Guidelines on clinical presentation and management of nondystrophic myotonias

The nondystrophic myotonias are rare muscle hyperexcitability disorders caused by gain-of-function mutations in the SCN4A gene or loss-of-function mutations in the CLCN1 gene. Clinically, they are characterized by myotonia, defined as delayed muscle relaxation after voluntary contraction, which leads to symptoms of muscle stiffness, pain, fatigue, and weakness. Diagnosis is based on history and examination findings, the presence of electrical myotonia on electromyography, and genetic confirmation. In the absence of genetic confirmation, the diagnosis is supported by detailed electrophysiological testing, exclusion of other related disorders, and analysis of a variant of uncertain significance if present. Symptomatic treatment with a sodium channel blocker, such as mexiletine, is usually the first step in management, as well as educating patients about potential anesthetic complications.     

A well-tolerated core needle muscle biopsy process suitable for children and adults

Serial muscle biopsies within clinical trials for Duchenne muscular dystrophy (DMD) are critical to document therapeutic responses. Less invasive means of sampling muscle are needed. We analyzed a retrospective consecutive case-series cohort of vacuum-assisted core needle muscle biopsy procedures performed on healthy and dystrophic individuals at a single institution assessing for safety and reliability of obtaining sufficient high-quality biopsy tissue for histologic assessment in adult and pediatric subjects. Of 471 muscle cores from 128 biopsy procedures, 377-550 mg of total muscle tissue was obtained per procedure with mean core weight of 129 mg (SD, 25.1 mg). All biopsies were adequate for histological assessment. There were no significant adverse events. This core needle biopsy approach, when combined with improved sample processing, provides a safe means to consistently obtain muscle samples for diagnostic and clinical trial applications.     

Pericapsular hip muscle activity in people with and without femoroacetabular impingement. A comparison in dynamic tasks

ObjectivesCompare anterior pericapsular muscle activity between individuals with and without femoroacetabular impingement syndrome (FAIS) during dynamic tasks, to investigate whether muscle activity is consistent with a role in retracting the capsule to prevent impingement and active restraint of the femoral head in walking.DesignCross-sectional.SettingUniversity-laboratory.ParticipantsThirteen athletes with FAIS and 13 pain-free controls.Main outcome measuresMuscle activity was recorded using fine-wire (Iliocapsularis, iliacus and anterior gluteus minimus) and surface (rectus femoris) electromyography (EMG), during three hip flexion tasks (active and assisted hip flexion; squatting) and four walking trials.ResultsIliocapsularis EMG amplitude was no different between active and assisted hip flexion tasks around 90° of hip flexion in FAIS. There was no difference in EMG between groups in squatting. The pattern of burst activity preceding peak hip extension in iliacus, iliocapsularis, and anterior gluteus minimus was similar in both groups during walking.ConclusionIn FAIS, similar activation of iliocapsularis during active and assisted hip flexion, despite reduced flexion torque demand in the latter, suggests a role in capsular retraction or enhanced hip joint protection. Pericapsular muscle activity in advance of peak hip extension during walking is consistent with a proposed contribution to femoral head control.     

Origin of the 31P MR signal at 5.3 ppm in patients with critical limb ischemia

An unknown intense signal (P_un) with a mean chemical shift of 5.3 ppm was observed in ³¹P MR spectra from the calf muscles of patients with the diabetic foot syndrome. The aim of the study was to identify the origin of this signal and its potential as a biomarker of muscle injury. Calf muscles of 68 diabetic patients (66.3 ± 8.6 years; body mass index = 28.2 ± 4.3 kg/m²) and 12 age‐matched healthy controls were examined by (dynamic) ³¹P MRS (3 T system, ³¹P/¹H coil). Phantoms (glucose‐1‐phosphate, P_i and PCr) were measured at pH values of 7.05 and 7.51. At rest, P_un signals with intensities higher than 50% of the P_i intensity were observed in 10 of the 68 examined diabetic subjects. We tested two hypothetical origins of the P_un signal: (1) phosphorus from phosphoesters and (2) phosphorus from extra‐ and intracellular alkaline phosphate pools. 2,3‐diphosphoglycerate and glucose‐1‐phosphate are the only phosphoesters with signals in the chemical shift region close to 5.3 ppm. Both compounds can be excluded: 2,3‐diphosphoglycerate due to the missing second signal component at 6.31 ppm; glucose‐1‐phosphate because its chemical shifts are about 0.2 ppm downfield from the P_i signal (4.9 ppm). If the P_un signal is from phosphate, it represents a pH value of 7.54 ± 0.05. Therefore, it could correspond to signals of P_i in mitochondria. However, patients with critical limb ischemia have rather few mitochondria and so the P_un signal probably originates from interstitia. Our data suggest that the increased P_un signal observed in patients with the diabetic foot syndrome is a biomarker of severe muscular damage.     

三维磁共振对腭裂术后患者腭咽结构的观察和测量

目的探讨三维磁共振技术观察测量腭咽结构的可行性,并比较腭裂术后成年患者与正常成年人腭咽结构的差异,用于指导腭裂修复术手术方式的选择。方法根据入选标准选择2018年2月至2018年8月就诊于蚌埠医学院第一附属医院整形烧伤科的6例成年男性腭裂修复术后患者(腭裂组),年龄18~26岁,平均21.8岁。招募6例皖北地区健康成年男性(正常组),年龄19~28岁,平均23.3岁。对2组测量对象进行语音检测,评估语音发音和腭咽闭合情况。行正中矢状面静态三维和动态磁共振扫描,在矢状面、冠状面和腭帆提肌平面(斜冠面)测量软腭长、有效软腭长度、腭咽比、腭高、腭帆提肌长度及厚度等32个数据,共测量2次。采用Pearson积矩相关系数对2次数据进行相关性检验,判断测量结果误差大小。使用两独立样本t检验对2组数据进行组间比较。结果所有研究对象均无语音异常,腭咽闭合均完全。2次测量的Pearson积矩相关系数r值范围在0.789~0.925(P<0.05),即2次测量结果误差在可接受范围内。正常组腭帆提肌形态较为流畅,而腭裂组腭帆提肌形态不规则,中线处可观察到不连续现象,且提肌插入软腭时角度明显不同。腭裂组具体测量数据中咽宽为(23.83±3.48)mm、咽深为(29.94±3.52)mm、骨性咽深为(39.68±3.63)mm、腭长比为1.18±0.16、腭咽比为0.87±0.91、发/i:/时软腭膝部和鼻后棘、悬雍垂连线的夹角[PVU角(动)]为(105.68±20.54)°、腭帆提肌内侧段长度为(13.13±1.00)mm、腭帆提肌插入间距为(24.63±2.54)mm、腭帆提肌起点角为(58.0±3.3)mm,均大于正常组,差异具有统计学意义(P<0.05)。腭裂组腭宽为(37.5±1.43)mm、软腭厚度为(9.48±1.03)mm、软腭相对伸长度(/ts/)为(1.09±0.05)mm、安静时鼻后棘和鼻前棘、软腭膝部连线的夹角[APV角(静)]为(180.51±8.55)°、腭帆提肌厚度为(4.07±0.25)mm、腭帆提肌起点间距为(52.27±7.08)mm,均小于正常组,差异具有统计学意义(P<0.05)。结论三维磁共振技术测量腭咽结构方法可行,且腭裂成人和正常成人的腭咽结构、软腭动度和腭帆提肌形态结构存在显著差异,在腭裂早期修复时需要注意提肌的解剖复位,尤其是对作用较大的外侧段的保护和延长,以及软腭瓣分离时有效软腭体的延长。     

Hip muscle atrophy in patients with acetabular labral joint pathology

Intra-articular hip joint pathology is a source of hip and groin pain in active individuals and is thought to be a precursor to hip osteoarthritis. Limited evidence exists to guide appropriate physiotherapy management for these patients. Identification of which hip muscles are affected may help clinicians to develop effective exercise programs. A cross-sectional observational study in a hospital setting was conducted to investigate the size of individual hip abductor, hip extensor, and hip external rotator muscles in patients with acetabular labral joint pathology compared with age and sex matched healthy subjects. Twelve participants (eight females, four males), aged 20–53 years, with a medical diagnosis of unilateral acetabular labral tear and 12 healthy participants were recruited. Magnetic resonance imaging was used to assess cross-sectional areas of the gluteus minimus, gluteus medius, upper gluteus maximus, lower gluteus maximus, piriformis, and quadratus femoris muscles bilaterally. Gluteus medius muscle cross-sectional area was significantly different between groups (P < 0.01, effect size = 0.92) with muscle size found to be smaller in the pathology group. No differences were found for the other hip muscles (P > 0.05). These findings suggest that hip muscles are not all affected equally by the presence of intra-articular hip joint pathology. Atrophy of specific hip muscles, which are important in hip joint and pelvic stability, may alter hip joint function during gait and functional tasks. Clinicians treating patients with intra-articular hip joint pathology may need to prescribe exercises targeting the specific muscles with demonstrated dysfunction. Clin. Anat. 33:538–544, 2020. © 2019 Wiley Periodicals, Inc.     

Assessing the variability of 23Na MRI in skeletal muscle tissue: Reproducibility and repeatability of tissue sodium concentration measurements in the lower leg at 3 T

The goal of this study was to evaluate the reproducibility and repeatability of tissue sodium concentration (TSC) measurements using ²³Na MRI in skeletal muscle tissue. ²³Na MRI was performed at 3 T on the right lower leg of eight healthy volunteers (aged 28 ± 4 years). The examinations were repeated at the same site after ~ 22 weeks to assess the variability over a medium‐term period. Additionally, they were scanned at a second site shortly before or shortly after the first visit (within 3 weeks) to evaluate the inter‐site reproducibility. Moreover, we analysed the effect of B₀ correction on the variability. Coefficients of variations (CVs) from mean TSC values as well as Bland–Altman plots were used to assess intra‐site repeatability and inter‐site reproducibility. In phantom measurements, the B₀ correction improved the quantitative accuracy. We observed differences of up to 4.9 mmol/L between the first and second visit and a difference of up to 3.7 mmol/L between the two different sites. The CV for the medium‐term repeatability was 15% and the reproducibility CV was 9%. The Bland–Altman plots indicated high agreement between the visits in all muscle regions. The systematic bias of ?0.68 mmol/L between site X and Y (P = 0.03) was slightly reduced to ?0.64 mmol/L after B₀ correction (P = 0.04). This work shows that TSC measurements in healthy skeletal muscle tissue can be performed with good repeatability and reproducibility, which is of importance for future longitudinal or multicentre studies.