Putaminal magnetic resonance imaging features at various magnetic field strengths in multiple system atrophy

The “Black Straight-Line Sign” in the Putamen in Diffusion-Weighted Imaging: A Potential Diagnostic MRI Marker for Multiple System Atrophy

Background and Purpose

The diagnosis of multiple system atrophy (MSA) remains challenging in clinical practice. This study investigated the value of hypointense signals in the putamen (“black straight-line sign”) in diffusion-weighted imaging (DWI) of brain MRI for distinguishing (MSA) from Parkinson's disease (PD).

Methods

We retrospectively enrolled 30 MSA patients, 30 PD patients, and 30 healthy controls who had undergone brain MRI between 2016 and 2020. Two readers independently assessed the signal intensity of the bilateral putamen on DWI. The putaminal hypointensity was scored using 4-point visual scales. Putaminal hypointensity and the presence of a “black straight-line sign” were statistically compared between MSA and PD or healthy controls.

Results

The mean scores of putaminal hypointensity in DWI in the MSA group were significantly higher than in both the PD (U = 315.5, P = 0.034) and healthy control groups (U = 304.0, P = 0.022). Uni- or bilateral putaminal hypointensity in DWI with a score ≥2 was identified in 53.3% (16/30), 16.7% (5/30), and 13.3% (4/30) of MSA, PD, and healthy controls, respectively, with significant differences between MSA and PD (X² = 8.864, P = 0.003) or healthy controls (X² = 10.800, P = 0.001). Notably, the “black straight-line sign” of the putamen was observed in 16/30 (sensitivity 53.3%) patients with MSA, while it was absent in PD and healthy controls (specificity 100%). There were no significant differences for the presence of “black straight-line sign” in the MSA-P and MSA-C groups (X² = 0.433, P = 0.510).

Conclusion

The “black straight-line sign” of the putamen in DWI of head MRIs has the potential to serve as a diagnostic marker for distinguishing MSA from PD.

Iron distribution in the lentiform nucleus: A post-mortem MRI and histology study

Iron plays an important role in many neurobiological processes, especially in the basal ganglia, the brain structures with the highest concentration. Composed of the pallidum and putamen, the lentiform nucleus plays a key role in the basal ganglia circuitry. With MRI advances, iron-based sequences such as R2* and quantitative susceptibility mapping (QSM) are now available for detecting and quantifying iron in different brain structures. Since their validation using classic iron detection techniques (histology or physical techniques), these sequences have attracted growing clinical attention, especially in the field of extrapyramidal syndromes that particularly affect the basal nuclei. Accurate mapping of iron in these nuclei and their connections is needed to gain a better understanding of this specific anatomy, before considering its involvement in the physiopathological processes. We performed R2* and QSM along with Perls histology, to gain new insights into the distribution of iron in the lentiform nucleus and its surrounding structures, based on four specimens obtained from voluntary donors. We found that iron is preferentially distributed in the anterior part of the globus pallidus externus and the posterior part of the putamen. The lateral wall of the putamen is iron-poor, compared with the lateral medullary lamina and intraputaminal fibers. The relevance of perivascular iron concentration, along with pallido- and putaminofugal iron-rich fibers, is discussed.

Can Autonomic Testing and Imaging Contribute to the Early Diagnosis of Multiple System Atrophy? A Systematic Review and Recommendations by the Movement Disorder Society Multiple System Atrophy Study Group

Background

In the current consensus diagnostic criteria, the diagnosis of probable multiple system atrophy (MSA) is based solely on clinical findings, whereas neuroimaging findings are listed as aid for the diagnosis of possible MSA. There are overlapping phenotypes between MSA-parkinsonian type and Parkinson's disease, progressive supranuclear palsy, and dementia with Lewy bodies, and between MSA-cerebellar type and sporadic adult-onset ataxia resulting in a significant diagnostic delay and misdiagnosis of MSA during life.

Objectives

In light of an ongoing effort to revise the current consensus criteria for MSA, the Movement Disorders Society Multiple System Atrophy Study Group performed a systematic review of original articles published before August 2019.

Methods

We included articles that studied at least 10 patients with MSA as well as participants with another disorder or control group for comparison purposes. MSA was defined by neuropathological confirmation, or as clinically probable, or clinically probable plus possible according to consensus diagnostic criteria.

Results

We discuss the pitfalls and benefits of each diagnostic test and provide specific recommendations on how to evaluate patients in whom MSA is suspected.

Conclusions

This systematic review of relevant studies indicates that imaging and autonomic function tests significantly contribute to increasing the accuracy of a diagnosis of MSA.

The Role of Magnetic Resonance Imaging for the Diagnosis of Atypical Parkinsonism

The diagnosis of Parkinson's disease and atypical Parkinsonism remains clinically difficult, especially at the early stage of the disease, since there is a significant overlap of symptoms. Multimodal MRI has significantly improved diagnostic accuracy and understanding of the pathophysiology of Parkinsonian disorders. Structural and quantitative MRI sequences provide biomarkers sensitive to different tissue properties that detect abnormalities specific to each disease and contribute to the diagnosis. Machine learning techniques using these MRI biomarkers can effectively differentiate atypical Parkinsonian syndromes. Such approaches could be implemented in a clinical environment and improve the management of Parkinsonian patients. This review presents different structural and quantitative MRI techniques, their contribution to the differential diagnosis of atypical Parkinsonian disorders and their interest for individual-level diagnosis.

Dopamine-loaded poly (butyl cyanoacrylate) nanoparticles reverse behavioral deficits in Parkinson’s animal models

Aim: Parkinson's disease (PD) is a neurological disorder resulting from decreased dopamine (DA) secretion in the brain, which reflects impaired motor function. Thus, a drug-delivery system for releasing DA into the brain would be of crucial importance. Materials & methods: We herein examined the in vivo drug efficiency of novel poly-butyl-cyanoacrylate nanoparticles loaded with DA (DA-PBCA NPs). Results & conclusion: The NPs were able to pass through the blood–brain barrier and improve brain structure and function in the PD animal models. Moreover, we found a reduced α-synucleinopathy in the animal model brains after the NPs administration. Thus, the NPs seem to be a reliable DA delivery system for treating PD patients.

ACR Appropriateness Criteria® Movement Disorders and Neurodegenerative Diseases

Movement disorders and neurodegenerative diseases are a variety of conditions that involve progressive neuronal degeneration, injury, or death. Establishing the correct diagnosis of a movement disorder or neurodegenerative process can be difficult due to the variable features of these conditions, unusual clinical presentations, and overlapping symptoms and characteristics. MRI has an important role in the initial assessment of these patients, although a combination of imaging and laboratory and genetic tests is often needed for complete evaluation and management. This document summarizes the imaging appropriateness data for rapidly progressive dementia, chorea, Parkinsonian syndromes, suspected neurodegeneration with brain iron accumulation, and suspected motor neuron disease. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Differential value of brain magnetic resonance imaging in multiple system atrophy cerebellar phenotype and spinocerebellar ataxias

Clinically differentiating multiple system atrophy cerebellar (MSA-C) phenotype and spinocerebellar ataxias (SCAs) is challenging especially in the early stage. We assessed diagnostic value of brain magnetic resonance imaging (MRI) in differentiating MSA-C and SCAs based at different disease stages (<3, 3–7, and >7 years of disease duration). Overall, 186 patients with probable MSA-C and 117 with genetically confirmed SCAs were included. Hot cross bun (HCB) signs and middle cerebellar peduncle (MCP) hyperintensities were exclusively prevalent in MSA-C compared to SCAs at <3 years (HCB, 44.6% versus 0.9%; MCP hyperintensities, 38.3% versus 0.9%, respectively). Sensitivity, specificity, and positive predictive value (PPV) for HCB signs to differentiate MSA-C from SCAs were 45%, 99%, and 99% and those for MCP hyperintensities were 68%, 99%, and 99%, respectively; considering both HCB signs and MCP hyperintensities, specificity and PPV were 100%. However, the differential value of MRI signs decreased over time. MCP widths were smaller and showed more significant decrease in MSA-C than in SCAs. In conclusion, pontine and MCP changes were exclusively prominent in early stage MSA-C rather than in SCAs. Therefore, we should consider disease duration when interpreting pontine and MCP changes in brain MRIs, which will help better differentiate MSA-C and SCAs.

Structural Imaging in Atypical Parkinsonism

Qualitative and quantitative structural magnetic resonance imaging offer objective measures of the underlying neurodegeneration in atypical parkinsonism. Regional changes in tissue volume, signal changes and increased deposition of iron as assessed with different structural MRI techniques are surrogate markers of underlying neurodegeneration and may reflect cell loss, microglial proliferation and astroglial activation. Structural MRI has been explored as a tool to enhance diagnostic accuracy in differentiating atypical parkinsonian disorders (APDs). Moreover, the longitudinal assessment of serial structural MRI-derived parameters offers the opportunity for robust inferences regarding the progression of APDs. This review summarizes recent research findings as (1) a diagnostic tool for APDs as well as (2) as a tool to assess longitudinal changes of serial MRI-derived parameters in the different APDs.

Clinical and Imaging Features of Multiple System Atrophy: Challenges for an Early and Clinically Definitive Diagnosis

Multiple system atrophy (MSA) is an adult-onset, progressive neurodegenerative disorder. Patients with MSA show various phenotypes during the course of their illness, including parkinsonism, cerebellar ataxia, autonomic failure, and pyramidal signs. Patients with MSA sometimes present with isolated autonomic failure or motor symptoms/ signs. The median duration from onset to the concomitant appearance of motor and autonomic symptoms is approximately 2 years but can range up to 14 years. As the presence of both motor and autonomic symptoms is essential for the current diagnostic criteria, early diagnosis is difficult when patients present with isolated autonomic failure or motor symptoms/signs. In contrast, patients with MSA may show severe autonomic failure and die before the presentation of motor symptoms/signs, which are currently required for the diagnosis of MSA. Recent studies have also revealed that patients with MSA may show nonsupporting features of MSA such as dementia, hallucinations, and vertical gaze palsy. To establish early diagnostic criteria and clinically definitive categorization for the successful development of disease-modifying therapy or symptomatic interventions for MSA, research should focus on the isolated phase and atypical symptoms to develop specific clinical, imaging, and fluid biomarkers that satisfy the requirements for objectivity, for semi- or quantitative measurements, and for uncomplicated, worldwide availability. Several novel techniques, such as automated compartmentalization of the brain into multiple parcels for the quantification of gray and white matter volumes on an individual basis and the visualization of α-synuclein and other candidate serum and cerebrospinal fluid biomarkers, may be promising for the early and clinically definitive diagnosis of MSA.

The Relevance of Iron in the Pathogenesis of Multiple System Atrophy: A Viewpoint

Iron is essential for cellular development and maintenance of multiple physiological processes in the central nervous system. The disturbance of its homeostasis leads to abnormal iron deposition in the brain and causes neurotoxicity via generation of free radicals and oxidative stress. Iron toxicity has been established in the pathogenesis of Parkinson's disease; however, its contribution to multiple system atrophy (MSA) remains elusive. MSA is characterized by cytoplasmic inclusions of misfolded α-synuclein (α-SYN) in oligodendrocytes referred to as glial cytoplasmic inclusions (GCIs). Remarkably, the oligodendrocytes possess high amounts of iron, which together with GCI pathology make a contribution toward MSA pathogenesis likely. Consistent with this observation, the GCI density is associated with neurodegeneration in central autonomic networks as well as olivopontocerebellar and striatonigral pathways. Iron converts native α-SYN into a β-sheet conformation and promotes its aggregation either directly or via increasing levels of oxidative stress. Interestingly, α-SYN possesses ferrireductase activity and α-SYN expression underlies iron mediated translational control via RNA stem loop structures. Despite a correlation between progressive putaminal atrophy and iron accumulation as well as clinical decline, it remains unclear whether pathologic iron accumulation in MSA is a secondary event in the cascade of neuronal degeneration rather than a primary cause. This review summarizes the current knowledge of iron in MSA and gives evidence for perturbed iron homeostasis as a potential pathogenic factor in MSA-associated neurodegeneration.

Magnetic resonance imaging for the diagnosis of Parkinson's disease

The differential diagnosis of parkinsonian syndromes is considered one of the most challenging in neurology and error rates in the clinical diagnosis can be high even at specialized centres. Despite several limitations, magnetic resonance imaging (MRI) has undoubtedly enhanced the diagnostic accuracy in the differential diagnosis of neurodegenerative parkinsonism over the last three decades. This review aims to summarize research findings regarding the value of the different MRI techniques, including advanced sequences at high- and ultra-high-field MRI and modern image analysis algorithms, in the diagnostic work-up of Parkinson's disease. This includes not only the exclusion of alternative diagnoses for Parkinson's disease such as symptomatic parkinsonism and atypical parkinsonism, but also the diagnosis of early, new onset, and even prodromal Parkinson's disease.

[Expanding concept of clinical conditions and symptoms in multiple system atrophy]

Multiple system atrophy (MSA) is an adult-onset, progressive neurodegenerative disorder. MSA patients show various phenotypes during the course of their illness including parkinsonism, cerebellar ataxia, autonomic failure, and pyramidal signs. MSA is classified into the parkinsonian (MSA-P) or cerebellar (MSA-C) variant depending on the clinical motor phenotype at presentation. MSA-P and MSA-C are predominant in Western countries and Japan, respectively. The mean age at onset is 55 to 60 years. Prognosis ranges from 6 to 10 years, but some cases survive for more than 15 years. Early and severe autonomic failure is a poor prognostic factor. MSA patients sometimes present with isolated autonomic failure or motor symptoms/signs, and the median duration from onset to the concomitant appearance of motor and autonomic symptoms was approximately 2 years in our previous study. As the presence of the combination of motor and autonomic symptoms is essential for the current diagnostic criteria, early diagnosis is difficult when patients present with isolated autonomic failure or motor symptoms/signs. We experienced MSA patients who died before presentation of the motor symptoms/signs diagnostic for MSA (i.e., premotor MSA). Detection of the nature of autonomic failure consistent with MSA and identification of the dysfunctional anatomical sites may increase the probability of a diagnosis of premotor MSA. Dementia is another problem in MSA. Although dementia had been thought to be rare in MSA, frontal lobe dysfunction is observed frequently during the early course of the illness. Magnetic resonance imaging can show progressive cerebral atrophy in longstanding cases. More recently, MSA patients presenting with frontotemporal dementia preceding the presence of motor and autonomic manifestations diagnostic of MSA have been reported. Novel diagnostic criteria based on an expanding concept of the clinical conditions and symptoms of MSA will be needed for the development of disease-modifying therapies and better management.

Role of Magnetic Resonance Imaging in the Diagnosis of Multiple System Atrophy

Background

Multiple system atrophy (MSA) is a rapidly progressing neurodegenerative disorder without effective disease-modifying therapies. Because of a lack of reliable diagnostic biomarkers, there has been increasing interest in using magnetic resonance imaging (MRI) to improve the diagnostic accuracy of MSA.

Methods

This review summarizes recent literatures on the role of MRI in the diagnosis of MSA.

Results

Several MRI abnormalities on conventional MRI already are included in the current diagnostic criteria for MSA. Other features on conventional MRI are also used to make a diagnosis of MSA or to rule out alternative diagnoses. On the other hand, some of the MRI findings that were previously considered suggestive of a diagnosis of MSA are now being challenged, because it turned out that they were not as specific to MSA as previously thought. More advanced MRI modalities, including susceptibility-weighted imaging, diffusion-weighted imaging, diffusion tensor imaging, voxel-based morphometry, and cortical thickness analysis, are now used to study the changes in the brains of patients with MSA. Furthermore, studies have produced promising results demonstrating the use of MRI as a tool for monitoring and assessing disease progression in MSA.

Conclusions

MRI is useful and indispensable in the diagnosis of MSA and also possibly for monitoring disease progression. In this regard, well-designed, long-term, prospective studies on large numbers of patients are needed.

Volume of Interest Analysis of Spatially Normalized PRESTO Imaging to Differentiate between Parkinson Disease and Atypical Parkinsonian Syndrome

Purpose:

Various magnetic resonance imaging (MRI) techniques including T₂*-weighted imaging, susceptibility-weighted imaging, and MR relaxometry had been performed to evaluate different patterns of brain iron depositions in Parkinsonian syndrome. The aim of the present study was to evaluate the diagnostic value of a volume of interest (VOI) analysis on the principles of echo shifting with a train of observations (PRESTO) imaging using the statistical parametric mapping (SPM) 8 and the WFU PickAtlas program for the diagnosis of Parkinsonian syndrome.

Methods:

Fifty subjects, including 13 with the Parkinsonian variant of multiple system atrophy (MSA-P), 12 with progressive supranuclear palsy (PSP), 12 with Parkinson’s disease (PD) and 13 controls were evaluated in this study. After the spatial normalization of PRESTO images on SPM8, the WFU PickAtlas program was performed to create target VOIs in the putamen, red nucleus, substantia nigra, subthalamic nucleus, and dentate nucleus. The signal intensity ratio (SIR) was calculated by normalizing the signal of each VOI to that of the cerebrospinal fluid space. These SIRs were used as determinants in receiver operating characteristic (ROC) analyses.

Results:

SIR of the putamen was significantly lower in MSA-P than in PSP (P = 0.0051) and controls (P = 0.0004). In contrast, SIR of the red nucleus was significantly lower in PSP than in MSA-P (P = 0.0003), PD (P = 0.0029), and controls (P = 0.0011). In ROC analyses, SIR of the putamen exhibited the highest areas under the curves (AUCs) of 0.83 (vs. PSP) and 0.91 (vs. controls) in the diagnosis of MSA-P. On the other hand, SIR of the red nucleus exhibited the highest AUCs of 0.87 (vs. MSA-P), 0.90 (vs. PD), and 0.89 (vs. controls) in the diagnosis of PSP.

Conclusions:

The VOI analysis based on spatially normalized PRESTO images may be useful for depicting hypointensity, indicative of abnormal iron depositions, of the putamen and red nucleus in the diagnosis of MSA-P and PSP.

Differentiation of Parkinsonism-Predominant Multiple System Atrophy from Idiopathic Parkinson Disease Using 3T Susceptibility-Weighted MR Imaging, Focusing on Putaminal Change and Lesion Asymmetry

BACKGROUND AND PURPOSE

Asymmetric presentation of clinical feature in parkinsonism is common, but correlatable radiologic feature is not clearly defined. Our aim was to evaluate 3T susceptibility-weighted imaging findings for differentiating parkinsonism-predominant multiple system atrophy from idiopathic Parkinson disease, focusing on putaminal changes and lesion asymmetry.

MATERIALS AND METHODS

This retrospective cohort study included 27 patients with parkinsonism-predominant multiple system atrophy and 50 patients with idiopathic Parkinson disease diagnosed clinically. Twenty-seven age-matched subjects without evidence of movement disorders who underwent SWI were included as the control group. A consensus was reached by 2 radiologists who visually assessed SWI for the presence of putaminal atrophy and marked signal hypointensity on each side of the posterolateral putamen. We also quantitatively measured putaminal width and phase-shift values.

RESULTS

The mean disease duration was 4.7 years for the patients with parkinsonism-predominant multiple system atrophy and 7.8 years for the patients with idiopathic Parkinson disease. In the patients with parkinsonism-predominant multiple system atrophy, putaminal atrophy was frequently observed (14/27, 51.9%) and was most commonly found in the unilateral putamen (13/14). Marked signal hypointensity was observed in 12 patients with parkinsonism-predominant multiple system atrophy (44.4%). No patients with idiopathic Parkinson disease or healthy controls showed putaminal atrophy or marked signal hypointensity. Quantitatively measured putaminal width, phase-shift values, and the ratio of mean phase-shift values for the dominant and nondominant sides were significantly different between the parkinsonism-predominant multiple system atrophy group and the idiopathic Parkinson disease and healthy control groups (P < .001).

CONCLUSIONS

3T SWI can visualize putaminal atrophy and marked signal hypointensity in patients with parkinsonism-predominant multiple system atrophy with high specificity. Furthermore, it clearly demonstrates the dominant side of putaminal changes, which correlate with the contralateral symptomatic side of patients.

Significance of the hot-cross bun sign on T2*-weighted MRI for the diagnosis of multiple system atrophy

Although the sensitive detection of putaminal iron deposition by T2*-weighted imaging (T2*-WI) is of diagnostic value for multiple system atrophy (MSA), the diagnostic significance of the pontine hot-cross bun (HCB) sign with increased ferritin-bound iron in the background remains unknown. We retrospectively evaluated the cases of 33 patients with cerebellar-form MSA (MSA-C) and 21 with MSA of the parkinsonian form (MSA-P) who underwent an MRI study with a 1.5-T system. Visualization of the HCB sign, posterior putaminal hypointensity and putaminal hyperintense rim on T2*-WI was assessed by two neurologists independently using an established visual grade, and were compared with those on T2-weighted imaging (T2-WI). The visual grade of pontine and putaminal signal changes was separately assessed for probable MSA (advanced stage) and possible MSA (early stage). T2*-WI demonstrated significantly higher grades of HCB sign than T2-WI (probable MSA-C, n = 27, p < 0.001; possible MSA-C, n = 6, p < 0.05; probable MSA-P, n = 13, p < 0.01). The visual grade of the HCB sign on T2*-WI in the possible MSA-C patients was comparable to that in the probable MSA-C patients. Although the HCB sign in MSA-P was of lower visual grade than in MSA-C even on T2*-WI, some patients showed evolution of the HCB sign preceding the appearance of the putaminal changes. These findings suggest that T2*-WI is of extreme value for detecting the HCB sign, which is often cited as a hallmark of MSA. The appearance of the HCB sign on T2*-WI might not only support but also improve the diagnosis of MSA.

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.

[Cutting-edge MRI techniques for studying neurological diseases focusing on spinocerebellar degeneration]

This symposium discusses the utility of the different MR techniques in the diagnosis and management of spinocerebellar degeneration (SCD). Conventional MRI is widely used and can show characteristic signal abnormalities such as putaminal hyperintensity, hyperintense putaminal rim, putaminal hypointensity, hot cross bun sign in the pontine base, and hyperintensity in the middle cerebellar peduncles strengthening a diagnosis of multiple system atrophy (MSA). However, the diagnostic utility of these signal abnormalities in early MSA remains restricted. In addition, it should be considered that different magnetic field strengths and sequences could be influenced on the findings resulting false negative. On the other hand, proton magnetic resonance spectroscopy, diffusion weighted imaging (DWI), diffusion tensor imaging (DTI) and voxel based morphometry (VBM) in the pontine base, cerebellum, and putamen will be informative in the early diagnosis of MSA and other SCD prior to conventional MRI changes and even before any clinical manifestation of symptoms. Particularly, DWI, DTI, and VBM are expected to have potential as surrogate markers of disease progression. Further prospective and large studies including earlier disease stages will be needed to clarify whether these novel MR techniques will aid in the future sets of diagnostic criteria and therapeutic trials.

Recent advances in structural MRI in Parkinson’s disease and atypical parkinsonian syndromes

SUMMARY In the past 2 years, technical developments in conventional and advanced MRI, such as ultra-high-field MRI or mapping of brain mineralization, has allowed novel insights into the nature of Parkinson’s disease (PD) and atypical parkinsonian syndromes, which may aid diagnostic accuracy and differential diagnosis. In addition, sophisticated post-processing analyses, such as morphometry- and surface-based classifications and automated whole-brain analyses, have become available; in PD, this has led to direct visualization of structural substantia nigra abnormalities, monitoring disease progression or screening for brain atrophy associated with dementia. Based on conventional MRI, new MRI rating scales have been established for progressive supranuclear palsy and multiple system atrophy and have been further assessed with a view to their diagnostic accuracy. Clinicopathological series of patients with tauopathies imply that correlations between clinical syndromes, imaging patterns and underlying histopathology are not always strong. Here, some of the issues related to conventional and advanced MRI for the diagnostic accuracy of PD and atypical parkinsonian syndromes are reviewed.

[The diagnosis of neurodegenerative disorders based on clinical and pathological findings using an MRI approach]

Diffusion tensor imaging and voxel based morphometry are efficient in the diagnosis of neurodegenerative disorders, however, these technologies are available at a limited number of facilities. Thus, conventional MRI remains important in the diagnosis of neurodegenerative disorders. Dorsolateral putaminal hyperintensity (DPH) and hot cross bun sign discriminate Parkinson's disease from multiple system atrophy (MSA). However, differences in magnetic field strength and sequence affect the sensitivity of DPH, and mild DPH may be observed in normal elderly subjects. Patients with progressive supranuclear palsy (PSP) presenting Richardson's syndrome show midbrain tegmentum atrophy, but Parkinsonian PSP (PSP-P) and pure akinesia with gait freezing, which are other phenotypes of PSP, may not show especially during early course of illness. In patients with corticobasal degeneration (CBD), asymmetrical cerebral atrophy corresponding with corticobasal syndrome (CBS) may be a characteristic finding. However, at autopsy, CBS patients presenting asymmetrical cerebral atrophy have CBD as the underlying pathology in approximately 50% of PSP patients. The sensitivity and specificity of MRI for the diagnosis of MSA, PSP, and CBD is based generally on clinical diagnostic criteria. Diagnosis based on MRI has limitations, and, therefore, we should reconsider our diagnoses, particularly during the early course of illness.

Hyperintense putaminal rim at 1.5 T: prevalence in normal subjects and distinguishing features from multiple system atrophy

Background

Hyperintense putaminal rim (HPR) is an important magnetic resonance imaging (MRI) sign for multiple system atrophy (MSA). Recent studies have suggested that it can also be observed in normal subjects at 3 T. Whether it can be observed in normal subjects at 1.5 T is not known. This study aimed to determine whether HPR could be observed in normal subjects at 1.5 T; and if so, to establish its prevalence, the MRI characteristics, and the features which distinguish from HPR in MSA patients.

Methods

Axial T2-weighted images of 130 normal subjects were evaluated for the prevalence of HPR, its age and gender distribution, laterality, maximum dimension, association with hypointensity of nearby putamen, and presence of discontinuity. To distinguish from that observed in MSA, axial T2-weighted images of 6 MSA patients with predominant parkinsonism (MSA-P) and 15 MSA patients with predominant cerebellar symptoms (MSA-C) were also evaluated. The characteristics of HPR were compared between these patients and age-matched normal subjects. The mean diffusivity (MD) values of putamen were also compared. Fisher’s exact test, t-test, and one way analysis of variance were used to determine significance at corrected p < 0.05.

Results

HPR was observed in 38.5% of normal subjects. Age and gender predilection and laterality were not observed. In most cases, it occupied the full length or anterior half of the lateral margin of putamen, and was continuous throughout its length. Maximum transverse dimension was 2 mm. There was no association with hypointensity of nearby putamen. However, in MSA-P, HPR was located predominantly at the posterolateral aspect of putamen, and associated with putaminal atrophy. Discontinuity of HPR was more frequently observed in MSA-P. On visual analysis, the characteristics of HPR were similar between MSA-C patients and normal subjects. Patients with MSA of either type had significantly higher MD values of putamen than normal subjects.

Conclusions

HPR can be observed in 38.5% of normal subjects at 1.5 T. Thin linear hyperintensity without discontinuity, occupying the full length or anterior half of the lateral margin of the putamen, is suggestive of “normal.” In doubtful cases, measurement of the MD values of nearby putamen may be valuable.

Movement disorders: role of imaging in diagnosis

Magnetic resonance imaging (MRI and single-photon emission computed tomography (SPECT) have a considerable role in the diagnosis of the single patient with movement disorders. Conventional MRI demonstrates symptomatic causes of parkinsonism but does not show any specific finding in Parkinson's disease (PD). However, SPECT using tracers of the dopamine transporter (DAT) demonstrates an asymmetric decrease of the uptake in the putamen and caudate from the earliest clinical stages. In other degenerative forms of parkinsonism, including progressive supranuclear palsy (PSP), multisystem atrophy (MSA), and corticobasal degeneration (CBD), MRI reveals characteristic patterns of regional atrophy combined with signal changes or microstructural changes in the basal ganglia, pons, middle and superior cerebellar peduncles, and cerebral subcortical white matter. SPECT demonstrates a decreased uptake of tracers of the dopamine D2 receptors in the striata of patients with PSP and MSA, which is not observed in early PD. MRI also significantly contributes to the diagnosis of some inherited hyperkinetic conditions including neurodegeneration with brain iron accumulation and fragile-X tremor/ataxia syndrome by revealing characteristic symmetric signal changes in the basal ganglia and middle cerebellar peduncles, respectively. A combination of the clinical features with MRI and SPECT is recommended for optimization of the diagnostic algorithm in movement disorders.

Significance of apparent diffusion coefficient measurement for the differential diagnosis of multiple system atrophy, progressive supranuclear palsy, and Parkinson's disease: evaluation by 3.0-T MR imaging

INTRODUCTION

The clinical differentiation of Parkinson's disease (PD) from multiple system atrophy (MSA) and progressive supranuclear palsy (PSP) may be challenging, especially in their early stages. The aim of this study was to evaluate the utility of apparent diffusion coefficient (ADC) measurement to distinguish among these degenerative disorders.

METHODS

Twenty-five MSA, 20 PSP, and 17 PD patients and 18 healthy controls were retrospectively studied. Axial diffusion-weighted and T2-weighted images were obtained using a 3-T MR system. Regions of interest (ROIs) were precisely placed in the midbrain, pons, putamen, globus pallidus, caudate nucleus, thalamus, superior cerebellar peduncle, middle cerebellar peduncle, cerebellar white matter, and cerebellar dentate nucleus, and the regional ADC (rADC) value was calculated in each ROI.

RESULTS

In MSA, rADC values in the pons, middle cerebellar peduncle, cerebellar white matter, and cerebellar dentate nucleus were significantly higher than in PSP, PD, and controls. Furthermore, rADC values in the posterior putamen were significantly higher in MSA than in PSP and controls. In PSP, rADC values were significantly higher in the globus pallidus and midbrain than in MSA, PD, and controls. Furthermore, rADC values in the caudate nucleus and superior cerebellar peduncle were significantly higher in PSP than in MSA and controls. In PD, there were no significant differences in the rADC values compared to in MSA, PSP, and controls in all regions.

CONCLUSION

Evaluation of rADC values in characteristic lesions in MSA, PSP, and PD by placing ROIs using 3-T systems can provide useful additional information for differentiating these disorders.

A new MRI rating scale for progressive supranuclear palsy and multiple system atrophy: validity and reliability

AIM

To evaluate a standardised MRI acquisition protocol and a new image rating scale for disease severity in patients with progressive supranuclear palsy (PSP) and multiple systems atrophy (MSA) in a large multicentre study.

METHODS

The MRI protocol consisted of two-dimensional sagittal and axial T1, axial PD, and axial and coronal T2 weighted acquisitions. The 32 item ordinal scale evaluated abnormalities within the basal ganglia and posterior fossa, blind to diagnosis. Among 760 patients in the study population (PSP = 362, MSA = 398), 627 had per protocol images (PSP = 297, MSA = 330). Intra-rater (n = 60) and inter-rater (n = 555) reliability were assessed through Cohen's statistic, and scale structure through principal component analysis (PCA) (n = 441). Internal consistency and reliability were checked. Discriminant and predictive validity of extracted factors and total scores were tested for disease severity as per clinical diagnosis.

RESULTS

Intra-rater and inter-rater reliability were acceptable for 25 (78%) of the items scored (≥ 0.41). PCA revealed four meaningful clusters of covarying parameters (factor (F) F1: brainstem and cerebellum; F2: midbrain; F3: putamen; F4: other basal ganglia) with good to excellent internal consistency (Cronbach α 0.75-0.93) and moderate to excellent reliability (intraclass coefficient: F1: 0.92; F2: 0.79; F3: 0.71; F4: 0.49). The total score significantly discriminated for disease severity or diagnosis; factorial scores differentially discriminated for disease severity according to diagnosis (PSP: F1-F2; MSA: F2-F3). The total score was significantly related to survival in PSP (p<0.0007) or MSA (p<0.0005), indicating good predictive validity.

CONCLUSIONS

The scale is suitable for use in the context of multicentre studies and can reliably and consistently measure MRI abnormalities in PSP and MSA. Clinical Trial Registration Number The study protocol was filed in the open clinical trial registry (http://www.clinicaltrials.gov) with ID No NCT00211224.

Utility of the fluid-attenuated inversion recovery sequence in detecting a hyperintense putaminal rim in multiple system atrophy-parkinsonism: a preliminary study

OBJECTIVE

To investigate the utility of fluid-attenuated inversion recovery (FLAIR) imaging for diagnosing multiple system atrophy-parkinsonism (MSA-P).

METHODS

We retrospectively evaluated 49 subjects (19 with MSA-P including 11 with early-stage disease, 15 with Parkinson's disease and 15 matched controls) in order to compare the diagnostic value of FLAIR imaging to detect a hyperintense putaminal rim (HPR) with that of T(2)-weighted (T2W) imaging.

RESULTS

Compared with T2W imaging, FLAIR imaging detected HPR more conspicuously in the 19 MSA-P patients (p = 0.01); this trend was also observed in 11 early-stage MSA-P patients (p = 0.01). Furthermore, FLAIR imaging tended to increase sensitivity of detecting HPR compared with T2W imaging (all patients: 89 vs. 58%, p = 0.07; early-stage patients: 100 vs. 55%, p = 0.06).

CONCLUSIONS

FLAIR imaging might be more useful for detecting HPR in MSA-P patients, even though they are at an early stage.

Use of MRI to monitor Parkinson’s disease

SUMMARY Objective biological markers of Parkinson’s disease (PD) are pivotal for confirming diagnosis, monitoring disease progression, and evaluating therapeutic interventions and disease-modifying agents. Structural and functional MRI provide an in vivo means to investigate the cortical and subcortical regions known to be affected in PD. In this article, we summarize how several MRI techniques, namely conventional MRI, iron-based MRI, volume-based MRI, diffusion tensor imaging, magnetic resonance spectroscopy and functional MRI have been used to assess the neurobiological changes related to the motor features of PD. We also discuss promising new research in which multiple MRI techniques are combined to achieve greater sensitivity and specificity of disease detection. Longitudinal research is necessary to establish MRI techniques as viable disease-state biomarkers of PD.