An Overview Of Cerebral Palsy And
Evolving Trends In Management

Daniel E. Shanks, M.D.
Daniel E. Shanks, M.D. is a Pediatric Neurologist with Nemours Children's Clinic, Jacksonville.

The developmental disabilities are a group of disorders differentiated by the pattern of delay among developmental streams. The four streams of development include language, problem solving, motor, and social. Cerebral palsy is a disorder of motor development. Common to the developmental disabilities, cerebral palsy is a static encephalopathy which is further characterized as a disorder of movement and posture associated with an abnormal pattern of persistent primitive reflexes and delayed evolution of postural reactions and consequent motor milestones. The prevalence of cerebral palsy is approximately 2 per 1000; however, with the increasing survival of very low birth weight (VLBW) premature infants, the prevalence appears to be increasing slightly. The prevalence of cerebral palsy in premature infants with birth weight less than 1500 grams is 60 per 1000. Although the risk of cerebral palsy is increased 30 fold compared to term infants, the vast majority of children who are VLBW do not have cerebral palsy.

This article will describe the classification of cerebral palsy, features which may alert the primary physician when to consider the possibility of cerebral palsy, examples of common conditions which may mimic cerebral palsy, and emerging trends in technology which offers a greater variety of therapeutic options.

Classification

Not all children with cerebral palsy have spastic quadriplegia. The classification is based on the predominant motor pattern. Two major categories are used in this scheme: spastic (pyramidal) and extrapyramidal. Approximately 65% of children with cerebral palsy have spastic cerebral palsy. The spastic group is further subdivided based on the pattern of body involvement. Quadriplegia involves all four extremities and should be further described if there is asymmetry in the degree of involvement among the extremities. Hemiplegia is restricted to one side of the body with the arm typically more severely involved than the leg. Diplegia involves the lower extremities predominantly, although there can be minor fine motor abnormalities. This is the most common pattern in premature infants. Occasionally a triplegic pattern is seen with a single upper extremity spared. This likely represents hemiplegia superimposed on diplegia. On occasion a monoplegia is seen and when in a lower extremity the differentiation from a spinal cord etiology can be very problematic.

Extrapyramidal cerebral palsy, comprising 25% of cases, almost always represents a quadriplegic pattern of involvement. The subdivisions of this group are based on the type of movement disorder which predominates: rigidity, dystonia, choeroathethosis, and ataxia. Although not a movement disorder, hypotonic cerebral palsy is included in the extrapyramidal group. Rigidity is the most common of this group that is difficult to differentiate from spasticity. The critical feature characterizing spasticity is velocity dependent increase of tone. The faster the attempt to passively move the joint, the greater the resistance. Gradual slow pressure produces movement more readily. There is also clasp knife effect: beyond a certain amount of stretch of the muscle, a sudden relaxation of the muscle allows movement more easily. The presence of a fixed contracture will interfere with the attempt to elicit these characteristics. Rigidity is characterized by consistent increased tone unrelated to speed of movement or joint position. Table 1 describes additional features differentiating spastic and extrapyramidal features. The final 10% of cases are classified as mixed, displaying prominent spastic and extrapyramidal features.

The proper classification of cerebral palsy is important for diagnostic and treatment purposes. The potential etiologies and differential diagnosis varies among the different subtypes of cerebral palsy. The details of a comprehensive diagnostic work-up for each type of cerebral palsy is beyond the scope of this paper. As treatment options increase, the proper characterization of the child's motor patterns becomes more important in selecting the most appropriate approach. Later in this paper, I will discuss the evolving options for treating spasticity.

When To Suspect Cerebral Palsy

Motor milestones are the most commonly used features to clinically monitor for cerebral palsy. Although these can be very informative, they are sometimes misleading. A developmental quotient can be calculated for motor skills (MQ), just as the intellectual quotient (IQ) reflects cognitive development:

MOTOR MILESTONES
MOTOR QUOTIENT = CHRONOLOGIC AGE X 100%

When calculating any developmental quotient in the first 24 months of age, half correction should be given for prematurity.¹ For example, a twelve month old who was two months premature would be assigned a chronological age in the denominator of eleven months. A MQ of 50 _ 70 % is a borderline to mild range whereas a MQ of less than 50% is usually associated with significant pathology. The failure to sit by 10 months or walk by 15 months should trigger consideration of further evaluation. For a comprehensive review of early motor milestones (gross motor and fine motor) as well as general developmental milestones, Capute and Accardo^{2, 3} are recommended.

Prior to twelve months of age, children should use both hands equally. The establishment of a clear hand preference prior to the first birthday is strongly suggestive of an abnormality of the "non-dominant" hand. Failure to use the upper extremity in the first months (usually days) of life suggests a peripheral nerve, spinal cord, or traumatic disorder. When an unexplained asymmetry is noted after three months (usually four to six months), a congenital hemiplegia should be suspected.

The persistence of primitive reflexes is often the earliest clue to the diagnosis of cerebral palsy and may allow identification in the first year of life.⁴ Primitive reflexes should gradually extinguish over the first six months. Prominent fisting, obligate positive support reflex, and obligate asymmetric tonic neck reflex are suggestive of spastic cerebral palsy. Prominent Moro (myoclonic reflex) and tonic labyrinthine reflexes, especially when they persist past six months, are early markers for extrapyramidal forms. Extrapyramidal movements are not present until the second year of life and do not necessarily represent a progression of disease, but instead a maturing to these movements in an infant who had previously been hypotonic. Details of the diagnostic features based on the neurodevelopmental exam can be found in review articles by Ingram⁵ and Illingsworth.⁶

Conditions Which Mimic Cerebral Palsy

By presenting two relatively common benign conditions which mimic cerebral palsy, an emphasis is placed on the need to remember all the features of the definition in the diagnosis of cerebral palsy, especially in early and mild cases. Many other less common conditions must also be borne in mind as part of the differential diagnosis for cerebral palsy. The first of the benign conditions is characterized by normal to high muscle tone and hyperreflexia in the first six months of life. This occurs most commonly in infants who were premature and whose motor system may be mildly disorganized. The infant is alert and is only mildly delayed. Prominent primitive reflexes and hard neurologic findings are absent. In the latter half of the first year, developmental progress normalizes.

The second condition often misidentified as cerebral palsy is benign congenital hypotonia. As the name implies, the child is floppy from birth but has no evidence of weakness and has easily elicitable DTR's. The motor DQ is approximately 70% for gross motor skills. Fine motor skills and other areas of development (language, social) are normal. The hypotonia appears less prominent with age and the prognosis is good without intervention. There is frequently a family history of a similar developmental pattern. The critical clue in both the hypertonic and hypotonic conditions is the uniformly good quality of skills when the gross motor skills emerge. These two groups were likely the patients who in earlier reports were considered to have "outgrown" their cerebral palsy.

Management

The basic approach to management of cerebral palsy remains the close collaboration among a wide range of specialties to address the often complex constellation of medical needs many have. For more information, reviews by Dormans & Pellegrimo⁷ and Batshaw⁸ are recommended. Batshaw⁹ also provides an excellent resource for parents.

Just as recent advances in technology have revolutionized many aspects of all our lives, it offers an ever enlarging array of new interventions for individuals with cerebral palsy. From polymers for making splints and braces, to mechanical advances allowing for better motorized wheelchairs, to computer advances which allow for better communication systems and academic participation, many new options are becoming available.¹⁰ It cannot be overemphasized that in addition to medical interventions, Physical and Occupational therapies remain a critical component in the comprehensive management of cerebral palsy.

One area which has seen an evolution of medical options for treatment is spasticity management. These include oral medications, intrathecal baclofen, neurolytic and neuromuscular blockade, and surgical procedures. The most commonly used oral medications to reduce spasticity are diazepam, baclofen, and dantrolene. Overall, oral treatment for spasticity due to cerebral palsy has been unsatisfactory with inconsistent and only partial improvement.¹¹ The dose required to produce a meaningful effect usually cannot be tolerated due to excess sedation.

Surgical options for treatment of spasticity include selective dorsal rhizotomy (SDR) and intrathecal baclofen infusion. Selective dorsal rhizotomy is a procedure in which a proportion of dorsal rootlets of the lumbosacral plexus are cut in order to interrupt the afferent reflex arc from muscle spindles to the spinal cord where they stimulate muscle contraction. The failure of the motor system from above to inhibit this reflex appropriately is the basis for spasticity. The procedure was initially used to treat cerebral palsy in 1913. It was subsequently repopularized by Peacock in the 1980's.¹² Accurate assessment of the child with cerebral palsy is essential, because significant extrapyramidal involvement is a contraindication for SDR. The ideal candidates appear to be early school age children with spastic diplegia related to prematurity who are ambulatory and have adequate cognitive ability to participate in vigorous post-rhizotomy physical therapy.⁷ Reports of efficacy are largely anecdotal. In a blinded controlled study, McLaughlin, et al¹³ compared a group of children who underwent SDR and intense physical therapy with a group receiving intense physical therapy alone. Although SDR reduced spasticity, the functional outcome of the groups was similar.

Limitations of SDR include the uncertainty of efficacy, the small percentage of children with cerebral palsy who are candidates, and its irreversibility. The effect of SDR also is often not maintained without indefinite aggressive physical therapy. Intrathecal baclofen by infusion appears to be supplanting some of the utility of SDR.

In the past five years, interest has been generated in the use of an implantable pump for the infusion of baclofen into the intrathecal space. Although efficacy of oral baclofen is disappointing, intrathecal administration is efficacious and well tolerated due to the extremely low dose utilized.¹⁴ The pump is generally implanted in the lower abdomen in a pouch which can be created in the subcutaneous tissue external to the abdominal musculature. A catheter is then tunneled subcutaneously to the spine where it is inserted into the subarachnoid space. The pump contains a reservoir where baclofen is stored. It also contains a computer chip which can be programmed using telemetry to set the infusion rate and pattern and to calculate remaining reservoir volume.

Intrathecal baclofen reliably reduces spasticity; however, the reduction in spasticity does not reliably improve functional outcome, especially in the more functionally mobile children with cerebral palsy. Intrathecal baclofen infusion has been more efficacious in more severely involved children where the reduced spasticity allows for greater comfort and makes care and positioning easier. Whether this will lead to less orthopedic complications and need for orthopedic surgical procedures has yet to be determined. Advantages over SDR include the ability to easily titrate the degree of tone reduction and reversibility. Prior to implantation, a test dose administered by lumbar puncture is given in order to determine response.

In addition to treating spasticity, intrathecal baclofen appears to be effective for dystonia, although higher doses are required.¹⁴ A beneficial effect on upper extremity tone and oral motor dysfunction may also be attained. As more experience is gained with intrathecal baclofen, a wider range of indications will likely be found.

In the early 1990's, botulinum toxin became available for treatment of spasticity in cerebral palsy. The toxin binds with the presynaptic axon terminal at the neuromuscular junction and blocks the release of acetylcholine. Although this is the toxin responsible for botulism, botulinum toxin is safe because the dose used is an order of magnitude smaller than would be required to produce systemic effects. Botulinum toxin binds readily to the neuromuscular junction and remains localized to the area of injection. Although the toxin produces an irreversible binding to the nerve ending, duration of effect is generally three to five months because the nerve sprouts new axon terminals. Numerous trials have demonstrated a reduction of spasticity in cerebral palsy.^{15, 16} Due to the limitations of dosing, the number of muscles which can be injected at a time is only two to three. Combined with aggressive physical therapy and sometimes serial casting, improved range of motion can generally be obtained. The goal is to improve range of motion and function in a less invasive manner than would be accomplished with surgical interventions. Fixed contractures and bony deformities do not respond to botulinum toxin injections.

Cerebral palsy remains a very challenging disability to manage, requiring multiple disciplines for the wide range of potential complications. A variety of new therapeutic options are becoming available for appropriately selected patients. Unfortunately, therapy is geared toward the secondary complications of this motor disorder. Presently, no therapy has been proven effective for the primary brain disorders responsible for cerebral palsy. Prevention of these disorders, when feasible, remains the only truly effective treatment.

REFERENCES

1. Blasco PA. Preterm Birth: To correct or not to Correct. Dev Med Child Neurol. 1989; 31: 816-821.
2. Capute AJ, Accardo PJ. The infant neurodevelopmental assessment: A clinical interpretive manual for CAT-CLAMS in the first two years of life, Part 1. Curr Probl Pediatr. 1996; 26:238-257.
3. Capute AJ, Accardo PJ. The infant neurodevelopmental assessment: A clinical interpretive Manual for CAT-CLAMS in the first two years of life, Part 2. Curr Probl Pediatr. 1996; 26: 279-306.
4. Capute AJ, Palmer FB, Shapiro BK. Primitive reflex profile: a quantitation of primitive reflexes in infancy. Develop Med Child Neurol. 1984; 26: 375-383.
5. Ingram TTS. The neurology of cerebral palsy. Arch Dis Child. 1966; 41: 337-357.
6. Illingsworth RS. The diagnosis of cerebral palsy in the first year of life. Develop Med Child Neurol. 1966; 8: 178-194.
7. Dormans JP, Pellegrino L (ed). Caring for Children with Cerebral Palsy: A Team Approach. Baltimore: Paul H. Brooks Publishing; 1998.
8. Batshaw M. Children with Disabilities. 4^th ed. Baltimore: Paul H Brooks Publishing; 1997.
9. Batshaw M. Your Child has a Disability. Boston: Little, Brown and Co.; 1991.
10. Adams RC, Snyder P. Treatment for cerebral palsy: Making choices of intervention from an expanding menu of options. Inf Young Children. 1998; 10: 1-22.
11. O'Donnell M, Armstrong R. Pharmacologic intervention for management of spasticity in cerebral palsy. Mental Retardation and Developmental Disabilities Research Reviews. 1997; 3: 204-211.
12. Hays RM, McLaughlin JF, Geiduschek JM, et al. Evaluation of the effects of selective dorsal rhizotomy. Mental Retardation and Developmental Disabilities Research Reviews. 1997; 3: 168-174.
13. McLaughlin JF, Bjornson KF, Astley SJ, et al. Selective dorsal rhizotomy: efficacy and safety in an investigator-masked clinical trial. 1998; 40:220-232.
14. Albright AL. Intrathecal baclofen in cerebral palsy movement disorders. J Child Neurol. 1996; 11 (Suppl 1): S29-S35.
15. Cossgrove AP, Corry IS, Graham HK. Botulinum toxin in the management o f the lower limb in cerebral palsy. Dev Med Child Neurol. 1994; 36: 386-396.
16. Wong V. Use of botulinum toxin injection in 17 children with spastic cerebral palsy. Pediatr Neurol. 1998; 18: 124-131.

March, 2000/ Jacksonville Medicine

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