Disturbed grip function in women with rheumatoid arthritis.

OBJECTIVE: Hand dysfunction is a frequent cause of disability in rheumatoid arthritis (RA). In patients with RA, we studied the precision grip-lift sequence in relation to pain, stiffness, and observer assessed hand function and their relation to patients' experience of clumsiness and tendency to drop objects. METHODS: Performance of the precision grip-lift sequence was studied in 23 women with RA and 7 age and sex matched controls. The results were correlated to self-estimation of pain and stiffness of hands and to observer assessed measurements of hand function. RESULTS: A prolongation of the preload and loading phases and of the acceleration part of the transition phase as well as a disturbance of the safety margin (SM) during precision grip-lift were noted. Patients with good hand function (low Grip Ability Test score; GAT) displayed normal or increased SM compared to the healthy controls, whereas patients with more pronounced disease exhibited a lower SM. Disturbances seen in the precision grip-lift performance were related to stiffness, range of motion, and GAT score. In RA patients with decreased hand function the SM was correlated to feeling of clumsiness, but did not explain the frequency of object dropping. CONCLUSION: A disturbance in the precision grip-lift performance was noted in patients with RA. These grip performance changes need further investigation to determine possible mechanisms.

On automatic determination of movement phases in manual transport during the precision grip.

Integrated movement and force analysis of the precision grip-lift sequence (grasping an object between index finger and thumb) is a useful tool in studies on manipulative hand functions. The everyday Manual Transport tasks, moving objects from one place to another, exhibits powerful test possibilities because it includes the precision grip. In this study, as a step towards the exploitation of these possibilities, we created an algorithm that extracts sequence of phases in this task. The mathematical and dynamical properties of the movement and force signals were used to determine the start and the end of each phase. The grip-lift synergy was quantified by the correlation coefficient during each phase. Eight patients with Parkinson's Disease (PD) and 10 healthy persons were studied. The PD patients were tested both in the medicated (ON) and the unmedicated (OFF) state. The object was lifted with the index finger and the thumb, moved a short distance, and put down on a shelf. The preliminary results of these experiments displayed significantly higher coordination between the grip and load forces in the initial phases, before the lift was completely established, than during the transport phases. This was evident both in PD patients and healthy subjects. This method provides an automatic analysis of the motor performance during an arm-hand movement that is important in daily life to aid in clinical diagnosis.

Action tremor during object manipulation in Parkinson's disease.

In previous studies of fingertip forces during precision grip in subjects with Parkinson's disease (PD), we observed regular oscillations in isometric force. The present study characterizes the nature of these oscillations. Fingertip forces were recorded from the index finger and thumb during precision grip-lifts with a 300 g and 900 g object in 10 subjects with PD and 20 healthy control subjects. Fourier analysis confirmed that all subjects with PD exhibited force oscillations with a clearly definable frequency (approximately 7-11 Hz). Five of these subjects also exhibited a second lower frequency peak (approximately 5 Hz). Approximately half of the 20 control subjects displayed a single frequency peak (approximately 8-12 Hz), which was generally lower in amplitude than in the subjects with PD (representing enhanced physiological tremor), whereas the remaining control subjects had low-amplitude, broad-based spectra (representing physiological tremor). The amplitude of the force oscillations was higher for lifts with the heavier object in both the control subjects and subjects with PD. L-Dopa resulted in a decreased tremor amplitude but did not influence the frequency. The force oscillations of the two opposing digits normal to the grip surfaces were in phase, whereas the oscillations tangential to the grip surfaces were often out of phase. The results suggest that the multipeaked force rate trajectories reported previously are caused by action tremor. The similarity of force oscillations in subjects with PD and healthy control subjects suggests common tremor-generating mechanisms and supports the notion that the parkinsonian action tremor (AT) is an exaggerated form of physiological tremor. These findings provide insight into the impaired hand function observed in individuals with PD.

Anticipatory control of manipulative forces in Parkinson's disease.

In a previous study we found that subjects with Parkinson's disease (PD) had an impaired capability to initiate and sequence successive movement phases during lifts of small objects using the precision grip, and that they had regular oscillations in the force rates. The present study examined whether these subjects could use anticipatory control, in which the force output is scaled prior to liftoff, based on the object's physical properties. Subjects lifted an instrumented test object between the tips of the thumb and index finger while the employed grip force, load force (vertical lifting force), and corresponding time derivatives were recorded. In the first experiment, the object's weight was varied to assess its influence on the isometric force output. Subjects with PD scaled the isometric force increase according to the object's weight. In another experiment, the weight changed in proportion to the volume to determine whether subjects could make associative transformations between visual size information and the weight of the object. Subjects with PD still scaled the forces toward the expected weight, proportional to the volume of the object. Finally, programmed adjustments in force to sudden self-induced load changes were examined while subjects dropped a disk with one hand into a plate attached to the bottom of the grip instrument, held with the other hand. Subjects with PD had preparatory increases in the grip force prior to the disk contact, which matched the change in load, though may have been more dependent on visual feedback. We conclude that subjects with PD are capable of using anticipatory control to parameterize the isometric force output during a familiar lifting task.

Coordination of manipulative forces in Parkinson's disease.

The coordination of manipulative forces was examined in 10 subjects with Parkinson's disease (PD) both OFF and ON medication while they grasped and lifted a small object using the precision grip. The development of grip (squeeze) force and load (vertical lifting) force was recorded and compared to a group of age-matched control subjects. Subjects with PD often exhibited a prolonged delay between the first digit contact with the object and initiation of the lifting drive. These subjects also exhibited stepwise increases in force, with regular oscillations in the force rates. However, once the vertical drive began, the main increase in grip and load force generally was in parallel and most other temporal aspects of the force coordination were similar to those of the control subjects. The extent to which the movement initiation was delayed was related to the stage of the disease, and most subjects improved ON medication. When the object was held in the air, subjects with PD used a grip force level which was similar to that of the control subjects, and all subjects adjusted their grip force according to the surface texture. Furthermore, they exhibited proper reflexive corrections to sudden changes in load (object perturbations), suggesting intact sensorimotor integration. We conclude that the most obvious impairments in the coordination of this task were delayed initiation of the grip-lift sequence and tremor-like oscillations superimposed on otherwise normal force.

Single-dose L-dopa response in early Parkinson's disease: measurements with optoelectronic recording technique.

Twenty-five patients with suspected Parkinson's disease were submitted to optoelectronic movement analysis with the Posturo-Locomotor-Manual (PLM) test before and 60 min after a single dose of L-Dopa. They were then examined clinically for diagnosis. Two patients were excluded due to L-Dopa intolerance. Seventeen of the remaining patients were classified as having Parkinson's disease. The movement time (MT) in the PLM test was increased for all these patients, and they improved their performance after L-Dopa. The degree of improvement was roughly proportional to the pretreatment augmentation of MT in comparison to healthy subjects of the same age. The PLM phase analysis showed a specific disability profile for each individual. Six patients were given diagnoses other than PD. Some improvement was found in one patient with suspected olivopontocerebellar atrophy and one patient with multiple brain injury. Two patients with progressive supranuclear palsy, one with suspected striatonigral degeneration, and one with functional disturbance deteriorated after L-Dopa. In conclusion, truly objective and fully reproducible evaluation of the motor performance before and after a single L-Dopa dose is easily accomplished with computer-assisted modern optoelectronic recording equipment. The technique is a valuable tool for the quantitative measurement of treatment effects and contributes to the differential diagnosis.

Optoelectronic movement analysis in Parkinson's disease: effect of selegiline on the disability in de novo parkinsonian patients--a pilot study.

New opto-electronic camera systems permit easy quantification of the motor performance during natural acts in freely moving humans. We used a simple test movement (PLM test) to quantify the disturbance in the postural (P), locomotor (L) and manual (M) part of the body movement and the coordination of the different movement phases into a smooth motor act. The test movement time was used to quantify the overall performance. With this technique we have measured the effects of selegiline on the degree of parkinsonism in a double-blind, placebo-controlled pilot study of 5 de novo patients with Parkinson's disease. There was a clear trend that selegiline was superior to placebo in reducing the test movement time.

Disability profiles and objective quantitative assessment in Parkinson's disease.

A new technique for quick objective and quantitative determination of important aspects of the motor handicap in movement disorders is presented. A compound, but natural, test movement was used to find out if the degree of dysfunction in postural, locomotor and manual motor functions differed among the patients and if medication influenced these functions differently. After 12 h without medication, 16 patients with Parkinson's disease showed a movement time between 1.5 and 13.6 times that of an age-matched normal subject and a greater performance variability on repeated examination. In some patients the increase of test movement time was caused mainly by the locomotion component while in others the time for the postural or manual part of the movement was more markedly augmented. Thus, a specific motor disability profile was found for each patient and expressed in quantitative terms. The effects of l-dopa treatment were quantified in each patient.

Objective measurement of motor disability in Parkinson's disease.

A kinesiological analysis of complex movement performance was carried out in patients with Parkinson's disease, and in healthy subjects of different ages, with a computer-assisted optoelectronic camera system. A lifting movement entailing simultaneous coordination of rising, walking some steps and a goal-directed manual movement, the PLM test, was used. Speed reduction through normal aging was greatest at higher ages, where the coordination deficits were also most prominent. The increased movement time in parkinsonian patients was due both to deficient simultaneous coordination of postural, locomotor and manual movement phases, and to varying increases in phase durations. It was possible to determine postural, locomotor and manual disability profiles quantitatively, in terms of the relative phase time values. The presented documentation of parkinsonian disability and single-dose effects of l-dopa indicates that the technique is applicable in the objective assessment of disability and pharmacotherapeutic efficacy.