Effects of mirror therapy on the motor and functional recovery of post-stroke paretic upper limbs : a systematic review

| After a stroke upper limbs may display motor deficits that could lead to functional disability. Mirror therapy (MT) is a therapeutic tool in the rehabilitation of upper limbs (UL). This study aimed to bring together evidence to show the main effects of MT in the motor recovery of paretic upper limbs after a stroke. An electronic search on the Lilacs, Scielo, PubMed, PEDro and ScienceDirect databases was performed, in accordance with the inclusion criteria: clinical trials, in which individuals should have had a stroke of any etiology and in any stage of recovery, with UL impairment, published in full in journals indexed in those databases, between 2010 and 2015, in English or Portuguese, using MT for the rehabilitation of these patients’ UL, with motor function and functional independence as main outcomes. The remaining articles were evaluated with the PEDro scale to assign their methodological quality a score. Thirteen clinical studies evaluated the effects of MT in the motor function and functional independence of the upper limbs after a stroke. Fugl-Meyer scale and the Functional Independence Measure were frequently used in the studies, which showed that MT is efficient in upper limb motor recovery and functional independence, Fisioter Pesqui. 2016;23(4):431-438 432 especially concerning transferring and self-care. Regarding the methodological evaluation, the articles were considered as having moderate or high quality. In conclusion, MT promotes significant improvement of the motor function and functional independence of paretic upper limbs after a stroke, regardless of the time elapsed after the encephalic lesion.

Effects of mirror therapy on the motor and functional recovery of post-stroke paretic upper limbs: a systematic review Efeitos da terapia espelho na recuperação motora e funcional do membro superior com paresia pós-AVC: uma revisão sistemática Los efectos de la terapia del espejo en la rehabilitación motora y funcional del miembro superior con paresia pos-ACV: revisión sistemática nos quesitos transferências e autocuidados.Os artigos foram considerados de moderada a alta qualidade metodológica.

INTRODUCTION
The Cerebral Vascular Accident (CVA) is defined as a hemorrhagic or ischemic vascular dysfunction that can reach different regions of the brain and result in neurological damage and sensorimotor deficits.The most frequent consequences are hemiparesis or hemiplegia and sensitivity and coordination disorders 1 .The upper limbs (UL) are compromised due to weakness and/ or spasticity 2 .Such deficits may lead to the restriction of activities of daily living (ADL) and to functional disabilities, restricting the patient's social participation 3 .
The neurorehabilitation of the UL with paresis after a stroke includes methods and techniques aimed at the reduction of functional impairments and recovery of the individual's abilities so that he can achieve the highest degree of functional independence possible.Mirror Therapy (MT), one of these methods, uses visual feedback to stimulate neuronal plasticity in the primary motor area and cortical reorganization, the mechanisms responsible for the therapeutic results obtained by this therapy 4,5 .In addition, other mechanisms have been suggested, such as the stimulating of certain areas of the primary motor cortex and the activation of mirror neurons, induced by the MT 6,7 .
The technique consists in the performing of bimanual activities with the use of a box with an one-sided mirror placed in the sagittal plane (in relation to the patient).This way, the patient visualizes the reflection of his healthy upper limb as if it were the impaired member 8 .For the application of the technique, two protocols are proposed, namely, the performing of isolated movements of the shoulders, elbows, wrists and fingers, or functional tasks of the upper limbs 9,10 .
Although there are a few studies which assess the effects of MT, as indicated by the reviews of Toh and Fong 11 and Thieme et al. 12 , more homogenous clinical studies with larger samples and with improved methodological quality have been carried out in recent years.These studies have more robust results, which can support the use of the technique in the functional recovery of patients with stroke sequelae.The aim of this study was to gather evidence that could show the effects of MT on the motor and functional recovery of upper limbs with post-stroke paresis.

METHODOLOGY
The present study is a systematic review of the literature.A search in the Scielo, Lilacs, Pubmed, PEDro and ScienceDirect electronic databases was held in the period from September to October 2015, using an advanced integrative search strategy, with the combination of the four terms connected by the Boolean operator "and".The following search terms were used, in Portuguese: Terapia Espelho, Reabilitação, Membro Superior, Acidente Vascular Cerebral and in English: Mirror Therapy, Rehabilitation, Upper Limb, Stroke.
The search for and selection of the articles was performed by four researchers and held according to the following inclusion criteria: randomized controlled trials, in which individuals above 18 years old were assigned a clinical diagnosis of stroke of any etiology and at any stage, and with sequelae in the upper limbs; studies published in full in scientific journals indexed in the aforementioned databases, in English and Portuguese, with publication date between 2010 and 2015 and which used MT for the rehabilitation of the UL of these patients, having as outcomes motor function and functional independence.Articles identified as duplicates were excluded.The proceedings of this research were summarized in accordance with the PRISMA criteria 13 and can be seen in Figure 1.
Thus, the final sample of this review consisted of 13 articles, which had their methodological quality evaluated in accordance with the PEDro scale 14 and were assessed independently by two researchers.In the absence of consensus, a new evaluation was carried out by a third party.This scale is made up of eleven items, each item is equivalent to one point when the criterion is obeyed, except item one, which should not be assigned a score.Thus, the score ranges from zero to ten.The items are: eligibility criteria, random allocation, secret allocation, homogeneity of the sample, blind sample, blind therapist, blind appraiser, outcome in 85% of the subjects initially distributed among the groups, treatment or control according to allocation, statistical comparison between the groups for at least one key outcome and precision and variability measures for at least one key outcome.

RESULTS
Thirteen clinical studies with a total sample of 368 individuals were part of this research.These studies were characterized according to the analyzed variables, type of intervention and main results, as shown in Table 1.
Generally these studies evaluate motor function, sensory function and functional independence.A few of them included some method for measuring strength, muscle spasticity and kinematics, in addition to electroencephalographic and functional magnetic resonance analyses.The variables which were most studied were the motor function of paretic UL, through the Fugl-Meyer (FMS) (eight studies), Brunnstrom Motor Recovery Stage (BMRS) (four studies), Manual Function Test (MFT) (three studies) and Box and Block Test (BBT) (four studies) scales.Functional independence was evaluated through the Functional Independence Measure (FIM) (four studies).Most of these studies demonstrated the effectiveness of MT on the motor recovery of UL, compared to the control therapy.
In general terms, it was observed that MT significantly improves the gross and fine motor function of the paretic UL.With regard to functional independence, it was observed that the MT provided significant changes especially concerning the transfer and self-care items of the FIM.The articles were grouped according to their methodological quality, analyzed through the PEDro scale.The results of this analysis can be seen in Table 2.

DISCUSSION
The literature includes some studies that support the use of MT in post-stroke rehabilitation, although many of them are inconclusive 11,12 .However, researches involving MT have evolved over the past years, acquiring better methodological quality.
The studies found in this review assessed individuals in the acute and chronic phases post-stroke and showed similar effects concerning the effectiveness of MT on the recovery of the motor function (the acute phase being understood as the period of up to six months after a stroke and the chronic phase the period that follows).Two of these studies 16,21 did not present significant results, when compared to the control therapy.However, in the study by Medeiros et al. 21the absence of effects can be attributed to the small sample of only six patients, not being thus possible to generalize their results, and to the fact that these researchers compared two groups that used different MT protocols.On the other hand, the study by Thieme et al. 16 used relatively low frequency and intensity, with less than 10 total hours of MT.
The studies involving functional independence assessed patients predominantly in the chronic phase.As an exception, the study by Thieme et al. 16 evaluated patients in the acute phase, with the Barthel Index (BI), but showed no significant result.On the other hand, Invernizzi et al. 17 assessed functional independence with FIM and showed statistically significant results in the acute phase.The studies that evaluated functional independence in patients in the chronic phase, with FIM 20,21,26 , observed statistically significant improvement of functional independence after the intervention.
The studies that used FIM observed statistically significant improvement especially in the categories of transfer and self-care 17,20,21,26 .Two studies evaluated functional independence with the BI and ABILHAND 16,18 , however they did not report significant difference between the experimental and control groups.Some methodological limitations may explain this absence of difference.Firstly, the sample size was relatively small to detect the size of the effect, with a high rate of loss of the sample in one of them 16 .Secondly, the first study did not use blinding in the evaluation through the BI, which may have lead to some bias; also, it used patients in the subacute phase in the sample, with severe distal impairment, and admittedly poor prognosis for recovery 16 .Additionally, the ABILHAND questionnaire evaluates the patient's difficulty in performing ADL 23 which require bimanual manipulation, thus it is possible that the effects on the motor and kinematic functions observed in that same study 18 were not reflected in activities that require simultaneous and joint use of the hands and therefore require specific training.
The most widely used instruments for motor function were FMS 10,15,18,19,[22][23][24][25] , BMRS 15,19,23,24 , MFT 15,19,26 and BBT 19,20,23,25 , which assess the gross and fine motor function of the UL.In general, the studies that used these tests showed statistically significant results, with improvement of the group that received MT, in comparison to the control group.Some studies used the Action Research Arm Test, the Jebsen-Taylor Test and the Motricity Index instruments and also verified improvements in the experimental group, compared to the control group 17,20,22,23 .
Some of the researches also evaluated the sensorial function 16,18 and aspects such as prehension 25 , kynematics 18 and spasticy 16,20 , with varied instruments.In these studies MT had significant results, with the exception of the studies by Lin et al. 20 and Thieme et al. 16 , who observed non-significant spasticity improvement and spasticity increase in the finger flexor muscles, respectively, after the intervention.There was disparity in the results of the studies that use different assessment instruments for the same outcome, while some showed significant results, others did not show any statistically significant clinical improvement.This may be explained by the variety of the aspects that are evaluated within each test, mainly in the scales that assess together the gross and fine motor function based on various movements and in different ways.
Only two of the 13 studies evaluated the maintenance of the effects of MT, with a six-month follow-up.Both reported that there was no maintenance of the effects obtained with MT after six months 10,18 .
Three intervention protocols with MT have been identified, namely, isolated bilateral movements (five studies), unilateral or bilateral functional tasks (three studies) or the combination of the two protocols (four studies).In relation to the improvement of motor function and functional independence, there was improvement of these outcomes with each of the protocols.In two studies, two modalities of MT were compared with each other.The study by Paik et al. 22 compared MT with isolated movements with MT with functional tasks.Improvement was observed in both groups, with no significant difference regarding motor function.The study by Medeiros et al. 21, who made the same comparison, observed statistically significant improvement in the total FIM and cognition scores, without reporting, however, difference between the groups.In the study by Samuelkamaleshkumar et al. 23 MT and conventional rehabilitation were compared.They found that there was significant improvement of manual dexterity (BBT), motor recovery of the hands and arms (assessed through BMRS) and of the motor function (assessed through FSM) compared to the control group.
Most of them used an intervention period of four to six weeks, with a frequency of five times a week, in 30-minute sessions.In what concerns series and repetitions, there was not much homogeneity, with some studies ranging from one to four series of 10 to 100 repetitions for each movement or motor standard used.
In the assessment of methodological quality (through the PEDro scale) seven studies had scores between 8 and 10 (good quality) and six had scores from 5 to 7 (moderate quality).The biggest limitation of the works with moderate quality was the absence of blinding (or information about the blinding) on the part of the appraisers, researchers and participants.

CONCLUSION
It is concluded that MT promotes the clinically significant improvement of the motor function and functional independence of the upper limb with poststroke paresis, regardless of the recovery phase.Such improvements, highlighted by studies of moderate to high methodological quality, strengthen the indication of MT as therapeutic measure in rehabilitation.The effects of MT on functional independence in the acute phase are not fully established yet, therefore, it becomes necessary to carry out a greater number of studies with good methodological quality, to test this hypothesis.In addition, studies that investigate the duration of the effects of the improvement in the motor function of the UL and in functional independence through the monitoring of these patients after the end of the treatment are necessary.The only two studies that conducted the monitoring after the intervention showed that the effects remained.

IdentificationFigure 1 .
Figure1.Flowchart of search procedures in the databases, based on the PRISMA group (2009)13

Table 1 . Continuation Table 2 .
Methodological evaluation of the studies in accordance with the PEDro scale.