Essential tremor vs idiopathic Parkinson disease: Utility of transcranial sonography

Distinguishing essential tremor from Parkinson's disease: clinical and experimental tools

INTRODUCTION

Essential tremor (ET) and Parkinson's disease (PD) are the most common causes of tremor and the most prevalent movement disorders, with overlapping clinical features that can lead to diagnostic challenges, especially in the early stages.

AREAS COVERED

In the present paper, the authors review the clinical and experimental studies and emphasized the major aspects to differentiate between ET and PD, with particular attention to cardinal phenomenological features of these two conditions. Ancillary and experimental techniques, including neurophysiology, neuroimaging, fluid biomarker evaluation, and innovative methods, are also discussed for their role in differential diagnosis between ET and PD. Special attention is given to investigations and tools applicable in the early stages of the diseases, when the differential diagnosis between the two conditions is more challenging. Furthermore, the authors discuss knowledge gaps and unsolved issues in the field.

EXPERT OPINION

Distinguishing ET and PD is crucial for prognostic purposes and appropriate treatment. Additionally, accurate diagnosis is critical for optimizing clinical and experimental research on pathophysiology and innovative therapies. In a few years, integrated technologies could enable accurate, reliable diagnosis from early disease stages or prodromal stages in at-risk populations, but further research combining different techniques is needed.

Value of ultrasound fusion imaging in detecting vascular cerebral white matter pathology

BACKGROUND

Transcranial sonography is beside magnetic resonance imaging (MRI) and computed tomography, a well-established imaging method for evaluation of brain parenchyma and already implicated in various neurological disorders as bed-side investigation possibility in clinical routine. The aim of this study was the qualitative assessment detecting vascular white matter hyperintensities (WMHs), with ultrasound fusion-imaging technique (UFI) and to find the optimal location for their visualization in accordance to the grade of WMHs and to possibly providing a standardized protocol for clinical use.

RESULTS

29 patients with WMHs of variable degree quantified according to Fazekas grading scale (n = 13 I; n = 9 II; n = 7 III) and 11 subjects with normal findings on MRI were identified for further analysis. Ultrasound images were analyzed to a standardized protocol and predefined anatomical landmarks. UFI could visualize the MRI-verified WMHs in 147 of 161 localizations (91%). The overall ultrasound detection rate of WMHs increased with higher degree of WMHs burden (I:85%, II:94%, III:97%). The highest sensitivity was achieved at the contralateral central part (CPc) (97%) of the lateral ventricle. The inter-rater analysis between 2 independent raters, who were blinded to the patient's diagnosis and assessed only the B-mode ultrasound images, indicated an 86% agreement with an overall moderate strength of agreement (κ: 0.489, p < 0.0005) for all localizations. The highest accordance within raters was shown at the CPc; 92% (κ: 0.645, p < 0.0005).

CONCLUSIONS

This explorative study describes prospectively the ultrasound detection of periventricular vascular WMHs based on MRI lesions using UFI. Transcranial ultrasound (TCS) could serve as an additional screening opportunity for the detection of incidental WMLs during routine TCS investigations to initiate early vascular risk factor modification in primary prevention.

Differentiating Parkinson’s Disease from Essential Tremor Using Transcranial Sonography: A Systematic Review and Meta-Analysis

Background:

Essential tremor (ET) and the tremor of Parkinson’s disease (PD) are the most common tremors encountered in clinical practice. Especially in early disease stages, discrimination between the tremors of ET and PD can be challenging.

Objective:

The aim of this study was to evaluate the diagnostic accuracy of transcranial sonography (TCS) of the substantia nigra echogenicity for differential diagnosis of PD versus ET.

Methods:

A systematic PubMed search identified 512 studies. Sensitivity and specificity of substantia nigra hyperechogenicity was estimated. Data synthesis was carried applying a random effects bivariate binomial model. To assess study quality and risk of bias, the QUADAS-2 tool was used.

Results:

Eighteen studies were suitable for analysis including 1,264 PD and 824 ET patients. The meta analysis showed a pooled sensitivity and specificity for TCS in the differential diagnosis of PD versus ET of 84.6% (95% CI, 79.4–88.6%) and 83.9% (95% CI, 78.4–88.2%), respectively. Furthermore, we found nearly similar results in sensitivity and specificity comparing TCS and DaTSCAN in a subgroup-analysis of three studies using both diagnostic tools including 107 patients with PD and 62 patients with ET. The QUADAS-2 toolbox revealed a high risk of bias regarding the methodological quality of patient selection.

Conclusion:

Substantia nigra hyperechogenicity yield high diagnostic accuracy for the discrimination of PD from ET. TCS is a low cost, widely available, non-invasive marker without radiation Therefore, a diagnostic algorithm based on presence or absence of substantia nigra hyperechogenicity is highly warranted.

Visual analysis of nigrosome-1 in the differential diagnosis of Parkinson's disease and essential tremor

Differentiation between Parkinson’s disease, especially in its early stages, and essential tremor, which is a phenotypically similar movement disorder, still remains an unsolved challenge for neurology. The aim of this study was to assess the diagnostic significance of nigrosome imaging (nigrosomes are dopaminergic neuron clusters in the substantia nigra of the midbrain) using 3T high-resolution SW-MRI. The study was conducted in 20 patients with Parkinson’s disease and 10 patients with essential tremor. Visual analysis of the acquired nigrosome-1 images was performed using a 4-point ordinal rating scale. Differences in sex, age and duration of the disease were calculated using the Fisher exact test and the Mann–Whitney U test. The diagnostic value of the method was assessed using Pearson’s chisquared test. Nigrosome-1 was bilaterally or unilaterally absent in 70% of parkinsonian patients. Less specific changes to the substantia nigra (SN) were observed in two more parkinsonian patients (10%), whose nigrosome-1 appeared reduced in size. By contrast, nigrosome-1 was bilaterally intact in all patients (100%) with essential tremor (p < 0.001). Our preliminary findings demonstrate the high potential of noninvasive nigrosome-1 imaging in the differential diagnosis of Parkinson’s disease and essential tremor.