Quantitative ultrasonography of skeletal muscles in children: normal values

The purpose of this study was to establish normal values of muscle thickness, ratio of muscle thickness to subcutaneous fat thickness, and muscle echo intensity in children between 11 weeks and 16 years of age. Transverse scans of four muscles were made by standardized real-time ultrasound examination. The scans were digitized, and mean echo intensity was measured using gray-scale analysis. A multiple regression equation was used to study which independent parameter (age, height, weight, or sex) influenced the variables for each muscle. Muscle thickness depended on the child's weight. The other parameters did not significantly influence muscle thickness after correction for weight. The ratio of muscle thickness to subcutaneous fat thickness depended on age. Echo intensity showed no correlation with either of the variables. As a result, all normal values, including the equation to calculate them, are described. These normal data may help to determine the diagnostic value of muscle ultrasound in children with suspected neuromuscular disease.     

Reliability of sonographic muscle thickness measurements of the thenar and hypothenar muscles

Introduction This study was undertaken to assess the intra‐ and interrater reliability of sonographic thickness measurements of the thenar and hypothenar muscles. Methods: The thickness of the thenar and hypothenar muscles of both hands of 15 volunteers (7 male, 8 female) were evaluated with a 4–13‐MHz linear probe by 2 examiners who were blinded to each other's measurements. Interrater reliability was then evaluated. To assess intrarater reliability, the first examiner also performed a second measurement after an interval of at least 1 day. Results: Mean age of the subjects was 31.1 ± 9.0 years. Test–retest reliability showed excellent intrarater reliability (intraclass correlation coefficient range: 0.889–0.963) and substantial to excellent results for interrater reliability (intraclass correlation coefficient range: 0.692–0.937). Discussion: We found that ultrasound is a reliable method for thickness measurements of the thenar and hypothenar muscles. Muscle Nerve 57 : E14–E17, 2018     

Tonic stretch reflexes in lip, tongue and jaw muscles

Despite considerable speculation it remains unclear as to whether stretch reflexes perform a functional role in speech articulator muscles. Recent research, however, has shown that long loop stretch reflex mechanisms are brought into play during voluntary contraction of limb muscles and a functional role in oscillatory damping has been suggested. It was decided, therefore, to use a method and a technique of analysis similar to that used in limb muscles to search for tonic stretch reflex (TSR) responses in lip, tongue and jaw muscles during sustained voluntary contraction. The term 'action TSR' is used to differentiate stretch reflex responses measured from voluntary activity from those measured at rest. Simultaneous electromyogram (EMG) recordings were taken from the lip, tongue and jaw musculature in normal, stutterer and cerebral spastic subjects. Subjects were instructed to hold the appropriate articulator in a fixed position while the experiment applied an irregular, continuously changing, stretching force. The stretch and EMG signals were analyzed using a cross correlation and spectral analysis technique. This provided a sensitive means of detecting any EMG fluctuations which covaried with applied stretch and might therefore be classified as reflex. No suggestion of such action TSR responses could be found in lip or tongue muscles of any of the subjects tested, including the cerebral spastic subjects with dysarthric speech. It is therefore concluded that action TSR mechanisms are not operative in control of lip and tongue muscles in man. Furthermore, dysarthric speech in cerebral spasticity cannot be attributed to exaggerated tone of lip and tongue muscles resulting from hypersensitivity of TSR mechanisms. In contrast, clear action TSR responses were demonstrable in jaw closing muscles while in jaw opening muscles, small amplitude responses were detected but were not substantial in comparison with background activity. Since the action TSR is present in jaw and limb muscles, but absent in lip and tongue muscles, the suggestion of a functional role of this reflex in damping mechanical oscillations associated with inertial loads is further supported.     

Quantitative muscle ultrasonography in the follow‐up of juvenile dermatomyositis

Introduction: We explored the use of quantitative muscle ultrasonography (QMUS) for follow‐up of juvenile dermatomyositis (JDM). Methods: Seven JDM patients were evaluated at diagnosis and 1, 3, 6, 12, and 24 months using the Childhood Myositis Assessment Scale (CMAS) and QMUS. Muscle thickness (MT) and quantitative muscle echo intensity (EI) were assessed with QMUS in 4 muscles. Results: Six patients experienced a monocyclic course. At diagnosis EI was slightly increased, and MT was relatively normal. After start of treatment MT first decreased and EI increased, with normalization of EI within 6–12 months (n = 4). One patient had higher EIs at diagnosis and slower normalization, indicating fibrosis, despite early normalization of CMAS. One patient experienced a chronic course, with high EIs and atrophy during follow‐up. Conclusions: QMUS can provide additional information for follow‐up of JDM regarding disease severity and residual muscle damage, particularly after normalization of CMAS. Muscle Nerve 52: 540–546, 2015     

Quantitative ultrasonography of facial muscles

Introduction: There is no standardized method for examination of facial muscles with ultrasound. The purpose of this study was to identify those facial muscles accessible for reliable identification and to provide reference data. Methods: In healthy subjects all facial muscles were screened for visibility, separation from adjacent muscles, and reliability of landmarks. Bilateral scans of reliable muscles were performed in 40 adult volunteers. Results: Six facial muscles were clearly demarcated with ultrasound. These were: frontalis, orbicularis oculi, orbicularis oris, depressor anguli oris, depressor labii inferioris, and mentalis muscles. Cross-sectional area and muscle thickness showed gender differences and were independently related to age for some muscles. A significant left–right side difference was only seen for the orbicularis oculi muscle in women. Conclusions: These data demonstrate the usefulness of ultrasonography to assess facial muscles and provide reference values that can be applied in the clinical setting. Muscle Nerve 47: 878–883, 2013     

Ultrasound characterization of medial gastrocnemius tissue composition in children with spastic cerebral palsy

Introduction: In this study we aimed to characterize muscle composition of the medial gastrocnemius in children with spastic cerebral palsy (SCP) using quantitative ultrasound. Methods: Forty children with SCP, aged 4–14 years, participated in this study. Children were grouped according to the gross motor function classification system (GMFCS I–V) and compared with a cohort of age‐ and gender‐matched, typically developing children (TD; n = 12). Ultrasound scans were taken of the medial gastrocnemius. Images were then characterized using grayscale statistics to determine mean echo intensity (EI) and the size and number of spatially connected homogeneous regions (i.e., blobs). Results: Significant differences in skeletal muscle composition were found between children with SCP and their TD peers. Children classified as GMFCS III consistently exhibited the highest EI and blob area. Conclusions: This study demonstrates altered tissue composition in children with SCP visualized using ultrasound. Further work is required to determine the pathophysiology contributing to these alterations in SCP. Muscle Nerve 52:397–403, 2015     

Quantitative muscle ultrasound versus quantitative magnetic resonance imaging in facioscapulohumeral dystrophy

Introduction: Ultrasound and magnetic resonance imaging (MRI) are non‐invasive methods that can be performed repeatedly and without discomfort. In the assessment of neuromuscular disorders it is unknown if they provide complementary information. In this study we tested this for patients with facioscapulohumeral muscular dystrophy (FSHD). Methods: We performed quantitative muscle ultrasound (QMUS) and quantitative MRI (QMRI) of the legs in 5 men with FSHD. Results: The correlation between QMUS‐determined z‐scores and QMRI‐determined muscle fraction and T1 signal intensity (SI) was very high. QMUS had a wider dynamic range than QMRI, whereas QMRI could detect inhomogeneous distribution of pathology over the length of the muscles. Conclusions: Both QMUS and QMRI are well suited for imaging muscular dystrophy. The wider dynamic range of QMUS can be advantageous in the follow‐up of advanced disease stages, whereas QMRI seems preferable in pathologies such as FSHD that affect deep muscle layers and show inhomogeneous abnormality distributions. Muscle Nerve 50: 968–975, 2014     

Strength and fatigue of lumbar extensor muscles in older adults

Introduction: Loss of lumbar extensor muscle strength and fatigue resistance may contribute to functional disability. Methods: Two groups of subjects were recruited: young (n = 26, 20–35 years of age) and old (n = 26, ≥65 years of age) adults. Lumbar extensor muscle strength was measured with a load cell, and electromyographic activities were recorded to study muscle fatigue at 60% of maximum voluntary contraction. Results: We found that the muscle moments generated by the extensor muscles decreased with age (P < 0.05). Aging was associated with a significant increase in the power of the lower frequency band (101–200 Hz) of the electromyographic signals (P < 0.05), but the spectral characteristics did not appear to change with sustained contraction (P > 0.05). Conclusions: The changes in strength and spectral properties of the electromyographic signals of lumbar extensor muscles may be related to age‐related alterations in muscle fiber composition and recruitment. These changes should be considered in clinical functional task evaluation. Muscle Nerve 44: 74–79, 2011     

Reliability of bedside ultrasound of limb and diaphragm muscle thickness in critically ill children

Introduction: We evaluated the reliability of measuring muscle thickness with ultrasound in limbs and diaphragms of critically ill children and determined the sensitivity of these measures to quantitate muscle atrophy over time. Methods: An expert and trained novice sonographers prospectively measured limb and diaphragm muscle thickness in 33 critically ill children. Results: Expert and novice intrarater and interrater reliability were similar. Intraclass correlations (ICC) and coefficients of variation (CoV) were better in limbs (ICC > 0.9; CoV 3.57%–5.40%) than in diaphragm (ICC > 0.8; CoV novice 11.88%, expert, 12.28%). Mean relative difference in all muscles was small (1%-8%). Limits of agreement of the relative difference were smaller in limb (<13%–18%) than in diaphragm (<38%) muscles. Discussion: Muscle thickness is reliably measured with ultrasound by trained examiners in critically ill children. Our approach detects atrophy >13% in limb and >38% in diaphragm muscles. The smaller detectable change in limb muscles is likely due to their greater thickness. Muscle Nerve 59 :88–94, 2019     

Quantitative ultrasound of the calcaneus in children and young adults with severe cerebral palsy

Osteopenia is common in children, adolescents, and young adults with severe cerebral palsy (CP; spastic quadriplegia) living in residential care, and frequently results in atraumatic fractures. On clinical grounds 67 patients (34 males, 33 females) with severe CP (gross motor function classification system [GMFCS] levels IV or V) aged 5 to 25 years (median 20 y) were divided into three groups with increasing likelihood of severe impairment of bone quality: (1) patients without fractures and without anticonvulsant medication (n=13); (2) patients without fractures and with anticonvulsant medication (n=45); (3) patients with fractures and with anticonvulsant medication (n=9). Evaluation included measurements of quantitative ultrasound (QUS) of the calcaneus, multiple serum analyses, and determination of urinary bone-resorption markers. Values of the quantitative ultrasound index (QUI) were significantly different (p=0.001): group 1 (median 56.9; interquartile range 43.8-75.3); group 2 (49.9; 40.0-60.0); group 3 (35.6; 30.5-38.5). when comparing values of laboratory serum and urine in the three groups, we found significant differences in values of serum bone alkaline phosphatase (p=0.001), serum parathyroid hormone (PTH; p=0.002), serum albumin (p=0.020), and urinary deoxypyridinoline/creatinine ratio (p=0.004). In multiple regression analysis, no laboratory variable was found to be an independent predictor of QUI. QUS of the calcaneus may be a useful method to assess bone quality and fracture risk in children and young adults with severe cp living in residential care, independent of information from laboratory data.     

Quantitative ultrasonography of facial muscles in patients with chronic facial palsy

Introduction: In this study we introduce quantitative facial muscle ultrasound as a diagnostic tool for patients with chronic unilateral facial palsy. Methods: Muscle area, thickness, and echo intensity of 6 facial muscles (frontalis, orbicularis oculi, orbicularis oris, depressor anguli oris, depressor labii inferioris, and mentalis) and of 2 chewing muscles (temporalis and masseter, as controls) were measured in 20 patients with chronic facial palsy. Results: Aside from 1, all facial muscles were significantly smaller on the paralyzed side. With exception of frontalis and orbicularis oculi muscles, all other facial muscles showed significantly higher echo intensity on the affected side. Muscle size and echo intensity of the chewing muscles showed no side‐to‐side asymmetry. Conclusions: Quantitative ultrasound of facial muscles helps to better characterize their status in patients with chronic facial palsy in the phase of denervation and during regeneration. Muscle Nerve 50 : 358–365, 2014     

Quantitative gray‐scale analysis in skeletal muscle ultrasound: A comparison study of two ultrasound devices

Muscle ultrasound is a useful technique to detect neuromuscular disorders. Quantification of muscle echo intensity (EI) using gray‐scale analysis is more reliable and more sensitive compared with visual evaluation of the images. We devised a method to reliably use EI normal values established with one ultrasound device for use with another device. Based on measurements in a dedicated phantom and in 7 healthy subjects, a conversion equation was calculated to convert the mean EI. The reliability of this equation was next evaluated in a follow‐up study of 22 healthy children. Mean muscle EI could be reliably converted from one ultrasound device to another. This allows for normal values obtained with one device to be used with other devices, which is an important step forward toward the use of quantitative muscle ultrasound in daily clinical care. Muscle Nerve, 2009     

Two-dimensional ultrasound imaging of the diaphragm: Quantitative values in normal subjects

Introduction: Real time ultrasound imaging of the diaphragm is an under-used tool in the evaluation of patients with unexplained dyspnea or respiratory failure. Methods: We measured diaphragm thickness and the change in thickness that occurs with maximal inspiration in 150 normal subjects, with results stratified for age, gender, body mass index, and smoking history. Results: The lower limit of normal diaphragm thickness at end expiration or functional residual capacity is 0.15 cm, and an increase of at least 20% in diaphragm thickness from functional residual capacity to total lung capacity is normal. A side to side difference in thickness at end expiration of > 0.33 cm is abnormal. Diaphragm thickness and contractility are minimally affected by age, gender, body habitus, or smoking history. Conclusions: This study confirms previous findings in much smaller groups of normal controls for quantitative ultrasound of the diaphragm and provides data that can be applied widely to the general population. Muscle Nerve 47: 884–889, 2013     

Quantitative neuromuscular ultrasound in the intensive care unit

Introduction: Intensive care unit acquired weakness (ICU‐AW) results from a complex mixture of nerve and muscle pathology, and early identification is challenging. This pilot study was designed to examine the ultrasonographic changes that occur in muscles during ICU hospitalization. Methods: Patients admitted to the ICU for acute respiratory failure were enrolled prospectively and underwent serial muscle ultrasound for thickness and gray‐scale assessment of the tibialis anterior, rectus femoris, abductor digiti minimi, biceps, and diaphragm muscles over 14 days. Results: Sixteen participants were enrolled. The tibialis anterior (P = 0.001) and rectus femoris (P = 0.041) had significant decreases in gray‐scale standard deviation when analyzed over 14 days. No muscles showed significant changes in thickness. Conclusions: Ultrasound is an informative technique for assessing muscles of patients in the ICU, and lower extremity muscles demonstrated increased homogeneity during ICU stays. This technique should be examined further for diagnosing and tracking those with ICU‐AW. Muscle Nerve, 2013