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ABSTRACT: PURPOSE: Single-pulse electrical stimulation (SPES) during intracranial recordings is part of the epilepsy presurgical evaluation protocol at King's College Hospital (London). Epileptiform responses correlated to the stimulus (delayed responses - DRs) tend to occur in areas of seizure onset, thereby allowing interictal identification of epileptogenic cortex in patients suffering refractory epilepsy. This preliminary study investigated the validity of SPES in the operating theatre under general anaesthesia (GA) during the implantation procedure, aiming to improve the positioning of intracranial electrodes. METHODS: Twelve drug-resistant epilepsy patients implanted with depth and/or subdural electrodes were studied. SPES (1ms pulses, 4-8mA, 0.2Hz) was performed during both intra-operative electrode implantation under GA and chronic intracranial ECoG recordings, and the two recordings were compared in terms of cortical responses produced by stimulation and their electrode location. RESULTS: In 8/12 patients, SPES during chronic recordings produced DRs positively correlated to seizure onset and/or early seizure propagation areas. Of those eight patients, four showed DRs during electrode implantation under GA over the same electrode contacts. Among the four patients without DR during GA, three had continuous localized spontaneous epileptiform discharges, which made interpretation of SPES responses unreliable. CONCLUSION: This study showed that, under GA, DRs can be reliably replicated, without false positive epileptiform responses to SPES, although the method's sensitivity is greatly reduced by spontaneous discharges. Results support SPES as a complementary technique that can be used to improve electrode placement during epilepsy surgery when no profound interictal activity is present.
Seizure 01/2013; · 1.80 Impact Factor
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ABSTRACT: ObjectiveReliable identification of the subthalamic nucleus (STN) and globus pallidus interna (GPi) is critical for deep brain stimulation
(DBS) of these structures. The purpose of this study was to compare the visibility of the STN and GPi with various MRI techniques
and to assess the suitability of each technique for direct stereotactic targeting.
MethodsMR images were acquired from nine volunteers with T2- and proton density-weighted (PD-W) fast spin echo, susceptibility-weighted
imaging (SWI), phase-sensitive inversion recovery and quantitative T1, T2 and T2* mapping sequences. Contrast-to-noise ratios
(CNR) for the STN and GPi were calculated for all sequences. Targeting errors on SWI were evaluated on magnetic susceptibility
maps. The sequences demonstrating the best conspicuity of DBS target structures (SWI and T2*) were then applied to ten patients
with movement disorders, and the CNRs for these techniques were assessed.
ResultsSWI offers the highest CNR for the STN, but standard PD-W images provide the best CNR for the pallidum. Susceptibility maps
indicated that the GPi margins may be shifted slightly on SWI, although no shifts were seen for the STN.
ConclusionSWI may improve the visibility of the STN on pre-operative MRI, potentially improving the accuracy of direct stereotactic
targeting.
KeywordsMRI-Deep brain stimulation-Direct stereotactic targeting-Subthalamic nucleus-Globus pallidus
European Radiology 04/2012; 21(1):130-136. · 3.22 Impact Factor
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ABSTRACT: To describe neuronal firing patterns observed during human spontaneous interictal epileptiform discharges (IEDs) and responses to single pulse electrical stimulation (SPES).
Activity of single neurons was recorded during IEDs and after SPES in 11 consecutive patients assessed with depth EEG electrodes and attached microelectrodes.
A total of 66 neurons were recorded during IEDs and 151 during SPES. We have found essentially similar patterns of neuronal firing during IEDs and after SPES, namely: (a) a burst of high frequency firing lasting less than 100 ms (in 39% and 25% of local neurons, respectively for IED and SPES); (b) a period of suppression in firing lasting around 100-1300 ms (in 19% and 14%, respectively); (c) a burst followed by suppression (in 10% and 12%, respectively); (d) no-change (in 32% and 50%, respectively).
The similarities in neuronal firing patterns associated with IEDs and SPES suggest that, although both phenomena are initiated differently, they result in the activation of a common cortical mechanism, probably initiated by brief synchronised burst firing in some cells followed by long inhibition.
The findings provide direct in vivo human evidence to further comprehend the pathophysiology of human focal epilepsy.
Clinical neurophysiology: official journal of the International Federation of Clinical Neurophysiology 03/2012; 123(9):1736-44. · 3.12 Impact Factor
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ABSTRACT: Deep brain stimulation hardware is constantly advancing. The last few years have seen the introduction of rechargeable cell technology into the implanted pulse generator design, allowing for longer battery life and fewer replacement operations. The Medtronic® system requires an additional pocket adaptor when revising a non-rechargeable battery such as their Kinetra® to their rechargeable Activa® RC. This additional hardware item can, if it migrates superficially, become an impediment to the recharging of the battery and negate the intended technological advance.
To report the emergence of the 'shielded battery syndrome', which has not been previously described.
We reviewed our deep brain stimulation database to identify cases of recharging difficulties reported by patients with Activa RC implanted pulse generators.
Two cases of shielded battery syndrome were identified. The first required surgery to reposition the adaptor to the deep aspect of the subcutaneous pocket. In the second case, it was possible to perform external manual manipulation to restore the adaptor to its original position deep to the battery.
We describe strategies to minimise the occurrence of the shielded battery syndrome and advise vigilance in all patients who experience difficulty with recharging after replacement surgery of this type for the implanted pulse generator.
Stereotactic and Functional Neurosurgery 03/2012; 90(2):113-7. · 1.85 Impact Factor
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ABSTRACT: Refractory status epilepticus (RSE) is associated with high mortality. We report a potential treatment alternative.
Deep brain stimulation (DBS) of the centromedian thalamic nuclei (CMN) can be effective in the treatment of RSE.
Report of the evolution of RSE after DBS of the CMN in a 27-year-old man.
In the course of an encephalopathy of unknown origin, and after a cardiac arrest, the patient developed RSE with myoclonic jerks and generalized tonic-clonic seizures. The EEG showed continuous generalized periodic epileptiform discharges (GPEDS). Five weeks after RSE onset, bilateral DBS of the CMN was started. This treatment was immediately followed by disappearance of tonic-clonic seizures and GPEDS, suggesting a resolution of RSE. The patient continued having multifocal myoclonic jerks, probably subcortical in origin, which resolved after 4 weeks. The patient remained clinically stable for 2 months in a persistent vegetative state.
The remission of RSE, the abolition of GPEDS, and the patient survival suggest that DBS of the CMN may be efficacious in the treatment of refractory, generalized status epilepticus.
Brain Stimulation 10/2011; 5(4):594-8. · 3.76 Impact Factor
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ABSTRACT: Hypothalamic hamartoma (HH) is a relatively rare cause of epilepsy, mainly affecting children. Nearly all patients develop gelastic seizures, often followed by other focal seizure types. Our case illustrates the mechanisms of epileptogenesis in HH. The patient developed gelastic attacks as a baby, and secondarily generalized seizures and drop attacks at 9 years of age. Magnetic resonance imaging (MRI) confirmed the presence of a HH. Presurgical assessment with intracranial electroencephalography (EEG) monitoring recorded gelastic seizures with generalized epileptiform activity. Functional stimulation of the hamartoma provoked gelastic attacks. Single pulse electrical stimulation (SPES) was used to identify epileptogenic cortex. SPES of the left cingular cortex provoked generalized responses similar to the spontaneous generalized discharges. Our results suggest that long-standing history of epilepsy in patients with HH may be related to additional sources of epileptogenic activity. Electrical stimulation performed in this patient provided additional data to favor the hypothesis of secondarily epileptogenesis in the cingulate gyrus independently from the primary origin in the HH.
Epilepsia 05/2011; 52(5):e35-9. · 3.96 Impact Factor
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ABSTRACT: Reliable identification of the subthalamic nucleus (STN) and globus pallidus interna (GPi) is critical for deep brain stimulation (DBS) of these structures. The purpose of this study was to compare the visibility of the STN and GPi with various MRI techniques and to assess the suitability of each technique for direct stereotactic targeting.
MR images were acquired from nine volunteers with T2- and proton density-weighted (PD-W) fast spin echo, susceptibility-weighted imaging (SWI), phase-sensitive inversion recovery and quantitative T1, T2 and T2* mapping sequences. Contrast-to-noise ratios (CNR) for the STN and GPi were calculated for all sequences. Targeting errors on SWI were evaluated on magnetic susceptibility maps. The sequences demonstrating the best conspicuity of DBS target structures (SWI and T2*) were then applied to ten patients with movement disorders, and the CNRs for these techniques were assessed.
SWI offers the highest CNR for the STN, but standard PD-W images provide the best CNR for the pallidum. Susceptibility maps indicated that the GPi margins may be shifted slightly on SWI, although no shifts were seen for the STN.
SWI may improve the visibility of the STN on pre-operative MRI, potentially improving the accuracy of direct stereotactic targeting.
European Radiology 01/2011; 21(1):130-6. · 3.22 Impact Factor
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ABSTRACT: Stereotactic postoperative imaging is essential for verification of the position of electrodes implanted for deep brain stimulation (DBS). MRI offers superior visualisation of the DBS targets relative to CT, but previous adverse incidents have heightened concerns about risks of postoperative MRI. Preoperative MRI fused with postoperative CT offers an alternative method for evaluating electrode position, but before this method can be clinically applied, the image registration accuracy must be established. The purpose of this study was to quantitatively assess the accuracy of three different image registration and fusion methods.
Preoperative stereotactic MRI and postoperative stereotactic CT were acquired from 20 patients under- going DBS surgery (35 electrodes in total). The postoperative CT was registered and fused with the preoperative MRI, using three different registration algorithms. The position of each electrode tip was determined in stereotactic coordinates both in the (unfused) postoperative CT and the fused CT/MRI. The difference in tip position between the CT and fused CT/MRI was used to evaluate the registration accuracy.
The mean error along the lateral, anteroposterior, and vertical axes was 0.5, 0.5, and 1 mm, respectively.
CT/MRI fusion provides a safe, practical technique for postoperative identification of DBS electrodes.
Stereotactic and Functional Neurosurgery 07/2009; 87(4):205-10. · 1.85 Impact Factor
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ABSTRACT: Abnormal late responses to single pulse electrical stimulation (SPES) in patients with intracranial recordings can identify epileptogenic cortex. We aimed to investigate the presence of neuropathological abnormalities in abnormal SPES areas and to establish if removal of these areas improved postsurgical seizure control.
We studied abnormal responses to SPES during chronic intracranial recordings in 40 consecutive patients who were thereafter operated on because of refractory epilepsy and had a follow-up period of at least 12 months.
22 patients had abnormal responses to SPES exclusively located in resected regions (96% with favourable outcome), seven had abnormal responses to SPES located in resected and non-resected regions (71% with favourable outcome), three had abnormal responses to SPES exclusively outside the resected region (none with favourable outcome), and eight did not have abnormal responses to SPES (62.5% with favourable outcome). Surgical outcome was significantly better when areas with abnormal responses to SPES were completely resected compared with partial or no removal of abnormal SPES areas (p=0.006). Neuropathological examination showed structural abnormalities in the abnormal SPES areas in 26 of the 29 patients in whom these regions were resected, despite the absence of clear MRI abnormalities in nine patients.
Abnormal responses to SPES are functional markers of epileptogenic structural abnormalities, and can identify epileptogenic cortex and predict surgical outcome, especially when a frontal or temporal focus is suspected.
The Lancet Neurology 12/2005; 4(11):718-26. · 23.46 Impact Factor
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ABSTRACT: Magnetic resonance imaging (MRI) after implantation of electrodes in the subthalamic nuclei is currently performed at a number of sites, but a recent adverse incident and changes in MRI technology may heighten safety concerns. In this report, it is demonstrated that given whole-head image data, registration of postimplantation computed tomography to preimplantation MRI can enable verification of the position of electrodes to an accuracy of 2 mm. This registration technique can remove the need for potentially risky postoperative MRI.
Journal of Computer Assisted Tomography 28(4):548-50. · 1.22 Impact Factor
