Perfusion MRI demonstrates crossed-cerebellar diaschisis in sickle cell disease

Crossed cerebellar diaschisis in Alzheimer's disease

BACKGROUND

Crossed cerebellar diaschisis (CCD) is characterized by hypometabolism and hypoperfusion on molecular imaging in the cerebellum due to a supratentorial lesion on the contralateral side. CCD is a well-established phenomenon in acute or subacute conditions such as infarction but it has been less well described in chronic conditions such as neurodegenerative dementias. Here, we investigate CCD in a large sample of 830 people meeting research criteria for Alzheimer's disease (AD) using [18F]fluorodeoxyglucose-positron emission tomography (FDG-PET).

MATERIALS AND METHODS

This study is based on FDG-PET data collected at baseline as part of two large-scale Phase III clinical trials of a novel tau aggregation inhibitor medication, methylthioninium in mild to moderate AD participants. Quantification of FDG-PET hypometabolism was carried out using standardized uptake value ratio (SUVR), with the pons as the comparison region. SUVR was compared in different regions of interest between the right and left hemispheres of the brain and cerebellum in people with mild AD (Mini-Mental State Examination score ≥ 20).

RESULTS

Comparison of SUVR in different brain regions demonstrated significant differences in the temporal, occipital and cerebellar cortices. Right and left asymmetry was noted with lower SUVR in the left temporal and occipital regions, whereas SUVR was lower in the right side of the cerebellum.

CONCLUSION

Here, we found robust evidence of CCD in a large sample of people with AD, a chronic neurodegenerative condition. The presence of this phenomenon in AD opens up a new avenue of research in AD pathogenesis and has the potential to change future diagnostic and therapeutic strategies.

Subacute Changes in N-Acetylaspartate (NAA) Following Ischemic Stroke: A Serial MR Spectroscopy Pilot Study

Preservation of neuronal tissue is crucial for recovery after stroke, but studies suggest that prolonged neuronal loss occurs following acute ischaemia. This study assessed the temporal pattern of neuronal loss in subacute ischemic stroke patients using ¹H magnetic resonance spectroscopy, in parallel with functional recovery at 2, 6 and 12 weeks after stroke. Specifically, we measured N-acetylaspartate (NAA), choline, myoinositol, creatine and lactate concentrations in the ipsilesional and contralesional thalamus of 15 first-ever acute ischaemic stroke patients and 15 control participants and correlated MRS concentrations with motor recovery, measured at 12 weeks using the Fugl-Meyer scale. NAA in the ipsilesional thalamus fell significantly between 2 and 12 weeks (10.0 to 7.97 mmol/L, p = 0.003), while choline, myoinositol and lactate concentrations increased (p = 0.025, p = 0.031, p = 0.001, respectively). Higher NAA concentrations in the ipsilesional thalamus at 2 and 12 weeks correlated with higher Fugl Meyer scores at 12 weeks (p = 0.004 and p = 0.006, respectively). While these results should be considered preliminary given the modest sample size, the progressive fall in NAA and late increases in choline, myoinositol and lactate may indicate progressive non-ischaemic neuronal loss, metabolically depressed neurons and/or diaschisis effects, which have a detrimental effect on motor recovery. Interventions that can potentially limit this ongoing subacute tissue damage may improve stroke recovery.

Detection of Crossed Cerebellar Diaschisis by Intravoxel Incoherent Motion MR Imaging in Subacute Ischemic Stroke

Intravoxel incoherent motion has received extensive attention in brain studies for its potential as a non-invasive magnetic resonance perfusion method. However, studies on intravoxel incoherent motion imaging and crossed cerebellar diaschisis detection are relatively scarce. The aim of our study was to evaluate the feasibility of using intravoxel incoherent motion imaging in crossed cerebellar diaschisis diagnosis in subacute ischemic stroke patients by comparing results from intravoxel incoherent motion imaging, single-photon emission computed tomography, and arterial spin-labeling perfusion methods. In total, 39 patients with subacute ischemic stroke who underwent intravoxel incoherent motion, arterial spin-labeling, and single-photon emission computed tomography scanning were enrolled. Intravoxel incoherent motion-derived perfusion-related parameters including fast diffusion coefficient, vascular volume fraction, arterial spin-labeling-derived cerebral blood flow as well as single-photon emission computed tomography-derived cerebral blood flow of bilateral cerebellum were measured. A crossed cerebellar diaschisis-positive result was considered present with an asymmetry index ≥10% of single-photon emission computed tomography. In the crossed cerebellar diaschisis-positive group, fast diffusion coefficient, arterial spin-labeling-derived cerebral blood flow, and computed tomography-derived cerebral blood flow of the contralateral cerebellum decreased compared with those of the ipsilesional cerebellum; whereas vascular volume fraction significantly increased. The National Institutes of Health Stroke Scale score and infarct volume in the crossed cerebellar diaschisis-positive group were significantly higher than those in the crossed cerebellar diaschisis-negative group. A positive correlation was detected between the fast diffusion coefficient-based asymmetry index and the single-photon emission computed tomography-based asymmetry index, fast diffusion coefficient-based asymmetry, and arterial spin-labeling based asymmetry index; whereas the vascular volume fraction-based asymmetry index value had a negative correlation with the single-photon emission computed tomography-based asymmetry index and arterial spin-labeling based asymmetry index. Furthermore, the area under the receiver operating characteristic curve value of the arterial spin-labeling-based asymmetry index was 0.923. The fast diffusion coefficient derived from the intravoxel incoherent motion could be valuable for the assessment of crossed cerebellar diaschisis in supratentorial stroke patients.

A qualitative comparison of arterial spin labelling and dynamic susceptibility contrast MRI in 52 children with a range of neurological conditions

OBJECTIVE

To assess the usefulness of arterial spin labelling (ASL) compared with dynamic susceptibility contrast (DSC) perfusion MRI for typical paediatric neuroimaging applications at 1.5 T.

METHODS

52 children (age: 4 months-17 years) with a variety of neurological disorders were scanned using three-dimensional ASL and echoplanar imaging DSC sequences. All images were reviewed by an experienced neuroradiologist; image quality was recorded as "good", "acceptable" or "poor" and diagnostic value was noted as being "greater", "similar" or "less" for ASL when compared with DSC.

RESULTS

ASL cerebral blood flow (CBF) images were judged to be acceptable in 89% of cases, poor in 11% of cases and good in 0% of cases, while DSC CBF images were acceptable in 88% of cases, poor in 12% of cases and good in 0% of cases. ASL images were judged to have better diagnostic value than DSC images in 28% of cases, about the same in 58% of cases and worse in 14% of cases.

CONCLUSION

The results of this study suggest that ASL offers a realistic alternative to DSC in the paediatric setting for the majority of cases encountered in this study. However, there are some situations where DSC outperforms ASL; so, care is required to choose the most appropriate technique for the pathology under investigation. A larger study is required to corroborate these preliminary findings. Advances in knowledge: ASL is a relatively new perfusion imaging technique whose use has not been explored extensively in the paediatric setting. This work is a preliminary study to evaluate its usefulness in paediatric neuroimaging.

Crossed cerebellar diaschisis after stroke identified noninvasively with cerebral blood flow-weighted arterial spin labeling MRI

BACKGROUND AND PURPOSE

Crossed cerebellar diaschisis (CCD) is most commonly investigated using hemodynamic PET and SPECT imaging. However, noninvasive MRI offers advantages of improved spatial resolution, allowing hemodynamic changes to be compared directly with structural findings and without concerns related to ionizing radiation exposure. The aim of this study was to evaluate relationships between CCD identified from cerebral blood flow (CBF)-weighted arterial spin labeling (ASL) MRI with cerebrovascular reactivity (CVR)-weighted blood oxygenation level dependent (BOLD) MRI, Wallerian degeneration, clinical motor impairment, and corticospinal tract involvement.

METHODS

Subjects (n=74) enrolled in an ongoing observational stroke trial underwent CBF-weighted ASL and hypercapnic CVR-weighted BOLD MRI. Hemispheric asymmetry indices for basal cerebellar CBF, cerebellar CVR, and cerebral peduncular area were compared between subjects with unilateral supratentorial infarcts (n=18) and control subjects without infarcts (n=16). CCD required (1) supratentorial infarct and (2) asymmetric cerebellar CBF (>95% confidence interval relative to controls).

RESULTS

In CCD subjects (n=9), CVR (p=0.04) and cerebral peduncular area (p<0.01) were significantly asymmetric compared to controls. Compared to infarct subjects not meeting CCD criteria (n=9), CCD subjects had no difference in corticospinal tract location for infarct (p=1.0) or motor impairment (p=0.08).

CONCLUSIONS

CCD correlated with cerebellar CVR asymmetry and Wallerian degeneration. These findings suggest that noninvasive MRI may be a useful alternative to PET or SPECT to study structural correlates and clinical consequences of CCD following supratentorial stroke.

Arterial spin-labeling MR imaging of cerebral hemorrhages

INTRODUCTION

The purpose of this study is to identify the characteristics of brain perfusion measured by arterial spin-labeling magnetic resonance imaging (ASL-MRI) in cerebral hemorrhages.

METHODS

Brain blood flow values (CBF-ASL values) for cerebral and cerebellar hemispheres and segmented cerebral regions were measured by ASL-MRI in 19 putaminal hemorrhage patients and 20 thalamic hemorrhage patients in acute or subacute stages. We assessed the lateralities of CBF-ASL values and the relationships between CBF-ASL values and other imaging findings and clinical manifestations.

RESULTS

Both the 19 putaminal hemorrhage patients and the 20 thalamic hemorrhage patients had significantly low CBF-ASL values of the contralateral cerebellum in subacute stage, suggesting that ASL-MRI might delineate crossed cerebellar diaschisis (CCD). Ipsilateral low CBF-ASL values were observed in frontal lobes and thalami with a putaminal hemorrhage and lentiform nuclei, temporal lobes, and parietal lobes with a thalamic hemorrhage, suggesting that ASL-MRI showed the ipsilateral cerebral diaschisis (ICD). In the putaminal hemorrhage patients, the hematoma volume negatively affected both the bilateral cerebellar and cerebral hemispheric CBF-ASL values. In the thalamic hemorrhage patients, a concomitant intraventricular hemorrhage caused low cerebral hemispheric CBF-ASL values.

CONCLUSION

The use of ASL-MRI is sensitive to the perfusion abnormalities and could thus be helpful to estimate functional abnormalities in cerebral hemorrhage patients.

Crossed cerebellar diaschisis in acute isolated thalamic infarction detected by dynamic susceptibility contrast perfusion MRI

PURPOSE

Crossed cerebellar diaschisis (CCD) is a state of neural depression caused by loss of connections to injured neural structures remote from the cerebellum usually evaluated by positron emission tomography. Recently it has been shown that dynamic susceptibility contrast perfusion weighted MRI (PWI) may also be feasible to detect the phenomenon. In this study we aimed to assess the frequency of CCD on PWI in patients with acute thalamic infarction.

METHODS

From a MRI report database we identified patients with acute isolated thalamic infarction. Contralateral cerebellar hypoperfusion was identified by inspection of time to peak (TTP) maps and evaluated quantitatively on TTP, mean transit time (MTT), cerebral blood flow and volume (CBF, CBV) maps. A competing cerebellar pathology or an underlying vascular pathology were excluded.

RESULTS

A total of 39 patients was included. Common symptoms were hemiparesis (53.8%), hemihypaesthesia (38.5%), dysarthria (30.8%), aphasia (17.9%), and ataxia (15.4%). In 9 patients (23.1%) PWI showed hypoperfusion in the contralateral cerebellar hemisphere. All of these had lesions in the territory of the tuberothalamic, paramedian, or inferolateral arteries. Dysarthria was observed more frequently in patients with CCD (6/9 vs. 6/30; OR 8.00; 95%CI 1.54-41.64, p = 0.01). In patients with CCD, the median ischemic lesion volume on DWI (0.91 cm³), IQR 0.49-1.54 cm³) was larger compared to patients with unremarkable PWI (0.51 cm³, IQR 0.32-0.74, p = 0.05). The most pronounced changes were found in CBF (0.94±0.11) and MTT (1.06±0.13) signal ratios, followed by TTP (1.05±0.02).

CONCLUSIONS

Multimodal MRI demonstrates CCD in about 20% of acute isolated thalamic infarction patients. Lesion size seems to be a relevant factor in its pathophysiology.

Correlation between crossed cerebellar diaschisis and clinical neurological scales

BACKGROUND

A common consequence of unilateral stroke is crossed cerebellar diaschisis (CCD), a decrease in regional blood flow (CBF) and metabolism (CMRglu) in the cerebellar hemisphere contralateral to the affected cerebral hemisphere. Former studies indicated a post-stroke time-dependent relationship between the degree of CCD and the clinical status of acute and sub-acute stroke patients, but no study has been performed in post-stroke patients.

OBJECTIVES

The objective of this investigation was to evaluate the quantitative correlation between the degree of CCD and the values of clinical stroke scales in post-stroke patients.

MATERIALS AND METHODS

We measured with positron emission tomography (PET) regional CBF and CMRglu values in the affected cortical regions and the contralateral cerebellum in ten ischaemic post-stroke patients. Based on these quantitative parameters, the degree of diaschisis (DoD) was calculated, and the DoD values were correlated with three clinical stroke scales [Barthel Index, Orgogozo Scale and Scandinavian Neurological Scale (SNS)].

RESULTS

There were significant linear correlations between all clinical stroke scales and the CCD values (Barthel Index and Orgogozo Scale: P < 0.001, for both CBF and CMRglu; SNS: P = 0.007 and P = 0.044; CBF and CMRglu, respectively).

CONCLUSIONS

The findings indicate that DoD can be used as a quantitative indicator of the functional impairments following stroke, i.e. it can serve as a potential surrogate of the severity of the damage.

Novel MRI approaches for assessing cerebral hemodynamics in ischemic cerebrovascular disease

Changes in cerebral hemodynamics underlie a broad spectrum of ischemic cerebrovascular disorders. An ability to accurately and quantitatively measure hemodynamic (cerebral blood flow and cerebral blood volume) and related metabolic (cerebral metabolic rate of oxygen) parameters is important for understanding healthy brain function and comparative dysfunction in ischemia. Although positron emission tomography, single-photon emission tomography, and gadolinium-MRI approaches are common, more recently MRI approaches that do not require exogenous contrast have been introduced with variable sensitivity for hemodynamic parameters. The ability to obtain hemodynamic measurements with these new approaches is particularly appealing in clinical and research scenarios in which follow-up and longitudinal studies are necessary. The purpose of this review is to outline current state-of-the-art MRI methods for measuring cerebral blood flow, cerebral blood volume, and cerebral metabolic rate of oxygen and provide practical tips to avoid imaging pitfalls. MRI studies of cerebrovascular disease performed without exogenous contrast are synopsized in the context of clinical relevance and methodological strengths and limitations.

Arterial spin labeling in neuroimaging

Arterial spin labeling (ASL) is a magnetic resonance imaging technique for measuring tissue perfusion using a freely diffusible intrinsic tracer. As compared with other perfusion techniques, ASL offers several advantages and is now available for routine clinical practice in many institutions. Its noninvasive nature and ability to quantitatively measure tissue perfusion make ASL ideal for research and clinical studies. Recent technical advances have increased its sensitivity and also extended its potential applications. This review focuses on some basic knowledge of ASL perfusion, emerging techniques and clinical applications in neuroimaging.