In a randomised, double‐blind study, the effects of intramuscular injection of botulinum toxin type A (BtA) into the upper limb were compared with those of normal saline solution in 14 patients with cerebral palsy; their mean age was 9 years. Range of movement and function were assessed before injection and at 2 and 12 weeks after injection. BtA injection significantly increased maximum active elbow and thumb extension and significantly reduced tone at wrist and elbow. The hand grasp‐and‐release score improved, representing a modest functional change, but fine motor function, assessed by the ability to pick up coins, did not improve and in some cases deteriorated temporarily. The most notable subjective change was the cosmetic benefit of reduced involuntary elbow flexion. The tone‐reducing effect of BtA was clinically detectable in comparison with the placebo and patients and parents perceived the change as beneficial. The median of changes in the treatment group was small but the range Was large, suggesting that BtA can be useful in selected patients.

SUMMARY1. The resonance of the relaxed wrist for flexion-extension movements in the horizontal plane has been investigated by using rhythmic torques generated by a printed motor.2. In the normal subject the resonant frequency of the wrist is ca. 2 Hz unless the torque is reduced below a certain critical value when the system is no longer linear and the resonant frequency rises.3. This critical torque level, and the damping are both less in women than men. 4. The resonant frequency is uninfluenced by surgical anaesthesia. 5. With added bias the increase of resonant frequency at low torques still occurs although the hand is now oscillating about a displaced mean position.6. It follows that the stiffening implied by this elevation of resonant frequency for small movements is neither the result of pre-stressing of the muscles nor of reflex activity.7. With velocity feed-back of appropriate polarity the system will oscillate spontaneously at its resonant frequency. If the peak driving torque is progressively reduced the resonant frequency increases abruptly, indicating that the system has stiffened.8. Perturbations delivered to the wrist may reduce its stiffness. The postural system is thixotropic with a 'memory time' of 1-2 s.9. The resonant frequency is elevated in voluntary stiffening.

Rhythmicity during muscular contration has long been studied. The earliest observations dealt with the sounds that can be heard on listening to a contracting muscle and were naturally limited by the poor sensitivity of the ear at low frequencies. When, in the second half of the nineteenth century, graphic recording techniques became readily available a number of papers were published dealing with the periodicity that can be recorded in myograms. Of outstanding interest were the findings of Schafer (1886) MethodsMost of the observations reported in this paper have been concemed with acceleration rather than displacement. The measurement of acceleration is advantageous for three reasons. First, the application of Newton's second law indicates that the force put into a limb will be reflected in its acceleration. Secondly, graphic records of acceleration reveal smaller discontinuities during the course of a movement than could be detected by comparable recording of displacement. Thirdly, the technique is simple and versatile.An accelerometer double diode (Mullard DDR 100) was attached to a part of the limb under investigation.The anodes of such a valve are deflected by acceleration in one plane. Movement of the valve upset the balance of a bridge circuit, and the electrical output was fed through an Ediswan electro-encephalographic amplifier to both an ink-writer and an oscillograph.The natural period of the accelerometer valve was 1,000 c./sec., and it may be regarded as accurately recording motion having sinusoidal components up to 250 c./sec. (manufacturer's figures). The response of the ink-writer was more limited; signals higher in frequency than 90 c./sec. would be seriously attenuated.In order to ensure that the ink-writers on which the bulk of the recordings were to be made were able satisfactorily to follow the movements which we were likely to encounter, over 100 oscilloscope recordings were 260

No abstract

SUMMARY Observations on wrist tremor have been made in the horizontal plane using a tremorograph of new design. A small tap to the hand gave rise to a decrementing series of oscillations at about 9 Hz; as these effects were seen in relaxed and in anaesthetised subjects they were not due to neural reflexes. With the fingers partially extended the spontaneous tremor increased markedly and taps again gave rise to a series of oscillations. Under these circumstances there was no modulation of the EMG. It is accordingly concluded that mechanical wrist resonance plays a major role in the forms of tremor studied. sought to investigate the response to gentle taps which are nonetheless sufficient to generate a disturbance which is larger than the prevailing tremor; much of this work involved a tremorograph of new design. This paper describes oscillations similar to those found by Lippold but which are not accompanied by synchronised EMG activity. Furthermore, we show that these oscillatory transients can occur in conditions in which all active muscular activity is suspended. The short range resonant passive behaviour of the wrist joint and associated structures is a new finding which calls for significant modification of current theories.