Assessment of spasticity:from EMG to patients' perception

Spasticity is a common phenomenon which often develops after an upper motor neuro lesion, such as stroke, multiple sclerosis or spinal cord injury. The clinical picture after an UMN lesion depends primarily upon its location and extent, and the time since it occurred, rather than on the pathogenesis of the lesion. Spasticity is part of the positive phenomena, characterized by an exaggerated motor response, elicited for instance during physical examination. The interval between an acute lesion and the appearance of spasticity varies from days to months

Muscle activation patterns of knee flexors and extensors during passive and active movement of the spastic lower limb in chronic stroke patients

The aim of this study was to describe the characteristics of spasticity, quantified as muscle activity during stretch, during passive and active movement. For this cross sectional study 19 stroke patients with spasticity in the lower limb were recruited. Reflex activity was studied with surface electromyography of knee flexor and extensor muscles during passive and active movement of the lower leg.\ud \ud On both the affected and unaffected side, root mean square values of the knee extensor muscles, while stretched, were higher during active than during passive movement (p < 0.05). For the vastus lateralis (VL) the correlation was moderate (ρ = 0.54, p = 0.022), for the rectus femoris (RF) high (ρ = 0.83, p < 0.001). For the semitendinosus (ST) the correlation was low (ρ = 0.27) and not significant.\ud \ud During active movement the correlation between VL activity and activity of the antagonist ST, as an indicator for co-contraction of the affected muscles, was marked (ρ = 0.73, p = 0.001). A moderate negative correlation was found between reflex activity of RF during passive stretch and the active range of motion (ρ = −0.51, p = 0.027).\ud \ud The results show that a passive stretch test alone is insufficient either as assessment method for spasticity during active motor tasks or as a measure for motor control.\ud \ud \u

Analytic and synthetic pitch of two-tone complexes

An experiment was performed in which subjects had to judge whether the pitch of two sequential sounds went up or down. The sounds were harmonic two-tone complexes. They were constructed in such a way that the frequency of one harmonic remained fixed, the frequency of the other went up or down, and the missing fundamental moved in the opposite direction. Results show that, for partials of low harmonic order, most subjects tend to follow the frequency of the moving partial, whereas for partials of order 6 or higher, responses are divided more or less equally between tracking of the moving partial and tracking of the missing fundamental

Analytic and holistic pitch perception in two-tone complexes

An experiment was performed in which subjects had to judge whether the pitch of two sequential sounds went up or down. The sounds were harmonic two-tone complexes. They were constructed in such a way that the frequency of one harmonic remained fixed, the frequency of the other went up or down, and the missing fundamental moved in the opposite direction. Results show that for partials of low harmonic order subjects tend to follow the frequency of the moving partial (analytic pitch perception). For partials of order 6 or higher, about half the observer population retains the analytic mode, whereas the other half switches to a synthetic or holistic mode of perception in which the perceived pitch follows the missing fundamental. The findings are accounted for in terms of the dominant region and aural resolution

Analytic and holistic pitch perception in two-tone complexes

An experiment was performed in which subjects had to judge whether the pitch of two sequential sounds went up or down. The sounds were harmonic two-tone complexes. They were constructed in such a way that the frequency of one harmonic remained fixed, the frequency of the other went up or down, and the missing fundamental moved in the opposite direction. Results show that for partials of low harmonic order subjects tend to follow the frequency of the moving partial (analytic pitch perception). For partials of order 6 or higher, about half the observer population retains the analytic mode, whereas the other half switches to a synthetic or holistic mode of perception in which the perceived pitch follows the missing fundamental. The findings are accounted for in terms of the dominant region and aural resolution

Analytic and holistic pitch perception in two-tone complexes

An experiment was performed in which subjects had to judge whether the pitch of two sequential sounds went up or down. The sounds were harmonic two-tone complexes. They were constructed in such a way that the frequency of one harmonic remained fixed, the frequency of the other went up or down, and the missing fundamental moved in the opposite direction. Results show that for partials of low harmonic order subjects tend to follow the frequency of the moving partial (analytic pitch perception). For partials of order 6 or higher, about half the observer population retains the analytic mode, whereas the other half switches to a synthetic or holistic mode of perception in which the perceived pitch follows the missing fundamental. The findings are accounted for in terms of the dominant region and aural resolution

Patient ratings of spasticity during daily activities are only marginally associated with long-term surface electromyography

AIM: To investigate the association between subjective spasticity ratings and objective spasticity measurement using a new tool for spasticity assessment, that is long-term surface electromyography (sEMG) recordings during daily activities. For monitoring, processing and analysis of this long-term sEMG data, a muscle activity detection algorithm was developed. METHOD: sEMG of the rectus femoris, vastus lateralis, adductor group and semitendinosus of 14 complete spinal-cord-injured patients, in whom voluntary muscle contraction was absent, was recorded continuously during daily activities. Synchronously, subjects stored their activities in a diary and scored their experienced level of spasticity on the Visual Analogue Scale (VAS) for that particular activity. sEMG data were analysed using a high-quality burst-detection algorithm that was developed and validated within this study. Derived sEMG parameters were clustered using principal-component analysis (PCA) and used in a linear mixed model analysis to study their association with VAS. RESULTS: VAS scores appeared significantly associated with the PCA components representing the number and the duration of bursts, but not burst amplitude. Furthermore, VAS scores were associated with the activity performed. The percentage explained variance was, however, low, that is 27-35%. CONCLUSIONS: Patient ratings of the level of spasticity appear poorly associated with spasticity in terms of involuntary muscle activity assessed with long-term sEMG recordings. It is likely that other factors such as pain and cognitions are also incorporated in these patient ratings. Clinicians are therefore strongly advised to perform complementary objective assessments using long-term sEMG recordings.\ud \ud \ud \u

Influence of posture and muscle length on stretch reflex activity in poststroke patients with spasticity

Objective To investigate the influence of different positions on stretch reflex activity of knee flexors and extensors measured by electromyography in poststroke patients with spasticity and its expression in the Ashworth Scale