Patients with spastic hemiplegia at different recovery stages: evidence of reciprocal modulation of early/late reflex responses

Differences in F-Wave Characteristics between Spinobulbar Muscular Atrophy and Amyotrophic Lateral Sclerosis

There is limited data on the differences in F-wave characteristics between spinobulbar muscular atrophy (SBMA) and lower motor neuron dominant (LMND) amyotrophic lateral sclerosis (ALS). We compared the parameters of F-waves recorded bilaterally from the median, ulnar, tibial, and deep peroneal nerves in 32 SBMA patients, 37 patients with LMND ALS, and 30 normal controls. The maximum F-wave amplitudes, frequencies of giant F-waves, and frequencies of patients with giant F-waves in all nerves examined were significantly higher in the SBMA patients than in the ALS patients and the normal controls. The mean F-wave amplitude, maximum F-wave amplitude, frequency of giant F-waves, and frequency of patients with giant F-waves in the median and deep peroneal nerves were comparable between the ALS patients and normal controls. Giant F-waves were detected in multiple nerves and were often symmetrical in the SBMA patients compared with the ALS patients. The number of nerves with giant F-waves seems to be the most robust variable for differentiation of SBMA from ALS, with an area under the curve of 0.908 (95% CI: 0.835–0.982). A cut-off value of the number of nerves with giant F-waves (≥3) for diagnosing SBMA showed high sensitivity and specificity: 85% sensitivity and 81% specificity vs. ALS patients. No significant correlations were found between the pooled frequency of giant F-waves and disease duration in the SBMA (r = 0.162, P = 0.418) or ALS groups (r = 0.107, P = 0.529). Our findings suggested that F-waves might be used to discriminate SBMA from ALS, even at early stages of disease.

Reliability of elbow stretch reflex assessment in chronic post-stroke hemiparesis

OBJECTIVE

To establish reliability of quantitative measures of elbow joint spastic hypertonia in post-stroke hemiparesis.

METHODS

Nine subjects with post-stroke hemiparesis (mn duration: 42 months) were tested on three separate days. Biceps brachii and brachioradialis EMG were recorded during passive ramp-and-hold extensions applied at seven speeds between 30 and 210 degrees /s. EMG burst duration, onset position threshold, and burst intensity were used to evaluate reflex activity. Torque at 40 degrees of elbow flexion was used as a mechanical indicator of spastic hypertonia.

RESULTS

Across speeds ICCs were consistent, means ranged between 0.63 and 0.85. Thus, relative reliability was fair to excellent for all parameters. Absolute reliability, determined using standard error of measurement expressed as a percentage of the mean score (%SEM), improved at higher speeds (> or = 120 degrees/s).

CONCLUSIONS

These results establish reliability of reflex and mechanical measures of elbow spastic hypertonia post-stroke. The data demonstrate greater reflex detection at high speeds, indicating greater potential to document meaningful changes in these distinct aspects of spastic hypertonia following intervention.

SIGNIFICANCE

Based on findings of this study, reliability was demonstrated using four parameters of reflex EMG and torque indicating measurement consistency across sessions. These observations motivate determination of requisite effect sizes for clinical trials that evaluate treatment outcome.

Reflex contribution of spindle group Ia and II afferent input to leg muscle spasticity as revealed by tendon vibration in hemiparesis

OBJECTIVE

Foot dorsiflexion evokes a short- (SLR) and a medium-latency EMG response (MLR) in the soleus of standing subjects. SLR is mediated by spindle group Ia, while group II fibres contribute to MLR through an oligosynaptic circuit. We studied the effects of Achilles' tendon vibration on both responses in spastic patients to disclose any abnormal excitability of these pathways.

METHODS

SLR and MLR were evoked in 11 hemiparetics and 11 normals. The vibration-induced changes in both responses were correlated to the Ashworth score of the affected leg.

RESULTS

There were no differences between normals and patients in the size of control SLR or MLR. Vibration decreased SLR to 70% in normal subjects, but increased it to 110% in patients, in both affected and unaffected leg. Vibration did not affect MLR in normals, but increased it to 165% on the affected and 120% on the unaffected side of patients. Ashworth score was solely correlated with the degree of vibration-induced increase of MLR.

CONCLUSIONS

While the lack of inhibitory effect of vibration on SLR confirms a reduced inhibitibility of the monosynaptic reflex, the increased MLR indicates a disinhibition of group II pathway in patients, connected to the loss of descending control on group II interneurones. Spastic hypertonia depends on release of group II rather than group Ia reflex pathways.

SIGNIFICANCE

These findings give a neurophysiological support for the pharmacological treatment of spastic hypertonia and suggest a method for the assessment of its effects.

Clinical utility of botulinum toxin in the treatment of cerebral palsy: comprehensive review

The physical properties, mechanism of action, and clinical evidence supporting the use of botulinum toxin in the management of spasticity in cerebral palsy are discussed. Assessment methods, patient selection criteria, and methodology for preparation and administration of botulinum toxin are discussed in detail and a treatment algorithm based on the cumulative experience of the author is provided. Botulinum toxin type A is well tolerated, safe, and effective in the treatment of patients with spastic cerebral palsy. Appropriate patient selection is imperative. Treatment goals need to be well defined and tailored to the individual patient's needs. Growth and development is a continuous and evolving process, necessitating the constant reassessment of the patient and modification of future treatment goals. The ultimate success of management in cerebral palsy is dependent on the development of a comprehensive spasticity team with complementing skills who, together, can significantly improve the quality of life of these patients.

Long latency responses in pure sensory stroke due to thalamic infarction

OBJECTIVES

Our study was designed to clarify the role of the thalamus in the generation of the electrically elicited long-latency reflexes (LLR) in voluntarily activated hand muscles.

MATERIALS AND METHODS

EMG responses of the thenar muscles were evoked by electrical stimulation of the median nerve at the wrist at motor threshold intensity in 10 patients with acute pure sensory stroke due to thalamic infarction. Concomitant recording of somatosensory evoked potentials (SEPs) was performed. The subjects were asked to steadily abduct the thumb at 20-30% of maximal force against a force transducer. Rectified and averaged EMG activities were recorded.

RESULTS

The LLR II was missing completely or significantly attenuated in the majority of the patients (9 of 10), of whom 3 also had delayed latency. Abnormal SEPs were documented in 7 patients (7 of 10). In the follow-up, 5 patients had partial reversal of LLR II. LLR II was still pathological in 1 fully recovered patient.

CONCLUSION

Our results further confirm the transcortical generation of LLR II and imply that a thalamic relay is present in the afferent limb of the LLR.

Giant repeater F-wave in patients with anterior horn cell disorders. Role of motor unit size

Conventional F-wave responses as well as single motor unit F-wave responses together with the volitionally recruited motor unit action potentials (MUAP) were studied in hand and feet muscles of 10 healthy subjects and 32 patients with anterior horn cell disorders. The amplitude of the largest F-wave (Fl) was significantly greater in the affected patients compared with healthy subjects. Giant repeater F-wave responses "up to 4 mV" were recorded in muscles having volitionally recruited giant MUAPs. Although, the group mean percentage of motor unit F-wave responses per stimulation in all tested orthodromic MUAPs was significantly decreased in amyotrophic lateral sclerosis patients, the group mean percentage of motor unit F-wave responses per stimulation in all tested orthodromic MUAPs that gave motor unit F-wave response was significantly increased compared with healthy subjects. The responding orthodromic MUAP gave identical motor unit F-wave response, even for complex polyphasic units. Enhanced monosynaptic (H-) reflex, proximal axon reflex (A-wave), and repetitive muscle response as possible explanations for the giant F-wave responses could be discounted. The electrophysiologic behavior of the giant late responses described here fits well with the criteria of F-waves modulated by newly formed distal (and or proximal) axonal branching.