Jorge Gonzalez-Martinez

Evaluation of specific absorption rate as a dosimeter of MRI-related implant heating

To compare the magnetic resonance imaging (MRI)‐related heating per unit of whole body averaged specific absorption rate (SAR) of a conductive implant exposed to two different 1.5‐Tesla/64 MHz MR systems.

Hemispherectomy for catastrophic epilepsy in infants.

Summary:  Purpose: To report our experience with hemispherectomy in the treatment of catastrophic epilepsy in children younger than 2 years.

Stereoelectroencephalography in the "difficult to localize" refractory focal epilepsy: early experience from a North American epilepsy center.

Purpose:  Stereo‐electroencephalography (SEEG) enables precise recordings from deep cortical structures, multiple noncontiguous lobes, as well as bilateral explorations while avoiding large craniotomies. Despite a long reported successful record, its application in the United States has not been widely adopted. We report on our initial experience with the SEEG methodology in the extraoperative mapping of refractory focal epilepsy in patients who were not considered optimal surgical candidates for other methods of invasive monitoring. We focused on the applied surgical technique and its utility and efficacy in this subgroup of patients.

Ripple classification helps to localize the seizure-onset zone in neocortical epilepsy

Purpose:  Fast ripples are reported to be highly localizing to the epileptogenic or seizure‐onset zone (SOZ) but may not be readily found in neocortical epilepsy, whereas ripples are insufficiently localizing. Herein we classified interictal neocortical ripples by associated characteristics to identify a subtype that may help to localize the SOZ in neocortical epilepsy. We hypothesize that ripples associated with an interictal epileptiform discharge (IED) are more pathologic, since the IED is not a normal physiologic event.

Long-term seizure outcome after resective surgery in patients evaluated with intracranial electrodes.

Purpose:  Despite advances in “noninvasive” localization techniques, many patients with medically intractable epilepsy require the placement of subdural (subdural grid electrode, SDE) and/or depth electrodes for the identification and definition of extent of the epileptic region. This study investigates the trends in longitudinal seizure outcome and its predictors in this group.

Temporal patterns and mechanisms of epilepsy surgery failure

Epilepsy surgery is an accepted treatment option in patients with medically refractory focal epilepsy. Despite various advances in recording and localization noninvasive and invasive techniques (including electroencephalography (EEG), magnetic resonance imaging (MRI), positron emission tomography (PET), single photon emission computed tomography (SPECT), magnetoencephalography (MEG), subdural grids, depth electrodes, and so on), the seizure outcome following surgical resection remains suboptimal in a significant number of patients. The availability of long‐term outcome data on an increasing number of patients suggests two major temporal patterns of seizure recurrence (early vs. late) that implicate the following two different mechanisms for seizure recurrence: (1) a failure to either define/resect the epileptogenic zone, and (2) the nonstatic nature of epilepsy as a disease through the persistence of proepileptic cortical pathology. We describe the temporal patterns of epilepsy surgery failures and discuss their potential clinical, histopathologic, genetic, and molecular mechanisms. In addition, we review predictors of successful surgical interventions and analyze the natural history of epilepsy following surgical intervention. We hypothesize that the acute/early postoperative failures are due to errors in localizing and/or resecting the epileptic focus, whereas late recurrences are likely due to development/maturation of a new and active epileptic focus (de novo epileptogenesis).

Robot-Assisted Stereotactic Laser Ablation in Medically Intractable Epilepsy: Operative Technique

BACKGROUND: Stereotactic laser ablation offers an advantage over open surgical procedures for treatment of epileptic foci, tumors, and other brain pathology. Robot-assisted stereotactic laser ablation could offer an accurate, efficient, minimally invasive, and safe method for placement of an ablation catheter into the target. OBJECTIVE: To determine the feasibility of placement of a stereotactic laser ablation catheter into a brain lesion with the use of robotic assistance, via a safe, accurate, efficient, and minimally invasive manner. METHODS: A laser ablation catheter (Visualase, Inc) was placed by using robotic guidance (ROSA, Medtech Surgical, Inc) under general anesthesia into a localized epileptogenic periventricular heterotopic lesion in a 19-year-old woman with 10-year refractory focal seizure history. The laser applicator (1.65 mm diameter) position was confirmed by using magnetic resonance imaging (MRI). Ablation using the Visualase system was performed under multiplanar imaging with real-time thermal imaging and treatment estimates in each plane. A postablation MRI sequence (T1 postgadolinium contrast injection) was used to immediately confirm the ablation. RESULTS: MRI showed accurate skin entry point and trajectory, with the applicator advanced to the lesions distal boundary. Ablation was accomplished in less than 3 minutes of heating. The overall procedure, from time of skin incision to end of last ablation, was approximately 90 minutes. After confirmation of proper lesioning by using a T1 contrast-enhanced MRI, the applicator was removed, and the incision was closed using a single stitch. No hemorrhage or other untoward complication was visualized. The patient awoke without any complication, was observed overnight after admitting to a regular floor bed, and was discharged to home the following day. CONCLUSION: This technique, using a combination of Visualase laser ablation, ROSA robot, and intraoperative MRI, facilitated a safe, efficacious, efficient, and minimally invasive approach that could be used for placement of 1 or multiple electrodes in the future. ABBREVIATIONS: EEG, electroencephalography SEEG, stereoelectroencephalography

Pattern of P450 expression at the human blood–brain barrier: Roles of epileptic condition and laminar flow

Purpose:  P450 enzymes (CYPs) play a major role in hepatic drug metabolism. It is unclear whether these enzymes are functionally expressed by the diseased human blood–brain barrier (BBB) and are involved in local drug metabolism or response. We have evaluated the cerebrovascular CYP expression and function, hypothesizing possible implication in drug‐resistant epilepsy.

Expression of Neural Stem Cell Surface Marker CD133 in Balloon Cells of Human Focal Cortical Dysplasia

Summary:  Purpose: Focal cortical dysplasia (CD) is characterized by the presence of dysmorphic neurons, laminar and columnar disorganization. A few patients with CD have balloon cells intermixed with dysmorphic neurons. The cellular characteristics of balloon cells remain unknown. This study was intended to determine further the cellular characteristics of balloon cells.

Long-term seizure outcome in reoperation after failure of epilepsy surgery.

OBJECTIVETreatment of patients who fail epilepsy surgery is problematic. Selected patients may be candidates for further surgery, potentially leading to a significant decrease in the frequency and severity of seizures. We present our long-term outcome series of highly investigated patients who failed resective epilepsy surgery and subsequently underwent reoperative resective procedures. METHODSWe performed a retrospective consecutive analysis of patients who underwent reoperative procedures because of medically intractable epilepsy at our institution from 1990 to 2001. Seventy patients underwent reoperative epilepsy surgery, with 57 patients having a minimum follow-up period of 2 years. We assessed the relationship between seizure outcome and categorical variables using χ2 and Fishers exact tests, and the relationship between outcome and continuous variables using a Wilcoxon rank-sum test. Statistical significance was set at a P value of 0.05. RESULTSOf the 57 patients (29 male and 28 female patients), the age of seizure onset ranged from 3 months to 39 years (mean, 10.7 ± 10.3 yr; median, 7 yr). The mean age at reoperation was 24.7 ± 12 years (range, 4–50 yr). The interval between first and second resection was 7 days to 16 years. The follow-up period ranged from 24 to 228 months (mean, 128 mo; mode, 132 mo). Seizure outcome was classified according to Engels classification. Fifty-two percent of the patients had a favorable outcome (38.6% were Class I and 14.0% were Class II). Patients with tumors as their initial pathology had better outcome compared with patients with focal cortical dysplasia and mesial temporal sclerosis (P < 0.05). CONCLUSIONReoperation should be considered in selected patients failing epilepsy resective surgery because approximately 50% of patients may have benefit. Patients with cortical dysplasia and mesial temporal sclerosis are less likely to improve after reoperation.