Abstract
Stroke remains a leading cause of disability (Krishnamurthi et al., 2013) in the United States, with 795,000 new strokes occurring annually (Mozaffarian et al., 2016). One of the most common poststroke impairments is upper-extremity (UE) hemiparesis, which severely undermines quality of life (Gordon et al., 2004). Although many approaches aim to reduce UE impairment, most are efficacious only in survivors with minimal impairment (Page & Peters, 2014; Wolf et al., 2008), a group constituting only ≈20% of the poststroke population (Wolf & Binder-MacLeod, 1983).
The most effective UE treatment approaches promote neuroplastic reorganization and motor recovery through repetitive, task-specific training (RTP) of the affected UE, but such practice is not always feasible for the majority of stroke survivors with moderate to severe UE impairment. Indeed, these survivors typically exhibit little to no active hand and wrist function, making task practice alone difficult to implement. Transcranial direct current stimulation (tDCS) delivers a constant, low current to upregulate or downregulate activity in targeted brain regions. It is portable and safe (Poreisz, Boros, Antal, & Paulus, 2007), and the device can be easily worn without interfering with movement attempts, including in people with moderate to severe UE impairment.
Although many studies have demonstrated the efficacy of tDCS when combined with motor rehabilitation (Peters, Edwards, Wortman-Jutt, & Page, 2016), virtually all of them recruited participants with minimal impairment (Butler et al., 2013; Rocha et al., 2016), used short-term regimens (Ang et al., 2015; Bolognini et al., 2015), or used physical practice interventions that were not occupation based (Kasashima-Shindo et al., 2015; Triccas et al., 2015). Moreover, although two recent meta-analyses that examined the effect of tDCS on UE impairment (Butler et al., 2013; Elsner, Kugler, Pohl, & Mehrholz, 2013) found a significant effect of tDCS compared with sham, the included studies almost exclusively recruited participants with minimal impairment in the chronic stage of recovery, thus limiting the generalizability of these results. Therefore, a gap remains, centering on the need to examine the efficacy of tDCS combined with task-specific motor rehabilitation in stroke survivors with moderate UE hemiparesis.
To bridge this gap, the aim of this study was to determine the efficacy of tDCS when combined with RTP on affected UE impairment and UE use in a chronic stroke survivor with moderate impairment. We hypothesized that this combined approach would decrease UE impairment and increase UE use in daily activities.
Method
Participant
The participant was a 54-yr-old woman who had experienced a right hemisphere ischemic cortical stroke 10 yr before study enrollment. She demonstrated stable UE deficits at baseline, scoring a 26 and a 27 at the first and second baseline testing sessions, respectively. This participant lived outside of commuting distance from the laboratory but was able to accommodate the protocol through travel and hotel boarding 2 nights/wk for the duration of the study.
Outcome Measures
After screening was done and the participant had signed an approved consent form, assessments were administered twice before intervention (no greater than 1 wk apart and less than 2 wk before the start of the intervention) to ensure the stability of UE deficits. Assessments were also administered immediately afterward and at 2 mo postintervention. All testing was performed in a quiet testing room adjacent to our laboratory by the same rater (a trained and licensed occupational therapist) at all time points, to increase reliability. Outcome measures were chosen to assess not only UE impairment but also affected limb use in daily activities outside of the laboratory.
UE Section of the Fugl–Meyer Assessment.
The UE Section of the Fugl–Meyer Assessment (UEFM; Fugl-Meyer, Jääskö, Leyman, Olsson & Steglind, 1975) was used to determine changes in UE impairment. This measure assesses movement at all affected UE joints as well as strength, coordination, and hypertonia. Each item is scored using a 2- or 3-point ordinal scale (0 = cannot perform, 1 = performs partially, 2 = performs fully) for a total possible score of 66 points. A score increase of at least 4.25 yields a clinically important difference in people with mild to moderate impairment due to stroke (Page, Fulk, & Boyne, 2012). The UEFM has been shown to have impressive test–retest reliability, interrater reliability, and construct validity (Di Fabio & Badke, 1990; Duncan, Propst, & Nelson, 1983).
Motor Activity Log.
An integral component of facilitating neuroplasticity is reintegration of the affected limb into daily activities. Therefore, the Motor Activity Log (MAL; van der Lee, Beckerman, Knol, de Vet, & Bouter, 2004) was administered to quantify changes in the participant’s UE use. Respondents rate, on a 6-point ordinal scale, how often (0 = never used to 5 = used prestroke amount) and how well (0 = very poor to 5 = same as prestroke) they had been able to use the affected UE in 30 various daily activities in the past wk. These scores are added together and divided by the total number of items to obtain scores for each of the subscales. Although there is currently no established minimal clinically important difference in this population, previous research has indicated that the MAL is a valid and reliable scale of arm use and movement quality in real-world settings (van der Lee et al., 2004).
Apparatus
tDCS is a form of noninvasive brain stimulation that delivers a constant, low current into the brain, causing alterations in activity in brain regions under the electrode sites (Lefaucheur et al., 2017). To be specific, anodal stimulation causes excitation of cortical structures, potentially leading to increased synaptic communication and long-term potentiation (Nitsche & Paulus, 2000). For the treatment of UE impairment, anodal stimulation is delivered to the affected primary motor cortex, ideally alongside rehabilitative therapies, to facilitate neuroplasticity and augment motor recovery. Indeed, an increasing body of literature has suggested that anodal stimulation delivered as an adjunct to physical practice increases UE motor function in chronic stroke (Butler et al., 2013).
tDCS was delivered through saline-soaked electrode sponges (3 in. × 4.75 in.) using a Chattanooga Ionto™ system (Patterson Medical, Warrenville, IL). The anodal electrode was placed over the UE representation on the affected primary motor cortex (C3 or C4, based on the international 10/20 electroencephalogram system), and the reference electrode was placed over the contralateral supraorbital region (Fp1 or Fp2, based on the international 10/20 electroencephalogram system). For this study, 2 mA of stimulation were delivered for the first 20 min of the RTP intervention, at which point the stimulator automatically turned off and therapy continued uninterrupted for the remaining 25 min.
Intervention
The RTP of the affected limb is the foundation on which neurorehabilitative therapies are based, and it has been shown to facilitate neuroplasticity and cortical reorganization after stroke (Woldag & Hummelsheim, 2002). In light of this, an RTP intervention was chosen as the basis for the therapy regimen, which consisted of 45-min RTP sessions occurring 3 days/wk for 8 wk. The same therapist administered all sessions for the duration of the intervention. Tasks were chosen on the basis of extensive pilot work in which RTP was integrated alongside various adjunctive interventions such as mental practice, modified constraint-induced therapy, and electrical stimulation (Page, Levine, & Leonard, 2005, 2007). Moreover, this intervention represents current best practice in UE motor rehabilitation, which emphasizes repetitive, goal-directed use of the affected limb.
During these pilot RTP experiences, our laboratory staff identified a list of nearly 60 activities of daily living that many stroke patients wish to relearn. From this list, various activities were identified that were meaningful to the participant and appropriate given her impairment level, based on the therapist’s clinical judgment; specifically, she focused intensely on the following four activities: (1) brushing hair; (2) bringing a toothbrush to her mouth while standing at a sink; (3) simulated meal preparation in a kitchen environment (i.e., cutting, scooping, pan frying, and pouring tasks); and (4) home management tasks, such as sweeping and picking up laundry from the floor. Within each of these activities, tasks were broken down into manageable parts (i.e., part–whole practice) until the participant achieved proficiency, at which point the parts were put together to form a complete activity. For example, within the activity of hair brushing, the participant first repetitively practiced using elbow flexion to bring the hairbrush to her head. Once this component was mastered, she practiced forearm supination to point the hairbrush in the direction of her hair. Then, these two components were combined to complete the full activity.
Results
Over the course of the 8-wk intervention the participant reported a minor tingling and itching sensation under the electrode site, which is consistent with previous studies that have used tDCS (Nitsche & Paulus, 2001). The participant never requested that the stimulation be stopped, and there were no adverse events associated with this protocol.
Scores on all outcome measures are listed in Table 1. The participant demonstrated stability of UE deficits before intervention, scoring a 26 and a 27 on the first and second UEFM pretests, respectively. She demonstrated a 6.5-point increase on the UEFM immediately after the intervention and a 7.5-point increase at 2 mo postintervention. Her performance on the MAL yielded an increase of 0.46 points in amount of use and in the quality of use of the affected arm from baseline to the first posttest. Moreover, she continued to increase use of her affected arm 2 mo postintervention, exhibiting an increase of 0.70 and 0.63 on the Amount of Use and Quality of Use subscales, respectively.
Participant’s Scores on Outcome Measures
Note. AOU = Amount of Use subscale; Pre = the result of the average score of both pretests; QOM = Quality of Movement subscale; UEFM = Upper Extremity Section of the Fugl–Meyer Assessment.
Discussion
A growing body of research has indicated that tDCS combined with motor rehabilitation decreases UE impairment and increases UE function in chronic stroke survivors; however, the vast majority of this research has been conducted on people with minimal impairment, a group that comprises only a small minority of the poststroke population. Furthermore, many of the studies have incorporated physical practice regimens that require expensive equipment (e.g., robotics, virtual reality) or non–task-based therapies, despite the well-established and widely recognized importance of task-specific training in promoting neuroplasticity (Hubbard, Parsons, Neilson, & Carey, 2009; Nudo & Friel, 1999). To bridge this gap, in the current case study we investigated the effects of an 8-wk regimen of RTP and tDCS on affected arm outcomes in a chronic stroke survivor with moderate impairment.
Immediately after the 8-wk intervention, the participant demonstrated a 6.5-point increase on the UEFM. Moreover, she continued to improve after completion of the study, demonstrating a 7.5-point increase 2 mo postintervention. These scores surpassed the minimal clinically important difference threshold of 4.25 points (Page et al., 2012), meaning that these changes likely conferred a functional benefit. Indeed, over the course of therapy this participant demonstrated increased proficiency in activities such as teeth brushing, pouring, and scooping with a spoon, likely as a result of marked increases in supination, elbow extension, and shoulder flexion. Furthermore, compensatory movement patterns also diminished over the course of treatment; specifically, she demonstrated an increased ability to pour water out of a cup using controlled elbow extension and shoulder flexion, without recruiting lateral trunk flexion and shoulder elevation and abduction. These UE impairment reductions are in accord with recent reviews of tDCS combined with motor rehabilitation in chronic stroke (Butler et al., 2013; Peters et al., 2016). However, it is important to note that this woman had more severe impairment than most participants enrolled in previous studies, suggesting that tDCS may be effective in the rapidly expanding population of stroke survivors with moderate impairment. These gains are comparable to other approaches that require expensive, cumbersome equipment (Kasashima-Shindo et al., 2015; Triccas et al., 2015) or high-intensity regimens (Wolf et al., 2008), making this approach a practical adjunct for rehabilitative practice.
Although reductions in UE impairment alone are not sufficient to warrant implementation of an intervention, the participant also demonstrated increased scores on the MAL, indicating that she used her affected arm more frequently and proficiently in daily tasks. It is important to note that she continued to increase the use of her affected arm in daily activities on both the Quality of Movement and Amount of Use subscales of the MAL at the 2-mo follow-up. Increased scores on MAL items were also consistent with specific gains on the UEFM; specifically, she demonstrated increased supination on the UEFM, which translated into increased frequency and quality of movement during teeth brushing and turning a doorknob. In addition, the participant reported increased frequency and proficiency when opening a refrigerator, wiping off a counter, operating a light switch, steadying herself while standing, and pulling chairs away from or toward a table before sitting down, likely as a result of an increased ability to simultaneously extend the elbow and flex the shoulder.
Taken together, these data add to the growing body of literature indicating that tDCS combined with RTP increases UE outcomes after stroke. Because this was a single case study we cannot make generalizations about the treatment efficacy in the larger population of chronic stroke survivors with moderate impairment; however, a larger study is currently underway that is using this exact regimen to determine the long-term outcomes in a larger sample of participants with moderate to severe impairment. Also, given the chronicity of the participant’s stroke and the fact that there were no other rehabilitative treatments being delivered during the study time frame, these gains likely were a direct result of the study intervention.
Implications for Occupational Therapy Practice
Occupational therapists apply a variety of physical treatment approaches to remediate physical impairments that impede occupational performance. Practitioners also apply physical agent modalities to facilitate increased participation and success in therapy. Many adjunctive technologies and treatment approaches, however, require expensive, cumbersome equipment (e.g., robotics) that is not realistic in many clinical environments or cannot be overlaid onto functional activities. Moreover, many commonly used treatment approaches are only efficacious in stroke survivors exhibiting some degree of active hand and wrist function, a group that includes only a minority of the stroke survivor population. tDCS bridges these gaps, because it is portable, inexpensive, and able to be administered concurrent with a variety of functional, occupation-based tasks regardless of impairment level. Although more research is needed to determine optimal stimulation parameters and dosing, existing evidence suggests that tDCS may constitute a promising adjunct to occupational therapy practice that can be easily and cost-effectively integrated into clinical environments.
Conclusion
tDCS combined with RTP decreased UE impairment and increased UE use in a chronic stroke survivor with moderate impairment immediately and 2 mo after intervention. The treatment protocol is simple to deliver, relatively inexpensive, and easily incorporated alongside rehabilitative therapies. The risk associated with tDCS is minuscule and is far outweighed by the potential benefits of its use. Future studies that recruit larger sample sizes, incorporate a double-blind study design, and include a control group are needed to determine the efficacy of tDCS combined with RTP in this population.
Footnotes
Acknowledgments
This case study was funded by LSVT Global.