Background
It is generally accepted that upper motor neuron (UMN) lesion can alter lower motor neuron (LMN) functionby the plasticity of neural circuit. However there have been only few researches regarding the axonal excitability of LMNafter UMN injury especially during the acute stage. The aim of this study was to investigate the nerve excitability propertiesof the LMNs following an acute to subacute supratentorial corticospinal tract lesion. Methods: An automated nerve excitabilitytest (NET) using the threshold tracking technique was utilized to measure multiple excitability indices in median motoraxons of 15 stroke patients and 20 controls. Testing of both paretic and non-paretic side was repeated twice, during theacute stage and subacute stage. The protocols calculated the strength-duration time constant from the duration?릀harge curve,parameters of threshold electrotonus (TE), the current-threshold relationship from sequential sub-threshold current, and therecovery cycle from sequential supra-threshold stimulation. Results: On the paretic side, compared with the control group,significant decline of superexcitablity and increase in the relative refractory period were observed during the subacute stageof stroke. Additionally, despite the absence of statistical significance, a mildly collapsing in (
