What are Congenital Brain Defects?
Congenital brain defects are defined as functional or structural abnormalities of the brain that develop in the womb and are present at birth.
The brain of the fetus begins to grow shortly after conception and continues to develop throughout pregnancy. Billions of nerve cells called neurons undergo a critical and crucial development process in which they form different regions of the brain. Any interruption or disturbance in this process, specifically during the first twelve weeks of pregnancy, can result in congenital brain defects. Brain abnormalities may also occur if the skull does not form properly.
Causes of Congenital Brain Defects
A variety of environmental and genetic factors can be attributed to the development of congenital brain defects. These factors may include:
- Inherited genetic defects
- Spontaneous genetic mutations within the embryo
- Damage to the embryo due to mother's exposure to infection, toxins, drug and alcohol use, malnutrition, or trauma
Signs and Symptoms of Congenital Brain Defects
Signs and symptoms of congenital brain abnormalities vary as each abnormality has a distinct set of impairments and symptoms associated with it. In general, children born with congenital brain conditions may have:
- Cleft lip and palate
- Head pain
- Bowel and bladder issues
- Muscle weakness
- Vision impairments
- Cardiovascular issues
- Gastrointestinal problems
- Growth or developmental delays
Types of Congenital Brain Defects
Many types of congenital brain abnormalities can occur as a result of neural tube defects. During the early development of a fetus, a flat layer of tissue along the rear of the fetus curls up to form a tube. This presumed neural tube matures into the brain, and at one end, the spinal cord. Closure of the neural tube is necessary for subsequent development of the tissue within. Improper closure of this tube can result in the occurrence of several different types of brain abnormalities, including:
- Arnold-Chiari or Chiari II: A section of the cerebellum, a part of the brain that influences motor control, is moved downward into the top section of the spinal column. This causes the spinal cord or brain to become compressed.
- Encephalocele: A section of the brain swells out through an opening in the skull. The swelling is often noted along the front-to-back midline at the rear of the skull.
- Anencephaly: The head end of the neural tube fails to close, and a significant section of the brain and skull is missing. The missing section of the skull means that the brain tissue is exposed.
Other types of congenital brain abnormalities occur within the structure of the brain. These include:
- Microcephaly: An abnormality in which the baby's head appears significantly smaller than expected, often as a result of abnormal brain development.
- Megalencephaly: Also called macrencephaly, this is a condition in which a baby’s brain is abnormally heavy, large, and usually malfunctioning.
- Holoprosencephaly: This is an embryonic brain development abnormality in which the brain does not divide properly into left and right hemispheres. The disorder can also hamper the development of the face and head.
- Hydrocephalus: A condition characterized by excessive accumulation of cerebrospinal fluid (CSF) in and around the brain, which causes swelling of the brain and affects its normal functioning.
- Dandy-Walker syndrome: An abnormal brain malformation condition that occurs during embryonic development and is characterized by enlargement of the base of the skull, cystic enlargement of the fourth ventricle, and underdevelopment of the central portion of the cerebellum.
Diagnosis of Congenital Brain Defects
Your physician may be able to diagnose congenital brain abnormalities either from direct physical examination or imaging studies including magnetic resonance imaging (MRI) and computed tomography (CT) scans. Electroencephalography (EEG) may be utilized to detect characteristic defects.
Prenatal diagnosis of neural tube defects causing meningomyelocele or anencephaly is possible through maternal blood testing for alpha-fetoprotein, which is almost always elevated, and ultrasound examination. Ultrasound can also be utilized to diagnose Chiari II malformations and Dandy-Walker malformation. Amniocentesis may be used to detect trisomies or other chromosomal abnormalities.
Treatment for Congenital Brain Defects
Treatment for congenital brain defects varies and depends upon the severity and type of condition. Many treatments in general concentrate on treating the symptoms. For instance, medications may be utilized to treat symptoms of brain defects, such as episodes of seizures and spasticity or muscle rigidity.
Some congenital brain defects are addressed with surgery. For instance, decompression surgery is employed to create more space for cerebrospinal fluid and brain tissue where necessary to treat conditions such as Chiari malformation. Surgery to correct a defective skull can also provide the brain with adequate space for normal growth and development and address specific brain conditions. Insertion of shunts is another option to drain the accumulated cerebrospinal fluid in and around the brain with malformations associated with hydrocephalus (Chiari II, Dandy-Walker, and some cases of hydranencephaly).