The least investigated issue in polymorphism of motor control impairment in stroke population is spasticity. Along with the theory of corticospinal dissociation, the role of reorganization of ipsilateral cortical motor networks is represented among the modern data and as a result of the development of hyperexcitability of reticulo- and vestibulospinal tracts, the role of the corticospinal tract in the development of spinal hyperexcitability still remains poorly understood. The aim of the study was to conduct the analysis of the effect of the degree of impairment of corticospinal innervation on the development of spinal hyperexciatability in patients after hemispheric ischemic stroke. In the study the results of the examination of 21 patients diagnosed with chronical ischemia of I-II stages without any neurological deficiency and 63 patients with the consequences of ischemic stroke with cortical localization and various degrees of neurological deficiency have been described. As a result of the research carried out by the method of transcranial magnetic stimulation, three types of pathophysiological reactions have been found depending on the state of corticospinal innervation, which resulted in the distribution of patients into three groups. Among the patients of the first group, the reduction of the conducting function (the time of motor conduction) to 12.3 % as well as the reduction of excitability of the primary motor cortex up to 17.4 % (according to the threshold of excitation) have been established. At the same time, CMEP amplitude among patients of the first group has been reduced to 35 % as compared with patients of the control group (CG). When comparing the amplitudes of SMEP, a significant increase of up to 80 % has been established which indicates the expressive hypersensitivity of the spinomotoneuronal pool. Thus, a moderate decrease in corticospinal innervation has been accompanied by a marked increase in segmental motor excitiability. Among patients of the second RG, the conductive function has reduced to 63 % (according to the time of the motor conduction), the reduction of the excitability of the primary motor cortex up to 63.8 % (according to the inactive threshold). In the evaluation of the amplitude of CMEP, a decrease of up to 96 % and a decrease in the amplitude of CMEP up to 14 % as compared with the CG have been observed. The results of the comparative analysis allowed us to come to the conclusion that there was no spinal hyperpexcitability among patients with the impairment of gross corticospinal innervation. While comparing the results of the examination of patients of the third control group with the control one, in the absence of CMEP including the sample with facilitation, the amplitude of the CMEP has increased to 182 %. In the process of the comparative analysis, it has been found out that among patients of the third RG in the absence of CMEP, the amplitude of segmental innervation has exceeded twice the amplitude among patients of CG, indicating a distinct spinal hyperexcitiability. As a result of the study, it can be concluded that only a complete impairment of corticospinal innervation is always accompanied by the development of spinal hyper-excitability. It does not have a direct correlation with the degree of the impairment of corticospinal innervation with the development of segmental hyper-excitability. After examining the indicators of cortisospinal innervation of the affected hemisphere and the contralateral segments of the spinal cord, one can fail to notice that the pathophysiological basis of the development of the segmental hyper-excitability syndrome is the complex mechanism of the reorganization of the ipsilateral neural networks of the cerebral cortex. Recieved: 12.10.2018
Keywords: stroke, transcranial magnetic stimulation, spinal hyper-excitability, corticospinal tract, spasticity
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