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ABSTRACT: : The compression of the cerebellum is of unclear significance in posterior fossa compression (Chiari I). We studied the diffusion tensor imaging changes (Fractional Anisotropy - FA and Apparent Diffusion Coefficient - ADC) before and after Chiari surgery and correlated findings with clinical and radiological presentation.
: We evaluated MR studies, obtained as part of clinical scans, in 10 patients before and after posterior fossa decompression of Chiari I malformations. Studies included both conventional (structural) MRI and diffusion tensor imaging (DTI). The average DTI parameters of established regions of interest were calculated. Resolution of clinical symptoms was also noted.
: Nine of 10 patients showed changes from preoperative DTI parameters after decompression. Cerebellar white matter (middle cerebellar peduncle) demonstrated a significant decrease in ADC (pre = 0.77 ± 0.07 (standard deviation), post = 0.72 ± 0.04; T = 3.93, P = 0.003) and trend increase in FA (pre = 0.497 ± 0.079, post = 0.542 ± 0.096 T = -2.18, P = 0.057). All of these patients presented with both radiological and clinical improvement including resolution of syringomyelia, improvement of headaches and other neurological symptoms. All of the patients were able to resume their daily activities.
: Both ADC and FA measurements returned closer to normal expected values in the middle cerebellar peduncle. The increase in FA suggests a normalization of white matter integrity not apparent in conventional imaging. The pre and postoperative diffusion tensor imaging evaluation is a readily available additional tool in the neuroradiological arsenal. It may become a valuable asset in medical decision making and successful management of Chiari I malformation patients. Nevertheless more studies are needed to assess properly its value, correlation with symptoms and outcome, reliability of repeat measurements in non-surgical patients, and any possible clinical application.
Neurosurgery 08/2012; 71(2):E578. · 2.79 Impact Factor
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ABSTRACT: The gold-standard method for determining cortical functional organization in the context of neurosurgical intervention is electrical cortical stimulation (ECS), which disrupts normal cortical function to evoke movement. This technique is imprecise, however, as motor responses are not limited to the precentral gyrus. Electrical cortical stimulation also can trigger seizures, is not always tolerated, and is often unsuccessful, especially in children. Alternatively, endogenous motor and sensory signals can be mapped by somatosensory evoked potentials (SSEPs), functional MRI (fMRI), and electrocorticography of high gamma (70-150 Hz) signal power, which reflect normal cortical function. The authors evaluated whether these 4 modalities of mapping sensorimotor function in children produce concurrent results.
The authors retrospectively examined the charts of all patients who underwent epilepsy surgery at Seattle Children's Hospital between July 20, 1999, and July 1, 2011, and they included all patients in whom the primary motor or somatosensory cortex was localized via 2 or more of the following tests: ECS, SSEP, fMRI, or high gamma electrocorticography (hgECoG).
Inclusion criteria were met by 50 patients, whose mean age at operation was 10.6 years. The youngest patient who underwent hgECoG mapping was 2 years and 10 months old, which is younger than any patient reported on in the literature. The authors localized the putative sensorimotor cortex most often with hgECoG, followed by SSEP and fMRI; ECS was most likely to fail to localize the sensorimotor cortex.
Electrical cortical stimulation, SSEP, fMRI, and hgECoG generally produced concordant localization of motor and sensory function in children. When attempting to localize the sensorimotor cortex in children, hgECoG was more likely to produce results, was faster, safer, and did not require cooperation. The hgECoG maps in pediatric patients are similar to those in adult patients published in the literature. The sensorimotor cortex can be mapped by hgECoG and fMRI in children younger than 3 years old to localize cortical function.
Journal of Neurosurgery Pediatrics 06/2012; 10(1):1-6. · 1.53 Impact Factor
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ABSTRACT: Brain activity patterns during face processing have been extensively explored with functional magnetic resonance imaging (fMRI)
and event-related potentials (ERPs). ERP source localization adds a spatial dimension to the ERP time series recordings, which
allows for a more direct comparison and integration with fMRI findings. The goals for this study were (1) to compare the spatial
descriptions of neuronal activity during face processing obtained with fMRI and ERP source localization using low-resolution
electromagnetic tomography (LORETA), and (2) to use the combined information from source localization and fMRI to explore
how the temporal sequence of brain activity during face processing is summarized in fMRI activation maps. fMRI and high-density
ERP data were acquired in separate sessions for 17 healthy adult males for a face and object processing task. LORETA statistical
maps for the comparison of viewing faces and viewing houses were coregistered and compared to fMRI statistical maps for the
same conditions. The spatial locations of face processing-sensitive activity measured by fMRI and LORETA were found to overlap
in a number of areas including the bilateral fusiform gyri, the right superior, middle and inferior temporal gyri, and the
bilateral precuneus. Both the fMRI and LORETA solutions additionally demonstrated activity in regions that did not overlap.
fMRI and LORETA statistical maps of face processing-sensitive brain activity were found to converge spatially primarily at
LORETA solution latencies that were within 18ms of the N170 latency. The combination of data from these techniques suggested
that electrical brain activity at the latency of the N170 is highly represented in fMRI statistical maps.
Brain Topography 04/2012; 22(2):83-96. · 3.45 Impact Factor
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ABSTRACT: The presurgical evaluation of patients with epilepsy often requires an intracranial study in which both subdural grid electrodes and depth electrodes are needed. Performing a craniotomy for grid placement with a stereotactic frame in place can be problematic, especially in young children, leading some surgeons to consider frameless stereotaxy for such surgery. The authors report on the use of a system that uses electromagnetic impulses to track the tip of the depth electrode. Ten pediatric patients with medically refractory focal lobar epilepsy required placement of both subdural grid and intraparenchymal depth electrodes to map seizure onset. Presurgical frameless stereotaxic targeting was performed using a commercially available electromagnetic image-guided system. Freehand depth electrode placement was then performed with intraoperative guidance using an electromagnetic system that provided imaging of the tip of the electrode, something that has not been possible using visually or sonically based systems. Accuracy of placement of depth electrodes within the deep structures of interest was confirmed postoperatively using CT and CT/MR imaging fusion. Depth electrodes were appropriately placed in all patients. Electromagnetic-tracking-based stereotactic targeting improves the accuracy of freehand placement of depth electrodes in patients with medically refractory epilepsy. The ability to track the electrode tip, rather than the electrode tail, is a major feature that enhances accuracy. Additional advantages of electromagnetic frameless guidance are discussed.
Journal of Neurosurgery Pediatrics 11/2011; 8(5):464-7. · 1.53 Impact Factor
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ABSTRACT: The study of human brain electrophysiology has extended beyond traditional frequency ranges identified by the classical EEG rhythms, encompassing both higher and lower frequencies. Changes in high-gamma-band (>70 Hz) power have been identified as markers of local cortical activity. Fluctuations at infra-slow (<0.1 Hz) frequencies have been associated with functionally significant cortical networks elucidated using fMRI studies. In this study, we examined infra-slow changes in band-limited power across a range of frequencies (1-120 Hz) in the default mode network (DMN). Measuring the coherence in band-limited power fluctuations between spatially separated electrodes makes it possible to detect small, spatially extended, and temporally coherent fluctuating components in the presence of much larger incoherent fluctuations. We show that the default network is characterized by significant high-gamma-band (65-110 Hz) coherence at infra-slow (<0.1 Hz) frequencies. This coherence occurs over a narrow frequency range, centered at 0.015 Hz, commensurate with the frequency of BOLD signal fluctuations seen by fMRI, suggesting that quasi-periodic, infra-slow changes in local cortical activity form the neurophysiological basis for this network.
Journal of Neuroscience 08/2011; 31(32):11728-32. · 7.11 Impact Factor
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Hillary Shurtleff,
Molly Warner, Andrew Poliakov,
Brian Bournival,
Dennis W Shaw,
Gisele Ishak,
Tong Yang,
Mahesh Karandikar,
Russell P Saneto,
Samuel R Browd,
Jeffrey G Ojemann
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ABSTRACT: The authors describe their experience with functional MR (fMR) imaging in children as young as 5 years of age, or even younger in developmental age equivalent. Functional MR imaging can be useful for identifying eloquent cortex prior to surgical intervention. Most fMR imaging clinical work has been done in adults, and although children as young as 8 years of age have been included in larger clinical series, cases in younger children are rarely reported.
The authors reviewed presurgical fMR images in eight patients who were 8 years of age or younger, six of whom were 5 or 6 years of age. Each patient had undergone neuropsychological testing. Three patients functioned at a below-average level, with adaptive functioning age scores of 3 to 4 years. Self-paced finger tapping (with passive movement in one patient) and silent language tasks were used as activation tasks. The language task was modified for younger children, for whom the same (not novel) stimuli were used for extensive practice ahead of time and in the MR imaging unit. Patient preparation involved techniques such as having experienced staff present to work with patients and providing external management during imaging. Six of eight patients had extensive training and practice prior to the procedure. In the two youngest patients, this training included use of a mock MR unit.
All cases yielded successful imaging. Finger tapping in all seven of the patients who could perform it demonstrated focal motor activation in the frontal-parietal region, with expected activation elsewhere, including in the cerebellum. Three of four patients had the expected verb generation task activations, with left-hemisphere dominance, including a 6-year-old child who functioned at the 3-year, 9-month level. The only child (an 8-year-old) who was not prepared prior to the imaging session for the verb generation task failed this task due to movement artifact.
Despite the challenges of successfully using fMR imaging in very young and clinically involved patients, these studies can be performed successfully in children with a chronological age of 5 or 6 years and a developmental age as young as 3 or 4 years.
Journal of Neurosurgery Pediatrics 05/2010; 5(5):500-6. · 1.53 Impact Factor
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Carlo Giussani, Andrew Poliakov,
Raymond T Ferri,
Lauren L Plawner,
Samuel R Browd,
Dennis W W Shaw,
Tanya Z Filardi,
Corrine Hoeppner,
J Russell Geyer,
James M Olson,
James G Douglas,
Elisabeth H Villavicencio,
Richard G Ellenbogen,
Jeffrey G Ojemann
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ABSTRACT: Intrinsic diffuse brainstem tumors and demyelinating diseases primarily affecting the brainstem can share common clinical and radiological features, sometimes making the diagnosis difficult especially at the time of first clinical presentation. To explore the potential usefulness of new MRI sequences in particular diffusion tensor imaging fiber tracking in differentiating these two pathological entities, we review a series of brainstem tumors and demyelinating diseases treated at our institution.
The clinical history including signs and symptoms and MRI findings of three consecutive demyelinating diseases involving the brainstem that presented with diagnostic uncertainty and three diffuse intrinsic brainstem tumors were reviewed, along with a child with a supratentorial tumor for comparison. Fiber tracking of the pyramidal tracts was performed for each patient using a DTI study at the time of presentation. Additionally Fractional Anisotropy values were calculated for each patient in the pons and the medulla oblongata.
Routine MR imaging was unhelpful in differentiating between intrinsic tumor and demyelination. In contrast, retrospective DTI fiber tracking clearly differentiated the pathology showing deflection of the pyramidal tracts posteriorly and laterally in the case of intrinsic brainstem tumors and, in the case of demyelinating disease, poorly represented and truncated fibers. Regionalized FA values were variable and of themselves were not predictive either pathology.
DTI fiber tracking of the pyramid tracts in patients with suspected intrinsic brainstem tumor or demyelinating disease presents two clearly different patterns that may help in differentiating between these two pathologies when conventional MRI and clinical data are inconclusive.
NeuroImage 04/2010; 52(1):217-23. · 5.89 Impact Factor
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ABSTRACT: The relationship between changes in functional magnetic resonance imaging and neuronal activity remains controversial. Data collected during awake neurosurgical procedures for the treatment of epilepsy provided a rare opportunity to examine this relationship in human temporal association cortex. We obtained functional magnetic resonance imaging blood oxygen dependent signals, single neuronal activity and local field potentials from 8 to 300 Hz at 13 temporal cortical sites, from nine subjects, during paired associate learning and control measures. The relation between the functional magnetic resonance imaging signal and the electrophysiologic parameters was assessed in two ways: colocalization between significant changes in these signals on the same paired associate-control comparisons and multiple linear regressions of the electrophysiologic measures on the functional magnetic resonance imaging signal, across all tasks. Significant colocalization was present between increased functional magnetic resonance imaging signals and increased local field potentials power in the 50-250 Hz range. Local field potentials power greater than 100 Hz was also a significant regressor for the functional magnetic resonance imaging signal, establishing this local field potentials frequency range as a neuronal correlate of the functional magnetic resonance imaging signal. There was a trend for a relation between power in some low frequency local field potentials frequencies and the functional magnetic resonance imaging signal, for 8-15 Hz increases in the colocalization analysis and 16-23 Hz in the multiple linear regression analysis. Neither analysis provided evidence for an independent relation to frequency of single neuron activity.
Brain 09/2009; 133(Pt 1):46-59. · 9.46 Impact Factor
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ABSTRACT: Presumably, second-language (L2) learning is mediated by changes in the brain. Little is known about what changes in the brain, how the brain changes, or when these changes occur during learning. Here, we illustrate by way of example how modern brain-based methods can be used to discern some of the changes that occur during L2 learning. Preliminary results from three studies indicate that classroom-based L2 instruction can result in changes in the brain's electrical activity, in the location of this activity within the brain, and in the structure of the learners’ brains. These changes can occur during the earliest stages of L2 acquisition.
Journal of Neurolinguistics 12/2008; 21(6):509-521. · 1.97 Impact Factor
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ABSTRACT: Abstract
Background
Three-dimensional (3-D) visualization of multimodality neuroimaging data provides a powerful technique for viewing the relationship between structure and function. A number of applications are available that include some aspect of 3-D visualization, including both free and commercial products. These applications range from highly specific programs for a single modality, to general purpose toolkits that include many image processing functions in addition to visualization. However, few if any of these combine both stand-alone and remote multi-modality visualization in an open source, portable and extensible tool that is easy to install and use, yet can be included as a component of a larger information system.
Results
We have developed a new open source multimodality 3-D visualization application, called MindSeer, that has these features: integrated and interactive 3-D volume and surface visualization, Java and Java3D for true cross-platform portability, one-click installation and startup, integrated data management to help organize large studies, extensibility through plugins, transparent remote visualization, and the ability to be integrated into larger information management systems. We describe the design and implementation of the system, as well as several case studies that demonstrate its utility. These case studies are available as tutorials or demos on the associated website: http://sig.biostr.washington.edu/projects/MindSeer .
Conclusion
MindSeer provides a powerful visualization tool for multimodality neuroimaging data. Its architecture and unique features also allow it to be extended into other visualization domains within biomedicine.
BMC Bioinformatics. 01/2007;
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ABSTRACT: This cortical stimulation mapping study investigates the neural representation of action and object naming. Data from 13 neurosurgical subjects undergoing awake cortical mapping is presented. Our findings indicate clear evidence of differential disruption of noun and verb naming in the context of this naming task. At the individual level, evidence was found for punctuate regions of perisylvian cortex subserving noun and verb function. Across subjects, however, the location of these sites varied. This finding may help explain discrepancies between lesion and functional imaging studies of noun and verb naming. In addition, an alternative coding of these data served to highlight the grammatical class vulnerability of the target response. The use of this coding scheme implicates a role for the supramarginal gyrus in verb-naming behavior. These data are discussed with respect to a functional-anatomical pathway underlying verb naming.
Human Brain Mapping 02/2005; 24(1):1-10. · 5.88 Impact Factor
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ABSTRACT: Cortical mapping (CSM) studies have shown cortical locations for language function are highly variable from one subject to the next. If individual variation can be normalized, patterns of language organization may emerge that were heretofore hidden. In order to uncover these patterns, computer-aided spatial normalization to a common atlas is required. Our goal was to determine a methodology by which spatial normalization methods could be evaluated and compared. We developed key metrics to measure accuracy of a surface-based (Caret) and volume-based (SPM2) method. We specified that the optimal method would i) minimize variation as measured by spread reduction between CSM language sites across subjects while also ii) preserving anatomical localization of all CSM sites. Eleven subject's structural MR image sets and corresponding CSM site coordinates were registered to the colin27 human brain atlas using each method. Local analysis showed that mapping error rates were highest in morphological regions with the greatest difference between source and target. Also, SPM2 mapped significantly less type 2 errors. Although our experiment did not show statistically significant global differences between the methods, our methodology provided valuable insights into the pros and cons of each method.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2005; 5:5331-4.
