Congenital disorders

Congenital disorders
Neurologic disorders present at birth can stem from a variety of maternal or fetal causes. For example, arteriovenous malformations result from abnormalities of the blood vessels in the brain. Some, such as cerebral palsy, result from prenatal, perinatal, or postnatal central nervous system damage. Others, such as hydrocephalus, result from cerebrospinal fluid dysfunction. Embryonic neural tube defects during the first trimester of pregnancy can lead to spinal cord malformations.
ARTERIOVENOUS MALFORMATION
Cerebral arteriovenous malformation (AVM) is a congenital disorder of the blood vessels consisting of an abnormal connection between the arteries and the veins in the brain and occur in approximately 3 out of 10,000 people. Although some AVMs may occur as a result of penetrating injuries, such as trauma, most are present at birth. Although subsequent symptoms may occur at any time, they typically occur between ages 10 and 20, with two-thirds of cases occurring before age 40. Evidence suggests that AVMs run in families, equally affecting males and females.
Pathophysiology
An AVM is a tangled mass of thin-walled, dilated blood vessels between arteries and veins that aren’t connected by capillaries and primarily occurs in the posterior portion of the cerebral hemispheres. Brain tissue perfusion is inadequate due to abnormal channels between the arterial and venous systems that allow mixing of oxygenated and unoxygenated blood, resulting in increased venous pressure, which causes engorgement and dilation of the venous structures. AVMs range in size from a few millimeters to large malformations that extend from the cerebral cortex to the ventricles. In fact, if the AVM is large enough, the shunting can deprive the surrounding tissue of adequate blood flow, resulting in cardiac decompensation— where the heart can’t pump enough blood to compensate for bleeding in the brain (typical in infants and small children). Thin-walled vessels may ooze small amounts of blood—they may even rupture—causing hemorrhage into the brain or subarachnoid space.
Complications
  • Development of cerebral aneurysm and subsequent rupture
  • Hemorrhage (intracerebral, subarachnoid, or subdural, depending on the location of the AVM)
  • Hydrocephalus
Assessment findings
In more than 50% of patients with AVM, hemorrhage (from rupture) from the malformation is the first symptom.
Symptoms that occur before an AVM rupture are related to slower bleeding from the abnormal vessels and may include:
  • chronic mild headache, a sudden and severe headache, or a localized or general headache
  • seizure
  • vision disturbances
  • muscle weakness or inability to move a limb or a side of the body
  • lack of sensation in part of the body, or abnormal sensations, such as ringing and numbness
  • mental status change (sleepy, stuporous, lethargic, confused, disoriented, or irritable)
  • stiff neck
  • impaired speech or sense of smell
  • fainting, dizziness, and decreased level of consciousness
  • facial paralysis, eyelid drooping, and tinnitus.
Diagnostic test results
  • Magnetic resonance imaging identifies irregular or globoid masses; however, hemorrhage may obscure findings.
  • Cerebral arteriogram confirms the presence of AVMs and evaluates blood flow.
  • Doppler ultrasonography reveals abnormal, turbulent blood flow.
  • Computed tomography scan identifies intracerebral hemorrhage and large AVMs.
Treatment
General support measures include aneurysm precautions to prevent possible rupture, which involves placing the patient on bed rest or limiting activity and maintaining a quiet atmosphere. Analgesics may be given for headache, and sedatives may be given to help calm the patient. Stool softeners may be given to prevent straining at defecation, which increases intracranial pressure. Anticonvulsants, such as phenytoin, may also be administered to prevent seizures.
A bleeding AVM is a medical emergency and requires immediate hospitalization. The goal of treatment is to prevent further complications by limiting bleeding, controlling seizures and, if possible, removing the AVM. Surgical techniques may include block dissection, laser, or ligation to repair the communicating channels and remove the feeding vessels. Surgery is dependent upon the accessibility and size of the lesion and the patient’s status.
Open brain surgery, embolization, and stereotactic radiosurgery may also be used separately or in any combination. Open brain surgery involves the actual removal of the malformation through an opening made in the skull. This type of surgery carries a higher risk because the surgery itself may cause the AVM to bleed uncontrollably.
DISCHARGE TEACHING
TEACHING THE PATIENT WITH AN AVM
Before discharge, teach the patient and his family:
  • about arteriovenous malformation (AVM) and its implications
  • about prescribed medication administration, dosage, possible adverse effects, and when to notify the physician
  • postoperative care of any incision
  • activity recommendations
  • signs and symptoms of complications, such as shunt infection or intracranial bleeding (sudden severe headache, vision changes, decreased movement in extremities, and change in level of consciousness)
  • the importance of follow-up care
  • the benefits of utilizing available community resources or support groups, especially if neurologic deficits have occurred.
If surgery isn’t possible—due to the size or location of the lesion—embolization or stereotactic radiosurgery may be performed to close the communicating channels and feeder vessels, thereby reducing blood flow to the AVM. Embolization involves injecting a gluelike substance into the abnormal vessels to stop aberrant blood flow into the AVM. Stereotactic radiosurgery is particularly useful for small, deep lesions, which are typically difficult to remove by surgery.
Nursing interventions
  • Monitor vital signs and titrate medications to control hypertension.
  • Monitor neurologic status.
  • Monitor for seizure activity and institute seizure precautions.
  • Maintain a quiet atmosphere and provide relaxation techniques.
  • Provide appropriate education to the parents (and patient if appropriate) before discharge. (See Teaching the patient with an AVM, page 189.)
CEREBRAL PALSY
Cerebral palsy (CP)—the most common crippling disease in children—includes several neuromuscular disorders resulting from prenatal, perinatal, or postnatal central nervous system damage. The three major types of CP include spastic, affecting approximately 70% of children; athetoid, affecting approximately 20%; and ataxic, affecting approximately 10%. Some types may occur in mixed forms. Motor impairment may be minimal (sometimes apparent only during physical activities such as running) or severely disabling. Associated defects, such as seizures, speech disorders, and mental retardation, are common.
Prenatal causes include Rh factor or ABO blood type incompatibility, maternal infection (especially rubella in the first trimester), maternal diabetes, irradiation, anoxia, toxemia, malnutrition, abnormal placental attachment, and isoimmunization.
Perinatal causes include trauma during delivery, depressed maternal vital signs from general or spinal anesthesia, asphyxia from the cord wrapping around the neck, prematurity, prolonged or unusually rapid labor, and multiple births (infants born last in a multiple birth have an especially high rate of CP).
Postnatal causes include infections, such as meningitis and encephalitis, head trauma, poisoning, and any condition that results in cerebral thrombus or embolus. (See Causes of cerebral palsy.)
Pathophysiology
In the early stages of brain development, a lesion or abnormality causes structural and functional defects that, in turn, cause impaired motor function and cognition. Even though defects are present at birth, signs and symptoms may not be apparent until months later, when the axons have become myelinated and the basal ganglia are mature.
CAUSES OF CEREBRAL PALSY
Conditions that result in cerebral anoxia, hemorrhage, or other damage may cause cerebral palsy (CP).
  • Prenatal conditions that may increase risk of CP: maternal infection (especially rubella), maternal drug ingestion, radiation, anoxia, toxemia, maternal diabetes, abnormal placental attachment, malnutrition, and isoimmunization.
  • Perinatal and birth difficulties that may increase the risk of CP: forceps delivery, breech presentation, placenta previa, abruptio placentae, metabolic or electrolyte disturbances, abnormal maternal vital signs from general or spinal anesthetic, prolapsed cord with delay in delivery of head, premature birth, prolonged or unusually rapid labor, and multiple birth (especially infants born last in a multiple birth).
  • Infection or trauma during infancy that may increase the risk of CP: poisoning, severe kernicterus resulting from erythroblastosis fetalis, brain infection, head trauma, prolonged anoxia, brain tumor, cerebral circulatory anomalies causing blood vessel rupture, and systemic disease resulting in cerebral thrombosis or embolus.
Complications
  • Contracture
  • Skin breakdown and ulcer formation
  • Muscle atrophy
  • Malnutrition
  • Seizure disorders (in about 25% of patients)
  • Speech, vision, and hearing problems
  • Language and perceptual deficits
  • Mental retardation (in up to 40% of patients)
  • Dental problems
  • Aspiration pneumonia
Assessment findings
Shortly after birth, the infant with CP may exhibit some typical signs and symptoms, including:
  • excessive lethargy or irritability
  • high-pitched cry
  • poor head control
  • weak sucking reflex
  • smaller than normal head circumference
  • abnormal postures
  • abnormal reflexes
  • abnormal muscle tone. (See Assessing signs of cerebral palsy.)
Findings for spastic CP include:
  • underdevelopment of affected limbs
  • characteristic scissors gait
  • hyperactive deep tendon reflexes and increased stretch reflexes
  • rapid alternating muscle contraction and relaxation
  • muscle weakness
  • muscle contraction in response to manipulation with a tendency toward contractures.
Findings for athetoid CP include:
  • involuntary movements, such as grimacing, wormlike writhing, dystonia, and sharp jerks that impair voluntary movement
  • involuntary facial movements (affects speech).
Findings for ataxic CP include:
  • lack of leg movement during infancy
  • wide gait
  • disturbed balance
  • incoordination (especially of the arms)
  • hypoactive reflexes
  • nystagmus
  • muscle weakness and tremors
  • lack of sudden or fine movements.
ASSESSING SIGNS OF CEREBRAL PALSY
Each type of cerebral palsy (CP) is manifested by specific findings. This chart highlights the major signs and symptoms associated with each type of CP. The manifestations reflect impaired upper motor rneuron function and disruption of the normal stretch reflex.

TYPE OF CP

SIGNS AND SYMPTOMS

Spastic CP (due to impairment of the pyramidal tract [most common type])

  • Hyperactive deep tendon reflexes

  • Increased stretch reflexes

  • Rapid alternating muscle contraction and relaxation

  • Muscle weakness

  • Underdevelopment of affected limbs

  • Muscle contraction in response to manipulation

  • Tendency toward contractures

  • Typical walking on toes with a scissors gait, crossing one foot in front of the other

Athetoid CP (due to impairment of the extrapyramidal tract)

  • Involuntary movements usually affecting arms more severely than legs, including:

    -grimacing

    >

    -wormlike writhing

    -dystonia

    -sharp jerks

  • Difficulty with speech due to involuntary facial movements

  • Increasing severity of movements during stress; decreased with relaxation and disappearing entirely during sleep

Ataxic CP (due to impairment of the extrapyramidal tract)

  • Disturbed balance

  • Incoordination (especially of arms)

  • Hypoactive reflexes

  • Nystagmus

  • Muscle weakness

  • Tremor

  • Lack of leg movement during infancy

  • Wide gait as child begins to walk

  • Sudden or fine movements impossible (due to ataxia)

Mixed CP

  • Spasticity and athetoid movements

  • Ataxic and athetoid movements (resulting in severe impairment)

Findings for children who have mixed forms of CP may include:
  • retarded growth and development
  • difficulty chewing and swallowing.
Diagnostic test results
  • Cranial ultrasound identifies structural abnormalities, hemorrhage and hypoxic-ischemic injury.
  • Computed tomography scan and magnetic resonance imaging may show congenital malformations, hemorrhage, and periventricular leukomalacia.
  • EEG may identify the source of seizure activity.
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Jun 1, 2016 | Posted by in NEUROLOGY | Comments Off on Congenital disorders

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