There are two main reasons for the separation of fetal ventricles and the widening of fetal lateral ventricles, namely, the abnormality of fetal central nervous system or other systemic systems. The specific reasons for fetal lateral ventricle widening are:
1. Abnormal fetal central nervous system: it may be caused by abnormal development of fetal midline structure or local occupation;
2. Other systemic abnormalities: intracranial manifestations of other systemic abnormalities. The pathogenic factors are chromosome abnormality and virus infection (such as cytomegalovirus infection, Toxoplasma gondii infection and syphilis infection).
Ventricular enlargement (VM) refers to the excessive accumulation of cerebrospinal fluid in the ventricular system, which leads to the enlargement of the ventricular system, among which lateral ventricular enlargement is the most common. Prenatal ultrasound examination showed that the width of fetal lateral ventricle was greater than 10mm, which was called lateral ventricle widening.
The diagnostic method of fetal lateral ventricle widening is usually ultrasound examination. Widening of lateral ventricle is one of the most easily displayed intracranial structural abnormalities by prenatal ultrasound. The standard method for prenatal ultrasound examination to judge whether the ventricle is widened and the degree of lesion is to measure the width of the lateral ventricle. The width of normal lateral ventricle is ≤ 10 mm, with an average of 7mm, which is basically unchanged between 14-40 weeks. Ultrasound scanning has high clinical value and significance in diagnosing fetal mild lateral ventricular widening.
Matters needing attention in ultrasound examination of fetal lateral ventricle widening are as follows:
1. If lateral ventricular enlargement is suspected in ultrasound screening, it should be measured and evaluated, and whether there are other structural abnormalities or genetic markers should be examined in detail;
2. It is suggested to analyze chromosome karyotype;
3. Because lateral ventricle widening is also related to intrauterine infection, it is suggested to screen TORCH virus.
4. It is suggested to do MRI (nuclear magnetic resonance) to help rule out central nervous system diseases.
Classification of fetal lateral ventricle widening The classification of fetal lateral ventricle widening is generally classified according to the location of the disease, the width of the ventricle and the pathogenic factors. According to different parts of fetal lateral ventricle widening, it can be divided into fetal left ventricle widening, fetal right ventricle widening and fetal bilateral lateral ventricle widening. Fetal lateral ventricle widening can be divided into severe lateral ventricle widening, mild lateral ventricle widening and isolated mild lateral ventricle widening.
1, severe lateral ventricular widening: refers to the excessive accumulation of cerebrospinal fluid in the ventricular system, the expansion of the lateral ventricular system, and the increase of pressure. Ultrasound examination shows that the ventricle is widened. Generally, the triangular area of lateral ventricle is widened to 1.5 cm, indicating that the ventricle is enlarged, and the wider it is, the heavier it is. If the triangle 1.2- 1.4 cm wide and choroid plexus accounts for more than 50% of the ventricle, it is generally considered normal. If the choroid plexus is reduced and suspended, it is considered that there is hydrocephalus, and the width of ventricle is ≥15 mm. Severe lateral ventricle widening can be caused by dynamic changes of cerebrospinal fluid, abnormal brain tissue structure or brain tissue destruction. Severe ventricular dilatation with abnormal cerebrospinal fluid circulation pathway and rapid progress is called hydrocephalus, which can be divided into obstructive hydrocephalus and communicating hydrocephalus.
2. Mild lateral ventricle widening: 10mm≤ lateral ventricle diameter ≤ 15mm is mild lateral ventricle widening. Lateral ventricle diameter
3. Isolated mild lateral ventricular widening: refers to cases with no other abnormal findings by prenatal systemic ultrasound, which belongs to mild lateral ventricular widening. If mild lateral ventricular widening is not accompanied by other ultrasonic structural abnormalities, it is called isolated mild lateral ventricular widening. About 10% of isolated fetuses with mild lateral ventricular widening are chromosomal abnormalities, of which 2 1 trisomy is the most common. Viral infection in pregnancy, especially cytomegalovirus infection in the third trimester of pregnancy, often leads to abnormal manifestations such as isolated lateral ventricle widening and paraventricular mixed echo.