Anodal tDCS of the lower limb M1 does not acutely affect clinical blood pressure and heart rate in healthy and post stroke individuals

  • Madhavan S
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Abstract

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique increasingly investigated an adjunct modality to enhance the effects of motor therapy. Although the safety of tDCS in relation to cognition, sensation and perception has been well reviewed, there still exists limited information regarding its effects on blood pressure and heart rate. As tDCS is being largely used in conjunction with stroke rehabilitation, it is important that we understand the effects of tDCS on autonomic function in the stroke population. In this retrospective study, we examined the acute effects of tDCS of the lower limb motor cortex in healthy and post stroke individuals using clinical measurements of blood pressure and heart rate. Fifteen minutes of 1 mA anodal tDCS did not cause any clinically detectable changes in blood pressure or heart rate. This is the first study to report the cardiovascular autonomic effects of tDCS of the lower limb M1 in healthy and post stroke individuals. Further studies are needed to examine if these safety effects are preserved during repeated applications of tDCS. always feasible or time-saving to monitor patients using ECG especially when delivering tDCS in the outpatient clinic or at home. In addition, to the best of our knowledge, there is no information yet on the effects of tDCS on autonomic function in stroke survivors. Since autonomic function is compromised in individuals post stroke and as tDCS is being increasingly used for stroke rehabilitation [10], it is important to clarify its effects on cardiovascular function in stroke. Also, as most tDCS studies focus on the upper limb motor cortex (M1) or pre frontal areas, autonomic effects of tDCS of the lower limb M1 in healthy individuals or patients has never been examined. This is important to study due to basic differences between the upper and lower extremities in anatomical location of motor maps, differences in sensorimotor organization and differences in motor task performances (lack of fine control and more automated movement for the lower limb) which may result in a differential response of tDCS. Hence in this study we examined the effects of tDCS of the lower limb M1 on cardiovascular autonomic function using clinically used measurements such as heart rate and blood pressure in healthy and stroke participants. Methods This post hoc analyses combined data from four different studies from our laboratory with similar tDCS parameters. Data from 31 young healthy adults (15 females, 16 males; age range 20 – 34 years) and 19 individuals with stroke (8 females, 11 males; 50 – 75 years) were included. Stroke participants' who had only one stroke with no other significant medical conditions, and well managed hypertension were recruited. Healthy participants with no history of neurological, cardiovascular or other metabolic conditions participated. All research methods were approved by University of Illinois' Institutional Review Board. tDCS tDCS was administered using a constant current stimulator (Chattanooga Ionto Iontophoresis System, TN) for 15 minutes at 1 mA. The active electrode (5 cm x 2.5 cm) saline-soaked sponge electrode was placed on the motor hot-spot (determined using transcranial magnetic stimulation) of the non-dominant/affected

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Madhavan, S. (2016). Anodal tDCS of the lower limb M1 does not acutely affect clinical blood pressure and heart rate in healthy and post stroke individuals. SOJ Neurology, 2(2), 01–03. https://doi.org/10.15226/2374-6858/2/2/00118

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