Ventriculomegaly
Encyclopedia
Ventriculomegaly is a brain condition that occurs when the lateral ventricles
become dilated. The most common definition uses a width of the atrium of the lateral ventricle of greater than 10 mm. This occurs in around 1% of pregnancies. When this measurement is between 10 and 15 mm, the ventriculomegaly may be described as mild to moderate. When the measurement is greater than 15mm, the ventriculomegaly may be classified as more severe. Enlargement of the ventricles may occur for a number of reasons, such as loss of brain volume (perhaps due to infection
or infarction
), or impaired outflow or absorption of cerebrospinal fluid
from the ventricles. Often, however, there is no identifiable cause. The interventricular foramen may be congenitally malformed
, or may have become obstructed by infection, hemorrhage, or rarely tumor
, which may impair the drainage of cerebrospinal fluid, and thus accumulation in the ventricles. This diagnosis is generally found in routine fetal anomaly scans at 18–22 weeks gestation. It is one of the more common abnormal brain findings on prenatal ultrasound, occurring in around 1–2 per 1000 pregnancies. In many cases of mild ventriculomegaly, however, there is resolution of ventriculomegaly during the pregnancy.
, spina bifida
, and heart defects. Fetuses with both isolated ventriculomegaly and with other anomalies have an increased risk of having a chromosomal abnormality, including that of Down Syndrome
.
Many conditions associated with ventriculomegaly can be defined prior to birth, but the possibility remains of other anomalies (either structural, chromosomal or genetic) only being identified later in pregnancy or after birth. Ventriculomegaly associated with abnormal findings and other structural malformations, often has an adverse prognosis
, which ranges from disability (often mild) to death. However, in cases of mild isolated ventriculomegaly, there is around a 90% chance of a normal outcome.
Increasingly, fetal magnetic resonance imaging
is being considered as part of the assessment of pregnancies complicated by fetal ventriculomegaly, and appears to be important in the postnatal assessment of affected children.
Although evaluation of lateral ventricles dimensions is decisive for establishing a diagnosis of ventriculomegaly, but the shape of the ventricular system, including that of the frontal horns is also important.
Ventricular system
The ventricular system is a set of structures containing cerebrospinal fluid in the brain. It is continuous with the central canal of the spinal cord.-Components:The system comprises four ventricles:* right and left lateral ventricles* third ventricle...
become dilated. The most common definition uses a width of the atrium of the lateral ventricle of greater than 10 mm. This occurs in around 1% of pregnancies. When this measurement is between 10 and 15 mm, the ventriculomegaly may be described as mild to moderate. When the measurement is greater than 15mm, the ventriculomegaly may be classified as more severe. Enlargement of the ventricles may occur for a number of reasons, such as loss of brain volume (perhaps due to infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
or infarction
Infarction
In medicine, infarction refers to tissue death that is caused by a local lack of oxygen due to obstruction of the tissue's blood supply. The resulting lesion is referred to as an infarct.-Causes:...
), or impaired outflow or absorption of cerebrospinal fluid
Cerebrospinal fluid
Cerebrospinal fluid , Liquor cerebrospinalis, is a clear, colorless, bodily fluid, that occupies the subarachnoid space and the ventricular system around and inside the brain and spinal cord...
from the ventricles. Often, however, there is no identifiable cause. The interventricular foramen may be congenitally malformed
Congenital disorder
A congenital disorder, or congenital disease, is a condition existing at birth and often before birth, or that develops during the first month of life , regardless of causation...
, or may have become obstructed by infection, hemorrhage, or rarely tumor
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...
, which may impair the drainage of cerebrospinal fluid, and thus accumulation in the ventricles. This diagnosis is generally found in routine fetal anomaly scans at 18–22 weeks gestation. It is one of the more common abnormal brain findings on prenatal ultrasound, occurring in around 1–2 per 1000 pregnancies. In many cases of mild ventriculomegaly, however, there is resolution of ventriculomegaly during the pregnancy.
Associations
Ventriculomegaly is also known to be associated with other malformations such as agenesis of the corpus callosumAgenesis of the corpus callosum
Agenesis of the corpus callosum is a rare birth defect in which there is a complete or partial absence of the corpus callosum. Agenesis of the corpus callosum occurs when the corpus callosum, the band of white matter connecting the two hemispheres in the brain, fails to develop normally,...
, spina bifida
Spina bifida
Spina bifida is a developmental congenital disorder caused by the incomplete closing of the embryonic neural tube. Some vertebrae overlying the spinal cord are not fully formed and remain unfused and open. If the opening is large enough, this allows a portion of the spinal cord to protrude through...
, and heart defects. Fetuses with both isolated ventriculomegaly and with other anomalies have an increased risk of having a chromosomal abnormality, including that of Down Syndrome
Down syndrome
Down syndrome, or Down's syndrome, trisomy 21, is a chromosomal condition caused by the presence of all or part of an extra 21st chromosome. It is named after John Langdon Down, the British physician who described the syndrome in 1866. The condition was clinically described earlier in the 19th...
.
Many conditions associated with ventriculomegaly can be defined prior to birth, but the possibility remains of other anomalies (either structural, chromosomal or genetic) only being identified later in pregnancy or after birth. Ventriculomegaly associated with abnormal findings and other structural malformations, often has an adverse prognosis
Prognosis
Prognosis is a medical term to describe the likely outcome of an illness.When applied to large statistical populations, prognostic estimates can be very accurate: for example the statement "45% of patients with severe septic shock will die within 28 days" can be made with some confidence, because...
, which ranges from disability (often mild) to death. However, in cases of mild isolated ventriculomegaly, there is around a 90% chance of a normal outcome.
Increasingly, fetal magnetic resonance imaging
Magnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
is being considered as part of the assessment of pregnancies complicated by fetal ventriculomegaly, and appears to be important in the postnatal assessment of affected children.
Although evaluation of lateral ventricles dimensions is decisive for establishing a diagnosis of ventriculomegaly, but the shape of the ventricular system, including that of the frontal horns is also important.