High-resolution ultrasound changes of the vagus nerve in idiopathic Parkinson's disease (IPD): a possible additional index of disease

The association of vagal atrophy with parameters of autonomic function in multiple system atrophy and progressive supranuclear palsy

Background

Vagal atrophy is a hallmark of Parkinson's disease (PD) and has been found to be associated with autonomic dysfunction, while analyses of the vagus nerve (VN) in atypical Parkinsonian syndromes (APS) have not yet been performed. We here investigate the characteristics of the VN in multiple system atrophy (MSA) and progressive supranuclear palsy (PSP) and, in a second step, its potential as a possible biomarker for orthostatic dysregulation.

Objectives

The aim was to compare the VN pathology in MSA and PSP with healthy individuals and patients with PD as a differentiating factor and to further analyse the correlation of the VN with clinical parameters and cardiovascular response.

Design

We conducted a monocentric, cross-sectional cohort study in 41 APS patients and compared nerve ultrasound (NUS) parameters with 90 PD patients and 39 healthy controls.

Methods

In addition to a detailed neurological history and examination, several clinical severity and motor scores were obtained. Autonomic symptoms were reported in the Scales for Outcomes in Parkinson's Disease - Autonomic questionnaire. Further scores were used to detect other non-motor symptoms, quality of life and cognition. Additionally, we performed a head up tilt test (HUTT) and NUS of the VN. We conducted correlation analyses of the VN cross-sectional area (CSA) with clinical scores and the heart rate and blood pressure variability parameters of the HUTT.

Results

The examination demonstrated a high prevalence of abnormal autonomic response in both MSA (90%) and PSP (80%). The VN CSA correlated with spectral parameters of the HUTT, which are associated with sympatho-vagal imbalance. In addition, the CSA of the VN in patients with PD and PSP were significantly smaller than in healthy controls. In MSA, however, there was no marked vagal atrophy in comparison.

Conclusion

The occurrence of autonomic dysfunction was high in MSA and PSP, which underlines its impact on these syndromes. Our findings indicate a connection between vagal pathology and autonomic dysfunction and might contribute to a better comprehension of APS. To further evaluate the clinical relevance and the VN as a possible marker of autonomic dysfunction in APS, prospective longitudinal observations are necessary.

Vagus Nerve Ultrasonography Helps Distinguish Multiple System Atrophy from Other Parkinsonian Syndromes

Background

Distinguishing multiple system atrophy from other parkinsonian syndromes is challenging.

Objectives

To evaluate vagus nerve ultrasonography for differentiating parkinsonian syndromes.

Methods

A single-center, cross-sectional, observational study assessed 85 consecutive adult patients with de novo parkinsonism between June 2020 and December 2022, using 12 MHz ultrasonography of the vagus nerve cross-sectional area.

Results

Bilateral vagus nerves were smaller in multiple system atrophy than in other parkinsonian syndromes. The area under the receiver operating characteristic curve for differentiating multiple system atrophy was 0.79 on the right side and 0.74 on the left. The cut-off values to diagnose multiple system atrophy were 0.71 and 0.86 mm2 on the right and left sides, respectively, with sensitivities of 82.6% and 87.0%, specificities of 74.2% and 64.5%, positive predictive values of 54% and 47.6%, and negative predictive values of 92.0% and 93.0%.

Conclusions

Vagus nerve ultrasonography may differentiate multiple system atrophy from other parkinsonian syndromes.

Vagus nerve cross-sectional area decreases in Parkinson's disease

INTRODUCTION

Morphological alterations of the vagus nerve (VN) in Parkinson's disease (PD) are discussed controversially. Several studies reported no difference in VN cross-sectional area (CSA) in PD patients in nerve ultrasound, others found a reduced CSA interpreted as atrophy of the VN and involvement of the dorsal nucleus of VN.

METHODS

In a prospective comparative cross-sectional study, CSA of the VN bilaterally and the right ulnar nerve, clinical PD scales, non-motor symptoms and autonomic tests were compared between 49 PD patients and 24 healthy controls. Nerve ultrasound was performed by two independent investigators, patients and controls were compared at Bonferroni corrected p < 0.025 using results of both investigators and averaged results. Blinding included CSA measurements and PD scores, but not PD diagnosis.

RESULTS

Bilateral averaged VN CSA was significantly lower in PD patients than in controls (Right VN PD mean 2.70 mm2 SD 0.69, controls 3.30 mm2 SD 0.49, p < 0.001. Left VN PD mean 2.45 mm2 SD 0.57, controls 2.77 mm2 SD 0.46, p = 0.012). No difference was found in the ulnar nerve. There was a weak negative correlation between the right VN CSA and the Unified Parkinson Disease Rating Scale (-0.08 mm2 per 10 points). The area under the receiver operating characteristic curve for the right VN was 0.78 (p < 0.001).

CONCLUSION

The present results support the hypothesis of atrophy of the VN in PD. Reduction of VN CSA is a weak marker of disease progression. Nerve ultrasound of the VN might represent a supplementary method in diagnosis of PD.

Sonographic vagus nerve atrophy in Parkinson's disease: Myth or fact? A systematic review and meta-analysis of recent evidence answers

BACKGROUND

Parkinson's disease (PD) is a major cause of disability. We aimed to assess the benefit of ultrasonography of the vagus nerve (VN) to compare between PD and healthy controls as well as to deliver reference values of nerve cross sectional area (CSA).

MATERIALS AND METHODS

We performed a systematic search on Medline (PubMed), Scopus, Embase, and Web of Science, up till July 25, 2022. After article selection and screening, we performed a quality assessment using the Newcastle-Ottawa Scale. Furthermore, a statistical analysis and subgroup analysis was performed.

RESULTS

Eleven studies were included with a total of 809 participants (409 PD patients and 400 controls). A statistically significant difference in the CSA of the right and left VN between PD patients and healthy controls was observed, indicating the atrophy of VN in PD patients (p < 0.00001). The subgroup meta-analysis for average measurements of VN CSA showed insignificant heterogeneity for age (I² = 48.67%, p = 0.058), level of measurements (I² = 57.91%, p = 0.05), and disease duration (I² = 27.1%, p = 0.241).

CONCLUSION

Our meta-analysis showed a sonographically detectable degree of neuronal damage in PD, which correlates with VN atrophy with high confidence. Therefore, we believe this is a potential marker for vagus neuronal lesions. Future studies are required to assess the potential clinical correlation.

Evaluating Diagnostic Ultrasound of the Vagus Nerve as a Surrogate Marker for Autonomic Neuropathy in Diabetic Patients

Background and Objectives: Diagnostic ultrasound of the vagus nerve has been used to examine different polyneuropathies, and it has been suggested to be useful as a marker of autonomic dysfunction in diabetic patients. Materials and Methods: We analyzed the cross-sectional area (CSA) of the right vagus nerve of 111 patients with type 2 diabetes in comparison to 104 healthy adults and 41 patients with CIDP (chronic inflammatory demyelinating polyneuropathy). In the diabetes group, sympathetic skin response (SSR) was measured as an indicator for autonomic neuropathy. Carotid intima-media thickness (CIMT) was measured as a surrogate for atherosclerosis. Clinical symptoms of polyneuropathy were assessed using the Neuropathy Symptom Score and the Neuropathy Disability Score. Results: In total, 61.3% of the diabetes patients had clinical signs of polyneuropathy; 23.4% had no SSR at the feet as an indicator of autonomic neuropathy. Mean vagus nerve CSA did not differ in patients with and without diabetic polyneuropathy or in diabetic patients with and without SSR at the feet. No significant correlation was found between vagus nerve CSA and CIMT or SSR parameters in diabetic patients. Mean CSA of the right vagus nerve was slightly larger in diabetic patients (p = 0.028) and in patients with CIDP (p = 0.015) than in healthy controls. Conclusions: Effect sizes and mean differences were rather small so that a reliable diagnosis cannot be performed based on the vagus nerve measurement of a single person alone. Vagus nerve CSA seems not suitable as an indicator of autonomic dysfunction or cardiovascular risk in diabetic patients.

Ultrasound evaluation of vagus nerve cross-sectional area in a community-dwelling elderly Japanese cohort

OBJECTIVES

Although the vagus nerve (VN) is easily observed by ultrasonography, few studies have evaluated the cross-sectional area (CSA) of the VN in healthy older individuals from East Asia. In this study, we aimed to report reference values for the CSA of the VN in community-dwelling elderly Japanese individuals and to identify any associated medical history and/or lifestyle factors.

METHODS

The present study included 336 participants aged ≥ 70 years from a prospective cohort study conducted in Yahaba, Japan from October 2021 to February 2022. The CSA of the VN was measured bilaterally at the level of the thyroid gland by ultrasonography. Simple linear regression analysis and generalized estimating equation were conducted to identify the associations between clinical and background factors and the CSA of the VN.

RESULTS

In our cohort, the median CSA of the VN was 1.3 mm2 (interquartile range [IQR] 1.1-1.6) on the right side and 1.2 mm2 (IQR 1.0-1.4) on the left side. Generalized estimating equation showed that history of head injury (β = 0.19, p < .01), current smoking habit (β = -0.09, p = .03), and BMI (β = 0.02, p < .01) were independently associated with the CSA of the VN.

CONCLUSION

We have reported reference VN CSA values for community-dwelling elderly Japanese individuals. In addition, we showed that the CSA of the VN was positively associated with a history of head injury and BMI and inversely associated with current smoking habit.

Autonomic dysfunction in amyotrophic lateral sclerosis: A neurophysiological and neurosonology study

BACKGROUND AND PURPOSE

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder affecting upper and lower motor neurons. Some ALS patients exhibit concomitant nonmotor signs, and thus ALS is considered a multisystem disorder. The aim of this study is to investigate autonomous nervous system involvement in ALS.

METHODS

We investigated 21 ALS patients and 28 age-matched controls. ALS patients were assessed for disease severity with the Revised-ALS Functional Rating Scale (ALSFSR) and for the presence of autonomic symptoms with the Composite Autonomic Symptom Score scale. Sympathetic nervous system was evaluated by sympathetic skin response (SSR) and parasympathetic nervous system by ultrasonography of vagus nerve (VN) at the level of the thyroid gland.

RESULTS

SSR latencies were shorter and SSR amplitudes were higher in controls compared to ALS patients. The cross-sectional area (CSA) of the VN was significantly smaller in ALS patients (mean CSA right/left: 1.73±0.62 mm² /1.47±0.53 mm² ) compared to controls (mean CSA right/left: 2.91±0.79 mm² /2.30±0.80 mm² ), right: p <. 001, left: p <. 001. There was a significant negative correlation between disease duration and CSA of left-VN (r = -0.493, p = .023). This correlation was attenuated between disease duration and CSA of right-VN (r = -0.419, p = .059). ALSFSR-R was positively correlated to CSA of right-VN (p = .006, r = 0.590). CSA of VN did not correlate with bulbar involvement.

CONCLUSIONS

This study confirms the presence of autonomic dysfunction in ALS patients and provides evidence of VN atrophy that correlates with disease severity and duration and is independent of bulbar involvement. Degeneration of dorsal nucleus neurons of the VN is hypothesized.

Ultrasound imaging of vagus nerves in patients with Parkinson's disease

Parkinson’s disease (PD) is a neurodegenerative multisystem disorder characterized by pathologic α-synuclein aggregation affecting, among other things, vagal fibers. The aim of this study was to investigate the cross-sectional area (CSA) of the vagus nerve (VN) in patients with PD using ultrasound imaging. The study was conducted in 32 patients with PD (15 men and 17 women; mean age 58 ± 10 years) and 32 healthy controls comparable with the main group in terms of sex and age. All study participants underwent ultrasound examination of the VN using a high-resolution transducer. Left VN CSA was significantly smaller in patients with PD than in the control group (1.78 ± 0.52 mm2 vs 2.11 ± 0.41 mm2; р = 0.007). A similar result was obtained for right VN CSA at the trend level. ROC analysis demonstrated that the threshold CSA value of < 2.10 mm2 for the left VN has low diagnostic sensivity (59%) for VN atrophy in patients with PD. Right VN CSA was significantly larger than left VN CSA in both groups (p < 0.001). The analysis of the PD group did not reveal any associations between VN CSA and age, duration and stage of the disease, motor (UPDRS III) and non-motor (NMSQ) scores. Patients with akinetic-rigid form of PD had smaller left VN CSA than patients with the mixed form of the disease (р < 0.05). A moderate inverse correlation was established between left VN CSA and the area of substantia nigra hyperechogenicity on both sides (р < 0.04); for the right VN a similar correlation was established at the trend level. High-resolution ultrasound of patients with PD demonstrated atrophy of the VN and the association of VN CSA with the clinical form of the disease and the ultrasound features of the substantia nigra.

Normal anatomy, variants and factors associated with the cervical vagus nerve topography: a high-resolution ultrasound study

PURPOSE

To describe the cervical vagus nerve (CVN) topography at the thyroid lobe (TL) level using high-resolution ultrasound and to investigate the possible association with anthropometric data, TL size, and thyroid disease.

METHODS

We prospectively examined 550 CVNs in 275 (205 female, 70 male) individuals with normal thyroid (53/275, 19.3%), multinodular disease (167/275, 60.7%), and Hashimoto thyroiditis (55/275, 20%). The CVN location relative to the common carotid artery was recorded as typical (lateral position) and atypical (anterior, medial, and posterior position). The shortest distance between CVN and TL margin, the TL dimensions, and volume were measured.

RESULTS

Normal thyroid subjects had lateral-positioned right CVNs in 100% and lateral/anterior/medial left CVNs in 81.1%, 15.1%, and 3.8%, respectively. CVN types did not differ significantly bilaterally between study groups. Asymmetry in CVN topography in all subjects was found in 22.2%, of which anterior CVN was the most common atypical position (64%), especially on the left side (82%). Significant gender, age, body mass, and BMI differences among CVN types were observed on the left side only. Among CVN types, no difference in TL dimensions, volume, and CVN-TL distance was found in all study groups. A weak negative correlation was recorded between CVN-thyroid distance and TL volume only on the left side (r = - 0.147, p = 0.01).

CONCLUSION

Asymmetry in CVN topography is mainly due to the increased incidence of the anterior location of CVN on the left side. Age and anthropometric parameters are different on the left side possibly due to the increased prevalence of left CVN variants.

Vagus Nerve Cross-Sectional Area in Patients With Parkinson's Disease-An Ultrasound Case-Control Study

Background: Vagal parasympathetic neurons are prone to degeneration in Parkinson's disease (PD). High-resolution ultrasound can precisely estimate the cross-sectional (CSA) area of peripheral nerves. Here, we tested the hypothesis that vagus CSA is reduced in PD. Methods: We included 56 healthy controls (HCs) and 63 patients with PD. Using a high-end ultrasound system equipped with a high-frequency transducer, five images were obtained of each nerve. The hypoechoic neuronal tissue was delineated offline with dedicated software and the CSA extracted. Results: In the initial PD vs. HC comparison, no statistically significant differences were observed in mean left vagus CSA (HC: 1.97 mm2, PD: 1.89 mm2, P = 0.36) nor in mean right vagus CSA (HC: 2.37 mm2, PD: 2.23 mm2, P = 0.17). The right vagus CSA was significantly larger than the left vagus CSA in both groups (P < 0.0001). Females were overrepresented in the HC group and presented with generally smaller vagus CSAs. Consequently, sex-adjusted CSA was significantly smaller for the right vagus nerve of the PD group (P = 0.041), but not for the left. Conclusion: A small but significant reduction in sex-adjusted right vagus CSA was observed in patients with PD. The left vagus CSA was not significantly reduced in patients with PD. Ultrasound may not be a suitable method to detecting vagal axonal loss in individual patients.