Stroke is the leading cause of functional impairment and long-term disability among adults worldwide1,2. The incidence of stroke will increase to 35% in 2050 as the proportion of older adults rises3, and the cost and burden of post-stroke care remain substantial2,4. Four-fifths of stroke survivors experience arm and hand paresis with different degrees of severity5, and up to 66% of patients with affected upper limbs are still incapable of performing daily activities at 6 months post-stroke6.
Thus, one of the top priorities in stroke rehabilitation is to develop
and provide effective and specific interventions for improving
upper-limb motor recovery and function in patients.
Over the last few years, mirror therapy (MT) and action
observation therapy (AOT) have become promising approaches to enhance
the efficacy of stroke motor rehabilitation7.
In conventional MT, patients observe a reflection of the movements of
the non-affected upper limb as if it were the affected one by using a
plain mirror or mirror box8,9. Conventional MT is a simple, easy-to-use, and relatively low cost intervention9.
During AOT, patients carefully observe motor acts in video clips and
then physically practice the observed motor acts to the best of their
ability10.
Previous meta-analyses found that, compared with control interventions,
AOT had significant small-to-moderate effects on arm and hand motor
impairment and motor function11,12 and moderate-to-large effects on functional independence in basic activities of daily living11. Similarly, MT had significant medium effects on arm and hand motor impairment and motor function9,13,14 and small-to-moderate effects on functional independence in basic activities of daily living9,14, respectively.
Nevertheless,
the use of a mirror box or a plain mirror in conventional MT may cause
imbalances in trunk control and weight shifting, and a weak sense of
body ownership, and the diversity of motor movements and tasks is
limited15,16.
Moreover, the pre-recorded video clips of AOT and the reflected visual
illusions of MT in a mirror or mirror box may constrain the variety of
therapeutic movements and functional tasks. In AOT, the pre-recorded
video clips, especially those of functional tasks, may not be suitable
for each individual patient’s needs; in MT, the limited space of the
mirror box or the size of the mirror may restrict types of therapeutic
tasks that the patients can practice.
Given the current advances
in digital imaging technology, real-time video-captured images and
computer-mediated visual feedback and stimuli have been developed and
widely used in stroke rehabilitation17,18,19,20,21,22,23.
Recently, some studies have recorded movements executed mainly by the
non-affected hand of patients, immediately transformed the actions of
the non-affected hand, and presented them on a screen or in goggles via
cameras, webcams, or virtual reality technology17,19,21,23,24,25.
This approach using real-time video-captured images broadens the
diversity of movements and functional tasks and allows the users to
record individual videos by themselves, which helps to overcome some
limitations of conventional MT and AOT. These studies have also
demonstrated the benefits of these devices or systems in improving
upper-limb motor impairments in patients with stroke. Previous studies
have found that computer-mediated visual illusions and real mirrored
images produce similar degrees of neural activation16,26.
Thus, computer-mediated visual feedback and stimuli (e.g., images or
videos) may strengthen the clinical utility of MT and AOT.
Nowadays,
for patients with stroke, computerized or digital MT devices focusing
on upper-limb training have been widely developed with different
technologies, such as digital imaging systems25, augmented reflection technology19, virtual-reality based equipment23,24, and camera-based mirror visual feedback17.
These devices have the following individual advantages over
conventional MT: (1) They minimize the tension of the cervical posture,
asymmetry of the head and trunk, and weight shifting while the reflected
images are viewed on a screen or in goggles17,19,21,23,25; (2) they increase the possibility of executing asymmetrical and reciprocal upper-limb movements21,25 or broadening the range of motion exercise and simulated real-life tasks23,24;
and (3) they provide more vivid and convincing visual illusions when
the reflected movements of the non-affected hand are directly
superimposed on the affected hand on a computer screen17,19. In addition, some of them demonstrate clinical feasibility in stroke rehabilitation17,19,21,23. Although the space for performing all types of upper-limb movements or functional tasks17 may still be restricted or insufficient, computerized or digital MT devices show apparent promise.
With
the evolution of digital imaging technology, it is now possible to
extend and integrate the concepts of the two observational types of
motor learning, conventional MT and AOT, to create a novel
system/interface for wider clinical application. Integrating two
effective and promising rehabilitation therapies, AOT and MT, into one
digital system to achieve a more eclectic approach is needed for
research and clinical use. This study aimed (1) to develop a new
multi-mode stroke rehabilitation (MSR) system integrating digital AOT
and MT and (2) to test the usability of this new system.
