Chapter 20 Alterations of Neurologic Function in Children PDF

CHAPTER 20- Alterations of Neurologic Function in Children Know when the neural tube forms during embryonic development. The nervous system develops from embryonic ectoderm through a complex and sequential process, including the formation of the neural tube (3 to 4 weeks gestation) Formation...

CHAPTER 20- Alterations of Neurologic Function in Children Know when the neural tube forms during embryonic development. The nervous system develops from embryonic ectoderm through a complex and sequential process, including the formation of the neural tube (3 to 4 weeks gestation) Formation of the neural tube begins between 3- and 4-weeks gestation as the neural plate folds to form a neural groove and neural folds. The neural groove deepens and closes dorsally to form the neural tube, which gives rise to the entire central nervous system (CNS). The neural tube closes first in the cervical region and then “zippers” in two directions—cranially and caudally Define encephalocele, meningocele, spina bifida, myelomeningocele. Where is the defect located in each? Defects of Neural Tube Closure are divided into two categories: Anterior midline defects (ventral induction) o Anterior midline defects may cause brain and face abnormalities in the holoprosencephaly spectrum, with the most extreme form being cyclopia, in which the child has a single midline orbit and eye with a protruding nose like proboscis above the orbit Posterior defects (dorsal induction) o ***Most common neural tube closure defect o Posterior defects result from failure of closure of the neural tube and result in a variety of myelodysplasias depending on the level of the failure. o Although myelodysplasia is defined as a defect in formation of the spinal cord, the term is used to refer to anomalies of both the vertebral column and the spinal cord Spina bifida:  Most common neural tube defect and includes anencephaly, encephalocele, meningocele, and myelomeningocele Originates during the first month of embryonic development when the neural tube fails to close completely Anencephaly: An anomaly in which the soft, bony component of the skull and part of the brain are missing. Relatively common disorder, with an incidence of approximately 1 per 4859 live births in the United States each year. These infants are stillborn or die within a few days after birth. The pathologic mechanism is unknown. Diagnosis is often made prenatally using ultrasound or evaluating maternal serum α-fetoprotein (AFP). Encephalocele: Refers to a herniation or protrusion of brain and meninges through a defect in the skull sac-like structure Occurs during the 1st weeks of pregnancy When defect contains only meninges → referred to as a cranial meningocele Meningocele Saclike cyst of meninges filled with spinal fluid and is a mild form of spina bifida. Develops during the first 4 weeks of pregnancy when the neural tube fails to close completely. The cystic dilation of meninges protrudes through a defect in the posterior arch of the vertebra. The vertebral defect does not involve the spinal cord or nerve roots and may produce no neurologic deficit or symptoms. Meningoceles occur with equal frequency in the cervical, thoracic, and lumbar spine. Cranial meningocele→ surgical repair of the cranial defect affords a good prognosis for most affected infants whose intellectual and motor functioning is usually normal. Myelomeningocele A hernial protrusion of a saclike cyst (containing meninges, spinal fluid, and a portion of the spinal cord with its nerves) through a defect in the posterior arch of a vertebra. One of the most common developmental anomalies of the nervous system. 80% percent of myelomeningoceles are in the lumbar and lumbosacral regions, the last regions of the neural tube to close. Hydrocephalus occurs in 85% of infants with myelomeningocele. Almost always associated type II Arnold-Chiari malformation (Chari II malformation). o This is a complex malformation of the brainstem and cerebellum in which the cerebellar tonsils are displaced downward into the cervical spinal canal, the upper medulla and lower pons are elongated and thin, and the medulla also is displaced downward and sometimes has a “kink”. o Associated with hydrocephalus from pressure that blocks CSF and syringomyelia (cause cyst in spinal canal) o Requires surgical decompression or placement of CSF shunt.  Chiari I - does not involve the brainstem and may be asymptomatic Chiari III - brainstem or cerebellum extends into high cervical myelomeningocele Chiari IV - lack of cerebellar development Until the myelomeningocele is surgically closed, cerebrospinal fluid (CSF) may accumulate, resulting in further dilation and enlargement of the sac, which may risk more damage to the nervous system. → Need surgical repair asap to prevent damage to the nervous system A child with a myelomeningocele will have motor, sensory, reflex, and autonomic function below the level of the lesion and will not have total paralysis Spina bifida occulta: Defect without any visible exposure of meninges or neural tissue Common and occurs to some degree in 10-25% of infants Usually causes no neurologic dysfunction because the spinal cord and spinal nerves are normal Surgical treatment is usually directed at associated intraspinal abnormalities that occur with growth of the child (tethered cord, sacral lipoma, or dermoid cyst). Tethered cord syndrome: may develop after surgical correction for myelomeningocele→ the cord becomes abnormally attached or tethered from scar tissue as the cord transcends the vertebral canal with growth Traction decreases blood flow and impairs oxidative metabolism. The cord can be untethered surgically. Meningoceles and myelomeningoceles Both associated with maternal folate deficiency and both occur on the backs of infants near the spine. Meningocele & myelomeningoceles are evident at birth as a pronounced skin defect on the infant's back. The bony prominences of the unfused neural arches can be palpated at the lateral border of the defect. Defect is usually covered by a transparent membrane that may have neural tissue attached to its inner surface. This membrane may be intact at birth or may leak cerebrospinal fluid (CSF), thereby increasing the risks of infection and neuronal damage. The spinal cord and nerve roots are malformed below the level of the lesion, resulting in loss of motor, sensory, reflex, and autonomic functions. A brief neurologic examination concentrating on motor function in the legs, reflexes, and sphincter tone is usually sufficient to determine the level above which spinal cord and nerve root function is preserved. This is useful to predict if the child will ambulate, require bladder catheterization, or be at high risk for developing scoliosis. Most cases of meningocele and myelomeningocele are diagnosed prenatally by a combination of maternal serologic testing (α-fetoprotein) and prenatal ultrasound. Elective cesarean section to minimize trauma during labor. Surgical repair is critical and can be performed by in utero fetal surgery or during the first 72 hours of life. Where is the defect located in encephalocele, meningocele, spina bifida, myelomeningocele? Encephalocele: herniation or protrusion of various amounts of brain and meninges through a defect in the skull, resulting in a saclike structure.  o Occurs during first weeks of pregnancy. Usually seen at birth as a midline skull defect through which a large mass protrudes; if the defect is located in the nasopharynx, no external anomaly is visible, but the child may experience nasal airway obstruction. o Most contain neural tissue as well as meninges, and occur in the occipital area, with the remainder found in the frontal, parietal, or nasopharyngeal areas. o On examination with a nasal speculum, a smooth, round mass will be visible in the nasal passages ▪ Frontal encephalocele-- extend into the orbit of the eye and produce proptosis on the affected side ▪ Occipital encephalocele---may be cause blindness and cognitive impairment. ▪ The size, location, and involvement of the encephalocele help determine a child's development and intellectual outcome. Spina bifida (“split spine”): occur because of an incompletely formed or absent posterior vertebral arch in the spinal column, allowing protrusion of either a saclike cyst of meninges filled with spinal fluid (meningocele) or a similar saclike cyst that also has neural tissue, spinal cord, or nerves in it (myelomeningocele). Meningocele: cyst-like dilation of meninges protruding through a defect in the posterior arch of the vertebrae; spinal cord intact (does not involve the spinal cord). Myelomeningocele: cystic dilation of meninges and protuberance of various amounts of the spinal cord through the vertebral defect and is associated with more severe complications; spinal cord NOT intact. Meningoceles and myelomeningoceles are both associated with maternal folate deficiency and both occur on the backs of infants near the spine. Pathophysiology, clinical manifestations and etiology of CEREBRAL PALSY Definition: a disorder of movement, muscle tone, or posture that is caused by injury or abnormal development in the immature brain, before, during, or after birth up to 1 year of age. Most common crippling disorder of childhood. Although cerebral palsy refers to motor deficits, associated ID, seizures, and other problems are common in children with this disorder. Pathophysiology: o Perinatal: anoxia, trauma, and infections are the most common factors that cause injury to the nervous system in this period. o Prenatal: impaired embryo implantation, chromosomal abnormalities, infection, trauma, radiation exposure, toxic substances, maternal toxemia, DM, maternal nutritional deficiencies, and premature labor. o Low birth weight and asphyxia are commonly identified as risk factors for cerebral palsy. o Vascular abnormalities, arterial or venous stasis, and thrombosis can occur as a result of tissue hypoxia or as unrelated structural alteration. o These anomalies may result in direct brain trauma that leads to infarction, intraventricular hemorrhage, and subarachnoid hemorrhage. o The use of intrathecal baclofen pumps, botulinum toxin, and selective dorsal rhizotomy for spasticity has led to improvement in selected children with cerebral palsy. o Etiology:  1. Genetic, teratogenic, and early pregnancy influences on the development of cerebral palsy are multifactorial and not yet fully understood 2. Several factors, alone or in combination, can produce brain damage that leads to cerebral palsy (see Table 20-4) Clinical manifestations (depends on type of cerebral palsy): Vision/hearing impairment Intellectual disability Seizures Swallowing problems Brain damage may affect the pyramidal system, causing spasticity, and leading to dyskinetic, ataxic, or hypotonic cerebral palsy. Pyramidal (spastic) cerebral palsy: Results from damage or defects in the brain’s corticospinal pathways (upper motor neuron) in either one or both hemispheres and accounts for approximately 70% to 80% of CP cases It is associated with increased muscle tone, prolonged primitive reflexes, exaggerated deep tendon reflexes, clonus rigidity of the extremities, scoliosis, and contractures. If spasticity occurs throughout the body, the child has spastic quadriparesis; if it occurs in one half, the child has hemiparetic cerebral palst. The later type can occur after stroke in the middle cerebral artery territory before or at the time of birth. Extrapyramindal (nonspastic) cerebral palsy: Caused by damage to cells in the basal ganglia, thalamus, or cerebellum and includes two subtypes: o Dyskinetic cerebral palsy: ▪ Associated with extreme difficulty in fine motor coordination and purposeful movements. ▪ Movements are jerky, uncontrolled, and abrupt, resulting from injury to the basal ganglia or thalamus (20% to 25% of CP cases). o Ataxic cerebral palsy: ▪ Associated with damage to the cerebellum and manifests with gait disturbances and instability ▪ Infants will have hypotonia at birth but will develop stiffness of the trunk muscles later infancy. ▪ This lack of flexibility exaggerates the infant’s inability to balance body position without support (approximately 5% of CP cases). o Some children may have symptoms each of these CP types, which leads to a mixed-variety disorder (13% of CP cases). Know pathophysiology, clinical manifestations and etiology of PKU. Definition: an example of an inborn error in the metabolism of amino acids (phenylalanine, to tyrosine). Etiology: Autosomal recessive inborn error in the metabolism of amino acids characterized by mutations of the phenylalanine hydroxylase (PAH) gene. Pathophysiology:  o Most natural food proteins contain about 15% of phenylalanine – the body uses tyrosine in the biosynthesis of protein, melanin, thyroxine, and the catecholamines in the brain and adrenal medulla. o Loss of PAH activity results in phenylalanine hydroxylase deficiency and the inability of the body to convert the essential amino acid phenylalanine to tyrosine, leading to the accumulation of phenylalanine in the serum. o This accumulation of phenylalanine and associated metabolites causes damage to the CNS. Clinical manifestations: o Most individuals with PKU appear normal at birth. If the newborn screening fails, progressive developmental delay is common presentation. o Other findings in untreated kids in later infancy and childhood may include developmental delay or ID, concomitant jerking movements, seizures, skin rashes, and attention problems, as well as vomiting, abnormally small head (microcephaly), musty odor in child’s breath/skin/ urine, eczema, self-mutilation, and severe behavioral problems. Because of the lack of tyrosine and its relationship to the biosynthesis of melanin, children with PKU have a characteristic phenotype that includes blond hair, blue eyes, and fair ski