Therapies For Low Bone Mineral Density In Children With Cerebral Palsy
Though most people associate osteoporosis with elderly populations, low bone mineral density (BMD) has its roots in childhood. While not inherently a disease, low BMD, especially in childhood, increases a person’s risk of acquiring osteoporosis later in life. Low BMD is characterized by decreased bone density which, in turn, increases the risk of various negative consequences like fracturing a bone. In adults, osteoporosis is diagnosed with a T-score, or a report of bone health, of less than or equal to -2. 5, with -1. 0 being considered healthy. In children however, evaluations and treatments for low BMD are still not well-defined. Diagnosis in children requires a clinically significant fracture history and BMD Z-scores less than -2. 0 when adjusted for age, gender, and body size (Houlihan & Stevenson, 2010). While many different things can cause low BMD in children, I will be focusing on pediatric BMD in children with Cerebral Palsy (CP).
CP refers to a group of permanent neurological disorders that arise due to damage or abnormalities during development of the cerebral cortex, and, in developed countries, is estimated to affect two to three individuals per 1,000 births. In fact, CP affects the majority of children suffering from a physical disability. The cause of CP is often attributed to the abnormal development of the brain while in utero or shortly after birth. It is, however, possible for brain damage occurring within the first months or years of life to lead to CP. For many children, the specific cause of CP is unknown. While CP is not necessarily a hereditary disorder, genetics can predispose a person to CP and genetic abnormalities can negatively affect brain development. CP affects each individual differently, with symptoms ranging from weakness in one or more limb to seizures or abnormal physical sensations. One universal symptom of CP is difficulty controlling movement due to cerebral cortex abnormalities. As each case of CP and the symptoms that accompany it is unique, it is essential to define each individual’s functional abilities with an established scale to set movement goals and aid treatment. Children on the most severe ends of these scales are labeled non-ambulatory, meaning they are unable to walk. These children present unique clinical challenges, particularly in respect to BMD. Non-ambulatory children in particular are at greater risk for low BMD, but some research has shown that even ambulatory children with mild CP have a lower BMD than children with no CP in specific skeletal regions. Twenty percent of all children with CP sustain a femoral fracture at some point in their lifetime.
In an attempt to increase the Quality of Life (QoL) in individuals living with CP, researchers have explored many treatment options. Current treatments include therapy, medication, and visitations to a specialist. For example, in an effort to optimize motor training for individuals living with CP, following a physiotherapy regimen that is intensive yet not tiring helps strengthen motor skills and optimize motor training. For non-ambulatory children, one possible facet of a treatment plan includes passive exercise or passive loading.
Although there are significant benefits to attending therapy sessions, physical activity levels of children with CP are often lower outside of structured therapy sessions. In fact, half of leisure time is spent doing sedentary activities such as watching TV, listening to music, reading, and arts and crafts (Zbogar et al. , 2016). Another important aspect of leisure time for children with CP is play. As defined by Missiuna et al, “play is a complex, multifaceted behavior that is relatively easy to observe and describe but difficult to define theoretically”. In this study, the authors argue children who are limited by their physical disability are not adequately engaged in play. This can result in the development of poor social skills, lack of motivation, and increased dependence. Thus, engaging children with CP in home-based rehabilitation programs can provide the support needed to increase play, involvement, and QoL.
Living with a disability often subjects individuals to a great deal of discrimination. Often times, their QoL suffers due to this discrimination. While it is unlikely that there are enough resources to teach every human the important role individuals with disabilities play in our society, and thus, help alleviate some aspects of discrimination, it is likely that we can help improve QoL in another way. In populations of both individuals with and without disabilities, one effective way to increase QoL is through exercise. The following paper explores the importance of BMD in populations with CP and the efficacy of both active exercise and passive exercise as treatment methods for children with low BMD due to CP.
Cerebral Palsy
For most children, the exact cause of CP is unknown. This is especially true for children with congenital CP, or, children who were born with CP. According to the Centers for Disease Control (CDC), congenital CP makes up 85-90% of total CP cases, while acquired CP, or CP that occurs via brain damage 28 days or more postnatally, makes up the remaining cases (CDC, 2018). Acquired CP is typically associated with postnatal infections such as meningitis but can also be caused by traumatic head injuries or abnormal blood flow to the developing brain.
Types of Cerebral Palsy
As the causes of CP vary greatly, so do the symptoms. Today, doctors classify children with CP into one of four main categories, based on the main type of movement disorder. Spastic CP is the most common type, affecting about 80% of CP cases. Individuals with spastic CP have increased muscle tone, resulting in stiff muscles and awkward movements. Spastic diplegia is stiffness in the legs, hemiplegia is stiffness in only one side of the body, while quadriplegia affects the entire body and is the most severe form of spasticity. The second category of CP is dyskinetic CP, which is categorized by a person’s inability to control movements of limbs, but in severe forms can also affect the face and tongue. The muscle tone of a person with dyskinetic CP can vary from too tight to too loose from day to day, or even within a single day. The next unique category of CP is ataxic CP, in which a person has problems with balance, coordination, and fine motor control. The final type of CP is mixed CP, in which a person displays symptoms of more than one type of CP, with the most common combination being spastic-dyskinetic. Motor and functional ability of children with CP is also affected by the comorbidity of diseases like epilepsy, as well as vision, hearing, speech, or intellectual impairments, or dependence on external devices such as feeding tubes.
Quality of Life
Even minor motor or intellectual impairments raises questions about an individual’s QoL. As QoL is a measure of the person’s view of themselves and their experiences, measuring QoL is dependent on self-report. This can be challenging to measure in children with CP, as they may not be able to understand or respond to interviewers due to comorbid intellectual disability or difficulties verbalizing. Through semi-structured interviews of 18 parents with children with CP, Davis et al. (2017) identified 11 domains of QoL, including variety of activity and movement or physical activity. Based on these findings, future studies should aim to demonstrate the significance of these QoL domains.
Children’s ability to interact and play with their peers is closely tied to several domains of QoL, including communication, variety of activity, movement or physical activity, and physical health. Sport participation provides opportunities to interact with groups of peers and participate in physical activity, and can increase self-esteem, fitness, confidence, and QoL. However, sport programs with modifications for children with disabilities can be both expensive and difficult to find. Due to the unique musculoskeletal development and muscular loading in CP, even ambulatory children with CP have lower BMD in specific skeletal regions when compared to healthy controls. This low BMD increases risk of fractures, especially in the limbs for children with CP which can, in turn, decrease a child’s QoL. Physical activity outside of sport participation could be implemented as a method of increasing or maintaining a healthy BMD while simultaneously playing a positive role in a child’s QoL.
Bone Mineral Density and Measurement
Due to increased fracture risk and potential degradation in QoL, BMD is an important measure to assess in children with CP. BMD as reported by the National Osteoporosis Foundation is the amount of bone mineral in bone tissue and is measured in grams per cubic centimeter. Low BMD is defined as being lower than an average BMD but not quite low enough to be considered osteoporosis. Having low BMD is particularly concerning as it is a precursor to osteoporosis and significantly increases the likelihood of fracturing a bone. Osteoporosis is the weakening of bone, usually due to the loss of bone material, failure to make enough bone, or both occurring simultaneously. This leads to the development of large gaps between the pores in bone, making them porous, frail, and more susceptible to fracture.
Bone Mineral Density and Cerebral Palsy
In non-ambulatory children with moderate to severe CP, decreased BMD is ubiquitous across the population, especially after age ten. In fact, CP is the most common childhood condition that is correlated to the advancement of osteoporosis. Due to the compromising nature of BMD, children with CP may sustain fractures after minor incidents or injuries. Because these children are more susceptible to low bone mineralization, clinicians must construct a plan to prevent further loss of bone density and prevent the onset of osteoporosis. In order to prevent the decline in the QoL for children with CP, physicians must perform reliable and valid bone scans to evaluate the density and integrity of the bone.
Bone Mineral Density Assessment
When assessing BMD, most physicians recommend scanning the anatomical areas of the lumbar spine, distal femur, hips, and/or proximal tibia. Focus on these regions is due to the fact that these are the locations that have the highest risk of fracturing. For instance, the distal femur appears to be the best site for children with CP, since it is the most common site of fractures and has a vital role in ambulation.
For individuals who are already at a higher risk of reduced BMD such as children with CP, it is crucial to utilize accurate and efficient imaging mechanisms. According to the PDC, the use of Dual X-Ray Absorptiometry (DXA) on the lumbar spine is recommended when evaluating the BMD in pediatric patients. Through the use of two rays with different energies, DXA scans the bon region and produces an image of the bone in a way that allows for BMD to be analyzed. Another common type of imaging is pQCT, which takes high resolution volumetric images of peripheral parts of the body and measures both the bone density and bone architecture of the trabecular and cortical bones. When evaluating children with CP, understanding the risk factors of low BMD as well as the importance of imaging techniques allows the physician to make informed decisions on the best scan to use for the given skeletal area and volume.
Active Exercise
Physical activity and exercise have been known to improve one’s health for many years. Health and QoL are associated with high physical activity levels, while low physical activity levels are linked to obesity, type II diabetes, and other negative health conditions. Physical activity can consist of either active exercise or passive exercise. Active exercise is the voluntary movement of the body while contracting and relaxing muscles in response to a load. These activities have been shown to have a critical role in bone health in adults and children, in both humans and other animals. Many different types of active exercise have been shown to greatly improve BMD. These include high-impact training, resistance training, weight bearing exercise, cycling, and other ambulatory activities. While high-impact and resistance training have been shown to improve BMD, many children do not participate in these types of training. Ambulatory activities, like sports, are a socially relevant way for children with or without disabilities to get physical activity. However, many children with CP have very limited participation due to restricted mobility and accessibility. Because of this, less physically demanding activities such as weight bearing activities and home-based cycling programs offer an opportunity for individuals with CP to increase BMD through active exercise.
One study that examined the associations between BMD and weight bearing activities in children with CP found that the BMD for children with CP had a baseline BMD that was significantly lower than their healthier counterparts in the control group. The study also found that participants who went through a program that included more than two hours of assisted standing for at least five days per week showed a 3. 61% increase in BMD while participants who went through a program that included 20 minutes of assisted standing for at least two days per week showed a 4. 69% decrease in BMD. Another study exploring the relationship between BMD and cycling found that a 12-week home based virtual cycling training program significantly increased the BMD of the distal femur as well as strengthened the knee extensor and flexor muscles.
While these forms of active exercise have been shown to have a positive effect on the BMD of individuals with CP, it is important to realize that this form of therapy only works on individuals who can control their own movements. For individuals with more severe motor movement difficulties due to CP, a possible treatment method is known as passive exercise.
Passive Exercise
A wide range of the global population experience common diseases, disorders, or have experienced injuries that have left them unable to perform or control muscular movements. Without the ability to move and/or control their own muscles, this population often relies on the help of others in the form of therapy and are sometimes even fully dependent on the help of others to perform daily activities crucial to survival. A multitude of studies have shown people who fall under these categories of limited movement abilities can benefit greatly from therapy. Because some individuals lack the complete ability to move parts of their body, including some individuals with CP, a treatment method more inclusive than active exercise should be investigated.
An inclusive treatment option that could be utilized by various individuals with little to no gross motor movement abilities is known as passive exercise. In contrast to active exercise, which involves an individual's own physical exertion to perform a particular movement, passive exercise requires mechanical assistance via another individual or a machine so the individual performing a movement does not have to exert any energy of their own. Passive exercise is thought of as an inclusive treatment because it offers individuals who lack the ability to move their muscles or control their muscles a treatment method tailored toward their lack of motor abilities. One treatment method under the passive exercise term includes passive mechanical loading techniques. Also referred to as passive standing techniques, passive mechanical loading techniques offer treatment opportunities to individuals with CP who have limited movement. Passive mechanical loading techniques often require a participant to be strapped into dynamic standers, a contraption that positions the individual into a fixed standing position. The footplates on which the participants place their feet in the dynamic stander provide a force to the lower limbs similar to that during the natural walking gait. In a study of four preschool-aged children with severe CP, researchers found that standing in a static stander machine resulted in a maintained BMD level while standing in a dynamic stander where foot pedals fluctuated up and down by 2 cm to replicate the motion of walking resulted in an increase in BMD. Another study utilizing a pneumatic actuator followed nine children in either the passive load bearing condition or the dynamic load bearing condition for 15 months finding that non-ambulatory individuals in the dynamic load bearing group significantly increased BMD while non-ambulatory individuals in the passive load bearing group maintained BMD levels. Despite the limits to the experimental design of both Gudjonsdottir and Damcott’s study, mainly their sample size, both offer a good starting point for which future studies can build on.
Conclusion
CP is more often than not a congenital disorder that can be classified into four categories: spastic CP which results in stiff muscles, dyskinetic CP which results in uncontrollable motor movements, ataxic CP which results in poor balance or coordination, and mixed CP which results in the combination of any of the other forms of CP. With no identifiable cause, current efforts should be placed on improving the QoL of children living with CP. In this specific demographic, BMD levels can be seen as being partially synonymous with QoL because, QoL greatly increases when a child is at less risk of osteoporosis or fracturing their bones. As this paper has explored, exercise can be utilized as a treatment option for children who often lose BMD as a result of CP. Just as every case of CP is unique, every treatment method should be too. While active exercise proved to be the most effective mode of treatment for increasing BMD in children with CP, it is not reasonable to ask non-ambulatory children with CP to perform active exercise. For children with CP who are non-ambulatory, passive exercise offers a more feasible treatment method that has been shown to maintain BMD levels in the aforementioned population. Increasing the QoL of any individual in our society should be a goal of all of ours. When we allow individuals to pursue a better life, we allow them to become active contributors to the betterment of society.
