Multimodality approach in cryptogenic epilepsy with focus on morphometric 3T MRI.

PURPOSE: This study aimed to investigate the potential contribution of morphometric MRI analysis in comparison to other modalities, such as MEG, SPECT and PET, in identifying the epileptogenic focus in patients with cryptogenic epilepsy. PATIENTS AND METHODS: Study inclusion was limited to epilepsy patients with a monolobar focus hypothesis, as concluded from EEG/seizure semiology and the best individual concordance rate. Feature maps, generated by the MATLAB(®) "morphometric analysis program" (MAP), were evaluated by a neuroradiologist blinded to conventional MRI and the focus hypothesis (MAP(1)). In addition, the feature maps were also interpreted by simultaneous matching conventional MRI but, again, with the reader having no knowledge of the focus hypothesis (MAP(2)). RESULTS: In 12 out of 51 patients, true-positive findings were achieved (MAP(1): sensitivity 24%; specificity 96%). The sensitivity of the MAP(1) results was superior extratemporally. After matching conventional MRI, FCD was traced in six of the 12 patients (MAP(2): sensitivity 12%; specificity 100%). MEG sensitivity was 62%. Sensitivity of interictal and ictal SPECT was 20% and 50%, respectively. PET was not as sensitive extratemporally (19%) as temporally (82%). The greatest correspondence with the best individual concordance rate was noted with PET (14/16; 88%) and MEG (8/10; 80%), followed by interictal (5/8; 63%) and ictal (9/15; 60%) SPECT. Results for MAP(1) were 53% (10/19), and 100% for MAP(2) (6/6). CONCLUSION: Although MAP sensitivity and specificity results are lower in comparison to other modalities, implementation of the technique should be considered first, before arranging any further investigations. The present study results offer guidelines for the implementation, interpretation and concordance of diagnostic procedures.

[Retrospective analysis of routine-MRI and correlation with aetiology of dementia, severity and neuropsychology in a memory-clinic population]. / Retrospektive Analyse der MRT-Routinebefunde und Korrelation mit Demenzätiologie, Schweregrad und neuropsychologischen Befunden von Patienten aus einer universitären Gedächtnisambulanz.

BACKGROUND: The contribution of potential treatable dementia aetiologies diagnosed using cerebral imaging varied considerably in previous studies and was not evaluated in a recent larger German sample of patients from a memory clinic. MATERIAL AND METHODS: MRI images of 502 patients were retrospectively reassessed. Beside the proportion of potentially treatable dementia aetiology, the extent of whole brain atrophy (semiquantitative) and vascular white matter lesions were assessed. RESULTS: Mean age of the patients was 63.7 ± 13.1 years; 49 % were female, mean MMST was 24.2 ± 5.5. In 74 % there was an agreement between the clinical dementia syndrome and MRI. 9 % (45 patients) had clearly discrepant imaging results, according to MRI criteria (21 × ischaemia, 20 × normal pressure hydrocephalus (NPH), 4 × intracerebral haemorrhage). These patients could not not be differentiated using age and MMST alone as clinical criteria. There was a significant correlation between global brain atrophy and MMST (r = -0.32; p < 0.001) and white matter lesion score (r = 0.28; p < 0.001). CONCLUSION: In 9 % there was a clear discrepancy between MRI results and the clinical syndrome diagnosis in memory-clinic patients. As known from earlier studies and current German 3 rd generation guidelines, it is reasonable to perform MRI imaging in dementia to improve the aetiological and differential diagnoses and to detect a different aetiology that can be missed using the clinical dementia criteria alone.

Alterations of intracerebral γ-aminobutyric acid (GABA) levels by titration with levetiracetam in patients with focal epilepsies.

PURPOSE: The objective of this study was to determine if levetiracetam (LEV) modulates brain γ-aminobutyric acid (GABA) in patients with epilepsy. METHODS: Occipital GABA was assessed by protein magnetic resonance spectroscopy (¹H-MRS) in 16 patients with focal epilepsy at baseline and following the initiation of oral administration of LEV as monotherapy. Responder profiles were calculated as percentage of baseline seizure frequency. Alterations of GABA/Cr (creatine) of baseline measurements compared to GABA/Cr under LEV therapy were analyzed by Student's t-test for paired samples. RESULTS: After administration of LEV, partial seizure reduction (> 50%) was noticed in 5 of 16 patients (31%; 7 of 16 (44%) patients turned out to be free of seizures. Patients with 50-100% seizure reduction under LEV titration were referred to as LEV responders. Of the 32 GABA spectra, only 22 (approximately 70%) yielded a result that met the criteria for spectral quality; therefore, GABA/Cr data from only seven patients were paired. A significant increase of GABA/Cr during titration with LEV was noted in patients responding to LEV (n = 5; p = 0.007). No differences in baseline GABA/Cr levels were detected between patients with and without previous antiepileptic treatment (p = 0.74). DISCUSSION: The increasing GABA/Cr levels under drug titration only in LEV-responding epilepsy patients suggest a more complex and indirect influence of LEV on the GABAergic system.

(1)H-MRS profile in MRI positive- versus MRI negative patients with temporal lobe epilepsy.

INTRODUCTION: The objective of this study was to quantitate and compare ipsilateral total N-acetyl aspartate (tNAA), creatine (Cr), choline (Cho), myo-inositol (m-Ins) and glutamate plus glutamine (Glx) levels in the hippocampi of patients with temporal lobe epilepsy (TLE) with and without magnetic resonance imaging (MRI) evidence for mesial temporal sclerosis (MRI positive/negative). PATIENTS AND METHODS: Twenty-three age matched healthy controls and 26 consecutive patients with unilateral TLE, based on intensive 24h video-EEG, were investigated with proton magnetic resonance spectroscopy ((1)H-MRS) (17 with unilateral hippocampal sclerosis (HS) in MRI-MRI positive; 9 MRI negative). For statistical analysis one-way analysis of variance (ANOVA) with post hoc multiple comparisons and Bonferroni correction was applied. The significance level was based on p<0.05. RESULTS: The mean tNAA level ipsilateral to the seizure focus was significantly decreased in MRI negative, respectively MRI positive patients in comparison to healthy controls (p<0.001). The lowest tNAA level was noticed in the MRI positive group (p<0.001). Statistical analysis highlighted a clear "tNAA cut-off" (95% confidence interval) between MRI positive- and MRI negative patients and healthy controls. Mean level of Glx and m-Ins was not significantly elevated or reduced. However, in individual cases a significant elevation was noticed for Glx in MRI negative patients, respectively for m-Ins in MRI positive patients. CONCLUSION: MRI negative TLE patients have a different MRS profile than MRI positive patients (HS) with marginal but significant decrease of tNAA. Our results reveal a clear "tNAA cut-off" between the groups. The value of m-Ins and Glx in focus detection in TLE patients remains controversy.

Flat panel detector angiographic CT for stent-assisted coil embolization of broad-based cerebral aneurysms.

BACKGROUND AND PURPOSE: The purpose of this work was to evaluate angiographic CT (ACT) in the combined application of a self-expanding neurovascular stent and detachable platinum coils in the management of broad-based and fusiform intracranial aneurysms. MATERIALS AND METHODS: Eleven patients harboring wide-necked intracranial aneurysms were treated with a flexible self-expanding neurovascular stent and subsequent aneurysm embolization with platinum microcoils. ACT was performed after the interventional procedure to analyze stent position and the relationship of coils to the stent. Postprocessing included multiplanar reconstructions (MPRs) and maximum intensity projections (MIPs). ACT volume datasets were postprocessed for soft tissue visualization. RESULTS: Accurate stent placement with subsequent coil occlusion of the aneurysms was feasible in all of the patients. Similar to nonsubtracted digital subtraction angiography (DSA) images, radiopaque platinum stent markers showed excellent visibility in ACT as well. The stent struts themselves, hardly visible in nonsubtracted DSA, were visible in MPRs and MIPs of ACT in all of the patients. In aneurysms larger than 10 mm in diameter, accurate stent assessment at the level of the coils was limited due to beam hardening artifacts. Postprocedural ACT in all of the patients did not reveal any evidence of procedure-related intracranial hemorrhage. CONCLUSION: ACT provides cross-sectional, 3D visualization of endovascular stents otherwise hardly visible with plain fluoroscopy. ACT enables us to accurately determine stent position, which may be helpful in complex stent-assisted aneurysm coiling procedures. However, in aneurysms larger than 10 mm in diameter, beam hardening artifacts caused by the endoaneurysmal coil package impair visibility of the stent. Further data are necessary to evaluate the usefulness of ACT in stent-assisted aneurysm coiling.

Multimodal coregistration in patients with temporal lobe epilepsy--results of different imaging modalities in lateralization of the affected hemisphere in MR imaging positive and negative subgroups.

BACKGROUND AND PURPOSE: In this study, intensive video electroencephalogram (EEG) monitoring, high-resolution MR imaging (MR imaging), proton MR spectroscopy ((1)H-MR spectroscopy) and single-photon emission CT (SPECT) were compared in patients with temporal lobe epilepsy (TLE) to evaluate lateralization of affected hemisphere with regard to bilateral affection and postoperative outcome. PATIENTS AND METHODS: Recall ratio of each technique for indicating the affected hemisphere was determined in 49 patients with TLE. Postoperative outcome was established by Engel classification. RESULTS: Twenty-two of 25 patients with TLE with evidence for hippocampal sclerosis in MR imaging (MR imaging-positive) were graded as unilateral by EEG findings whereas 3 were classified as bilateral. Fourteen of 24 MR imaging-negative patients were graded as unilateral by EEG and 10 as bitemporal. (1)H-MR spectroscopy indicated concordant lateralization to EEG in 82% of MR imaging-positive patients and 71% of MR imaging-negative patients and to SPECT in 84% of MR imaging-positive patients and 67% of MR imaging-negative patients with TLE. In unilateral TLE, the concordance rate of both modalities was 74% in MR imaging-positive patients and 67% in MR imaging-negative patients. Contralateral findings to EEG focus were found in 28% by (1)H-MR spectroscopy and in 27% by SPECT. Concordant findings to the operated side of different modalities revealed a clear tendency (P = .08) for a better postoperative outcome compared with bitemporal or contralateral findings. CONCLUSION: Our data demonstrate that multimodal imaging in patients with TLE improves lateralization of affected hemispheres, especially in patients without pathologic findings in MR imaging, and indicates bilateral effect, which is important to identify patients who will benefit from surgery.

Magnetic resonance spectroscopic imaging for visualization of the infiltration zone of glioma.

BACKGROUND AND PURPOSE: In conventional MR imaging, it is often difficult to delineate the heterogeneous structure of gliomas. Proton magnetic resonance spectroscopic imaging ((1)H-MRSI) is a noninvasive tool for investigating the spatial distribution of metabolic changes in brain lesions. The aim of this study was to assess the improvements in delineation of gliomas based on segmentation of metabolic changes measured with (1)H-MRSI. MATERIAL AND METHODS: Twenty patients with gliomas (WHO grade II and III) were examined using a standard (1)H-MRSI sequence. Metabolic maps for choline (Cho), N-acetyl-aspartate (NAA) and Cho/NAA ratios were calculated and segmented based on the assumption of a Gaussian distribution of the Cho/NAA values for normal brain. Areas of hyperintensity on T2-weighted (T2w) MR images were compared with the areas of the segmented tumor on Cho/NAA maps. Stereotactic biopsies were obtained from the MRSI/T2w difference areas. RESULTS: In all patients, the segmented MRSI tumor areas were greater than the T2w hyperintense areas, on average, by 20% (range 6-34%). In nine patients, biopsy sampling from the MRSI/T2w difference areas showed tumor infiltration ranging from 4-17% (mean 9%) tumor cells, in the areas detected only by MRSI. DISCUSSION AND CONCLUSION: Our method for automated segmentation of the lesion-related metabolic changes achieved significantly improved delineation for gliomas compared to routine clinical methods. We demonstrate that this method can improve delineation of tumor borders compared to routine imaging strategies in clinics. Metabolic images of the segmented tumor may thus be helpful for therapeutic planning.

In vivo quantification of intracerebral GABA by single-voxel (1)H-MRS-How reproducible are the results?

Gamma aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the human brain. It plays a decisive role in a variety of nervous system disorders, such as anxiety disorders, epilepsy, schizophrenia, insomnia, and many others. The reproducibility of GABA quantification results obtained with a single-voxel spectroscopy J-difference editing sequence with Point Resolved Spectroscopy localization (MEGA-PRESS) was determined on a 3.0 Tesla MR scanner in healthy adults. Eleven volunteers were measured in long- and short-term intervals. Intra- and inter-subject reproducibility were evaluated. Internal referencing of GABA+ to total creatine (tCr) and water (H(2)O), as well as two different post-processing methods for the evaluation (signal integration and time-domain fitting) were compared. In all subjects lower coefficient of variation and therefore higher reproducibility can be observed for fitting compared to integration. The GABA+/tCr ratio performs better than the GABA+/H(2)O ratio or GABA+ without internal referencing for both fitting and integration (GABA+/tCr: 13.3% and 17.0%; GABA+/H(2)O: 15.0% and 17.8%; GABA+: 19.2% and 21.7%). Four-day measurements on three subjects showed higher intra- than inter-subject reproducibility (GABA+/tCr approximately 10-12%). With a coefficient of variation of about 13% for inter-subject and 10-12% for intra-subject variability of GABA+/tCr, this technique seems to be a precise tool that can detect GABA confidently. The results of this study show the reproducibility limitations of GABA quantification in vivo, which are necessary for further clinical studies.

Multi-voxel magnetic resonance spectroscopy at 3 T in patients with idiopathic generalised epilepsy.

PURPOSE: The objective of our study was to gain further insight into the extent of local metabolic alterations in patients with idiopathic generalised epilepsy (IGE), respectively, the subgroup with generalised tonic-clonic seizures (GTCS). The extent of regional metabolic involvement perhaps indicates the key structures in generation of seizures and involvement of specific network of dysfunction. METHODS: Using the multi-voxel technique at a 3 T MRI Scanner metabolite levels of 25 age-matched healthy controls and 18 patients with GTCS were obtained from the basal ganglia, insular cortex, cingulum, hippocampus and along both hemispheres in the fronto-parietal white and grey matter. RESULTS: Group analysis of GTCS patients versus healthy controls revealed significant (p < 0.05) decrease of tNAA in the cortex of the central region and cingulum, but also in the thalami. Glx was elevated broadly in both hemispheres, in particular in central region, cingulum, insular cortex and left putamen, yet also in the right thalamus. Cho and mI demonstrated a significant coincidental decrease pronounced in the grey and white matter of the central region. Significant metabolic correlation (p ≤ 0.05) based on tNAA, respectively, Glx occurred between the thalamus and the central region, cingulum, putamen and medial frontal cortex. In patients with > 2 tonic-clonic seizures in the last 12 months a trend towards higher Glx and lower tNAA levels was observed. DISCUSSION: Our results demonstrate the altered metabolic interconnection of cerebral anatomic regions in patients with GTCS, in particular the major role of basal ganglia-central region relay in seizure generation.

Flat-panel detector volumetric CT for visualization of subarachnoid hemorrhage and ventricles: preliminary results compared to conventional CT.

INTRODUCTION: The aim of this study was to compare flat-panel volumetric CT (VCT) to conventional CT (cCT) in the visualization of the extent of subarachnoid hemorrhage (SAH) and the width of the ventricles in patients with acute SAH. METHODS: Included in the study were 22 patients with an acutely ruptured cerebral aneurysm who received VCT during coil embolization. VCT image quality, the extent of SAH (using a modified Fisher score and total slice number with SAH visible) and the width of the ventricles (Evans index) were evaluated by two experienced neuroradiologists (RAD1 and RAD2) and compared to the findings on cCT. Ten patients undergoing VCT for reasons other than SAH served as negative controls. RESULTS: Interobserver agreement in rating image quality was excellent for cCT (Kendall W value 0.94) and good for VCT (0.74). SAH was identified by RAD1 and RAD2 on VCT images in all patients. The modified Fisher scores underestimated the extent of SAH on VCT images in comparison with cCT images. Pearson's correlation coefficient (r) regarding the number of image slices with SAH visible on cCT images compared with the number on VCT images was 0.85 for RAD1 and 0.84 for RAD2. The r value for the degree of interobserver agreement for the number of slices with SAH visible was 0.99 for cCT, and 0.95 for VCT images (n=19), respectively. The width of the ventricles measured in terms of the Evans Index showed excellent concordance between the modalities (r=0.81 vs. 0.82). CONCLUSION: Our preliminary results indicate that VCT is helpful in evaluating SAH in the angiography suite. Additionally, reliable evaluation of ventricle width is feasible. However, there are limitations with regard to the visibility of SAH on VCT images in comparison to cCT images.

Flat panel detector angiographic CT in the management of aneurysmal rupture during coil embolization.

Angiographic CT (ACT) produces CT-like images within minutes in the angiography suite. We present the cases of 2 patients with intraprocedural aneurysmal rupture in which ACT enabled the neuroradiologist to rapidly assess the extent of bleeding during endovascular treatment. Additionally, ACT revealed pronounced rebleeding within the time between conventional CT and onset of treatment. In the management of aneurysmal rupture during coil embolization, ACT may be a valuable adjunct.