Cerebral Palsy (CP) is primarily the most important cause for disabilities in children. CP rate is approximately 2 to 3 per 1000 live births in European countries (SCPE, 2000) the National Institutes of Health Clinical Centre (CC) investigated the newborn babies in the United State, they found that 0.25% of newborns are affected by CP (CC, 2009) and this rate is same for most of the developed countries (Bonellie, 2007; Pharoah, 1998; Sciberras C, 1999; SCPE, 2000). In addition, this rate increases to 40-100 per 1000 live births among babies born very early or with very low birth weight (Krägeloh-Mann and Cans, 2009)
CP is a group of central nervous system (CNS) disorders which affects the body's ability to control movement and posture. The motor neuron system is divided into two groups: upper motor neuron (UMN) and lower motor neuron (LMN). UMNs consist of the cell bodies within the motor cortex, the medulla or within the spinal cord. LMNs consist of cell bodies in the anterior horn of spinal cord.
The clinical features of motor neuron dysfunction or brain damage can be divided into two broad groups: Negative phenomena; muscle weakness, loss of dexterity, fatigue ability and positive phenomena; increase tendon reflex, clonus, spasticity (Pandyan et al., 2001).
Cerebellum plays a major role in regulating muscle tone, the lesions of this can affect a child's ability to control movement and posture with either low muscle tone (hypotonia) or high muscle tone (hypertonia) or a combination of the two (fluctuating tone). Hypertonia is an abnormal increase in muscle tension. It is a common symptom of CP that can lead to loss of function and deformity. The hypotonic CP has reflex patterns which distinguishes it from lower motor neuron causes of hypotonia. Infants with hypotonic CP are floppy in overall muscle tone, have significant delays in motor milestones and weak facial and oral muscles consequently there often are associated problems with feeding. Children who have CP often have stiff, jerky movements and extensor spasms where their joints fully extend for a period of seconds before relaxing. Some of them cannot do the verbal communication, have to use of signing or recognition of symbols such as smile, turning red in the face, beginning to perspire heavily or any communicate via eye contact.
1.2.1 Classification
The principal problems in CP are directly related to the lesion of the central nervous system (CNS). The numerous features which is associated with CNS lesion can be summarised by following: loss of selective muscle control, dependence on primitive reflex patterns, abnormal muscle tone, imbalance between agonists and antagonists muscle and deficient equilibrium reactions (Panteliadis and Strassburg, 2004).
The classification of CP has been a source of a number of discussions over the year, in order to the categorisation of CP is variability within each boundary. Different categories are based on pathology, aetiology or clinical description. Since they are unclear in so many cases, universal classification is currently possible only for clinical description and based on theories of Hagberg (Panteliadis and Strassburg, 2004) ,but reliability is ambiguous and difficult in practice (Blair and Watson, 2006). The clinical signs, classified according to the main symptom, are spasticity, hypotonia, dystonia, ataxic, dyskinetic or a combination of the above (Table XX). Many support of the suggestion that the scription of CP should include the type of symptoms, is in term of mild, moderate, or severe. Mild CP is characterised by presence of clear clinical symptoms, without any limitation to daily motions and more severe is characterised by serious obstruction of activity (Panteliadis and Strassburg, 2004).
Clinical classification
Lesion sites
Type of symptoms
Mild
Moderate
Severe
Spasticity
cortex
: hypertonic, stiff and jerky movements, classified by the part of the body affected
Ataxic
Basal ganglia
: unsteady and shaky affects the sense of balance and depth perception.
Dyskinetic
cerebellum
: uncoordinated movements that will interfere with speaking, feeding, and other skills
Hypotonia
: limp muscle can move only a little or not at all
Mixed
diffuse
: gennerally will mixed between Spastic and another
Classification used by American Academy for CP divides into two classifications by major physiologic: pyramidal (spastic) and extra pyramidal (non spastic). Another based upon the part of limb that is involved or topography of motor lesions is the following: monoplegia, diplegia, hemiplegia, triplegia, or quadriplegia that shows in table XX.
1.2.2 Spastic CP
The most common type of CP is spastic CP, which causes children have stiff and jerky movements. The nature of spasticity remains a controversial. A widely accepted definition of spasticity, which is classically defined by Lance: is "a motor disorder characterised by a velocity-dependent increase in tonic stretch reflexes with exaggerated tendon jerks, resulting from hyper-excitability of the stretch reflex"(Lance, 1980). In the other words, spasticity is a hyperactive muscle fast stretch reflex which is result of uncoordinated agonist and antagonist muscle activity due to dysfunction of the electrical signal from the motor neuron system.
Normal muscle physiology
Human bodies consist of 3 types of muscle: cardiac muscle or heart muscle makes up the wall of the heart, smooth muscle is found in the walls of all the hollow organs of the body (except the heart) and skeletal muscle or striated muscle is the muscle attached to the skeleton. Both cardiac and smooth muscle can contract without being stimulated by the nervous system. Different from the first two kinds, the contraction of skeletal muscle is controlled by the nervous system which is to a large extent under voluntary control.
There are four importance characteristics of muscle activities: excitability, contractility, extensibility and elasticity. Excitability is that muscle responds to stimuli from nerves. Contractility means the length of muscle can contract or shorten. Extensibility means that muscle can be stretched when pulled. And the last functional characteristic is elasticity, muscle trends to return to original shape and length after extension or contraction. Clearly, movement is created by the contraction of skeletal muscle. In normal cases, muscle fibres have a length of up to 30 cm but less than 0.1 mm in diameter (Basmajian, 1978). When these fibres receive a motor order from the nervous system, they can shorten to about 57% of it resting length (Basmajian, 1978).
Muscle contraction is started by electrical stimulation of the motor neurons, with one motor neuron often controling more than one motor unit. The movement mechanism occurs in the muscle spindle, when the gamma motor neuron receives commands from the upper motor neuron, it will innervate the group I afferent nerves in the muscle spindle. In antagonism process, a group of muscle fibres (agonist) will flex while another (antagonist) will extend. After the contraction, the group II afferent nerves in the muscle spindle will action to alpha motor neuron to reset the muscle contractions.
The area where the nerve contacts the muscle is called the neuromuscular junction, or the motor end plate. After the action potential is transmitted across the neuromuscular junction, an action potential is elicited in all of the innervated muscle fibers of that particular motor unit. The sum of all this electrical activity is known as a motor unit action potential. This electro physiologic activity from multiple motor units is the signal typically evaluated during an electromyography (EMG). The composition of the motor unit, the number of muscle fibres per motor unit, the metabolic type of muscle fibres and many other factors affect the shape of the motor unit potentials in the myogram.
Forces produced by contraction of a single unit are distributed though the muscle when all of the muscle fibres of motor unit contract simultaneously. Therefore, the greater the number of motor units active the greater the force on the tendon. For example, in eye movement motor units are usually smaller than motor units of leg movement. One motor unit contains 20 fibres and another has 5 fibres. If each fibre produce 1 gram of force, so the motor unit which contains more myofibrils will has more force than another one.
Specific tension is a functional measure of the number of myofibrils per unit of cross-section area. Given an accurate estimate of specific tension, the maximum force a muscle (Fm) can exert is estimated form (Enoka, 2002).
Fm = specific tension cross-section area
Muscle physiology in spasticity
Spasticity is the impairment that is associated with upper motor neuron syndrome, and is positive phenomena. The positive impairments are additional whereas negative impairments are lost such as loss strength and dexterity. Spastic patients have hypertonic contractions that are due to a dysfunction in their upper motor neuron (the cerebral) which causes a lack of inhibition of the spinal reflex, resulting in the motor neuron the afferent unit cannot do its function. The gamma motor neuron will receive too many contract commands thus, the hypertonicity results. Furthermore, the overreacting spastic muscle also affects to inhibit the antagonist muscle on the opposite side of the joint from the spastic muscle. The loss of orderly recruitment and rate modulation of motoneuron within a given motoneuron pool leads to inefficient muscle activation, inducing early loss of force, augment subject effort and the clinical perception of weakness (Katz, 1994).
Spasticity can be a result of cerebral and spinal lesions. There are some differences between them: spasticity with cerebral lesions tends to be less severe and more often involve the extensors with a posture of lower limb extension. Flexor spasms are rare and the clasp-knife phenomenon (an increased tone in either flexion or extension with sudden relaxation, as the muscle continues to be stretched) is uncommon. In many children with spasticity, the end result is a difficult situation in that both the spastic and the non-spastic muscle are weaker than normal and also their absolute power is often significantly lower than normal (Paterson, 2004). The unbalanced pull of the shorter spastic muscle causes biomechanical problems in children with CP. Asymmetrical pull of spastic muscle in spastic patients has orthopedic problems because of the interaction of the abnormal neurologic system with the muscles, joints and soft tissues. The abnormal, usually unbalanced, pull of spastic muscles coupled with lack of normal movement and weight bearing can lose flexibility and the range of motion (Evans, 1995).
Spasticity is different from rigidity, although both include involuntary increase in muscle tone, spasticity generally occurs only during muscle stretch and it usually accompanied by increase tendon reflexes and a Babinski's response (Gelber and Jeffery, 2002). Spastic CP is anatomically distributed into three types as can be seen in table XX. The most common movement patterns in spastic hemiplegia are arm flexion and foot extension pattern, in diplegia flexion or extension pattern of the lower extremities and in tetraplgia or quadriplegia flexion or extension pattern of all four limbs (Lieber, 1990).
(CP Symptom Organisation,(2009)
Measurement of spasticity
A wide variety of motor dysfunctions in patients with spasticity are not simply. Also, the quantifying of the spasticity has been a difficult and challenging problem. There are many ways to quantify the spasticity: clinical examination, tabulation of functional activities and electromyographical analysis.
1) Ashworth Scale (Ashworth,1964 cited by (Damiano et al., 2002)
To perform this test, move the body part through the joint range of motion. No speed of movement is specified.
0 No increase in tone
1 Slight increase in tone, giving a "catch" when the limb is moved in flexion or extension
2 More marked increase in tone, but limb easily flexed
3 Considerable increase in tone; passive movement difficult
4 Limb rigid in flexion or extension
2) Modified Ashworth Scale for grading Spasticity (Bohannon, 1987)
Grade
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 part(s) is moved in flexion or extension
2
Slight increase in muscle tone, manifested by a catch, followed by minimal resistance throughout the remainder (less than half) of the range of movement (ROM)
3
More marked increase in muscle tone through most of ROM, but affected part(s) easily moved
4
Considerable increase in muscle tone, passive movement difficult
5
Affected part(s) rigid in flexion and extension
3) Tardieu Scale (Markey, 2004)
The test is performed with patient in the supine position, with head in midline. This is measurement of the movement in the 3 different velocities (V1, V2, and V3). Responses are recorded at each velocity as X/Y, with X indicating the 0 to 5 rating, and Y indicating the degree of angle at which the muscle reaction occurs. By moving the limb at different velocities, the response to stretch can be more easily gauged since the stretch reflex responds differently to velocity.
V1: As slow as possible, slower than the natural drop of the limb segment under gravity
V2: Speed of limb segment falling under gravity
V3: As fast as possible, faster than the rate of the natural drop of the limb segment under gravity
Scoring
0 No resistance throughout the course of the passive movement
1 Slight resistance throughout the course of passive movement, no clear catch at a precise angle
2 Clear catch at a precise angle, interrupting the passive movement, followed by release
3 Fatigable clonus with less than 10 seconds when maintaining the pressure and appearing at the precise angle
4 Unfatigable clonus with more than 10 seconds when maintaining the pressure and appearing at a precise angle
5 Joint is immovable
4) The pendulum test
The pendulum test is a simple test that is used to quantify spasticity in knee muscles (Cavorzin et al., 2001). It is the test with the subject sitting on a chair. The feet are dropped on position of above the ground and the shanks have freedom to swing (freely between flexion and extension). Electro-goniometric recording of motion and oscillation is performed. In figure XX, during the pendulum test, Starting position is extended leg and at final position is flexed leg. The numbers are the skin reference markers: 1, 2/3 thigh; 2, lateral femoral condyle; 3, head of fibula; 4, lateral malleolus.
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Figure 7: Pendulum test (Valle et al., 2006)
5) Electromyography (EMG)
EMG is the measurement of the electrical activity of a muscle in contraction which is synthesised by linearly summing the motor unit action potential. There are two kinds of EMG namely needle EMG and surface EMG.
The EMG signal is the electrical demonstration of the neuromuscular activation associated with a muscle in contraction. It is synthesised by linear summation of the motor unit action potential. A variety of abnormal patterns of EMG activation have been described in person with spasticity. These include inefficient muscle activation with abnormal EMG force relationships, disturbances of spatial selection of muscle and alterations in time-course of EMG activation in agonist and antagonist muscles (Katz, 1994).
The high threshold motor units with rapid rates of adaptation are evidently recruited early and the fast twitch units are poorly suited to maintain sustained muscle contractions. Increasing in mean motor unit discharge rates in paretic muscle maybe the cause of abnormal EMG force generated. And the important appearance in EMG evaluation of spastic patients is an alteration in the time course of EMG activation in the contraction of the antagonism process. Because of the dysfunction of motor neuron, the agonist muscle is activated by too many contract messages.
6) The Hoffman or H-reflex
The Hoffman or H-reflex can be used to measure spasticity. The H-reflex is the electrical equivalent of the monosynaptic reflex. Recording the resultant reflex compound muscle action potential from a target muscle is used by an EMG electrode.
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Figure 11: Hoffman or H-reflex (Rossi et al., 2007)
The stimulus travels along the fibres, through the dorsal root ganglion, and is transmitted across the central synapse to the anterior horn cell which fires it down along the alpha motor axon to the muscle. A common measured H-reflex is obtained by stimulating the tibial nerve in popliteal fossa, eliciting a reflex response in the triceps surae muscle (Basmajian, 1978).
Treatment of spasticity
Treatment of spasticity is complex because each movement involves numerous muscles. Those are of biomechanical importance in each flexion spasticity includes the various muscles involved and respective therapeutic goals vary widely between patients.
The goals of spasticity treatment are to relieve the symptoms of spasticity and to protect patients from the effects of spasticity such as painful or abnormal posture and to perform better in activities of daily living. Massage and stretching provide only temporary relief from spasticity, but for everyday management, a balanced of stretching and strengthening exercises must always be implemented by the spastic person. Stretching improve flexibility, the ability to move the parts of the body through the full range of motion. Strengthening exercises help decrease muscle tone and improve the quality of muscles. Effectively, stretching routines must be done regularly, usually once or twice a day. Stretches should be as far as possible and held 10 seconds and then eased back. Each stretch should be performed slowly, with no sudden jerking or bouncing (Fink, 2009). Stretching and strengthening exercises are also needed to prevent contractures.
Treatment may also include medications and surgery. There are several medications that may be of help such as Baclofen, Tizanidine, Dantrolene, Botulinum Toxin and Diazepam. A surgical procedure called a radiofrequency rhizotomy is sometimes indicated in the treatment of severe spasticity (Tilton, 2009). The prognosis for those with spasticity depends on the severity of the spasticity and the associated disorders. To a small degree spasticity performs the helpful role of exercise, but it is usually bothersome to normal activities in life.
Characteristic of Movement patterns in children who have CP are typically slow, stiff and not smooth movements due to lack of sufficient motor function. This not only affects a child's ability to control posture and movement. In addition some children with CP also have visual, speech impairments and/or mental retardation (Sharma et al., 1999). One-third of children with CP have severe CP (Krägeloh-Mann and Cans, 2009), a number of persons with severe CP are completely disabled and require lifelong care. In the SCPE study, 35.2% of children with spastic CP were unable to walk and 23.5% of children had severe mental retardation (intelligence quotient <50). Three-fourth of severe CP children cannot walk and they have to use wheelchairs to aid their mobility and support their activities of daily living (ADL).
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