Neurophysiological methods for the assessment of spasticity: the Hoffmann reflex, the tendon reflex, and the stretch reflex.

PURPOSE: To review the literature concerning neurophysiological methods to assess spasticity with respect to mechanisms and methodology, and to describe the three most commonly used methods: the Hoffmann reflex (H-reflex), the Tendon reflex (T-reflex), and the Stretch Reflex (SR). METHOD: A systematic internet database search was performed to identify neurophysiological measurement methods of spasticity. A systematic exclusion procedure resulted in 185 included references, completed by additional informal search. For this paper, information about the H-, T- and stretch reflexes was extracted from these references. RESULTS: Although the reflexes are basically monosynaptic, there are many supraspinal pathways which modulate the responses in terms of their amplitude and latency. As a consequence the methods are sensitive to a considerable number of experimental conditions and are characterized by a moderate reliability and sensitivity. Correlations with other (i.e. biomechanical, neurophysiological or clinical) spasticity assessment parameters are moderate to poor. Standardised and broadly accepted protocols are still largely lacking preventing an effective exchange of knowledge. CONCLUSIONS: The clinical and experimental use of the three methods is restricted due to moderate reliability and sensitivity. It is recommended to perform combined neurophysiological-biomechanical assessment of spasticity during active, functional movement.

Theoretical and methodological considerations in the measurement of spasticity.

PURPOSE: To discuss the measurement of spasticity in the clinical and research environments, make recommendations based on the SPASM reviews of biomechanical, neurophysiological and clinical methods of measuring spasticity and indicate future developments of measurement tools. METHOD: Using the results of the systematic reviews of the biomechanical, neurophysiological and clinical approaches, methods were evaluated across three dimensions: (1) validity, reliability and sensitivity to change; (2) practical quality such as ease of use and (3) qualities specific to the measurement of spasticity, for example ability to be applied to different muscle groups. Methods were considered in terms of applicability to research and clinical applications. RESULTS: A hierarchy of measurement approaches was identified from highly controlled and more objective (but unrelated to function) to ecologically valid, but less objective and subject to contamination from other variables. The lack of a precise definition of spasticity may account for the problem of developing a valid, reliable and sensitive method of measurement. The reviews have identified that some tests measure spasticity per se, some phenomena associated with spasticity or consequential to it and others the effect of spasticity on activity and participation and independence. CONCLUSIONS: Methods appropriate for use in research, particularly into the mechanism of spasticity did not satisfy the needs of the clinician and the need for an objective but clinically applicable tool was identified. A clinical assessment may need to generate more than one 'value' and should include evaluation of other components of the upper motor neurone syndrome. There is therefore a need for standardized protocols for 'best practice' in application of spasticity measurement tools and scales.

Knee muscle activity during ambulation of trans-tibial amputees.

Gait analysis of trans-tibial amputees brings to light asymmetries of different gait parameters between the amputated and sound legs. The present study investigated the activity of the vastus medialis and biceps femoris muscles during ambulation of trans-tibial amputees. Peak activities of the vastus medialis were reached similarly in both legs (6.06+/-4.9% and 8.84+/-3.6% of gait cycle, in the sound and amputated leg, respectively). Biceps femoris peak activities were reached at 92.43+/-6.6% of gait cycle in the sound leg, and significantly later (at 9.81+/-4.8% of gait cycle) in the amputated leg (p < 0.05). Integrated EMG activity ratios, between swing and stance periods, were similar for the vastus medialis (0.33 in the sound and 0.35 in the amputated leg). However, these ratios differed significantly for the biceps femoris since the amputated leg presented a substantial (p < 0.05) smaller ratio (0.22) compared with the sound leg (0.83). The use of prosthesis in trans-tibial amputees requires further activity of the biceps femoris during stance period to improve support of the amputated leg knee joint.

Lower limb muscle activity in ambulatory children with cerebral palsy before and after the treatment with Botulinum toxin A.

Purpose: The study investigated the effect of Botulinum toxin A on the gait and lower limb muscle activity of ambulatory CP children. Methods: 19 spastic diplegic and 4 left hemiparetic CP children were injected with a mean dose of 23.5 units of Botulinum toxin A/kg body weight into the gastrocnemius and hamstring muscles. Muscle tone and gait analysis including the kinesiological electromyogram of the shank and thigh muscles were assessed before and four weeks after injection and compared with the help of a multivariate analysis (p < 0.05). Results: Botulinum toxin A caused a definite reduction of plantarflexor, knee and hip hypertonia in 21 children, resulting in a more plantar grade and erect gait in 17 children four weeks after injection. Gait analysis showed a statistically significant improvement in peak ankle dorsi-flexion and knee extension during stance, and the length of the force point of action under both feet increased. Electromyography revealed sig-nificantly less co-contraction of the lower leg muscles, due to a more phasic instead of a tonic activity of the tibialis anterior muscle, and an improved activation pattern of the left rectus and biceps femoris muscles. Conclusions: The present study demonstrated that the injection of Botulinum toxin A resulted in a more mature muscle activation pattern of CP children. Most of the children walked more plantigrade and erect, the functional gait parameters, however, did not change.

Suppression of flexor reflex by transcutaneous electrical nerve stimulation in spinal cord injured patients.

The effect of transcutaneous electrical nerve stimulation (TENS) applied to the area of the sural nerve on the early and late electromyographic component of the flexor reflex was studied in 20 patients with complete and incomplete transversal spinal cord injuries. A marked, progressive, and prolonged decrease of both reflex components was observed in most patients. The early component was decreased less than the late reflex component immediately following the end of TENS, while further decrement of both components was observed 30 min after the end of TENS. The placebo stimulation in 4 patients revealed no decrease, or only a less marked decrease in reflex responses. The marked suppressive effect of TENS cannot be attributed to the potentiated habituation of the reflex responses alone. The induced inhibitory processes seem to be at least partially localized at the segmental level of the spinal interneuron system.

Double-limb support and step-length asymmetry in below-knee amputees.

The sequence of gait events and symmetry of kinematic parameters between both lower limbs are compromised in below-knee amputees. In the present study the periods of double-limb support and the step length in below-knee amputees were investigated. The symmetry of the two periods of double-limb support occurring in each stride was obviously abnormal (ratio: 0.74) among temporal and distance parameters. The time of double-limb support (0.211 +/- 0.05 seconds) measured from heel-strike of the amputated leg until toe-off of the normal leg was significantly longer (p = 0.011) when compared with the contralateral leg (0.173 +/- 0.04 seconds). The step length of the normal leg (0.709 +/- 0.07 m) was significantly (p = 0.045) shorter than that of the amputated leg (0.752 +/- 0.08 m). Most of these differences between measured kinematic parameters can be explained by the limited ability of the prosthesis ankle-foot component to reproduce the normal functions of both foot and ankle.

Alterations in gait resulting from deliberate changes of arm-swing amplitude and phase.

OBJECTIVE: The purpose of the study was to reach a better understanding of the influence of arm movement in human gait. DESIGN: The experiment involved the adoption of different arm-swing patterns by normal subjects who walked in a gait laboratory. BACKGROUND: The reciprocal swinging of the arms in walking plays an important role in gait, but the details require further research. More insight into the role of the arm-swing in gait could be obtained by adopting different arm-swing patterns while walking at different speeds. METHOD: Thirteen normal subjects were therefore requested to walk adopting different arm-swing patterns which included, one or both arms strapped to the body, full reciprocal excursion of both arms, pace walking and swinging the arms in parallel. From measurements made at different speeds of walking, regressions were calculated which made it possible to compare basal gait characteristics of the different arm patterns. RESULTS: Maximum velocity decreased in all cases. In the test conditions where the arms were strapped, the subjects increased velocity by increasing stride frequency more than stride length. In the other conditions the reverse was the case. CONCLUSION: The experiments show that the gait pattern is very much influenced by changes in arm-swing but the effects are related to the pattern of arm-swing and the speed of walking.

Influence of speed on gait parameters and on symmetry in trans-tibial amputees.

Normal gait is characterised by a high level of inter-leg symmetry of gait parameters. Therefore, efforts in rehabilitation of amputees are directed at the construction of a prosthesis which provides normal leg function and allows a more symmetrical gait. Analysis of the gait of trans-tibial amputees was performed when they were ambulating at their own freely selected speed and at a faster speed. The effect of speed on selected gait parameters in each leg was evaluated and the influence on symmetry established by comparing the inter-leg changes for each of the selected parameters. The faster gait trail affected significantly all temporal and distance parameters in both legs but not the level of symmetry between legs. At the faster speed, the hip angles at heel-strike and during swing and the knee angle during load response, in the normal leg, and the knee angle during swing in the amputated leg, all increased significantly. Speed of gait significantly affected symmetry between knee angles as reflected by the increased differences measured during load response (from 2.62 +/- 5.2 to 7.06 +/- 4.2 degrees) and during toe-off (from 1.80 +/- 7.4 to 9.50 +/- 9.1 degrees). Timing and sequence of selected gait events, as related to stride time, were not significantly affected by speed of gait. These results might contribute to a better understanding of gait characteristics in trans-tibial amputees and provide design guidance for prosthetic components.

Stump length as related to atrophy and strength of the thigh muscles in trans-tibial amputees.

Stump length and the thigh muscles strength of the amputated limb are among the major factors influencing outcome of prosthetic rehabilitation of trans-tibial amputees. In the present study the authors evaluated and compared the strength of quadriceps and hamstrings muscles of both limbs in trans-tibial amputees, as measured by means of an electrical dynamometer. The obtained results showed that the thigh muscles of the sound limbs are significantly stronger than those of the amputated limbs (p < 0.01). The results obtained for amputees with shorter stumps were compared with those with longer stumps. In the group of amputees (n = 9) with a stump shorter than 15.1 cm, values of peak torque (in isokinetic contraction) and maximal average torque (in isometric contraction) were significantly (p < 0.5) weaker when compared to those (n = 9) with a stump longer than 15.1 cm. The results obtained for amputees with a higher rate of thigh muscle atrophy were compared to those with lesser atrophy. In the group of amputees where muscle atrophy was accompanied by decrease in thigh girth of over 5.9 cm, muscles strength did not significantly decrease (p < 0.5) as compared to amputees where thigh girth decrease was less than 5.9 cm. It is concluded that atrophy of the thigh muscles of trans-tibial amputees is accompanied with a significant decrease in strength. In amputees with a short stump, the short lever action provided by the stump interferes with the ability of the thigh muscles to control the prosthesis efficiently during daily activities such as standing and walking.

Ankle muscle activity before and after botulinum toxin therapy for lower limb extensor spasticity in chronic hemiparetic patients.

BACKGROUND AND PURPOSE: Recent studies have been made of the novel treatment of lower limb spasticity after stroke with botulinum toxin A, and the results were based mostly on the clinical assessment made before and after treatment. This study investigated the effects of toxin on ankle muscle activity during gait in patients with severe extensor spasticity. The questions posed were whether the toxin particularly diminishes the so-called premature muscle activity as a major cause of equinovarus deformity and whether different types of altered motor control allow a prediction of the outcome of the treatment. METHODS: In 12 chronic hemiparetic outpatients with pronounced lower limb spasticity, we injected 400 U botulinum toxin A into the soleus and tibialis posterior muscles and both heads of the gastrocnemius muscles. Ankle spasticity and complex gait analysis including kinematic electromyography (EMG) of the soleus and tibialis muscles were assessed before treatment and 4 weeks after the injection. RESULTS: Nine patients profited with a reduction of spasticity, improved gait ability, and a more normal temporal pattern of muscle activity with a prominent reduction of the premature activity of the plantar flexors. Eight patients exhibited a qualitative pattern (type I) corresponding to an increased stretch-reflex excitability. Three patients did not profit; their muscle tone, gait ability, and muscle activation remained stable or even deteriorated. CONCLUSIONS: This study further supports the beneficial effects of botulinum toxin in the treatment of lower limb extensor spasticity. A correlation was observed between the clinical reduction of muscle tone, functional gait parameters, and a more normal EMG pattern with a predominant reduction of the premature activity of the plantar flexors. The qualitative type of EMG pattern corresponding to an increased stretch-reflex excitability (type I) was a positive predictor for the outcome.

Effects of transcutaneous electrical nerve stimulation (TENS) on spasticity in patients with hemiplegia.

The effect of afferent cutaneous electrical stimulation on the spasticity of leg muscles was studied in 20 patients with chronic hemiplegia after stroke. Stimulation electrodes were placed over the sural nerve of the affected limb. The standard method of cutaneous stimulation, TENS with impulse frequency of 100 Hz, was applied. The tonus of the leg muscles was measured by means of an electrohydraulic measuring brace. The EMG stretch reflex activity of the tibialis anterior and triceps surae muscles was detected by surface electrodes and recorded simultaneously with the measured biomechanical parameters. In 18 out of 20 patients, a mild but statistically significant decrease in resistive torques at all frequencies of passive ankle movements was recorded following 20 min of TENS application. The decrease in resistive torque was often (but not always) accompanied by a decrease in reflex EMG activity. This effect of TENS persisted up to 45 min after the end of TENS. The results of the study support the hypothesis that TENS applied to the sural nerve may induce short-term post-stimulation inhibitory effects on the abnormally enhanced stretch reflex activity in spasticity of cerebral origin.

Botulinum toxin treatment for lower limb extensor spasticity in chronic hemiparetic patients.

Twelve chronic hemiparetic outpatients with pronounced lower limb extensor spasticity were injected with 400 units of botulinum toxin A, EMG guided into the soleus, tibialis posterior, and both heads of the gastrocnemius muscles. Botulinum toxin A caused a definite reduction of plantar flexor spasticity, in 10 patients two weeks after the injection, as assessed by the Ashworth scale. Four of the patients were able to achieve active dorsiflexion of their affected ankle. Gait analysis including the measurement of vertical ground reaction forces showed a statistically significant (p < 0.01) improvement in velocity, stride length, stance symmetry, and the length of the force point of action under the affected foot. Qualitative improvements on the force diagrams indicated a better loading, advancement of the body, and push off of the affected limb in seven patients. Eight weeks after the injection the effects waned.

Effects of electrical stimulation on muscles of children with Duchenne and Becker muscular dystrophy.

Twelve children with progressive muscular dystrophy (10 Duchenne and 2 Becker type) were included in a low-frequency electrical stimulation (LFES) program of the right tibialis anterior (TA) muscle for three months. Muscle strength was estimated by measuring torques in the ankle during short attempts of maximal voluntary isometric contraction (MVIC) in the direction of dorsal flexion of the foot. Muscle fatigue was assessed by the decrease of force during sustained (1-minute) voluntary contraction. The measurements were carried out before the beginning of the stimulation program and immediately after its conclusion. At the end of the stimulation program there were higher torques in 10 out of 12 children in the stimulated leg. The increase in torques in the stimulated leg was statistically significant (p < 0.01). Regarding the fatigue of the stimulated muscle there was no change after the conclusion of stimulation.

EMG monitoring of stimulating electrode position in implantation of subcutaneous peroneal stimulators.

Implantation of subcutaneous peroneal stimulators requires careful positioning to obtain a good response. With the patient lying down during the surgical procedure, ankle dorsal flexion was not always satisfactory during gait. Instead of dorsal flexion the stimulus could give an excessive eversion or a coactivation of ankle antagonists. To select the correct electrode position, the responses to single stimulation pulses were monitored in the tibialis anterior, peroneus longus and triceps surae muscles by surface EMG electrodes. With the patient standing, a strong contraction of the anterior tibial muscle without excessive contraction of the peroneus longus muscle was first determined by surface stimulation. The EMG responses were then recorded with the patient lying in the position required for implantation. The records were used as a guideline during surgery, during which positioning of the electrodes was monitored by the EMG responses. The method, tested on 2 healthy adults and 13 patients, resulted in reliable positioning of the stimulating electrodes.

Rigidity in parkinsonism: characteristics and influences of passive exercise and electrical nerve stimulation.

Rigidity was measured during sinusoidal passive movements of the ankle joint in 7 patients with parkinsonism. Velocity-dependent changes were observed, less marked than in spasticity and expressed in a different way in flexor and extensor muscles: a mild decrease in resistive torques at faster stretching of dorsal flexors and an increase in resistance on stretching of plantar flexors. Dorsal flexors also frequently showed shortening reactions. Passive exercises and electrical stimulation of the peroneal nerve resulted in decreased electromyographic responses to stretch, smoother passive movements and in improved voluntary contraction.

Electrical stimulation in treating spasticity resulting from spinal cord injury.

To study the efficacy of electrical stimulation in treating spasticity of six spinal cord injured patients, transcutaneous electrical nerve stimulation (TENS) was applied to the dermatomes belonging to the same spinal cord level as the selected spastic muscle group. Spasticity was assessed in knee extensors by a pendulum test in which the knee joint angle of a swinging lower leg was recorded with an electrogoniometer. TENS was found to produce a noticeable decrease of spasticity in three of the patients, but had little effect on the others.

Postural control in scoliosis. A statokinesimetric study in patients with scoliosis due to neuromuscular disorders and in patients with idiopathic scoliosis.

Statokinesimetric characteristics were analysed in patients with scoliosis which had developed in the course of degenerative neuromuscular disorders and in patients with adolescent idiopathic scoliosis. Patients with Duchenne and limb- girdle muscular dystrophy and spinal muscular atrophy showed markedly decreased oscillations of the body's centre of gravity, in addition to a forward shift of its mean position. Thus the postural equilibrium in neuromuscular patients with scoliosis is even more efficiently controlled than normal. On the other hand, patients with idiopathic scoliosis did not show any significant changes as compared with normal subjects. The present study therefore does not support the suggestion that the pathogenesis of scoliosis, at least in neuromuscular patients, is triggered by an impairment of descending postural control.

Reflex responses of paraspinal muscles to tapping.

ERECTOR SPINAE REFLEX STUDIES IN HEALTHY SUBJECTS REVEALED TWO RESPONSES: a 12·0±1·6 ms latency, oligosynaptic response, and a 30 to 50 ms latency response with polysynaptic reflex characteristics. There was a silent period after the first and second responses. The effect of limb position, trunk, neck, postural changes, Jendrassik manoeuvre and vibration on both responses were also evaluated.