Approach Considerations
The 2003 American Academy of Neurology (AAN) practice parameter on cerebral palsy suggests laboratory studies if: [24] (1) the clinical history or findings from neuroimaging do not indicate a specific structural abnormality, (2) additional and atypical features are present in the history or clinical examination, or (3) a brain malformation is detected in a child with cerebral palsy. In addition, diagnostic testing for coagulation disorders is recommended if a cerebral infarction is seen; however, available data were insufficient for guiding what precise studies should be ordered.
If a diagnosis of a hereditary or neurodegenerative disorder is suspected, screening for an underlying metabolic or genetic disorder should be performed. However, specific studies were not recommended by the AAN practice parameter as such studies should be guided by the clinical picture, such as clinical features suggestive of a particular syndrome. [24] However, since the 2003 practice parameter, there have been studies demonstrating clinically significant copy number variants on chromosomal microarray in patients with clinical diagnoses of cerebral palsy. These were found in patients with more severe motor impairment, dysmorphisms, or non-motor comorbidities as well as patients with cerebral palsy of unknown cause. [35, 36]
The AAN practice parameter did not recommend an electroencephalogram (EEG) unless suspicion for epilepsy or an epileptic syndrome is present, but it did recommend neuroimaging "to establish that a brain abnormality exists in children with cerebral palsy, that may, in turn, suggest an etiology and prognosis." [24] Note that a normal brain imaging study does not mean that the child does not have cerebral palsy, because the diagnosis is always based only on physical examination findings.
Potentially Helpful Laboratory Tests
There are no definitive laboratory 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. Such studies may include the following:
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Thyroid function studies - Abnormal thyroid function may be related to abnormalities in muscle tone or deep tendon reflexes or to movement disorders.
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Lactate and pyruvate levels - Abnormalities may indicate an abnormality of energy metabolism (ie, mitochondrial cytopathy).
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Ammonia levels - Elevated ammonia levels may indicate liver dysfunction or urea cycle defect.
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Organic and amino acids - Serum quantitative amino acid and urine quantitative organic acid values may reveal inherited metabolic disorders.
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Chromosomal analysis - Chromosomal analysis, including karyotype analysis, chromosomal microarray, or specific DNA testing, may be indicated to rule out a genetic syndrome, particularly if dysmorphic features or abnormalities of various organ systems are present, or etiology of the cerebral palsy is undetermined.
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Cerebrospinal protein - Levels may assist in determining asphyxia in the neonatal period. Protein levels can be elevated, as can the lactate-to-pyruvate ratio.
Cranial 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.
Cranial ultrasonography performed in the early neonatal period can be helpful in medically unstable infants until they are able to tolerate transport for more detailed neuroimaging. Ultrasonography can delineate clear-cut structural abnormalities and show evidence of hemorrhage or hypoxic-ischemic injury. For example, neonatal cranial 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 approximately age 2 weeks. Periventricular leukomalacia is strongly associated with cerebral palsy.
In infants, computed tomography (CT) scanning of the brain helps to identify congenital malformations, intracranial hemorrhage, and periventricular leukomalacia more clearly than ultrasonography.
Magnetic resonance imaging (MRI) of the brain is most useful after 2-3 weeks of life and is the diagnostic neuroimaging study of choice for older children, because this modality defines cortical and white matter structures and abnormalities more clearly than any other method. MRI also allows for the determination of appropriate myelination for a given age. In children with spasticity of the legs and worsening of bowel and bladder function, a spine MRI may help identify a tethered spinal cord.
Although the precise role for MRI in the diagnosis and workup of children with cerebral palsy or suspected cerebral palsy has not been fully elucidated, the literature suggests that MRI should be strongly considered in all cases; in one study, 89% children with cerebral palsy were found to have abnormal MRIs. [37] Additionally, MRI may have a role in predicting neurodevelopmental outcomes in preterm infants. [38] See the following images.
Magnetic resonance image (MRI) of a 1-year-old boy who was born at gestational week 27. The clinical examination was consistent with spastic diplegic cerebral palsy. Pseudocolpocephaly and decreased volume of the white matter posteriorly were consistent with periventricular leukomalacia. Evidence of diffuse polymicrogyria and thinning of the corpus callosum is noted in this image.
Magnetic resonance image (MRI) of a 16-month-old boy who was born at term but had an anoxic event at delivery. Examination findings were consistent with a spastic quadriplegic cerebral palsy with asymmetry (more prominent right-sided deficits). Cystic encephalomalacia in the left temporal and parietal regions, delayed myelination, decreased white matter volume, and enlarged ventricles can be seen in this image. These findings are most likely the sequelae of a neonatal insult (eg, periventricular leukomalacia with a superimposed left-sided cerebral infarct).
Magnetic resonance image (MRI) of a 9-day-old girl who was born at full term and had a perinatal hypoxic-ischemic event. Examination of the patient at 1 year revealed findings consistent with a mixed quadriparetic cerebral palsy notable for dystonia and spasticity. Severe hypoxic-ischemic injury to the medial aspect of the cerebellar hemispheres, medial temporal lobes, bilateral thalami, and bilateral corona radiata is observed in this image.
Head ultrasonography, CT scanning, and MRI may be helpful for diagnosing and monitoring findings of hydrocephalus.
Patients who present clinically with cerebral palsy may have normal results from brain imaging studies. Normal results from neuroimaging studies do not exclude a clinical diagnosis of this disorder. However, in these cases, other underlying metabolic and genetic etiologies should be considered and excluded before diagnosing a child with cerebral palsy.
Electroencephalography
Electroencephalography (EEG) 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. EEG can also be used to confirm a clinical diagnosis of epilepsy. However, EEG is not indicated if seizures are not suspected along with cerebral palsy.
EMG and Nerve Conduction Studies
Electromyography (EMG) and nerve conduction studies are helpful when a muscle or nerve disorder is suspected (eg, a hereditary motor or sensory neuropathy as a basis for equinus foot deformities and toe walking).
Evoked potentials are used to evaluate the anatomic pathways of the auditory and visual systems.
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Magnetic resonance image (MRI) of a 1-year-old boy who was born at gestational week 27. The clinical examination was consistent with spastic diplegic cerebral palsy. Pseudocolpocephaly and decreased volume of the white matter posteriorly were consistent with periventricular leukomalacia. Evidence of diffuse polymicrogyria and thinning of the corpus callosum is noted in this image.
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Magnetic resonance image (MRI) of a 16-month-old boy who was born at term but had an anoxic event at delivery. Examination findings were consistent with a spastic quadriplegic cerebral palsy with asymmetry (more prominent right-sided deficits). Cystic encephalomalacia in the left temporal and parietal regions, delayed myelination, decreased white matter volume, and enlarged ventricles can be seen in this image. These findings are most likely the sequelae of a neonatal insult (eg, periventricular leukomalacia with a superimposed left-sided cerebral infarct).
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Magnetic resonance image (MRI) of a 9-day-old girl who was born at full term and had a perinatal hypoxic-ischemic event. Examination of the patient at 1 year revealed findings consistent with a mixed quadriparetic cerebral palsy notable for dystonia and spasticity. Severe hypoxic-ischemic injury to the medial aspect of the cerebellar hemispheres, medial temporal lobes, bilateral thalami, and bilateral corona radiata is observed in this image.
