delivered with the following parameters: 60 Hz, 450 μs, 3.0 V. Seizure control runs between 69% and 83% in different reports, decreasing mainly generalized seizures from the start, with significant improvement in neuropsychological performance. Significant decrease in seizure occurs from hours to days after the onset of deep brain stimulation. Some reports refer that seizure improvement may occur by the simple insertion of the deep brain stimulation electrodes, and therefore, it was used to treat refractory epileptic status.
<b><i>Background:</i></b> Positron emission tomography (PET) imaging in epilepsy is an in vivo technique that allows the localization of a possible seizure onset zone (SOZ) during the interictal period. Stereo-electro-encephalography (SEEG) is the gold standard to define the SOZ. The objective of this research was to evaluate the accuracy of PET imaging in localizing the site of SOZ compared with SEEG. <b><i>Methods:</i></b> Seven patients with refractory temporal lobe epilepsy (Ep) and 2 healthy controls (HC) underwent 2 PET scans, one with 2-[<sup>18</sup>F]-fluoro-2-deoxy-D-glucose (FDG) and another with 2’-[<sup>18</sup>F]fluoroflumazenil (FFMZ), acquired 1 day apart. FDG was acquired for 10 min (static scan) 1 h after administration. An FFMZ scan was acquired for 60 min from radiopharmaceutical administration in a dynamic mode. Each brain PET image was segmented using a standard template implemented in PMOD 3.8. The pons was used as the reference region for modeling of the nondisplaceable binding potential (BP<sub>ND</sub>)<sub></sub>for FFMZ, and to obtain uptake ratios for FDG. SEEG studies of patients were performed as a part of their surgical evaluation to define the SOZ. <b><i>Results:</i></b> Well-defined differences between HC and Ep were found with both radiopharmaceuticals, showing the utility to identify abnormal brain regions using quantitative PET imaging. Lateralization of the SOZ findings by PET (lower uptake/binding in a specific brain hemisphere) matched in 86% for FFMZ and 71% for FDG with SEEG data. <b><i>Conclusion:</i></b> Quantitative PET imaging is an excellent complementary tool that matches reasonably well with SEEG to define SOZ in presurgical evaluation.
OBJECTIVE The authors sought to determine the antiseizure effects of deep brain stimulation (DBS) of the parahippocampal cortex (PHC) for treatment of drug-resistant mesial temporal lobe epilepsy (MTLE). METHODS After a 3-month baseline period, 6 adult patients with drug-resistant MTLE and hippocampal sclerosis (HS) had stereoelectroencephalography (SEEG)–DBS electrodes implanted at the PHC for identification of the seizure onset zone (SOZ). Patients entered an 8-month, randomized, double-blind protocol for DBS, followed by a 12-month open-phase study. Monthly reports of seizure frequency were collected, with separate counting of focal seizures with or without awareness impairment (focal impaired awareness seizures [FIAS] or focal aware seizures [FAS], respectively) and focal evolving to bilateral generalized tonic clonic seizures (GTCS). Stimulation parameters were 130 Hz, 450 μsec, 2.5–3 V, and cyclic stimulation 1 minute on/4 minutes off. RESULTS The total seizure rate decrement during follow-up was 41% (CI 25%–56%), with better seizure control for GTCS (IQR 19%–20%) and FIAS (IQR 0%–16%), with FAS being less responsive (IQR 67%–236%). No neuropsychological deterioration was observed. CONCLUSIONS PHC DBS induced important antiseizure effects in patients with incapacitating FIAS and GTCS, most likely through blocking the propagation of hippocampal-onset seizures. The PHC target can be easily and safely approached due to positioning away from vascular structures, and there was no evidence of DBS-induced cognitive deterioration.
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