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This study attempted to determine changes in motor unit discharge patterns, characterized by serial correlation coefficients (SCC) and fractional parameters during a functional recovery in stroke patients. Using the surface electrode technique, 171 single motor units were recorded from bilateral upper extremities of 23 stroke patients and 7 normal volunteers. SCCs and fractional parameters were calculated and correlated with Rasch-converted Functional Independence Measurement (FIM) scores by linear regression analysis. No statistically significant correlation was found between FIM scores and SCCs and between FIM scores and fractional parameters recorded during first four weeks post stroke. Only FIM for total motor scores and FIM for locomotion subscore significantly correlated with SCC recorded after 4 weeks post stroke (p < 0.05). Predictive power (R2) of SCC for FIM scores did not change much over time. Fractional parameters, recorded after 4 weeks post stroke, had significant correlation with FIM for total motor scores and all FIM subscores except FIM for sphincter control subscores. Predictive values of fractional parameters for FIM scores was better after 6 months post stroke. There was a better correlation between fractional parameters with FIM scores and a better predictive value of fractional parameters for FIM scores over functional recovery period. This change in the correlation during the course of stroke recovery may indicate that fractional parameters could reflect a more stabilized motor control stage rather than a less stabilized motor functional stage.

Background: We have previously demonstrated that the fractional parameter has significant correlation with the muscle strength of patients with stroke. In this study, we have investigated whether fractional parameter can be used to objectively document stroke patients' functional level (using FIM scores)., Methods: Sixty motor units were recorded in abductor pollicis brevis, first dorsal interosseous, and abductor digiti minimi muscles in 18 stroke patients. Patients' FIM scores, obtained fractional parameters, and serial correlation coefficients were analyzed and statistical determination was made., Results: Statistical significance was found between fractional parameters and motor items of FIMs (except selfcare category); no statistical significant correlation was found between SSC and FIM scores., Conclusion: Fractional parameter could be a useful tool for measuring motor function at a single motor unit level.

We have developed a comprehensive technique to identify single motor unit (SMU) potentials and to decompose overlapped electromyographic (EMG) signals into their constituent SMU potentials. This technique is based on one-channel EMG recordings and is easily implemented for many clinical EMG tests. There are several distinct features of our technique: 1) it measures waveform similarity of SMU potentials in the wavelet domain, which gives this technique significant advantages over other techniques; 2) it classifies spikes based on the nearest neighboring algorithm, which is less sensitive to waveform variation; 3) it can effectively separate compound potentials based on a maximum signal energy deduction algorithm, which is fast and relatively reliable; and 4) it also utilizes the information on discharge regularities of SMU's to help correct possible decomposition errors. The performance of this technique has been evaluated by using simulated EMG signals composed of up to eight different discharging SMU's corrupted with white noise, and also by using real EMG signals recorded at levels up to 50% maximum voluntary contraction. We believe that it is a very useful technique to study SMU discharge patterns and recruitment of motor units in patients with neuromuscular disorders in clinical EMG laboratories.

We studied 60 motor units from abductor pollicis brevis, first dorsal interosseous, and abductor digiti minimus muscles in 18 patients with upper motor neuron lesions. Both fractional process parameters and serial correlation coefficients were estimated. The results suggest that both serial correlation coefficients and fractional process parameters can be used to objectively document upper motor neuron disorders in stroke patients. However, each of them may be more sensitive to distinct central motor regulatory mechanisms.

Current techniques for motor unit number estimation (MUNE) rely on the amplitude of the compound muscle action potential (CMAP) evoked by supramaximal stimulation and mean amplitude of single motor unit potentials (SMUPs). The phase cancellation during summation is not considered. We developed a technique to address this issue. Slow and fast types of motor unit potentials were collected from 5 normal subjects from their abductor pollicis brevis muscles by low-level voluntary contractions, and near-threshold nerve stimulation, respectively. Two of each type of SMUPs were used as templates for reconstructing the best fitted CMAP using a feed-forward neural network. The total number of SMUPs simulated from the four templates during the reconstruction served as MUNE. The mean MUNE was 222 +/- 98. The technique is simple and noninvasive, and may be applied in the future for MUNE in patients.

We developed a technique to study temporal discharge patterns of single motor units using 1/f process model, whose fractional parameter gamma was shown to be a useful indicator for distinguishing between discharge behaviors of single motor units of normal subjects and patients with upper motor neuron lesions. We have studied a total of 47 motor units in 3 normal subjects, and 41 in 3 patients with upper motor neuron lesions from biceps and extensor digitorum communis muscles during steady contraction. The parameter gamma was estimated with an algorithm based on wavelet analysis. The mean value of gamma in patients was 1.52, and the mean value of gamma in normal subjects was -0.06. These results suggest that 1/f process can be used to document the impaired motor control mechanisms at single motor unit level.

A new method for estimating the number of motor units using a surface EMG triggered averaging technique is described. This method provides an estimation of mean motor unit potential (MUP) amplitude at different levels of contraction, which can be utilized to estimate the number of motor units in a given muscle. Motor unit count estimated in abductor pollicis brevis (APB) muscle of 11 normal healthy subjects ranged from 131 to 371 with a mean of 246 +/- 68. In our preliminary study of patients with lower motor neuron lesions, there was a significant reduction in the number of motor units. We believe our new noninvasive method of motor unit counting is a relatively simple and reproducible physiological technique.

We studied the discharge pattern of single motor units (SMUs) in the left and right biceps muscles from a patient with nonspastic weakness of the left arm. Detailed statistical analysis of the behavior of discharge patterns of 4 of 4 single motor units on the affected side showed abnormalities with characteristic features of an upper motor neuron lesion. Five out of 5 single motor units recorded from the right biceps were normal. An upper motor neuron lesion affecting the left arm, predicted by our results, was confirmed by magnetic resonance imaging (MRI), which showed a lesion in the right precentral gyrus. It appears that changes in single motor unit firing characteristics, caused by an upper motor neuron lesion, can be detected at a time when there is no evidence of increased "tone" and/or hyperreflexia (spasticity) in the affected extremity.

We stimulated the cervical region with a 9-cm-diameter magnetic coil on centered on the spinous processes in 21 normal subjects. We obtained maximal amplitudes with clockwise coil current in right-sided upper extremity muscles and counterclockwise coil current in left-sided upper extremity muscles. Optimal stimulation sites for biceps, triceps, and abductor digiti minimi were C-3 or C-4, C-4 or C-5, and C-4, C-5, or C-6, respectively. The latencies of the muscle responses varied little in the same subject in spite of marked amplitude changes due to suboptimal position of the coil or submaximal stimulator output. In abductor digiti minimi, the amplitude of the muscle response on cervical magnetic stimulation was 9 to 100% of the supramaximal amplitude on wrist electrical stimulation. We established normal values for latency, amplitude, and interside differences for the above 3 upper extremity muscles. The findings were reproducible, and the latencies obtained with large coils from different manufacturers in the same subjects were comparable. We found no advantage in bipolar recording over tendon-belly montage. Comparison of magnetic and electrical needle root stimulation in the same subjects showed that the magnetic stimulus was more proximal in biceps and triceps, and that the site of excitation was approximately the same in abductor digiti minimi. Indirect assessment of the longitudinal site of excitation based on F-wave minimal latency indicated that excitation occurred within millimeters of the emergence of axon of the peripheral motor neuron.

Physiological and biochemical studies were carried out on 16 patients with motor neurone disease (MND). It was confirmed that the peripheral nerves in cases of MND are often unusually resistant to ischaemia especially as regards the large sensory fibres. Biochemical investigations demonstrated a tendency to carbohydrate intolerance and abnormal pyruvate metabolism. When compared with other related studies in MND it seems very likely that there is a metabolic abnormality present in MND which demands further study.

The usefulness of performing late response studies for the detection of peripheral nerve dysfunction has been demonstrated. It has been shown that significant prolongation of the minimal latencies of the H reflex and the F response is present at a time when conventional methods of motor and sensory conduction do not show an abnormality in individual patients. Abnormalities of late responses have been shown to occur in a variety of peripheral neuropathies with "axonal" as well as "segmental demyelination" type of underlying pathology. [ABSTRACT FROM AUTHOR]