Imaging of Amyloid-Related Imaging Abnormalities (ARIA)

Patients with Alzheimer's disease (AD) can now be treated with monoclonal antibodies aiming at clearing amyloid plaques from the brain parenchyma. Weeks after initiation of this drug therapy, patients may develop so-called amyloid-related imaging abnormalities (ARIA) on MRI. ARIA comprise vasogenic edema and leptomeningeal effusions (ARIA-E) as well as microbleeds and superficial hemosiderosis (ARIA-H). The prevalence is drug- and dose-dependent (up to 40 % of patients), the apolipoprotein E4 variant and concomitant cerebral amyloid angiopathy (CAA) increase the risk. With regard to MRI characteristics, ARIA strongly resembles the so-called inflammatory subtype of CAA (CAA-ri). While patients with CAA-ri are typically detected due to symptoms such as headaches, lethargy, confusion, and rarely epileptic seizures, around 20 % of ARIA patients show symptoms. Management of ARIA is not yet clearly established. In asymptomatic patients, discontinuation of the drug might be sufficient. KEY POINTS:   · Amyloid-related imaging abnormalities (ARIA) occur in around 20 % of patients who are treated with monoclonal antibodies against amyloid β.. · There are 2 types: ARIA-E (edema effusion) und ARIA-H (hemorrhage).. · Depending on the severity, therapy with monoclonal antibodies is either interrupted or finished.. CITATION FORMAT: · Urbach H, Linn J, Hattingen E et al. Imaging of Amyloid-Related Imaging Abnormalities (ARIA). Fortschr Röntgenstr 2024; 196: 363 - 369.

Exploring the ATN classification system using brain morphology

BACKGROUND

The NIA-AA proposed amyloid-tau-neurodegeneration (ATN) as a classification system for AD biomarkers. The amyloid cascade hypothesis (ACH) implies a sequence across ATN groups that patients might undergo during transition from healthy towards AD: A-T-N-➔A+T-N-➔A+T+N-➔A+T+N+. Here we assess the evidence for monotonic brain volume decline for this particular (amyloid-conversion first, tau-conversion second, N-conversion last) and alternative progressions using voxel-based morphometry (VBM) in a large cross-sectional MRI cohort.

METHODS

We used baseline data of the DELCODE cohort of 437 subjects (127 controls, 168 SCD, 87 MCI, 55 AD patients) which underwent lumbar puncture, MRI scanning, and neuropsychological assessment. ATN classification was performed using CSF-Aβ42/Aβ40 (A+/-), CSF phospho-tau (T+/-), and adjusted hippocampal volume or CSF total-tau (N+/-). We compared voxel-wise model evidence for monotonic decline of gray matter volume across various sequences over ATN groups using the Bayesian Information Criterion (including also ROIs of Braak stages). First, face validity of the ACH transition sequence A-T-N-➔A+T-N-➔A+T+N-➔A+T+N+ was compared against biologically less plausible (permuted) sequences among AD continuum ATN groups. Second, we evaluated evidence for 6 monotonic brain volume progressions from A-T-N- towards A+T+N+ including also non-AD continuum ATN groups.

RESULTS

The ACH-based progression A-T-N-➔A+T-N-➔A+T+N-➔A+T+N+ was consistent with cognitive decline and clinical diagnosis. Using hippocampal volume for operationalization of neurodegeneration (N), ACH was most evident in 9% of gray matter predominantly in the medial temporal lobe. Many cortical regions suggested alternative non-monotonic volume progressions over ACH progression groups, which is compatible with an early amyloid-related tissue expansion or sampling effects, e.g., due to brain reserve. Volume decline in 65% of gray matter was consistent with a progression where A status converts before T or N status (i.e., ACH/ANT) when compared to alternative sequences (TAN/TNA/NAT/NTA). Brain regions earlier affected by tau tangle deposition (Braak stage I-IV, MTL, limbic system) present stronger evidence for volume decline than late Braak stage ROIs (V/VI, cortical regions). Similar findings were observed when using CSF total-tau for N instead.

CONCLUSION

Using the ATN classification system, early amyloid status conversion (before tau and neurodegeneration) is associated with brain volume loss observed during AD progression. The ATN system and the ACH are compatible with monotonic progression of MTL atrophy.

TRIAL REGISTRATION

DRKS00007966, 04/05/2015, retrospectively registered.

Anatomical labeling of intracranial arteries with deep learning in patients with cerebrovascular disease

Brain arteries are routinely imaged in the clinical setting by various modalities, e.g., time-of-flight magnetic resonance angiography (TOF-MRA). These imaging techniques have great potential for the diagnosis of cerebrovascular disease, disease progression, and response to treatment. Currently, however, only qualitative assessment is implemented in clinical applications, relying on visual inspection. While manual or semi-automated approaches for quantification exist, such solutions are impractical in the clinical setting as they are time-consuming, involve too many processing steps, and/or neglect image intensity information. In this study, we present a deep learning-based solution for the anatomical labeling of intracranial arteries that utilizes complete information from 3D TOF-MRA images. We adapted and trained a state-of-the-art multi-scale Unet architecture using imaging data of 242 patients with cerebrovascular disease to distinguish 24 arterial segments. The proposed model utilizes vessel-specific information as well as raw image intensity information, and can thus take tissue characteristics into account. Our method yielded a performance of 0.89 macro F1 and 0.90 balanced class accuracy (bAcc) in labeling aggregated segments and 0.80 macro F1 and 0.83 bAcc in labeling detailed arterial segments on average. In particular, a higher F1 score than 0.75 for most arteries of clinical interest for cerebrovascular disease was achieved, with higher than 0.90 F1 scores in the larger, main arteries. Due to minimal pre-processing, simple usability, and fast predictions, our method could be highly applicable in the clinical setting.

Cerebral Microbleeds and Treatment Effect of Intravenous Thrombolysis in Acute Stroke: An Analysis of the WAKE-UP Randomized Clinical Trial

Background and Objectives

Cerebral microbleeds (CMBs) are common in patients with acute ischemic stroke and are associated with increased risk of intracerebral hemorrhage (ICH) after intravenous thrombolysis. Whether CMBs modify the treatment effect of thrombolysis is unknown.

Methods

We performed a prespecified analysis of the prospective randomized controlled multicenter Efficacy and Safety of MRI-Based Thrombolysis in Wake-Up Stroke (WAKE-UP) trial including patients with acute ischemic stroke with unknown time of symptom onset and diffusion-weighted imaging–fluid-attenuated inversion recovery mismatch on MRI receiving alteplase or placebo. Patients were screened and enrolled between September 2012 and June 2017 (with final follow-up in September 2017). Patients were randomized to treatment with IV thrombolysis with alteplase at 0.9 mg/kg body weight or placebo. CMB status (presence, number, and distribution) was assessed after study completion by 3 raters blinded to clinical information following a standardized protocol. Outcome measures were excellent functional outcome at 90 days, defined by modified Rankin Scale (mRS) score ≤1, and symptomatic ICH according to National Institutes of Neurological Disease and Stroke trial criteria 22 to 36 hours after treatment.

Results

Of 503 patients enrolled in the WAKE-UP trial, 459 (91.3%; 288 [63%] men) were available for analysis. Ninety-eight (21.4%) had at least 1 CMB on baseline imaging; 45 (9.8%) had exactly 1 CMB; 37 (8.1%) had 2 to 4 CMBs; and 16 (3.5%) had ≥5 CMBs. Presence of CMBs was associated with a nonsignificant increased risk of symptomatic ICH (11.2% vs 4.2%; adjusted odds ratio [OR] 2.32, 95% confidence interval [CI] 0.99–5.43, p = 0.052) but had no effect on functional outcome at 90 days (mRS score ≤1: 45.8% vs 50.7%; adjusted OR 0.99, 95% CI 0.59–1.64, p = 0.955). Patients receiving alteplase had better functional outcome (mRS score ≤1: 54.6% vs 44.6%, adjusted OR 1.61, 95% CI 1.07–2.43, p = 0.022) without evidence of heterogeneity in relation to CMB presence (p of the interactive term = 0.546). Results were similar for subpopulations with strictly lobar (presumed cerebral amyloid angiopathy related) or not strictly lobar CMB distribution.

Discussion

In the randomized-controlled WAKE-UP trial, we saw no evidence of reduced treatment effect of alteplase in patients with acute ischemic stroke with ≥1 CMBs. Additional studies are needed to determine the treatment effect of alteplase and its benefit-harm ratio in patients with a larger number of CMBs.

Trial Registration Information

ClinicalTrials.gov identifier NCT01525290; ClinicalTrialsRegister.EU identifier 2011-005906-32.

Classification of Evidence

This study provides Class II evidence that for patients with acute ischemic stroke with unknown time of onset and diffusion-weighted imaging–fluid-attenuated inversion recovery mismatch who received IV alteplase, CMBs are not significantly associated with functional outcome at 90 days.

Hyperintense acute reperfusion marker associated with hemorrhagic transformation in the WAKE-UP trial

Introduction

Hyperintense acute reperfusion marker (HARM) is an indicator of early disruption of the blood-brain-barrier. Our aim was to investigate the incidence of HARM in patients with a diffusion weighted imaging (DWI) - fluid attenuated inversion recovery (FLAIR) mismatch and determine the association between this marker and hemorrhagic complications as well as clinical outcome.

Patients and Methods

We included patients from the Efficacy and Safety of MRI-Based Thrombolysis in Wake-Up Stroke (WAKE-UP) trial who underwent baseline perfusion weighted imaging (PWI). HARM was defined as a hyperintense signal in the cerebrospinal fluid space on FLAIR imaging at 24 h after baseline imaging. We compared baseline characteristics in patients with and without HARM and investigated the association between HARM and any hemorrhagic transformation (HT) and parenchymal hematoma (PH) in a multivariate logistic regression. We also explored HARM as an independent predictor of poor outcome, defined as a modified Rankin Scale of 3-6 at 90 days.

Results

HARM was present in 14 of 223 (6%) patients with a DWI-FLAIR mismatch and baseline characteristics were similar in patients with vs without HARM. HARM showed an independent relationship with any HT (OR 6.67; 95%CI 1.72-26.58) and any PH (OR 6.92; 95%CI 1.34-29.49). The rate of HARM was similar in patients with good and poor outcome (5%, p = 0.90).

Conclusion

In the WAKE-UP trial, the incidence of HARM was only 6% at 24 h. An association was present between HARM and hemorrhagic complications, but no relationship with functional outcome was observed.

Randomized clinical trial comparing a rivaroxaban-based with an antiplatelet-based strategy for cerebral embolization after TAVR (EARTH TAVR)-a magnetic resonance imaging substudy of the GALILEO trial

Background

Cerebral embolization in patients after Transcatheter Aortic Valve Replacement (TAVR) represents a serious complication, that was related to impaired bioprosthetic leaflet motion and new-onset atrial fibrillation (AFib).

Purpose

Hereafter we present the first randomized study comparing the effect of an anticoagulation plus antiplatelet with a dual antiplatelet antithrombotic treatment in patients after TAVR on cerebral embolizations as assessed by serial cerebral magnetic resonance imaging (MRI).

Methods

The Evaluation of Cerebral Thrombembolism After TAVR (EARTH - TAVR) study was conducted as an investigator initiated substudy of the multicenter, randomized, GALILEO study. After successful TAVR, patients without indication for chronic anticoagulation were randomly assigned to rivaroxaban 10mg plus acetylsalicylic acid 75–100mg once-daily or clopidogrel 75mg plus acetylsalicylic acid 75–100mg once-daily. Cerebral MRI scans were performed pre-TAVR as a baseline, post-TAVR (within 24–48 hours after TAVR) and 90 days after TAVR. The MRI protocol included diffusion-weighted (DWI) and fluid-attenuated inversion recovery (FLAIR) imaging. Cerebral embolic lesions were evaluated by an independent cerebral MRI core lab. The primary outcome measure of this study was the occurrence and extent of cerebral embolizations as measured by total volume of new ischaemic cerebral lesions.

Results

36 patients were enrolled in the EARTH and the GALILEO study. The DWI MRI scans revealed an increase of cerebral lesions and volume post-TAVR by a median of 4.75 (95% NBCI 2.1–8.9) and 0.26cm3 (95% NBCI 0.11–0.59). On FLAIR imaging, lesion number and volume increased by a median of 3 (95% NBCI 1.5–6) and 0.1 cm3 (95% NBCI 0.04–0.31). At the 90 days MRI scan, there was no statistically significant change in cerebral lesions, if compared to the post-TAVR scan, irrespective of the treatment arm.

Conclusion

Thromboembolic events occur largely in the periinterventional phase post TAVR. Thereafter, the risk for additional cerebral embolization is low. An additional rivaroxaban therapy beyond antiplatelet inhibition did not impact on cerebral thromboembolism.

Funding Acknowledgement

Type of funding source: Private company. Main funding source(s): Bayer Pharmaceuticals

Sphenopalatine Ganglion Stimulation to Augment Cerebral Blood Flow

Background and Purpose—

Many patients with acute ischemic stroke are not eligible for thrombolysis or mechanical reperfusion therapies due to contraindications, inaccessible vascular occlusions, late presentation, or large infarct core. Sphenopalatine ganglion (SPG) stimulation to enhance collateral flow and stabilize the blood-brain barrier offers an alternative, potentially more widely deliverable, therapy.

Methods—

In a randomized, sham-controlled, double-masked trial at 41 centers in 7 countries, patients with anterior circulation ischemic stroke not treated with reperfusion therapies within 24 hours of onset were randomly allocated to active SPG stimulation or sham control. The primary efficacy outcome was improvement beyond expectations on the modified Rankin Scale of global disability at 90 days (sliding dichotomy), assessed in the modified intention-to-treat population. The initial planned sample size was 660 patients, but the trial was stopped early when technical improvements in device placement occurred, so that analysis of accumulated experience could be conducted to inform a successor trial.

Results—

Among 303 enrolled patients, 253 received at least one active SPG or sham stimulation, constituting the modified intention-to-treat population (153 SPG stimulation and 100 sham control). Age was median 73 years (interquartile range, 64–79), 52.6% were female, deficit severity on the National Institutes of Health Stroke Scale was median 11 (interquartile range, 9–15), and time from last known well median 18.6 hours (interquartile range, 14.5–22.5). For the primary outcome, improved 3-month disability beyond expectations, rates in the SPG versus sham treatment groups were 49.7% versus 40.0%; odds ratio, 1.48 (95% CI, 0.89–2.47); P =0.13. A significant treatment interaction with stroke location (cortical versus noncortical) was noted, P =0.04. In the 87 patients with confirmed cortical involvement, rates of improvement beyond expectations were 50.0% versus 27.0%; odds ratio, 2.70 (95% CI, 1.08–6.73); P =0.03. Similar response patterns were observed for all prespecified secondary efficacy outcomes. No differences in mortality or serious adverse event safety end points were observed.

Conclusions—

SPG stimulation within 24 hours of onset is safe in acute ischemic stroke. SPG stimulation was not shown to statistically significantly improve 3-month disability above expectations, though favorable outcomes were nominally higher with SPG stimulation. Beneficial effects may distinctively be conferred in patients with confirmed cortical involvement. The results of this study need to be confirmed in a larger pivotal study.

Clinical Trial Registration—

URL: https://www.clinicaltrials.gov . Unique identifier: NCT03767192.

[Acceptance of dementia diagnostics by getriatric hospital patients : Comparison of various investigation methods with emphasis on FDG-PET imaging]

BACKGROUND

The number of people with dementia is continuously rising, in hospitals as well. For the diagnostics novel methods are available but the attitude of the patients to these methods is yet unknown.

OBJECTIVE

The aim of the study was to evaluatethe opinion of geriatric hospital patients with suspected dementia on the various possible methods of diagnosing dementia, especially fluorodeoxyglucose positron emission tomography (FDG-PET). Additionally, it was assessed if there are differences in toleration between imaging of the brain and conventional diagnostics by neuropsychological testing and if information on the diagnostic methods and the patient's physical or cognitive status influence their opinion.

METHOD

Within the framework of the iDSS001 clinical trial 90 geriatric hospital patients with suspected dementia were interviewed with respect to examinations performed for diagnosing dementia, e.g. anamnesis including physical and neurological examinations, neuropsychological testing, cerebrospinal fluid analysis, magnetic resonance imaging (MRI) and FDG-PET imaging.

RESULTS

Imaging of the brain was tolerated less than anamnesis including physical and neurological examinations, neuropsychological testing and cerebrospinal fluid analysis and patients also felt they were less informed about these procedures. The generally well-accepted FDG-PET imaging procedure was received slightly better than MRI. Cognitively impaired and less depressed patients were less willing to allow repeat MRI examinations.

CONCLUSION

The results suggest that imaging of the brain is perceived by cognitively impaired hospital patients as being more burdensome than conventional diagnostics, such as neuropsychological testing. Improved care during the investigations as well as physical and organizational adjustments could increase the acceptance.

Abstract TP47: Inverse PWI/DWI Mismatch is a Typical Feature of Acute Subcortical Ischemic Stroke

Introduction / Hypothesis: Diffusion/perfusion mismatch (MM) is commonly used to assess tissue at risk in stroke patients. In small subcortical infarcts (SSI) the reverse pattern i.e. “inverse mismatch” (IM) has been shown [1]. We aimed to evaluate the frequency and characteristics of IM in a larger cohort using two different perfusion diffusion analysis approaches.

Methods: We enrolled 129 patients with SSI within 24 hours of symptom onset (1000+ study, NCT00715533) comprising 44 infarcts of the thalamus, 9 located juxtacortically, 58 in the anterior choroidal artery, 18 in the lenticulostriate territory. Lesion volumes were assessed on DWI images using AnToNIa software. To evaluate perfusion maps a time-shift insensitive technique using a block-circulant matrix for deconvolution (oSVD) [2] was employed. Perfusion lesions were evaluated on MTT and Tmax (delay >2s and >6s) maps. A perfusion/diffusion ratio of 0.7 was used to define IM and 1.3 to define mismatch (MM).

Results: Results are summarized in table1. For all types of data analysis and all time points, IM was the by far most frequent pathophysiological pattern. Obviously, IM was seen most often at Tmax>6s, but it was still clearly observed with looser thresholds (Tmax>2s, MTT). At earlier time of onset IM occurred less often, but was still the most frequent pattern (p=0.0026). No significant association between infarct location and perfusion pattern was observed

Conclusion: IM is the most common pathophysiological constellation in SSI. We hypothesize that this is due to a lack of collateral circulation in these “endstream infarcts” and that the diffusion changes in areas without perfusion deficit reflect cytotoxic mechanisms.

1. Doege CA et al. AJNR 2003;24:1355-63

2. Wu O et al. Magn Reson Med 2003;50:164-174

Abstract 104: Golden Hour-Thrombolysis by Starting Treatment Before Hospital Arrival the Pre-Hospital Acute Neurological Treatment and Optimization of Medical Care in Stroke Study (PHANTOM-S)

Objective: The effectiveness of intravenous thrombolysis in acute ischemic stroke is time dependent. The effects are likely to be highest if onset-to-treatment time (OTT) is < 60 minutes, the so called Golden-Hour. Starting thrombolysis in a specialized ambulance with a CT-scanner plus point-of-care laboratory reduced time from emergency call to treatment in the prospective controlled PHANTOM-S study. We evaluated the rate and effectiveness of Golden-Hour thrombolysis.

Methods: The stroke emergency mobile (STEMO) is staffed with a neurologist trained in emergency medicine, a paramedic and a technician. The effects of the STEMO implementation were evaluated in a prospective study comparing weeks with and without STEMO-availability. STEMO was deployed when the dispatchers suspected an acute stroke during emergency calls. If STEMO was not available (in operation or maintenance), patients received conventional care. OTT-intervals were dichotomized in either ≤60 (Golden-Hour) or > 60 minutes as well as categorized in 10-minute intervals from 0 to 270 minutes for graphical description.

Results: Overall, thrombolysis rates in ischemic stroke were 33% (200/614) when STEMO was deployed and 22% (330/1497) in conventional care (p<0.001). The proportion of Golden-Hour treatments (from all thrombolysis) was 6-fold higher after STEMO deployment (31.0%; n= 62 versus 4.9%; n=16; p<0.01). Compared to patients with longer OTT patients with Golden-Hour thrombolysis had no higher risks for 7- or 90-day mortality (adjusted ORs: 0.38, 95%-CI: 0.09-1.70 and 0.69, 95%-CI: 0.32-1.53) but were more likely to be discharged at home (adjusted OR: 1.93 95%CI: 1.09-3.41; p=0.024).

Conclusion: STEMO increased the percentage of patients treated within the Golden-Hour. This entailed no risk to patients’ safety and was associated with better short-term outcome.

Investigation of changes in body composition, metabolic profile and skeletal muscle functional capacity in ischemic stroke patients: the rationale and design of the Body Size in Stroke Study (BoSSS)

BACKGROUND

Stroke is steadily increasing in prevalence. Muscle tissue wasting and functional changes are frequently observed in stroke, but this has not been studied in detail yet. There is a lack of data to support guideline recommendations on how to target muscle wasting in stroke patients. We hypothesise that pathophysiological metabolic profiles and muscle functional and structural impairment are developing in stroke patients, which are associated with stroke severity and outcome after stroke.

METHODS

The Body Size in Stroke Study (BoSSS) is a prospective, longitudinal observation study that will explore associations between the metabolic profile, body tissue wasting and particular metabolic and functional changes in skeletal muscle tissue in stroke patients. Consecutive patients with acute stroke (n = 150) will be enrolled due to lacunar or territorial ischemic infarct in the area of the middle cerebral artery. Patients will be studied at annual intervals after 12 and 24 months. For comparison, healthy controls of similar age and patients with chronic heart failure will be used as control groups. The main objective is to study changes in body composition in stroke patients. Secondary, the study will focus on changes in insulin sensitivity of adipose tissue and skeletal muscle. Furthermore, measurements of endothelial function and peripheral blood flow will provide insight in the vascular regulation in stroke patients.

CONCLUSION

This study will be the largest observational study providing insights into the metabolic and functional changes of muscle tissue in patients with acute ischemic stroke. The new data will increase our understanding of the pathophysiologic tissue wasting in stroke disease and help to develop new therapeutic strategies.

Identifying the perfusion deficit in acute stroke with resting-state functional magnetic resonance imaging

Temporal delay in blood oxygenation level-dependent (BOLD) signals may be sensitive to perfusion deficits in acute stroke. Resting-state functional magnetic resonance imaging (rsfMRI) was added to a standard stroke MRI protocol. We calculated the time delay between the BOLD signal at each voxel and the whole-brain signal using time-lagged correlation and compared the results to mean transit time derived using bolus tracking. In all 11 patients, areas exhibiting significant delay in BOLD signal corresponded to areas of hypoperfusion identified by contrast-based perfusion MRI. Time delay analysis of rsfMRI provides information comparable to that of conventional perfusion MRI without the need for contrast agents.

Iodinated and gadolinium contrast media in computed tomography (CT) and magnetic resonance (MR) stroke imaging

Thrombolysis has become an approved therapy for acute stroke. However, many stroke patients do not benefit from such treatment, since the presently used criteria are very restrictive, notably with respect to the accepted time window. Even so, a significant rate of intracranial hemorrhage still occurs. Conventional cerebral computed tomography (CT) without contrast has been proposed as a selection tool for acute stroke patients. Recently, more modern magnetic resonance imaging (MRI) and CT techniques, referred to as diffusion- and perfusion-weighted imaging, and perfusion-CT, have been introduced. They afford a comprehensive noninvasive survey of acute stroke patients as soon as their emergency admission, with accurate demonstration of the site of arterial occlusion and its hemodynamic and pathophysiological repercussions of the brain parenchyma. The objective of this review article is to present the advantages and drawbacks of CT, using iodinated contrast, and MRI, using gadolinium, in the evaluation of acute stroke patients.

Geometric accuracy of magnetic resonance imaging of the mandibular nerve

OBJECTIVES

Magnetic resonance imaging (MRI) is not routinely used for dental implant planning. A prerequisite for dental implant planning is the accurate imaging of risk structures like the mandibular nerve. The geometric accuracy of the imaging of the mandibular nerve was investigated.

METHODS

Two human cadaver heads were scanned using MRI. Computed tomography (CT) scans of the same heads were used as a benchmark. Using a stereotactic frame, corresponding images of MRI and CT were superimposed and the concordance of the images of the mandibular nerve in MRI with those of the mandibular canal in CT was assessed.

RESULTS

The geometric accuracy of the mandibular nerve in MRI was as good as that of the mandibular canal in CT imaging.

CONCLUSIONS

MRI of the mandibular nerve is sufficiently accurate for the use of this imaging method in dental implant planning.

Artefacts in magnetic resonance imaging caused by dental material

A common problem in computer tomography (CT) based imaging of the oral cavity is artefacts caused by dental restorations. The aim of this study was to investigate whether magnetic resonance imaging (MRI) of the oral cavity would be less affected than CT by artefacts caused by typical dental restorative alloys. In order to assess the extent of artefact generation, corresponding MRI scans of the same anatomic region with and without dental metal restorations were matched using a stereotactic frame. MRI imaging of the oral and maxillofacial region could be performed without reduction of the image quality by metallic dental restorations made from titanium, gold or amalgam. Dental restorations made from titanium, gold or amalgam did not reduce the image quality of the MRI sequence used in imaging of the oral and maxillofacial region for dental implant planning. In this respect MRI is superior to CT in implant planning.

MR-Volumetrie des N. trigeminus bei Patienten mit einseitigen Gesichtsschmerzen

PURPOSE

To assess whether MRI can detect atrophy of the trigeminal nerve in patients with trigeminal neuralgia.

MATERIALS AND METHODS

A prospective MRI study was conducted in 39 patients (trigeminal neuralgia, trigeminal neuropathy, or atypical facial pain) and 25 volunteers. Using a coronal orientation (T1 Flash 3D; T2 CISS 3D), regions of interest were delineated in the cisternal part of the trigeminal nerve along the border of the nerve to calculate the volume of the nerve. The volume of the nerve was compared side-by-side in each patient (t-test, p < 0.05) and the volume difference compared between patients and volunteers.

RESULTS

The volume of the compromised trigeminal nerve in patients with trigeminal neuralgia was lower than on the contralateral healthy side, with the difference between healthy and compromised side statistically significant (p < 0.05). In all other patients and in all volunteers, no significant difference was found between the volume of the healthy and compromised nerve. The volume difference between the healthy and compromised side in patients with trigeminal neuralgia was significantly higher (p < 0.05) than in all other patients and volunteers.

CONCLUSION

Atrophy of the trigeminal nerve caused by a nerve-vessel conflict can be detected by MRI. Only patients with trigeminal neuralgia show this unilateral atrophy. Therefore, it is possible to demonstrate the result of the nerve-vessel conflict and to determine the consequences of such a conflict.

Beidseitge A.-vertebralis- Dissektion nach chiropraktischer Behandlungn konservativer Behandlungsmethoden bei Patienten mit Claudicatio spinalis

A 31-year-old woman suffered a brainstem infarction secondary to chiropractic neck manipulation. A dissection of both vertebral arteries could be demonstrated by MR tomography. This case report should alert therapists to be aware of vertebrobasilar complications after spinal manipulations.

Normale und pathologische Wasserdiffusion im Gehirn

Diffusion magnetic resonance imaging (MRI) has become an important tool in the radiologic diagnosis of diseases of the brain as it measures molecular motion of water that characterizes the microstructure of tissues. Its most important clinical use to date is the early detection of cerebral ischemia by revealing the ischemic injury shortly after vessel occlusion and simultaneously providing therapy-relevant information on the tissue at risk. Furthermore, diffusion MRI is diagnostically promising in other diseases of the brain and is thus increasingly becoming part of routine clinical protocols in the diagnosis of tumors, inflammation, trauma, demyelination, dysmyelination and neurodegeneration. Although abnormalities of diffusion are generally not pathognomonic, diffusion MRI affords information about tissue changes for specific disorders that complements information obtained with standard MR techniques and frequently shows pathology earlier. In addition, diffusion MRI can be applied to plan, guide and follow-up biopsies or resective surgery. Particularly diffusion tensor imaging (DTI), which displays the orientation of white matter fibers, holds promise for improved surgical planning. Moreover, DTI can be used to detect changes in connectivity between functional brain areas. Therefore, DTI is highly relevant not only in advancing the knowledge of white matter diseases but also in stimulating research on normal brain development and brain aging.

[Dissection of four cerebral arteries after protracted birth]

A 37-year-old woman suffered from middle cerebral artery infarction secondary to dissection of the left internal carotid artery. Nine days before, a cesarean section had been performed on her after 20 h of unsuccessful labor. Cerebral angiography at admission revealed no further vascular abnormalities. A few days later, however, the patient developed additional dissections of the right internal carotid artery and both vertebral arteries. Pregnancy, childbirth, and a history of rheumatoid arthritis in this patient may have contributed to the dissections; however, due to the unknown etiology of cervical dissections, the pathogenetic contribution of all of these factors is incompletely understood.

[Value of MRI in intracerebral and subarachnoid hemorrhage]

Intracranial hemorrhage (ICH) accounts for 15% of all strokes. In hyperacute emergency assessment, CT is the diagnostic standard for differentiating between hyperacute ICH and ischemic stroke. At this stage, MRI is considered to be of little value for the diagnosis of ICH or subarachnoidal hemorrhage (SAH). We review the current literature and characterize the role of MRI in the diagnosis of ICH and SAH as well as hyperacute stroke in general: While MRI is considered superior to CT in the diagnosis of subacute and chronic ICH/SAH, in hyperacute ICH this is still a matter of debate. MRI signal characteristics of ICH depend on hemoglobin degradation. Deoxyhemoglobin is the MRI substrate for demonstration of blood due to its paramagnetic properties causing signal loss on susceptibility weighted images (T2*-WI). Preliminary data, however, suggest that the sensitivity of modern stroke MRI protocols is sufficiently high for hyperacute ICH and SAH and may render additional information with regard to the etiology of ICH or SAH. Further interest is focused on perihemorrhagic pathophysiologic processes, which may help to improve therapeutic decision making in patients with ICH.

[Thrombolysis in cerebral ischemia. An overview]

Thrombolytic therapy for acute ischemic stroke within the 3-h time window has been approved. In the US, where FDA approval has existed for about 4 years, less than 2% of stroke patients presently receive thrombolytic therapy. This review illustrates all completed trials of intravenous and intra-arterial thrombolytic therapy for carotid artery and vertebrobasilar artery stroke and includes recommendations for therapy, diagnostic procedures and their effect on patient selection, meta-analyses, phase IV trials, and cost efficacy analyses.

Comparison of CT with diffusion-weighted MRI in patients with hyperacute stroke

Tissue changes in ischaemic stroke are detectable by diffusion-weighted MRI (DWI) within minutes of the onset of symptoms. However, in daily routine CT is still the preferred imaging modality for patients with acute stroke. Our purpose of this study was to determine how early and reliably ischaemic brain infarcts can be identified by CT and DWI. Three neuroradiologists, blinded to clinical signs but aware that they were dealing with stroke, analysed the CT and DWI of 31 patients with an acute ischaemic stroke. We calculated kappa-values to analyse inter-rater variability. The ratings were compared with follow-up studies showing the extent of the infarct. The combined assessment of all observers gave positive findings in 77.4% of all CT examinations, with kappa = 0.58. Areas of high signal were seen on all DWI studies by all observers (kappa = 1). Estimation of the extent of the infarct based on DWI yeilded kappa = 0.70 and that based on CT kappa = 0.39. DWI was much more reliable than CT in the detection of early ischaemic lesions and we believe that it should be used in acute ischaemic stroke before aggressive therapeutic intervention.

[Magnetic resonance tomography for planning dental implantation]

PROBLEM

Three-dimensional imaging diagnostics are increasingly recommended before inserting dental implants in high-risk areas and in cases of severe alveolar atrophy. Since patients are exposed to considerable radiation with computed tomography (CT), the possibilities of employing magnetic resonance imaging (MRI) of the jaw as a diagnostic imaging method before inserting dental implants were examined.

MATERIAL AND METHOD

Twelve patients and three volunteers were examined by MRI with T1-weighted, fat-suppressed sequences and conventional T1-weighted sequences. The patients wore a diagnostic splint including markers--in the form of capillaries filled with 0.025 x 10(-2) M gadolinium solution (1.5 mm in diameter)--in the planned implant's position and axis.

RESULTS

The presentation of relevant anatomic structures and the three-dimensional accuracy of the markers were judged. Metal artefacts were evaluated in vitro. The MRI of the jaw and midface represents the mandibular canal, the maxillary sinus, and other decisive anatomic structures by detailed representation of the connective tissue surrounding the bone. Artefacts of metallic fillings reduce the image quality.

CONCLUSION

Obtaining clinical findings and planning before inserting dental implants with the help of MRI can certainly be applied with toothless patients and facilitates three-dimensional planning by representing the exact location and angle of the drill tubes. Local restrictions result from metal extinction artefacts in jaws with teeth and in controls after having inserted titanium implants.

Diffusion-weighted imaging of the spine using radial k-space trajectories

INTRODUCTION

Diffusion-weighted MR imaging (DWI) of the spine requires robust imaging methods, that are insensitive to susceptibility effects caused by the transition from bone to soft tissue and motion artifacts due to breathing, swallowing, and cardiac motion. The purpose of this study was to develop a robust imaging method suitable for DWI of the spine.

METHODS AND SUBJECTS

A radial k-space spin echo sequence has been implemented, which is self-navigating because each acquisition line passes through the origin of k-space. Influence of cardiac motion and associated flow of cerebrospinal fluid is minimized by cardiac gating with a finger photoplethysmograph. The sequence has been tested on a 1.5T system. Diffusion-weighted images of six normal volunteers were acquired in the sagittal plane with 4 b values between 50 and 500 s mm(-2). Because of the symmetries of the cord, diffusion measurements in the head-foot (HF) or left-right (LR) directions were sufficient to measure the dominant effects of anisotropy.

RESULTS

The apparent diffusion coefficients (ADCs) measured, respectively, in the LR and HF directions were (0.699+/-0.050)x10(-3) and (1.805+/-0.086)x10(-3) mm(2) s(-1) in the spinal cord, (1.588+/-0.082)x10(-3) and (1.528+/-0.052)x10(-3) mm(2) s(-1) in the intervertebral disks, and (0.346+/-0.047)x10(-3) and (0.306+/-0.035)x10(-3) mm(2) s(-1) in the vertebrae of the cervicothoracic spine.

CONCLUSION

Diffusion-weighted spin echo sequences with radial trajectories in k-space provide a means of achieving robust, high quality diffusion-weighted imaging and measuring ADCs in the spine. The application of the diffusion-weighting gradients in different directions allows diffusion anisotropy to be measured.

[MRI with fat suppression in the visualization of wall hematoma in spontaneous dissection of the internal carotid artery]

PURPOSE

Comparison of different MR-examination techniques for the diagnosis of acute spontaneous internal carotid artery dissection.

PATIENTS AND METHODS

13 patients (age range 23-59 years) with symptomatic spontaneous dissection of the internal carotid artery were examined. The MRI protocol contained a transverse spin echo sequence, a time-of-flight MR-angiography and a coronal fat suppressed T1-weighted sequence. The earliest examination was performed three days after symptom onset. Follow-up extended up to 30 months. We compared the three different sequences to find out the one that demonstrated the hematoma best.

RESULTS

MR-angiography shows a narrowing of the vessel diameter in early examinations. During the subacute stage methemoglobin can obscure this finding. From the third day on fat suppressed T1-weighted images showed a hyperintense hematoma that strongly contrasted to the surrounding fatty tissue. Fat suppressed images showed a hyperintense hematoma up to 10 months after symptom onset while MRA and spin echo sequences did not.

CONCLUSIONS

Fat suppressed T1-weighted images are superior in showing vessel wall hematoma and should thus be used in the standard MR-protocol for spontaneous internal carotid artery dissection.

Iodixanol in cerebral computed tomography: a randomized, double-blind, phase-III, parallel study with iodixanol and iohexol

Iodixanol is a new nonionic dimer, isotonic with blood at all clinically relevant concentrations. Iodixanol (270 mg I/ml) was compared in a double-blind, randomized, parallel-group, phase-III study to the monomeric nonionic iohexol (300 mg I/ml) for evaluation of safety, tolerability and radiographic efficacy during cerebral CT. One hundred adult patients scheduled to undergo contrast-enhanced cerebral CT were randomly allocated to receive either iodixanol or iohexol. All completed the trial. Safety was evaluated by recording discomfort and other adverse events, tolerance by assessing intensity and incidence of discomfort. Radiographic efficacy was assessed from the diagnostic information and the radiographic density. No serious adverse events occurred. One patient (2 %) in the iodixanol group and one patient (2 %) in the iohexol group experienced a transient reddening at the neck and lower neck-line, respectively. Both contrast agents were well tolerated. One patient (2 %) in the iodixanol group and two patients (4 %) in the iohexol group experienced a sensation of warmth (discomfort) in connection with the injection. No difference between the two contrast media were noted radiographically. This comparison between iodixanol and iohexol showed both contrast media to be safe, well-tolerated and efficacious for use in cerebral CT.

[Spectrum of neurological symptoms in dissections of brain-supplying arteries]

BACKGROUND AND OBJECTIVE

Dissection of extracranial arteries that supply the brain is a common cause of ischemic stroke in youngish persons. Yet this disease, with its warning and early symptoms, is inadequately known among the population as well as doctors. This study was undertaken to demonstrate the incidence, severity and sequelae of this condition, important in both routine general and hospital practice, with particular emphasis on early signs and diagnosis.

PATIENTS AND METHODS

The data from 33 patients (20 men, 13 women, average age 42 [21-72] years) who during one year had been treated in the authors' hospital for carotid (n = 23) or vertebral (n = 10) artery dissection were analysed.

RESULTS

The admission diagnosis of dissection, based on the history and ultrasound findings was in almost all cases confirmed by magnetic resonance imaging (wall haematoma), magnetic resonance angiograhy, computed tomography-angiography or conventional angiography. Typical warning and early symptoms such as whiplash sensation unilateral pain in the throat, neck and head or Horner's syndrome were elicited in nearly 50% of patients, while known causes such as trauma or connective tissue disease were confirmed in only 27%. Neurological deficits of ischemic infarction, some of them severe, persisted in two-thirds of patients, brain death occurred in one.

CONCLUSIONS

Dissection of carotid or vertebral arteries is a statistically and medically relevant cause of stroke in youngish persons that can be diagnosed by attention to typical warning and early symptoms and the performance of noninvasive tests. The often life-threatening sequelae of possible cerebral ischemia can be diagnosed and even averted by early recognition of the cause.