Robot-Assisted Mirror Therapy in the Rehabilitation of Hemiparetic Cerebral Palsy

EFFECT OF ROBOT-ASSISTED MIRROR THERAPY ON UPPER EXTREMITY FUNCTIONS IN HEMIPARETIC CEREBRAL PALSY REHABILITATION

-1 . INTRODUCTION :

Cerebral palsy (CP) is a group of permanent disorders of movement and posture caused by non-progressive disturbances in the developing brain. It has a worldwide prevalence of 2 to 3 per 1,000 live births and is the most common cause of motor disability in children. Spastic CP accounts for 85 to 91 percent of all cases, and hemiplegia is its most common subtype, accounting for approximately 38 percent of cases.

Hemiplegic cerebral palsy is characterized by unilateral motor and sensory impairments resulting from damage to the motor cortex and corticospinal tract. In nearly half of the cases, the upper limbs-particularly the hands-are more severely affected than the lower limbs. Patients typically present with limited upper extremity range of motion, increased muscle tone, muscle weakness, impaired isolated finger movements, and reduced grip function. Collectively, these symptoms adversely affect the performance of activities of daily living and participation in social life, potentially leading to the learned non-use of the affected limb and further impairment of motor function.

Various rehabilitation techniques have been developed to improve upper extremity function and performance in activities of daily living. Mirror therapy (MT), developed by Ramachandran, is one such approach. MT is based on the mirror neuron system, in which neurons in the premotor cortex and inferior parietal cortex are activated during both the observation and the execution of a movement. This technique involves placing a mirror between the unaffected and affected limbs. The mirror creates a visual illusion in which the movement of the unaffected limb is perceived as that of the affected limb. This illusion activates the mirror neuron system, which plays a key role in both action observation and action execution.

The mirror neuron system (MNS) encompasses a network of brain regions, including the ventral premotor cortex (area F5), supplementary motor area (SMA), inferior frontal gyrus (IFG), and inferior parietal lobule (IPL). This system plays a crucial role in action recognition and motor learning by enabling the observation and internal simulation of motor actions.

Investigators have utilized mirror therapy to address various unilateral neurological and orthopedic conditions, including pain and motor impairments. Most studies have focused on adult patients with post-stroke hemiparesis, demonstrating that MT effectively enhances motor cortex activation, leading to improvements in upper extremity motor function and overall functional performance.

Mirror therapy is a promising, non-invasive, low-cost intervention for children with hemiparetic cerebral palsy. Studies have shown that mirror therapy can modulate cortical activity through visual feedback in children with spastic hemiparetic cerebral palsy. This modulation promotes functional improvement and partially compensates for the lack of age-appropriate sensorimotor stimulation, thereby enhancing upper extremity function. Only a limited number of studies have investigated the use of mirror therapy in children with hemiparetic cerebral palsy, either as a standalone intervention or as an adjunct to other therapeutic approaches. Reported benefits include improvements in grasp and pinch strength, upper extremity function, gross motor skills, bimanual performance, and performance in activities of daily living. However, evidence regarding its effects on participation and quality of life within the framework of the International Classification of Functioning, Disability and Health for Children and Youth (ICF-CY), remains inconclusive.

Evidence supporting the use of mirror therapy in children with cerebral palsy remains limited. The need for more methodologically rigorous studies specifically targeting this population has been emphasized. In addition, further research evaluating performance in activities of daily living and hand function has been recommended. Recent evidence suggests that combined therapeutic interventions have the potential to enhance recovery in individuals with moderate to severe upper extremity dysfunction following stroke. In this context, several researchers have combined mirror therapy with wearable robotic devices, an approach known as robot-assisted mirror therapy (RAT). Unlike conventional mirror therapy (MT), which provides only visual feedback, robot-assisted mirror therapy (RAT) generates both visual and somatosensory feedback by inducing passive movement of the affected limb. This process provides proprioceptive input to the sensory cortex, thereby facilitating neuroplasticity and functional recovery of the affected upper extremity. Evidence suggests that integrating mirror therapy with a wearable robotic glove may enhance neural activity in the contralateral motor cortex and promote a more balanced pattern of interhemispheric cortical activation during grasping tasks in participants following stroke. Similarly, preliminary evidence suggests that robot-assisted mirror therapy (RAT) may lead to greater improvements in motor function than conventional mirror therapy (MT). Although RAT has been shown to be a feasible treatment approach, its neurological effects, particularly in pediatric populations, remain unclear, and its efficacy relative to conventional MT has yet to be established. Further studies are needed to determine its effects on functional recovery.

Therefore, the aim of this study is to investigate the effects of robot-assisted mirror therapy on spasticity, grip strength, hand function, selective motor control, bimanual performance, participation in activities of daily living, and quality of life in children with spastic hemiparetic cerebral palsy, and to compare these outcomes with those achieved through conventional mirror therapy.

-2. METHOD :

The study was approved by the Non-Interventional Research Ethics Committee of Istanbul Medipol University (Approval No. E-10840098-202.3.02-8027) on December 21, 2024.

The study will include 20 children aged 6-17 years with hemiparetic cerebral palsy who are receiving rehabilitation at the Dilbade Special Education and Rehabilitation Center and meet the inclusion criteria. Written informed consent will be obtained from the parents or legal guardians of all participants after they have been fully informed about the study. In addition, all children will receive age-appropriate information about the study before participation.

-2.1. Demographic data :

The following demographic and clinical characteristics will be recorded: age, sex, height, weight, body mass index (BMI), affected side, gestational age at birth, mode of delivery, history of neonatal intensive care unit (NICU) admission, orthosis use and duration of use, comorbidities, history of seizures, previous botulinum toxin injections and surgical interventions, duration and frequency of physiotherapy, and Gross Motor Function Classification System (GMFCS), Manual Ability Classification System (MACS), and Communication Function Classification System (CFCS) levels.

-2.2. Randomization and Intervention Groups :

After baseline demographic data are collected and the initial assessments (T0) are completed, all participants who meet the inclusion criteria will receive individualized neurodevelopmental treatment for 6 weeks, administered twice weekly, with each session lasting 40 minutes. At the end of this treatment period, the second assessment (T1) will be performed. Following the T1 assessment, a 2-week interval will be observed. At the end of this period, each participant will be assigned a unique identification number and allocated equally to one of the two groups using the Randomizer software, with stratified randomization based on age and MACS level. This method will help ensure balance between the groups in terms of demographic and clinical characteristics. Randomization will be performed by a staff member working at the clinic who is not otherwise involved in the study.

• Group 1 (RAT) (n = 10): Robot-assisted mirror therapy group
• Group 2 (MT) (n = 10): Mirror therapy group

Both groups will be assessed before the intervention (T2) and after the intervention (T3).

-2.3. Intervention Methods for Groups :

Following completion of the neurodevelopmental treatment administered up to the T1 assessment, participants in both groups will receive an additional intervention over a 6-week period. The intervention will be administered twice weekly, with each session lasting 30 minutes.

-2.3.1. Robot-assisted mirror therapy group :

The participant will be seated in an ergonomic chair at a table, with the hips and knees flexed to 90 degrees. The unaffected upper limb will be positioned in front of a Metafiz brand mirror placed on the table. After the affected upper limb is positioned behind the mirror, a robotic glove will be fitted to the participant's affected hand. The FosilTech robotic glove (FosilTech, Turkey) used in this study is similar to a robotic glove model previously reported to be suitable and valid for use in pediatric robotic rehabilitation. The participant will perform predetermined exercises by observing the mirror reflection of movements performed by the unaffected limb. Simultaneously, behind the mirror, passive movements symmetrical to those performed by the unaffected limb will be induced in the affected limb using a robotic glove. This approach aims to provide somatosensory stimulation to the affected limb, thereby promoting activation of the affected cerebral hemisphere.

-2.3.2. Mirror therapy group :

While seated in an ergonomic chair at a table, with the hips and knees flexed to 90 degrees, the participant's unaffected upper limb will be positioned in front of a Metafiz-brand mirror (Metafiz, Turkey) placed on the table. After the affected upper limb is positioned behind the mirror, the participant will perform the predetermined exercises with the unaffected hand while observing its reflection in the mirror. No intervention will be applied to the affected limb.

• 2.3.3. Exercise Protocol for Robot-Assisted Mirror Therapy and Mirror Therapy
• Exercise duration is planned as 30 minutes.
• The first 10 minutes of exercises will be for joint movements and grip, and the last 20 minutes will be for activity.
• Each given exercise will be done for 1 minute :

MCP joint flexion and extension, thumb flexion and extension, pinch grip, tripod pinch, hook grasp, spherical grasp, lateral pinch, wrist flexion and extension with the fingers extended, wrist flexion and extension with the fingers flexed, thumb opposition

-Each given exercise will be done for 2 minutes :

Rolling a cylinder (wrist and finger extension), grasping and releasing a ball (gross grasp and release), grasping and releasing a cup (cylindrical grasp), grasping and releasing objects using tripod tongs (tripod pinch), picking up small objects (pinch grip), cutting toy vegetables with a toy knife (lateral pinch), placing rings (hook grasp), drawing shapes (pencil grasp), gathering a towel (finger flexion) and striking an object (wrist movements combined with finger flexion and extension)

-2.3.4. Exercise Protocol for Neurodevelopmental Treatment :

No additional treatment will be administered beyond each participant's individualized neurodevelopmental treatment (NDT) program.

The exercises included in the neurodevelopmental treatment (NDT) program will be as follows: Lower extremity and balance training will include gastrocnemius and hamstring stretching; strengthening of the evertor, dorsiflexor, quadriceps, and hip muscles; and balance exercises performed with the eyes open and closed. Upper extremity training will include biceps and wrist stretching; strengthening of the triceps, shoulder girdle, scapular, and wrist muscles; forearm supination; wrist and finger flexion and extension; gross grasp and release; and pinch, cylindrical, tripod, lateral, and hook grasp exercises.

-2.4. Assessment Methodology :

The researchers will utilize the following assessment tools to evaluate the participants :

• 1. Manual Ability Classification System (MACS)
• 2. Gross Motor Function Classification System (GMFCS)
• 3. Communication Function Classification System (CFCS)
• 4. Modified Ashworth Scale (MAS)
• 5. Selective Control of the Upper Extremity Scale (SCUES)
• 6. Jebsen-Taylor Hand Function Test (JTHFT)
• 7. Children's Hand-use Experience Questionnaire (CHEQ)
• 8. Revised Pediatric Motor Activity Log (R-PMAL)
• 9. Canadian Occupational Performance Measure (COPM)
• 10. Pediatric Outcomes Data Collection Instrument (PODCI)

At baseline, children's gross motor function, manual ability, and communication function will be classified using the Gross Motor Function Classification System (GMFCS), Manual Ability Classification System (MACS), and Communication Function Classification System (CFCS), respectively. These three classification systems will be used to determine eligibility according to the inclusion criteria, while the remaining assessment instruments will be used to evaluate the primary and secondary outcomes.

All primary and secondary outcome measures will be assessed at four time points: at baseline, before the neurodevelopmental treatment (NDT) period (T0); at the end of Week 6, after the NDT period (T1); at the end of Week 8, immediately before the 6-week combined intervention consisting of NDT plus robot-assisted mirror therapy (NDT+RAT) or NDT plus mirror therapy (NDT+MT) (T2); and at the end of Week 14, immediately after the combined intervention (T3).

-2.5. Statistical analysis :

The sample size was determined using G*Power (version 3.1). Based on a similar study, the effect size for the difference between two independent groups was calculated as d = 2.87. The power analysis indicated that a minimum of 8 participants, with at least 4 participants per group, was required with a type I error rate of 5 percent (alpha = 0.05) and a statistical power of 80 percent (1 - beta = 0.80). Although the large effect size (d = 2.87) reported by Kara et al. (2020) was used as a reference, the possibility of effect size overestimation in clinical studies was taken into consideration. Therefore, to increase the statistical power of the study and enhance the generalizability of the findings, the sample size was increased to a total of 20 participants, with 10 participants allocated to each group.

Data will be analyzed using IBM SPSS Statistics for Windows, Version 20.0 (IBM Corp., Armonk, NY, USA). For statistical analysis, the sign test, Mann-Whitney U test, and correlation analyses using Pearson's and Spearman's correlation coefficients will be used. A p-value of less than 0.05 will be considered statistically significant.