Magnetization transfer measurements of brain structures in patients with multiple system atrophy

White matter and nigral alterations in multiple system atrophy-parkinsonian type

Multiple system atrophy (MSA) is classified into two main types: parkinsonian and cerebellar ataxia with oligodendrogliopathy. We examined microstructural alterations in the white matter and the substantia nigra pars compacta (SNc) of patients with MSA of parkinsonian type (MSA-P) using multishell diffusion magnetic resonance imaging (dMRI) and myelin sensitive imaging techniques. Age- and sex-matched patients with MSA-P (n = 21, n = 10 first and second cohorts, respectively), Parkinson’s disease patients (n = 19, 17), and healthy controls (n = 20, 24) were enrolled. Magnetization transfer saturation imaging (MT-sat) and dMRI were obtained using 3-T MRI. Measurements obtained from diffusion tensor imaging (DTI), free-water elimination DTI, neurite orientation dispersion and density imaging (NODDI), and MT-sat were compared between groups. Tract-based spatial statistics analysis revealed differences in diffuse white matter alterations in the free-water fractional volume, myelin volume fraction, and intracellular volume fraction between the patients with MSA-P and healthy controls, whereas free-water and MT-sat differences were limited to the middle cerebellar peduncle in comparison with those with Parkinson’s disease. Region-of-interest analysis of white matter and SNc revealed significant differences in the middle and inferior cerebellar peduncle, pontine crossing tract, corticospinal tract, and SNc between the MSA-P and healthy controls and/or Parkinson’s disease patients. Our results shed light on alterations to brain microstructure in MSA.

Imaging synucleinopathies

In this review the structural and functional imaging changes associated with the synucleinopathies PD, MSA, and dementias associated with Lewy bodies are reviewed. The role of imaging for supporting differential diagnosis, detecting subclinical disease, and following disease progression is discussed and its potential use for monitoring disease progression is debated. © 2016 International Parkinson and Movement Disorder Society.

Magnetization transfer MRI in dementia disorders, Huntington's disease and parkinsonism

Magnetic resonance imaging is the most used technique of neuroimaging. Using recent advances in magnetic resonance application it is possible to investigate several changes in neurodegenerative disease. Among different techniques, magnetization-transfer imaging (MTI), a magnetic resonance acquisition protocol assessing the magnetization exchange between protons bound to water and those bound to macromolecules, is able to identify microstructural brain tissue changes peculiar of neurodegenerative diseases. This review provides a report on the MTI technique and its use in the dementia disorders, Huntington's disease and parkinsonisms, comprehensive of the predictive values of MTI in the identification of early-phase disease.

The value of GRE, ADC and routine MRI in distinguishing Parkinsonian disorders

OBJECTIVES

To study different radiological signs and sequences including apparent diffusion coefficient (ADC) and gradient echo (GRE) to differentiate degenerative parkinsonian syndromes.

BACKGROUND

Multiple system atrophy (MSA), Parkinson's disease (PD), progressive supranuclear palsy (PSP) and corticobasal degeneration (CbD) differ in the pattern of neurodegeneration and cellular damage. Measuring the ADC, GRE sequences for paramagnetic substances and simple anatomical assessments have been reported individually to assist in separating some of these disorders, but have not been compared.

METHODS

brain MRIs from May 2002 to February 2008 were retrospectively evaluated by raters blinded to the clinical diagnosis for predefined MRI signs on T1, T2 and GRE sequences. ADC values were quantitatively measured. Medical records were objectively analyzed using standard clinical criteria for different parkinsonian syndromes.

RESULTS

195 cases comprising of 61 PD, 15 MSA-P, 7 MSA-C, 21 PSP, 6 Corticobasal syndrome, 21 not fitting criteria and 64 controls were evaluated. 73% of patients with MSA-P had hypointensity of the putamen (compared to the pallidum) on GRE. The specificity of this sign to diagnose MSA-P was 90% versus PD and 76% versus PSP. When GRE hypointensity was combined with atrophy of the putamen the specificity improved to 98% (versus PD) and 95% (versus PSP) without altering the sensitivity. The ADC values were significantly higher in the middle cerebellar peduncle in cases with MSA-C versus controls, PD and PSP (p<0.001).

CONCLUSIONS

The combination of hypointensity and atrophy of the putamen on GRE is useful in differentiating MSA-P from other parkinsonian syndromes.

Differentiation of typical and atypical Parkinson syndromes by quantitative MR imaging

BACKGROUND AND PURPOSE

The differential diagnosis of Parkinson syndromes remains a major challenge. Quantitative MR imaging can aid in this classification, but it is unclear which of the proposed techniques is best suited for this task. We, therefore, conducted a head-to-head study with different quantitative MR imaging measurements in patients with IPS, MSA-type Parkinson, PSP, and healthy elderly controls.

MATERIALS AND METHODS

Thirty-one patients and 13 controls underwent a comprehensive quantitative MR imaging protocol including R2*-, R2- and R1-mapping, magnetization transfer, and DTI with manual region-of-interest measurements in basal ganglia regions. Group differences were assessed with a post hoc ANOVA with a Bonferroni error correction and an ROC.

RESULTS

The best separation of MSA from IPS in patients and controls could be achieved with R2*-mapping in the PU, with an ROC AUC of ≤0.96, resulting in a sensitivity of 77.8% (with a specificity 100%). MD was increased in patients with PSP compared with controls and to a lesser extent compared with those with IPS and MSA in the SN.

CONCLUSIONS

Among the applied quantitative MR imaging methods, R2*-mapping seems to have the best predictive power to separate patients with MSA from those with IPS, and DTI for identifying PSP.

MRI for the differential diagnosis of neurodegenerative parkinsonism in clinical practice

Parkinson's disease (PD) is the most common neurodegenerative cause of parkinsonism, followed by progressive supranuclear palsy (PSP) and multiple system atrophy (MSA). Despite the publication of consensus operational criteria for the diagnosis of PD and the various atypical parkinsonian disorders (APD) such as PSP, MSA and corticobasal degeneration, an accurate diagnosis of neurodegenerative parkinsonian syndromes remains a challenge for each neurologist. Particularly in the early disease stages the clinical separation of APDs from PD carries a high rate of misdiagnosis. However, an early differentiation between APD and PD, each characterized by completely different natural histories, is crucial for determining the prognosis and choosing a treatment strategy. MRI plays an important role in the exclusion of symptomatic parkinsonism due to other pathologies. Over the past two decades, conventional MRI and advanced MRI techniques, including proton magnetic resonance spectroscopy (1H-MRS), diffusion-weighted imaging (DWI), magnetization transfer imaging (MTI), and magnetic resonance volumetry (MRV) have shown abnormalities in the substantia nigra and basal ganglia, especially in APD. Furthermore, in accordance with neuropathological studies suggesting that the olfactory system is an early target of the disease, recent studies using advanced MRI techniques have shown abnormalities in the olfactory system in the early disease stages of patients with PD. Given that olfactory deficits may be a premotor marker of the disease, such methods may eventually evolve into an early screening tool for PD.

Magnetization transfer magnetic resonance imaging of the brain, spinal cord, and optic nerve

Magnetic resonance imaging is highly sensitive in revealing CNS abnormalities associated with several neurological conditions, but lacks specificity for their pathological substrates. In addition, MRI does not allow evaluation of the presence and extent of damage in regions that appear normal on conventional MRI sequences and that postmortem studies have shown to be affected by pathology. Quantitative MR-based techniques with increased pathological specificity to the heterogeneous substrates of CNS pathology have the potential to overcome such limitations. Among these techniques, one of the most extensively used for the assessment of CNS disorders is magnetization transfer MRI (MT-MRI). The application of this technique for the assessment of damage in macroscopic lesions, in normal-appearing white and gray matter, and in the spinal cord and optic nerve of patients with several neurological conditions is providing important in vivo information-dramatically improving our understanding of the factors associated with the appearance of clinical symptoms and the accumulation of irreversible disability. MT-MRI also has the potential to contribute to the diagnostic evaluation of several neurological conditions and to improve our ability to monitor treatment efficacy in experimental trials.

Evaluating posterolateral linearization of the putaminal margin with magnetic resonance imaging to diagnose the Parkinson variant of multiple system atrophy

The objective was to develop a simple method for evaluating putaminal atrophy in patients with the Parkinson variant of multiple system atrophy (MSA-P). We used magnetic resonance imaging to study 9 patients with MSA-P, 24 patients with cerebellar variants of multiple system atrophy (MSA-C), 38 patients with Parkinson's disease (PD), and 27 healthy control subjects. Posterolateral linearization of the putaminal margin was semiquantitatively scored and the putaminal area per intracranial area was calculated as the adjusted putaminal area. There was a negative correlation between the linearization scores and adjusted putaminal areas (r = -0.43, P < 0.001), such that the mean adjusted putaminal area in the group without putaminal linearization (0.0148 +/- 0.0022) was greater than that of the group with linearization (0.0124 +/- 0.0029, P < 0.005). Moreover, the occurrence of putaminal linearization was significantly higher in MSA-P patients (88.8%) than in MSA-C (8.3%), PD (7.9%) and healthy subjects (7.4%; P < 0.005). Putaminal linearization was a highly sensitive (0.89) and specific (0.91) measure for differentiating MSA-P. Our results suggest that evaluating posterolateral putaminal linearization is useful for assessing putaminal atrophy and for differentiating MSA-P from MSA-C, PD, and healthy subjects.

Pyramidal tract degeneration in multiple system atrophy: the relevance of magnetization transfer imaging

The clinical features of multiple system atrophy (MSA) include four domains: autonomic failure/urinary dysfunction, Parkinsonism, cerebellar ataxia, and corticospinal tract dysfunction. Although the diagnosis of definite MSA requires pathological confirmation, magnetic resonance imaging (MRI) studies have been shown to contribute to the diagnosis of MSA. Although pyramidal tract dysfunction is frequent in MSA patients, signs of pyramidal tract involvement are controversially demonstrated by MRI. We evaluated the pyramidal involvement in 10 patients (7 women) with clinically probable MSA, detecting the presence of spasticity, hyperreflexia, and Babinski sign, as well as demonstrating degeneration of the pyramidal tract and primary motor cortex by MRI in all of them. Our article also discusses key radiological features of this syndrome. In MSA, pyramidal tract involvement seems to be more frequent than previously thought, and the clinicoradiological correlation between pyramidal tract dysfunction and degeneration may contribute to the understanding of the clinical hallmarks of MSA. MRI may also add information regarding the differential diagnosis of this syndrome.

An update on conventional and advanced magnetic resonance imaging techniques in the differential diagnosis of neurodegenerative parkinsonism

PURPOSE OF REVIEW

The clinical differentiation between Parkinson's disease and atypical parkinsonian disorders (APD) remains a challenge for every neurologist. Conventional magnetic resonance imaging (MRI) and different advanced MRI techniques offer the potential for objective criteria in the differential diagnosis of neurodegenerative parkinsonism. The aim of this article is to review the recent literature on the role of conventional and advanced MRI techniques in the differential diagnosis of neurodegenerative parkinsonian disorders.

RECENT FINDINGS

An important role of MRI is the exclusion of symptomatic parkinsonism due to other pathologies. Over the past two decades, conventional MRI and different advanced MRI techniques, including proton magnetic resonance spectroscopy (1H-MRS), diffusion-weighted imaging (DWI), magnetization transfer imaging (MTI) and magnetic resonance volumetry (MRV) have been found to show abnormalities in the substantia nigra and basal ganglia, especially in APD. Recent studies using MRV, MTI, DWI and 1H-MRS to discriminate Parkinson's disease from APD are discussed extensively.

SUMMARY

Research findings suggest that novel MRI techniques such as MTI, DWI and MRV have superior sensitivity compared to conventional MRI in detecting abnormal features in neurodegenerative parkinsonian disorders. Whether these techniques will emerge as standard investigations in the work-up of patients presenting with parkinsonism requires further prospective magnetic resonance studies during early disease stages.

How to diagnose MSA early: the role of magnetic resonance imaging

The clinical differentiation between Parkinson's disease (PD) and multiple system atrophy (MSA) remains a challenge for each neurologist. The use of different magnetic resonance imaging (MRI) techniques including conventional MRI, proton magnetic resonance spectroscopy (MRS), diffusion-weighted imaging (DWI), magnetization transfer imaging (MTI) and MR volumetry (MRV) offer the potential for objective criteria in the differential diagnosis of neurodegenerative parkinsonism. The aim of this article is to review the role of different MRI techniques in the differential diagnosis of PD and MSA.

How to diagnose multiple system atrophy

The diagnosis of multiple system atrophy (MSA) in life remains entirely clinical. Consensus diagnostic criteria have been developed, but their use does not particularly render a diagnosis of MSA more accurate than are clinicians' diagnoses. Some patients may not fulfill the stipulated core diagnostic criteria, yet display many so-called red flags pointing toward MSA. The additional usefulness of these red flags and of a variety of investigations currently is being investigated, with a view to some of them being incorporated in future sets of diagnostic criteria.

Differentiation of idiopathic Parkinson's disease, multiple system atrophy, progressive supranuclear palsy, and healthy controls using magnetization transfer imaging

The differentiation of multiple system atrophy (MSA) and progressive supranuclear palsy (PSP) from idiopathic Parkinson's disease (IPD) is difficult. Magnetization transfer imaging (MTI), a measure that correlates with myelination and axonal density, was employed in this study in the attempt to distinguish between these disorders. Measurements were carried out in 15 patients with IPD, 12 patients with MSA, 10 patients with PSP, and in 20 aged-matched healthy control subjects. The main finding was a change in the magnetization transfer ratio in the globus pallidus, putamen, caudate nucleus, substantia nigra, and white matter in IPD, MSA, and PSP patients, matching the pathological features of the underlying disorder. Furthermore, stepwise linear discriminant analysis provided a good classification of the individual patients into the different disease groups. All IPD patients and control subjects were correctly separated from the MSA and PSP cohort, and all PSP patients and 11 of 12 MSA patients were correctly separated from the IPD and control cohort. There was also a fairly good discrimination of IPD patients from control subjects and of MSA from PSP patients. In conclusion, MTI revealed degenerative changes in patients with different parkinsonian syndromes matching the underlying pathological features of the different diseases, underlining the high potential of this method in distinguishing MSA and PSP from IPD.

Magnetization transfer, HASTE, and FLAIR imaging

Continuous technologic developments and research have increased the clinical applications of MT, HASTE, and FLAIR imaging in neuroradiology. HASTE has become the MR imaging sequence of choice for fetal neuroimaging. Other promising uses, such as for diffusion-weighted imaging, have not been fully exploited. FLAIR has been firmly established as one of the cornerstones of brain imaging; however, post-contrast FLAIR images have not offered a clear advantage over standard T1-weighted images as suggested by early studies. FLAIR imaging with echoplanar acquisition is not considered advantageous, because the decreased imaging times are obtained at the expense of lower sensitivity. For a number of applications, diffusion-weighted imaging has surpassed FLAIR. Nevertheless, FLAIR images may be more sensitive for the detection of acute brain infarction. Recently described methods for the elimination of CSF flow artifacts may lead to improved quality and reliability of FLAIR images for subarachnoid space disease. MT preparation is now routinely incorporated in time-of-flight MR angiography and gradient-echo T2*-weighted spine imaging sequences and provides increased sensitivity for postcontrast MR imaging. These applications may not be advantageous in all clinical settings. MTR analysis offers valuable information for an increasing number of pathologic processes but has not yet gained wide clinical acceptance owing to sophisticated postprocessing and significant intercenter variations. Different modifications of these techniques are being evaluated, and further developments are expected.