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Toxins Apr 2021The simple definition of tone as the resistance to passive stretch is physiologically a complex interlaced network encompassing neural circuits in the brain, spinal... (Review)
Review
The simple definition of tone as the resistance to passive stretch is physiologically a complex interlaced network encompassing neural circuits in the brain, spinal cord, and muscle spindle. Disorders of muscle tone can arise from dysfunction in these pathways and manifest as hypertonia or hypotonia. The loss of supraspinal control mechanisms gives rise to hypertonia, resulting in spasticity or rigidity. On the other hand, dystonia and paratonia also manifest as abnormalities of muscle tone, but arise more due to the network dysfunction between the basal ganglia and the thalamo-cerebello-cortical connections. In this review, we have discussed the normal homeostatic mechanisms maintaining tone and the pathophysiology of spasticity and rigidity with its anatomical correlates. Thereafter, we have also highlighted the phenomenon of network dysfunction, cortical disinhibition, and neuroplastic alterations giving rise to dystonia and paratonia.
Topics: Animals; Brain; Dystonia; Humans; Muscle Contraction; Muscle Hypertonia; Muscle Rigidity; Muscle Spasticity; Muscle Tonus; Muscle, Skeletal; Neural Pathways; Spinal Cord
PubMed: 33923397
DOI: 10.3390/toxins13040282 -
British Journal of Pharmacology Apr 2023Fentanyl is a key therapeutic, used in anaesthesia and pain management. It is also increasingly used illicitly and is responsible for a large and growing number of... (Review)
Review
Fentanyl is a key therapeutic, used in anaesthesia and pain management. It is also increasingly used illicitly and is responsible for a large and growing number of opioid overdose deaths, especially in North America. A number of factors have been suggested to contribute to fentanyl's lethality, including rapid onset of action, in vivo potency, ligand bias, induction of muscle rigidity and reduced sensitivity to reversal by naloxone. Some of these factors can be considered to represent 'anomalous' pharmacological properties of fentanyl when compared with prototypical opioid agonists such as morphine. In this review, we examine the nature of fentanyl's 'anomalous' properties, to determine whether there is really a pharmacological basis to support the existence of such properties, and also discuss whether such properties are likely to contribute to overdose deaths involving fentanyls. LINKED ARTICLES: This article is part of a themed issue on Advances in Opioid Pharmacology at the Time of the Opioid Epidemic. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v180.7/issuetoc.
Topics: Humans; Fentanyl; Analgesics, Opioid; Narcotic Antagonists; Naloxone; Drug Overdose
PubMed: 34030211
DOI: 10.1111/bph.15573 -
Internal Medicine (Tokyo, Japan) Jan 2020Various methods of rehabilitation for dysphagia have been suggested through the experience of treating stroke patients. Although most of these patients recover their... (Review)
Review
Various methods of rehabilitation for dysphagia have been suggested through the experience of treating stroke patients. Although most of these patients recover their swallowing function in a short period, dysphagia in Parkinson's disease (PD) and Parkinson-related disorder (PRD) degenerates with disease progression. Muscle rigidity and bradykinesia are recognized as causes of swallowing dysfunction, and it is difficult to easily apply the strategies for stroke to the rehabilitation of dysphagia in PD patients. Disease severity, weight loss, drooling, and dementia are important clinical predictors. Silent aspiration is a pathognomonic sign that may lead to aspiration pneumonia. Severe PD patients need routine video fluoroscopy or video endoscopy to adjust their food and liquid consistency. Patients with PRD experience rapid progression of swallowing dysfunction. Nutrition combined with nasogastric tube feeding or percutaneous endoscopic gastrostomy feeding should be considered owing to the increased risk of aspiration and difficulty administrating oral nutrition.
Topics: Deglutition; Deglutition Disorders; Disease Progression; Enteral Nutrition; Humans; Hypokinesia; Muscle Rigidity; Parkinson Disease; Pneumonia, Aspiration; Respiratory Aspiration; Stroke Rehabilitation
PubMed: 30996170
DOI: 10.2169/internalmedicine.2373-18 -
Frontiers in Sports and Active Living 2019The foot is a complex system with multiple degrees of freedom that play an essential role in running or sprinting. The intrinsic foot muscles (IFM) are the main local... (Review)
Review
The foot is a complex system with multiple degrees of freedom that play an essential role in running or sprinting. The intrinsic foot muscles (IFM) are the main local stabilizers of the foot and are part of the active and neural subsystems that constitute the foot core. These muscles lengthen eccentrically during the stance phase of running before shortening at the propulsion phase, as the arch recoils in parallel to the plantar fascia. They play a key role in supporting the medial longitudinal arch, providing flexibility, stability and shock absorption to the foot, whilst partially controlling pronation. Much of the foot rigidity in late stance has been attributed to the windlass mechanism - the dorsiflexion of the toes building tension up in the plantar aponeurosis and stiffening the foot. In addition, recent studies have shown that the IFM provide a necessary active contribution in late stance, in order to develop sufficient impedance in the metatarsal-phalangeal joints. This in turn facilitates the propulsive forces at push-off. These factors support the critical role of the foot in providing rigidity and an efficient lever at push-off. During running or sprinting, athletes need to generate and maintain the highest (linear) running velocity during a single effort in a sprinting lane. Acceleration and sprinting performance requires forces to be transmitted efficiently to the ground. It may be of particular interest to strengthen foot muscles to maintain and improve an optimal capacity to generate and absorb these forces. The current evidence supports multiple exercises to achieve higher strength in the foot, such as the "short foot exercise," doming, toes curl, towing exercises or the more dynamic hopping exercises, or even barefoot running. Their real impact on foot muscle strength remains unclear and data related to its assessment remains scarce, despite a recognized need for this, especially before and after a strengthening intervention. It would be optimal to be able to assess it. In this article, we aim to provide the track and field community with an updated review on the current modalities available for foot strength assessment and training. We present recommendations for the incorporation of foot muscles training for performance and injury prevention in track and field.
PubMed: 33344969
DOI: 10.3389/fspor.2019.00046 -
Cureus Dec 2020Stiff-person syndrome (SPS) is a rare and disabling central nervous system disorder with no satisfactory treatment. Muscle rigidity, sporadic muscle spasms, and chronic... (Review)
Review
Stiff-person syndrome (SPS) is a rare and disabling central nervous system disorder with no satisfactory treatment. Muscle rigidity, sporadic muscle spasms, and chronic muscle pain characterize SPS. SPS is strongly correlated with autoimmune diseases, and it is usual to find high titers of antibodies against acid decarboxylase (GAD65). Due to its highly disabling nature and complicated treatment, we aim to create a treatment protocol through a narrative review of currently available treatments that show efficacy. We expect to facilitate management based on treatment responses ranging from first-line medication to refractory medication. We conducted a medical subject heading (MeSH) strategy. We used the term SPS with the subheading treatment: "Stiff-Person Syndrome/Therapy" [MeSH]. An initial data gathering of 270 papers came out with the initial research. After using the inclusion criteria, we had 159 articles. We excluded 31 papers for being either systematic reviews, literature reviews, or meta-analysis. From the 128 remaining articles, we excluded another 104 papers because the extraction of the data was not possible or the study outcome did not meet our demands. There are two main treatments for SPS: GABAergic (gamma-aminobutyric acid) therapy and immunotherapy. For treatment, we suggest starting with benzodiazepines as first-line treatment. We recommend adding levetiracetam or pregabalin if symptoms persist. As second-line therapy, we recommend oral baclofen over rituximab and tacrolimus. We also suggest rituximab over tacrolimus. For patients with refractory treatment, we can use intrathecal baclofen, intravenous immunoglobulin (IVIG), or plasmapheresis. We conclude that intrathecal baclofen and IVIG are more effective than plasmapheresis in patients with refractory symptoms. Propofol may be used as a bridge - temporary therapy before initiating a permanent treatment.
PubMed: 33437550
DOI: 10.7759/cureus.11995 -
Sensors (Basel, Switzerland) Feb 2020Rigidity is one of the cardinal symptoms of Parkinson´s disease (PD). Present in up 89% of cases, it is typically assessed with clinical scales. However, these...
Rigidity is one of the cardinal symptoms of Parkinson´s disease (PD). Present in up 89% of cases, it is typically assessed with clinical scales. However, these instruments show limitations due to their subjectivity and poor intra- and inter-rater reliability. To compile all of the objective quantitative methods used to assess rigidity in PD and to study their validity and reliability, a systematic review was conducted using the Web of Science, PubMed, and Scopus databases. Studies from January 1975 to June 2019 were included, all of which were written in English. The Strengthening the Reporting of observational studies in Epidemiology Statement (STROBE) checklist for observational studies was used to assess the methodological rigor of the included studies. Thirty-six studies were included. Rigidity was quantitatively assessed in three ways, using servomotors, inertial sensors, and biomechanical and neurophysiological study of muscles. All methods showed good validity and reliability, good correlation with clinical scales, and were useful for detecting rigidity and studying its evolution. People with PD exhibit higher values in terms of objective muscle stiffness than healthy controls. Rigidity depends on the angular velocity and articular amplitude of the mobilization applied. There are objective, valid, and reliable methods that can be used to quantitatively assess rigidity in people with PD.
Topics: Electromyography; Humans; Joints; Movement; Muscle Rigidity; Muscles; Observational Studies as Topic; Parkinson Disease
PubMed: 32041374
DOI: 10.3390/s20030880