AUTHOR AND EDITOR INFORMATION

Section 1 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

INTRODUCTION

Section 2 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

Background

Cerebral palsy is a group of disorders affecting the development of movement and posture that are believed to arise from nonprogressive disturbances in the developing fetal or infant brain. In addition to the motor disorders that characterize cerebral palsy, which limit a patient's activities, individuals with cerebral palsy often display epilepsy, secondary musculoskeletal problems, and disturbances of sensation, perception, cognition, communication, and behavior.¹ (See also Models of Cerebral Palsy: Which Ones Are the Best?, on Medscape.)

Cerebral palsy has traditionally been classified on the basis of the type of motor disorder that occurs, with variable numbers and descriptions of types.² The revised classification now in use defines 3 main categories of motor disorder, as follows:

• Spastic - 70-80%
• Dyskinetic - 10-15%
• Ataxic - <5%

There are also mixed types.

Spastic cases are further classified according to involvement of the extremities, as follows³:

• Quadriplegia - 10-15%; all 4 extremities are affected, and the trunk is involved.
• Diplegia - 30-40%; the lower extremities are affected more than the upper extremities and in some cases are solely involved.
• Hemiplegia - 20-30%; involvement is observed on 1 side of the body, including an arm and a leg, with the arm more involved than the leg. If both arms are more involved than the legs, the condition can be classified as a double hemiplegia.
• Monoplegia - Rare; involvement is noted in 1 limb, either an arm or a leg. If a patient has monoplegia, an effort should be made to rule out causes other than cerebral palsy.

See also the eMedicine articles Cerebral Palsy (in the Neurology section), Spasticity (in the Physical Medicine and Rehabilitation Section) and Spasticity (in the Neurology section).

Pathophysiology

Cerebral palsy is caused by an insult to the immature brain; the period during which the insult can occur ranges from any time before birth up to the postnatal period.⁴ (Some classify cerebral palsy as an insult to the brain before age 3 years.) After the immediate postnatal period, cerebral palsy often has an identifiable cause (eg, hypoxic ischemic encephalopathy), which should be noted. The cerebral insult alters muscle tone, muscle stretch reflexes, primitive reflexes, and postural reactions. Other associated symptoms may be involved secondary to the neurologic insult (eg, mental retardation, vision and hearing problems, seizures), but they are not part of the definition of cerebral palsy.

The etiology of the cerebral insults includes vascular, hypoxic-ischemic, metabolic, infectious, toxic, teratogenic, traumatic, and genetic causes. The pathogenesis of cerebral palsy involves multifactorial causes, but much is still unknown. Different pathogenetic mechanisms of cerebral palsy have been associated with preterm and term births. In many cases, a cause cannot be accurately determined. Some believe that a pre-existing condition in some fetuses causes early birth and neurologic problems, as opposed to the prematurity itself causing cerebral palsy.

Frequency

United States

The prevalence of cerebral palsy is approximately 1.5-2 cases per 1000 live births. The incidence of cerebral palsy has not changed in more than 4 decades, despite significant advances in the medical care of neonates.

International

The prevalence of cerebral palsy is approximately 1.5-2 cases per 1000 live births.

Mortality/Morbidity

Cerebral palsy is the leading cause of childhood disability affecting function and development.

Age

The insult that gives rise to cerebral palsy occurs during immature brain development. According to most references, this initiating event can take place anytime between prenatal development and age 3 years. However, children are usually not diagnosed until after age 1 year, with the condition becoming identifiable as children fail to meet developmental milestones.  Often, children who are older and are diagnosed as having cerebral palsy—as a result of having presenting symptoms or problems that are similar to those of cerebral palsy—should instead be labeled with the etiology of their brain injury (ie, traumatic brain injury secondary to a motor vehicle accident, stroke, metabolic condition, etc.)

CLINICAL

Section 3 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

History

• The child with cerebral palsy can present after failing to meet expected developmental milestones or to suppress obligatory primitive reflexes.
• Abnormal muscle tone is the most frequently observed symptom. The child may present as either hypotonic or, more commonly, hypertonic with either decreased or increased resistance to passive movements, respectively. Children with cerebral palsy may have an early period of hypotonia followed by hypertonia. The longer the period of hypotonia prior to hypertonia, the greater the likelihood that the hypertonia will be more severe.
• Definite hand preference before age 1 year is a red flag for possible hemiplegia.
• Asymmetric crawling or failure to crawl also may suggest cerebral palsy.
• Growth disturbance is noted in children with cerebral palsy, especially failure to thrive.

Physical

• Joint contractures secondary to spastic muscles
• Hypotonic to spastic tone
• Growth delay
• Persistent primitive reflexes - Examples such as the Moro, asymmetric tonic neck, symmetric tonic neck, palmar grasp, tonic labyrinthine, and foot placement reflexes are noted. The Moro and tonic labyrinthine reflexes should extinguish by the time the infant is aged 4-6 months; the palmar grasp reflex, by 5-6 months; the asymmetric and symmetric tonic neck reflexes, by 6-7 months; and the foot placement reflex, before 12 months.
• The overall gait pattern should be observed and each joint in the lower extremity and upper extremity should be assessed.
• • Hip - Excessive flexion, adduction, and femoral anteversion make up the predominant motor pattern. Scissoring of the legs is common in spastic cerebral palsy.
  • Knee - Flexion and extension with valgus or varus stress occur.
  • Foot - Equinus, or toe walking, and varus or valgus of the hindfoot is common in cerebral palsy.
• Gait abnormalities may include the crouch position with tight hip flexors and hamstrings, weak quadriceps, and/or excessive dorsiflexion.
• Physical attributes of different types of cerebral palsy
• • The spastic type (pyramidal cerebral palsy) constitutes 75% of patients with cerebral palsy. Patients have signs of upper motor neuron involvement, including hyperreflexia, clonus, extensor Babinski response, persistent primitive reflexes, and overflow reflexes (that is, crossed adductor). Cognitive impairment is present in approximately 30% of spastic diplegic patients, but most patients with spastic quadriplegia have some cognitive impairment.
  • The dyskinetic type (extrapyramidal cerebral palsy) is characterized by extrapyramidal movement patterns, abnormal regulation of tone, abnormal postural control, and coordination deficits. Athetosis, chorea, and choreoathetoid or dystonic movements can be seen. Patients often have pseudobulbar involvement, with dysarthria, swallowing difficulties, drooling, oromotor difficulties, and abnormal speech patterns. Generally, patients are hypotonic at birth, with abnormal movement patterns emerging at 1-3 years. The arms are usually more involved than the legs. Abnormal movement patterns may increase with stress or purposeful activity. Muscle tone is normal during sleep. Intelligence is normal in 78% of patients with athetoid cerebral palsy. A high incidence of sensorineural hearing loss is reported.
  • Patients with spastic diplegia often have a period of hypotonia followed by extensor spasticity in the lower extremities, with little or no functional limitation of the upper extremities. Patients have a delay in developing gross motor skills. Spastic muscle imbalance often causes persistence of infantile coxa valga and femoral anteversion. A scissoring gait (ie, hips flexed and adducted, knees flexed with valgus stress, equinus ankles) is observed.
  • Hemiplegia is characterized by weak hip flexion and ankle dorsiflexion, an overactive posterior tibialis muscle, hip hiking/circumduction, supinated foot in stance, upper extremity posturing (that is, often held with the shoulder adducted, elbow flexed, forearm pronated, wrist flexed, hand clenched in a fist with the thumb in the palm), impaired sensation, impaired 2-point discrimination, and/or impaired position sense. Some cognitive impairment is found in about 28% of these patients.

Causes

• Prenatal
• • Intrauterine infections
  • Congenital malformations
  • Toxic or teratogenic agents
  • Multiple births
  • Abdominal trauma
  • Maternal illness
• Neonatal
• • Prematurity (less than 32 weeks' gestation)
  • Birthweight less than 2500 g
  • Growth retardation
  • Intracranial hemorrhage
  • Trauma
  • Infection
  • Bradycardia and hypoxia
  • Seizures
  • Hyperbilirubinemia
  • Abnormal birthing presentations
• Postnatal
• • Trauma
  • Infection
  • Intracranial hemorrhage
  • Coagulopathies

DIFFERENTIALS

Section 4 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

Other Problems to Be Considered

Metabolic and genetic diseases

WORKUP

Section 5 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

Lab Studies

• There are no definite lab studies for diagnosing cerebral palsy, only studies to rule out other symptom causes, such as metabolic or genetic abnormalities, as deemed necessary based on clinical examination.
• • Thyroid studies
  • Lactate level
  • Pyruvate level
  • Organic and amino acids
  • Chromosomes
  • Cerebrospinal protein - Levels may assist in determining asphyxia in the neonatal period. Protein levels can be elevated, as can the lactate-to-pyruvate ratio.

Imaging Studies

• Neuroimaging studies can help to evaluate brain damage and to identify persons who are at risk for cerebral palsy. Data to support a definitive diagnosis of cerebral palsy are lacking.
• • Neonatal ultrasonography provides information about the ventricular system, basal ganglia, and corpus callosum, as well as diagnostic information on intraventricular hemorrhage and hypoxic-ischemic injury to the periventricular white matter. Periventricular leukomalacia initially appears as an echodense area that converts to an echolucent area when the patient is aged approximately 2 weeks. Periventricular leukomalacia is strongly associated with cerebral palsy. (See also the eMedicine articles Periventricular Leukomalacia [in the Radiology section] and Periventricular Leukomalacia [in the Pediatrics: Cardiac Disease and Critical Care Medicine: Neonatology section].)
  • Computed tomography (CT) scanning provides information to help in diagnosing congenital malformations, intracranial hemorrhages, and periventricular leukomalacia, especially in the infant.
  • Magnetic resonance imaging (MRI) is most useful after 2-3 weeks of life. MRI is the best study for assessing white matter disease in an older child.
  • Evoked potentials are used to evaluate the anatomic pathways of the auditory and visual systems.
  • A normal brain imaging study does not mean that the child does not have cerebral palsy, since the diagnosis is always based only on physical exam findings.

Other Tests

• Hearing and vision screens may be helpful.
• Electroencephalography is useful in evaluating severe hypoxic-ischemic injury. Findings initially show marked suppression of amplitude and slowing, followed by a discontinuous pattern of voltage suppression, with bursts of high-voltage sharp and slow waves at 24-48 hours.

TREATMENT

Section 6 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

Rehabilitation Program

Physical Therapy

Treatment is aimed at improving infant-caregiver interaction, giving family support, supplying resources, and providing parental education, as well as at promoting motor and developmental skills. The parent or caregiver should be taught the exercises or activities that are necessary to help the child reach his or her full potential and improve function.⁵

Daily range-of-motion (ROM) exercises are important to prevent or delay contractures that are secondary to spasticity and to maintain the mobility of joints and soft tissues. Stretching exercises are performed to increase motion. Progressive resistance exercises should be taught in order to increase strength. The use of age-appropriate play and of adaptive toys and games based on the desired exercises are important to elicit the child's full cooperation. Strengthening knee extensor muscles helps to improve crouching and stride length. Postural and motor control training is important and should follow the developmental sequence of normal children (that is, head and neck control should be achieved, if possible, before advancing to trunk control).

The child's developmental age should always be kept in mind, and adaptive equipment should be used as needed to help the child achieve his or her milestones. For example, if a child is developmentally ready to stand and explore the environment but is limited by a lack of motor control, the use of a stander should be encouraged to facilitate the achievement of the youngster's milestones. Performance should be encouraged at a level of success to maintain the child's interest and cooperation, and assistive devices and durable medical equipment should be ordered to attain function that may not otherwise be possible.

Orthoses are frequently required to maintain functional joint position in the upper and lower extremities, especially in nonambulatory or hemiplegic patients. Frequent reevaluation of orthotic devices is important because children quickly outgrow them and can undergo skin breakdown from improper use of this equipment.

Splints should be worn as much as possible without causing skin breakdown (at least 6 hours to provide a good stretch or sometimes a schedule of 2 hours on, 1 hour off throughout the day). Orthoses can become especially important in ambulatory cerebral palsy to improve gait, decrease contracture, and increase endurance. Patients with cerebral palsy have a very inefficient gait pattern, and there can be an energy expenditure gain of as much as 350%. Orthoses can be of great benefit, and while wearing them, patients can potentially suffer fewer trips and falls.

Patients and their parents often like hippotherapy (horseback-riding therapy) to help improve the child's tone, ROM, strength, coordination, and balance. Hippotherapy offers many potential cognitive, physical, and emotional benefits.

Aquatic therapy can be beneficial for strengthening.

Occupational Therapy

Occupational therapy should focus on the activities of daily living, such as feeding, dressing, toileting, and grooming. The goal should be for the child to function as independently as possible with or without the use of adaptive equipment. See also Physical Therapy.

Speech Therapy

Many children with dyskinetic cerebral palsy and some with spastic cerebral palsy have involvement of the face and oropharynx, causing dysphagia, drooling, and dysarthria. Speech therapy can be implemented to help improve swallowing and communication. Some children benefit from augmentative communication devices if they have some motor control and adequate cognitive skills. Patients with athetoid cerebral palsy may benefit the most from speech therapy, because most of these individuals have normal intelligence, and communication is an obstacle that is secondary to the effect of athetosis on speech. Adequate communication is probably the most important goal for enhancing function in a patient with athetoid cerebral palsy.

Recreational Therapy

Incorporation of play into all of a child's therapies is important. The child should view physical and occupational therapy as fun, not work. Caregivers should seek fun and creative ways to stimulate children, especially those who have a decreased ability to explore their own environment.

Medical Issues/Complications

• Spasticity and/or contractures
• Pulmonary complications - Including aspiration, oromotor dysfunction, bronchopulmonary dysplasia (seen in premature infants)
• Dental problems - Including enamel dysgenesis, malocclusion, caries, gingival hyperplasia (Malocclusion is twice as prevalent as in the normal population.)
• GI symptoms (eg, reflux, constipation) and/or dysphagia - May cause failure to thrive, resulting in growth failure; patients may require a gastrostomy tube (G-tube) or a jejunostomy tube (J-tube) to augment nutrition. Nutrition consultation should be done early and periodically to ensure proper growth. Parents and medical professionals must keep on top of the potential nutritional difficulties in children with cerebral palsy. These patients are especially at risk of developing osteoporosis because of decreased weight bearing, so following their calcium intake is important.⁶
• Mental retardation - Seen in 30-50% of children with cerebral palsy, most commonly associated with spastic quadriplegia
• Hearing loss - Especially in children with hyperbilirubinemia; also seen in patients who were born prematurely or who were exposed to ototoxic drugs
• Spasticity - Causes stress on the joints, leading to misalignment, especially in the hips and spine
• Scoliosis and kyphosis
• Dislocated hips
• Pain
• Neglect - More prevalent than in the normal population
• Failure to thrive/malnutrition
• Osteoporosis
• Social isolation

Surgical Intervention

• Scoliosis and hip dislocation - The most common conditions requiring surgery.
• • Scoliosis repair
  • Hip relocation surgery for dislocations
• Tendon lengthening or transfer - To decrease spastic muscle imbalance and deforming forces
• Osteotomy to realign limb - Including the femoral neck, tibia, and calcaneus
• Intrathecal insertion of a baclofen pump to treat spasticity - Useful in the patient with diffuse spasticity; the baclofen pump is most useful to help decrease spasticity in the lower extremities and trunk, but it can also decrease spasticity in the upper extremities and improve speech. The degree of improvement in the upper extremities is increased with higher placement of the pump catheter. The dose can be continuously adjusted, with different doses during the day and evening, depending on the patient's needs. The patient requires surgery for placement of the pump and then monthly appointments to refill the pump with intrathecal baclofen.
• Selective posterior rhizotomy to treat velocity-dependent spasticity - Includes a laminectomy and then surgical ablation of 70-90% of the dorsal or sensory nerve roots.
• • Gait analysis has revealed improved ROM at the knee and hip with improved stride length.
  • Patients must be selected carefully because the weakness produced may decrease the level of functional independence.
  • This surgery has come to be performed less frequently since the advent of the baclofen pump. 
  • Because of the laminectomies, some of the earlier surgeries had complications of more severe lumbar lordosis several years after surgery.

See also Selection of Treatment Modalities in Children With Spastic Cerebral Palsy, on Medscape.

Consultations

• A neurologist may help with differential diagnosis and with ruling out other neurologic disorders. Consultation with a neurologist may also be helpful in the treatment of patients with seizures.
• A specialist in genetics may help with the differential diagnosis and with ruling out other disorders.
• An orthopedic surgeon may be needed to help correct any structural deformities.
• Consultation with an ophthalmologist may be indicated for follow-up of any patient experiencing visual deficits.
• An audiologist may help to screen for hearing deficits.
• A pulmonologist may help to treat the patient who has bronchopulmonary dysplasia or frequent aspiration pneumonia.
• A gastroenterologist may help with reflux and constipation and may aid in coordinating feedings to regulate weight gain or loss, if needed. A G-tube or J-tube also may be needed to help augment nutrition. A periodic nutrition consultation is important to make sure that the child does not suffer from growth failure or nutritional deficiencies.
• Regular dental visits are important.
• And endocrinologist is occasionally needed for precocious puberty or treatment of osteoporosis.

Other Treatment

• Orthotic devices may help to control limb position during gait; also, if appropriate seating is needed, a wheelchair and mobility aids may help.
• • A manual wheelchair may be needed, with seating adaptations included to keep the back straight and protect the hips from excessive adduction or abduction. The early introduction of independent mobility is important because the ability to explore one's environment has been demonstrated to improve self-esteem.
  • A power wheelchair may be needed for children with severe spasticity or athetosis. A power wheelchair can be introduced to children aged 3 years who have normal intelligence. However, a child needs to understand the concept of cause and effect to use the device appropriately.
  • Orthotic devices such as an ankle-foot orthosis help to maintain foot position and prevent worsening contractures.
  • Walkers also may be prescribed to enhance mobility. Any child with the ability and/or desire to ambulate should be given every opportunity to do so. A posterior walker promotes a more upright posture than do traditional walkers.
• Phenol intramuscular neurolysis and botulinum toxin intramuscular blocks reduce spasticity for 3-6 months.⁷
• • The established total body dose of botulinum toxin is limited to 12 U/kg, to a maximum of 400 U per visit. (Many practices, however, have been safely using 20 U/kg, to a maximum of 600 U). Each small muscle receives 1-2 U/kg, and large muscles, 4-6 U/kg. The interval between doses should be at least 4 months in order to help prevent antibody formation, which could make subsequent botulinum toxin procedures less effective. (See also The Use of Botulinum Toxin Therapy For Lower-Extremity Spasticity in Children With Cerebral Palsy, on Medscape.)
  • Large muscles may not respond to this limiting dose, or quite often, patients need several muscles done at each visit.
  • Phenol can be used for some large muscles or when several muscles are treated, but this treatment is more difficult to administer than others. Because it is done using a nerve stimulator, phenol treatment is more painful.  The procedure is often performed with anesthesia. In certain nerves, phenol can cause unpleasant sensory dysesthesias.
• Short-term use of heat and cold over the tendon may help to decrease spasticity; vibration over the tendon also reduces spasticity. However, these treatments only decrease spasticity briefly and should be used in conjunction with ROM and stretching exercises.
• Casting and splinting can improve the ROM of a joint and decrease tone. This is particularly completed at the ankles to help with plantar flexion contractures, but it also can be done on any contracted joint to provide a slow, progressive stretch.

MEDICATION

Section 7 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

The goals of pharmacotherapy are to reduce morbidity and prevent complications.

Drug Category: Skeletal Muscle Relaxants

These are thought to work centrally by suppressing conduction in the vestibular cerebellar pathways. They may have an inhibitory effect on the parasympathetic nervous system.

Drug Category: Benzodiazepines

These agents may act in the spinal cord to induce muscle relaxation.

Drug Category: Neuromuscular Blocker Agent, Toxin

These agents paralyze the muscle by blocking neurotransmitter release.

Drug Category: Alpha2 Adrenergic Agonist Agent

Tizanidine is an imidazoline derivative and a central alpha2 noradrenergic agonist. The antispasticity effects are the probable result H-reflex inhibition. The drug may facilitate the inhibitory actions of glycine, reduce the release of excitatory amino acids and substance P, and produce analgesic effects.

FOLLOW-UP

Section 8 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

Further Inpatient Care

• Patients who require intensive physical, occupational, and/or speech therapy may need to be admitted for rehabilitation.
• • Patients receive therapy in at least 2 disciplines for 3 hours/day.
  • This rehabilitation may be especially useful after orthopedic surgery or placement of a baclofen pump.

Deterrence

• Good prenatal care is one method of prevention, but it is not 100% successful, since numerous causes are associated with cerebral palsy, and much is still unknown. The prevalence rate has remained constant despite improved prenatal and perinatal care.

Prognosis

• Patients with spastic quadriplegia
• • About 25% of patients have minimal or no functional limitation in ambulation and self-care.
  • Approximately 50% of patients have moderate impairment and, although not independent, are able to function.
  • Nearly 25% of patients are severely impaired, require complete care, and are not ambulatory.
• About 50% of patients with dyskinesia are ambulatory.
• Most patients with hemiplegic cerebral palsy become independent in their activities of daily living, but they may need assistive devices. Almost 100% of patients become ambulatory.
• Molnar and colleagues reported that patients with cerebral palsy and spastic diplegia or quadriplegia who sat by age 2 years eventually walked. The suppression of obligatory primitive reflex activity by age 18-24 months was a sensitive indicator for distinguishing children who ultimately walked from those who were not expected to walk.

Patient Education

• For excellent patient education resources, visit eMedicine's Brain and Nervous System Center. Also, see eMedicine's patient education article Cerebral Palsy.

REFERENCES

Section 9 of 9

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

1. Bax M, Goldstein M, Rosenbaum P, et al. Proposed definition and classification of cerebral palsy, April 2005. Dev Med Child Neurol. Aug 2005;47(8):571-6. [Medline].
2. Badawi N, Watson L, Petterson B, et al. What constitutes cerebral palsy?. Dev Med Child Neurol. Aug 1998;40(8):520-7. [Medline].
3. Dabney KW, Lipton GE, Miller F. Cerebral palsy. Curr Opin Pediatr. Feb 1997;9(1):81-8. [Medline].
4. Jones MW, Morgan E, Shelton JE, et al. Cerebral palsy: introduction and diagnosis (part I). J Pediatr Health Care. May-Jun 2007;21(3):146-52. [Medline].
5. Mayston MJ. People with cerebral palsy: effects of and perspectives for therapy. Neural Plast. 2001;8(1-2):51-69. [Medline].
6. Verrall TC, Berenbaum S, Chad KE, et al. Children with cerebral palsy: caregivers' nutrition knowledge, attitudes and beliefs. Can J Diet Pract Res. 2000;61(3):128-34. [Medline].
7. Scholtes VA, Dallmeijer AJ, Knol DL, et al. The combined effect of lower-limb multilevel botulinum toxin type a and comprehensive rehabilitation on mobility in children with cerebral palsy: a randomized clinical trial. Arch Phys Med Rehabil. Dec 2006;87(12):1551-8. [Medline].
8. Abstracts of the 5th International Congress on Cerebral Palsy. Bled, Slovenia, 7-10 June 2001. Brain Dev. Jun 2001;23(3):145-93. [Medline].
9. Kuban KC, Leviton A. Cerebral palsy. N Engl J Med. Jan 20 1994;330(3):188-95. [Medline].
10. Matthews DJ, Wilson P. Cerebral palsy. In: Molnar GE, Alexander MA, eds. Pediatric Rehabilitation. 3^rd ed. Philadelphia, Pa: Hanley & Belfus; 1999:192-217.
11. Taketomo CT, Hodding JH, Kraus DM. Pediatric Dosage Handbook. 4^th ed. Cleveland, Ohio: Lexi-Comp; 1997.

Article Last Updated: Dec 18, 2007