HISTORICAL & CURRENT VIEW OF THE BASIS OF NDT
By Lois Bly, MA, PT
More than 40 years ago, the Bobaths introduced a treatment concept for individuals with central nervous system impairment. The concept was developed from a therapist's clinical observations. A theoretical framework for the approach was based on the common belief in the 1940s that the nervous system functions in a hierarchy. Clinical aspects of the NDT approach have grown and changed during the past 40 years. This article details the original NDT concepts, notes common misconceptions, and looks at the concept with regard to newer theoretical frameworks of nervous system functioning.
Neurodevelopmental treatment, NDT, as based on the work of Dr. Karel and Berta Bobath, heralded in the idea that children with cerebral palsy should be evaluated and treated in a framework that addressed the neurological and developmental issues of their movement disorders. This was an innovative notion in the 1940s and 1950s when movement problems were evaluated and treated by more peripheral methods of individual muscle stretching, strengthening, and re-education.
Since its conception, the Bobath philosophy has grown and developed as newer understandings of movement and movement control have emerged. Investigating new advances is much in keeping with the Bobath philosophy. The Bobaths have described their approach as "not a method but a living concept...a management." In a recent article, the Bobaths stated: "Since we began our treatment in 1943, we have been learning constantly, and experience has taught us to change our approach and our emphasis on certain aspects of the treatment." Those who embrace the Bobath/NDT philosophy today are continuing in the growth of the "living concept."
As NDT has evolved, the neurological aspects of the movement problems have continued to be stressed. However, the neurological perspectives are being increasingly viewed through the newer hypotheses concerning the nervous system. In addition, the original strict adherence to the developmental process and the role of reflexes have been further clarified and modified. Today, as we become more familiar with the sciences of motor control and motor learning, we realize that we have additional avenues through which we can try to evaluate and treat our patients' movement problems.
The NDT/Bobath approach has always been an empirical approach to the treatment of children with cerebral palsy. Mrs. Bobath developed treatment protocols and treatment techniques from her astute clinical observations. In light of these observations, Dr. Bobath researched the literature to develop a theoretical framework for the empirical data. Dr. Bobath has always introduced the neurophysiological evidence as a "working hypothesis." Today, within this framework of a working hypothesis, it is judicious for us to accept new findings in the neurosciences to help us more accurately understand our clinical observations.
The original NDT theoretical framework was developed around Jackson's, Sherrington's and Magnus' hierarchical reflex levels of the nervous system. In light of this reflex model, the Bobaths proposed their theories on a normal and abnormal postural reflex mechanism and their theories that postural reflexes were responsible for automatic changes in muscle activity. They also developed their original handling techniques of reflex inhibiting postures (RIP) and reflex inhibiting patterns. A normal postural reflex mechanism utilized the righting and equilibrium reactions of level 3 of the hierarchy, while an abnormal postural reflex mechanism, due to lack of inhibitory control from higher centers, utilized the spinal and tonic reflexes of level 1 and 2. However, in 1985 the Bobaths stated: "Because of the great variability of the above mentioned postural reactions the use of the term postural reflexes,' when applied to motor behavior of children and adults, now seems to us increasingly questionableone should rather talk about postural reactions' or responses.'"
Although we may now question the hierarchical theory of the nervous system in which the reflex was the basic structure and the use of such terminology as "postural reflex mechanism" and "reflex inhibition," we are still struck by Mrs. Bobath's perceptive clinical investigations. Through observation of each patient's movement patterns, Mrs. Bobath realized that abnormal movement patterns had to be stopped or inhibited before new patterns could be developed or facilitated. She stressed that more normal patterns were possible, but, in order to achieve them, the therapist had to have a knowledgeable, logical plan of what movement patterns needed to be facilitated.
Initially, this plan focused on inhibiting the abnormal reflexes, facilitating higher postural reactions such as righting and equilibrium and facilitating missing components of the normal motor developmental sequence. The developmental sequence was selected because the patient's movement patterns represented developmentally primitive movement patterns. In addition, the Bobaths also strongly advocated analysis of each child's movement patterns to determine what the child was using and what was missing from his or her movement patterns.
In all of their writings, the Bobaths emphasized the importance of the interaction of postural reactions and movement patterns. As a result of her careful observations, Mrs. Bobath realized that there was more to a movement than the specific "voluntary" part of the movement; each movement consisted of "automatic" background postural adjustments before and during the specific voluntary action: Movements were preceded by "postural sets" and there were constant postural adjustments with automatic changes in muscular activity and tone during each movement. She also reported that the automatic postural adjustments of children with cerebral palsy were more stereotyped and less fluid than those of normal children and adults. In addition, she noted that there were marked differences in muscle tone associated with these stereotyped movement patterns and postures, and she recognized that through specific handling techniques she could change the patient's movement patterns and muscle tone and could help him or her learn new movement patterns with more normal muscle tone.
Although the original NDT theory was established around the hierarchical model of the nervous system, the Bobaths' example of continually evaluating what was happening with the patient and of using the current neurophysiological evidence as a "working hypothesis" for the empirical clinical observations. enables NDT to evaluate the evidence and move from the hierarchical model to a currently accepted distributed control model of the nervous system.
In the distributed control model, the nervous system is viewed as being capable of initiating, anticipating and controlling movements. It is no longer viewed as a passive system controlled by sensory feedback, with the reflex as the primary component. The distributed control model also embraces functional redundancy and distributed function. In this model, the nervous system utilizes feed-forward mechanisms as well as feedback mechanisms.
As NDT addresses the empirical data of the Bobaths from this newer model, posture and movement are no longer considered to be reflex dependent, and the postural reflex mechanism is no longer considered to be a viable scheme to explain the interrelationship between movement and posture in normal and abnormal situations. It is obvious that posture cannot be restricted to feedback reflex activity. A reflex implies a stereotyped movement, which occurs through a feedback loop. If all of our postural reactions were dependent on feedback, we would be in trouble because of the time delay. It is becoming increasingly obvious that posture must be evaluated from a feed-forward as well as a feedback perspective. However that is not to say that feedback from the sensory systems is not important. Sensory feedback is especially important in learning and modification of our responses.
The research literature of today concurs that there are automatic changes in muscle activity before and during movements, and these changes do affect our posture and equilibrium. Nashner and colleagues suggest that these changes or postural adjustments are learned through interaction of three primary sensory systems: vestibular, visual, and somatosensory. Subsequently these automatic changes occur in anticipation of the movement, possibly through central programming. Thus postural reaction deficits can be approached through feed-forward as well as feedback techniques.
In treating the postural problems of children with cerebral palsy, selection and evaluation of the techniques that address each child's "true" problems is critical. Nashner et al have reported that, with children with cerebral palsy, it is important to determine whether a child's poor postural adjustments are due to sensory organization problems and/or muscle coordination problems. Unfortunately, we are limited in our testing methods. Therefore, we have to carefully evaluate each treatment technique to determine if it is working for each particular child.
Marsden et al have demonstrated that postural adjustments or postural reactions are task or context dependent. They reported that movements with similar kinematic details may have significantly different EMG readings when the goals of the movements are different. This suggests that we must treat beyond the "components of the movement" and beyond basic feedback techniques, which include moving the child to provide sensory stimulation to elicit a responsei.e. righting or equilibrium reactions.
Postural responses can be learned and elicited in a predictive or anticipatory manner. Therefore, we must incorporate the reactions into the specific skills that the child wants to and/or needs to learn to function independently. The child must be an active part of the problem solving process determining how to adjust posture to achieve his or her goal, while the therapist's hands guide the movements.
The Bobaths always supported the concept that the patient's abnormal movement patterns could be changed. They recognized that these changes could be made through specific handling techniques. They realized that abnormal movement patterns and tone had to be stopped, inhibited, prevented before new patterns could be developed. The first step in their approach, therefore, focused on isolated inhibition of abnormal movement patterns. However, they soon noticed that inhibition alone made the child passive and was not sufficient to change the patient's functional movement patterns. Thus they began using less restrictive key points of control. Key points of control are defined as parts of the body, mostly proximal, from which "patterns of abnormal activity could be inhibited, while at the same time facilitating normal movements."
Today we must still remember that inhibition alone is not sufficient to change the patient's movement patterns. The child has to be an active participator in the process. Misinterpretation of the inhibition/facilitation process in NDT has resulted in therapists spending entire treatment sessions trying to inhibit abnormal tone before they try to facilitate movements. The therapist's handling techniques must combine inhibition of abnormal movement patterns while incorporating active movement and problem-solving by the patient.
Today, from a motor learning perspective, we can suggest use of specific handling techniques of inhibition and facilitation in order to help the patient learn new motor programs for performance. A motor program is defined by Brooks as "a set of muscle commands that are structured before the motor acts begin and that can be sent to the muscles with the correct timing so that the entire sequence can be carried out in the absence of peripheral feedback." According to Schmidt, a motor program is "an abstract memory structure that is prepared in advance of the movement to be produced." The program specifies which muscles are to be used, their order of contraction, the temporal phasing relationship of the contractions, and the relative force to be applied.
Motor programs do not need feedback to be elicited, but they can utilize feedback for adaptation or regulation of the movement. Motor programs can be initiated by central processes within the nervous system to perform practiced functional tasks. Brooks suggests that programmed movements are used only after the person understands the behavioral goal for which the movements are to be used. This once again emphasizes the importance of using task-specific or functional activities.
Clinically it appears that, as our patients learn functional movements with abnormal coordination or compensatory movements, they develop motor programs through which the same abnormal movement components are habitually elicited. Therefore, our handling techniques must function to inhibit key parts of patients' movement patterns that belong to old motor programs, while we also help facilitate new movement patterns. The patients' active participation is needed in problem solving, performing and practicing the goal-oriented task with the new movements, in order for them to develop new motor programs. As functional goals are practiced with new movement patterns, new motor programs are developed and muscles learn to work in synergies with specific spatial and temporal qualities.
Although reflexes were central in the early phases of NDT, the Bobaths became increasingly aware and stated that they overemphasized the role of the reflexes. However, it is clinically obvious that many children with cerebral palsy do use the motor patterns of various tonic reflexes. Therefore, the role of the reflexes needs to be reevaluated, especially in respect to the child's functional use of the reflex patterns.
Reflexes, according to Easton, are basic "coordinative structures" that are hard-wired in the nervous system. Thus they are capable of activating specific muscles and synergies. Easton further suggests that these coordinative structures, or muscle synergies, can be activated centrally as well as through peripheral feedback. It may be that children with cerebral palsy centrally activate the muscle synergies (coordinative structures) of a reflex in the absence of sensory feedback, if they have learned to use the reflex functionally. If this muscle synergy is used to achieve a functional goal, it has become incorporated into a motor program.
On observation, it is noted that many children with cerebral palsy do use the muscle synergies of various reflexesi.e. asymmetrical tonic neck reflex (ATNR) or symmetrical tonic neck reflex (STNR)in functional movements. The ATNR is frequently used for reaching and for postural stability in sitting, walking, etc. The STNR is most frequently seen when the child moves to quadruped and when crawling ("bunny hopping") across the floor. These children have developed goal-oriented motor programs that include these muscle synergies or coordinative structures. Therefore, treatment must include inhibition of the motor patterns of the ATNR or STNR, while retraining and practicing new motor programs for performance of the functional skills in which the ATNR or STNR is used. This example should make it even more obvious why solely inhibiting reflexes will not lead to functional changes.
Today, NDT treatment sessions are being designed to include more functional activities, which use goal-directed feed-forward mechanisms. Functional activities can be any activities that are important to the performer. Activities of daily living such as dressing, undressing, feeding and bathing have always been an important part of NDT. Play is also a valuable channel through which children can learn to problem solve how to plan movements to reach a specific goal. Active participation by the children is critical for motor learning; through goal-directed activities, they receive external (knowledge of results) and internal (knowledge of performance) feedback, which helps them plan the next movement (feed-forward).
Often the therapist is so concerned with "quality" of the child's movement that the child is not permitted to move or is only permitted to move when everything is totally controlled or "right." This often leads to children with cerebral palsy becoming passive. We must appreciate that early stages of learning a motor task are not characterized by a high quality of movement and that true learning involves problem-solving, trying out different methods to achieve an end, as well as the active engagement of internal error detection, which only comes through self-initiated movements. we need only recall the quality of our movements when we are in the initial learning phases of a new motor taske.g., tennis, skiing, skate-boarding, etc. We try out different methods of performance, and it is doubtful that these early learning attempts are accomplished with high quality. This is not to say that quality should not be considered; however, quality of movement must be balanced with the need for the child to participate in planning, initiating, and performing movement. The skill and the art of treatment is in knowing when and what movement components to compromise in order for the child to experience problem-solving as he or she learns new movement patterns.
The subject of muscle tone, today, is an area of great confusion and controversy. However from their earliest writings the Bobaths emphasized that the issues of tone needed to be appreciated and addressed. They recognized that all children with cerebral palsy were characterized by having abnormal muscle tone and impaired coordination of muscle action.
Utilizing the writings of Jackson, Sherrington, Magnus, and Bernstein, the Bobaths developed their theories on tone. Tone was viewed as a condition beyond that found in individual muscles and, therefore, beyond elasticity of muscles. Instead, tone, or tonus, was viewed as an ongoing condition of readiness of the periphery, regulated by the entire neuromuscular apparatus and therefore related to coordination. They used the term "postural tone" rather than "muscle tone," for they believed that muscle tone served the maintenance of posture. They also stated that "the term 'postural tone' is preferred...to give expression to the fact that for the purpose of maintaining posture, tone is organized in coordinated patterns." Abnormal coordination of movement patterns and abnormal muscle tone were always considered to be interrelated.
Using the terms interchangeably, the Bobaths viewed abnormal tone, hyper tonus, or spasticity as a "release symptom," a release of the abnormal tonic and static reflex activity from higher inhibitory control. Subsequently, these tonic and static reflexes produced the typical abnormal postural patterns or "patterns of spasticity." The Bobaths further stated, "Spasticity is not confined to any one muscle group, but is co-coordinated in definite synergistic patterns." Bernstein further emphasizes this relationship between tone and coordination. "One is struck by the fact...that not a single case of pathological co-ordination is known in which there is not at the same time a pathology of tonus."
Although the "release phenomena" is no longer viable, the relationship between tone and movement patterns is still observed clinically. Therefore, the cause-effect correlation requires further investigation. Gordon suggests that patients with neurological problems may develop abnormal movement patterns in an attempt to compensate for the neurological insult, rather than because of the insult. These patients continue to use these patterns because "they work."
There is now the unanswered question of whether all increased tone is spasticity. Spasticity is generally accepted as being hyper tonus, characterized by increased resistance to passive movement, velocity-dependent resistance to movement, and a hyperactive tendon jerk. If all hyper tonus is not due to spasticity, what are other possible sources of the hyper tonus clinically observed in children with cerebral palsy?
Bernstein's theory on how the nervous system handles redundant degrees of freedom may provide one possible hypothesis. Bernstein suggested that during skill learning the nervous system eliminates some of the degrees of freedom by keeping the body fairly rigid, by fixing or freezing non-essential movements. Such "fixing" reduces or eliminates many of the reactive forces. As skill increases, the child learns to work with the reactive forces and will release the freeze on the degrees of freedom, allowing additional movements to occur. When fixing is used to decrease the degrees of freedom at a joint or joints, the muscle tone or stiffness around that joint increases. This concept may provide a possible hypothesis for how muscle tone increases during the development of children with cerebral palsy.
It has been clinically observed that normal infants use fixing patterns during their developmental process, and the fixing patterns give way to more fluid movements. Infants and children with cerebral palsy also use similar fixing patterns early in their development to stabilize and control their movements. However, their fixing patterns do not give way to more fluid movements, but rather lead to more restricted abnormal movements. The infant/child may continue to freeze out degrees of freedom at many joints because "it works." Prolonged use of fixing leads to an increase in the muscle tone around specific joints and eventually leads to increased shortening of muscle fibers, which causes contractures and reduced or limited joint range. This has serious kinesiological consequences in a growing skeletal system.
NDT handling techniques are designed to control the child's abnormal and fixing patterns. By using key points of control, the therapist hands help to reduce some of the child's degrees of freedom, thus reducing or eliminating the child's need to fix to reduce these degrees of freedom. If he does not have to use his own limiting methods of fixing, his muscle tone is not increased. These handling techniques must not be totally controlling and must be incorporated into the child's own goal directed movements, in order for the child to develop new muscle synergies and new motor programs.
As we continue to try to expand our understanding of the movement disorders demonstrated by children with cerebral palsy, it is prudent to utilize other domains in the movement sciences. Kelso and Gentile suggest that there are three primary levels that must be analyzed and integrated to understand human movement. Kelso's areas of behavior, kinesiology, and neurophysiology are similar to Gentile's levels of action, movement, and neuromotor processes. Action and behavior both focus on the outcome of performance. Movement and kinesiology deal with the kinematics of human movement. Neuromotor processes and neurophysiology investigate the underlying neural mechanisms involved in controlling movement.
These three levels were implicitly and explicitly stated in many of the Bobath articles, but perhaps the first two, behavior and kinesiology, became overshadowed in an attempt to stress that cerebral palsy is a neurological problem and had to be evaluated and treated as such. However, the Bobaths also advocated analyzing the child's movement patterns and preparing the child for "skilled motor patterns for everyday life and self-help." This statement supports the importance of investigating the kinesiological/movement and behavioral/action perspectives of movement. Subsequently, NDT instructors Ryerson, Levit, Boehme, and Bly have written articles to advocate that the kinesiological aspects of the movement problems must be analyzed and addressed.
For example, during evaluation and treatment, the kinesiological perspective of proximal-distal/distal-proximal control and open/closed kinematic chains must be investigated. When the affects of the closed kinematic chain are considered, it is increasingly obvious that the biomechanics of the distal-proximal relationship are important. In the closed kinematic chain, the position of the base of support establishes the alignment of the associated superstructure. Although the importance of working on proximal-distal control has traditionally been stressed in NDT, it is becoming more obvious that working on distal-proximal and proximal-distal control may be of equal importance.
As the name neurodevelopmental treatment suggests, development is an important aspect of this treatment approach. Although the Bobaths originally stated that the developmental sequence had to be followed, they soon observed that there were many variations and areas of overlap in the motor developmental sequence in normal infants. Subsequently they stated: "Treatment should not attempt to follow the sequence of development...Rather it should decide what each child needs most urgently at any one stage or age, and what is absolutely necessary for him in preparation for future functional skills, or for improving the skills he has, but performs abnormally...There is no time to waste on unspecified general developmental treatment, for we cannot expect that such treatment will automatically carry over into functional skills later on."
Although knowledge of the developmental sequence is a valuable guide in the treatment of infants under 1 year of age, we must separate the behavior from the kinesiological structure. The milestone is the behavior or outcome goal, and it is purposeful to the baby's learning and interaction with his environment. Each milestone, as well as the transitions between the milestones, has a dynamic kinesiological structure. In treatment the kinesiological structure, not just the behavior, should be facilitated.
As an example, forearm weight bearing is seen in the 4- to 5-month-old infant. Forearm weight bearing is the behavior. Kinesiological, normal forearm weight bearing is achieved by activation of the shoulder girdle and trunk musculature.
Many children with cerebral palsy have difficulty achieving this position or achieve it with abnormal control. Therefore, in assessing the movements of a child with cerebral palsy, the therapist must determine if the absence of this behavior is important and/or if the absence of the kinesiological components is important. For a 4-month-old, controlled forearm weight-bearing activities are usually appropriate behaviors to use to work on developing increased shoulder girdle and upper trunk control. For a 4-year-old or a 14-year-old, forearm weight bearing may not be an appropriate behavior. However, the kinesiologicai problems of poor scapulae stability, poor glenohumeral joint stability and dissociation, and poor control of the humerus on the chest interfere significantly with the older child's upper extremity use. Fortunately, these trunk and shoulder girdle muscles can usually be worked on in other more age-appropriate positions. For example, while the child is aligned in sitting, have her reach forward onto a mirror or bolster while engaging in an age-appropriate activity.
If one follows the developmental sequence primarily from a behavioral perspective, all patients regardless of age would be expected to achieve forearm weight bearingregardless of how it is achieved. However, failure to understand and address the kinesiological components, and overuse of the behavioral aspects of the milestones, may actually contribute to further abnormal motor development.
CONCLUSION
It has been evident throughout the history of NDT that it is easy for us to become attached to the most tangible facets of the approach. We have each been guilty of out-of-context emphasis on the most easily defined aspects of the neurodevelopmental treatment strategies such as inhibition, postural reflexes, righting reactions, reflexes, and blocks. However, we must return to Mrs. Bobath's philosophy of evaluating and treating the whole child, and constantly evaluating the results of the treatment in the context of the individual child.
As an approach designed for the treatment of children with cerebral palsy, the NDT theoretical framework will continue to be presented as a working hypothesis built on empirical data. As a living concept, the new research findings from the movement sciences and neurophysiology are being carefully examined and utilized as supporting evidence for the empirically based NDT approach.
NDT Philosophy
The Neuro-Developmental Treatment/Bobath (NDT) approach is a "living concept." It is a problem solving approach, which involves the treatment and management of movement dysfunction in individuals with CNS pathophysiology. The person is addressed as a whole and the intervention process is individualized. The NDT approach is an interactive process among the individual, the caregivers, and the interdisciplinary team.
The overall goal of treatment and management is the enhancement of the individual's capacity to function. To reach this goal the quality of movement is addressed utilizing principles of movement science. Intervention involves direct handling to optimize function. Treatment includes the active participation by the individual with gradual withdrawal of the direct input of the therapist. This process contributes to the individual's increased independence and quality of life.