Spinal transcutaneous direct current stimulation to enhance locomotor training after spinal cord injury Radha Korupolu, MBBS, MS (pgy2) Physical Medicine & Rehabilitation University of Kentucky Mentor: Lumy Sawaki, MD, PhD Collaborator: Kenneth Chelette, MS University of Kentucky & Cardinal Hill Rehabilitation Hospital

Background Transcranial direct current stimulation Modulates cortical excitability Anodal stimulation increases neuronal firing rate Cathode stimulation decreases neuronal firing rate Effects may last for >1 hr after stimulation Inexpensive Non-invasive Nitsche et al., 2008; Nitsche et al., 2003; Priori, 2003

Transcranial direct current stimulation (tDCS) Possible Mechanism: Changes the resting membrane potential of the neurons in cortex Adjuvant treatment options for pts suffering from Stroke Chronic pain Depression Cognitive deficits Hummel et al., 2005;Fregni et al., 2006a,b

Transcutaneous spinal direct current stimulation (tsDCS) Preliminary studies in healthy subjects Suggest possibility of similar modulation in spinal neurons

F. Cogiamanian et al. (2008) Sample size : Intervention: 12 healthy subjects Intervention: tsDCS over T10 spinous process 2.5 mA for 15 mins anodal or cathodal Outcome Measures: Post. Tibial N & Median N SEPs were recorded Before, at current offset & 20 min after tcDCS (anodal/ cathodal DC) PF, L1, C6, U3, RE lobe

F. Cogiamanian et al. (2008) Results Anodal tcDCS decreased PTN SEPs amp by 25% Effect lasted at least 20 min Serum neurone specific enolase (NSE), a marker of neuronal damage NSE level before & 1 h after stimulation measured in 5 subjects was not elevated after tsDCS

T. Winkler et al. (2010) Sample size : Intervention: 10 healthy subjects Intervention: tcDCS at T11 level 2 cm paravertebrally 2.5 mA applied for 15 min Cathodal, anodal or sham Each subject received all modes of stim 1 week apart

T. Winkler et al. (2010) Outcome measures: Results H-reflex Before, at current offset, & 15 min after anodal, cathodal or sham tsDCS. Results Anodal tsDCS: Down-regulated spinal excitability Cathodal tsDCS: Up-regulated spinal excitability

Our research plan Aim to study effects of tsDCS in 3 phases Proposed objectives for the first phase: Establish a reliable & reproducible spinal tsDCS methodology to modulate spinal excitability in healthy subjects

Proposed methods for first phase Sample size: 10 healthy subjects Intervention: Anodal, cathodal or sham tsDCS at T11 2 cm paraspinally 2mA for 15 mins Outcome measures: MEPs will be evoked using trans magnetic stimulation MEPs, H-reflex and F-wave will be recorded via surface electrodes over gastrocnemius muscle & abductor hallucis muscle bilaterally before & after tsDCS

Reference electrode at infraclavicular area Active electrode T11 2 cm from spinous process Direct current stimulator

Transcranial Magnetic Stimulation MEP amplitude Transcranial Magnetic Stimulation

First phase Anticipated Results Improved motor output following cathodal tsDCS Increased MEPs Increased F wave and Decreased H reflex

Preliminary results: Preliminary testing in a single healthy subject suggests that cathodal tsDCS at T11 has greater facilitatory effects on MEPs compared to anodal tsDCS

Scientific plan Second phase: Apply the tsDCS methodology developed in phase one to subjects with SCI Evaluate modulation of spinal excitability Same outcome measures as in 1st phase If measures show favorable findings then we will progress to phase three

Scientific plan Third Phase: Our long term objective is to evaluate the effects of tsDCS on functional motor recovery, paired with robot-assisted treadmill training in subjects with SCI

Potential Problems Skin irritation & lesions have been reported following transcutaneous DC stimulation (caution in SCI) Pain Duration of the effects Is there any potential for inducing autonomic dysreflexia?

Discussion If successful the proposed stimulation technique would mark a significant advancement in the field of SCI rehabilitation Non-invasive Inexpensive

Questions