Brain Activations During Optokinetic Stimulation in Acute Right-Hemisphere Stroke Patients and Hemispatial Neglect: An fMRI Study

Combined optokinetic stimulation and cueing-assisted reading therapy to treat hemispatial neglect: A randomized controlled crossover trial

BACKGROUND

Hemispatial neglect is a disabling cognitive disorder following stroke and effective therapies are required.

OBJECTIVES

To evaluate the effects of combined optokinetic stimulation (OKS) and cueing-assisted reading therapy (READ) on the remission of hemispatial neglect following stroke.

METHODS

Randomized, controlled, two-period, crossover trial conducted at a German neurorehabilitation center. Twenty participants with left neglect following right hemispheric stroke (mean age 66 years (SD 11), mean time since stroke 50 days (SD 33)) finished the trial (12 received OKSREAD first, 8 CONTROL first). The intervention consisted of 15 daily sessions of OKS (20 min) and text reading assisted by a therapist providing cues (20 min). The control treatment was a same-number, same-length neuropsychological treatment not targeting visuospatial attention. Primary outcomes were the change in performance of a customized neuropsychological test battery for neglect (0% worst - 100% best) and a test of neglect-related functional disability (Catherine Bergego Scale, 0 no impairment - 30 severest impairment), assessed before and after each treatment period. Secondary outcomes were performance in the 6 single tests composing the battery (e.g., omissions in text reading, center of cancellation in the Bells test, spatial bias of fixations when freely viewing photographs) and a clinical test of anosognosia.

RESULTS

Overall performance in the neglect test battery improved slightly more after OKSREAD than after CONTROL (d=6%; p=0.002). The remission of neglect-related functional disability did not differ between treatments (d=-2; p=0.291). Ipsilesional fixation bias during free viewing was the only secondary outcome that was improved by OKSREAD as compared to CONTROL (d= -2.8°; p=0.005).

CONCLUSION

At the applied intensity, the combined OKSREAD intervention slightly attenuated the ipsilesional attention bias in persons with neglect, but it did not improve neglect-related functional disability, anosognosia, or other neglect symptoms to a clinically meaningful degree.

CLINICAL TRIAL REGISTRATION

URL: http://www.

CLINICALTRIALS

gov. Unique identifier: NCT04273620.

Efficacy of Unilateral and Bilateral Parietal Transcranial Direct Current Stimulation on Right Hemispheric Stroke Patients With Neglect Symptoms: A Proof-of-Principle Study

Different transcranial direct current stimulation (tDCS) protocols have been tested to improve visuospatial neglect (VSN). So far, methodological heterogenity limits reliable conclusions about optimal stimualtion set-up. With this proof-of-principle study behavioral effects of two promising (uni- vs. bilateral) stimulation protocols were directly compared to gain more data for an appropriate tDCS protocol in subacute neglect patients. Notably, each tDCS set-up was combined with an identical sham condition to improve comparability. In a double-blind sham-controlled cross-over study 11 subacute post-stroke neglect patients received 20 minutes or 30 seconds (sham) tDCS (2 mA, 0.8 A/m²) parallel to neglect therapy randomized in unilateral (anode-reference: P4-Fp2 10-20 electroencephalography [EEG] system) and bilateral manner (anode-cathode: P4-P3) and 48h wash-out in-between. Before and immediately after stimulation performance were measured in cancellation task (bell test), and line bisection (deviation error). Significant difference between active and assigned sham condition was found in line bisection but not cancellation task. Particularly, deviation error was reduced after bilateral tDCS (hedges g^* = 0.6) compared to bilateral sham, no such advantage were obtained for unilateral stimulation (hedges g^* = 0.2). Using a direct comparison approach findings add further evidence that stimulating both hemispheres (bilateral) is superior in alleviating VSN symptoms than unilateral stimulation in subacute neglect.

Prism Adaptation and Optokinetic Stimulation Comparison in the Rehabilitation of Unilateral Spatial Neglect

Prism adaptation (PA) is one of the most effective treatments for the rehabilitation of unilateral spatial neglect. Optokinetic stimulation (OKS) has also been demonstrated to be effective in ameliorating symptoms of neglect. The aim of this study is to compare the effectiveness of these two methods in a group of neglect patients using a crossover design. A group of 13 post-acute brain-damaged patients with unilateral spatial neglect, who had never been rehabilitated, were treated using PA and OKS. Each treatment was applied for 10 sessions, twice a day, to all patients with both treatments in crossed order (i.e., PA followed by OKS or vice versa). Neuropsychological assessments were performed: before the first (T1), at the end of the first/beginning of the second (T2) and at the end of the second training sessions (T3), and two weeks after the end of treatment (T4). Both procedures produced a significant improvement in clinical tests at T2, independent of the type of training. The results suggest that either PA or OKS induces a significant amelioration of neglect in right brain-damaged patients, mainly in the first block of treatment. Since no differences between treatments were found, they could be applied in clinical practice, according to the requirements of the individual patient.

Robot-Assisted Arm Training in Stroke Individuals With Unilateral Spatial Neglect: A Pilot Study

Background: Robot-assisted arm training (RAT) is an innovative exercise-based therapy that provides highly intensive, adaptive, and task-specific training, yet its effects for stroke individuals with unilateral spatial neglect remain to be explored. The study was aimed to investigate the effects of RAT on unilateral spatial neglect, arm motor function, activities of daily living, and social participation after stroke.

Methods: In a pilot randomized controlled trial, individuals with unilateral spatial neglect after right hemisphere stroke were equally allocated to intervention group and control group, 45-min training daily, 5 days/week, for 4 weeks. Outcome measures included the Behavioral Inattention Test-conventional section (BIT-C), Catherine Bergego Scale (CBS), Fugl-Meyer Assessment for Upper Extremity (FMA-UE), Modified Barthel Index (MBI), and World Health Organization Disability Assessment Schedule Version 2.0 (WHODAS 2.0).

Results: From November 2018 to February 2021, 20 stroke patients (mean age 47.40 ± 8.47) were enrolled in the study. Robot-assisted arm training was feasible and safe for individuals with unilateral spatial neglect. Both groups had significant improvements in all outcome measures. Participants assigned to RAT therapy had significantly greater improvements in BIT-C (difference, 7.70; 95% CI, 0.55–14.85, P = 0.04), FMA-UE (difference, 5.10; 95% CI, 1.52–8.68, P = 0.01), and WHODAS 2.0 (difference, −7.30; 95% CI, −12.50 to −2.10, P = 0.01). However, the change scores on CBS and MBI demonstrated no significance between the groups.

Conclusion: Our findings provide preliminary support for introducing robot-assisted arm training to remediate unilateral spatial neglect after stroke. The training program focusing on neglect of contralateral space and affected upper extremity may be effective in neglect symptoms, motor function recovery, and social participation, while not generalizing into improvements in activities of daily living.

Clinical Trial Registration: Chinese Clinical Trial Registry (http://www.chictr.org.cn/) on 17 October 2019, identifier: ChiCTR1900026656.

Repeated application of the covert shift of attention task improves endogenous but not exogenous attention in patients with unilateral visuospatial inattention

BACKGROUND

Most neglect treatment studies focus on automatic re-orientation procedures, assuming a deficit in automatic processes. We compare an automatic- and a controlled procedure, using the endogenous and exogenous variants of Posner's covert shift of attention task.

METHOD

In two experiments, neglect patients and patients with a right hemispherical stroke without neglect performed three blocks of Posner's covert shift of attention task (Posner Task) on two days. In Study 1 we used endogenous cues, in Study 2, exogenous cues.

RESULTS

In the endogenous task, neglect patients improved significantly with valid left-sided cues between block 1 and 2 on Day 1, subsequently showing a plateauing. They also showed a gradual improvement on invalid trials on both days. In the exogenous condition, all participants responded only increasingly faster on trials with a long stimulus onset asynchrony. Practicing on both tasks led to fewer omissions for left-sided targets, minimally in the exogenous and clearly in the endogenous condition.

CONCLUSION

In line with prior neuroanatomical studies, our study shows that practicing an endogenous, but not an exogenous, visuospatial attention task leads to significant improvements in neglect patients, especially for invalid trials, suggesting that neglect treatments based on top-down strategies should be given more attention.

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.

Unilateral Spatial Neglect After Stroke: Current Insights

INTRODUCTION

Unilateral spatial neglect (USN) is a disorder of contralesional space awareness which often follows unilateral brain lesion. Since USN impairs awareness of contralesional space/body and often of concomitant motor disorders, its presence represents a negative prognostic factor of functional recovery. Thus, the disorder needs to be carefully diagnosed and treated. Here, we attempted to present a clear and concise picture of current insights in the comprehension and rehabilitation of USN.

METHODS

We first provided an updated overview of USN clinical and neuroanatomical features and then highlighted recent progresses in the diagnosis and rehabilitation of the disease. In relation to USN rehabilitation, we conducted a MEDLINE literature research on three of the most promising interventions for USN rehabilitation: prismatic adaptation (PA), non-invasive brain stimulation (NIBS), and virtual reality (VR). The identified studies were classified according to the strength of their methods.

RESULTS

The last years have witnessed a relative decrement of interest in the study of neuropsychological disorders of spatial awareness in USN, but a relative increase in the study of potential interventions for its rehabilitation. Although optimal protocols still need to be defined, high-quality studies have demonstrated the efficacy of PA, TMS and tDCS interventions for the treatment of USN. In addition, preliminary investigations are suggesting the potentials of GVS and VR approaches for USN rehabilitation.

CONCLUSION

Advancing neuropsychological and neuroscience tools to investigate USN pathophysiology is a necessary step to identify effective rehabilitation treatments and to foster our understanding of neurofunctional bases of spatial cognition in the healthy brain.