Dandy-Walker syndrome is a congenital pathology of the nervous system, which is characterized by a triad of signs: hydrocephalus, hypoplasia or aplasia of the cerebellum, cysts of the posterior cranial fossa. The disease has a polyethological nature, among the provoking factors are genetic anomalies, teratogenic effects. Clinical symptoms include classic signs of hydrocephalus, various neurological disorders. Diagnosis of the defect requires neurosonography, MRI, echocardiography, and prenatal diagnosis with ultrasound screening is also possible. Treatment consists in conservative and surgical methods of correction of hydrocephalus.
Q03.1 Atresia of the holes of Mazhandi and Lushka
CNS defects occupy the second place in the group of congenital diseases, second only to cardiovascular anomalies. Up to 80% of all pathologies are accompanied by hydrocephalus, as in Dandy-Walker syndrome. This disease was described by the American neurosurgeon V. Dandy in 1914, 28 years later, Canadian-American neurosurgeon A. Walker and colleagues proposed an operative method for the treatment of the defect. Pathology occurs with a frequency of 1:25000-1:35000, girls get sick more often. Among infants with congenital hydrocephalus, pathology is registered in 3.5-12% of cases.
The etiological factors of Dandy-Walker syndrome have not yet been precisely clarified. According to modern data, pathology has a multifactorial nature, its development is promoted by both internal causes (chromosomal and gene mutations) and the effects of exogenous teratogens. Provoking factors of the disease can be:
- viral infections (cytomegalovirus, rubella);
- gestational diabetes;
- alcohol consumption by the mother during pregnancy.
The latest research shows a clear connection of the isolated form of the Dandy-Walker anomaly with mutations of the ZIC1 and ZIC4 genes. The risk of developing the disease increases in infants with congenital metabolic disorders. Most often, the syndrome is associated with one of the forms of 3-methylglutacone aciduria, which is manifested by retinopathy, renal dysfunction, metabolic acidosis and increased activity of liver enzymes.
There are three main hypotheses of structural brain lesions in Dandy-Walker disease. According to the first of them, CNS defects are caused by a slowdown in embryonic development at an early stage during the laying of the rhomboid brain. This situation is observed under the influence of teratogenic factors or against the background of genetic mutations. The second hypothesis indicates an overgrowth of the outlet of the 4th ventricle of the brain and the later opening of the Majandi aperture.
New experimental data confirm the probability of the third hypothesis: typical anatomical changes develop when a vascular plexus occurs on the thin roof of the rhomboid brain. Pathology is accompanied by intrauterine hydrocephalus, causes serious neurological disorders. Against this background, a large cyst develops in the posterior parts of the skull, which prevents the formation of the corpus callosum and the cerebellar worm.
Experts distinguish open and closed forms of the syndrome. In the first case, occlusion of the Lyushka and Mazhandi openings is observed, which is accompanied by serious violations of cerebrospinal fluid dynamics. The second option does not have such pathologies, therefore it proceeds in a more favorable form. In neurosurgery, the anatomical classification of the defect is important, according to which 2 forms of Dandy-Walker syndrome are distinguished:
- Full. It is characterized by the absence of a cerebellar worm, the presence of a connection between the cavity of the fourth ventricle and the cerebellar-cerebral cistern.
- Incomplete. It is manifested by partial underdevelopment of the cerebellar worm in its lower part, due to which communication with the large cistern is not realized throughout.
In 1989, the American pediatrician and neuroradiologist James Barkovich proposed an alternative classification based on the results of MR diagnostics. A group of diseases called the “Dandy-Walker complex” has been identified, which includes 4 clinical forms: classic anomaly (full form), Dandy Walker variant (less gross violations), Blake’s pocket cyst and mega cisterna magna.
The main manifestation of the Dandy-Walker syndrome is hydrocephalus, which occurs in the first months of a child’s life. The severity of symptoms depends on the variant of the syndrome, the rate of progression of disorders, the general condition of the newborn. Early signs include restless behavior, monotonous screaming, eating disorders and frequent regurgitation. Externally, there is a swelling of the fontanelles, expansion of the cranial sutures, a rapid increase in the circumference of the head.
A characteristic sign of hydrocephalus in Dandy-Walker syndrome is a symptom of the setting sun: when looking down, the iris is partially hidden by the lower eyelid, a white strip of sclera appears above it. Neurological symptoms are also represented by nystagmus, exophthalmos, strabismus. Convulsive syndrome, paresis and paralysis of the extremities are often noted in newborns. With the progression of the disease, a lag in psychomotor development is characteristic.
In 65-68% of cases, Dandy-Walker syndrome is accompanied by other structural neurological abnormalities. Most often, agenesis of the corpus callosum, stenosis of the Sylvian aqueduct, heterotopia of the convolutions of the cerebellar cortex are diagnosed. In severe forms of the disease, underdevelopment of the brain stem is determined, which is associated with a deep depression of vital functions and a high risk of infant mortality.
Up to 55% of children have concomitant congenital syndromes: Walker-Warburg, PHACE, Ritscher-Schinzel. Various forms of chromosomal aberrations are characteristic: deletions, duplications, trisomies and triploidies. The lesion of the cardiovascular system is manifested by septal defects and disorders of postnatal hemodynamics. Ophthalmological defects are less often detected: retinal dysplasia, microphthalmia.
The initial examination of a child with neurological disorders is carried out by a pediatrician or a neonatologist. In case of hydrocephalus and suspected Dandy-Walker syndrome, a pediatric neurologist, a neurosurgeon is connected to the diagnosis. Physical examination reveals nonspecific signs of intracranial hypertension, motor development disorders, concomitant anomalies. To make a final diagnosis , the following is carried out:
- Neurosonography. An ultrasound scan of the brain determines a large cystic formation in the back of the skull. On ultrasound, the cerebellar worm is not visualized, the underdeveloped hemispheres of the cerebellum are spread apart, the ventricular system of the brain is expanded and deformed.
- Brain MRI. Magnetic resonance imaging in sagittal and axillary projections demonstrates the expansion of the fourth ventricle, gross violations of the development of the cerebellum, and other structural anomalies.
- Echocardiography. Ultrasound of the heart is recommended for all children with Dandy-Walker syndrome, as it is often associated with congenital cardiac pathology. According to the results of EchoCG, it is possible to determine anomalies in the development of the valvular apparatus, defects of the intracardiac septum, pathologies of the location of large vessels.
- Karyotyping. In case of combined congenital malformations, it is necessary to consult a geneticist and a thorough study of the child’s genetic material. The in-depth study is aimed at diagnosing chromosomal aberrations.
- Prenatal diagnosis. During fetal ultrasound, it is possible to assume an anomaly at 15-16 weeks, a clearer visualization of the structures of the IV ventricle is possible after 22 weeks of gestation. When pathology is combined with facial clefts, echosonography may not be informative enough.
When making a diagnosis, it is necessary to differentiate the syndrome with cerebellar hypoplasia of a different etiology, retrocerebral cysts and extensions of the large cerebral cistern. A pathognomonic sign of the Dandy-Walker syndrome is a defect of the cerebellar worm, which does not occur with other variants of CNS defects. Differential diagnosis with arachnoid cysts is carried out, which requires additional instrumental research methods.
The greatest danger to the life and health of an infant is hydrocephalus, for the correction of which treatment in the intensive care unit is indicated. Massive dehydration therapy is prescribed, which includes different types of diuretics, hypertensive infusion solutions. The efforts of doctors are aimed at reducing liquor production and normalizing intracranial pressure in order to prevent brain edema and compression of cerebral structures.
With the ineffectiveness of conservative methods and the steady progression of hydrocephalus, the help of pediatric neurosurgeons is required. The main method of correction for Dandy-Walker syndrome is bypass surgery with implantation of drainage tubes or valve controlled systems. There are several types of bypass surgery: ventriculo-peritoneal, ventriculo-atrial, ventriculocysternostomy.
To correct occlusion of the cerebrospinal tract, methods of endoscopic ventriculostomy are used, which restore the normal outflow of cerebrospinal fluid, eliminate acute neurological symptoms. In hypertensive-hydrocephalic crisis, a ventricular discharge puncture is indicated, which refers to emergency temporary drainage options.
Prognosis and prevention
The outcome of the disease depends on the depth of the central nervous system lesion, the rate of increase of hydrocephalus, the presence of a combined pathology. Increasing hypertension and gross neurological defects in 90% of cases cause the death of the patient in the first years of life, for surviving children with an incomplete version of the anomaly, the prognosis is more favorable. Due to insufficient knowledge of the etiopathogenesis of the disease, effective preventive measures have not yet been developed.