The generally accepted theory of pathophysiological mechanisms for the development of spastic syndrome and pathological synergies is the disinhibition of spinal stretch reflexes and abnormal intraspinal processing, secondary to the loss of supra-segmental control. The role of primary motor cortex in the development of spastic syndrome in humans remains poorly understood.

The aim of the study was to analyze the interdependence between the loss of excitability of the primary motor cortex of the affected hemisphere after the stroke with the development of segmental hyperexcitability of the spinal cord.

Using electroneuromyography and transcranial magnetic stimulation (TMS), we examined a cortical (cMEP) and segmental (sMEP) evoked motor potentials in 60 patients divided into 2 groups: the main group consisted of 30 patients with subacute ischemic stroke, the control group consisted of 30 patients with chronic cerebral ischemia of I-II stage.

It was established that among patients in the control group when comparing the averaged TMS of the right and left hemispheres, and segmental innervation of the left and right sides at the level of the neck segments, there were no statistically significant differences. Since all patients were right-handed for neurophysiological analysis, the averaged TMS of the left hemisphere and contralateral segments of the spinal cord (right) were taken. In the statistical analysis of data of TMS of the affected hemisphere among the patients of the main group with the data of the control group, there were significant differences in the form of increase in latency to 13%, a decrease in the amplitude of the cMEP to 68.5%, an increase in duration to 30.8%, a decrease in the area to 52% and an increase in the time of the central motor carriage to 27%. Lowering the cMEP amplitude by more than 50%, increasing the motor holding time by 2 m/s or more, indicates a marked interruption of corticospinal innervation. The study of interdependence among the patients in the control group, between the cMEP amplitudes and the sMEP showed a high correlation between the scores - rs = 0.73. At the same time, in the study of the degree of correlation of the amplitude of cMEP and sMEP, among the patients in the control group, a low level was set - rs = 0.21.

In analyzing the parameters of segmental innervation in the main group, the absence of a statistically significant difference in the group was determined contralaterally and ipsilaterally to the affected hemisphere. The study of indicators compared with the control group showed statistically significant deviations of all results.

Comparing the results of segmental innervation of the contralateral side to the affected hemisphere of the main group and the right side of the control group, an increase in sMEP has been set to 21%, latency to 6%, an increase in duration to 22. At the same time, in the deviation of the amplitude of the sMEP below 50%, we can not conclude significant hyperexcitability.

The examined patients after a hemisphere ischemic stroke have a evident decrease in the excitability of the primary motor cortex in all of the parameters that was studied. A study of the state of the segmental apparatus of the spinal cord showed a two-side increase in latency, amplitude and duration. Nevetheless, the change in the amplitude of the sMEP was small in character, which may be due to the variability of the degree of excitability of the primary motor cortex among the patients in the main group, which needs further research.

On the basis of the obtained results, it can be concluded that the interruption of cortisospinal innervation has an indirect correlation (rs=0,21) with the development of segmental hyperexciatability.

Recieved: 05.03.2018

Ключові слова: transcranial magnetic stimulation, ischemic stroke, spinal excitability, spasticity, pathologic synergies

Повний текст: PDF (Ukr)

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