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(1/173) Relationship of lesion location to clinical outcome following microelectrode-guided pallidotomy for Parkinson's disease.

The purpose of this study was to examine the relationship between lesion location and clinical outcome following globus pallidus internus (GPi) pallidotomy for advanced Parkinson's disease. Thirty-three patients were prospectively studied with extensive neurological examinations before and at 6 and 12 months following microelectrode-guided pallidotomy. Lesion location was characterized using volumetric MRI. The position of lesions within the posteroventral region of the GPi was measured, from anteromedial to posterolateral along an axis parallel to the internal capsule. To relate lesion position to clinical outcome, hierarchical multiple regression analysis was used. The variance in outcome measures that was related to preoperative scores and lesion volume was first calculated, and then the remaining variance attributable to lesion location was determined. Lesion location along the anteromedial-to-posterolateral axis within the GPi influenced the variance in total score on the Unified Parkinson's Disease Rating Scale in the postoperative 'off' period, and in 'on' period dyskinesia scores. Within the posteroventral GPi, anteromedial lesions were associated with greater improvement in 'off' period contralateral rigidity and 'on' period dyskinesia, whereas more centrally located lesions correlated with better postoperative scores of contralateral akinesia and postural instability/gait disturbance. Improvement in contralateral tremor was weakly related to lesion location, being greater with posterolateral lesions. We conclude that improvement in specific motor signs in Parkinson's disease following pallidotomy is related to lesion position within the posteroventral GPi. These findings are consistent with the known segregated but parallel organization of specific motor circuits in the basal ganglia, and may explain the variability in clinical outcome after pallidotomy and therefore have important therapeutic implications.  (+info)

(2/173) Neuromyotonia: an unusual presentation of intrathoracic malignancy.

A 48 year old woman is described who presented with increasing muscular rigidity and who was found to have a mediastinal tumour. Electrophysiological studies revealed that the muscular stiffness resulted from very high frequency motor unit activity which outlasted voluntary effort, and which was abolished by nerve block. The abnormal activity may have arisen at the anterior horn cell level. Marked improvement followed the administration of diphenylhydantoin.  (+info)

(3/173) Raclopride and chlorpromazine, but not clozapine, increase muscle rigidity in the rat: relationship with D2 dopamine receptor occupancy.

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%.  (+info)

(4/173) Instrumentally detected changes in motor functioning in patients with low levels of antipsychotic dopamine D2 blockade.

Extrapyramidal side-effects (EPSE) of antipsychotic medication are related to the occupancy of dopamine D2 receptors and there appears to be a threshold of D2 occupancy below which clinically EPSE are unlikely to occur. It is unclear whether there are motor changes produced by 'subthreshold' levels of D2 occupancy that are not detectable by clinical examination. This study was designed to investigate whether a number of electromechanical instrumental techniques could detect 'subthreshold' motor changes and whether these changes correlate with dopamine D2 occupancy as measured by [11C]-raclopride PET scan. Twenty medication naive patients were studied before and during treatment with low dose haloperidol. Instrumental techniques detected an asymmetrical worsening in motor function with drug treatment despite the failure of the group to experience significant EPSE. These changes did not correlate with D2 occupancy and measurements of rigidity, tremor, and bradykinesia did not closely inter-correlate.  (+info)

(5/173) Contribution of thixotropy, spasticity, and contracture to ankle stiffness after stroke.

OBJECTIVES: Increased resistance to stretch of muscles after stroke may be the result of centrally mediated neural factors such as spasticity or local, peripheral factors such as muscle contracture or thixotropy. The aim was to investigate evidence for an abnormal thixotropic response and compare this with two other factors-contracture and spasticity-which could potentially contribute to muscle stiffness after stroke. METHODS: Thirty patients with stroke whose calf muscles were assessed clinically as stiff and 10 neurologically normal subjects were recruited. To measure thixotropy, their calf muscles were stretched through two cycles after two prestretch conditions: one in which the muscles were maintained in a shortened position and one in which they were maintained in a lengthened position. Spasticity was defined as the presence of tonic stretch reflexes in relaxed muscles. Contracture was defined as being present when maximum passive ankle dorsiflexion fell at least 2 SD below the mean value of the control subjects. RESULTS: Both controls and patients with stroke exhibited a thixotropic response but this was no greater in the patients than the controls. About one third of the patients displayed muscle contracture and most exhibited spasticity. Contracture made a significant contribution (p=0.006) to the clinical measure of calf muscle stiffness while spasticity made a significant contribution (p=0.004) to the laboratory measure of calf muscle stiffness. CONCLUSIONS: Measuring thixotropy at the level of joint movement was sufficiently sensitive to determine the thixotropic response in both neurologically normal subjects and patients impaired after stroke. The thixotropic response was not higher than normal after stroke, suggesting that whereas thixotropy may produce enough immediate resistance to impede movement in those who are very weak, it is not a substantial contributor to long term muscle stiffness. Contracture did significantly contribute to muscle stiffness, supporting the importance of prevention of contracture after stroke. Spasticity contributed to muscle stiffness only when the limb was moved quickly.  (+info)

(6/173) Dissociation of cocaine-antagonist properties and motoric effects of the D1 receptor partial agonists SKF 83959 and SKF 77434.

Previous studies suggest that D1 receptor partial agonists may be viable candidates for development as pharmacotherapies for cocaine addiction. This study investigated the ability of the D1 receptor partial agonists SKF 83959 and SKF 77434 to modulate the behavioral effects of cocaine and compared these effects with those of the reference D1 receptor antagonist SCH 39166 and D1 receptor agonists SKF 81297 and 6-Br-APB. Squirrel monkeys were trained either to respond under a fixed-interval schedule of stimulus-shock termination or to discriminate cocaine from vehicle (procedures useful for evaluating the behavioral stimulant and subjective effects of cocaine, respectively). Additional monkeys were studied with quantitative observational techniques to evaluate the effects of the drugs on various forms of motor behavior. Like SCH 39166, but unlike SKF 81297 and 6-Br-APB, the D1 receptor partial agonists attenuated the behavioral stimulant and discriminative stimulus effects of cocaine in a dose-dependent manner, although maximum antagonism produced by SKF 77434 was not always as great as that produced by SKF 83959 or SCH 39166. In observational studies, SKF 83959 and SKF 77434 produced less severe disruptions in motor behavior than did SCH 39166 and, for SKF 83959, showed a greater separation between the dose required to antagonize the behavioral effects of cocaine and the dose that induced catalepsy (>/=33-fold). These results suggest that D1 receptor partial agonists can act as functional cocaine antagonists with less severe behavioral effects than D1 receptor antagonists. The prominent cocaine-antagonist properties and the low incidence of motoric side effects of SKF 83959 may reflect its unique binding profile at D1 as well as nondopaminergic receptors.  (+info)

(7/173) Amphetamines in the treatment of Parkinson's disease.

Twenty-two patients with Parkinsonism were treated with levoamphetamine and 12 of these with dextroamphetamine. Levoamphetamine resulted in a significant improvement in disability from Parkinsonism, although the reduction in total disability, tremor, akinesia, and rigidity scores was slight (ca 20 percent). Dextroamphetamine in lower dosage also reduced disability by some 17 percent. The most disabled patients, including those also on levodopa, showed the greatest response to amphetamines. Previously, amphetamines have been reported to be a selective treatment for the oculogyric crises of post-encephalitic Parkinsonism. Amphetamines are thought to cause the release of catecholamines from central neurones. Their action in Parkinson's disease may be limited because of pre-existing striatal dopamine deficiency. Side-effects of amphetamines, anorexia, and CNS stimulation are different from those caused by levodopa in patients with Parkinson's disease.  (+info)

(8/173) Prevention of porcine malignant hyperthermia by epidural block.

Malignant hyperthermia in susceptible swine was completely blocked by epidural anesthesia with lidocaine. Incomplete epidural anesthesia modified the disease but did not prevent it. These studies indicate the importance of the nervous system in the triggering of malignant hyperthermia. (Key words: Hyperthermia, malignant; Anesthetic technique, peridural.).  (+info)