Dr Hassan Farah | The Complex Relationship between Gait and Balance in Cerebral Palsy

Dr Hassan Farah worked as a Graduate Research Assistant at the Virginia Polytechnic Institute and State University. Using novel approaches, he explored the complex connection between gait and balance in children with a particular form of cerebral palsy. Understanding how these children coordinate and move is vital to discovering new rehabilitation targets that will improve their overall strength and mobility.

The Impact of Cerebral Palsy

According to the Centers for Disease Control and Prevention in the USA, cerebral palsy (CP) is the most common motor disability in childhood, affecting around 1 in 345 children. It is thought to be possibly caused by a problem with the development of the brain whilst in the womb or damage during or shortly after birth, but in many cases, the actual cause remains unknown.

CP is a lifelong condition that affects movement and coordination between the brain and the body. There is no cure, and the severity of symptoms can vary greatly, with some individuals experiencing only minor problems whilst others are severely disabled and even wheelchair-bound.

Dr Hassan Farah at the Virginia Polytechnic Institute and State University (Virginia Tech) in the USA is advancing our knowledge about hemiparetic cerebral palsy (HCP). This particular diagnosis affects around 30% to 40% of all the children in the USA who are born with CP. Children with HCP present with an involved side of their body being weaker than the other. This affects how they distribute weight across their legs and maintain stability during standing, leading to poor posture control when trying to walk.

Having reviewed previous studies examining balance and gait, Dr Farah has worked to understand how gait and balance influence each other. He hopes the methodology behind his research can someday provide data for therapists to identify more rehabilitation targets to improve the strength of the hemiplegic side and bilateral ability (that is, movements using both sides of the body). Such changes would greatly improve the ability of affected individuals to carry out the day-to-day activities most of us take for granted – like climbing the stairs or stepping past an object that is in the way.

Achieving a Deeper Understanding

Dr Farah worked alongside Dr Stephanie DeLuca (Director of the Neuromotor Research Clinic and Associate Professor at the School of Neuroscience, Virginia Tech) and the Kevin P. Granata Biomechanics Lab on the Blacksburg campus to achieve a deeper understanding of the underlying mechanisms of standing and walking for children with HCP.

In a recent study, Dr Farah sought to better understand specifically how children with HCP anticipate gait. Since HCP causes one side of the body to be weaker than the other, the resulting asymmetry affects the child’s ability to distribute their centre of pressure evenly between their lower limbs, leading to poor posture control. This is highlighted by favouring the stronger side during balancing and a preference to begin walking (gait initiation) with their involved side that therapists have observed during treatment sessions.

He recruited three children with HCP, three age- and gender-matched typically developing children, and 12 non-matched typically developing children. Although lower than planned due to the pandemic, this sample size is consistent with the literature in this field. A simple ball-kick test was used to determine lower-limb dominance. The children were fitted with 50–60 reflective markers from their shoulders to their toes to allow a 10-camera motion capture system to track their movements while they carried out specific tasks and identify their centre of mass. Finally, force plates that the children stood on and walked across captured data about where and how pressure was distributed during standing and walking tasks.

Dr Farah hopes these novel data will help him specifically locate and track the centre of pressure and collect limb symmetry data (how stability changes through both sides of the body) during standing and walking activities in HCP. This will allow him to determine the impact of gait anticipation (the child’s expectation of their first step) on how they balance and distribute their body weight as they prepare to walk compared to when they stand still without anticipation.

Statistical analyses will also allow Dr Farah to compare the data from children with and without HCP, hopefully going some way towards filling knowledge gaps about the potential relationship between standing balance and gait anticipation. This study will provide a deep analysis of symmetry on balance and posture for children with HCP that is both novel and much needed. Therapists and researchers can then use this information to inform and develop new treatments.

‘My long-term career goal is to utilise biomechanics as a tool to define target measures for therapists to develop treatment options that are cost-effective, less risky than surgery, and ultimately more accessible to families.’

Investigating Gait Initiation

Children with HCP have a clear difference in the ability of their limbs, but researchers have not succeeded in quantifying or comparing these differences. A driving force behind this study came from conversations Dr Farah had with therapists in the Neuromotor Research Clinic, who observed that children with HCP would prefer to shift their weight to their stronger side during standing. As such, it is unknown how children with HCP initiate gait when their involved side bears the majority of their weight as the stance foot (which allows the other foot to offload when someone begins walking).

Gait initiation relies on the coordinated movement of the centre of pressure and centre of mass, but the asymmetry of HCP will impede the child’s ability to do this effectively. Dr Farah sought to determine the impact of changing the stance limb (switching between the dominant and non-dominant limb) on how the centre of pressure changes and the child’s reaction time during gait initiation. This was repeated and compared with children who are typically developing as well.

Assessing the ability of each limb in taking the role of the ‘leading’ limb as the child walks will provide a framework to allow the evaluation of how each limb performs during other types of movements, such as walking up stairs. Findings will contribute to the development of new physical therapy and rehabilitation targets that could improve the coordination of both limbs and encourage improvements in bilateral ability.

Critical Next Steps

Current treatments for CP include physical therapy and rehabilitation, orthotic devices, assistive devices and technologies, medication, and surgery. Since symptoms can vary greatly between those with HCP, treatment is not a one-size-fits-all approach. Some options, such as surgery, pose a greater risk of complications and are associated with higher costs.

Dr Farah’s long-term goal is to define targets for rehabilitation that are cost-effective, have lower risks compared to surgery, and are ultimately more accessible to the families of children with HCP. Supported by a team of experts from a wide range of specialities (from paediatric rehabilitation to biomechanics and biostatistics), the proposed research represents critical steps forward in understanding the complex relationship between gait and balance, thus improving the health outcomes for children with HCP.