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Antagonist Muscles (antagonist + muscle)

Distribution by Scientific Domains

Medical Sciences	80%

Selected Abstracts

Hypertonia in childhood secondary dystonia due to cerebral palsy is associated with reflex muscle activation,

MOVEMENT DISORDERS, Issue 7 2009
Johan van Doornik PhD
Abstract It is often assumed that co-contraction of antagonist muscles is responsible for increased resistance to passive movement in hypertonic dystonia. Although co-contraction may certainly contribute to hypertonia in some patients, the role of reflex activation has never been investigated. We measured joint torque and surface electromyographic activity during passive flexion and extension movements of the elbow in 8 children with hypertonic arm dystonia due to dyskinetic cerebral palsy. In all cases, we found significant phasic electromyographic activity in the lengthening muscle, consistent with reflex activity. By correlating activation with position or velocity of the limb, we determined that some children exhibit position-dependent activation, some exhibit velocity-dependent activation, and some exhibit a mixed pattern of activation. We conclude that involuntary or reflex muscle activation in response to stretch may be a significant contributor to increased tone in hypertonic dystonia, and we conjecture that this activation may be more important than co-contraction for determining the resistance to passive movement. © 2009 Movement Disorder Society [source]

Impaired heteronymous somatosensory motor cortical inhibition in dystonia

MOVEMENT DISORDERS, Issue 11 2003
Laura Bertolasi MD
Abstract A typical pathophysiological abnormality in dystonia is cocontraction of antagonist muscles, with impaired reciprocal inhibitory mechanisms in the spinal cord. Recent experimental data have shown that inhibitory interactions between antagonist muscles have also a parallel control at the level of the sensorimotor cortex. The aim of this work was to study heteronymous effects of a median nerve stimulus on the corticospinal projections to forearm muscles in dystonia. We used the technique of antagonist cortical inhibition, which assesses the conditioning effect of median nerve afferent input on motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) in ipsilateral forearm extensor muscles at rest. Nine healthy subjects and 10 patients with torsion dystonia participated in the study. MEPs and somatosensory evoked potentials were normal in patients. In healthy subjects, median nerve stimulation at 15- to 18-msec intervals inhibited the test MEPs in forearm extensors. In dystonic patients, median nerve stimulation delivered at the same conditioning,test intervals elicited significantly less inhibition of the test MEP. On the whole, these data suggest an impaired sensory,motor integration in dystonia and, more specifically, the decreased antagonistic cortical inhibition could suggest that functional interactions between antagonist muscles are primarily impaired at the cortical level. © 2003 Movement Disorder Society [source]

Stiff Limb Syndrome: End of Spectrum or A Separate Entity?

PAIN MEDICINE, Issue 3 2009
Usha K. Misra DM
ABSTRACT Background., Stiff-person syndrome is a rare disorder characterized by rigidity of axial or limb muscles with episodes of co-contraction of agonist and antagonist muscles during the spasms. In some patients axial or limb involvement may predominate and may have unusual manifestations. Design., Case report. Setting., Tertiary care teaching hospital. Patient., A 42-year-old farmer presented with seasonal occurrence of hiccup and vomiting during summer months for the last 3 years. He had painful lower limb spasms lasting for 2,3 minutes every 10,15 minutes for the past 20 days. His neurological examination was normal, erythrocyte sedimentation rate (ESR) was 50 mm at 1st hour, and cerebrospinal fluid protein 78 mg/dL without pleocytosis. Radiograph of chest, abdominal ultrasound, and craniospinal magnetic resonance imaging were normal. The patient improved on diazepam. Conclusion., Our patient is a forme fruste of stiff person syndrome with hiccups and vomiting due to diaphragmatic spasm. [source]

Neural control of shortening and lengthening contractions: influence of task constraints

THE JOURNAL OF PHYSIOLOGY, Issue 24 2008
Jacques Duchateau
Although the performance capabilities of muscle differ during shortening and lengthening contractions, realization of these differences during functional tasks depends on the characteristics of the activation signal discharged from the spinal cord. Fundamentally, the control strategy must differ during the two anisometric contractions due to the lesser force that each motor unit exerts during a shortening contraction and the greater difficulty associated with decreasing force to match a prescribed trajectory during a lengthening contraction. The activation characteristics of motor units during submaximal contractions depend on the details of the task being performed. Indexes of the strategy encoded in the descending command, such as coactivation of antagonist muscles and motor unit synchronization, indicate differences in cortical output for the two types of anisometric contractions. Furthermore, the augmented feedback from peripheral sensory receptors during lengthening contractions appears to be suppressed by centrally and peripherally mediated presynaptic inhibition of Ia afferents, which may also explain the depression of voluntary activation that occurs during maximal lengthening contractions. Although modulation of the activation during shortening and lengthening contractions involves both supraspinal and spinal mechanisms, the association with differences in performance cannot be determined without more careful attention to the details of the task. [source]

Botulinum Toxin, Physical and Occupational Therapy, and Neuromuscular Electrical Stimulation to Treat Spastic Upper Limb of Children With Cerebral Palsy: A Pilot Study

ARTIFICIAL ORGANS, Issue 3 2010
Gerardo Rodríguez-Reyes
Abstract Spasticity has been successfully managed with different treatment modalities or combinations. No information is available on the effectiveness or individual contribution of botulinum toxin type A (BTA) combined with physical and occupational therapy and neuromuscular electrical stimulation to treat spastic upper limb. The purpose of this study was to assess the effects of such treatment and to inform sample-size calculations for a randomized controlled trial. BTA was injected into spastic upper limb muscles of 10 children. They received 10 sessions of physical and occupational therapy followed by 10 sessions of neuromuscular electrical stimulation on the wrist extensors (antagonist muscles). Degree of spasticity using the Modified Ashworth scale, active range of motion, and manual function with the Jebsen hand test, were assessed. Meaningful improvement was observed in hand function posttreatment (P = 0.03). Median spasticity showed a reduction trend and median amplitude of wrist range of motion registered an increase; however, neither of these were significant (P > 0.05). There is evidence of a beneficial effect of the combined treatment. Adequate information has been obtained on main outcome-measurement variability for calculating sample size for a subsequent study to quantify the treatment effect precisely. [source]