Sonographic discrimination of corticobasal degeneration vs progressive supranuclear palsy

Refining the clinical diagnosis of Parkinson's disease

Our ability to define, understand, and classify Parkinson's disease (PD) has undergone significant changes since the disorder was first described in 1817. Clinical features and neuropathologic signatures can now be supplemented by in-vivo interrogation of genetic and biological substrates of disease, offering great opportunity for further refining the diagnosis of PD. In this mini-review, we discuss the historical perspectives which shaped our thinking surrounding the definition and diagnosis of PD. We highlight the clinical, genetic, pathologic and biologic diversity which underpins the condition, and proceed to discuss how recent developments in our ability to define biologic and pathologic substrates of disease might impact PD definition, diagnosis, individualised prognostication, and personalised clinical care. We argue that Parkinson's 'disease', as currently diagnosed in the clinic, is actually a syndrome. It is the outward manifestation of any array of potential dysfunctional biologic processes, neuropathological changes, and disease aetiologies, which culminate in common outward clinical features which we term PD; each person has their own unique disease, which we can now define with increasing precision. This is an exciting time in PD research and clinical care. Our ability to refine the clinical diagnosis of PD, incorporating in-vivo assessments of disease biology, neuropathology, and neurogenetics may well herald the era of biologically-based, precision medicine approaches PD management. With this however comes a number of challenges, including how to integrate these technologies into clinical practice in a way which is acceptable to patients, promotes meaningful changes to care, and minimises health economic impact.

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.

An overview: Radiotracers and nano-radiopharmaceuticals for diagnosis of Parkinson's disease

Parkinson's disease (PD) is a widespread progressive neurodegenerative disease. Clinical diagnosis approaches are insufficient to provide an early and accurate diagnosis before a substantial of loss of dopaminergic neurons. PET and SPECT can be used for accurate and early diagnosis of PD by using target-specific radiotracers. Additionally, the importance of BBB penetrating targeted nanosystems has increased in recent years. This article reviews targeted radiopharmaceuticals used in clinics and novel nanocarriers for research purposes of PD imaging.

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.

The Significance of Asymmetry in the Assessment of Brain Perfusion in Atypical Tauopathic Parkinsonian Syndromes

Progressive supranuclear palsy syndrome (PSPS) and corticobasal syndrome (CBS) are clinical manifestations of tauopathic Parkinsonian syndromes. Due to their overlapping symptomatology, the differential diagnosis of these entities may be difficult when bounded to clinical assessment. The manifestations are commonly associated with pathological entities—corticobasal degeneration and progressive supranuclear palsy, which are four-repeat tauopathies. In this study, the authors attempted to find whether the asymmetry typically associated with CBS may be feasible in the interpretation of perfusion single-photon computed tomography. The analysis based on the examination of patients with progressive supranuclear palsy—Richardson syndrome (PSP-RS), progressive supranuclear palsy—Parkinsonism predominant (PSP-P), and corticobasal syndrome (CBS) revealed significant asymmetry of perfusion of the amygdala in corticobasal syndrome. The more pronounced abnormalities of perfusion were observed in the left amygdala among patients with more severe Parkinsonian syndromes in CBS on the right. This study shows that the comparison of the perfusion of tauopathic Parkinsonian syndromes should be extended by asymmetry analysis. Interestingly, the differentiating potential of brain perfusion is present in the comparison of CBS and PSP-RS, but not in CBS and PSP-P. This phenomenon could be explained by more distinct asymmetry in the perfusion observed in PSP-P, which diminishes the differentiating potential of this parameter when it comes to the comparison of PSP-P and CBS. To the best of our knowledge, this is the first study evaluating which structures can be interpreted as significantly asymmetrical in the context of perfusion in CBS.

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.

Neuroimaging Advances in Parkinson's Disease and Atypical Parkinsonian Syndromes

Parkinson's disease (PD) and atypical Parkinsonian syndromes are progressive heterogeneous neurodegenerative diseases that share clinical characteristic of parkinsonism as a common feature, but are considered distinct clinicopathological disorders. Based on the predominant protein aggregates observed within the brain, these disorders are categorized as, (1) α-synucleinopathies, which include PD and other Lewy body spectrum disorders as well as multiple system atrophy, and (2) tauopathies, which comprise progressive supranuclear palsy and corticobasal degeneration. Although, great strides have been made in neurodegenerative disease research since the first medical description of PD in 1817 by James Parkinson, these disorders remain a major diagnostic and treatment challenge. A valid diagnosis at early disease stages is of paramount importance, as it can help accommodate differential prognostic and disease management approaches, enable the elucidation of reliable clinicopathological relationships ideally at prodromal stages, as well as facilitate the evaluation of novel therapeutics in clinical trials. However, the pursuit for early diagnosis in PD and atypical Parkinsonian syndromes is hindered by substantial clinical and pathological heterogeneity, which can influence disease presentation and progression. Therefore, reliable neuroimaging biomarkers are required in order to enhance diagnostic certainty and ensure more informed diagnostic decisions. In this article, an updated presentation of well-established and emerging neuroimaging biomarkers are reviewed from the following modalities: (1) structural magnetic resonance imaging (MRI), (2) diffusion-weighted and diffusion tensor MRI, (3) resting-state and task-based functional MRI, (4) proton magnetic resonance spectroscopy, (5) transcranial B-mode sonography for measuring substantia nigra and lentiform nucleus echogenicity, (6) single photon emission computed tomography for assessing the dopaminergic system and cerebral perfusion, and (7) positron emission tomography for quantifying nigrostriatal functions, glucose metabolism, amyloid, tau and α-synuclein molecular imaging, as well as neuroinflammation. Multiple biomarkers obtained from different neuroimaging modalities can provide distinct yet corroborative information on the underlying neurodegenerative processes. This integrative "multimodal approach" may prove superior to single modality-based methods. Indeed, owing to the international, multi-centered, collaborative research initiatives as well as refinements in neuroimaging technology that are currently underway, the upcoming decades will mark a pivotal and exciting era of further advancements in this field of neuroscience.

Substantia Nigra Hyperechogenicity Reflects the Progression of Dopaminergic Neurodegeneration in 6-OHDA Rat Model of Parkinson's Disease

Parkinson’s disease (PD) is the second most common neurodegenerative disease, and there is still no effective way to stop its progress. Therefore, early detection is crucial for the prevention and the treatment of Parkinson’s disease. The current diagnosis of Parkinson’s disease, however, mainly depends on the symptoms, so it is necessary to establish a reliable imaging modality for PD diagnosis and its progression monitoring. Other studies and our previous ones demonstrated that substantia nigra hyperechogenicity (SNH) was detected by transcranial sonography (TCS) in the ventral midbrain of PD patients, and SNH is regarded as a characteristic marker of PD. The present study aimed to explore whether SNH could serve as a reliable imaging modality to monitor the progression of dopaminergic neurodegeneration of PD. The results revealed that the size of SNH was positively related with the degree of dopaminergic neuron death in PD animal models. Furthermore, we revealed that microglia activation contributed to the SNH formation in substantia nigra (SN) in PD models. Taken together, this study suggests that SNH through TCS is a promising imaging modality to monitor the progression of dopaminergic neurodegeneration of PD.

Comparative study of the substantia nigra echogenicity and 123I-Ioflupane SPECT in patients with synucleinopathies with and without REM sleep behavior disorder

OBJECTIVES

Hyperechogenicity of the substantia nigra (SN) and abnormal dopamine transporter-single-photon emission computed tomography (DAT-SPECT) are biomarkers commonly used in the assessment of prodromal synucleinopathy. Our goals were as follows: (1) to compare echogenicity of SN in idiopathic rapid eye movement (REM) behavior disorder (iRBD), Parkinson's disease (PD) without RBD (PD-noRBD), PD with RBD (PD + RBD), and control subjects; and (2) to examine association between SN degeneration assessed by DAT-SPECT and SN echogenicity.

PATIENTS/METHODS

A total of 61 subjects with confirmed iRBD were examined using Movement Disorders Society-unified PD rating scale (MDS-UPDRS), TCS (transcranial sonography) and DAT-SPECT. The results were compared with 44 patients with PD (25% PD + RBD) and with 120 age-matched healthy subjects.

RESULTS AND CONCLUSION

The abnormal SN area was found in 75.5% PD, 23% iRBD and 7.3% controls. Median SN echogenicity area in PD (0.27 ± 0.22 cm²) was higher compared to iRBD (0.07 ± 0.07 cm²; p < 0.0001) and controls (0.05 ± 0.03 cm²; p < 0.0001). SN echogenicity in PD + RBD was not significantly different from PD-noRBD (0.30 vs. 0.22, p = 0.15). Abnormal DAT-SPECT was found in 16 iRBD (25.4%) and 44 PD subjects (100%). No correlation between the larger SN area and corresponding putaminal binding index was found in iRBD (r = -0.13, p = 0.29), nor in PD (r = -0.19, p = 0.22). The results of our study showed that: (1) SN echogenicity area in iRBD was higher compared to controls, but the hyperechogenicity was present only in a minority of iRBD patients; (2) SN echogenicity and DAT-SPECT binding index did not correlate in either group; and (3) SN echogenicity does not differ between PD with/without RBD.

Transcranial brain sonography for Parkinsonian syndromes

Substantia nigra (SN) hyperechogenicity has been proved to be a characteristic finding for idiopathic Parkinson's disease (PD), occurring in more than 90% of the patients. This echofeature is owed to increased amounts of iron in the SN region and reflects a functional impairment of the nigrostriatal dopaminergic system. In a prospective blinded study in which a group of patients with early mild signs and symptoms of unclear Parkinsonism were followed until a definite clinical diagnosis of PD, the hyperechogenicity of the SN was demonstrated to be highly predictive of a final diagnosis of PD. For the diagnosis of PD in individuals with early motor symptoms, both the sensitivity and positive predictive value of SN hyperechogenicity were higher than 90% and both the specificity and negative predictive value were higher than 80%. For early differential diagnosis between PD and atypical Parkinsonian syndromes, the sensitivity and positive predictive value of SN hyperechogenicity were higher than 90%, and both the specificity and negative predictive value were higher than 80%. The diagnostic specificity is increased if combining the TCS findings of SN, lenticular nucleus and third ventricle. In asymptomatic adult subjects, SN hyperechogenicity, at least unilaterally, indicates a subclinical functional insufficiency of the nigrostriatal dopaminergic system. Recent papers revealed that SN hyperechogenicity might suggest preclinical PD. Reduced echogenicity of midbrain raphe indicates increased risk of depression in PD patients. Caudate nucleus hyperechogenicity has been associated with drug-induced psychosis, and frontal horn dilatation >20 mm with dementia. Transcranial brain sonography can be a valuable tool for managing patients with Parkinsonian signs and symptoms.

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.

The role of substantia nigra sonography in the differentiation of Parkinson's disease and multiple system atrophy

Background

The differential diagnosis of Parkinson's disease (PD) and multiple system atrophy (MSA) remains a challenge, especially in the early stage. Here, we assessed the value of transcranial sonography (TCS) to discriminate non-tremor dominant (non-TD) PD from MSA with predominant parkinsonism (MSA-P).

Methods

Eighty-six MSA-P patients and 147 age and gender-matched non-TD PD patients who had appropriate temporal acoustic bone windows were included in this study. All the patients were followed up for at least 2 years to confirm the initial diagnosis. Patients with at least one substantia nigra (SN) echogenic size ≥18 mm² were classified as hyperechogenic, those with at least one SN echogenic size ≥25 mm² was defined as markedly hyperechogenic.

Results

The frequency of SN hyperechogenicity in non-TD PD patients was significantly higher than that in MSA-P patients (74.1% vs. 38.4%, p <  0.001). SN hyperechogenicity discriminated non-TD PD from MSA-P with sensitivity of 74.1%, specificity of 61.6%, and positive predictive value of 76.8%. If marked SN hyperechogenicity was used as the cutoff value (≥ 25 mm²), the sensitivity decreased to 46.3%, but the specificity and positive predictive value increased to 80.2 and 80.0%. Additionally, in those patients with SN hyperechogenicity, positive correlation between SN hyperechogenicity area and disease duration was found in non-TD PD rather than in MSA-P patients. In this context, among early-stage patients with disease duration ≤3 years, the sensitivity, specificity and positive predictive value of SN hyperechogenicity further declined to 69.8%, 52.2%, and 66.7%, respectively.

Conclusions

TCS could help discriminate non-TD PD from MSA-P in a certain extent, but the limitation was also obvious with relatively low specificity, especially in the early stage.

Imaging biomarkers in Parkinson's disease and Parkinsonian syndromes: current and emerging concepts

Two centuries ago in 1817, James Parkinson provided the first medical description of Parkinson’s disease, later refined by Jean-Martin Charcot in the mid-to-late 19th century to include the atypical parkinsonian variants (also termed, Parkinson-plus syndromes). Today, Parkinson’s disease represents the second most common neurodegenerative disorder with an estimated global prevalence of over 10 million. Conversely, atypical parkinsonian syndromes encompass a group of relatively heterogeneous disorders that may share some clinical features with Parkinson’s disease, but are uncommon distinct clinicopathological diseases. Decades of scientific advancements have vastly improved our understanding of these disorders, including improvements in in vivo imaging for biomarker identification. Multimodal imaging for the visualization of structural and functional brain changes is especially important, as it allows a ‘window’ into the underlying pathophysiological abnormalities. In this article, we first present an overview of the cardinal clinical and neuropathological features of, 1) synucleinopathies: Parkinson’s disease and other Lewy body spectrum disorders, as well as multiple system atrophy, and 2) tauopathies: progressive supranuclear palsy, and corticobasal degeneration. A comprehensive presentation of well-established and emerging imaging biomarkers for each disorder are then discussed. Biomarkers for the following imaging modalities are reviewed: 1) structural magnetic resonance imaging (MRI) using T1, T2, and susceptibility-weighted sequences for volumetric and voxel-based morphometric analyses, as well as MRI derived visual signatures, 2) diffusion tensor MRI for the assessment of white matter tract injury and microstructural integrity, 3) proton magnetic resonance spectroscopy for quantifying proton-containing brain metabolites, 4) single photon emission computed tomography for the evaluation of nigrostriatal integrity (as assessed by presynaptic dopamine transporters and postsynaptic dopamine D2 receptors), and cerebral perfusion, 5) positron emission tomography for gauging nigrostriatal functions, glucose metabolism, amyloid and tau molecular imaging, as well as neuroinflammation, 6) myocardial scintigraphy for dysautonomia, and 7) transcranial sonography for measuring substantia nigra and lentiform nucleus echogenicity. Imaging biomarkers, using the ‘multimodal approach’, may aid in making early, accurate and objective diagnostic decisions, highlight neuroanatomical and pathophysiological mechanisms, as well as assist in evaluating disease progression and therapeutic responses to drugs in clinical trials.

Accuracy of transcranial brain parenchyma sonography in the diagnosis of dementia with Lewy bodies

BACKGROUND AND PURPOSE

Transcranial sonography (TCS) of the brain parenchyma is used to visualize alterations in the substantia nigra (SN) and it is applied for early diagnosis of Parkinson's disease. Our aim was to explore specific echogenic alterations of the SN in dementia with Lewy bodies (DLB) compared to Alzheimer's disease (AD).

METHODS

Seventy-one subjects underwent TCS: 22 DLB, 28 AD and 21 healthy elderly controls. Cognitive impairment, extrapyramidal signs, visual hallucinations, fluctuations and rapid eye movement sleep behaviour symptoms were investigated. TCS assessed SN hyperechogenicity and symmetry.

RESULTS

Transcranial sonography revealed SN hyperechogenicity in 100% of DLB compared to 50% of AD and 30% of controls. Mean SN echogenic area (cm(2) ) was 0.22 ± 0.03 in DLB, 0.15 ± 0.03 in AD and 0.14 ± 0.03 in controls (P < 0.0001). More than 50% of DLB presented a marked hyperechogenicity (cutoff value >0.22 cm(2) ) compared to only 10% of AD (P < 0.0003). DLB had symmetrical SN enlargement, whereas AD were mostly asymmetrical (P = 0.015). A combination of SN echogenic area and asymmetry index had a sensitivity of 88.9% and a specificity of 81.2% in discriminating DLB from AD (positive predictive value 85.7%, negative predictive value 85.7%). No association was found between SN hyperechogenicity and Unified Parkinson's Disease Rating Scale part III, Mini Mental State Examination or the presence of visual hallucinations.

CONCLUSIONS

Transcranial sonography may be a valid supportive tool in the diagnostic workup of neurodegenerative dementia helping clinicians to distinguish DLB from AD even at the early stages.

Transcranial Sonography Findings in Depression in Association With Psychiatric and Neurologic Diseases: A Review

The transcranial sonography (TCS) finding of reduced echogenicity of brainstem raphe (hypoechogenic BR) has been associated with depressive states. Here, we review the TCS studies in subjects with depressive disorders and with depression related to degenerative brain diseases, and compare the frequency and clinical correlates of hypoechogenic BR in these reports. Summarizing the data published so far, hypoechogenic BR is present in 67% (range, 37-95%) of depressed but only in 15% (5-36%) of nondepressed subjects without history of neurodegenerative disease. The finding of hypoechogenic BR in these subjects is associated with a relative risk of 3.03 (95% CI, 2.44-3.75; P < .001) of being diagnosed with depression. In patients with Parkinson's disease, hypoechogenic BR is present in 63% (35-92%) of depressed but only in 27% (10-62%) of nondepressed patients, resulting in a relative risk of 2.18 (95% CI, 1.80-2.66; P < .001) of being diagnosed with depression. Hypoechogenic BR is associated with depression in a number of neurological disorders such Huntington's disease, idiopathic Rapid Eye Movement (REM) sleep behavior disorder, myotonic dystrophies, and cerebral small vessel disease. Although some studies did not show any relationship between BR echogenicity and severity of depression, others suggest an association with higher severity of depression, or even with suicidal ideation. In one study BR hypoechogenicity was found to be associated with better responsivity to serotonin reuptake inhibitors. Further studies are warranted to compare the TCS findings of BR alteration with post-mortem histopathological findings, and with genetic variants related to cerebral serotonin metabolism.

Abnormal Echogenicity of the Substantia Nigra, Raphe Nuclei, and Third-Ventricle Width as Markers of Cognitive Impairment in Parkinsonian Disorders: A Cross-Sectional Study

Background. Patients with Parkinson's disease (PD) have a high risk of cognitive problems. Objective. This study assesses whether abnormal echogenicity of the substantia nigra (SN) and raphe nuclei (RN) and the diameter of third ventricle are markers of cognitive impairment in patients with PD and other forms of parkinsonism. Methods. 126 outpatients with early signs of parkinsonism underwent transcranial sonography (TCS). The scales for the outcome of Parkinson's disease cognition (SCOPA-COG) were used as cognitive measure. Definite neurological diagnosis was established after two-year follow-up. Results. One-third of the patients with PD and half of those with APS had signs of cognitive impairment. The echogenicity of the SN was not related to cognitive impairment. The diameter of the third ventricle was significantly larger in PD patients with cognitive impairment compared to those without. In patients with APS we found a significantly higher frequency of hypoechogenic RN in patients with cognitive problems. Conclusions. Cognitive impairment is already present in a substantial proportion of patients with PD and APS at first referral. In patients with APS the frequency of hypoechogenic RN points to the direction of other pathophysiology with more emphasis on deficits in the serotonergic neurotransmitter system. The larger diameter of the third ventricle in PD patients with cognitive impairment may reflect Alzheimer like brain atrophy, as has been reported in earlier studies.

Substantia Nigra Echogenicity Predicts Response to Drug Withdrawal in Suspected Drug-Induced Parkinsonism

Introduction

Response to drug withdrawal in patients with suspected drug-induced parkinsonism (DIP) is of prognostic and therapeutic importance, but cannot be predicted solely on clinical information. The aim of this study was to validate SN hyperechogenicity (SN+) assessed by transcranial sonography as a predictor of response to drug withdrawal in this group of patients.

Methods

Patients were diagnosed according to previously published criteria and prospectively included in the study. All patients were followed until complete recovery of parkinsonian symptoms or at least for 6 months after discontinuation of the offending drug and then diagnosed as DIP or parkinsonism following neuroleptic exposure (PFNE). Transcranial sonography (TCS) findings were compared with the clinical diagnosis.

Results

Sixty patients comprised the group for the final analysis. Sixteen patients were classified as PFNE and 44 as DIP. The area of SN echogenicity was significantly increased in the PFNE group (0.23 cm²; standard deviation [SD]: 0.04), compared to the DIP group (0.14 cm²; SD, 0.05; one-way analysis of variance; P < 0.001). Normal SN was significantly associated with complete recovery after withdrawal of the parkinsonism-inducing drug (P < 0.0005). Accuracy of SN+ to distinguish PFNE from DIP was: sensitivity 81.2%; specificity 84.1%; positive predictive value 47.4%; and negative predictive value 96.2%.

Conclusions

We believe that SN+ assessed with TCS is a valid prognostic marker in the setting of suspected DIP. It is a nonexpensive, feasible technique that can be implemented for proper counseling and guidance of treatment decisions.

The role of neuroimaging in the diagnosis of the atypical parkinsonian syndromes in clinical practice

Atypical parkinsonian disorders (APD) are a heterogenous group of neurodegenerative diseases such as: progressive supranuclear palsy (PSP), multiple system atrophy (MSA), cortico-basal degeneration (CBD) and dementia with Lewy bodies (DLB). In all of them core symptoms of parkinsonian syndrome are accompanied by many additional clinical features not typical for idiopathic Parkinson's disease (PD) like rapid progression, gaze palsy, apraxia, ataxia, early cognitive decline, dysautonomia and usually poor response to levodopa therapy. In the absence of reliably validated biomarkers the diagnosis is still challenging and mainly based on clinical criteria. However, robust data emerging from routine magnetic resonance imaging (MRI) as well as from many advanced MRI techniques such as: diffusion weighted imaging (DWI) and diffusion tensor imaging (DTI), magnetic resonance spectroscopy (MRS), voxel-based morphometry (VBM), susceptibility-weighted imaging (SWI) may help in differential diagnosis. The main aim of this review is to summarize briefly the most important and acknowledged radiological findings of conventional MRI due to its availability in standard clinical settings. Nevertheless, we present shortly other methods of structural (like TCS - transcranial sonography) and functional imaging (like SPECT - single photon emission computed tomography or PET - positron emission tomography) as well as some selected advanced MRI techniques and their potential future applications in supportive role in distinguishing APD.

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.

Basal ganglia echogenicity in tauopathies

Accumulating data confirm the usefulness of transcranial sonography (TCS) in the diagnosis of Parkinson’s disease. The relevance of basal ganglia abnormalities depicted by TCS in atypical parkinsonian syndromes still needs further assessment. In the present study, 20 patients with progressive supranuclear palsy (PSP) and 13 patients with corticobasal syndrome (CBS) were studied with the use of transcranial sonography. Echogenicity of the substantia nigra (SN) and lenticular nucleus (LN) were assessed. 0/20 patients with PSP and 8/12 (66.6 %) patients with CBS were characterized with SN hyperechogenicity. LN hyperechogenicity was observed in 9/20 patients diagnosed with PSP and 0/11 of CBS patients. The combination of SN isoechogenicity and LN hyperechogenicity reached 100 % sensitivity and positive predictive value for the diagnosis of PSP. The results of this study point out that CBS has to be taken into consideration when SN hyperechogenicity is depicted in a patient with parkinsonian syndrome. Normal echogenicity of the SN coexisting with LN hyperechogenicity practically excludes CBS.

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

BACKGROUND AND PURPOSE

Brain imaging with positron emission tomography using [(18) F]fluorodeoxyglucose (FDG-PET) and transcranial B-mode sonography (TCS) improves the differential diagnosis of parkinsonism. The diagnostic merits of these approaches in identifying and differentiating atypical parkinsonian syndromes (APS) are compared.

METHODS

Data were included from 36 patients with clinically suspected APS who underwent PET and TCS. FDG-PET scans were analyzed by visual assessment (including voxel-based statistical maps) of a priori defined disease-specific metabolic patterns. Sonographers achieved diagnoses according to pre-defined criteria for echogenicities of the substantia nigra and lenticular nucleus, and third ventricle diameter. Patients with APS were identified and allocated to the subgroups multiple system atrophy (MSA), progressive supranuclear palsy (PSP) or corticobasal degeneration (CBD).

RESULTS

After a median follow-up period of 9 months, the final clinical diagnoses (reference standard) were Parkinson's disease, n = 15; MSA, n = 9; PSP, n = 7; and CBD, n = 5 (n = 21 APS in total). Six patients (4 APS) showed an insufficient bone window for TCS. In the remaining 30 patients, sensitivity/specificity for diagnosing APS were 82%/100% and 82%/85% for FDG-PET and TCS, respectively. Diagnostic accuracies did not differ between FDG-PET (90%) and TCS (83%; P = 0.69). Likewise, overall accuracy of subgroup classification (non-APS, MSA, PSP and CBD) did not differ between modalities (FDG-PET 87% and TCS 83%; P = 1.00).

CONCLUSIONS

FDG-PET and TCS show comparable accuracies for differential diagnosis of neurodegenerative parkinsonism. This preliminary study supports the use of TCS and warrants further prospective validation.

Transcranial sonography in obsessive-compulsive disorder

There is convergent evidence that basal ganglia structures are involved in the pathogenesis of obsessive-compulsive disorder (OCD). It has been also assumed that OCD is caused by a central serotonergic dysfunction. Transcranial sonography (TCS) has become a reliable, sensitive and non-invasive diagnostic tool concerning the evaluation of extrapyramidal movement disorders. This study used TCS to examine the alterations in different parenchymal regions, especially concerning serotonergic brainstem raphe nuclei as well as basal ganglia in OCD. Thirty-one OCD patients were compared with 31 matched healthy controls. Echogenecities were investigated according to the examination protocol for extrapyramidal disorders using a Siemens Sonoline(®) Elegra system. Obsessive-compulsive disorder patients showed reduced echogenity of the serotonergic brainstem raphe nuclei (32.3%) compared with healthy controls (16.1%). In nine OCD-patients (31%), but only in 2 control subjects (6.2%), a hyperechogenicity of the caudate nucleus was found. Patients with OCD significantly more often reveal a hypoechogenic brainstem raphe possibly reflecting altered serotonergic neurons there and a hyperechogenicity of caudate nucleus indicating structural or molecular cell changes. Further research is warranted to examine, whether TCS is useful in order to classify OCD and its subtypes.

How to measure substantia nigra hyperechogenicity in Parkinson disease: detailed guide with video

The detection of an enlarged echogenic size ("hyperechogenicity") of the substantia nigra on transcranial sonography is increasingly used for the early and differential diagnosis of Parkinson disease. However, the diagnostic value of substantia nigra sonography depends on the quality of its execution. This article with an accompanying video presents a step-by-step description and demonstration of ultrasound system settings, typical errors in assessment of the substantia nigra, planimetric measurement of substantia nigra echogenicity according to current guidelines, and its diagnostic implications in 2 exemplary patients with parkinsonism. Published cutoff values for grading substantia nigra hyperechogenicity with different ultrasound systems and novel technologies are reviewed.

The study of deep brain structures by transcranial duplex sonography and imaging resonance correlation

Transcranial duplex sonography (TCS) currently provides us with images of deep brain structures with sufficient resolution. We chose 2 sonographic quantitative parameters: the diameter of the third ventricle and a measurement not used by TCS to date, the midbrain area. Their reliability and reproducibility were assessed using magnetic resonance imaging (MRI) as the reference. A total of 99 patients free from neurodegenerative disorders were examined using TCS, and both parameters were measured by 2 independent explorers. Measurements of third-ventricle diameter by TCS showed very good correlation (r = 0.80) and agreement (ICC = 0.89) with measurements obtained by MRI. Measurements of the midbrain area by TCS also provided acceptable values with moderate correlation (r = 0.36) and agreement (ICC = 0.53). Interexplorer correlation values were good (ICC = 0.98 and 0.79 for the third ventricle and midbrain areas, respectively). Further studies will be required to determine the potential diagnostic usefulness of these parameters.

Specificity and sensitivity of transcranial sonography of the substantia nigra in the diagnosis of Parkinson's disease: prospective cohort study in 196 patients

OBJECTIVE

Numerous ultrasound studies have suggested that a typical enlarged area of echogenicity in the substantia nigra (SN+) can help diagnose idiopathic Parkinson's disease (IPD). Almost all these studies were retrospective and involved patients with well-established diagnoses and long-disease duration. In this study the diagnostic accuracy of transcranial sonography (TCS) of the substantia nigra in the patient with an undiagnosed parkinsonian syndrome of recent onset has been evaluated.

DESIGN

Prospective cohort study for diagnostic accuracy.

SETTING

Neurology outpatient clinics of two teaching hospitals in the Netherlands.

PATIENTS

196 consecutive patients, who were referred to two neurology outpatient clinics for analysis of clinically unclear parkinsonism. Within 2 weeks of inclusion all patients also underwent a TCS and a (123)I-ioflupane Single Photon Emission CT (FP-CIT SPECT) scan of the brain (n=176).

OUTCOME MEASURES

After 2 years, patients were re-examined by two movement disorder specialist neurologists for a final clinical diagnosis, that served as a surrogate gold standard for our study.

RESULTS

Temporal acoustic windows were insufficient in 45 of 241 patients (18.67%). The final clinical diagnosis was IPD in 102 (52.0%) patients. Twenty-four (12.3%) patients were diagnosed with atypical parkinsonisms (APS) of which 8 (4.0%) multisystem atrophy (MSA), 6 (3.1%) progressive supranuclear palsy (PSP), 6 (3.1%) Lewy body dementia and 4 (2%) corticobasal degeneration. Twenty-one (10.7%) patients had a diagnosis of vascular parkinsonism, 20 (10.2%) essential tremor, 7 (3.6%) drug-induced parkinsonism and 22 (11.2%) patients had no parkinsonism but an alternative diagnosis. The sensitivity of a SN+ for the diagnosis IPD was 0.40 (CI 0.30 to 0.50) and the specificity 0.61 (CI 0.52 to 0.70). Hereby the positive predictive value (PPV) was 0.53 and the negative predictive value (NPV) 0.48. The sensitivity and specificity of FP-CIT SPECT scans for diagnosing IPD was 0.88 (CI 0.1 to 0.95) and 0.68 (CI 0.58 to 0.76) with a PPV of 0.75 and an NPV of 0.84.

CONCLUSIONS

The diagnostic accuracy of TCS in early stage Parkinson's disease is not sufficient for routine clinical use. CLINICALTRIALS.GOV IDENTIFIER: NCT0036819.

Sonographic abnormality of the substantia nigra in melanoma patients

BACKGROUND

Evidence derived from large epidemiological studies suggests an association between Parkinson's disease (PD) and malignant melanoma. Transcranial sonography of the midbrain reveals an extended echogenic substantia nigra (SN) area in a high proportion of patients with PD. This characteristic, in the context of PD, may signal degeneration of dopaminergic nigrostriatal projection neurons. Demonstration of an increased prevalence of abnormal echogenic SN in melanoma patients could add weight to the hypothesis of an underlying common pathogenic pathway of both diseases.

METHODS

This was a cross-sectional observational study. Transcranial sonography of the SN region was performed on 31 patients suffering from malignant melanoma and 29 healthy participants. In addition, patients and controls were screened for motor and non-motor symptoms of PD.

RESULTS

The echogenic SN area was abnormally extended in 42% of melanoma patients versus 7% of control subjects (χ(2) = 9.811, P = .002). Mean echogenic SN area (SN[R, L]) was significantly larger in melanoma patients than in controls (patients, 0.21 ± 0.07 cm(2); controls, 0.15 ± 0.04 cm(2) [mean ± SD]; unpaired t test, P < .001).

CONCLUSIONS

These findings provide additional evidence in favor of a common pathogenic pathway of PD and malignant melanoma and raise the possibility that their association is closer than previously assumed.

Parkinson's disease-like midbrain hyperechogenicity is frequent in amyotrophic lateral sclerosis

Clinical and neuroimaging data suggest impairment of the nigrostriatal system in amyotrophic lateral sclerosis (ALS). We thus hypothesized whether Parkinson's disease (PD)-like midbrain sonography findings are also present in ALS. Eighty-six patients with the diagnosis of possible or definite ALS according to revised El Escorial criteria were examined by transcranial B-mode sonography compared to 76 age- and gender-matched controls and 33 PD patients. Hyperechogenic areas of the midbrain representing the substantia nigra were measured planimetrically using standard protocols. In subjects with sufficient temporal acoustic bone windows, mean midbrain hyperechogenic areas were significantly higher in ALS (0.251 ± 0.104 cm(2)) and PD patients (0.286 ± 0.078 cm(2)) compared to controls (0.091 ± 0.054 cm(2)) with no significant difference between ALS and PD patients (one-way ANOVA: F value = 94.3; P < 0.0001). Sixty-seven percent (95 % CI 57-78 %) of ALS patients and 84 % (95 % CI 71-97 %) of PD patients displayed abnormal midbrain hyperechogenic areas (P = 0.383 for group comparison, χ(2) test). No correlations of hyperechogenic area sizes in ALS patients were found in regard to age, gender, ALS subtype (bulbar versus spinal form) or ALS-FRS-R score. In summary, we observed hyperechogenicity of the substantia nigra in patients with sporadic ALS with a frequency similar to that in PD and higher than in all other movement disorders. These findings are important for the diagnosis and differential diagnosis of PD and ALS alike.

Evaluation of basal ganglia, brainstem raphe and ventricles in bipolar disorder by transcranial sonography

Transcranial brain sonography (TCS) has become a reliable and sensitive diagnostic tool in the evaluation of extrapyramidal movement disorders. Alterations of brainstem raphe (BR) have been depicted by TCS in major depression but not in bipolar disorder. The aim of our study was to evaluate BR echogenicity depending on the different conditions of bipolar patients. Echogenicities of dopaminergic basal ganglia structures were assessed for the first time in bipolar disorder. Thirty-six patients with bipolar I disorder (14 depressed, 8 manic, 14 euthymic) were compared to 35 healthy controls. Echogenicities were investigated according to the examination protocol for extrapyramidal disorders using a Siemens Sonoline® Elegra system. The sonography examiner was blinded for clinical rating scores. Six patients (16.7%) showed hyperechogenicity of the substantia nigra. The raphe was hypoechogenic in 13 (36.1%) of the patients. No significant differences were seen between the subgroups. Compared to the control group, frequency of altered echogenicities did not reach statistical significance. The width of third ventricle was significantly larger in the patient group (3.8±-2.1 mm vs. 2.7±1.2 mm). Depressed bipolar patients with reduced BR echogenicity showed significantly higher scores on the Hamilton Depression Rating Scale as well as the Montgomery-Åsberg Depression Rating Scale. In contrast to unipolar depression, sonographic findings of bipolar patients may generally indicate structural integrity of mesencephalic raphe structures. If bipolar disorder coexists with hypoechogenic raphe structure, depressive symptoms are more severe.

Mesencephalic midline change on transcranial sonography in early Parkinson's disease patients with depression

Recently, several studies using transcranial sonography (TCS) have resulted in the alteration of the mesencephalic midline in patients with depression. We aimed to investigate and compare sonographic abnormalities in the brainstem raphe (BR) in patients with Parkinson's disease (PD) and controls, according to presence of depression. Study participants totaled 61 patients with PD (29 PD without depression, 32 PD with depression) and 41 controls. Results indicated that decreased BR echogenicity was much higher in PD patients with depression (PD+D) than in those without depression (PD-D). Of the 61 PD patients, 32 (52.4%) had depression as diagnosed by psychiatric assessment, and 13 (17.6%) were excluded, due to insufficient temporal windows. Based on these results, the use of TCS with respect to the mesencephalic midline may be useful in detecting depression, a risk factor for the development of PD.

Development of Parkinson's disease biomarkers

Parkinson's disease (PD) is the most common neurodegenerative movement disorder, affecting over 6 million people worldwide. It is anticipated that the number of affected individuals may increase significantly in the most populous nations by 2030. During the past 20 years, much progress has been made in identifying and assessing various potential clinical, biochemical, imaging and genetic biomarkers for PD. Despite the wealth of information, development of a validated biomarker for PD is still ongoing. It is hoped that reliable and well-validated biomarkers will provide critical clues to assist in the diagnosis and management of Parkinson's disease patients in the near future.

Depression in patients with Huntington disease correlates with alterations of the brain stem raphe depicted by transcranial sonography

BACKGROUND

Transcranial sonography (TCS) has become a new diagnostic tool in the evaluation of extrapyramidal disorders. Studies of TCS report alterations of the mesencephalic raphe in patients with depression. The aim of this study was to evaluate TCS findings in patients with Huntington disease in correlation with their neurologic and psychiatric status.

METHODS

We recruited patients with genetically confirmed Huntington disease. The neurological and psychiatric status of participants was assessed by independent physicians. Echogenicities were investigated according to examination protocol for extrapyramidal disorders using a Siemens Sonoline Elegra system. The sonography examiner was blinded for clinical data.

RESULTS

We included 39 patients in our study; 21 patients (53.8%) showed symptoms of depression at the time of evaluation and, of those, 15 (71.4%) had hypoechogenic raphe structures. Thirty patients (76.9%) had a history of depressive episodes, 19 (63.3%) of them with hypoechogenic raphe structures. All 9 patients without a history of depressive episodes showed normal echogenicity of raphe structures (sensitivity 63.3%, specificity 100%). Twelve (70.6%) of the 17 patients with Huntington disease who showed psychiatric disturbances prior to the occurrence of motor symptoms exhibited pathological raphe echogenicity (sensitivity 70.6%, specificity 68.2%).

LIMITATIONS

Most of the patients were taking antichoreatic medication, which particularly influences neurologic status. Thus, a meaningful interpretation of the correlation between TCS findings and neurologic features was limited.

CONCLUSION

As a novel finding, a relation between mesencephalic raphe echogenicity and depressive state could be identified in patients with Huntington disease. An alteration of the serotonergic brain stem raphe might be involved in the pathogenesis of depression in these patients.

Transcranial sonography for the discrimination of idiopathic Parkinson's disease from the atypical parkinsonian syndromes

We reviewed eight studies on transcranial sonography (TCS) as a tool for differentiating idiopathic Parkinson's disease (IPD) from atypical parkinsonian syndromes (APS) and included some first data on TCS findings in the subforms of PSP. Changes of specific structures on TCS like the substantia nigra (SN), lenticular nucleus (LN), and the third ventricle are discussed as well as how they can contribute to differentiate between IPD, multiple system atrophy (MSA), progressive supranuclear palsy (PSP), Lewy body disease (LBD), and corticobasal degeneration (CBD). We finish with an algorithm that may be used to employ TCS as a diagnostic instrument delineating IPD from the APS and discerning among the APS themselves. As TCS is at present the most promising tool for this particular diagnostic problem, this algorithm might be a suitable hypothesis to study in future research.

Clinical neuroimaging and electrophysiological assessment of three DYT6 dystonia families

The purpose of the study was to delineate clinical and electrophysiological characteristics as well as laryngoscopical and transcranial ultrasound (TCS) findings in THAP1 mutation carriers (MutC). According to recent genetic studies, DYT6 (THAP1) gene mutations are an important cause of primary early-onset dystonia. In contrast to DYT1 mutations, THAP1 mutations are associated with primary early-onset segmental or generalised dystonia frequently involving the craniocervical region and the larynx. Blood samples from twelve individuals of three German families with DYT6 positive index cases were obtained to test for THAP1 mutations. Eight THAP1 MutC were identified. Of these, six (three symptomatic and three asymptomatic) THAP1 MutC could be clinically evaluated. Laryngoscopy was performed to evaluate laryngeal dysfunction in patients. Brainstem echogenicity was investigated in all MutC using TCS. Two of the patients had undergone bilateral pallidal DBS. In all three symptomatic MutC, early-onset laryngeal dystonia was a prominent feature. Laryngeal assessment demonstrated adductor-type dystonia in all of them. On clinical examination, the three asymptomatic MutC also showed subtle signs of focal or segmental dystonia. TCS revealed increased substantia nigra (SN) hyperechogenicity in all MutC. Intraoperative microelectrode recordings under general anesthesia in two of the patients showed no difference between THAP1 and previously operated DYT1 MutC. The presence of spasmodic dysphonia in patients with young-onset segmental or generalised dystonia is a hallmark of DYT6 dystonia. SN hyperechogenicity on TCS may represent an endophenotype in these patients. Pallidal DBS in two patients was unsatisfactory.

Essential tremor and Parkinson's disease: lack of a link

BACKGROUND

Essential tremor (ET) is a very common disorder and proving that there is a relationship to another common movement disorder, Parkinson's disease (PD), has been debated for years.

METHODS

Review of the literature for links between ET and PD primarily focused on neuropathology as well as neurochemistry, epidemiology, genetics, olfactory function, and neuroimaging.

RESULTS

While there may be some evidence to suggest an increase in occurrence of PD in people who were previously diagnosed with ET, neuropathologic studies of ET with similarly assessed control subjects do not find an increase in Lewy bodies in the ET group. Studies of incidental Lewy body disease do not find an increase in ET or action tremor compared to controls. ET subjects as a group do not have neurochemical changes that are found in PD, do not respond to medications used to treat PD, are not hyposmic as is found in PD, and neuroimaging studies do not find changes of PD when groups are compared.

CONCLUSION

The overwhelming amount of evidence suggests that any link between ET and PD is coincidental and not biological. Prospective, longitudinal cohort studies with standardized clinical and biomarker assessments followed by neuropathologic confirmation are needed.

Substantia nigra hyperechogenicity is a risk marker of Parkinson's disease: no

During the past two decades, transcranial sonography (TCS) has developed to an increasingly used brain imaging method that visualizes characteristic patterns of basal ganglia alterations in distinct movement disorders. Since the discovery of a characteristic abnormal hyperechogenic appearance of substantia nigra (SN) on TCS in Parkinson's disease (PD), which is stable during the course of the disease and probably present already in preclinical disease stages, the results of several studies have promoted the idea that this TCS finding in healthy subjects might be a risk marker of PD. The present view summarizes current scientific evidence favouring the idea that the TCS finding of SN hyperechogenicity alone may not be a (strong) risk marker of PD. Especially, it is discussed how reliable this TCS finding is, whether this TCS finding can be regarded as a progression marker or a risk marker of PD, how strongly it may indicate a risk of PD, what else if not an increased risk of PD could be indicated, and which role TCS of SN may finally play in the detection of subjects at risk of PD.