DESCRIPTIONÂ
A baby’s brain forms during pregnancy. First, nerve cells (neurons) form in the center of the brain. Then, they move outward to their final destinations all over the brain and are organized as the brain develops. This migration is a very precise process. It requires certain chemical signals to be sent accurately. In a fully developed brain, there are:
- Two hemispheres (halves of the brain)
- Appropriately sized gyri (folds in the brain)
- Sulci (grooves in the surface of the brain)
In neuronal migration disorders, neurons do not reach their appropriate destinations. This results in an abnormal brain structure. Sometimes, the abnormality is minimal. Other times, it is more severe. Examples of NMDs include:
- Agenesis of corpus callosum. This is when the major connection between the two halves of the brain do not properly form.
- Agenesis of cranial nerves. This is when the nerves controlling face and eye movements, hearing, balance, and swallowing do not properly form.
- Focal cortical dysplasia. This is when a limited area of the brain forms abnormally.
- Lissencephaly and pachygyria. In both of these NMDs, the brain is abnormally smooth.
- Macrogyria. This is when there are larger-than-normal folds of the brain.
- Microgyria. This is when there are smaller-than-normal folds of the brain.
- Polymicrogyria. This is when there are an abnormal number of small brain folds.
- Neuronal heterotopias. In this condition, gray matter in the brain appears in the wrong places. It might appear around the ventricles, the spaces of fluid inside the brain. Or it might appear in areas of white matter.
- Porencephaly. This results in an abnormal, fluid-filled cyst in the brain.
- Schizencephaly. This results in a slit or cleft in the brain.
SIGNS AND SYMPTOMSÂ
Diagnosis
NMDs can sometimes be diagnosed on prenatal ultrasound.
Fetal magnetic resonance imaging (MRI) done in pregnancy can confirm a diagnosis. It can also provide more details on the severity and presence of other brain malformations before the baby is born.
If a diagnosis is not made during pregnancy, NMDs can be diagnosed in infancy and childhood using:
- A head ultrasound (in infants only)
- A head computed tomography scan (CT scan)
- Brain MRI
Symptoms
Common symptoms of NMDs include:
- Microcephaly. This is when the head is abnormally small.
- This is when the head is abnormally large.
- Epilepsy. Children may develop seizures. The seizures may require medications, procedures, or a specialized medical diet.
- Developmental delays. There may be delays in reaching milestones such as:
- Rolling over
- Sitting
- Standing
- Walking
- Talking
- Learning
- Using hands
- Learning disabilities. Children will need extra help at school. They may need to be enrolled in special education.
- Problems with motor control and movement. This can include:
- Difficulty controlling muscles
- Lack of movement
- Muscles that are too tight or too floppy
- Unpredictable movements
- Problems with communication. This can include trouble:
- Learning or saying words
- Understanding language
- Communicating with words, sign language, or pointing
- Problems with swallowing. Some children may not be able to swallow safely. Many will benefit from a feeding tube. The feeding tube can help them safely get nutrition and medications.
- Problems with vision and hearing. Some children may be blind and/or deaf. They may benefit from:
- Vision or hearing therapy
- Hearing aids
- Special accommodations at school
- Facial differences. Some children may not look like their parents due to abnormal face development.
- This occurs when there is too much fluid in the head. The fluid can cause high pressure in the head.
Complications
NMDs can put children at risk for potentially life-threatening complications. These complications can include:
- Lung infections
- Difficulty breathing
- Seizures that are difficult to treat
OUTLOOK
There are no cures for NMDs. Symptoms can vary significantly based upon the type of NMD and its severity.
Early and consistent therapy can be very helpful for some children. Therapies may include physical, occupational, speech, or vision therapy.
Some children will need daily medications to prevent seizures and treat other complications. Some children will also benefit from a feeding tube for extra nutrition. When hydrocephalus is present, a surgical procedure called a shunt may be needed to relieve pressure in the head.
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