Abstract
Symptoms of visuospatial neglect occur frequently after unilateral brain damage. Neglect hampers rehabilitation progress and is associated with reduced quality of life. However, existing treatment methods show limited efficacy. Transcranial direct current stimulation (tDCS) is a neuromodulatory technique, which can be used to increase or decrease brain excitability. Its combination with conventional neglect therapy may enhance treatment efficacy. A 72-year-old male with a subacute ischemic stroke of the right posterior cerebral artery suffering from visuospatial neglect, hemianopia, and hemiparesis was treated with biparietal tDCS and cognitive neglect therapy in a double-blind, sham-controlled single-case study. Four weeks of daily treatment sessions (5 days per week, 30 min) were started 26 days post-stroke. During week 1 and 4 the patient received conventional neglect therapy, during week 2, conventional neglect therapy was combined once with sham and once with real biparietal tDCS. Week 3 consisted of daily sessions of real biparietal tDCS (1 mA, 20 min) combined with neglect therapy. Outcome measures were assessed before, immediately after, as well as 1 week and 3 months after the end of treatment. They included subtests of the Test for Attentional Performance (TAP): covert attention (main outcome), alertness, visual field; the Neglect-Test (NET): line bisection, cancelation, copying; and activities of daily living (ADL). After real stimulation, covert attention allocation toward left-sided invalid stimuli was significantly improved, and line bisection and copying improved qualitatively as compared to sham stimulation. ADL were only improved at the 3-month follow-up. This single-case study demonstrates for the first time that combined application of tDCS and cognitive training may enhance training-induced improvements in measures of visuospatial neglect and is applicable in a clinical context.
Highlights
Neglect is a higher-order, supramodal cognitive deficit, which affects space-related behavior not caused by an elementary sensorimotor deficit (Kerkhoff, 2001), and is mainly caused by lesions in frontoparietal cortical and subcortical networks (Doricchi et al, 2008)
Covert attention to valid left-sided stimuli was strongly impaired at admission, showed significant improvements during standard therapy reaching a stable and normal level after the first combined real Transcranial direct current stimulation (tDCS) treatment, and was maintained until long-term follow-up (Tables 1, 2)
We found a significantly larger improvement in therapy outcome www.frontiersin.org after combined biparietal tDCS and cognitive training, while cognitive training on its own after single treatment sessions as well as repeated sessions over a time-period of 5 days did not lead to significant changes
Summary
Neglect is a higher-order, supramodal cognitive deficit, which affects space-related behavior not caused by an elementary sensorimotor deficit (Kerkhoff, 2001), and is mainly caused by lesions in frontoparietal cortical and subcortical networks (Doricchi et al, 2008). Visuospatial neglect occurs in over 40% of right brain-lesioned patients and in 20% of left brainlesioned patients (Ringman et al, 2004) and more than 60% of the patients remain impaired after the end of rehabilitation (Carod-Artal et al, 2000; Clarke et al, 2002). Visuospatial neglect limits the success of other neurorehabilitative interventions, such as physical and occupational therapy. Treatment options to date show limited efficiency (Bowen et al, 2013) despite being time-intense. They mostly aim to compensate (e.g., optokinetic stimulation or neck muscle vibration) or substitute functions (e.g., prism adaptation), and few aim to restitute functions (e.g., mental imagery). Different therapeutic approaches are often combined and individually adapted to the needs of each patient
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