Evaluating the Child with Cerebral Palsy
Introduction
Most of the information leading to the diagnosis of cerebral palsy is generally obtained from a thorough medical history and examination. The most critical tasks of the health care professional are to identify potentially treatable causes of a child's impairment. The health care professional evaluating the child with possible cerebral palsy should be experienced in neurological examination and assessment of impaired children and well-versed in the potential causes of cerebral palsy. Often, but not necessarily, this practitioner should be a pediatric neurologist. Once the examination is complete, depending on the findings, the practitioner may order laboratory tests to help in the assessment.
There is no single test to diagnose cerebral palsy. But since cerebral palsy is the result of multiple different causes, the tests performed are used to identify specific causes when possible. Other tests will be performed to assess the condition of the child (nutritional status for example) or to assess other concomitant conditions that the child might have.
Clinical Assessment
Evaluation of an ambulant child with CP requires a unified Multi-Disciplinary Team (MDT) often comprising of a medical doctor or paediatrician, rehabilitation consultant, neurologist, orthopaedic consultant, physiotherapist, occupational therapist, clinical scientist and orthotist. [1] The MDT needs to have a close working relationship with the parents or caregivers to ensure consent is provided for assessment or for any proposed interventions and to ensure the treatment is incorporated into everyday family life.
Observing the child’s movements is the initial and a crucial part of the examination. Observe before you touch. If the child is young, apprehensive or tearful, let them stay on mother’s lap while you watch and talk to the mother. As the child adapts to the environment, slowly place them on the examination table or on the floor still close to the mother/carer and watch them move around. If the child cries a lot and does not cooperate, continue while they are in their mother’s lap. Tools required for the examination are very simple: toys, small wooden/different shaped blocks, and objects with different textures.
A thorough physical and biomechanical evaluation is necessary to decide the specific joints and segment levels to target any intervention. The physical examination of the child with Cerebral Palsy should evaluate:
Posture in Prone Lying, Supine Lying, Sitting, Standing and Walking;Muscle Tone of the Extremities, Trunk and Neck, Deep Tendon Reflexes;Muscle Strength; andJoint Range of Motion at the Hip, Knee, Ankle, Sub-talar and Mid-tarsal Joints. [1] [2]
As Cerebral Palsy is a disorder of movement that commonly presents with muscle tone abnormalities, it is critical to perform an evaluation of muscle tone during the initial and any future physical evaluations. Hypertonia due to an extra pyramidal brain lesion is known as dystonia and presents as involuntary intermittent muscle contractions that cause twisting or repetitive movements of abnormal postures. Hypertonia where a pyramidal brain lesion exists presents as muscle spasticity. Spasticity accounts for 80% of paediatric Cerebral Palsy presentations and is defined as a motor disorder characterised by a velocity dependent increase in tonic stretch reflexes (muscle tone) with exaggerated tendon jerks. [3] It results from hyper excitability of the stretch reflex as one component of the upper motor neurone syndrome. The identification and quantification of spasticity is critical when determining appropriate orthotic intervention. Identifying the joint angles during joint Range of Motion (ROM), testing at slow, medium and fast velocities where an increase in muscle tone is first felt and also at the end of joint ROM, helps establish the angle the anatomical joint will be positioned within any potentially prescribed orthosis. It also determines if, and what type, of mechanical joints may be included in the orthotic design.
Tone
The measurement tools used to evaluate muscle tone in children with Cerebral Palsy can be divided into two main groups according to their assessment technique and method of quantification. The Tardieu Scale (TS) assesses spasticity by passively moving the joints at three specified velocities (slow, under gravity and fast) while the intensity and duration of the muscle reaction to stretch (X) is rated on a 6-point scale (Table.1), with the joint angle (Y) recorded at where the muscle reaction is first felt. [4]
Velocity
Description
V1
As slow as possible (slower than the natural drop of the limb segment under gravity)
V2
Speed of the limb segment falling under gravity
V3
As fast as possible (faster than the rate of the natural drop of the limb segment under gravity)
Grade
Decsription
0
No resistance throughout passive movement
1
Slight resistance throughout, with no clear catch at as precise angle
2
Clear catch at a precise ankle followed by a release
3
Fatigable clonus (<10 seconds) occurring at a precise angle
4
Unfatigable clonus (>10 seconds) occurring at a precise angle
5
Joint immobile
TABLE 1: Definition of the velocities used and the 6-point scale used to grade the quality of muscle reaction when using the Tardieu Scale to assess spasticity
Due to the large amount of time required to perform the full Tardieu Scale, the Modified Tardieu Scale (MTS) was developed. It records the joint angles during the fast and slow velocities only. It uses the most clinically significant parts of the TS: the angle of catch at the most rapid velocity (R1) and the joint angle when the muscle length is at its maximum (R2), assessed by moving the joint through full ROM using slow passive movement. [5] The MTS has been found to be a valid, reliable and sensitive abridged version of the TS. [6] [7] [8] The difference in degrees between the angles R2 and R1 is referred to as the dynamic component of spasticity and estimates the relative contribution of spasticity compared to muscle contracture. [6] [5] [9]
The Ashworth Scale (AS) grades the intensity of muscle tone through joint ROM on a five-point scale at one non-specified velocity. (TABLE 2) Modifications of the AS are referred to as the Modified Ashworth Scale (MAS). Literature has also described the MAS to include a 6-point grading scale, a grading for the severity of the muscle tone and also the assessment of the muscle tone at an unspecified ‘fast’ velocity. [4]
Grade
Description
0
No increase in muscle tone
1
Slight increase in muscle tone, manifested by a catch and release or by minimal resistance at the end of the range of motion when the affected joint is moved in flexion or extension
1+
Slight increase in muscle tone, manifested by a catch, followed by minimal resistance throughout the remainder (less that half) of the ROM
2
More marked increase in muscle tone through most of the ROM, but affected joint is easily moved
3
Considerable increase in muscle tone, passive movement is difficult
4
Affected joint is rigid in flexion and extension
TABLE 2: The Grading Scale and description for the Ashworth Scale of Spasticity Evaluation [10]
As with any measurement tool, common sources of error are attributed to the individual taking the measurements, inaccuracies in the measurement instruments and variability in the characteristics being measured. [1] Studies on the reliability of the TS and the MTS have demonstrated high intra and inter rater reliability when assessing children with Cerebral Palsy, provided sufficient time is allowed for training and practice. [8] [2] However, the AS displayed poor test and re-test results for both inter and intra rater reliability. [4] [8]
Spasticity is defined as the velocity dependent increase in muscle tone, which means only the Tardieu Scale is an appropriate assessment tool as it accounts for the velocity dependent nature of spasticity by passively stretching the muscles at three different speeds. [3] The AS assessment tool measures passive resistance to motion at one speed, leading to inconstancies and over-estimations in the identification of spasticity, especially in the presence of muscle contracture. [3] Despite the widespread use of the AS and its ability to identify general hypertonia, it is recommended that this tool no longer be used and that the TS or MTS be used to evaluate the muscle tone in ambulant children with Cerebral Palsy. [5]
Children with Cerebral Palsy who present with altered states in muscle tone often show signs of underlying muscle weakness and it is therefore important to evaluate the lower limb muscle strength in ambulatory children with Cerebral Palsy. [4] [6] The child with Cerebral Palsy who has greater muscle strength will achieve a higher motor function level as muscle strength is more highly correlated to function than the presence of spasticity. [5] There is a direct correlation between muscle strength and a child’s motor function, walking speed, energy expenditure and the temporo spatial characteristics of gait. [7] [8] There is also an incremental drop in muscle strength in all muscle groups, with increasing walking difficulty from GMFCS levels I to III. [6]
Strength
The presence of muscle weakness leads to muscle imbalance across other joints. This muscle imbalance is thought to be a factor in the development of muscle shortening, contributes towards rotational deformities and further affects the motor function of a child. [4] [6] Hence, when performing the orthotic assessment of a child with Cerebral Palsy, a full muscle strength profile of the lower limbs is vital. The Medical Research Council Scale (MRCS) for manual muscle testing is the widely accepted clinical evaluation tool used to grade the muscle strength a child with Cerebral Palsy. [6] (TABLE 3) During the assessment it is important to note if the child does not cooperate, is unable to isolate the muscle being tested or comprehend what is being asked of them. If further quantification of muscle strength is required, a hand held dynamometer may be used. [6] [4]
Grade
Description
0
No movement is observed
1
Only a flicker or trace of muscle movement is seen or felt in the muscle or fasiculations are observed in the muscle
2
Muscle can only move if the resistance of gravity is removed
3
Muscle strength is further reduced such that the joint can be moved only against gravity with the examiner’s resistance completely removed
4
Muscle strength is reduced but muscle contraction can still move the joint against resistance
5
Muscle contracts normally against full resistance
TABLE 3: The Medical Research Council Scale (MRCS) for muscle strength evaluation [9]
Range of Movement
Muscle contracture and bony deformities are the commonly observed secondary musculoskeletal problems that children with Cerebral Palsy may develop. These secondary musculoskeletal problems cause a decrease in the child’s available lower limb joint
ROM. Therefore, evaluation and quantification of the passive and dynamic lower limb joint ROM is a crucial part of the orthotic assessment of any ambulant child with Cerebral Palsy. The findings assist with the prescription of orthoses, evaluation of the intervention and the monitoring of change due to growth.
The hip joint should be assessed for the amount of available passive and dynamic ROM in flexion, extension, abduction and adduction. Hip flexion contractures are a frequent presentation in a child with a predominantly spastic presentation of Cerebral Palsy. A primary hip flexion contracture adversely affects the kinematics of a child’s gait by:
Restricting heel contact at initial contact;Altering the position of the body’s weight line during stance phase;Changing the degree of inclination of the femur and the tibia during stance phase;Reducing the amount of hip extension possible, causing an interruption of transfer through the second and third rockers of stance phase.
The knee joint needs to be assessed for flexion and extension in both passive and dynamic ROM. It is also important to assess the joint range of motion of the passive, active and velocity specific knee extension with the child supine and the hip flexed to approximately 30°. This position replicates the degree of the hip flexion that occurs at initial contact during gait and establishes the degree of knee extension that is possible during early stance phase.
To establish the ROM of plantar and dorsi flexion at the ankle joint, it is important the sub-talar joint is maintained in a neutral alignment and the tests are best carried out with a child in a supine position. Movement of the sub-talar joint into either eversion or inversion while dorsi flexing the ankle affects the length of the gastrocnemius muscle and may produce erroneous findings of the available dorsiflexion ROM. [10] A plantar extensor pattern generally exists in the lower limbs of a child with a spastic presentation of Cerebral Palsy. This often causes either the gastrocnemius or soleus muscles to be affected by increases in muscle tone. The gastrocnemius is a bi-articular muscle, originating proximal to the femoral condyles and inserting at the base of the calcaneus. Flexing the hip and knee to 90° and then dorsi flexing the ankle eliminates the effects of the gastrocnemius muscle on the foot and ankle and makes it possible to check the available ROM and muscle tone specifically attributed to the soleus muscle. (FIGURE 1A)
A
B

FIGURE 1: Physical evaluation of the ROM of the ankle joint due to the Soleus Muscle (A) and the Gastrocnemius Muscle (B) [1]
Alternatively, positioning the hip in 30° of flexion, the knee in the maximum attainable extension, the sub-talar joint in a neutral alignment and then dorsi flexing the foot establishes the ROM of ankle dorsiflexion that is attributable to either changes in muscle tone or contracture of the gastrocnemius muscle. (FIGURE 1B) Assessing the ankle ROM due to gastrocnemius length ascertains the child’s plantar flexion-knee extension couple. This is used during the prescription of an AFO to determine the Angle of the Ankle in the AFO (AAAFO) and is the degree of ankle dorsi or plantar flexion the ankle is positioned within the AFO. It is defined as the angle of the foot relative to the tibial shank when viewed in the sagittal plane. [2]
Torsional deformities in ambulant children with Cerebral Palsy occur when there are muscle imbalances and abnormal loading and growth of bones due to increased tone or weakness. [3] Therefore it is important to include a rotational assessment of the joints of the lower limbs. The particular areas to assess are hip internal/external rotation, femoral ante/retro version, degree of tibial torsion, sub-talar inversion/eversion and mid-tarsal ab/adduction. Establishing the torsional profile of a child’s lower limbs aids orthotic prescription by identifying if a torsional lever arm deficiency is present. [4]
Goniometric measures are the most widely used technique to assess either passive or velocity dependent lower limb joint ROM in a child with Cerebral Palsy. [6] Factors such as the number of assessors, patient compliance and the method used for measuring can affect the reliability and repeatability of measures. Several studies involving children with spastic Cerebral Palsy found that goniometric measurements display high levels of inter and intra reliability and repeatability for observers who are trained and experienced. [8] [5] [7] [8] This is provided a strict measuring protocol is adhered to.