Fetal Dandy-Walker syndrome

　　DWS is often accompanied by various intracranial and extracranial developmental abnormalities, which come from different periods of pregnancy and different germ layers. Therefore, it is difficult to propose a consistent hypothesis about the embryonic development of this syndrome. As for its abnormal development in the later stage of embryogenesis, it may be related to intrauterine rubella virus, cytomegalovirus, or toxoplasmosis infection, medication (warfarin), and alcohol consumption.

　　But also found cases with chromosomal abnormalities, among which trisomy 18, 21, and 12 are most common, and this abnormal chromosome also exists in the father of the child, and there are cases where siblings both have DWS, which concerns genetic factors. In addition, this congenital malformation can be associated with tumors, reflecting the existence of gene mutations. Some studies have used animal simulation experiments, injecting 6-aminonicotinamide into the abdominal cavity of mice, which can induce DWS to show that the disease may also be caused by a systemic metabolic defect.

　　At the fifth week of normal embryonic development, the anterior membrane area of the rhombencephalon merges with the cerebellum, and the posterior membrane area forms the foramen of Magendie. DWS is a comprehensive developmental malformation of the rhombencephalon before the 6th to 7th week of pregnancy. If the oblique lip on the top of the rhombencephalon cannot completely differentiate, the neural cells from the oblique lips of the two wings cannot undergo normal proliferation and migration, affecting the fusion of the two wings, resulting in underdevelopment of the cerebellar vermis and ectopic inferior olive nucleus. If the posterior brain area only protrudes outward without rupture to form the middle and lateral foramina of the fourth ventricle, the result is a cystic malformation of the posterior fossa.

　　In 1982, French summarized four viewpoints on the etiology of the disease: 1. Occlusion of the foramen of Magendie during embryonic stage; 2. Poor fusion of the cerebellar vermis during embryonic stage; 3. Incomplete closure of the neural tube during embryonic stage; 4. Changes in cerebrospinal fluid dynamics.

　　More than 50% of children with Dandy-Walker malformation have other brain malformations, including abnormal gyrus structure, ectopic brain tissue, maldevelopment of midline structures (such as corpus callosum, anterior commissure, cingulate gyrus, inferior olive, choroid plexus, and underdeveloped cerebral aqueduct), and interhemispheric fissure cysts. There are also midline congenital tumors and lipomas, teratomas, and so on. The most common is maldevelopment of the corpus callosum (7.5-7%). They can also be accompanied by other systemic malformations. More than 25% have skeletal malformations, including polydactyly, syndactyly, cranioschisis, Klippel-Feil syndrome, and so on. Facial hemangiomas account for 10%. Cardiovascular malformations include atrioventricular septal defects, patent ductus arteriosus, vascular malformations, aortic stenosis, and dextrocardia, and so on.

　　Dandy-Walker malformation often appears within the first 6 months of life with hydrocephalus and increased intracranial pressure, and can also be accompanied by cerebellar ataxia and cranial nerve palsy. Posterior fossa obstruction is more common in posterior fossa tumors, presenting with progressive increased intracranial pressure, cerebellar ataxia, and symptoms of cranial nerve damage. CT can show symmetrical expansion of the ventricular system above the fourth ventricle, brain edema, and signs of posterior fossa occupancy.

　　Symptoms of increased intracranial pressure include: headache, vomiting, and paralysis of the abducens nerve.

　　Hydrocephalus symptoms include: increased head size, prominent at the occipital area, cranial suture separation, enlarged and prominent anterior fontanelle, sunset sign, secondary optic atrophy, and decreased vision.

　　3. Brain signs: unsteady gait, ataxia, horizontal nystagmus, but 50% of the cerebellar function is normal.

　　4. Delayed motor development.

　　5. Mental retardation.

　　6. Seizure.

　　7. Bleeding within the cyst, caused by reasons such as maternal delivery or the child's head injury, etc., leading to the rupture of the vascular wall of the cyst wall, bleeding and hematoma within the cyst, and then blocking the outlet of the fourth ventricle, resulting in symptoms.

　　8. Serosanguinous distension within the cyst is extremely rare.

　　In the prevention of fetal Dandy-Walker syndrome, attention should be paid to the first three months of pregnancy. If the early pregnancy reaction is severe, more rest should be taken, but if the reaction is not obvious, it is best not to lie down frequently. Avoid contact with those chemicals and physical factors that can cause teratogenicity.

　　The examinations that need to be done for fetal Dandy-Walker syndrome include ultrasound examination, CT routine scan, and iodine CT ventriculography and cisternography, etc.

　　1.Ultrasound examination

　　Prenatal intracranial ultrasound can show that the fetus with the disease has a cystic dark area communicating with the fourth ventricle in the posterior fossa and an incomplete cerebellar vermis, 53% of which have hydrocephalus, and 60% have extracranial malformations (such as heart, urinary system, gastrointestinal tract) and polyhydramnios. Therefore, prenatal ultrasound examination should include defects above the tentorium and extracranial defects, as well as chromosomes. Those with other structural and chromosomal abnormalities are very unfavorable for survival. Generally, it can be diagnosed by ultrasound around 20 weeks of pregnancy. Ultrasound examination within one month after birth is convenient and easy to perform and is often the first diagnostic examination.

　　2.CT and magnetic resonance imaging (MRI) examination

　　3. CT routine scan

　　Including the bottom of the posterior fossa and the area around the occipital bone, in addition to the sagittal midline reconstruction, it can also be used to make a clear diagnosis. However, the sagittal midline section of magnetic resonance imaging is clearer.

　　4.Iodine CT ventriculography and cisternography

　　This examination is indispensable. Due to the variation of DWS, it is necessary to understand the changes in cerebrospinal fluid dynamics before surgery. Through this examination, it can be clarified: 1. Whether hydrocephalus exists; 2. Whether the cerebral aqueduct is occluded (complete or partial); 3. Whether the posterior fossa cyst communicates with the subarachnoid cavity (complete or partial), so that effective treatment methods can be selected.

　　1, Fish  The fat in fish contains omega-3 fatty acids, which are helpful for brain health. Eating fish also helps to strengthen the activity of nerve cells, thereby improving learning and memory abilities.

　　2, Whole wheat products and brown rice  Brown rice contains a variety of vitamins (especially vitamin B1), which is crucial for improving the cognitive ability of children with incomplete brain development.

　　3, Eggs  The protein contained in eggs is one of the most excellent proteins in natural foods, and the yolk, in addition to being rich in lecithin, also contains abundant calcium, phosphorus, iron, and vitamins A, D, B, etc., which is beneficial to the brain development of children with incomplete brain development.

　　Shunting

　　1. Cyst Peritoneal Shunting (c-p) and Ventriculoamniotic Shunting

　　If there is no obstruction in the midbrain aqueduct, and the posterior cranial fossa cyst and subarachnoid cavity are communicating, surgery is not required unless the drainage tube is partially obstructed (semipermeable or valve-like). However, some advocates perform cyst peritoneal shunting within one month of birth, regardless of whether hydrocephalus is present, as long as the aqueduct is unobstructed. Fetal surgeons are even more advanced, performing ventriculoamniotic shunting under ultrasound guidance at 30 weeks of gestation. The purpose of these two methods is to reduce the size of the cyst, promote the development of the cerebellar hemispheres, make the meningocele disappear, and heal the bone defects. However, the cerebellar vermis is still absent, and it is generally not possible to improve the symptoms of patients with existing cerebellar functional deficiency.

　　2. Lateral Ventricle Peritoneal Shunting (v-p)

　　If the aqueduct is blocked, but the fourth ventricle and subarachnoid cavity are still communicating, then only lateral ventricle peritoneal shunting is required. Especially, in patients with congenital heart disease, atrial shunting (v-A) should be avoided, and air embolism should be prevented.

　　3. Double Shunting

　　When the aqueduct is open, but the fourth ventricle and subarachnoid cavity are not communicating, V-P or C-P can be used alone (depending on the surgeon's habits). However, once secondary aqueduct obstruction occurs, C-P or V-P, that is, double shunting, is required.

　　4. Simultaneous V-P and C-P

　　When the aqueduct is blocked, the fourth ventricle and subarachnoid cavity are also blocked, forming two isolated dead spaces, then V-P and C-P need to be performed simultaneously, using a Y-shaped connector to divert the fluid in the two dead spaces into the peritoneal cavity. At this time, if only V-P is performed, it may sometimes cause a cerebellar tentorial hernia above the tentorium, and if only C-P is performed, the intracranial pressure above the tentorium will gradually increase.

　　5. Trigone Ventriculostomy

　　When the shunting fails, the ventricles are very large, and there is no CSF reabsorption obstruction, then stereotactic percutaneous trigone ventriculostomy can be performed.

　　6. Lumbar Cistern Peritoneal Shunting

　　If the resection of the posterior fossa cyst does not solve the problem, and the CSF dynamics examination is unobstructed at this time, then lumbar cistern peritoneal shunting can also be adopted.