Congenital Diseases and Disorders

April 11, 2024

Congenital Diseases and Disorders

Learning Objective: Examine congenital diseases and disorders that impact the nervous system, including the signs, symptoms, etiology, diagnostic procedures, and treatments.

Congenital diseases and disorders include a wide range of structural and functional abnormalities present at birth. Many congenital diseases and disorders impact the nervous system. The following sections examine common congenital diseases and disorders that involve the nervous system.

Fetal Alcohol Spectrum Disorders

Learning Objective: Examine congenital diseases and disorders that impact the nervous system, including the signs, symptoms, etiology, diagnostic procedures, and treatments.

Fetal alcohol spectrum disorders (FASDs) are a group of conditions that occur in a person whose mother drank alcohol during the pregnancy. The physical and mental deficiencies will last for life. The disorders include the following:

• Fetal alcohol syndrome (FAS), which is at the farthest end of the spectrum, is the most complex disorder. People can experience the signs and symptoms indicated in the following section. People with FAS have a difficult time with school and getting along with others.
• Alcohol-related neurodevelopmental disorder (ARND), which affects learning and behavior.
• Alcohol-related birth defects (ARBD), which cause problems with the heart, kidneys, bones, and hearing.

These disorders are caused by alcohol consumption by the mother during the pregnancy. The alcohol in the mother’s bloodstream crosses the placenta. Alcohol can interfere with oxygen and nutrient delivery in the growing baby. It can also harm the development of tissues and organs. The signs and symptoms depend on the amount of alcohol consumed during the pregnancy and the time during the pregnancy it was consumed. Here are the common signs and symptoms:

• Poor memory, hyperactive behavior, difficulty with attention and math concepts
• Speech and language delays, learning and intellectual disabilities
• Poor reasoning and judgment skills
• Vision or hearing problems
• Babies may experience low body weight, sleeping and sucking problems
• Poor coordination, small head size, shorter-than-average height, abnormal facial features (e.g., smooth ridge between the nose and upper lip)
• Heart, kidney, or bone problems

Knowing at delivery that the mother drank alcohol during the pregnancy can help with early diagnosis. At birth, a thorough assessment will be done. The provider will assess for issues during childhood. The child will be screened for cognitive, learning, and language development delays. Health issues, along with social and behavioral problems, will also be monitored. There is no cure for FASDs. Early intervention can help reduce some of the effects. Not drinking alcohol during pregnancy is the only way to prevent FASDs.

Spina Bifida

Learning Objective: Discuss spina bifida, including the signs, symptoms, etiology, diagnostic procedures, and treatments.

Spina bifida is a neural tube defect that occurs when the spinal column does not close during the first month of pregnancy. Spina bifida can cause damage to the nerves and spinal cord. Pregnant females are encouraged to take folic acid during pregnancy to reduce the risk of spina bifida. The cause is unknown. There are four types of spina bifida:

• Spina bifida occulta: Mildest form; no spinal nerves are involved, but one or more vertebrae are malformed. No signs or symptoms may be present. The only indication may be an abnormal cluster of hair, a small dimple, or birthmark on the infant’s back (FIGURE 22.11).
• Closed neural tube defect: Includes a malformation of the fat, bone, or meninges associated with the spinal cord. Symptoms range from no symptoms to incomplete paralysis with bowel and urinary dysfunction.

FIGURE 22.11 Types of spina bifida.

• Meningocele: The meninges protrude through an abnormal vertebral opening, creating a sac. The sac is filled with fluid. Symptoms range from no symptoms to complete paralysis with bowel and bladder dysfunction.
• Myelomeningocele: The most serious type because the spinal canal is open along several vertebrae. A sac containing fluid, part of the spinal cord, and nerves comes through the opening in the infant’s back. This type can cause partial or complete paralysis below the opening. The child may have weakness or paralysis of the legs, bowel and bladder incontinence, lack of feeling in the legs, and an increase in cerebrospinal fluid.

During pregnancy, the mother can take a maternal serum alpha-fetoprotein (MSAFP) test (also known as the Triple Test and Quad Screen). If abnormally high amounts of alpha-fetoprotein (AFP) are found, it suggests that the baby has a neural tube defect (e.g., spina bifida). The accuracy of the MSAFP test is not perfect. Even though abnormally high levels of AFP are found, the baby may be normal. With negative test results, there is still a small risk of spina bifida. Amniocentesis can also be done if the MSAFP test result comes back abnormal. Most of the time, ultrasound can detect the two most severe types of spina bifida during pregnancy.
Prenatal surgery for spina bifida can occur around 26 weeks of pregnancy. The child may have fewer disabilities if the spinal cord is repaired at that time. Surgery can also occur after birth. Additional treatments focus on the complications that occur, including leg weakness, bowel or bladder problems, and hydrocephalus (FIGURE 22.12).

Shunt System

Hydrocephalus can be treated with a surgical placement of a shunt system. The shunt system drains the extra cerebrospinal fluid (CSF) from the ventricles in the brain into another part of the body (e.g., abdomen), where it is absorbed into the bloodstream. The ventriculoperitoneal shunt is one of the more common shunts (FIGURE 22.13).
The shunt system consists of the following parts:

• An inflow catheter (a tube) with a pressure-sensitive valve. When the pressure reaches a certain level, the valve opens, allowing CSF to drain into the catheter.
• A valve mechanism that regulates the pressure levels. Usually, this device is implanted under the skin on the top of the head or behind the ear.
• An outflow catheter, which drains the CSF into another part of the body.

A shunt system needs to be replaced as the person ages or when it gets blocked. Increased intracranial pressure (ICP) is a sign that the shunt system is not functioning correctly. A person may experience a headache, nausea and vomiting, confusion, double vision, and decreased mental abilities with ICP.

Other Congenital Diseases and Disorders

Learning Objective: Describe other congenital diseases and disorders of the nervous system.

The following are additional structural diseases and disorders.

• Anencephaly: The infant is born without parts of the brain. The remaining part of the brain may not be covered by the cranium or skin.
• Cerebral palsy (CP): A group of nonprogressive disorders caused by abnormal brain development or brain injury, resulting in muscle weakness or problems with using the muscles. CP can affect people’s ability to move and maintain their posture and balance. Signs and symptoms usually appear during infancy or the preschool years. The child can have abnormal reflexes, floppiness or rigidity of the extremities, abnormal posture, involuntary movements, and an unsteady gait (manner or style of walking). CP is classified by the main type of movement disorder involved: spasticity (stiff muscles), dyskinesia (uncontrollable movements), and ataxia.
• Down syndrome (also called trisomy 21): The most common chromosomal condition in the United States. It is a condition in which a person is born with an extra copy of chromosome 21. The complications from Down syndrome range in severity and can include intellectual disabilities, dementia, heart disease, hearing, and visual issues, thyroid disease, and musculoskeletal complications (e.g., poor muscle tone).
• Encephalocele: A saclike protrusion of the brain and the meninges. Results when the neural tube does not completely close during pregnancy, and the protrusion commonly occurs at the back and top of the head or between the forehead and nose (FIGURE 22.14).
• Microcephaly: A small head size compared to the rest of the body. Often reflects poor brain development and is usually associated with cognitive impairments.
• Tuberous sclerosis: A rare genetic disease that causes benign tumors to grow in major organs (e.g., heart, brain, liver, and skin). Symptoms depend on the location of the tumors and may include seizures, intellectual disabilities, and kidney problems.