(1) Methods have been developed to measure, analyse and document postural sway. The main parameters studied were: average sway amplitude; length of the sway path per unit time; sway direction and sway position histograms; and the frequency spectra of the antero-posterior and lateral sway components. (2) Postural ataxia was quantitatively studied in three groups of patients with cerebellar lesions: (a) late atrophy of the anterior lobe, (b) tumours of the cerebellar hemisphere and (c) tumours within the vestibulo-cerebellum. Characteristic differences were found. (3) Patients with anterior lobe lesion show a specific 3 Hz postural tremor in the antero-posterior direction. The tremor can be evoked by sudden destabilization in incipient cases. Less characteristic and smaller in amplitude is a mainly lateral sway component with an average frequency of 0.5 Hz. This is also seen in cases with spinal ataxia. Visual stabilization of posture is frequently preserved. Its amount does not correlate with general instability of posture. Tremor and characteristically exaggerated intersegmental responses between head, trunk, hips and legs are interpreted as the consequence of hyper-excitability of postural reflexes in these patients. (4) Patients with lesions of the hemispheres show only slight postural instability without directional preference. Their sway parameters with eyes open are within the 2 sigma range of normals and there is no significant difference from normals in these parameters even when the eyes are closed. Therefore these patients cannot be distinguished from normals by means of their platform recordings. (5) Two patients with posterior vermal and flocculo-nodular lesions were very unstable without preferred axis or frequency of instability. In contrast to the anterior lobe group the instability was characterized by the absence of intersegmental movements.

Methods and parameters are described to quantify body sway as measured by a force-transducing platform. Analogue data representing the coordinates of the body's center of force (COF) are fed into a digital computer. Th following parameters are then calculated and tested for their diagnostic significance: sway path (SP), mean amplitude of sway (MA), mean sway frequency (MF), their lateral and sagittal components, and the quotients sagittal/lateral of these as well as the sway area (SA) circumscribed by the COF. Quotients of eyes open/eyes closed for all these parameters determine the visual stabilization of posture. Sway position and sway direction histograms allow for a more detailed analysis of MA and SP. Despite considerable inter- and intraindividual variance of these parameters (in 28 normals), some of them seem of clinical significance not only for documentation and follow-up studies but also for differential diagnosis. In patients with cerebellar lesions (n = 12), SP and MA were up to 10 times larger with a marked antero-posterior instability, MF being above normal. Patients with labyrinthine lesions (n = 10) showed significant instability only with eyes closed, MF being slightly below normal.

SUMMARY Mechanical properties of relaxed lower leg muscles were assessed by torque measurements during imposed constant velocity dorsiflexion-plantarflexion cycles. At low angular velocities, they exhibited an elastic and an energy-consuming, velocity-independent (plastic) resistance. In most patients with long-standing spasticity, both of these were enhanced. The results support the hypothesis of secondary structural changes of muscles in spasticity.Spastic increase of muscle tone is estimated by the resistance to passive movements in a patient instructed to let go". It is considered to be due to enhanced stretch reflexes. Recent findings, however, indicate that the increase in tone is not sufficiently accounted for by this mechanism. The EMG activity in the gastrocnemius muscle when stretched during the stance and swing phase is rather low relative to an excessive activation of the tibialis anterior.' 2 It is concluded from this finding that the tibialis anterior has to overcome a resistance of non-reflex origin, probably owing to an alteration of passive mechanical properties of the triceps surae muscle. Evidence for an alteration in viscoelastic behaviour of muscles in severe spasticity has been reported previously.

Patients with AC without focal signs and with either evidence for a medical aetiology of delirium or prediagnosed dementia are at a very low risk of having focal lesions in their CCT or MRI.

The maturation of callosal motor fiber connectivity seems to reflect the degree of interhemispheric inhibition between the motor cortices with anisotropy of callosal motor fibers being a potential marker for motor development.