Withdrawal reflexes in the upper limb adapt to arm posture and stimulus location

Introduction: Withdrawal reflexes in the leg adapt in a context‐appropriate manner to remove the limb from noxious stimuli, but the extent to which withdrawal reflexes adapt in the arm remains unknown. Methods: We examined the adaptability of withdrawal reflexes in response to nociceptive stimuli applied in different arm postures and to different digits. Reflexes were elicited at rest, and kinetic and electromyographic responses were recorded under isometric conditions, thereby allowing motorneuron pool excitability to be controlled. Results: Endpoint force changed from a posterior–lateral direction in a flexed posture to predominantly a posterior direction in a more extended posture [change in force angle (mean ± standard deviation) 35.6 ± 5.0°], and the force direction changed similarly with digit I stimulation compared with digit V (change = 22.9 ± 2.9°). Conclusions: The withdrawal reflex in the human upper limb adapts in a functionally relevant manner when elicited at rest. Muscle Nerve 49 : 716–723, 2014     

Muscle intrusion as a potential cause of carpal tunnel syndrome

Introduction: The aim of this study was to determine whether there is an association between flexor digitorum and lumbrical muscle intrusion into the carpal tunnel and carpal tunnel syndrome (CTS). Methods: Five hundred thirteen manual laborers (1026 wrists) were evaluated with ultrasound to determine whether those with CTS had more muscle intrusion into the carpal tunnel than those without CTS. One hundred ninety of the participants without CTS at baseline (363 wrists) were followed over 1 year to determine whether muscle intrusion at baseline predicted the development of CTS. Results: Participants with CTS had more muscle within the carpal tunnel with the wrist in the neutral (P = 0.026) and flexed (P = 0.018) positions than those without CTS. Baseline muscle intrusion did not predict development of CTS at 1 year. Conclusions: Muscle intrusion into the carpal tunnel is associated with CTS, but muscle intrusion alone does not predict the development of CTS over the course of a year. Muscle Nerve 50: 517–522, 2014     

Sibling concordance for clinical features of Duchenne and Becker muscular dystrophies

Introduction: The correlation of markers of disease severity among brothers with Duchenne or Becker muscular dystrophy has implications for clinical guidance and clinical trials. Methods: Sibling pairs with Duchenne or Becker muscular dystrophy (n = 60) were compared for ages when they reached clinical milestones of disease progression, including ceased ambulation, scoliosis of ≥ 20°, and development of cardiomyopathy. Results: The median age at which younger brothers reached each milestone, compared with their older brothers ranged from 25 months younger for development of cardiomyopathy to 2 months older for ceased ambulation. For each additional month of ambulation by the older brother, the hazard of ceased ambulation by the younger brother decreased by 4%. Conclusions: The ages when siblings reach clinical milestones of disease vary widely between siblings. However, the time to ceased ambulation for older brothers predicts the time to ceased ambulation for their younger brothers. Muscle Nerve 49 : 814–821, 2014     

The effects of strength,aerobic, and concurrent exercise on skeletal muscle damage in rats

Introduction: In this study we examined oxidative stress and skeletal muscle damage resulting from acute strength, aerobic, or concurrent exercise in rats. Methods: The animals were divided into control (C), strength (SE), aerobic (AE), and combined (CE) exercise groups. They were euthanized at 3 different time‐points (6, 24, and 48 h) after acute exercise. Results: SE exercise rats had increased dichlorofluorescein oxidation at 6 h post‐exercise and decreased superoxide dismutase activity at all time‐points. Glutathione peroxidase activity and sulfhydryl levels were increased in the AE group at 48 h post‐exercise. Serum lactate dehydrogenase activity was increased in the SE and CE groups at 24 h and in the AE group at 48 h. Echo intensity was elevated at 24 h for all groups. Conclusions: Forty‐eight hours was sufficient for complete recovery from oxidative stress and muscle damage in the SE and CE groups, but not in the AE group. Muscle Nerve 50 : 79–86, 2014     

Blood‐based diagnostic testing for Pompe disease: Consistency between GAA enzyme activity in dried blood spots and GAA gene sequencing results

Introduction: We have identified a large consanguineous Lebanese family with 5 individuals with severe childhood‐onset recessive sensory loss associated with deafness and variable optic atrophy. Methods: Autozygosity mapping was performed in all affected individuals, followed by whole‐exome sequencing (WES) in 2 individuals. Results: WES identified a homozygous missense mutation (c.916G>A, p.G306R) in the cerebral riboflavin transporter SLC52A2, recently shown to cause Brown‐Vialetto‐Van‐Laere syndrome (BVVLS), which is considered primarily a motor neuronopathy. Our patients have a phenotype distinct from BVVLS, characterized by severe progressive sensory loss mainly affecting vibration and proprioception that evolves to include sensorineural hearing loss in childhood, variable degrees of optic atrophy, and marked upper extremity weakness and atrophy. Treatment of 3 patients with 400 mg/day riboflavin over 3 months produced definite clinical improvement. Conclusions: Mutations in SLC52A2 result in a recognizable phenotype distinct from BVVLS. Early recognition of this disorder is critical, given its potential treatability. Muscle Nerve 50 : 775–779, 2014     

Preoperative Prediction of Failure Following Two-Stage Revision for Knee Prosthetic Joint Infections

While two-stage revision is the gold standard for treatment of knee prosthetic joint infection (PJI), it is not without risk. The purpose of this study was to develop a tool to preoperatively predict the probability that a two-stage revision would fail to eradicate knee PJI. 3,809 surgical cases were retrospectively reviewed and data were collected from 314 charts. Overall, 105 (33.4%) cases failed to eradicate PJI using this procedure. Univariate analysis identified multiple variables independently associated with reinfection. Logistic regression was used to generate a model (bootstrap-corrected concordance index of 0.773) predicting failure of infection eradication. Preoperative knowledge of a high probability of failure may improve risk assessment, lead to more aggressive management, and allow for time to consider alternative therapies.