Transcranial sonography and [18F]fluorodeoxyglucose positron emission tomography for the differential diagnosis of parkinsonism: a head-to-head comparison

Systematic review-based guideline "Parkinson's disease" of the German Society of Neurology: diagnostic use of transcranial sonography

BACKGROUND AND OBJECTIVE

Transcranial brain parenchyma sonography (TCS) has been recommended as a tool for the early and differential diagnosis of Parkinson's disease (PD) in German and European clinical guidelines. Still, the brain structures to be examined for the diagnostic questions and the requirements for being a qualified investigator were not specified in detail. These issues have now been addressed in the 2023 update of the clinical guideline on PD by the German Society of Neurology (DGN).

METHODS

The recommendations were based on a systematic literature review following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines.

RESULTS

Three diagnostic questions were defined: (1) What is the accuracy of TCS in the differential diagnosis of PD versus atypical and secondary Parkinsonian syndromes? (2) What is the accuracy of TCS in the differential diagnosis of PD versus essential tremor? (3) What is the accuracy of TCS in the diagnosis of PD in persons with typical early symptoms, compared with the diagnosis established by clinical follow-up? The brain structures to be assessed and the level of recommendation were formulated for these questions. The training requirements for being regarded as qualified TCS investigator were stipulated by the responsible medical societies (German Society of Ultrasound in Medicine, DEGUM; German Society for Clinical Neurophysiology and Functional Imaging, DGKN). Finally, the recommendations for these diagnostic questions reached strong consensus (each ≥ 97%) of the guideline committee. Here, the details of review and recommendations are presented.

CONCLUSION

The updated guideline clarifies the diagnostic uses and limitations of TCS in PD.

Accuracy of 18F-FDG PET Imaging in Differentiating Parkinson's Disease from Atypical Parkinsonian Syndromes: A Systematic Review and Meta-Analysis

RATIONALE AND OBJECTIVE

To quantitatively assess the accuracy of 18F-FDG PET in differentiating Parkinson's Disease (PD) from Atypical Parkinsonian Syndromes (APSs).

METHODS

PubMed, Embase, and Web of Science databases were searched to identify studies published from the inception of the databases up to June 2024 that used 18F-FDG PET imaging for the differential diagnosis of PD and APSs. The risk of bias in the included studies was assessed using the QUADAS-2 or QUADAS-AI tool. Bivariate random-effects models were used to calculate the pooled sensitivity, specificity, and the area under the curves (AUC) of summary receiver operating characteristic (SROC).

RESULTS

24 studies met the inclusion criteria, involving a total of 1508 PD patients and 1370 APSs patients. 12 studies relied on visual interpretation by radiologists, of which the pooled sensitivity, specificity, and SROC-AUC for direct visual interpretation in diagnosing PD were 96% (95%CI: 91%, 98%), 90% (95%CI: 83%, 95%), and 0.98 (95%CI: 0.96, 0.99), respectively; the pooled sensitivity, specificity, and SROC-AUC for visual interpretation supported by univariate algorithms in diagnosing PD were 93% (95%CI: 90%, 95%), 90% (95%CI: 85%, 94%), and 0.96 (95%CI: 0.94, 0.97), respectively. 12 studies relied on artificial intelligence (AI) to analyze 18F-FDG PET imaging data. The pooled sensitivity, specificity, and SROC-AUC of machine learning (ML) for diagnosing PD were 87% (95%CI: 82%, 91%), 91% (95%CI: 86%, 94%), and 0.95 (95%CI: 0.93, 0.96), respectively. The pooled sensitivity, specificity, and SROC-AUC of deep learning (DL) for diagnosing PD were 97% (95%CI: 95%, 98%), 95% (95%CI: 89%, 98%), and 0.98 (95%CI: 0.96, 0.99), respectively.

CONCLUSION

18F-FDG PET has a high accuracy in differentiating PD from APS, among which AI-assisted automatic classification performs well, with a diagnostic accuracy comparable to that of radiologists, and is expected to become an important auxiliary means of clinical diagnosis in the future.

Differentiating progressive supranuclear palsy from other movement disorders using transcranial sonography: a systematic review and meta-analysis

Progressive supranuclear palsy (PSP) is an atypical parkinsonism that presents with different phenotypes. There are still no validated diagnostic biomarkers for early diagnosis of PSP. Transcranial sonography (TCS) is a promising tool in the differential diagnosis of parkinsonian disorders; however, there are no systematic investigations about the application of TCS in PSP patients. Therefore, we performed a systematic review and meta-analysis to discuss the role of TCS in diagnosing PSP by systematically searching PubMed, Cochrane Library, Chinese National Knowledge Infrastructure and Wan Fang databases. Of 66 obtained records, 16 articles, including 366 patients with PSP, were included. Our results showed the estimated random-effects pooled prevalence of substantia nigra hyperechogenicity in patients with PSP was 22% (95% CI 12-32%), lenticular nucleus hyperechogenicity was 70% (95% CI 52-82%), and enlarged third ventricle was 71% (95% CI 55-85%). Additionally, a normal echogenicity substantia nigra in TCS showed 70% sensitivity (95% CI 56-81%) and 86% specificity (95% CI 75-86%) to differentiate PSP from Parkinson's disease. In conclusion, TCS is an important supplementary biomarker for diagnosing PSP. At the same time, the diagnostic value of TCS in discriminating PSP from other atypical parkinsonism and between different PSP phenotypes needs further exploration.

Transcranial ultrasonography to detect intracranial pathology: A systematic review and meta-analysis

BACKGROUND AND PURPOSE

Transcranial ultrasonography (TCU) can be a useful diagnostic tool in evaluating intracranial pathology in patients with limited or delayed access to routine neuroimaging in critical care or austere settings. We reviewed available literature investigating the diagnostic utility of TCU for detecting pediatric and adult patient's intracranial pathology in patients with intact skulls and reported diagnostic accuracy measures.

METHODS

We performed a systematic review of PubMed® , Cochrane Library, Embase® , Scopus® , Web of Science™, and Cumulative Index to Nursing and Allied Health Literature databases to identify articles evaluating ultrasound-based detection of intracranial pathology in comparison to routine imaging using broad Medical Subject Heading sets. Two independent reviewers reviewed the retrieved articles for bias using the Quality Assessment of Diagnostic Accuracy Studies tools and extracted measures of diagnostic accuracy and ultrasound parameters. Data were pooled using meta-analysis implementing a random-effects approach to examine the sensitivity, specificity, and accuracy of ultrasound-based diagnosis.

RESULTS

A total of 44 studies out of the 3432 articles screened met the eligibility criteria, totaling 2426 patients (Mean age: 60.1 ± 14.52 years). We found tumors, intracranial hemorrhage (ICH), and neurodegenerative diseases in the eligible studies. Sensitivity, specificity, and accuracy of TCU and their 95% confidence intervals were 0.80 (0.72, 0.89), 0.71 (0.59, 0.82), and 0.76 (0.71, 0.82) for neurodegenerative diseases; 0.88 (0.74, 1.02), 0.81 (0.50, 1.12), and 0.94 (0.92, 0.96) for ICH; and 0.97 (0.92, 1.03), 0.99 (0.96, 1.01), and 0.99 (0.97, 1.01) for intracranial masses. No studies reported ultrasound presets.

CONCLUSIONS

TCU has a reasonable sensitivity and specificity for detecting intracranial pathology involving ICH and tumors with clinical applications in remote locations or where standard imaging is unavailable. Future studies should investigate ultrasound parameters to enhance diagnostic accuracy in diagnosing intracranial pathology.

Is MRPI 2.0 More Useful than MRPI and M/P Ratio in Differential Diagnosis of PSP-P with Other Atypical Parkinsonisms?

Differential diagnosis of progressive supranuclear palsy remains difficult, especially when it comes to the parkinsonism predominant type (PSP-P), which has a more favorable clinical course. In this entity, especially during the advanced stages, significant clinical overlaps with other tauopathic parkinsonian syndromes and multiple system atrophy (MSA) can be observed. Among the available additional diagnostic methods in every-day use, magnetic resonance imaging (MRI) focused specifically on the evaluation of the mesencephalon seems to be crucial as it is described as a parameter associated with PSP. There is growing interest in relation to more advanced mesencephalic parameters, such as the magnetic resonance parkinsonism index (MRPI) and MRPI 2.0. Based on the evaluation of 74 patients, we demonstrate that only the mesencephalon/pons ratio and MRPI show a significant difference between PSP-P and MSA-parkinsonian type (MSA-P). Interestingly, this differential feature was not maintained by MRPI 2.0. The mesencephalon to pons ratio (M/P), MRPI and MRPI 2.0 were not found to be feasible for the differentiation of PSP-P from other atypical tauopathic syndromes.

Brain topography on adult ultrasound images: Techniques, interpretation, and image library

BACKGROUND AND PURPOSE

Many studies have explored the possibility of using cranial ultrasound for discerning intracranial pathologies like tumors, hemorrhagic stroke, or subdural hemorrhage in clinical scenarios where computer tomography may not be accessible or feasible. The visualization of intracranial anatomy on B-mode ultrasound is challenging due to the presence of the skull that limits insonation to a few segments on the temporal bone that are thin enough to allow transcranial transmission of sound. Several artifacts are produced by hyperechoic signals inherent in brain and skull anatomy when images are created using temporal windows.

METHODS

While the literature has investigated the accuracy of diagnosis of intracranial pathology with ultrasound, we lack a reference source for images acquired on cranial topography on B-mode ultrasound to illustrate the appearance of normal and abnormal structures of the brain and skull. Two investigators underwent hands-on training in Cranial point-of-care ultrasound (c-POCUS) and acquired multiple images from each patient to obtain the most in-depth images of brain to investigate all visible anatomical structures and pathology within 24 hours of any CT/MRI imaging done.

RESULTS

Most reproducible structures visible on c-POCUS included bony parts and parenchymal structures. Transcranial and abdominal presets were equivalent in elucidating anatomical structures. Brain pathology like parenchymal hemorrhage, cerebral edema, and hydrocephalus were also visualized.

CONCLUSIONS

We present an illustrated anatomical atlas of cranial ultrasound B-mode images acquired in various pathologies in a critical care environment and compare our findings with published literature by performing a scoping review of literature on the subject.

Transcranial sonography in differential diagnosis of Parkinson disease and other movement disorders

Background:

Reports evaluating the efficacy of transcranial sonography (TCS) for the differential diagnosis of Parkinson disease (PD) and other movement disorders in China are scarce. Therefore, this study aimed to assess the application of TCS for the differential diagnosis of PD, multiple system atrophy (MSA), progressive supranuclear palsy (PSP), and essential tremor (ET) in Chinese individuals.

Methods:

From 2017 to 2019, 500 inpatients treated at the Department of Dyskinesia, Beijing Tiantan Hospital, Capital Medical University underwent routine transcranial ultrasound examination. The cross-sections at the midbrain and thalamus levels were scanned, and the incidence rates of substantia nigra (SN) positivity and the incidence rates of lenticular hyperechoic area were recorded. The echo of the SN was manually measured.

Results:

Of the 500 patients, 125 were excluded due to poor signal in temporal window sound transmission. Among the 375 individuals with good temporal window sound transmission, 200 were diagnosed with PD, 90 with ET, 50 with MSA, and 35 with PSP. The incidence rates of SN positivity differed significantly among the four patient groups (χ² = 121.061, P < 0.001). Between-group comparisons were performed, and the PD group showed a higher SN positivity rate than the ET (χ² = 94.898, P < 0.017), MSA (χ² = 57.619, P < 0.017), and PSP (χ² = 37.687, P < 0.017) groups. SN positivity showed a good diagnostic value for differentiating PD from the other three movement diseases, collectively or individually. The incidences of lenticular hyperechoic area significantly differed among the four patient groups (χ² = 38.904, P < 0.001). Next, between-group comparisons were performed. The lenticular hyperechoic area was higher in the PD group than in the ET (χ² = 6.714, P < 0.017) and MSA (χ² = 18.680, P < 0.017) groups but lower than that in the PSP group (χ² = 0.679, P > 0.017).

Conclusion:

SN positivity could effectively differentiate PD from ET, PSP, and MSA in a Chinese population.

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.

Multiple system atrophy

Multiple system atrophy (MSA) is a sporadic, adult-onset, relentlessly progressive neurodegenerative disorder, clinically characterized by various combinations of autonomic failure, parkinsonism and ataxia. The neuropathological hallmark of MSA are glial cytoplasmic inclusions consisting of misfolded α-synuclein. Selective atrophy and neuronal loss in striatonigral and olivopontocerebellar systems underlie the division into two main motor phenotypes of MSA-parkinsonian type and MSA-cerebellar type. Isolated autonomic failure and REM sleep behavior disorder are common premotor features of MSA. Beyond the core clinical symptoms, MSA manifests with a number of non-motor and motor features. Red flags highly specific for MSA may provide clues for a correct diagnosis, but in general the diagnostic accuracy of the second consensus criteria is suboptimal, particularly in early disease stages. In this chapter, the authors discuss the historical milestones, etiopathogenesis, neuropathological findings, clinical features, red flags, differential diagnosis, diagnostic criteria, imaging and other biomarkers, current treatment, unmet needs and future treatments for MSA.

Transcranial B-Mode Sonography in Movement Disorders

Applying a 2-4MHz probe at the temporal bone window transcranial B-mode sonography (TCS) enables the depiction of the brain parenchyma through the intact skull. Meanwhile it has been applied for the diagnosis and the differential diagnosis of movement disorders for decades. In the first part of this chapter, we summarize the technical requirements and describe the ultrasound method for optimal TCS examination. Imaging planes and the relevant structures are explained in detail. In the second part of the chapter, we focus on the role of substantia nigra hyperechogenicity for the diagnosis of Parkinson's disease (PD) and prodromal PD. In this part, we also mention the role of TCS in atypical and secondary Parkinsonian syndromes and other movement disorders. Summarizing all these information we explain how TCS can be helpful for the differential diagnosis of movement disorders. The current data show that TCS is an easily applicable and economic imaging method which can be used as an additional tool for the diagnosis of PD with a high sensitivity (>85%), specificity (>80%) and inter-rater reliability (>84%) as well as for the differential diagnosis of movement disorders. Lately, TCS has also been utilized in further areas such as the detection of individuals at risk for PD or the determination of electrode localization in patients with deep brain stimulation. An insufficient temporal bone window especially in the elderly and the necessity of an experienced investigator are limitations of this method.

Clinical utility of FDG PET in Parkinson's disease and atypical parkinsonism associated with dementia

Purpose

There are no comprehensive guidelines for the use of FDG PET in the following three clinical scenarios: (1) diagnostic work-up of patients with idiopathic Parkinson’s disease (PD) at risk of future cognitive decline, (2) discriminating idiopathic PD from progressive supranuclear palsy, and (3) identifying the underlying neuropathology in corticobasal syndrome.

Methods

We therefore performed three literature searches and evaluated the selected studies for quality of design, risk of bias, inconsistency, imprecision, indirectness and effect size. Critical outcomes were the sensitivity, specificity, accuracy, positive/negative predictive value, area under the receiving operating characteristic curve, and positive/negative likelihood ratio of FDG PET in detecting the target condition. Using the Delphi method, a panel of seven experts voted for or against the use of FDG PET based on published evidence and expert opinion.

Results

Of 91 studies selected from the three literature searches, only four included an adequate quantitative assessment of the performance of FDG PET. The majority of studies lacked robust methodology due to lack of critical outcomes, inadequate gold standard and no head-to-head comparison with an appropriate reference standard. The panel recommended the use of FDG PET for all three clinical scenarios based on nonquantitative evidence of clinical utility.

Conclusion

Despite widespread use of FDG PET in clinical practice and extensive research, there is still very limited good quality evidence for the use of FDG PET. However, in the opinion of the majority of the panellists, FDG PET is a clinically useful imaging biomarker for idiopathic PD and atypical parkinsonism associated with dementia.

Transcranial sonography in idiopathic REM sleep behavior disorder and multiple system atrophy

AIM

We investigated preclinical abnormalities as revealed by transcranial sonography (TCS) in patients with idiopathic rapid eye movement sleep behavior disorder (iRBD) compared with those revealed in patients with multiple system atrophy (MSA) or Parkinson's disease (PD) and in normal controls.

METHODS

Twenty-two patients with iRBD, 21 patients with MSA, 22 patients with PD, and 21 normal controls were included in this study. All participants underwent one night of video-polysomnography monitoring, and the sleep parameters were analyzed using Polysmith software and by visual analysis. TCS was performed following a standardized procedure. The echogenicity of the substantia nigra and basal ganglia were evaluated.

RESULTS

A greater proportion of PD patients were found to have substantia nigra hyperechogenicity (86.4%) when compared to iRBD patients (31.8%), MSA patients (23.8%), and normal controls (4.8%) (P < 0.001). Fourteen MSA patients (66.7%) and 11 iRBD patients (50.0%) had hyperechogenicity in the basal ganglia, whereas hyperechogenicity in the basal ganglia was less frequent in PD patients (18.2%) and normal controls (9.5%) (P < 0.001). Poor sleep efficiency, less stage II sleep time, and more periodic leg movements were found in MSA and PD patients, whereas iRBD patients had almost normal sleep.

CONCLUSION

Some iRBD patients had basal ganglia hyperechogenicity that was similar to that observed in MSA, which may represent another possible convert direction. The present study further confirmed iRBD as a prodromal stage of synucleinopathy. TCS could detect subclinical changes and thus might provide useful markers for identifying individuals at increased risk for developing a synucleinopathy.

Developments in the role of transcranial sonography for the differential diagnosis of parkinsonism

In the last two decades transcranial sonography (TCS) has developed as a valuable, supplementary tool in the diagnosis and differential diagnosis of movement disorders. In this review, we highlight recent evidence supporting TCS as a reliable method in the differential diagnosis of parkinsonism, combining substantia nigra (SN), basal ganglia and ventricular system findings. Moreover, several studies support SN hyperechogenicity as one of most important risk factors for Parkinson's disease (PD). The advantages of TCS include short investigation time, low cost and lack of radiation. Principal limitations are still the dependency on the bone window and operator experience. New automated algorithms may reduce the role of investigator skill in the assessment and interpretation, increasing TCS diagnostic reliability. Based on the convincing evidence available, the EFNS accredited the method of TCS a level A recommendation for supporting the diagnosis of PD and its differential diagnosis from secondary and atypical parkinsonism. An increasing number of training programmes is extending the use of this technique in clinical practice.

Therapeutic interventions in parkinsonism: Corticobasal degeneration

Corticobasal degeneration (CBD) is a progressive neurodegenerative disorder resulting from pathological accumulation of tau protein and is included in the spectrum of Atypical Parkinsonism. The typical clinical phenotype of CBD is characterized by the Corticobasal syndrome (CBS). In recent years it has become clear that the clinical picture of CBS may be caused by different pathological conditions, resulting in frequent misdiagnosis. CBD has high morbidity and poor prognosis with no effective therapies. In this review, we will discuss the symptomatic treatment, the palliative care and the disease modifying strategies currently in use. Symptomatic treatment in patients with CBD may sometimes be useful for improving motor (parkinsonism, dystonia and myoclonus) and non-motor (cognitive-behavioral) symptoms, but the effects are often unsatisfactory. In addition, non-pharmacological strategies and palliative care are useful integrating components of the multidisciplinary therapeutic approach for patients with CBD. Despite many efforts, a disease-modifying treatment is still unavailable for CBD.

Diagnosis and differential diagnosis of MSA: boundary issues

Because the progression of multiple system atrophy (MSA) is usually rapid and there still is no effective cause-related therapy, early and accurate diagnosis is important for the proper management of patients as well as the development of neuroprotective agents. However, despite the progression in the field of MSA research in the past few years, the diagnosis of MSA in clinical practice still relies largely on clinical features and there are limitations in terms of sensitivity and specificity, especially in the early course of the disease. Furthermore, recent pathological, clinical, and neuroimaging studies have shown that (1) MSA can present with a wider range of clinical and pathological features than previously thought, including features considered atypical for MSA; thus, MSA can be misdiagnosed as other diseases, and conversely, disorders with other etiologies and pathologies can be clinically misdiagnosed as MSA; and (2) several investigations may help to improve the diagnosis of MSA in clinical practice. These aspects should be taken into consideration when revising the current diagnostic criteria. This is especially true given that disease-modifying treatments for MSA are under investigation.

Substantia nigra hyperechogenicity in hypokinetic Huntington's disease patients

Substantia nigra (SN) hyperechogenicity can be detected by transcranial sonography (TCS) to assist the early diagnosis of idiopathic Parkinson's disease (IPD). This study prospectively investigated whether SN hyperechogenicity is also present in Huntington's disease (HD) patients with symptoms of hypokinesia and/or rigidity. All patients recruited to the study (n = 15) were characterised by hypokinesia and/or rigidity while nine of these patients also displayed chorea and/or dystonia. The control group included 15 individuals. Clinical examination was documented using the Unified Huntington's Disease Rating Scale (UHDRS). TCS examination revealed SN hyperechogenicity in 14/15 (93.3 %) patients (9/14 unilateral, 5/14 bilateral). Hyperechogenicity of the caudate and lentiform nuclei (CN, LN) was less frequent (CN: 80 % total, LN: 53.3 % total). This is the first study to assess SN hyperechogenicity in hypokinetic HD patients. Assuming that the primary sites of pathology in IPD and HD are the SN and the striatum, respectively, our observations suggest a functional impairment of the nigrostriatal system in HD, an effect that is potentially independent of the primarily-affected basal ganglia nucleus.

Neuroimaging in Parkinson disease: from research setting to clinical practice

Over the past three decades, neuroimaging studies-including structural, functional and molecular modalities-have provided invaluable insights into the mechanisms underlying Parkinson disease (PD). Observations from multimodal neuroimaging techniques have indicated changes in brain structure and metabolic activity, and an array of neurochemical changes that affect receptor sites and neurotransmitter systems. Characterization of the neurobiological alterations that lead to phenotypic heterogeneity in patients with PD has considerably aided the in vivo investigation of aetiology and pathophysiology, and the identification of novel targets for pharmacological or surgical treatments, including cell therapy. Although PD is now considered to be very complex, no neuroimaging modalities are specifically recommended for routine use in clinical practice. However, conventional MRI and dopamine transporter imaging are commonly used as adjuvant tools in the differential diagnosis between PD and nondegenerative causes of parkinsonism. First-line neuroimaging tools that could have an impact on patient prognosis and treatment strategies remain elusive. This Review discusses the lessons learnt from decades of neuroimaging research in PD, and the promising new approaches with potential applicability to clinical practice.