Quantifying Lower Limb Muscle Stiffness as Ambulation Function Declines in Duchenne Muscular Dystrophy with Acoustic Radiation Force Impulse Shear Wave Elastography

Ultrasound scatteromics: A multimodal QUS-based solution for detecting ambulatory function deterioration in Duchenne muscular dystrophy

Quantitative ultrasound (QUS) envelope statistics imaging has been investigated as a non-invasive method for evaluating Duchenne muscular dystrophy (DMD). This study introduces an ultrasound scatteromics approach to differentiate between early and late ambulatory stages of DMD. A total of 47 DMD subjects were divided into early (n = 23) and late (n = 24) ambulatory stages. Ultrasound images of the gastrocnemius muscle were acquired and processed to generate multimodal QUS envelope statistics images based on the Nakagami distribution parameter m, homodyned K-distribution parameters α and k, and information entropy H. A simplified feature set based on first-order statistical features of each QUS envelope statistics image was then used for classification with support vector machine (SVM), random forest (RF), and linear discriminant analysis (LDA). A total of 30 iterations of five-fold cross-validation, along with the area under the receiver operating characteristic curve (AUROC), were used for model evaluation. Individual QUS envelope statistics parameters produced average AUROC values below 0.7. Scatteromics achieved average AUROC values of 0.97, 0.98, and 0.83 for SVM, RF, and LDA models, respectively. The simplified scatteromics models, using m, α, k, and H as input to SVM, RF, and LDA, yielded average AUROC values of 0.98, 0.98, and 0.88, respectively. The scatteromics approach outperformed individual QUS envelope statistics imaging methods in monitoring ambulatory function deterioration in DMD in clinical settings (p < 0.05 for AUROC comparisons, DeLong test).

Radiomics with Ultrasound Radiofrequency Data for Improving Evaluation of Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is a rare and severe genetic neuromuscular disease, characterized by rapid progression and high mortality, highlighting the need for accurate ambulatory function assessment tools. Ultrasound imaging methods have been widely used for quantitative analysis. Radiomics, which converts medical images into data, combined with machine learning (ML), offers a promising solution. This study is aimed at utilizing radiomics to analyze different stages of data generated during B-mode image processing to evaluate the ambulatory function of DMD patients. The study included 85 participants, categorized into ambulatory and non-ambulatory groups based on their functional status. Ultrasound scans were utilized to capture backscattered radiofrequency data, which were then processed to generate envelope, normalized, and B-mode images. Radiomics analysis involved the manual segmentation of grayscale images and automatic feature extraction using specialized software, followed by feature selection using the maximal relevance and minimal redundancy method. The selected features were input into five ML algorithms, with model evaluation conducted via area under the receiver operating characteristic curve (AUROC). To ensure robustness, both leave-one-out cross-validation and repeated data splitting methods were employed. Additionally, multiple ML models were constructed and tested to assess their performance. The intensity values across all image types increased as walking ability declined, with significant differences observed between the ambulatory and non-ambulatory groups (p < 0.001). These groups exhibited similar diagnostic performance levels, with AUROC values below 0.8. However, radiofrequency (RF) images outperformed other types when radiomics was applied, notably achieving an AUROC value of 0.906. Additionally, combining multiple ML algorithms yielded a higher AUROC value of 0.912 using RF images as input. Radiomics analysis of RF data surpasses conventional B-mode imaging and other ultrasound-derived images in evaluating ambulatory function in DMD. Moreover, integrating multiple machine learning models further enhances classification performance. The proposed method in this study offers a promising framework for improving the accuracy and reliability of clinical follow-up evaluations, supporting more effective management of DMD. The code is available at https://github.com/Goldenyan/radiomicsUS .

Assessment of Muscular Stiffness in Children with Duchenne Muscular Dystrophy using Real-Time Elastography

BACKGROUND

Imaging modalities, such as ultrasonography (USG), can be used to evaluate and monitor the musculoskeletal system during the clinical progression of Duchenne muscular dystrophy (DMD).

AIM

This study aimed to measure passive muscle stiffness in children with Duchenne muscular dystrophy and to compare these measurements with those of healthy children.

METHODS

Patients with DMD were evaluated clinically (age, clinical functional score, timed Gover score), serum creatine kinase level, B-mode ultrasonography, and real-time tissue elastography imaging.

RESULTS

A total of 64 boys were included in this study. The medial and lateral gastrocnemius muscle strain ratio in patients with DMD was significantly bigger than that in the control group (medial; 1.66 ± 1.23 vs 0.81 ± 0.16, P < 0.001, lateral; 1.49 ± 0.52 vs 0.85 ± 0.16, P < 0.001).

CONCLUSION

The strain ratios of the medial and lateral gastrocnemius muscles were greater in patients with Duchenne muscular dystrophy than in the controls, indicating that ultrasound elastography may be beneficial for diagnosis and follow-up.

Ultrasound attenuation imaging as a strategy for evaluation of early and late ambulatory functions in Duchenne muscular dystrophy

BACKGROUND

Duchenne muscular dystrophy (DMD) is a genetic neuromuscular disorder that leads to mobility loss and life-threatening cardiac or respiratory complications. Quantitative ultrasound (QUS) envelope statistics imaging, which characterizes fat infiltration and fibrosis in muscles, has been extensively used for DMD evaluations.

PURPOSE

Notably, changes in muscle microstructures also result in acoustic attenuation, potentially serving as another crucial imaging biomarker for DMD. Expanding upon the reference frequency method (RFM), this study contributes to the field by introducing the robust RFM (RRFM) as a novel approach for ultrasound attenuation imaging in DMD.

METHODS

The RRFM algorithm was developed using an iterative reweighted least squares technique. We conducted standard phantom measurements with a clinical ultrasound system equipped with a linear array transducer to assess the improvement in attenuation estimation bias by RRFM. Additionally, 161 DMD patients, included in both a validation dataset (n = 130) and a testing dataset (n = 31), underwent ultrasound scanning of the gastrocnemius for RRFM-based attenuation imaging. The diagnostic performances for ambulatory functions and discrimination between early and late ambulatory stages were evaluated and compared with those of QUS envelope statistics imaging (involving Nakagami distribution, homodyned K distribution, and entropy values) using the area under the receiver operating characteristic curve (AUROC).

RESULTS

The results indicated that the RRFM method more closely matched the actual attenuation properties of the phantom, reducing measurement bias by 50% compared to conventional RFM. The AUROCs for RRFM-based attenuation imaging, used to discriminate between early and late ambulatory stages, were 0.88 and 0.92 for the validation and testing datasets, respectively. These performances significantly surpassed those of QUS envelope statistics imaging (p < 0.05).

CONCLUSIONS

Ultrasound attenuation imaging employing RRFM may serve as a sensitive tool for evaluating the progression of ambulatory function deterioration, offering substantial potential for the health management and follow-up care of DMD patients.

Muscle ultrasound in myopathies

PURPOSE OF REVIEW

This review highlights recent developments in the field of muscle ultrasound (MUS) for the diagnosis and follow up of muscle disorders.

RECENT FINDINGS

The diagnostic screening capacity of quantitative grayscale analysis is still sufficient to assess children suspected of a neuromuscular disorder. A combination of visual and quantitative assessment is advised for optimal interpretation. MUS was more sensitive but less specific than MRI for detecting pathology in limb girdle dystrophies and inflammatory myopathies. New techniques such as shearwave elastography and artificial intelligence algorithms for automated image segmentation show promise but need further development for use in everyday practice.Muscle ultrasound has high correlations with clinical measures of function in skeletal and respiratory muscles and the orofacial region, in most of the myopathies and dystrophies studied. Over time, imaging changes precede changes in clinical status, making them attractive for biomarker use in trials. In Duchenne muscular dystrophy MUS was also responsive to the effects of steroid treatment.

SUMMARY

Muscle ultrasound is a sensitive technique to diagnose and follow up of skeletal, facial and respiratory muscles in neuromuscular disorders. Its role is both complementary to and partially overlapping with that of MRI.

Changes in mechanical properties at the muscle level could be detected by Nakagami imaging during in-vivo fixed-end contractions

In this study, we investigated the capability of the Nakagami transformation to detect changes in vastus lateralis muscle-tendon stiffness (k) during dynamic (and intense) contractions. k was evaluated in eleven healthy males using the gold-standard method (a combination of ultrasound and dynamometric measurements) during maximal and sub-maximal voluntary fixed-end contractions of the knee extensors (20, 40, 60, 80, and 100% of maximum voluntary force), while Nakagami parameters were analysed using the Nakagami transformation during the same contractions. Muscle-belly behaviour was investigated by means of B-mode ultrasound analysis, while Nakagami parameters were obtained in post-processing using radiofrequency data. k was calculated as the slope of the force-muscle-belly elongation relationship. Three contractions at each intensity were performed to calculate the intra-trial reliability and the coefficient of variation (CV) of the Nakagami parameters. At all contraction intensities, high values of intra-trial reliability (range: 0.92-0.96) and low CV (<9%) were observed. k and Nakagami parameters increased as a function of contraction intensity, and significant positive correlations were observed between these variables. These data suggest that changes in mechanical properties (e.g., stiffness) at the muscle level could be investigated by means of Nakagami parameters.

Characterizing Mechanical Changes in the Biceps Brachii Muscle in Mild Facioscapulohumeral Muscular Dystrophy Using Shear Wave Elastography

There is no general consensus on evaluating disease progression in facioscapulohumeral muscular dystrophy (FSHD). Recently, shear wave elastography (SWE) has been proposed as a noninvasive diagnostic tool to assess muscle stiffness in vivo. Therefore, this study aimed to characterize biceps brachii (BB) muscle mechanics in mild-FSHD patients using SWE. Eight patients with mild FSHD, the BB were assessed using SWE, surface electromyography (sEMG), elbow moment measurements during rest, maximum voluntary contraction (MVC), and isometric ramp contractions at 25%, 50%, and 75% MVC across five elbow positions (60°, 90°, 120°, 150°, and 180° flexion). The mean absolute percentage deviation (MAPD) was analyzed as a measure of force control during ramp contractions. The shear elastic modulus of the BB in FSHD patients increased from flexed to extended elbow positions (e.g., p < 0.001 at 25% MVC) and with increasing contraction intensity (e.g., p < 0.001 at 60°). MAPD was highly variable, indicating significant deviation from target values during ramp contractions. SWE in mild FSHD is influenced by contraction level and joint angle, similar to findings of previous studies in healthy subjects. Moreover, altered force control could relate to the subjective muscle weakness reported by patients with dystrophies.

Shear modulus of lower limb muscles in school-aged children with mild hypotonia

The objective of this study is to compare shear modulus of lower limb muscles between children with hypotonia versus typical development (TD) or developmental disorders associated with altered tone. Nineteen children with mild hypotonia (mean age 9.4 ± 2.3y, 13 male) completed assessment of resting shear modulus of rectus femoris, biceps femoris (BF), tibialis anterior (TA) and gastrocnemius lateralis (GL) at short and long lengths using shear wave elastography. Data was compared with previous data from TD children and a scoping review for children with developmental disorders. Data were collated according to Net-Longitudinal Tension Angle (Net-LTA), which is the muscle length expressed as the net proximal and distal joint angles. Effects of Net-LTA (e.g., short, neutral, long) were examined according to sex, age and body mass index (BMI). In children with hypotonia, shear modulus was: higher at longer versus shorter lengths for four muscles (p < 0.01); correlated with age for BF-short (r = 0.60, p < 0.03) and GL-short (r = -0.54, p < 0.03), with BMI for BF-short (r = 0.71, p < 0.05); and not different between sexes (p > 0.05). The shear modulus values for lower limb muscles for children with mild hypotonia were lower than those for children with Duchenne Muscular Dystrophy (TA-neutral), or Cerebral Palsy (GL-neutral), but not TD children (all four muscles). In conclusion, shear modulus increases with longer muscle length (i.e. higher Net-LTA) in mildly hypotonic children. Children with mild hypotonia have lower shear modulus than children with cerebral palsy and Duchenne muscular dystrophy.

Three-dimensional dynamic homogenous modeling: The biomechanical influences of leg tissue stiffness on pressure performance of compression biomedical therapeutic textiles

Patient compliance and therapeutic precision of compression textiles (CTs) are frequently limited by the inaccurate pressure distributions along biological bodies in physical-based compression therapy. Therefore, the biomechanical influences of physiological tissue material characteristics of lower extremities on compression generations of CTs need to be explored systematically to improve pressure management efficacy. In this study, we developed three-dimensional (3D) homogenous finite element (FE) CT-leg systems to qualitatively compare the pressure diversities along lower limbs with different biomaterial tissue properties under each external compression level. Simultaneously, through the obtained leg circumferential displacement, a contact analysis model was applied to quantitatively explore the impact mechanisms of soft leg indentations on the pressure performance of CTs. Based on the experimental validation study, the proposed FE systems could be efficiently utilized for compression performance prediction (error ratio: 7.45%). Through the biomechanical simulation and theoretical calculations, the tissue stiffness characteristics of applied bodies showed significant correlations (p < 0.05) with the body circumferential displacements but no correlations (p > 0.05) with pressure delivery differences of CTs. This study facilitates the pressure fit design principle and leg mannequin material selection guidance for the development and experimental assessment of CTs. It also provides effective simulation methods for pressure prediction and property parametric optimization of compression materials.

Ultrasonographic Assessment of Tissue Stiffness: Recent Progress in Transient Elastography and Shear Wave Elastography in the Liver and Various Organs

Ultrasonography is a noninvasive and widely accessible modality in clinical practice. Recently, ultrasonography has been used to evaluate tissue stiffness; the two representative techniques are transient elastography (FibroScan®) and shear wave elastography. These modalities are now generally used for the assessment of liver fibrosis, the prediction of hepatocarcinogenesis, and determining prognosis. In addition, shear wave elastography is available, not only for the liver but also for various other organs, including the breast and brain. In the breast and brain, shear wave elastography distinguishes malignant lesions from benign ones. Moreover, shear wave elastography can be useful for differentiating between ischemic and hemorrhagic strokes. This review summarizes the recent progress in transient elastography and shear wave elastography of the liver and introduces the advantages of ultrasonographic assessment of tissue stiffness in various organs, including the breast, brain, kidney, heart, thyroid, pancreas, muscle, and bone.

Quantifying lower limb muscle stiffness in typically developing children and adolescents using acoustic radiation force impulse shear wave elastography (ARFI/SWE)-a pilot study

OBJECTIVE

To investigate and quantify age-related changes in lower limb muscle stiffness in typically developing children and adolescents using acoustic radiation force impulse shear wave elastography.

MATERIALS AND METHODS

Shear wave velocities of bilateral rectus femoris, tibialis anterior, and medial gastrocnemius muscles at rest were obtained in typically developing children and adolescents aged 3 to 18 years. The participants were classified into three age groups: Group 1 (children), 3 to 7 years old; Group 2, 8 to 12 (pre-adolescent); and Group 3 (adolescent), 13 to 18. The shear wave velocities of muscle were compared across the three age groups, as well as compared between right- and left-side limbs. The correlation between shear wave velocities and body weight or body mass index was assessed.

RESULTS

Of the 47 participants, 21 were in Group 1, 17 in Group 2, and 9 in Group 3. There were no significant differences among the three age groups' shear wave velocities of bilateral lower limb muscles, and no significant differences between right and left sides. There was no correlation between muscle stiffness and body weight or body mass index.

CONCLUSION

The present pilot study applied acoustic radiation force impulse shear wave elastography to quantify lower limb muscle stiffness in typically developing children and adolescents aged 3 to 18 years, suggesting no marked change in muscle stiffness occurs as they develop.

Quantitative ultrasonography reveals skeletal muscle abnormalities in carriers of DMD pathogenic variants

INTRODUCTION/AIMS

Carriers of DMD pathogenic variants may become symptomatic and develop muscle-related manifestations. Despite that, few studies have attempted to characterize changes in the muscles of these carriers using imaging tools, particularly muscle ultrasound (MUS). The aim of this study was to compare lower limb MUS findings in carriers of DMD pathogenic variants (cDMD) vs healthy controls.

METHODS

Twenty-eight women (15 cDMD and 13 controls) underwent clinical evaluation and MUS. We collected information about muscle-related symptoms and assessed muscle strength. MUS was performed by a single physician (blind to the genetic status of subjects). The following muscles were assessed: rectus femoris, sartorius, tibialis anterior, and medial gastrocnemius. For each site, we computed data on muscle thickness, cross-sectional area, sound attenuation index, and elastography. Between-group comparisons were assessed using nonparametric tests and p-values <.05 were deemed significant.

RESULTS

None of the subjects had objective muscle weakness, but exercise intolerance/fatigue was reported by four cDMDs and only one control. Regarding MUS, sound attenuation indices were significantly higher among carriers for all muscles tested. Longitudinal and axial deep echo intensities for the rectus femoris and tibialis anterior were also higher in the cDMD group compared with controls. No significant between-group differences were noted for elastography values, muscle area, or mean echo intensities.

DISCUSSION

cDMD have skeletal muscle abnormalities that can be detected using quantitative MUS. Further studies are needed to determine whether such abnormalities are related to muscle symptoms in these patients.

Characterization of the in vivo transient responses of the femoral cartilage by means of quantitative ultrasound imaging techniques

BACKGROUND

Quantitative ultrasound (QUS) techniques are new diagnostic tools able to identify changes in structural and material properties of the investigated tissue. For the first time, we evaluated the capability of QUS techniques in determining the in vivo transient changes in knee joint cartilage after a stressful task.

METHODS

An ultrasound scanner collecting B-mode and radiofrequency data simultaneously was used to collect data from the femoral cartilage of the right knee in 15 participants. Cartilage thickness (CTK), ultrasound roughness index (URI), average magnitude ratio (AMR), and Nakagami parameters (NA) were evaluated before, immediately after and every 5 min up to 45 min a stressful task (30 min of running on a treadmill with a negative slope of 5%).

RESULTS

CTK was affected by time (main effect: p < 0.001). Post hoc test showed significant differences with CTK at rest, which were observed up to 30 min after the run. AMR and NA were affected by time (p < 0.01 for both variables), while URI was unaffected by it. For AMR, post hoc test showed significant differences with rest values in the first 35 min of recovery, while NA was increased compared to rest values in all time points.

CONCLUSION

Data suggest that a single running trial is not able to modify the integrity of the femoral cartilage, as reported by URI data. In vivo evaluation of QUS parameters of the femoral cartilage (NA, AMR, and URI) are able to characterize changes in cartilage properties over time.

Novel five nucleotide deletion in dysferlin leads to autosomal recessive limb-girdle muscular dystrophy

Muscular dystrophy (MD) is a genetic disorder that causes progressive muscle weakness and degeneration. Limb-girdle muscular dystrophy (LGMD) is a type of MD that mainly causes muscle atrophy within the shoulder and pelvic girdles. LGMD is classified into autosomal dominant (LGMD-D) and autosomal recessive (LGMD-R) inheritance patterns. Mutations in the Dysferlin gene (DYSF) are common causes of LGMD-R. However, genetic screening of DYSF mutations is rare in Taiwan. Herein, we identified a novel c.2867_2871del ACCAG deletion and a previously reported c.937+1G>A mutation in DYSF from a Taiwanese family with LGMD. The primary symptoms of both siblings were difficulty climbing stairs, walking on the toes, and gradually worsening weakness in the proximal muscles and increased creatine kinase level. Through pedigree analysis and sequencing, two siblings from this family were found to have compound heterozygous DYSF mutations (c. 937+1G>A and c. 2867_2871del ACCAG) within the separated alleles. These mutations induced early stop codons; if translated, truncated DYSF proteins will be expressed. Or, the mRNA products of these two mutations will merit the nonsense-mediated decay, might result in no dysferlin protein expressed. To our knowledge, this is the first report of a novel c.2867_2871del ACCAG deletion in DYSF. Further research is required to examine the effects of the novel DYSF mutation in Taiwanese patients with LGMD.

Acoustic radiation force impulse shear wave elastography quantifies upper limb muscle in patients with Duchenne muscular dystrophy

We investigated whether the upper limb muscle stiffness quantified by the acoustic radiation force impulse shear wave elastography (ARFI/SWE) is a potential biomarker for age-related muscle alteration and functional decline in patients with Duchenne muscular dystrophy (DMD). 37 patients with DMD and 30 typically developing controls (TDC) were grouped by age (3-8, 9-11, and 12-18 years). ARFI/SWE measured the biceps and deltoid muscle's shear wave velocities (SWVs). Performance of Upper Limb Module (PUL 1.2 module) assessed muscle function in DMD patients. Mann Whitney test compared muscle SWVs between DMD and TDC, stratified by three age groups. We used analysis of variance with Bonferroni correction to compare muscle SWVs between DMD and TDC and correlated muscle SWVs with PUL results in the DMD group. Results showed that the SWVs of biceps differentiated DMD patients from TDC across age groups. Younger DMD patients (3-8 years) exhibited higher SWVs (p = 0.013), but older DMD patients (12-18 years) showed lower SWVS (p = 0.028) than same-aged TDC. DMD patients had decreasing biceps SWVs with age (p < 0.001), with no such age effect in TDC. The SWVs of deltoid and biceps positively correlated with PUL scores (r = 0.527 ∼ 0.897, P < 0.05) and negatively correlated with PUL timed measures (r = -0.425 ∼ -0.542, P < 0.05) in DMD patients. Our findings suggest that ARFI/SWE quantifying the SWVs in upper limb muscle could be a potential biomarker to differentiate DMD from TDC across ages and that DMD patients showed age-related muscle alteration and limb functional decline.

In vivo shear wave elasticity imaging for assessment of diaphragm function in muscular dystrophy

Duchenne muscular dystrophy (DMD) causes patients to suffer from ambulatory disability and cardiorespiratory failure, the latter of which leads to premature death. Due to its role in respiration, the diaphragm is an important muscle for study. A common method for evaluating diaphragm function is ex vivo force testing, which only allows for an end point measurement. In contrast, ultrasound shear wave elastography imaging (US-SWEI) can assess diaphragm function over time; however, US-SWEI studies in dystrophic patients to date have focused on the limbs without preclinical studies. In this work, we used US-SWEI to estimate the shear wave speed (SWS) in diaphragm muscles of healthy (WT) mice, mdx mice, and mdx mice haploinsufficient for utrophin (mdx-utr) at 6 and 12 months of age. Diaphragms were then subjected to ex vivo force testing and histological analysis at 12 months of age. Between 6 and 12 months, a 23.8% increase in SWS was observed in WT mice and a 27.8% increase in mdx mice, although no significant difference was found in mdx-utr mice. Specific force generated by mdx-utr diaphragms was lower than that of WT diaphragms following twitch stimulus. A strong correlation between SWS and collagen deposition was observed, as well as between SWS and muscle fiber size. Together, these data demonstrate the ability of US-SWEI to evaluate dystrophic diaphragm functionality over time and predict the biochemical and morphological make-up of the diaphragm. Additionally, our results highlight the advantage of US-SWEI over ex vivo testing by obtaining longitudinal measurements in the same subject. STATEMENT OF SIGNIFICANCE: In DMD patients, muscles experience cycles of regeneration and degeneration that contribute to chronic inflammation and muscle weakness. This pathology only worsens with time and leads to muscle wasting, including in respiratory and cardiac muscles. Because respiratory failure is a major contributor to premature death in DMD patients, the diaphragm muscle is an important muscle to evaluate and treat over time. Currently, diaphragm function is assessed using ex vivo force testing, a technique that only allows measurement at sacrifice. In contrast, ultrasonography, particularly shear wave elasticity imaging (USSWEI), is a promising tool for longitudinal assessment; however, most US-SWEI in DMD patients aimed for limb muscles only with the absence of preclinical studies. This work broadens the applications of US-SWE imaging by demonstrating its ability to track properties and function of dystrophic diaphragm muscles longitudinally in multiple dystrophic mouse models.

Ultrasound of the Biceps Muscle in Idiopathic Parkinson's Disease with Deep Brain Stimulation: Rigidity Can Be Quantified by Shear Wave Elastography

Rigidity in Parkinson’s disease (PD) is assessed by clinical scales, mostly the Unified Parkinson’s Disease Rating Scale of the Movement Disorders Society (MDS-UPDRS). While the MDS-UPDRS-III ranges on an integer from 0 to 4, we investigated whether muscle ultrasound shear wave elastography (SWE) offers a refined assessment. Ten PD patients (five treated with deep brain stimulation (DBS) and levodopa, five with levodopa only) and ten healthy controls were included. Over a period of 80 min, both the SWE value and the item 22b-c of the MDS-UPDRS-III were measured at 5 min intervals. The measurements were performed bilaterally at the biceps brachii muscle (BB) and flexor digitorum profundus muscle in flexion and passive extension. Rigidity was modified and tracked under various therapeutic conditions (with and without medication/DBS). The feasibility of SWE for objective quantification was evaluated by correlation with the UPDRS-III: considering all positions and muscles, there was already a weak correlation (r = 0.01, p < 0.001)—in a targeted analysis, the BB in passive extension showed a markedly higher correlation (r = 0.494, p < 0.001). The application of dopaminergic medication and DBS resulted in statistically significant short-term changes in both clinical rigidity and SWE measurements in the BB (p < 0.001). We conclude that rigidity is reflected in the SWE measurements, indicating that SWE is a potential non-invasive quantitative assessment tool for PD.

Muscle ultrasound in hereditary muscle disease

In this review we summarise the key techniques of muscle ultrasound as they apply to hereditary muscle disease. We review the diagnostic utility of muscle ultrasound including its role in guiding electromyography and muscle biopsy sampling. We summarize the different patterns of sonographic muscle involvement in the major categories of genetic muscle disorders and discuss the limitations of the technique. We hope to encourage others to adopt ultrasound in their care for patients with hereditary muscle diseases.