The feasibility and effectiveness of using prism adaptation to treat motor and spatial dysfunction in stroke survivors with multiple incidents of stroke

No short-term treatment effect of prism adaptation for spatial neglect: An inclusive meta-analysis

Despite 25 years of research on the topic, there is still no consensus on whether prism adaptation is an effective therapy for visuospatial neglect. We have addressed this question through a meta-analysis of the most well-controlled studies on the topic. Our main meta-analytic model included studies with a placebo/sham/treatment-as-usual control group from which data from right hemisphere stroke patients and left-sided neglect could be aggregated. The short-term treatment effects on the two commonly used standard tests for neglect, the conventional Behavioural Inattention Test (BIT-C) and cancellation test scores were combined into one random effect model justified by the fact that 89% of the BIT-C score is determined by cancellation tasks. With this approach, we were able to obtain a larger and more homogeneous dataset than previous meta-analyses: sixteen studies including 430 patients. No evidence for beneficial effects of prism adaptation was found. The secondary meta-analysis including data from the Catherine Bergego Scale, a functional measure of activities of daily living, also found no evidence for the therapeutic effects of prism adaptation, although half as many studies were available for this analysis. The results were consistent after the removal of influential outliers, after studies with high risk-of-bias were excluded, and when an alternative measure of effect size was considered. These results do not support the routine use of prism adaptation as a therapy for spatial neglect.

Spatial neglect treatment: The brain's spatial-motor Aiming systems

Animal and human literature supports spatial-motor "Aiming" bias, a frontal-subcortical syndrome, as a core deficit in spatial neglect. However, spatial neglect treatment studies rarely assess Aiming errors. Two knowledge gaps result: spatial neglect rehabilitation studies fail to capture the impact on motor-exploratory aspects of functional disability. Also, across spatial neglect treatment studies, discrepant treatment effects may also result from sampling different proportions of patients with Aiming bias. We review behavioural evidence for Aiming spatial neglect, and demonstrate the importance of measuring and targeting Aiming bias for treatment, by reviewing literature on Aiming spatial neglect and prism adaptation treatment, and presenting new preliminary data on bromocriptine treatment. Finally, we review neuroanatomical and network disruption that may give rise to Aiming spatial neglect. Because Aiming spatial neglect predicts prism adaptation treatment response, assessment may broaden the ability of rehabilitation research to capture functionally-relevant disability. Frontal brain lesions predict both the presence of Aiming spatial neglect, and a robust response to some spatial neglect interventions. Research is needed that co-stratifies spatial neglect patients by lesion location and Aiming spatial neglect, to personalize spatial neglect rehabilitation and perhaps even open a path to spatial retraining as a means of promoting better mobility after stroke.

Can prism adaptation effects generalize to wheelchair maneuvering?

BACKGROUND

While prism adaptation (PA) has been recognized as a promising tool for treating spatial neglect, implementation as a standard treatment in clinical care has been lagging. Limited evidence for the generalization of after-effects to everyday activities has been a barrier towards implementation.

OBJECTIVES

This study examined whether a home-friendly standardized PA protocol (Peg-the-Mole, PTM) induces after-effects that can transfer to wheelchair maneuvering. We also examined the impact of using constant (1 starting hand position) or variable (3 starting hand positions) training conditions on the transfer of after-effects to wheelchair maneuvering.

METHODS

Sixty participants were randomly assigned to one of four PTM conditions: 1) prisms/constant training; 2) prisms/variable training; 3) sham goggles/constant training; 4) sham goggles/variable training.

RESULTS

The use of PTM with rightward shifting prisms induced after-effects on proprioceptive and visual pointing outcome tasks. Groups using PTM with prism goggles showed a leftward shift in their position within a wheelchair course and a reduction in the number of right-sided collisions. The training condition did not have an impact on the transfer of after-effects to wheelchair driving.

CONCLUSION

PTM is a clinically appealing PA protocol that induces after-effects that can transfer to an everyday activity relevant to patients with neglect.

Exploring the time-course and the reference frames of adaptation to optical prisms and its aftereffects

Prism adaptation (PA) is used to investigate visuo-motor plasticity and to rehabilitate the syndrome of Unilateral Spatial Neglect (USN). After PA, participants show aftereffects (AEs), contralateral to the side of the optical displacement in several tasks. This study explored the features of these AEs, specifically the "egocentric" versus "allocentric, object-based", reference frames involved, and their time course. In three experiments, healthy participants adapted to prismatic lenses inducing a horizontal displacement of the visual field. In Experiment #1, participants adapted to rightward displacing prisms. Four tasks were used requiring repeated pointings towards the participant's subjective egocentric straight-ahead, with the availability of proprioceptive or visual-proprioceptive signals, and, in some conditions, of an external allocentric visual frame (i.e., a rectangular paper sheet). Experiment #2 explored the role of the position of the allocentric frame, with AEs being tested by straight-ahead and frame bisection tasks, requiring pointing toward the external visual frame, placed in different positions of the working space. An egocentric visual proprioceptive task was administered after prism removal and after the execution of the allocentric tasks, to assess the effectiveness of the PA, as indexed by the AEs, and their persistence up to the end of the administration of the allocentric tasks. Experiment #3 differed from #2 in that participants adapted to leftward displacing lenses. Consistent with evidence from USN patients, in Experiment #1, in the egocentric tasks, AEs lasting up to 30 min after PA were found. In Experiment #2, AEs in "allocentric" tasks did not occur, regardless of frame position. Experiment #3 showed AEs in both the "egocentric" and the "allocentric" tasks, with the latter being minor in size. These findings illustrate that the spatial reference systems modulated by PA in extra-personal space primarily operate in spatial "egocentric" reference frames, with a comparatively minor and direction-specific role of "allocentric" frames.

Quantitative Assessment of Motor Neglect

[Figure: see text].

Neglect syndrome in post-stroke conditions: assessment and treatment (scoping review)

There is no consensus about the definition or most effective treatment for neglect syndrome. The aim of this review was therefore to evaluate the results of trials that investigated different treatment methods for neglect syndrome. A systematic literature search in PubMed and Web of Science databases was performed to identify studies that investigated the effects of neglect therapies. Authors followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. Studies were selected by two assayers, and disagreement was resolved by a third reviewer. The literature search identified 202 articles: 19 met the inclusion criteria and were included for data extraction. Thirty-five different kinds of assessments were used in these studies, and 17 treatment methods were applied. Successful treatments were reported at least in some parts of the assessments in 12 studies: mirror therapy (in two trials), transcranial magnetic stimulation, street crossing test in virtual reality, smooth pursuit eye movement training, saccadic eye movement therapy, direct current stimulation, eye patching therapy, prism adaptation treatment, socially assistive pet-type therapeutic robot (PARO), Kinesiological Instrument for Normal and Altered Reaching Movement robotic device therapy, transcutaneous electrical nerve stimulation, and optokinetic stimulation (the last two methods in the same trial). No success was shown in seven trials, which contained not only single treatments but combined ones also. Authors concluded that there are no convincing results for or against any of the different therapies used for neglect syndrome. The quality of the trials is questionable, and the numbers of included patients are small in the trials.

Applications of Functional Magnetic Resonance Imaging in Determining the Pathophysiological Mechanisms and Rehabilitation of Spatial Neglect

Functional magnetic resonance imaging (fMRI) is a neuroimaging tool which has been applied extensively to explore the pathophysiological mechanisms of neurological disorders. Spatial neglect is considered to be the failure to attend or respond to stimuli on the side of the space or body opposite a cerebral lesion. In this review, we summarize and analyze fMRI studies focused specifically on spatial neglect. Evidence from fMRI studies have highlighted the role of dorsal and ventral attention networks in the pathophysiological mechanisms of spatial neglect, and also support the concept of interhemispheric rivalry as an explanatory model. fMRI studies have shown that several rehabilitation methods can induce activity changes in brain regions implicated in the control of spatial attention. Future investigations with large study cohorts and appropriate subgroup analyses should be conducted to confirm the possibility that fMRI might offer an objective standard for predicting spatial neglect and tracking the response of brain activity to clinical treatment, as well as provide biomarkers to guide rehabilitation for patients with SN.

Improved stability of long-duration sitting in spatial neglect after a single session of prism adaptation

Spatial neglect after right brain stroke affects balance, and improvements in sitting balance after prism adaptation have been demonstrated using short-duration center of pressure (CoP) data. We present long-duration (5 min) CoP and trunk muscles electromyography recordings of a 61-year-old man with left-sided spatial neglect, before and after a single session of prism adaptation. His CoP-derived measures showed improved balance and postural stability in both the anterior-posterior and medial-lateral directions after prism adaptation. Concurrently, asymmetry in neuromuscular activations was reduced. The findings suggest that improved sitting balance may be associated with more symmetrical activation of trunk muscles after prism adaptation.

Multisensory stimulation for the rehabilitation of unilateral spatial neglect

Unilateral spatial neglect (USN) is a neuropsychological syndrome, typically caused by lesions of the right hemisphere, whose features are the defective report of events occurring in the left (contralesional) side of space and the inability to orient and set up actions leftwards. Multisensory integration mechanisms, largely spared in USN patients, may temporally modulate spatial orienting. In this pilot study, the effects of an intensive audio-visual Multisensory Stimulation (MS) on USN were assessed, and compared with those of a treatment that ameliorates USN, Prismatic Adaptation (PA). Twenty USN stroke patients received a 2-week treatment (20 sessions, twice per day) of MS or PA. The effects of MS and PA were assessed by a set of neuropsychological clinical tests (target cancellation, line bisection, sentence reading, personal neglect, complex drawing) and the Catherine Bergego Scale for functional disability. Results showed that MS brought about an amelioration of USN deficits overall comparable to that induced by PA; personal neglect was improved only by MS, not by PA. The clinical gains of the MS treatment were not influenced by duration of disease and lesion volume, and they persisted up to one month post-treatment. In conclusion, MS represents a novel and promising rehabilitation procedure for USN.

A One-Year Follow-Up Study on Community Dwelling Multiple Stroke Survivors with Spatial Neglect

This study assessed nine participants, who sustained multiple strokes and had spatial neglect, one year after participation in a prior trial on whether Prism Adaptation Treatment (PAT) was a feasible and effective treatment for spatial neglect remediation compared to standard care. The objectives were to: (1) describe the sample, (2) measure the degree of spatial neglect symptoms if present, and (3) determine group differences in motor and spatial performance. Three (60%) participants from the PAT group and two (50%) from the comparison group still displayed spatial neglect. A series of two-way mixed ANOVAs exploring group (PAT vs. comparison of standard care) and time effects (pretest vs. posttest vs. follow-up) found a main effect of time for all participants on the Kessler Foundation Neglect Assessment (F(1,2) = 30.28, p<.001), Functional Independence Measure (F(1,2) = 16.998, p<.001), and star cancelation (F(1,2) = 11.077, p<.001). An interaction effect of time*prism was observed when assessing the line bisection test (F(1,2) = 6.986, p = .008), suggesting that the PAT group performed significantly better on this test. Additional research should be completed with a larger sample in order to better understand the PAT long term effects as well as develop clinical recommendations for occupational therapy practitioners.