Single Sessions of High-Definition Transcranial Direct Current Stimulation Do Not Alter Lower Extremity Biomechanical or Corticomotor Response Variables Post-stroke

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique used to modulate cortical activity. However, measured effects on clinically relevant assessments have been inconsistent, possibly due to the non-focal dispersion of current from traditional two electrode configurations. High-definition (HD)-tDCS uses a small array of electrodes (N = 5) to improve targeted current delivery. The purpose of this study was to determine the effects of a single session of anodal and cathodal HD-tDCS on gait kinematics and kinetics and the corticomotor response to transcranial magnetic stimulation (TMS) in individuals post-stroke. We hypothesized that ipsilesional anodal stimulation would increase the corticomotor response to TMS leading to beneficial changes in gait. Eighteen participants post-stroke (average age: 64.8 years, SD: 12.5; average months post-stroke: 54, SD: 42; average lower extremity Fugl-Meyer score: 26, SD: 6) underwent biomechanical and corticomotor response testing on three separate occasions prior to and after HD-tDCS stimulation. In a randomized order, anodal, cathodal, and sham HD-tDCS were applied to the ipsilesional motor cortex for 20 min while participants pedaled on a recumbent cycle ergometer. Gait kinetic and kinematic data were collected while walking on an instrumented split-belt treadmill with motion capture. The corticomotor response of the paretic and non-paretic tibialis anterior (TA) muscles were measured using neuronavigated TMS. Repeated measures ANOVAs using within-subject factors of time point (pre, post) and stimulation type (sham, anodal, cathodal) were used to compare effects of HD-tDCS stimulation on measured variables. HD-tDCS had no effect on over ground walking speed (P > 0.41), or kinematic variables (P > 0.54). The corticomotor responses of the TA muscles were also unaffected by HD-tDCS (resting motor threshold, P = 0.15; motor evoked potential (MEP) amplitude, P = 0.25; MEP normalized latency, P = 0.66). A single session of anodal or cathodal HD-tDCS delivered to a standardized ipsilesional area of the motor cortex does not appear to alter gait kinematics or corticomotor response post-stroke. Repeated sessions and individualized delivery of HD-tDCS may be required to induce beneficial plastic effects. Contralesional stimulation should also be investigated due to the altered interactions between the cerebral hemispheres post-stroke

Cannabis use in people with Multiple Sclerosis: the highway to lower disability?

2017 Fall.Includes bibliographical references.The following dissertation describes a series of investigations designed to identify possible effects of cannabis use in people with Multiple Sclerosis. The specific aims of the three projects were: 1) to determine the proportion of people with Parkinson's Disease and Multiple Sclerosis currently using cannabis and collect self-reported measures of disability, to include physical function, balance, and fatigue; 2) to determine if people with Multiple Sclerosis using cannabis perform better on functional tasks compared to individuals who are not using cannabis; 3) to determine if resting brain glucose uptake is altered in people with Multiple Sclerosis using cannabis compared to people not using cannabis. In Project 1 we found that a large portion of people with Parkinson's disease and Multiple Sclerosis responding to our survey are currently using cannabis. These individuals are also reporting lower levels of neurological disability, especially within the realms of mood, memory, and fatigue. A large majority of participants also reported reducing the amount of prescription medications since starting cannabis use. In project 2 we compared objective and subjective measurements of neurological disability between current cannabis users and data taken from a previous investigation investigating predictors/correlates of physical activity in people with Multiple Sclerosis. When we compared the users versus the non-users we found that users reported higher levels of fatigue as assessed by the fatigue severity scale questionnaire. We also found that people with Multiple Sclerosis using cannabis performed worse on the Paced Auditory Serial Addition Test, which is a measure of cognitive function. Project 3 utilized Positron Emission Tomography to measure brain glucose uptake with the glucose analog tracer [18F]-Fluorodeoxyglucose. Higher levels of glucose uptake were beneficially correlated with disability status, fatigue, and pain in our sample. These findings agree with previous studies and indicated that brain glucose uptake can be used as a biomarker in people with multiple sclerosis. When our sample was dichotomized into current cannabis users and non-users measures of disability were similar, except that cannabis users performed more poorly during cognitive function testing. Even though most measures of disability were similar between the groups, cannabis users were found to have greater glucose uptake throughout areas of the frontal and temporal lobes. This suggests that cannabis may provide beneficial effects in maintaining nervous system glucose uptake but may also be accompanied by negative effects on cognition in people with multiple sclerosis