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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 -
Lakartidningen Dec 2021Paroxysmal sympathetic hyperactivity (PSH) is a condition mainly described in patients after traumatic brain injury and it is also known under the terms "autonomic...
Paroxysmal sympathetic hyperactivity (PSH) is a condition mainly described in patients after traumatic brain injury and it is also known under the terms "autonomic storm" and "dysautonomia". It affects between 8-10% of patients after traumatic brain injury and can also affect patients after other neurological diseases, such as anoxic brain injury, stroke, tumors or infections. PSH manifests with six main symptoms: tachycardia, tachypnea, hypertension, hyperthermia, hyperhidrosis and increased muscle tonus. It is of outmost importance to exclude other causes for the symptoms and there are diagnostic criteria established to identify and diagnose PSH. The treatment is pharmacological and non-pharmacological and often multimodal. PSH is probably underdiagnosed and increased awareness is needed.
Topics: Autonomic Nervous System Diseases; Brain Injuries; Brain Injuries, Traumatic; Humans; Hypertension; Tachycardia
PubMed: 34914088
DOI: No ID Found -
Cureus Aug 2021Pseudomyopia is an inappropriately excessive accommodation of the eye due to overstimulation or ciliary spasm, which leads to a marked approximation of the far point.... (Review)
Review
Pseudomyopia is an inappropriately excessive accommodation of the eye due to overstimulation or ciliary spasm, which leads to a marked approximation of the far point. Common symptoms of pseudomyopia include eye strain or fatigue, and it is classified as organic or functional. The latter is due to eye strain and functional increase in the ciliary tonus. Pseudomyopia can vary from being a transient condition or continue to progress to myopia. Head trauma is the most common cause followed by psychiatric illnesses, neurologic diseases, and drug-induced causes. There is an association between psychological stress-inducing events and pseudomyopia as it affects the autonomic nervous system. The human body counteracts anxiety by activating the parasympathetic nervous system, causing ciliary muscle contraction. Underlying psychiatric diseases in pseudomyopia patients have been reported in the past in multiple studies. Generalized anxiety disorder is the most common psychiatric illness associated with pseudomyopia with a positive correlation between anxiety-somatization scores and accommodation amount of the eye. It is strongly advised that a psychiatric consultation should be included in the multidisciplinary evaluation of every case. If patients have coexisting anxiety disorders, a multidisciplinary approach using psychiatric consultations, work environment changes, ocular exercises, and cycloplegic drugs can be used. This review aims to shed light on the association of psychiatric disorders such as anxiety with pseudomyopia.
PubMed: 34589322
DOI: 10.7759/cureus.17411 -
American Journal of Physiology. Lung... Oct 2019
Topics: Animals; Bronchiectasis; Mice; Muscle Tonus; Respiratory System
PubMed: 31508977
DOI: 10.1152/ajplung.00363.2019 -
Nature Communications Jul 2020The relationship between orexin/hypocretin and rapid eye movement (REM) sleep remains elusive. Here, we find that a proportion of orexin neurons project to the...
The relationship between orexin/hypocretin and rapid eye movement (REM) sleep remains elusive. Here, we find that a proportion of orexin neurons project to the sublaterodorsal tegmental nucleus (SLD) and exhibit REM sleep-related activation. In SLD, orexin directly excites orexin receptor-positive neurons (occupying ~3/4 of total-population) and increases gap junction conductance among neurons. Their interaction spreads the orexin-elicited partial-excitation to activate SLD network globally. Besides, the activated SLD network exhibits increased probability of synchronized firings. This synchronized excitation promotes the correspondence between SLD and its downstream target to enhance SLD output. Using optogenetics and fiber-photometry, we consequently find that orexin-enhanced SLD output prolongs REM sleep episodes through consolidating brain state activation/muscle tone inhibition. After chemogenetic silencing of SLD orexin signaling, a ~17% reduction of REM sleep amounts and disruptions of REM sleep muscle atonia are observed. These findings reveal a stabilization role of orexin in REM sleep.
Topics: Action Potentials; Animals; Behavior, Animal; Brain Stem; Disease Models, Animal; Electrodes, Implanted; Electroencephalography; Electromyography; Humans; Male; Mice; Mice, Transgenic; Muscle Tonus; Neurons; Optogenetics; Orexin Receptors; Orexins; Patch-Clamp Techniques; Rats; Rats, Sprague-Dawley; Sleep Deprivation; Sleep, REM; Wakefulness
PubMed: 32694504
DOI: 10.1038/s41467-020-17401-3 -
Journal of Speech, Language, and... May 2022Despite the high prevalence of primary muscle tension dysphonia (MTD-1), its underlying mechanisms and their interrelationships have yet to be fully identified. The... (Review)
Review
PURPOSE
Despite the high prevalence of primary muscle tension dysphonia (MTD-1), its underlying mechanisms and their interrelationships have yet to be fully identified. The objectives of this integrative review were (a) to describe and classify the suggested underlying mechanisms for MTD-1, (b) to appraise the empirical evidence supporting each of the proposed mechanisms, and (c) to summarize the information in an integrative model.
METHOD
PubMed, Scopus, and CINAHL were searched for all publications pertaining to muscle tension dysphonia. Papers were retained if they included theoretical or empirical data pertaining to underlying mechanisms of MTD-1. A total of 921 papers initially qualified for screening, of which 100 remained for consideration in this review. Underlying mechanisms of MTD-1 were extracted using a consensus approach.
RESULTS
Seven broad categories of putative mechanisms involved in MTD-1 were identified: psychosocial, autonomic, sensorimotor, respiratory, postural, inflammatory, and neuromuscular. These categories were further divided into 19 subcategories detailed in the body of this review article. Based on the reviewed evidence, our proposed integrative model presents MTD-1 as an idiosyncratic motor adaptation to physiological perturbation or perceived threat. Under this model, physiologically or psychologically aversive stimuli can instigate a series of motor adaptations at multiple levels of the nervous system, ultimately disturbing muscle activation patterns and their biomechanical outcomes. Importantly, these adaptations appear to have the potential to become chronic even after threatening stimuli are withdrawn.
CONCLUSIONS
The proposed model highlights the importance of personalized rehabilitation in MTD-1 treatment. Limitations of the literature are discussed to provide guidance for future research aimed at improving our understanding of MTD-1.
SUPPLEMENTAL MATERIAL
https://doi.org/10.23641/asha.19586065.
Topics: Dysphonia; Hoarseness; Humans; Muscle Tonus
PubMed: 35446683
DOI: 10.1044/2022_JSLHR-21-00575 -
Journal of Biomechanics May 2023The classical view of muscles as independent motors has been challenged over the past decades. An alternative view has emerged in which muscles are not isolated but... (Review)
Review
The classical view of muscles as independent motors has been challenged over the past decades. An alternative view has emerged in which muscles are not isolated but embedded in a three-dimensional connective tissue network that links them to adjacent muscles and other non-muscular structures in the body. Animal studies showing that the forces measured at the distal and proximal ends of a muscle are not equal have provided undisputable evidence that these connective tissue linkages are strong enough to serve as an extra pathway for muscular force transmission. In this historical review, we first introduce the terminology and anatomy related to these pathways of muscle force transmission and provide a definition for the term epimuscular force transmission. We then focus on important experimental evidence indicating mechanical interactions between synergistic muscles that may affect force transmission and/or influence the muscles' force generating capacity. We illustrate that there may exist different expressions of the highly relevant force-length properties depending on whether the force is measured at the proximal or distal tendon and depending on the dynamics of surrounding structures. Changes in length, activation level or disruption of the connective tissue of neighboring muscles, can affect how muscles interact and produce force on the skeleton. While most direct evidence is from animal experiments, studies on humans also suggest functional implications of the connective tissues surrounding muscles. These implications may explain how distant segments, which are not part of the same joint system, affect force generation at a given joint, and, in clinical conditions, explain observations from tendon transfer surgeries, where a muscle transferred to act as an antagonist continues to produce agonistic moments.
Topics: Humans; Muscle, Skeletal; Animals; Connective Tissue; Muscle Tonus; Muscle Strength
PubMed: 37120913
DOI: 10.1016/j.jbiomech.2023.111575 -
Biochemical Society Transactions Aug 2021Pulmonary arterial hypertension (PAH) is a fatal disease of the cardiopulmonary system that lacks curative treatments. The main pathological event in PAH is elevated... (Review)
Review
Pulmonary arterial hypertension (PAH) is a fatal disease of the cardiopulmonary system that lacks curative treatments. The main pathological event in PAH is elevated vascular resistance in the pulmonary circulation, caused by abnormal vasoconstriction and vascular remodelling. Ion channels are key determinants of vascular smooth muscle tone and homeostasis, and four PAH channelopathies (KCNK3, ABCC8, KCNA5, TRPC6) have been identified so far. However, the contribution of ion channels in other forms of PAH, which account for the majority of PAH patients, has been less well characterised. Here we reason that a variety of triggers of PAH (e.g. BMPR2 mutations, hypoxia, anorectic drugs) that impact channel function may contribute to the onset of the disease. We review the molecular mechanisms by which these 'extrinsic' factors converge on ion channels and provoke their dysregulation to promote the development of PAH. Ion channels of the pulmonary vasculature are therefore promising therapeutic targets because of the modulation they provide to both vasomotor tone and proliferation of arterial smooth muscle cells.
Topics: Animals; Homeostasis; Humans; Ion Channels; Muscle Tonus; Muscle, Smooth, Vascular; Pulmonary Arterial Hypertension
PubMed: 34346486
DOI: 10.1042/BST20210538 -
Otolaryngologia Polska = the Polish... Jun 2020<b>Introduction:</b> Patient-reported outcome measures have been used within the otorhinolaryngologic disorders' field for many years to compare patient's...
<b>Introduction:</b> Patient-reported outcome measures have been used within the otorhinolaryngologic disorders' field for many years to compare patient's perception of the severity of symptoms and the effectiveness of a therapeutic approach. Questionnaires that evaluate dysphagia are relatively complex instruments aimed mostly at patients with neurological or malignant diseases. The ICD-10 classification specifies only one broad term - dysphagia (R13). Introduction of Muscle Tension Dysphagia (MTDg) in 2016 by Kang completed the spectrum of the nomenclature. This dysphagia type is defined as a type of laryngeal muscle tension disorder manifesting primarily as swallowing difficulty with or without any accompanying organic cause, laryngeal hyperresponsiveness and/or nonspecific laryngeal inflammation. <br><b>Aim:</b> Since there were no clear diagnostic and therapeutic perspectives on the group of patients with MTDg, the aim of this work was to analyse selected diagnostic tools used for the evaluation of swallowing disorders in the context of finding the most suitable tools for patients with Muscle Tension Dysphagia. <br><b>Material and method:</b> The material of the work included 61 patients. Each patient underwent otolaryngologic, phoniatric and speech therapist's examination, Functional Endoscopic Evaluation of Swallowing (FEES) and filled out questionnaires concerning dysphonia and dysphagia symptoms. <br><b>Results:</b> The results of the work showed that patients with MTDg were characterised by correct results of FEES examination, prolonged swallowing, features of inappropriate mucous and oropharyngeal muscle function. <br><b>Conclusions:</b> The Swallowing Disorder Scale (SDS), developed by the authors, correlated best with the cause of dysphagia. The questionnaire corresponded well with the degree of severity. In the diagnostic process of MTDg one of the key tasks is the differentiation with patients with non-normative swallowing patterns. Apart from specialistic consultations with otolaryngologist and speech therapist, while diagnosing MTDg we recommend using objective (FEES, videofluroscopy, SEMG) and subjective (SDS, DHI, EAT-10 surveys) assessment tools. In our opinion, the inclusion of questionnaires to detect reflux syndromes is also important in the causal treatment of ailments.
Topics: Deglutition Disorders; Dysphonia; Hoarseness; Humans; Muscle Tonus; Surveys and Questionnaires
PubMed: 33724224
DOI: 10.5604/01.3001.0014.1997 -
Brain and Behavior Feb 2020Systematic studies on increased muscle tone and spasticity late after ischemic stroke, without any selection, are limited. Therefore, we aimed to determine the...
BACKGROUND
Systematic studies on increased muscle tone and spasticity late after ischemic stroke, without any selection, are limited. Therefore, we aimed to determine the prevalence of increased muscle tone, classical spasticity and contracture and predictors of increased muscle tone seven years after stroke.
METHODS
Consecutive patients with acute ischemic stroke <70 years of age (n = 411) were recruited to the Sahlgrenska Academy Study on Ischemic Stroke. Symptoms at index stroke were assessed using the Scandinavian Stroke Scale. Seven years after stroke, survivors (n = 358) were invited for follow-up assessments, of whom 292 agreed to participate and 288 contributed data. Muscle tone according to the Modified Ashworth scale, classical spasticity, and contracture was assessed by a neurologist. The associations between increased muscle tone and characteristics at index stroke and recurrent strokes during follow-up were investigated using logistic regression analysis.
RESULTS
Increased muscle tone was recognized in 99 participants (34%): 94 (33%) in the upper limbs, and 72 (25%) in the lower limbs. Classical spasticity was found in 51 participants (18%) and contracture in 26 (9%). Age (odds ratio [OR] 1.03 [95% confidence interval [CI] 1.00-1.06]), arm paresis (OR 1.76 [95% CI 1.40-2.2]), aphasia (OR 1.68 [95% CI 1.12-2.51]), and facial palsy (OR 2.12 [95% CI 1.10-4.07]) were independent predictors of increased muscle tone.
CONCLUSIONS
One-third of patients with ischemic stroke before 70 years of age showed increased muscle tone at 7-year follow-up. Half of them also had classical spasticity. Age, arm paresis, aphasia, and facial palsy at index stroke were predictors of increased muscle tone poststroke.
Topics: Aged; Contracture; Extremities; Female; Humans; Ischemic Stroke; Long Term Adverse Effects; Male; Muscle Spasticity; Muscle Tonus; Neurologic Examination; Prevalence; Sweden
PubMed: 31893564
DOI: 10.1002/brb3.1509