Guiding Neurosurgery by Evidence (Progress in Neurological Surgery Vol 19)
They were able to target the residual splenium of the corpus callosum with a single fiber. In a study, Lehner et al. DTI revealed decreased fractional anisotropy in the region of the ablated corpus callosum relative to the remainder of the nonablated corpus callosum. Resting-state fMRI was used to confirm a decrease in interhemispheric functional connectivity with preservation of intrahemispheric functional connectivity, a technique that has previously been employed to demonstrate the role of the corpus callosum in interhemispheric functional connectivity. Collectively, these data provide strong support in a small number of adult patients studied before and after LITT callosotomy.
Since that time, VNS has been frequently used off-label and in several studies in younger children. Blount et al. The model introduced the option to use a cardiac sensing algorithm to detect rapid heart rate changes, which can be associated with seizure onset. Standard VNS is performed in an open-loop system with intermittent stimulation that is always on. With the newer models in the AutoStim cardiac sensing mode, an additional automated stimulation pulse can be provided by the device, similar to the manual magnet swipe previously performed by the patient or caregiver.
This type of closed-loop stimulation can be useful for individuals who are physically or cognitively unable to perform a timely manual magnet swipe at seizure onset. Two studies have reported that the AutoStim feature is well tolerated by patients. In a paper, Conti et al.
They report that the events resolved with explant of the and replacement with a new model In addition to cardiac sensing, the model allows for programming a schedule for automatic advancement of stimulation parameters to improve ease of titrating stimulation after implantation. Automatic titration may be beneficial for those patients where repeat clinical visits are nontrivial. These added features, as well as a smaller-profile pulse generator, make for better efficacy and tolerance for patients undergoing VNS treatment.
Responsive neurostimulation RNS is an alternative, more regional, neuromodulation technique that functions in a closed-loop configuration.
In , Heck et al. To date there have been very few case reports of pediatric patients undergoing RNS therapy for refractory epilepsy. In a case report, Singhal et al. Magnetoencephalography and positron emission tomography revealed concordant findings that localized to the same area. Invasive EEG monitoring with ECoG surface and depth electrodes subsequently confirmed the seizure onset zone in the area of the FCD with rapid spread to the overlying posterior superior temporal gyrus and angular gyrus. Unfortunately, bedside clinical mapping found disruption of speech with stimulation to part of the superior temporal gyrus, prohibiting a strategy of complete resection.
Therefore, they opted for resection of the accessible FCD not associated with speech arrest accompanied by RNS placement during the same procedure. Continued improvement was seen at 6 months when she was only experiencing auras several times per week without progression to alteration of awareness. In the case presented in Fig.
Figure 3A shows an intraoperative view of the device sitting in a window of bone that has been cut to its dimensions using a template. Next to the device are anchors for holding intracranial electrodes in place. The implant can be seen in a profile view Fig.
Mark E Linskey
Despite the proximity to eloquent cortex, no postoperative deficits were noted and the patient achieved a significant reduction in seizure frequency over the course of 2 years. RNS neuromodulation for seizure onset in eloquent cortex. A: Intraoperative photograph demonstrating the RNS system and implanted electrodes fixed to the skull. B: Postoperative lateral radiograph showing the device in place.
C: CT image demonstrating the depth electrodes used for sensing and stimulation. RNS is designed to deliver electrical stimulation in response to the onset of a seizure detected by digital signal analysis of the electrocorticogram.
Guiding neurosurgery by evidence, Editor: B.E. Pollock
In this fashion the direct effect is primarily to abate progression. This effect may be responsible for the decrease in seizure duration and intensity reported at initial follow-up. Interestingly, early reports suggest there may also be a neuromodulatory effect on the seizure network over time that may also lead to decrease in seizure occurrence, separate from the effect of stopping a seizure once it is detected. Such an effect of stimulation leading to decreased seizure generation is similar to what has been reported with adult RNS 43 and other neuromodulation devices such as VNS and DBS 52 for epilepsy.
A progressive benefit of neuromodulation was also observed by Kokoszka et al. In the year-old patient, after an extensive prior surgical and invasive monitoring history, it was decided to place cortical surface electrodes over the left frontal and right temporal cortex as well as depth electrodes in the anterior nucleus of the thalamus.
Over the first 3 months of stimulation there was not only a decrease in seizure duration, suggesting successful arrest of seizures once detected by the RNS, but also a decrease in the daily rate of detected abnormalities in the electrocorticogram. With the goal of additional seizure control, the team decided to reconfigure the device to use one of the thalamic electrodes for stimulation while using the temporal surface electrode for both seizure detection and stimulation. The second patient 9 years old had a seizure onset zone that co-localized with eloquent speech and motor cortex on stimulation mapping in the left frontal and parietal lobes.
Surface electrodes were placed over the putative seizure onset zone; 17 months later her seizure frequency had been reduced from 12 to 2 seizures per month, and at 21 months postoperatively she had been seizure free for 4 months. Performing such an exchange can be done in a less-invasive procedure, as the proximal leads reside adjacent to the device in the extracranial space for easier access.
Therefore, multiple stimulation and recording combinations can be configured in addition to varied stimulation parameters to optimize the monitoring and stimulation profiles for the individual patient. Chan et al.
They instead inserted depth electrodes in the hippocampus and in the neocortex overlying a periventricular nodular heterotopia identified on MRI in one patient, and in the hippocampus and orbitofrontal cortex of the second. In both patients these were sites where interictal spiking had been observed on invasive monitoring. Through correlation of chronic ECoG recordings via the RNS device with seizure diaries kept by the patients, they were able to detect seizures in the neocortex that rapidly spread to the hippocampus of the first patient and in the hippocampus, but not the orbitofrontal cortex, of the second.
Deep brain stimulation DBS , a third type of neuromodulation, is well known to neurosurgeons for the treatment of movement disorders and has gained traction in recent years for treating medically refractory epilepsy see the article by Zhou et al. The results of a randomized double-blind trial involving stimulation of the anterior nuclei of the thalamus for epilepsy SANTE were published in The study included a 3-month blinded stimulation versus sham period, similar to that of previously mentioned neuromodulation trials.
The between-groups difference in seizure frequency reduction was greater with increased time of stimulation such that at the end of the 3-month blinded period the stimulation group achieved a Alternative targets include the centromedian nucleus, subthalamic nucleus, ventral intermediate nucleus of the thalamus, nucleus accumbens, caudal zona incerta, mammillothalamic tract, fornix, posterior hypothalamus, and hippocampus.
The encouraging results of trials and cases series in adults has led to similar case reports and series in pediatric patients. Yan et al. In this study, which was published in , they identified 21 studies describing a total of 40 cases in which pediatric patients age range 4—18 years underwent DBS for epilepsy. The various studies used a variety of targets, with the most frequent being the centromedian nucleus of the thalamus used in 18 of 40 cases. With this configuration, they reported improved seizure response using the combination of ANT stimulation and cortical sensing and stimulation.
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In this manner they effectively performed DBS in a closed-loop fashion. In addition to expanding the minimally invasive surgical procedures, recent work has sought to advance noninvasive diagnostic tools with advanced functional imaging. Resting-state functional MRI r-fMRI is a functional imaging technique that detects the low-frequency fluctuations in the blood oxygen level—dependent BOLD signal from the brain at rest.
One of the unique strengths of r-fMRI is the ability to identify intrinsic brain networks through correlations in the slow fluctuations of the BOLD signal. Seizure networks in epilepsy are postulated to disrupt these fluctuations and intrinsic networks. One such study measured r-fMRI in pediatric patients with temporal lobe epilepsy.
Shah et al.
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Lancet Oncol. Counterbalancing risks and gains from extended resections in malignant glioma surgery: a supplemental analysis from the randomized 5-aminolevulinic acid glioma resection study. Clinical article. Extent of resection and survival in glioblastoma multiforme: identification of and adjustment for bias. Brown, T. Association of the extent of resection with survival in glioblastoma: a systematic review and meta-analysis.maisonducalvet.com/dating-sites-de-la-bisbal-dempord.php
Guiding neurosurgery by evidence, Editor: B.E. Pollock | SpringerLink
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Maximize surgical resection beyond contrast-enhancing boundaries in newly diagnosed glioblastoma multiforme: is it useful and safe? A single institution retrospective experience. Chaichana, K. Establishing percent resection and residual volume thresholds affecting survival and recurrence for patients with newly diagnosed intracranial glioblastoma. Oppenlander, M.