FDG-PET/MRI coregistration improves detection of cortical dysplasia in patients with epilepsy

OBJECTIVE

Patients with cortical dysplasia (CD) are difficult to treat because the MRI abnormality may be undetectable. This study determined whether fluorodeoxyglucose (FDG)-PET/MRI coregistration enhanced the recognition of CD in epilepsy surgery patients.

METHODS

Patients from 2004-2007 in whom FDG-PET/MRI coregistration was a component of the presurgical evaluation were compared with patients from 2000-2003 without this technique. For the 2004-2007 cohort, neuroimaging and clinical variables were compared between patients with mild Palmini type I and severe Palmini type II CD.

RESULTS

Compared with the 2000-2003 cohort, from 2004-2007 more CD patients were detected, most had type I CD, and fewer cases required intracranial electrodes. From 2004-2007, 85% of type I CD cases had normal non-University of California, Los Angeles (UCLA) MRI scans. UCLA MRI identified CD in 78% of patients, and 37% of type I CD cases had normal UCLA scans. EEG and neuroimaging findings were concordant in 52% of type I CD patients, compared with 89% of type II CD patients. FDG-PET scans were positive in 71% of CD cases, and type I CD patients had less hypometabolism compared with type II CD patients. Postoperative seizure freedom occurred in 82% of patients, without differences between type I and type II CD cases.

CONCLUSIONS

Incorporating fluorodeoxyglucose-PET/MRI coregistration into the multimodality presurgical evaluation enhanced the noninvasive identification and successful surgical treatment of patients with cortical dysplasia (CD), especially for the 33% of patients with nonconcordant findings and those with normal MRI scans from mild type I CD.

Supraaortic arteries: contrast material dose reduction at 3.0-T high-spatial-resolution MR angiography--feasibility study

PURPOSE

To evaluate and compare the diagnostic image quality resulting from three contrast agent dose regimens for 3.0-T high-spatial-resolution three-dimensional magnetic resonance (MR) angiography of the supraaortic arteries.

MATERIALS AND METHODS

Institutional review board approval was obtained; informed consent was waived for this HIPAA-compliant study. One hundred twenty consecutive patients who underwent 3.0-T three-dimensional high-spatial-resolution contrast material-enhanced MR angiography of the supraaortic arteries with an identical acquisition protocol were assigned to either the high-dose (0.154 mmol per kilogram of body weight), intermediate-dose (0.097 mmol/kg), or low-dose (0.047 mmol/kg) group. Two readers evaluated resulting images for arterial definition, venous contamination, and arterial stenosis. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were evaluated at six consistent sites. Statistical analysis was performed with the Kruskal-Wallis, Wilcoxon signed rank, and analysis of variance tests and the kappa coefficient.

RESULTS

Readers 1 and 2 scored vascular definition as excellent or sufficient for diagnosis in 1311 of 1360 segments and in 1313 of 1360 segments in the high-dose group (kappa = 0.73), in 1321 of 1354 and in 1319 of 1354 segments in the intermediate-dose group (kappa = 0.77), and in 1322 of 1350 and in 1320 of 1350 segments in the low-dose group (kappa= 0.66), respectively. Arterial occlusive disease was detected by reader 1 in 52, 27, and 98 segments in the high-, intermediate-, and low-dose groups, respectively. Arterial occlusive disease was detected by reader 2 in 48, 25, and 100 segments in high-, intermediate-, and low-dose groups, respectively. No significant difference existed among the three groups regarding arterial definition scores (reader 1, P = .21; reader 2, P = .25) and venous contamination scores (reader 1, P = .38; reader 2, P = .35). SNRs and CNRs were lower in the low-dose group (P < .01).

CONCLUSION

At 3.0 T, high-spatial-resolution MR angiography of the supraaortic arteries can be performed with contrast agent doses as low as 0.047 mmol/kg, without compromising image quality, acquisition speed, or spatial resolution.

SUPPLEMENTAL MATERIAL

http://radiology.rsnajnls.org/cgi/content/full/249/3/980/DC1http://radiology.rsnajnls.org/cgi/content/full/249/3/980/DC2.

Neuroimaging in pediatric epilepsy: a multimodality approach

Pediatric patients with intractable epilepsy represent a challenging clinical population. However, recent advances in neuroimaging with a multimodality imaging approach that combines fluorine 18 fluorodeoxyglucose positron emission tomography, magnetoencephalography, diffusion tensor imaging, and magnetic source imaging with conventional magnetic resonance imaging continue to improve diagnosis and treatment in affected patients. These advances are increasing the understanding of the underlying disease process and improving the ability to noninvasively detect epileptogenic foci that in the past went undetected and whose accurate localization is crucial for a good outcome following surgical resection.

High-resolution depth electrode localization and imaging in patients with pharmacologically intractable epilepsy

Localization and targeting of depth electrodes in specific regions of the human brain is critical for accurate clinical diagnoses and treatment as well as for neuroscientific electrophysiological research. By using high-resolution magnetic resonance imaging combined with 2D computational unfolding, the authors present a method that improves electrode localization in the medial temporal lobe. This method permits visualization of electrode placements in subregions of the hippocampus and parahippocampal gyrus, allowing for greater specificity in relating electrophysiological and anatomical features in the human medial temporal lobe. Such methods may be extended to therapeutic procedures targeting specific neuronal circuitry in subfields of structures deep in the human brain.

Early Neutrophilia Is Associated With Volume of Ischemic Tissue in Acute Stroke

Background and Purpose— Few data exist on the relationship between differential subpopulations of peripheral leukocytes and early cerebral infarct size in ischemic stroke. Using diffusion-weighted MR imaging (DWI), we assessed the relationship of early total and differential peripheral leukocyte counts and volume of ischemic tissue in acute stroke.

Methods— All included patents had laboratory investigations and neuroimaging collected within 24 hours of stroke onset. Total peripheral leukocyte counts and differential counts were analyzed individually and by quartiles. DWI lesions were outlined using a semiautomated threshold technique. The relationship between leukocyte quartiles and DWI infarct volumes was examined using multivariate quartile regression.

Results— 173 patients met study inclusion criteria. Median age was 73 years. Total leukocyte counts and DWI volumes showed a strong correlation (Spearman rho=0.371, P <000.1). Median DWI volumes (mL) for successive neutrophil quartiles were: 1.3, 1.3, 3.2, and 20.4 ( P for trend <0.001). Median DWI volumes (mL) for successive lymphocyte quartiles were: 3.2, 8.1, 1.3, and 1.5 ( P =0.004). After multivariate analysis, larger DWI volume remained strongly associated with higher total leukocyte and neutrophil counts (both probability values <0.001), but not with lymphocyte count ( P =0.4971). Compared with the lowest quartiles, DWI volumes were 8.7 mL and 12.9 mL larger in the highest quartiles of leukocyte and neutrophil counts, respectively.

Conclusions— Higher peripheral leukocyte and neutrophil counts, but not lymphocyte counts, are associated with larger infarct volumes in acute ischemic stroke. Attenuating neutrophilic response early after ischemic stroke may be a viable therapeutic strategy and warrants further study.

Prior antiplatelet use and infarct volume in ischemic stroke

BACKGROUND

Conflicting data exist on the role of antiplatelet agents in reducing incident ischemic stroke magnitude, but most prior studies used clinically-assessed neurologic deficit as the index of stroke extent rather than more precise volumetric measurements of infarct size. We assessed the relation of premorbid antiplatelet use to initial diffusion-weighted MRI (DWI) lesion volumes among acute ischemic stroke patients.

METHODS

Consecutive patients presenting within 24 h of ischemic stroke over an 18-month period were studied. DWI lesions were outlined using a semi-automated threshold technique. Subjects were categorized into two groups: antiplatelet (AP) or no antithrombotic (NA). The relationship between prestroke antithrombotic status and DWI infarct volumes was examined using multivariate quantile regression.

RESULTS

One hundred sixty-six individuals met study criteria: 75 AP and 91 NA patients. Median DWI volume was lower in the AP group than in the NA group (1.5 cc vs. 5.4 cc, p=0.031). A multivariable model (adjusting for age, history of transient ischemic attack, admission temperature, admission blood pressure, admission serum glucose, stroke onset to imaging interval, stroke mechanism, premorbid statin and antihypertensive use) demonstrated smaller infarcts in the AP vs. NA group (adjusted volume difference: -1.3 cc, 95% CI=-0.09, -2.5, p=0.037). Prior statin use, no history of TIA, large vessel atherosclerosis and microvascular ischemic disease stroke mechanism were also independently associated with reduced infarct volume.

CONCLUSIONS

Prior antiplatelet treatment is independently associated with reduced cerebral infarct volume among acute ischemic stroke patients. Premorbid statin use, TIA history and stroke mechanism also predict infarct volume in ischemic stroke.

A hypothesis regarding the pathogenesis and epileptogenesis of pediatric cortical dysplasia and hemimegalencephaly based on MRI cerebral volumes and NeuN cortical cell densities

This study compared MRI cerebral volumes and Neuronal-Nuclei (NeuN) cell densities in pediatric epilepsy surgery patients with cortical dysplasia (CD; n = 25) and hemimegalencephaly (HME; n = 14). Our purpose was to deduce possible mechanisms of pathogenesis and epileptogenesis based on an understanding of normal developmental corticoneurogenesis. We used MRI to measured cerebral hemisphere volumes, and NeuN staining to determine grey and white matter cell densities and cell sizes in the molecular layer, grey, and white matter. CD and HME surgical cases were compared with autopsy or non-CD cases (n = 20). Total MRI brain volumes were similar between non-CD, CD, and HME cases. However, in HME patients, the affected cerebral hemisphere was larger and the nonaffected side smaller than non-CD cases. Compared with autopsy cases, NeuN cell densities and cell sizes in CD and HME patients were increased in the molecular layer, upper grey matter, and white matter. In CD and HME cases, total cerebral hemisphere volumes were normal in size and there were more cortical neurons in upper layers than expected. The increase in cortical neuronal densities is consistent with the hypothesis that CD and HME pathogenesis involves increased neurogenesis in the late (not early) phases of cortical formation. In addition, more neurons in the molecular layer and white matter supports the concept that CD and HME pathogenesis also involves incomplete programmed cell death in the remnant cells occupying the preplate and subplate regions. Based on our anatomical and previous electrophysiological findings, we propose that in CD and HME seizure generation is the consequence of incomplete cerebral development with abnormal interactions between immature and mature cells and cellular networks.

Prediction of hemorrhagic transformation after recanalization therapy using T2*-permeability magnetic resonance imaging

OBJECTIVE

Predicting hemorrhagic transformation (HT) is critical in the setting of recanalization therapy for acute stroke. Dedicated magnetic resonance imaging (MRI) sequences for detection of increased blood-brain barrier (BBB) permeability recently have been developed. We evaluated the ability of a novel MRI permeability technique to detect baseline derangements predictive of various forms of HT after recanalization therapy.

METHODS

We retrospectively analyzed the clinical and pretreatment MRI data on patients undergoing recanalization therapy for acute cerebral ischemia at a university medical center from January 2004 to November 2006. Pretreatment MRI permeability images derived from perfusion source data were compared with posttreatment imaging to evaluate whether baseline BBB permeability derangements may predict HT after recanalization therapy. The use of a novel permeability technique to illustrate BBB derangements was based on the detection of decreased signal intensity at later time points in perfusion MRI acquisition, signifying continued local accumulation of contrast caused by leakage.

RESULTS

Among 32 patients, some degree of HT occurred in 12. Permeability image abnormalities at baseline were present in 7 of 12 patients with HT and none of the 20 patients without HT on follow-up images. The sensitivity of permeability abnormality for parenchymal hematoma was 83%. False-negative findings were noted in five cases, most commonly asymptomatic or minor HT after mechanical clot retrieval.

INTERPRETATION

Permeability images derived from pretreatment perfusion MRI source data may identify patients at risk for HT with high specificity. Our preliminary demonstration of permeability imaging based on standard perfusion data for prediction of hemorrhage merits further study with dedicated MRI BBB permeability acquisitions and multicenter validation.

Association of higher serum calcium levels with smaller infarct volumes in acute ischemic stroke

BACKGROUND

Elevated serum calcium levels at admission in patients with stroke have been associated with less severe clinical deficits and with better outcomes; however, the relationship between serum calcium levels and volumetric measurement of cerebral infarct size on neuroimaging has not been studied, to our knowledge.

OBJECTIVE

To assess the relationship between serum calcium levels at admission and initial diffusion-weighted magnetic resonance imaging (DWI) infarct volumes among patients with acute ischemic stroke.

DESIGN

Secondary analysis of prospectively collected hospital quality improvement data.

SETTING

Tertiary university hospital.

PATIENTS

One hundred seventy-three consecutive patients with acute ischemic stroke initially seen within 24 hours of the last known well time.

MAIN OUTCOME MEASURES

Total serum calcium levels were measured on admission and were collapsed into quartiles. The DWI lesions were outlined using a semiautomated threshold technique. The relationship between serum calcium level quartiles and DWI infarct volumes was examined using multivariate quartile regression analysis.

RESULTS

One hundred seventy-three patients (mean age, 70.3 years [age range, 24-100 years]; median National Institutes of Health Stroke Scale score, 4 [range, 0-38]) met the study criteria. The median DWI infarct volumes for the serum calcium level quartiles (lowest to highest quartile) were 9.42, 2.11, 1.03, and 3.68 mL. The median DWI infarct volume in the lowest serum calcium level quartile was larger than that in the other 3 quartiles (P < .005). After multivariate analysis, the median adjusted DWI infarct volumes for the serum calcium level quartiles (lowest to highest) were 8.9, 5.8, 4.5, and 3.8 mL. The median adjusted DWI infarct volume in the lowest serum calcium level quartile was statistically significantly larger than that in the other 3 quartiles (P < .05).

CONCLUSIONS

Higher serum calcium levels at admission are associated with smaller cerebral infarct volumes among patients with acute ischemic stroke. These results suggest that serum calcium level may serve as a clinical prognosticator following stroke and may be a potential therapeutic target for improving stroke outcome.

White matter fiber tractography and color mapping of the normal human cerebellum with diffusion tensor imaging

Diffusion tensor imaging (DTI) color mapping and fiber tractography was used to study the white matter within the cerebellum along with the afferent and efferent tracts associated with the cerebellum in 24 normal human subjects. The most prominent structures that can be readily identified using these DTI techniques are the middle, inferior and superior cerebellar peduncles. Furthermore DTI shows transverse white matter fiber that cross between the two cerebellar hemispheres at the level of the vermis. At the hemispheric level fibers to the dentate, to the emboliform nuclei are clearly visible on DTI as is the afferent pathway represented by the middle cerebellar peduncle. Selective DTI fiber tractography provides very exquisite images of the cerebellar peduncles and of the fibers projecting to and from the cerebellar cortex. This study demonstrates that DTI is complementary to conventional MRI in that DTI elucidates the orientation of white matter fiber bundles that are associated with the cerebellum. Therefore we anticipate that DTI will become an important adjunct to conventional MRI for clinical and basic studies of cerebellar ataxias and congenital disorders involving the cerebellum and brain stem. This work provides a summary of the normal DTI appearance of the cerebellar white matter which will be useful for interpreting DTI results in clinical populations.

Infantile spasm-associated microencephaly in tuberous sclerosis complex and cortical dysplasia

OBJECTIVE

In children with and without infantile spasms, this study determined brain volumes and cell densities in epilepsy surgery patients with tuberous sclerosis complex (TSC) and cortical dysplasia with balloon cells (CD).

METHODS

We compared TSC (n = 18) and CD (n = 17) patients with normal/autopsy controls (n = 20) for MRI gray and white matter volumes and neuronal nuclei (NeuN) cell densities.

RESULTS

In patients without a history of infantile spasms, TSC cases showed decreased gray and white matter volumes (-16%). In cases with a history of infantile spasms, both CD (-25%) and TSC (-35%) patients showed microencephaly. This was confirmed in monozygotic twins with TSC, where the twin with a history of spasms had cerebral volumes less (-16%) than the twin without a history of seizures. Regardless of seizure history, TSC patients showed decreased NeuN cell densities in lower gray matter (-36%), whereas CD patients had increased densities in upper cortical (+52%) and white matter regions (+65%). For TSC patients, decreased lower gray matter NeuN densities correlated with reduced MRI volumes.

CONCLUSIONS

Patients with tuberous sclerosis without spasms showed microencephaly associated with decreased cortical neuronal densities. In contrast, cortical dysplasia patients without spasms were normocephalic with increased cell densities. This supports the concept that tuberous sclerosis and cortical dysplasia have different pathogenetic mechanisms despite similarities in refractory epilepsy and postnatal histopathology. Furthermore, a history of infantile spasms was associated with reduced cerebral volumes in both cortical dysplasia and tuberous sclerosis patients, suggesting that spasms or their treatment may contribute to microencephaly independent of etiology.

Improving MRI differentiation of gray and white matter in epileptogenic lesions based on nonlinear feedback

A new method for enhancing MRI contrast between gray matter (GM) and white matter (WM) in epilepsy surgery patients with symptomatic lesions is presented. This method uses the radiation damping feedback interaction in high-field MRI to amplify contrast due to small differences in resonance frequency in GM and WM corresponding to variations in tissue susceptibility. High-resolution radiation damping-enhanced (RD) images of in vitro brain tissue from five patients were acquired at 14 T and compared with corresponding conventional T(1)-, T(2) (*)-, and proton density (PD)-weighted images. The RD images yielded a six times better contrast-to-noise ratio (CNR = 44.8) on average than the best optimized T(1)-weighted (CNR = 7.92), T(2) (*)-weighted (CNR = 4.20), and PD-weighted images (CNR = 2.52). Regional analysis of the signal as a function of evolution time and initial pulse flip angle, and comparison with numerical simulations confirmed that radiation damping was responsible for the observed signal growth. The time evolution of the signal in different tissue regions was also used to identify subtle changes in tissue composition that were not revealed in conventional MR images. RD contrast is compared with conventional MR methods for separating different tissue types, and its value and limitations are discussed.

Cholesterol level and symptomatic hemorrhagic transformation after ischemic stroke thrombolysis

BACKGROUND

Prestroke statin use may improve ischemic stroke outcomes, yet there is also evidence that statins and extremely low cholesterol levels may increase the risk of intracranial hemorrhage. We evaluated the independent effect of statin use and admission cholesterol level on risk of symptomatic hemorrhagic transformation (sHT) after recanalization therapy for acute ischemic stroke.

METHODS

We analyzed ischemic stroke patients recorded in a prospectively maintained registry that received recanalization therapies (IV or intra-arterial fibrinolysis or endovascular embolectomy) at a university medical center from September 2002 to May 2006. The independent effect of premorbid statin use on sHT post intervention was evaluated by logistic regression, adjusting for prognostic and treatment variables known to predict increased HT risk after ischemic stroke.

RESULTS

Among 104 patients, mean age was 70 years, and 49% were men. Male sex, hypertension, statin use, low total cholesterol and low-density lipoprotein (LDL) cholesterol, current smoking, elevated glucose levels, and higher admission NIH Stroke Scale (NIHSS) score were all associated with a greater risk of sHT in univariate analysis. After adjusting for covariates, low LDL cholesterol (odds ratio [OR], 0.968 per 1-mg/dL increase; 95% CI, 0.941 to 0.995), current smoking (OR, 14.568; 95% CI, 1.590 to 133.493), and higher NIHSS score (OR, 1.265 per 1-point increase; 95% CI, 1.047 to 1.529) were independently associated with sHT risk.

CONCLUSIONS

Lower admission low-density lipoprotein cholesterol level with or without statin use, current smoking, and greater stroke severity are associated with greater risk for symptomatic hemorrhagic transformation after recanalization therapy for ischemic stroke.

Reduced Neocortical Thickness and Complexity Mapped in Mesial Temporal Lobe Epilepsy with Hippocampal Sclerosis

We mapped the profile of neocortical thickness and complexity in patients with mesial temporal lobe epilepsy (MTLE) and hippocampal sclerosis. Thirty preoperative high-resolution magnetic resonance imaging scans were acquired from 15 right (mean age: 31.9 +/- 9.7 standard deviation [SD] years) and 15 left (mean age: 30.8 +/- 8.4 SD years) MTLE patients who were seizure-free for 2 years after anteriomesial temporal resection. Nineteen healthy controls were also scanned (mean age: 24.8 +/- 3.9 SD years). A cortical pattern matching technique mapped thickness across the entire neocortex. Mesial temporal structures were not included in this analysis. Cortical models were remeshed in frequency space to compute their fractal dimension (surface complexity). Both MTLE groups showed up to 30% bilateral decrease in cortical thickness, in the frontal poles, frontal operculum, orbitofrontal, lateral temporal, and occipital regions. In both groups, cortical complexity was decreased in multiple lobar regions. Significant linkages were found relating longer duration of epilepsy to greater cortical thickness reduction in the superior frontal and parahippocampal gyrus ipsilateral to the side of seizure onset. The pervasive extrahippocampal structural deficits may result from chronic seizure propagation or may reflect other causes such as initial precipitating factors leading to MTLE.

Predictors of Cerebral Microbleeds in Acute Ischemic Stroke and TIA Patients

BACKGROUND

Cerebral microbleeds (CMB) detected on gradient-echo T2*-weighted MRI have been associated with cognitive impairment and the potential for increased risk of intracranial hemorrhage. We evaluated risk factors for these microangiopathic lesions in a cohort of stroke and transient ischemic attack patients.

METHODS

Presence and number of CMB in consecutive acute stroke patients admitted to a university hospital stroke service over an 18-month period were rated. Multivariate models were generated to determine the contribution of 21 demographic and clinical variables to the frequency and number of CMB.

RESULTS

Of 164 patients (mean age 71 years, 52% female), 57 (35%) had CMB evident on gradient-echo T2*-weighted MRI. CMB were more commonly noted among patients with small vessel disease ischemic stroke mechanism (47%) than large vessel atherothromboembolic (12%) or cardioembolic (18%, p = 0.0001). In univariate analysis, patients with CMB were older, (p = 0.008), more likely to have been on >1 antihypertensive prior to admission (p = 0.024) than those without CMB. In multivariate logistic regression analyses, presumed small vessel stroke subtype, history of atrial fibrillation, being on >1 antihypertensive prior to admission, and smoking were independent factors increasing the risk of CMB. Logistic regression analysis by number of CMB showed almost similar findings.

CONCLUSIONS

CMB are more frequently noted in hospitalized stroke and transient ischemic attack patients with small vessel ischemia, as well as those with important modifiable vascular risk factors like atrial fibrillation and smoking.

FDG-PET/MRI coregistration and diffusion-tensor imaging distinguish epileptogenic tubers and cortex in patients with tuberous sclerosis complex: a preliminary report

PURPOSE

Patients with tuberous sclerosis complex (TSC) are potential surgical candidates if the epileptogenic region(s) can be accurately identified. This retrospective study determined whether FDG-PET/MRI coregistration and diffusion-tensor imaging (DTI) showed better accuracy in the localization of epileptogenic cortex than structural MRI in TSC patients.

METHODS

FDG-PET/MRI coregistration and/or DTI for apparent diffusion coefficient (ADC) and fractional anisotropy (FA) were utilized in 15 TSC patients. Presurgery scalp EEG and postsurgery seizure control identified epileptogenic tubers (n = 27) and these were compared with nonepileptogenic tubers (n = 204) for MRI tuber volume, volume of FDG-PET hypometabolism on MRI coregistration, DTI, ADC, and FA values.

RESULTS

Compared with nonepileptogenic tubers, epileptogenic regions had increased volume of FDG-PET hypometabolism (p < 0.0001), and increased ADC values in subtuber white matter (p < 0.0001). In contrast, the largest MRI identified tuber (p = 0.046) and decreased FA values (p = 0.58) were less accurate in identifying epileptogenic regions. Larger volumes of FDG-PET hypometabolism correlated positively with increased ADC values (p = 0.029), and localized to areas of cortical dysplasia adjacent to the tuber in four cases.

CONCLUSIONS

Larger volumes of FDG-PET hypometabolism relative to MRI tuber size and higher ADC values identified epileptogenic tubers and adjoining cortex containing cortical dysplasia in TSC patients with improved accuracy compared with largest tuber by MRI or lowest FA values. Used in conjunction with ictal scalp EEG and interictal magnetoencephalography, these newer neuroimaging techniques should improve the noninvasive evaluation of TSC patients with intractable epilepsy in distinguishing epileptogenic sites for surgical resection.

Three-Dimensional Cerebral Contrast-Enhanced Magnetic Resonance Venography at 3.0 Tesla

OBJECTIVE

The objective of this study was to evaluate a high spatial resolution 3-dimensional (3D) contrast-enhanced magnetic resonance (CE-MR) venography protocol for evaluation of intracranial venous system using highly accelerated parallel imaging at 3.0 T.

MATERIALS AND METHODS

Ten patients (4 male, 6 female; age, 38-76 years) with suspected cerebrovascular disease were prospectively studied on a 32-channel 3.0 T MR system. After a single intravenous contrast injection, high spatial resolution 3D CE-MR angiography of the entire supraaortic arteries was performed followed immediately by 3D cerebral CE-MR venography. By using a fast 3D gradient-recalled-echo sequence with elliptic centric k-space ordering and highly accelerated parallel acquisition (acceleration factor 3 and 2 in phase and slice encoding direction, respectively), 3D cerebral CE-MR venography was acquired with voxel dimensions of 0.7 x 0.7 x 0.8 mm in 24 seconds. Image evaluation was performed independently by 2 neuroradiologists for overall image quality, presence of noise, and artifacts. The image quality of 30 venous segments was evaluated in each subject using a 1 to 4 scoring scale. In 2 patients, catheter angiography was available for correlation. Statistical analysis of data was performed by using Wilcoxon rank sum test and kappa coefficient.

RESULTS

All studies were determined to be of diagnostic image quality by both observers. The majority (90%) of cerebral venous segments were evaluated to be of diagnostic image quality (median, 3; range, 3-4) by both readers and with excellent interobserver agreement (kappa = 0.86; 95% confidence interval, 0.79-0.93). One meningioma invading the superior sagittal sinus and one superior sagittal sinus fistula were detected subsequently confirmed by conventional angiography.

CONCLUSION

High spatial resolution 3D cerebral CE-MR venography is feasible and promising. Using a 32-channel 3.0 T system combined with multichannel array coils effectively supports highly accelerated parallel imaging, enabling subsequent acquisition of both high spatial resolution CE-MR angiography and CE-MR venography after a single contrast injection without impairing the image quality. More extensive clinical studies are warranted to establish the range of applications and confirm the accuracy of this technique.

Epileptogenesis in pediatric cortical dysplasia: the dysmature cerebral developmental hypothesis

Cortical dysplasia (CD) is the most frequent pathology found in pediatric epilepsy surgery patients with a nearly 80% incidence in children younger than 3 years of age. Younger cases are more likely to have multilobar and severe forms of CD compared with older patients with focal and mild CD. Using clinico-pathologic techniques, we have initiated studies that unravel the timing of CD pathogenesis that in turn suggest mechanisms of epileptogenesis. Morphological comparisons provided the first clue when we observed that cytomegalic neurons have similarities with human subplate cells, and balloon cells have features analogous to radial glia. This suggested that failure of prenatal cell degeneration before birth could explain the presence of postnatal dysmorphic cells in CD tissue. Neuronal density and MRI volumes indicate that there were more neurons than expected in CD tissue, and they were probably produced in later neurogenesis cell cycles. Together these findings imply that there is partial failure in later phases of cortical development that might explain the distinctive histopathology of CD. If correct, epileptogenesis should be the consequence of incomplete cellular maturation in CD tissue. In vitro electrophysiological findings are consistent with this notion. They show that balloon cells have glial features, cytomegalic neurons and recently discovered cytomegalic interneurons reveal atypical hyperexcitable intrinsic membrane properties, there are more GABA than glutamate spontaneous synaptic inputs onto neurons, and in a subset of cells NMDA and GABA(A) receptor-mediated responses and subunit expression are similar to those of immature neurons. Our studies support the hypothesis that there are retained prenatal cells and neurons with immature cellular and synaptic properties in pediatric CD tissue. We propose that local interactions of dysmature cells with normal postnatal neurons produce seizures. This hypothesis will drive future studies aimed at elucidating mechanisms of epileptogenesis in pediatric CD tissue.

Diffusion tensor MRI shows abnormal brainstem crossing fibers associated with ROBO3 mutations

Horizontal gaze palsy with progressive scoliosis (HGPPS) is caused by mutations in the ROBO3 gene, critical for the crossing of long ascending medial lemniscal and descending corticospinal tracts in the medulla. Diffusion tensor imaging in a patient with HGGPS revealed the absence of major pontine crossing fiber tracts and no decussation of the superior cerebellar peduncles. Mutations in the ROBO3 gene lead to a widespread lack of crossing fibers throughout the brainstem.

Electrical conductivities of the freshly excised cerebral cortex in epilepsy surgery patients; correlation with pathology, seizure duration, and diffusion tensor imaging

The electrical conductivities (sigma) of freshly excised neocortex and subcortical white matter were studied in the frequency range of physiological relevance for EEG (5-1005 Hz) in 21 patients (ages 0.67 to 55 years) undergoing epilepsy neurosurgery. Surgical patients were classified as having cortical dysplasia (CD) or non-CD pathologies. Diffusion tensor imaging (DTI) for apparent diffusion coefficient (ADC) and fractional anisotropy (FA) was obtained in 9 patients. Results found that electrical conductivities in freshly excised neocortex vary significantly from patient to patient (sigma = 0.0660-0.156 S/m). Cerebral cortex from CD patients had increased conductivities compared with non-CD cases. In addition, longer seizure durations positively correlated with conductivities for CD tissue, while they negatively correlated for non-CD tissue. DTI ADC eigenvalues inversely correlated with electrical conductivity in CD and non-CD tissue. These results in a small initial cohort indicate that electrical conductivity of freshly excised neocortex from epilepsy surgery patients varies as a consequence of clinical variables, such as underlying pathology and seizure duration, and inversely correlates with DTI ADC values. Understanding how disease affects cortical electrical conductivity and ways to non-invasively measure it, perhaps through DTI, could enhance the ability to localize EEG dipoles and other relevant information in the treatment of epilepsy surgery patients.

Magnetic source imaging localizes epileptogenic zone in children with tuberous sclerosis complex

The authors assessed whether magnetoencephalography/magnetic source imaging (MEG/MSI) identified epileptogenic zones in patients with tuberous sclerosis complex (TSC). In six TSC children with focal seizures, ictal video-EEG predicted the region of resection with 56% sensitivity, 80% specificity, and 77% accuracy (p = 0.02), whereas interictal MEG/MSI fared better (100%, 94%, and 95%, respectively; p < 0.0001). Interictal MEG/MSI seems to identify epileptogenic zones more accurately in children with TSC and focal intractable epilepsy.

Three-dimensional preoperative maps of hippocampal atrophy predict surgical outcomes in temporal lobe epilepsy

The authors used surface-based anatomic mapping to detect features of hippocampal anatomy that correlated with surgical outcomes in patients undergoing surgery for mesial temporal lobe epilepsy with hippocampal sclerosis. Compared with a seizure-free group, hippocampal profiles for the non-seizure-free group had greater diffuse ipsilateral atrophy and more region-specific contralateral atrophy in the anterior, lateral hippocampus. These atrophic regions may indicate areas of increased epileptogenicity, contributing to poorer surgical outcomes.