# Birth Disorders of the Brain and Spinal Cord

## What are birth disorders of the brain and spinal cord?

Birth disorders of the brain and spinal cord generally occur during pregnancy and are often present at birth. They are rare and are caused by problems that happen during the development of the brain and spinal cord.

Some of these problems occur very early in pregnancy as the brain begins to develop. For example, neural tube defects occur when the neural tube does not form properly. The neural tube forms from a special set of cells; the top of the tube becomes the brain, and the remainder becomes the spinal cord and the structures around it. The neural tube typically folds and closes between the third and fourth weeks of pregnancy to form the brain and spinal cord of the embryo. Spina bifida is one of the more common neural tube disorders.

Other brain and spinal cord development issues arise during neuronal migration, the process of brain cells traveling from their place of origin to the place they will remain. When neuronal migration is disrupted, birth defects happen in the brain. The information below describes some of the disorders that can arise when the brain and spinal cord do not develop normally during pregnancy.

## Types of birth disorders of the brain and spinal cord

### Agenesis of the Corpus Callosum

Agenesis of the corpus callosum (ACC) is a brain disorder in which the main structure (known as the corpus callosum) that connects the left and right sides of the brain is partially or completely missing. It is caused by a disruption of brain cell migration during development.  ACC can occur as an isolated condition or in combination with other brain conditions, including Chiari malformations, Dandy-Walker syndrome, schizencephaly, and holoprosencephaly. The effects of ACC range from mild to severe, depending on whether other brain conditions are present. Other disorders of the corpus callosum include dysgenesis, in which the corpus callosum develops in a malformed or incomplete way, and hypoplasia, in which the corpus callosum is thinner than usual. Women and girls may have a gender-specific condition called Aicardi syndrome.

### Aicardi syndrome

Aicardi syndrome is a rare, genetic neurological disorder in which all or part of the corpus callosum is missing. This disorder primarily affects newborn girls. Symptoms may include infantile spasms (a type of epilepsy), eye lesions, low muscle tone, microcephaly (unusually small head), increased muscle tone or stiffness (spasticity), intellectual problems and developmental delays, heterotopias (groups of brain cells that migrated to the wrong areas of the brain during development), numerous small (or too few) brain folds, and brain cysts. People with Aicardi syndrome also may have  skeletal issues, skin problems, facial asymmetry (in which one side of the face doesn’t exactly mirror the other side), small hands, and an increased occurrence of tumors.

### Anencephaly

Anencephaly is rare neurological disorder that involves a defect in the closure of the neural tube during fetal development. Infants with this disorder are born without a forebrain (the front part of the brain). The remaining brain tissue is often not covered by bone or skin.

### Colpocephaly

Colpocephaly is a congenital brain disorder in which the occipital horns—located in the rear portion of the brain—are larger than normal. This happens because white matter in the posterior cerebrum has failed to develop or thicken.. Other features may include movement problems, muscle spasms, and seizures.

### Craniosynostosis

The skull is made up of bony plates that allow the brain to grow while it develops. The skull plates are joined together by seams (called sutures), which allow for growth of the skull. Craniosynostosis is a developmental condition that occurs when the sutures in a developing baby’s skull plates join together  too early. This can be caused by a genetic issue, metabolic disease, or an overactive thyroid. Surgery can help relieve pressure on the brain and nerves and reshape the skull. Some children can use a helmet. The prognosis for development depends on the underlying condition, if there is one.

### Dandy-Walker syndrome

Dandy-Walker syndrome is a brain disorder caused by an unusual formation between the cerebellum and the fluid-filled spaces around it. The cerebellum is in the back of the brain and controls movement. Dandy-Walker syndrome is sometimes associated with an absence of the corpus callosum. Symptoms may include slow development of motor skills (the ability to control movements) and progressive growth of the skull in babies. In older children, symptoms can include pressure in the skull, irritability, throwing up, problems with balance or muscle control, and unusual eye movements. Dandy-Walker syndrome can be associated with unusual development of the head, heart, face, arms, or legs, although some children may never have symptoms.

### Encephalocele

Encephalocele is a rare neural tube disorder characterized by a sac-like protrusion of the brain and the membranes that cover the brain through an opening in the skull. The disorder is caused by failure of the neural tube to close completely as the fetus develops. The result is a groove down the middle of the skull, in the area between the forehead and nose, or at the back of the skull. The disorder is usually diagnosed immediately after birth and is often accompanied by abnormalities of the brain and face or other brain malformations.

### Holoprosencephaly

Holoprosencephaly occurs when a developing baby’s brain does not sufficiently divide into left and right halves (known as hemispheres). The result is a single brain structure and significant skull and facial differences. In most cases, the malformations are so severe that babies die before birth. In less severe cases, babies are born with normal or near-normal brain development, but may have facial differences that affect the eyes, nose, and upper lip.

### Iniencephaly

Iniencephaly is a rare birth disorder caused by improper closure of the neural tube as the fetus develops. The disorder results in extreme backward bending of the head combined with severe distortion of the spine. Most infants have additional birth defects, such as anencephaly, cephalocele (in which part of the cranial contents protrudes from the skull), and cyclopia (in which the two cavities of the eyes fuse into one). Additional birth disorders related to iniencephaly may include the lack of a lower jawbone or a cleft lip and palate. Other parts of the body may be affected, and infants can have cardiovascular disorders, diaphragmatic hernias, and gastrointestinal malformations.

### Lissencephaly

Lissencephaly, also known as agyria, is a condition in which the cerebral cortex develops without folds (convolutions) and the head is extremely small. It is a rare, gene-linked brain disorder. Children with lissencephaly usually have head sizes in the expected range at birth, but the head and brain do not grow at normal rates. Lissencephaly is caused by neuronal migration problems. In pachygyria, also called incomplete lissencephaly, there are few folds, and they are usually broad and flat. Lissencephaly may be associated with isolated lissencephaly sequence, Miller-Dieker syndrome, and Walker-Warburg syndrome.

### Megalencephaly

Megalencephaly (also known as macrencephaly) is a condition in which an infant or child has a large, heavy, and potentially malfunctioning brain. The condition affects boys more often than girls. Unilateral megalencephaly or hemimegalencephaly is a rare condition in which one side of the brain is enlarged. Children with this disorder may have a large, asymmetrical head and experience epilepsy, partial paralysis, and impaired cognitive development.

### Microcephaly

Microcephaly is a medical condition in which the head is small because the brain has not fully developed or has stopped growing. Microcephaly can be present at birth or it may develop in the first few years of life. Microcephaly is associated with Down syndrome, chromosomal syndromes, congenital infections, and neurometabolic syndromes.

### Polymicrogyria

Polymicrogyria, also known as micropolygyria or microgyria, is a developmental disorder of the brain in which the ridges or folds, called gyri, on the surface of the brain do not develop normally. In people with polymicrogyria, the brain develops too many folds, and the folds are unusually small. Polymicrogyria can affect part of the brain or the whole brain. Symptoms of polymicrogyria depend on how much of the brain and which areas of the brain are affected.

### Porencephaly

Porencephaly is an extremely rare disorder of the central nervous system that causes a cyst or cavity filled with cerebrospinal fluid to develop in the brain. It is usually the result of damage from stroke or infection after birth, but it can also be caused by delayed development before birth (which is inherited and less common). Hydranencephaly is an extreme form of porencephaly in which the brain’s hemispheres are absent and replaced by sacs filled with cerebrospinal fluid. Symptoms may include epilepsy, vision problems, lack of growth, deafness, paralysis, and intellectual problems.

### Schizencephaly

Schizencephaly is an extremely rare birth disorder in which there are abnormal slits, or clefts, in the left and right hemispheres of the brain. Babies with clefts in both hemispheres commonly have developmental delays, delays in speech and language skills, and problems with brain-spinal cord communication. Children with clefts in only one hemisphere (unilateral clefts) are often paralyzed on one side of the body but may have average to near-average intelligence. Individuals with schizencephaly also may have an abnormally small head, cognitive problems, partial or complete paralysis, and poor muscle tone. Most will have epilepsy. Some individuals may have an excessive accumulation of fluid in the brain called hydrocephalus.

## How can I or my loved one help improve care for people with birth disorders of the brain and spinal cord?

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Many of these disorders are considered rare, which often means not much is known about them. This is usually the case because doctors and researchers do not see many people with these disorders, which makes it hard to learn from them through observations or large studies. This makes it even more important to participate in research on these conditions.

Consider participating in a clinical trial so clinicians and scientists can learn more about birth disorders of the brain and spinal cord. In the case of conditions surrounding birth defects, participation in genetic research by the individual’s siblings and other family members can be particularly valuable. Clinical research with study participants to help researchers learn more about a disorder and perhaps find better ways to safely detect, treat, or prevent disease.

All types of participants are needed—those who are healthy or may have an illness or disease—of all different ages, sexes, races, and ethnicities to ensure that study results apply to as many people as possible, and that treatments will be safe and effective for everyone who will use them.

For information about participating in clinical research visit NIH Clinical Research Trials and You. Learn about clinical trials currently looking for people with birth disorders of the brain and spinal cord at Clinicaltrials.gov.
> Where can I find more information about birth disorders of the brain and spinal cord?
The following organizations and resources may provide additional information: 

Birth Defect Research for Children, Inc.Phone: 407-895-0802

Genetic and Rare Diseases (GARD) Information Center

Magic FoundationPhone: 800- 362-4423 

March of DimesPhone: 888-663-4637

MedlinePlus

National Organization for Rare Disorders (NORD)Phone: 203-744-0100 or 800-999-6673; 844-259-7178 Spanish

PMG Awareness Organization

PubMed

The Arc of the United StatesPhone: 202-534-3700 or 800-433-5255

The Carter Centers for Brain Research in Holoprosencephaly and Related Brain MalformationsPhone: 214-559-8411

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