Differences in Rheobase and Chronaxie between the Paretic and Non-Paretic Sides of Hemiplegic Stroke Patients: a Pilot Study

Abstract

[Purpose] Rheobase and chronaxie are used to confirm muscle degeneration. For stroke patients, however, the uses of rheobase and chronaxie in determining paretic side muscle degeneration is not yet fully understood. Thus, in this study, we examined the electrical properties of the quadriceps muscles of stroke patients' paretic side and compared them with their respective values on the non-paretic side. [Method] The subjects were six stroke patients (three females, three males). The pad of an electrical stimulator was applied to the vastus lateralis and vastus medialis regions to measure rheobase and chronaxie until the contractive muscle response to electrical stimulation became visible. [Result] Rheobase was significantly increased on the paretic side compared to that of the non-paretic side of hemiplegic stroke patients. Furthermore, chronaxie was significantly increased on the paretic side compared to the non-paretic side of hemiplegic stroke patients. [Conclusion] These results suggest that stroke affects the sensitivity of skeletal muscle contraction. Therefore, this data may contribute to our understanding of the muscle status of stroke patients.

Keywords: Chronaxie; Hemiplegic stroke patients; Rheobase.

Fig. 1.

Schematic representation of the measurements of rheobase and chronaxie In the analysis of rheobase and chronaxie, the thigh (parts of the vastus lateralis and vastus medialis) was stimulated using an electrical stimulator and two surface electrodes of the same size for bipolar stimulation. Rheobase and chronaxie were measured using monofilaments, as described in the Materials and Methods. +, anode; -, cathode; →, region of stimulation of the anterior parts of thigh; PS, paretic side of stroke patients; NS, non-paretic side of stroke patients; ES, electrical stimulation; MP, motor point; S-D Curve, strength-duration curve.