Prognosis of movement abilities can be made in the second to third year of life and is strongly related to the kind and localization of the motor disorder and the mental status of the child. There are three main types of motor syndromes: spastic paresis, ataxic paresis, and dyskinetic paresis.
Spastic paresis is characterized by a posture- and movement-dependent tone regulation disorder. The clinical symptoms are the loss or absence of tone in lying, and increase in tone in sitting, standing, walking, or running, depending on the degree of involvement. Spastic paresis is the most common motor disorder (83%). 2
In patients with ataxic paresis, impairments of equilibrium and coordination are dominant. There are hypermetric movements in the extremities, and tremor and titubations can be present. Only 4% of children with CP have a mainly ataxic paresis, often with some signs of spasticity in the legs. The time course of obtaining walking ability is delayed in comparison with spastic paresis, but most children achieve walking ability, at least with a walking aid.
Dyskinetic paresis can be divided into the hyperkinetic (athetoid) type, characterized by involuntary movements, most pronounced in the face and extremities, which are present even at rest, and the dystonic type, characterized by slow powerful contractions of agonist and antagonist of movement simultaneous, locally or with total body involvement. In time, a hyperkinetic type of movement can change into a dystonic type, and combinations are also possible. The development of head and trunk balance is delayed. Some children achieve walking ability even at the age of 10 years. Dyskinetic paresis is seen in 12% of children with CP.
For the proper treatment of children with CP, the classification of the kind of motor disorder is crucial. The surgical and orthotic management in children with dyskinetic or ataxic paresis is completely different from that of children with spastic paresis. Because the spastic paresis is the most common motor syndrome, this article will focus on that motor disorder.
The motor disorder can also be classified in regard to the localization: hemiplegia is defined as a unilateral involvement (33%); diplegia as a bilateral involvement, in which only the lower extremities are involved or the lower extremities are more involved than the upper extremities (44%); quadriplegia (or tetraplegia) is defined as a bilateral involvement, in which the upper extremities are equal or more involved than the lower extremities (6%). This classification is unambiguous and easy to use in clinical practice. [Classifications using the presence of muscle impairment of the upper extremities (paraparesis if no involvement of the upper extremities, diplegia with involvement of the upper extremities) or bulbar involvement (diplegia without bulbar involvement, quadriplegia with bulbar involvement) can cause confusion. These signs can be present only slightly, so it is difficult in clinical practice to set limits for the classification paraparesis, diplegia, and quadriplegia.] According to this classification, the functional prognosis of independent walking ability (with or without walking aids) can be set: 100% of the hemiplegic children, 85% of the diplegic children, based on the ability to put weight on the hands while prone at 18 months and a short sit at the age of 24 months, 7 and none of the quadriplegic children will achieve independent walking ability in adulthood. 8,9 The Gross Motor Function Classification System (GMFCS) is an instrument for early classification the severity of the motor disorder. 10
CLASSIFICATION OF IMPAIRMENT IN MUSCLE FUNCTION IN SPASTIC PARESIS
About 80–90% of the children have spastic paresis as the motor disorder. However, with regard to the impairment of muscle function, a variety of clinical symptoms can be distinguished. Several terms have been used in the literature to describe the different symptoms of spastic paresis, and the same terms are often defined differently. 11 The term “spasticity” is often used for all kinds of motor disorders or for all signs of a spastic paresis. Because a proper description of the different symptoms is needed for selection of patients for a specific therapy, conventions about terminology are needed. The following classification is according to the actual insight.
In spastic paresis, three sets of symptoms can be distinguished: impairment of muscle activation; impairment of muscle stiffness; and impairment of muscle length.
IMPAIRMENT OF MUSCLE ACTIVATION
Impairment of muscle activation can be divided into deficit symptoms and excess symptoms.
Deficit symptoms are caused by the reduction of voluntary muscle function. In the case of mild involvement, only loss of dexterity of movement, diminished ability to perform fast alternating movements and enhanced fatigability are present. In more severe involvement, the patient can perform only synergistic voluntary movements and the level of force is reduced. The lowest level of motor control is voluntary movement in a general flexion (mostly present in the upper limbs) or extension pattern (mostly present in the lower limbs). Synergistic voluntary movements are also described as “loss of selective motor control.” In spastic paresis, the influence of posture is also increased. For instance, it is much easier for most patients to bend the hip in a sitting position than in a standing position. For that reason, it is not rational to use the Medical Research Council scale for grading the force of muscles when synergies of muscle movements are present.
Excess symptoms reflect the presence of abnormal muscle activity. Clinically, the presence of abnormal muscle activity can be noticed either during passive joint movements, while the patient is in maximal relaxation, or while the patient is performing motor tasks.
During (very) slow passive movements, muscle tone can be examined. Some patients show a raised muscle tone during a very slow passive stretch (hypertonia defined as a non-velocity-dependent resistance to passive stretch). This increased resistance could be caused by a continuous activation of the stretched muscle (tonic stretch reflex activity).
During fast passive movements, the presence of spasticity, defined as the velocity-dependent resistance to passive stretch, can be examined. If only a catch (clasp-knife symptom) can be noticed, the spasticity is mild. In more severe spasticity, a clonus in the muscle or a marked increase in resistance can be evoked. 12 Hyperreflexia of tendon jerks, abnormal cutaneo-muscular reflexes (such as Babinski’s response) are also excess symptoms.
When performing motor tasks, three other features of involuntary muscle activation can be present:mirror movements can be present in patients with a hemiplegia or asymmetric diplegia: strong voluntary contraction of a muscle on the unaffected side evokes contractions in the same muscle on the opposite side;involuntary synergies can arise during the performance of a motor task. For example, the occurrence of a flexor synergy in the arm of hemiplegic patients when walking;postural reflexes cause involuntary muscle activity during the performance of a motor task (e.g., the clawing of the toes when walking). The muscle contractions develop gradually during walking.
Active (Voluntary) Movement
During active movement, co-contraction of the antagonist is also an excess symptom. Clinically, co-contraction can sometimes be observed as a paradoxical movement. For instance, the patient is asked to extend the elbow, but a flexion movement takes place: the co-contraction of the flexors is more powerful than the contraction of the extensors of the elbow. There is no relationship between the presence of co-contraction during voluntary movement and spasticity during passive movement. 13 The amount of co-contraction in repetitive movements of the ankle is significantly lower on the hemiplegic side than on the unaffected side. 14
IMPAIRMENT OF MUSCLE STIFFNESS
Clinically, increased muscle stiffness (defined as hypertonia) can be observed during slow passive stretch of a muscle after maximal relaxation. It is important to choose a posture for the patient in which maximal relaxation can be achieved (i.e., lying supine, flexion-abduction-exorotation in the hip and flexion in the knee will relax the triceps surae muscle). Without electromyographic activity, hypertonia can be caused by changes in the biomechanical properties of the muscle
IMPAIRMENT OF MUSCLE LENGTH
The development of muscle shortening is a well-known phenomenon in clinical practice. It is unclear why muscle shortening is present in some patients and not in others. A neurological growth disturbance has been postulated. 15 Because muscle shortening takes place in the pattern of movement, a relation between gait pattern and muscle shortening seems probable.
The classification of impairment of muscle function in spastic paresis is summarized in Table 1. The clinical consequences of this classification are evident: treatment of spasticity can improve only functional problems caused by spasticity, not by other such impairments as postural reflexes, hypertonia, or muscle shortening. This is crucial, for instance, for selection of patients for a specific therapy, such as prescription of ankle foot orthoses or selective dorsal rhizotomy.
CLASSIFICATION OF GAIT PATTERN
In children with CP, the classification of gait pattern can be used to determine developmental risks, to forecast walking ability in time, and to define therapeutic measures, such as orthotic treatment or surgery. For hemiplegic patients, four kinds of gait patterns are recognized. 16 The following classification can be used for both hemiplegic and diplegic patients. Diplegic patients can show different patterns for each leg.
Type 1: Insufficient Foot Lift in Swing
In children affected only mildly, the main problem in walking is insufficient foot lift in mid-swing and forefoot landing at initial contact. In general, insufficient activity in the tibialis anterior and/or shortening of the gastrocnemius muscle is the cause of this gait pattern.
Type 2: Knee (Hyper)Extension in Midstance without Heel Rise
More severely affected children show, besides the insufficient foot lift in mid-swing, knee extension or hyperextension after initial contact instead of knee flexion, without heel rise in midstance. This is caused by a premature activation of the triceps surae muscle. The forefoot landing may be caused not only by insufficient foot lift but also by incomplete knee extension in terminal swing due to insufficient selective motor control (in terminal swing, hip flexion must be combined with a knee extension movement (Figure 3).
Type 3: Knee (Hyper)Extension in Midstance with Heel Rise
This gait pattern is similar to type 2, but heel rise takes place in midstance (Figure 4). A higher degree of abnormal activation of the triceps surae muscle is present. Prolonged activation of the vastus lateralis muscle can be present as a sign of insufficient power of the gastrocnemius muscle in terminal stance. In that case, the risk of development of a gait type 4 is present.
Type 4: Knee Flexion in Midstance with Heel Rise
In severely affected children, a gait pattern characterized by hip and knee flexion in midstance can be present. This gait pattern can be caused by strong abnormal activity (with or without muscle shortening) of the gastrocnemius and hamstring muscles or by abnormal activity of the psoas and hamstring muscles (Figure 5). The former situation has a better functional prognosis than the latter. These children are at high risk of developing shortening of the psoas, hamstring, and gastrocnemius muscles, and, in later stages, flexion contractures in hip and knee joints. Because this gait pattern is very energy-consuming, deterioration in (pre)puberty can be expected.
Type 5: Knee Flexion in Midstance without Heel Rise
The worst pattern of gait is a gait pattern with flexion of the hip and knee in midstance without heel rise. Insufficient power of the gastrocnemius muscle must be present. Often, it is caused by previous gastrocnemius surgery or Achilles tendon lengthening, but it can also develop spontaneously (Figure 6). If a change of gait pattern in bilateral involvement, at least into type 4 gait pattern, cannot be reached, loss of walking ability can be expected in puberty.
Besides these gait patterns, foot deformation can be present (varus or valgus) (Figure 6). Increased homolateral trunk movements or pelvic drop of the contralateral leg in midstance are signs of weakness of the hip abductors (Figure 3). Also, endorotation adduction motion in terminal swing can be present, in severe cases resulting in rubbing of the knees (Figure 5). This can be caused by shortening or abnormal activity of the medial hamstrings. Persistent adduction in stance and swing can be caused by shortened hip adductors, endorotation by increased hip anteversion and endorotation contractures. Exorotational or endorotational foot progression angles can be caused by hip rotational contractures or rotational deformities of the femur or tibia. Insufficient foot clearance in preswing can be related to insufficient hip and knee flexion or abnormal stretch reflex activity (and shortening) of the rectus femoris muscle. 17
All these aspects of the gait pattern must be taken into account for making a plan for improvement of gait. The task of the medical specialist is to coordinate the multidisciplinary treatment of children with CP. Setting long-term goals on the level of abilities is the major task of the team. The medical specialist must determine the functional possibilities of the child and the risks for deterioration during growth. The medical treatment should take place within a whole treatment program, taking into account all aspects of development of the child and the possibilities of its environment. It is a challenging task for teams specializing in the treatment of children with CP.
In children with CP, a complex of neurological impairments and developmental risks with regard to their physical, psychological, and social development can be present. Pediatric rehabilitation is a complex process, facing all these problems. First, the diagnosis and functional prognosis of the child with regard to movement abilities, cognition, and communication must be determined. A multidisciplinary treatment approach is needed. A tool for team conferences, based on the model of the ICF, is presented. Because the motor impairment is the main interest of medical treatment, classification of the motor syndromes and impairment of muscle functions are described. Finally, a classification of gait patterns in relation to the degree of involvement for patients with a spastic paresis is described. This classification can be used to set the prognosis of ambulation and the kind of interventions needed to optimize the walking ability.
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Keywords:© 2002 Lippincott Williams & Wilkins, Inc.
Rehabilitation; therapy; management; cerebral palsy; spasticity; gait analysis; team management