Quantitative magnetic resonance imaging of the brachial plexus shows specific changes in nerve architecture in chronic inflammatory demyelinating polyneuropathy, multifocal motor neuropathy and motor neuron disease.

BACKGROUND: The immunological pathophysiologies of chronic inflammatory demyelinating polyneuropathy (CIDP) and multifocal motor neuropathy (MMN) differ considerably, but neither has been elucidated completely. Quantitative magnetic resonance imaging (MRI) techniques such as diffusion tensor imaging, T2 mapping, and fat fraction analysis may indicate in vivo pathophysiological changes in nerve architecture. Our study aimed to systematically study nerve architecture of the brachial plexus in patients with CIDP, MMN, motor neuron disease (MND) and healthy controls using these quantitative MRI techniques. METHODS: We enrolled patients with CIDP (n = 47), MMN (n = 29), MND (n = 40) and healthy controls (n = 10). All patients underwent MRI of the brachial plexus and we obtained diffusion parameters, T2 relaxation times and fat fraction using an automated processing pipeline. We compared these parameters between groups using a univariate general linear model. RESULTS: Fractional anisotropy was lower in patients with CIDP compared to healthy controls (p < 0.001), patients with MND (p = 0.010) and MMN (p < 0.001). Radial diffusivity was higher in patients with CIDP compared to healthy controls (p = 0.015) and patients with MND (p = 0.001) and MMN (p < 0.001). T2 relaxation time was elevated in patients with CIDP compared to patients with MND (p = 0.023). Fat fraction was lower in patients with CIDP and MMN compared to patients with MND (both p < 0.001). CONCLUSION: Our results show that quantitative MRI parameters differ between CIDP, MMN and MND, which may reflect differences in underlying pathophysiological mechanisms.

Timing of procedural stroke and death in asymptomatic patients undergoing carotid endarterectomy: individual patient analysis from four RCTs.

BACKGROUND: The effectiveness of carotid endarterectomy (CEA) for stroke prevention depends on low procedural risks. The aim of this study was to assess the frequency and timing of procedural complications after CEA, which may clarify underlying mechanisms and help inform safe discharge policies. METHODS: Individual-patient data were obtained from four large carotid intervention trials (VACS, ACAS, ACST-1 and GALA; 1983-2007). Patients undergoing CEA for asymptomatic carotid artery stenosis directly after randomization were used for the present analysis. Timing of procedural death and stroke was divided into intraoperative day 0, postoperative day 0, days 1-3 and days 4-30. RESULTS: Some 3694 patients were included in the analysis. A total of 103 patients (2·8 per cent) had serious procedural complications (18 fatal strokes, 68 non-fatal strokes, 11 fatal myocardial infarctions and 6 deaths from other causes) [Correction added on 20 April, after first online publication: the percentage value has been corrected to 2·8]. Of the 86 strokes, 67 (78 per cent) were ipsilateral, 17 (20 per cent) were contralateral and two (2 per cent) were vertebrobasilar. Forty-five strokes (52 per cent) were ischaemic, nine (10 per cent) haemorrhagic, and stroke subtype was not determined in 32 patients (37 per cent). Half of the strokes happened on the day of CEA. Of all serious complications recorded, 44 (42·7 per cent) occurred on day 0 (20 intraoperative, 17 postoperative, 7 with unclear timing), 23 (22·3 per cent) on days 1-3 and 36 (35·0 per cent) on days 4-30. CONCLUSION: At least half of the procedural strokes in this study were ischaemic and ipsilateral to the treated artery. Half of all procedural complications occurred on the day of surgery, but one-third after day 3 when many patients had been discharged.

ANTECEDENTES: La efectividad de la endarterectomía carotídea (carotid endarterectomy, CEA) en la prevención de un accidente cerebrovascular depende de que este procedimiento tenga pocos riesgos. El objetivo de este estudio fue evaluar la frecuencia y el momento de aparición de las complicaciones tras una CEA, lo que podría clarificar los mecanismos subyacentes y ayudar a establecer una política de altas hospitalarias segura. MÉTODOS: Se utilizaron los datos de los pacientes incluidos en cuatro grandes ensayos de intervención carotídea (VACS, ACAS, ACST-1 y GALA; 1983-2007). Para el presente análisis se utilizaron los datos de pacientes sometidos a CEA por estenosis de la arteria carótida asintomática recogidos inmediatamente tras la aleatorización. Se consideraron diferentes intervalos entre el procedimiento, la muerte o el accidente cerebrovascular: intraoperatorio día 0, postoperatorio día 0, postoperatorio días 1-3 y postoperatorio días 4-30. RESULTADOS: En el análisis se incluyeron 3.694 pacientes. Se detectaron complicaciones graves relacionadas con el procedimiento en 103 (2,8%) pacientes (18 accidentes cerebrovasculares fatales, 68 accidentes cerebrovasculares no fatales, 11 infartos de miocardio fatales y 6 muertes por otras causas). De los 86 accidentes cerebrovasculares, 67 (78%) fueron ipsilaterales, 17 (20%) contralaterales y dos (2%) vertebrobasilares. Los accidentes cerebrovasculares fueron isquémicos en 45 (52%) casos, hemorrágicos en 9 (10%) y no se pudo determinar el subtipo de ictus en 32 (37%). La mitad de los accidentes cerebrovasculares ocurrieron el día de la CEA. De todas las complicaciones graves registradas, 44 (43%) ocurrieron en el día 0 (20 intraoperatorias, 17 postoperatorias y 7 en períodos poco definidos), 23 (22%) entre los días 1-3 y 36 (35%) entre los días 4-30. CONCLUSIÓN: En este estudio, al menos la mitad de los accidentes cerebrovasculares relacionados con la CEA fueron isquémicos e ipsilaterales respecto a la arteria tratada. La mitad de todas las complicaciones de la CEA ocurrieron el día de la cirugía, pero un tercio de los casos se presentaron después del día 3, cuando muchos pacientes ya habían sido dados de alta.

A comparative study of brachial plexus sonography and magnetic resonance imaging in chronic inflammatory demyelinating neuropathy and multifocal motor neuropathy.

BACKGROUND AND PURPOSE: To compare the performance of neuroimaging techniques, i.e. high-resolution ultrasound (HRUS) and magnetic resonance imaging (MRI), when applied to the brachial plexus, as part of the diagnostic work-up of chronic inflammatory demyelinating neuropathy (CIDP) and multifocal motor neuropathy (MMN). METHODS: Fifty-one incident, treatment-naive patients with CIDP (n = 23) or MMN (n = 28) underwent imaging of the brachial plexus using (i) a standardized MRI protocol to assess enlargement or T2 hyperintensity and (ii) bilateral HRUS to determine the extent of nerve (root) enlargement. RESULTS: We found enlargement of the brachial plexus in 19/51 (37%) and T2 hyperintensity in 29/51 (57%) patients with MRI and enlargement in 37/51 (73%) patients with HRUS. Abnormal results were only found in 6/51 (12%) patients with MRI and 12/51 (24%) patients with HRUS. A combination of the two imaging techniques identified 42/51 (83%) patients. We found no association between age, disease duration or Medical Research Council sum-score and sonographic nerve size, MRI enlargement or presence of T2 hyperintensity. CONCLUSIONS: Brachial plexus sonography could complement MRI in the diagnostic work-up of patients with suspected CIDP and MMN. Our results indicate that combined imaging studies may add value to the current diagnostic consensus criteria for chronic inflammatory neuropathies.

Upper Extremity Blood Pressure Difference in Patients Undergoing Carotid Revascularisation.

INTRODUCTION: Blood pressure (BP) regulation is important in patients with carotid artery atherosclerotic disease. Concomitant subclavian artery stenosis (SAS) might lead to an underestimation of the true systemic BP in the monitoring of these patients. This study aimed to assess the prevalence of the inter-arm BP difference in patients undergoing carotid intervention and its association with ipsilateral significant subclavian stenosis and clinical outcome. METHODS: Bilateral BP measurements and vascular imaging (CTA and MRA) of both subclavian arteries and the innominate artery were assessed in 182 symptomatic patients with carotid artery stenosis undergoing revascularisation in the International Carotid Stenting Study (ICSS). Data were separately analysed according to previously described cutoff values for systolic BP (SBP) differences of ≥10 and <15 mmHg, ≥15 and <20 mmHg, or ≥20 mmHg. Significant SAS was defined as a >50% diameter reduction. RESULTS: Of the 182 patients, 39 (21%) showed an inter-arm difference in SBP >15 mmHg. The mean inter-arm SBP difference associated with ipsilateral SAS was 14 mmHg. SAS was present in 21/182 (12%) patients. Only two patients (1%) had bilateral stenotic disease. An inter-arm SBP difference of ≥20 mmHg was associated with unilateral SAS (RR 11.8; 95% CI 3.2-43.1) with a sensitivity of 23% and a specificity of 98%. Patients were followed up for a median of 4.0 years (IQR 3.0-6.0; maximum 7.5). Risk of stroke or death during follow-up was 20.0% (95% CI 11.1-28.9) in patients with, and 15.1% (95% CI 12.3-17.9) in patients without SAS (p = .561). The hospital stay was longer in patients with significant SAS (5.0 days, SD 4.9 vs. 2.7 days, SD 4.3, p = .035). CONCLUSION: The present study is the first to affirm the clinical need for the measurement of inter-arm BP differences in patients undergoing carotid revascularisation, especially in the post-operative phase in the prevention of cerebral hyperperfusion.

Definition of common carotid wall thickness affects risk classification in relation to degree of internal carotid artery stenosis: the Plaque At RISK (PARISK) study.

BACKGROUND: Mean or maximal intima-media thickness (IMT) is commonly used as surrogate endpoint in intervention studies. However, the effect of normalization by surrounding or median IMT or by diameter is unknown. In addition, it is unclear whether IMT inhomogeneity is a useful predictor beyond common wall parameters like maximal wall thickness, either absolute or normalized to IMT or lumen size. We investigated the interrelationship of common carotid artery (CCA) thickness parameters and their association with the ipsilateral internal carotid artery (ICA) stenosis degree. METHODS: CCA thickness parameters were extracted by edge detection applied to ultrasound B-mode recordings of 240 patients. Degree of ICA stenosis was determined from CT angiography. RESULTS: Normalization of maximal CCA wall thickness to median IMT leads to large variations. Higher CCA thickness parameter values are associated with a higher degree of ipsilateral ICA stenosis (p < 0.001), though IMT inhomogeneity does not provide extra information. When the ratio of wall thickness and diameter instead of absolute maximal wall thickness is used as risk marker for having moderate ipsilateral ICA stenosis (>50%), 55 arteries (15%) are reclassified to another risk category. CONCLUSIONS: It is more reasonable to normalize maximal wall thickness to end-diastolic diameter rather than to IMT, affecting risk classification and suggesting modification of the Mannheim criteria. TRIAL REGISTRATION: Clinical trials.gov NCT01208025 .

Rationale and design of the Edwards SAPIEN-3 periprosthetic leakage evaluation versus Medtronic CoreValve in transfemoral aortic valve implantation (ELECT) trial : A randomised comparison of balloon-expandable versus self-expanding transcatheter aortic valve prostheses.

BACKGROUND AND OBJECTIVES: Periprosthetic aortic regurgitation (PPR) after transcatheter aortic valve implantation (TAVI) remains an important issue associated with impaired long-term outcomes. The current randomised study aims to evaluate potential differences between the balloon-expandable Edwards SAPIEN-3 and the self-expanding Medtronic CoreValve system with the main focus on post-TAVI PPR by means of novel imaging endpoints, and an additional focus on other clinical endpoints. ENDPOINTS: The primary endpoint of this study is quantitative assessment of the severity of post-procedural PPR using cardiac magnetic resonance imaging. Several other novel imaging modalities (X-ray contrast angiography, echocardiography) are used as secondary imaging modalities for the assessment of PPR following TAVI. Secondary objectives of the study include clinical outcomes such as cerebral and kidney injury related to TAVI, and quality of life. METHODS AND DESIGN: The ELECT study is a single-centre, prospective, two-armed randomised controlled trial. For the purpose of this study, 108 consecutive adult patients suitable for transfemoral TAVI will be randomly allocated to receive the SAPIEN-3 (n = 54) or the CoreValve system (n = 54). DISCUSSION: The ELECT trial is the first randomised controlled trial to quantitatively compare the extent of post-TAVI PPR between the SAPIEN-3 and CoreValve. Furthermore, it will evaluate potential differences between the two prostheses with regard to mid-term clinical outcome and quality of life.

Misinterpretation of ischaemic infarct location in relationship to the cerebrovascular territories.

PURPOSE: Cerebral perfusion territories are known to vary widely among individuals. This may lead to misinterpretation of the symptomatic artery in patients with ischaemic stroke to a wrong assumption of the underlying aetiology being thromboembolic or hypoperfusion. The aim of the present study was to investigate such potential misinterpretation with territorial arterial spin labelling (T-ASL) by correlating infarct location with imaging of the perfusion territory of the carotid arteries or basilar artery. MATERIALS AND METHODS: 223 patients with subacute stroke underwent MRI including structural imaging scans to determine infarct location, time-of-flight MR angiography (MRA) to determine the morphology of the circle of Willis and T-ASL to identify the perfusion territories of the internal carotid arteries, and basilar artery. Infarct location and the perfusion territory of its feeding artery were classified with standard MRI and MRA according to a perfusion atlas, and were compared to the classification made according to T-ASL. RESULTS: A total of 149 infarctions were detected in 87 of 223 patients. 15 out of 149 (10%) infarcts were erroneously attributed to a single perfusion territory; these infarcts were partly located in the originally determined perfusion territory but proved to be localised in the border zone with the adjacent perfusion territory instead. 12 out of 149 (8%) infarcts were misclassified with standard assessments and were not located in the original perfusion territory. CONCLUSIONS: T-ASL with territorial perfusion imaging may provide important additional information for classifying the symptomatic brain-feeding artery when compared to expert evaluation with MRI and MRA.

Cerebrospinal fluid volumetric MRI mapping as a simple measurement for evaluating brain atrophy.

OBJECTIVES: To assess whether volumetric cerebrospinal fluid (CSF) MRI can be used as a surrogate for brain atrophy assessment and to evaluate how the T2 of the CSF relates to brain atrophy. METHODS: Twenty-eight subjects [mean age 64 (sd 2) years] were included; T1-weighted and CSF MRI were performed. The first echo data of the CSF MRI sequence was used to obtain intracranial volume, CSF partial volume was measured voxel-wise to obtain CSF volume (VCSF) and the T2 of CSF (T2,CSF) was calculated. The correlation between VCSF/T2,CSF and brain atrophy scores [global cortical atrophy (GCA) and medial temporal lobe atrophy (MTA)] was evaluated. RESULTS: Relative total, peripheral subarachnoidal, and ventricular VCSF increased significantly with increased scores on the GCA and MTA (R = 0.83, 0.78 and 0.78 and R = 0.72, 0.62 and 0.86). Total, peripheral subarachnoidal, and ventricular T2 of the CSF increased significantly with higher scores on the GCA and MTA (R = 0.72, 0.70 and 0.49 and R = 0.60, 0.57 and 0.41). CONCLUSION: A fast, fully automated CSF MRI volumetric sequence is an alternative for qualitative atrophy scales. The T2 of the CSF is related to brain atrophy and could thus be a marker of neurodegenerative disease. KEY POINTS: • A 1:11 min CSF MRI volumetric sequence can evaluate brain atrophy. • CSF MRI provides accurate atrophy assessment without partial volume effects. • CSF MRI data can be processed quickly without user interaction. • The measured T 2 of the CSF is related to brain atrophy.

Cerebellar cortical infarct cavities and vertebral artery disease.

INTRODUCTION: Cerebellar cortical infarct cavities are a newly recognised entity associated with atherothromboembolic cerebrovascular disease and worse physical functioning. We aimed to investigate the relationship of cerebellar cortical infarct cavities with symptomatic vertebrobasilar ischaemia and with vascular risk factors. METHODS: We evaluated the MR images of 46 patients with a recent vertebrobasilar TIA or stroke and a symptomatic vertebral artery stenosis ≥50 % from the Vertebral Artery Stenting Trial (VAST) for the presence of cerebellar cortical infarct cavities ≤1.5 cm. At inclusion in VAST, data were obtained on age, sex, history of vertebrobasilar TIA or stroke, and vascular risk factors. Adjusted risk ratios were calculated with Poisson regression analyses for the relation between cerebellar cortical infarct cavities and vascular risk factors. RESULTS: Sixteen out of 46 (35 %) patients showed cerebellar cortical infarct cavities on the initial MRI, and only one of these 16 patients was known with a previous vertebrobasilar TIA or stroke. In patients with symptomatic vertebrobasilar ischaemia, risk factor profiles of patients with cerebellar cortical infarct cavities were not different from patients without these cavities. CONCLUSION: Cerebellar cortical infarct cavities are seen on MRI in as much as one third of patients with recently symptomatic vertebral artery stenosis. Since patients usually have no prior history of vertebrobasilar TIA or stroke, cerebellar cortical infarct cavities should be added to the spectrum of common incidental brain infarcts visible on routine MRI.

Age-related changes in brain hemodynamics; A calibrated MRI study.

INTRODUCTION: Blood oxygenation-level dependent (BOLD) magnetic resonance imaging signal changes in response to stimuli have been used to evaluate age-related changes in neuronal activity. Contradictory results from these types of experiments have been attributed to differences in cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2 ). To clarify the effects of these physiological parameters, we investigated the effect of age on baseline CBF and CMRO2 . MATERIALS AND METHODS: Twenty young (mean ± sd age, 28 ± 3 years), and 45 older subjects (66 ± 4 years) were investigated. A dual-echo pseudocontinuous arterial spin labeling (ASL) sequence was performed during normocapnic, hypercapnic, and hyperoxic breathing challenges. Whole brain and regional gray matter values of CBF, ASL cerebrovascular reactivity (CVR), BOLD CVR, oxygen extraction fraction (OEF), and CMRO2 were calculated. RESULTS: Whole brain CBF was 49 ± 14 and 40 ± 9 ml/100 g/min in young and older subjects respectively (P < 0.05). Age-related differences in CBF decreased to the point of nonsignificance (B=-4.1, SE=3.8) when EtCO2 was added as a confounder. BOLD CVR was lower in the whole brain, in the frontal, in the temporal, and in the occipital of the older subjects (P<0.05). Whole brain OEF was 43 ± 8% in the young and 39 ± 6% in the older subjects (P = 0.066). Whole brain CMRO2 was 181 ± 60 and 133 ± 43 µmol/100 g/min in young and older subjects, respectively (P<0.01). DISCUSSION: Age-related differences in CBF could potentially be explained by differences in EtCO2 . Regional CMRO2 was lower in older subjects. BOLD studies should take this into account when investigating age-related changes in neuronal activity.

The use of (18)F-FDG PET to differentiate progressive disease from treatment induced necrosis in high grade glioma.

In the follow-up of patients treated for high grade glioma, differentiation between progressive disease (PD) and treatment-induced necrosis (TIN) is challenging. The purpose of this study is to evaluate the diagnostic accuracy of FDG PET for the differentiation between TIN and PD after high grade glioma treatment. We retrospectively identified patients between January 2011 and July 2013 that met the following criteria: age >18; glioma grade 3 or 4; treatment with radiotherapy or chemoradiotherapy; new or progressive enhancement on post treatment MRI; FDG PET within 4 weeks of MRI. Absolute and relative (to contralateral white matter) values of SUVmax and SUVpeak were determined in new enhancing lesions on MRI. The outcome of PD or TIN was determined by neurosurgical biopsy/resection, follow-up MRI, or clinical deterioration. The association between FDG PET and outcome was analyzed with univariate logistic regression and ROC analysis for: all lesions, lesions >10, >15, and >20 mm. We included 30 patients (5 grade 3 and 25 grade 4), with 39 enhancing lesions on MRI. Twenty-nine lesions represented PD and 10 TIN. Absolute and relative values of SUVmax and SUVpeak showed no significant differences between PD and TIN. ROC analysis showed highest AUCs for relative SUVpeak in all lesion sizes. Relative SUVpeak for lesions >20 mm showed reasonable discriminative properties [AUC 0.69 (0.41-0.96)]. FDG PET has reasonable discriminative properties for differentiation of PD from TIN in high grade gliomas larger than 20 mm. Overall diagnostic performance is insufficient to guide clinical decision-making.

Simultaneous quantitative assessment of cerebral physiology using respiratory-calibrated MRI and near-infrared spectroscopy in healthy adults.

BACKGROUND: Functional near-infrared spectroscopy (fNIRS) and functional MRI (fMRI) are non-invasive techniques used to relate activity in different brain regions to certain tasks. Respiratory calibration of the blood oxygen level dependent (BOLD) signal, and combined fNIRS-fMRI approaches have been used to quantify physiological subcomponents giving rise to the BOLD signal. A comparison of absolute oxygen metabolism parameters between MRI and NIRS, using spatially resolved (SRS) NIRS and respiratory calibrated MRI, could yield additional insight in the physiology underlying activation. MATERIALS AND METHODS: Changes in the BOLD signal, cerebral blood flow (CBF), and oxygen saturation (SO2) were derived from a single MRI sequence during a respiratory challenge in healthy volunteers. These changes were compared to SO2 obtained by a single probe SRS NIRS setup. In addition, concentration changes in oxygenated (O2Hb), deoxygenated (HHb), and total haemoglobin (tHb), obtained by NIRS, were compared to the parameters obtained by MRI. RESULTS: NIRS SO2 correlated with end-tidal CO2 (0.83, p<0.0001), the BOLD signal (0.82, p<0.0001), CBF (0.85, p<0.0001), and also MRI SO2 (0.82, p<0.0001). The BOLD signal correlated with NIRS HHb (-0.76, p<0.0001), O2Hb (0.41, p=0.001), and tHb (r=0.32, p=0.01). CONCLUSIONS: Good correlations show that changes in cerebral physiology, following a respiratory challenge, go hand in hand with changes in the BOLD signal, CBF, O2Hb, HHb, NIRS SO2, and MRI SO2. Out of all NIRS derived parameters, the SO2 showed the best correlation with the BOLD signal.

Non-invasive MRI measurements of venous oxygenation, oxygen extraction fraction and oxygen consumption in neonates.

BACKGROUND AND PURPOSE: Brain oxygen consumption reflects neuronal activity and can therefore be used to investigate brain development or neuronal injury in neonates. In this paper we present the first results of a non-invasive MRI method to evaluate whole brain oxygen consumption in neonates. MATERIALS AND METHODS: For this study 51 neonates were included. The T1 and T2 of blood in the sagittal sinus were fitted using the 'T2 prepared tissue relaxation inversion recovery' pulse sequence (T2-TRIR). From the T1 and the T2 of blood, the venous oxygenation and the oxygen extraction fraction (OEF) were calculated. The cerebral metabolic rate of oxygen (CMRO2) was the resultant of the venous oxygenation and arterial spin labeling whole brain cerebral blood flow (CBF) measurements. RESULTS: Venous oxygenation was 59±14% (mean±sd), OEF was 40±14%, CBF was 14±5ml/100g/min and CMRO2 was 30±12µmol/100g/min. The OEF in preterms at term-equivalent age was higher than in the preterms and in the infants with hypoxic-ischemic encephalopathy (p<0.01). The OEF, CBF and CMRO2 increased (p<0.01, <0.05 and <0.01, respectively) with postnatal age. CONCLUSION: We presented an MRI technique to evaluate whole-brain oxygen consumption in neonates non-invasively. The measured values are in line with reference values found by invasive measurement techniques. Preterms and infants with HIE demonstrated significant lower oxygen extraction fraction than the preterms at term-equivalent age. This could be due to decreased neuronal activity as a reflection of brain development or as a result of tissue damage, increased cerebral blood flow due to immature or impaired autoregulation, or could be caused by differences in postnatal age.

Increased Intracranial Arterial Pulsatility and Microvascular Brain Damage in Pseudoxanthoma Elasticum.

BACKGROUND AND PURPOSE: Carotid siphon calcification might contribute to the high prevalence of cerebrovascular disease in pseudoxanthoma elasticum through increased arterial flow pulsatility. This study aimed to compare intracranial artery flow pulsatility, brain volumes, and small-vessel disease markers between patients with pseudoxanthoma elasticum and controls and the association between arterial calcification and pulsatility in pseudoxanthoma elasticum. MATERIALS AND METHODS: Fifty patients with pseudoxanthoma elasticum and 40 age- and sex-matched controls underwent 3T MR imaging, including 2D phase-contrast acquisitions for flow pulsatility in the assessment of ICA and MCA and FLAIR acquisitions for brain volumes, white matter lesions, and infarctions. All patients with pseudoxanthoma elasticum underwent CT scanning to measure siphon calcification. Flow pulsatility (2D phase-contrast), brain volumes, white matter lesions, and infarctions (3D T1 and 3D T2 FLAIR) were compared between patients and controls. The association between siphon calcification and pulsatility in pseudoxanthoma elasticum was tested with linear regression models. RESULTS: Patients with pseudoxanthoma elasticum (mean age, 57 [SD, 12] years; 24 men) had significantly higher pulsatility indexes (1.05; range, 0.94-1.21 versus 0.94; range, 0.82-1.04; P = .02), lower mean GM volumes (597 [SD, 53] mL versus 632 [SD, 53] mL; P < .01), more white matter lesions (2.6; range, 0.5-7.5 versus 1.1; range, 0.5-2.4) mL; P = .05), and more lacunar infarctions (64 versus 8, P = .04) than controls (mean age, 58 [SD, 11] years; 20 men). Carotid siphon calcification was associated with higher pulsatility indexes in patients with pseudoxanthoma elasticum (ß = 0.10; 95% CI, 0.01-0.18). CONCLUSIONS: Patients with pseudoxanthoma elasticum have increased intracranial artery flow pulsatility and measures of small-vessel disease. Carotid siphon calcification might underlie the high prevalence of cerebrovascular disease in pseudoxanthoma elasticum.

Quantification and visualization of flow in the Circle of Willis: time-resolved three-dimensional phase contrast MRI at 7 T compared with 3 T.

The assessment of both geometry and hemodynamics of the intracranial arteries has important diagnostic value in internal carotid occlusion, sickle cell disease, and aneurysm development. Provided that signal to noise ratio (SNR) and resolution are high, these factors can be measured with time-resolved three-dimensional phase contrast MRI. However, within a given scan time duration, an increase in resolution causes a decrease in SNR and vice versa, hampering flow quantification and visualization. To study the benefits of higher SNR at 7 T, three-dimensional phase contrast MRI in the Circle of Willis was performed at 3 T and 7 T in five volunteers. Results showed that the SNR at 7 T was roughly 2.6 times higher than at 3 T. Therefore, segmentation of small vessels such as the anterior and posterior communicating arteries succeeded more frequently at 7 T. Direction of flow and smoothness of streamlines in the anterior and posterior communicating arteries were more pronounced at 7 T. Mean velocity magnitude values in the vessels of the Circle of Willis were higher at 3 T due to noise compared to 7 T. Likewise, areas of the vessels were lower at 3 T. In conclusion, the gain in SNR at 7 T compared to 3 T allows for improved flow visualization and quantification in intracranial arteries.

In vivo blood T(1) measurements at 1.5 T, 3 T, and 7 T.

The longitudinal relaxation time of blood is a crucial parameter for quantification of cerebral blood flow by arterial spin labeling and is one of the main determinants of the signal-to-noise ratio of the resulting perfusion maps. Whereas at low and medium magnetic field strengths (B0), its in vivo value is well established; at ultra-high field, this is still uncertain. In this study, longitudinal relaxation time of blood in the sagittal sinus was measured at 1.5 T, 3 T, and 7 T. A nonselective inversion pulse preceding a Look-Locker echo planar imaging sequence was performed to obtain the inversion recovery curve of venous blood. The results showed that longitudinal relaxation time of blood at 7 T was ∼ 2.1 s which translates to an anticipated 33% gain in the signal-to-noise ratio in arterial spin labeling experiments due to T1 relaxation alone compared with 3 T. In addition, the linear relationship between longitudinal relaxation time of blood and B0 was confirmed.

Current status of clinical magnetic resonance imaging for plaque characterisation in patients with carotid artery stenosis.

OBJECTIVE: The article aims to provide an overview of the literature that assessed the agreement between magnetic resonance imaging (MRI) and histology for specific carotid plaque characteristics associated with vulnerability in terms of sensitivity and specificity. METHODS: A systematic search strategy was conducted in MEDLINE and EMBASE databases resulting in 1084 articles. Finally, we included 17 papers. Due to variation in presentation, especially in MRI and histology methods, a pooled analysis could not be performed. RESULTS: Two studies were performed on a 3.0-T MRI scanner; all other studies were performed on a 1.5-T scanner. Most performed sequences were two-dimensional (2D) and three-dimensional (3D) T1-weighted and all histology protocols varied slightly. Our results indicate that calcification, fibrous cap, intraplaque haemorrhage and lipid-rich necrotic cores can be identified with moderate-to-good sensitivity and specificity. CONCLUSIONS: Based on current literature, it appears premature for routine application of MRI as an imaging modality to assess carotid plaque characteristics associated with plaque vulnerability. Although MRI still holds promise, clinical application for plaque characterisation would require consensus regarding MRI settings and confirmation by histology. Predefined protocols for histology and MR imaging need to be established.

Incompleteness of the circle of Willis is related to EEG-based shunting during carotid endarterectomy.

OBJECTIVES: The occurrence of cerebral ischemia during carotid endarterectomy (CEA) can be prevented by (selective) placement of an intraluminal shunt during cross-clamping. We set out to develop a rule to predict the likelihood for shunting during CEA based on preoperative assessment of collateral cerebral circulation and patient characteristics. METHODS: Patients who underwent CEA between 2004 and 2010 were included. Patients without preoperative magnetic resonance (MRA) or computed tomography angiography (CTA) were excluded. The primary endpoint was intraluminal shunt placement based on electroencephalography changes. Age, sex, cardiovascular risk factors peripheral artery disease, symptomatic status, degree of ipsilateral and contralateral carotid, status of the vertebral arteries, and morphology of the CoW were studied as potential predictors for shunt use. A prediction model was derived from a multivariable regression model using discrimination, calibration, and bootstrapping approaches and transformed into a clinical prediction model. RESULTS: A total of 431 patients were included, of which 65 patients (15%) received an intraluminal shunt. In the MRA group (n = 285) factors related to shunt use in multivariate analysis were ipsilateral carotid stenosis 90-99% (odds ratio [OR] 0.15, 95% CI 0.04-0.53), contralateral carotid occlusion (OR 4.29, 95% CI 1.68-10.95) and any not-visible anterior (OR 4.96, 95% CI 1.95-12.58) or ipsilateral posterior segment of the CoW (OR 5.08, 95% CI 2.10-12.32). In the CT group none of the factors were independently related to shunt use; therefore, only predictors describing morphology of CoW derived from MRA findings were included in our model. The c-statistic of this model was 0.79 (95% CI 0.72-0.86). Among patients with an estimated chance of needing a shunt of under 10% (49% of the population), the likelihood of shunting was 5%. In those in whom this chance was estimated higher than 30% (13% of the population) the likelihood was 51%. CONCLUSIONS: Among patients scheduled for CEA, assessment of cerebral arteries and of the configuration of the CoW based on MRA-derived images can help to identify patients with low and high likelihood of the need of shunt use during surgery.

Changes in intra- and extracranial carotid plaque calcification: a 2-year follow-up study.

Extra- and intracranial carotid plaque calcification might have plaque-stabilizing effects, yet information on changes in plaque calcification remains scarce. We evaluated changes in carotid plaque calcification over 2 years follow-up in patients with symptomatic carotid artery disease. This study is based on the PARISK-study, a multicenter cohort study, with TIA/minor stroke patients with ipsilateral mild-to-moderate carotid artery stenosis (< 70%). We included 79 patients (25% female, mean age 66 years) who underwent CTA imaging with 2 year interval. We assessed the volume of extra- and intracranial carotid artery calcification (ECAC and ICAC) and calculated the difference between baseline and follow-up ECAC and ICAC volume. We performed multivariable regression analyses to investigate the association between change of ECAC or ICAC with cardiovascular determinants. ECAC. We found increase (46.2%) and decrease (34%) in ECAC volume during 2 year follow-up, both significantly correlation with baseline ECAC volume (OR = 0.72, 95% CI 0.58-0.90 respectively OR = 2.24, 95% CI 1.60-3.13).We found significant correlation for change in ECAC volume with diabetes (ß = 0.46, 95% CI 0.03-0.89) and baseline ECAC volume (ß = 0.81, 95% CI 0.73-0.88). ICAC. We found increase (45.0%) and decrease (25.0%) in ICAC volume. The ICAC decrease was significantly correlated with baseline ICAC volume (OR = 2.17, 95% CI 1.48-3.16), age (OR = 2.00, 95% CI 1.19-3.38) and use of antihypertensive drugs (OR = 3.79, 95% CI 1.20-11.96]).The overall change of ICAC volume was also significantly correlated with diabetes (ß = 0.92, 95% CI 1.59-7.02), use of oral hypoglycemic drugs (ß = 0.86, 95% CI 0.12-1.59) and baseline ICAC volume (ß = 0.71, 95% CI 0.55-0.87). We provide novel insights into the dynamics of carotid plaque calcification in symptomatic stroke patients.

Microinfarcts in the Deep Gray Matter on 7T MRI: Risk Factors, MRI Correlates, and Relation to Cognitive Functioning-The SMART-MR Study.

BACKGROUND AND PURPOSE: The clinical relevance of cortical microinfarcts has recently been established; however, studies on microinfarcts in the deep gray matter are lacking. We examined the risk factors and MR imaging correlates of microinfarcts in the deep gray matter on 7T MR imaging and their relation to cognitive functioning. MATERIALS AND METHODS: Within the Second Manifestations of ARTerial disease-Magnetic Resonance (SMART-MR) study, 213 patients (mean age, 68 [SD, 8] years) had a risk-factor assessment, 7T and 1.5T brain MR imaging, and a cognitive examination. Microinfarcts on 7T MR imaging were defined as lesions of <5 mm. Regression models were used to examine the age-adjusted associations among risk factors, MR imaging markers, and microinfarcts. Cognitive function was summarized as composite and domain-specific z scores. RESULTS: A total of 47 microinfarcts were found in 28 patients (13%), most commonly in the thalamus. Older age, history of stroke, hypertension, and intima-media thickness were associated with microinfarcts. On 1.5T MR imaging, cerebellar infarcts (relative risk = 2.75; 95% CI, 1.4-5.33) and lacunes in the white (relative risk = 3.28; 95% CI, 3.28-6.04) and deep gray matter (relative risk = 3.06; 95% CI, 1.75-5.35) were associated with microinfarcts, and on 7T MR imaging cortical microinfarcts (relative risk = 2.33; 95% CI, 1.32-4.13). Microinfarcts were also associated with poorer global cognitive functioning (mean difference in the global z score between patients with multiple microinfarcts versus none = -0.97; 95% CI, -1.66 to -0.28, P = .006) and across all cognitive domains. CONCLUSIONS: Microinfarcts in the deep gray matter on 7T MR imaging were associated with worse cognitive functioning and risk factors and MR imaging markers of small-vessel and large-vessel disease. Our findings suggest that microinfarcts in the deep gray matter may represent a novel imaging marker of vascular brain injury.