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Query: UMLS:C0026837 (muscle rigidity)
 1,077 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Studies of orofacial motor control in Parkinson's disease (PD) have demonstrated that these subjects may exhibit hypokinesia and bradykinesia, as well as increased muscle tone. Yet the relationship between aberrations of orofacial movement and muscle rigidity remains unclear. Measures of labial muscle rigidity and movement were made for 12 parkinsonian and 9 age-matched control subjects. Displacement amplitude, peak instantaneous velocity, and movement time were evaluated during repetitive syllable productions. The results showed that while mean parkinsonian displacement amplitudes and velocities were lower than the normal control subjects, there was no statistical relationship between labial rigidity and the degree of movement abnormality. It is concluded that while rigidity may play a part in the overall disability, it does not sufficiently explain the labial articulatory difficulties associated with parkinsonism. This is in agreement with the literature on limb rigidity and movement aberrations in PD, suggesting that rigidity and bradykinesia may represent independent pathophysiological phenomena.
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PMID:Labial kinematics during speech in patients with parkinsonian rigidity. 365 93

Clinical Neurophysiology brings about 2 major contributions in the study of Parkinson's disease: on the one hand, it makes it possible to measure the motor troubles; on the other, it enables their pathophysiological analysis. The 3 classical signs must be studied separately. Tremor can easily be recorded by electromyography. Moreover, its parkinsonian nature can be specified by studying the resetting of EMG bursts following electrical stimulation of the motor nerve. A pace maker has been demonstrated in the thalamus from where rhythmic messages are first sent to motor cortex and thereafter reverberated to spinal motoneurons. Rigidity can be assessed by sophisticated but not generalized methods. It is easier to evaluate it by long-loop responses evoked by proprioceptive or exteroceptive stimulations. These responses reflect activity in pathways relaying in supraspinal structures. Contrary to spasticity, rigidity is not basically due to dysfunctions in segmentary spinal circuits. It is more likely that it depends on hyperactive and hyperexcitable long loop pathways. This hypothesis is in agreement with well established facts showing that parkinsonian hypertonia vanishes after dorsal root section. Akinesia is complex semeiologically. It is made of various components some of which can be measured. Reaction times and movement times provide interesting data which however are not strictly correlated with the motor handicap. Motor programmes are assembled in normal delays but they are not "called upon" correctly, reflecting a disturbance in the motor planning. A lack of "energetization" of the motor cortex and the pyramidal tract is likely. A functional disconnection between the motor program/plan side and the execution side can be hypothesized to explain the 3 major signs; on the one hand, neural messages are not correctly transferred to the pyramidal system, on the other, spinoencephalospinal loops on the execution side become more active as they escape from the control normally exerted by the plan/program side where basal ganglia play a prominent role.
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PMID:[Clinical neurophysiology in the evaluation and physiopathology of Parkinson's disease]. 383 95

The aim of the present study was to localize the dopamine receptors involved in the regulation of muscle tone. A strategy was used whereby the effects on muscle tone of injecting the irreversible dopamine receptor antagonist N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) in discrete brain regions were assessed. Increases in muscle tone were measured as changes in electromyographic activity of the gastrocnemius and tibialis muscles of conscious, unrestrained rats. No increases in muscle tone were found after injections of EEDQ into the anterior and posterior striatum, which produced marked reductions in dopamine receptor concentration. The effects of muscle tone of injecting EEDQ into the substantia nigra pars reticulata were also assessed. Large increases in muscle tone were observed associated with inactivation of either D1 or D2 dopamine receptors in the substantia nigra. The increased muscle tone was not reduced by subcutaneous administration of apomorphine, despite the presence of a normal population of striatal dopamine receptors. These findings provide evidence that dopamine receptors in the substantia nigra play an important role in the regulation of muscle tone. Further, they challenge the hypothesis that the muscle rigidity of Parkinson disease results primarily from loss of striatal dopamine receptor stimulation.
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PMID:Dopamine receptors in the substantia nigra are involved in the regulation of muscle tone. 787 37

Increased masticatory muscle tone after administration of suxamethonium has been demonstrated in children when combined with volatile anaesthetics. Whether volatiles are a prerequisite for this phenomenon is not known. In this study upper airway muscle tone, including the tone of the masticatory muscles, was determined in 54 children (age range 2-15 years), anaesthetized with propofol, fentanyl and nitrous oxide and avoiding any use of volatiles. The children were either relaxed with suxamethonium (n = 26) or vecuronium (n = 28). The forces applied during laryngoscopy were used to quantify upper airway muscle tone and were significantly greater in the suxamethonium group than in the vecuronium group: maximally applied force was 25 N versus 21 N (P = 0.008), and mean applied force was 16 N versus 13 N (P = 0.006), respectively. The results of this study indicate that upper airway muscle tone increases after administration of suxamethonium in children independent of the presence of volatile anaesthetics. Moreover, increased muscle tone had no effect on the difficulty of laryngoscopy or the intubation conditions. Increased masseter muscle rigidity after suxamethonium could be due to the very unique characteristics of this muscle.
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PMID:Forces applied during laryngoscopy in children. Are volatile anaesthetics essential for suxamethonium induced muscle rigidity? 794 38

Muscle rigidity and spasms occur with neurological disease and may contribute to contractures and shortening of muscle fibers that can interfere with motor behaviors, such as ambulation, or activities of daily living, such as combing hair, feeding or dressing. The neuromuscular technique (NMT) and muscle energy technique (MET) are nursing interventions that can reduce pain and muscle rigidity, lengthen muscle fibers and increase range of motion necessary for normal motor behavior. Nurses can use these techniques in patients with acute neurological diseases and those recovering in rehabilitation and long-term care settings. With some neurological diseases, muscle rigidity, increased muscle tone and muscle spasms reduce the range of motion of joints and the quality of movement. These changes often lead to contractures and impairments in performing daily tasks or ambulating, and thus, to loss of independence. Soft tissue manipulation can be used to reduce muscle tension and spasms, reduce pain and enhance the range of motion of joints whose function depends on the involved muscles. Soft tissue manipulation may also improve movement during specific tasks. Although the muscle relaxation achieved with manipulation techniques is primarily short-term, long-term effects occur. This article describes two techniques of soft tissue manipulation, their mechanisms of action, assessment and implementation. A case study is used to illustrate application of the techniques and possible long-term effects.
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PMID:Soft tissue manipulation: neuromuscular and muscle energy techniques. 914 Aug 47

The aim of the present study was to investigate the relationship between effects on muscle tone and D2 receptor occupancy of two typical antipsychotic drugs, raclopride and chlorpromazine, and the atypical drug, clozapine. Increased muscle tone (i.e., muscle rigidity), was measured as increases in tonic electromyographic (EMG) activity of the antagonistic muscles of the rat hind limb. D2 dopamine receptor occupancy was assessed in the striatum and substantia nigra, areas involved in the regulation of muscle tone. Raclopride and chlorpromazine produced dose-dependent increases in EMG activity associated with D2 occupancy of 68%-80% in the striatum and 67%-76% in the nigra. No significant increases in EMG were observed with clozapine which showed low D2 occupancy. The results are consistent with those from human studies showing extrapyramidal side effects were associated with striatal D2 occupancy of > 70%.
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PMID:Raclopride and chlorpromazine, but not clozapine, increase muscle rigidity in the rat: relationship with D2 dopamine receptor occupancy. 1037 24

Examination of tone (increased resistance to the passive movement of a joint) is a clinically useful and occasionally neglected part of the neurological examination. Rigidity and spasticity are two distinct types of hypertonia that arise from distinct anatomical pathways. The ability to differentiate between these two entities therefore gives important information regarding localization. Whereas spasticity arises as a result of damage to the corticoreticulospinal (pyramidal) tracts, rigidity is caused by dysfunction of extrapyramidal pathways, most commonly the basal ganglia, but also as a result of lesions of the mesencephalon and spinal cord. Spasticity is characterized by abnormally high muscle tone, which often asymmetrically affects antagonistic muscle groups. It is both amplitude and velocity dependent and is therefore best assessed using rapid movements of the relevant joint to effect abrupt stretching of the muscle group involved. When a threshold velocity, angle, or amplitude is reached, a sudden increase in tone can be detected as a characteristic "catch." Rigidity differs from spasticity in that the increased tone remains constant throughout the range of movement of the joint. It is independent of velocity and should even be detectable with very slow movements. It is present in flexors and extensor muscle groups equally, giving rise to a uniform quality in all directions often described as "lead pipe" rigidity. Given that rigidity frequently arises in diseases of the basal ganglia, a tremor can coexist, giving rise to an interrupted "cogwheeling" effect. We herein describe an approach to the examination of patients with rigidity and spasticity.
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PMID:How Do I Examine Rigidity and Spasticity? 3036 19