Dandy Walker
From Holoprosencephaly
What is Dandy-Walker Syndrome?
Dandy-walker syndrome is a congenital malformation involving cerebellum and the cavity in the brain called fourth ventricle. The disease is characterized by the abnormal widening of fourth ventricle, one of the cavities which Central Nervous system fluid (liqour cerebri) takes place and congenital agenezis of vermis (mid-portion of both cerebellar hemispheres). And Consequently a cystic dilatation of fourth ventricle towards the posterior cranial fossa occurs.In addition a clinical situation known as hydrocephalus (increased CNS-fluid and abnormal enlargement of head cicumference) may be present.
It has been proposed that disease is due to generalized dysembriogenesis involving fourth ventricle's upper wall.(during foetal development in pregnancy).Cerebellar hemispheres are also hypoplastic and placed towards cerebral margins. Hydrocephalus occurs in 70 percent of patients because of congenitally obstructed Luschka and Magendie foramens which provide CNS-fluid drainage in normal humans. That obstruction leads an abnormal increase in CNS fluid and head circumference.
Demographics
About one in 1,000 children is born with hydrocephalus. Of those, 10% have DWM as the underlying cause of their condition. DWM has not been shown to be more frequent in any particular ethnic group or race. About 85% of babies born with DWM have one or more other congenital malformations, or some type of recognizable syndrome. The 15% that have no other malformations may be said to have "isolated" DWM.
Causes and symptoms
The true cause of DWM is unknown. However, the components of the malformation seem to be related to a disruption in development of the middle portion of the lower part of the brain in the embryonic stage. This affects growth and development of the cerebellum, especially the vermis, and the brainstem such that the foramina of Magendie and Luschka are partially or completely closed.
Most cases of isolated DWM occur by chance (sporadic) and have very little risk of recurrence in siblings or children of the affected individual. In a few cases, DWM may be inherited as an autosomal recessive trait, which would imply a 25% risk for recurrence in siblings.
Some syndromes that may occur with DWM are chromosomal (abnormal number of chromosomes in every cell of the body—usually sporadic), while others are hereditary. The empiric recurrence risk for non-syndromic DWM with other anomalies is about 5% for siblings or children of the affected individual.
Outward physical signs of DWM may be a bulging occiput (lower rear portion of the skull) and an increased total head circumference. Symptoms of DWM are those caused by hydrocephalus (if present) and dysgenesis/agenesis of the cerebellar vermis. In infants, symptoms can include irritability, seizures, vomiting, abnormal breathing, nystagmus (jerky eye movements), and slow motor development. Older children and adults may have headaches, ataxia (difficulties with coordination), visual disturbances, and/or developmental delay/mental retardation.
What are the clinical symptoms of disease?
The symptoms of the disease begin in the early childhood.The major clinical symptoms are neuromotor retardation (delay in normal neural and muscle tonus development),mental retardation and hyrocephalus. That means delayed development of Central Nervous System and locomotor system resulting in abnormal muscle tonus called "spasticity". Mental and intellectual functions are depressed in half of patients.The other 50% may have normal cognitive functions. Degree of symptoms depends on gravity of congenital disease.If the child has severe malformations from birth the signs may appear at early ages. But sometimes disease may be unnoticed until adult ages.Sometimes the only symptom can be the abnormal enlargement of head.Some childrens may appeal with the signs of increased intracranial pressure such as vomiting,convulsions,agitation or signs of impaired cerebellar function such as equilibrium problems dizzines,abnormal eye movements named nistagmus.
Diagnosis
DWM may be diagnosed in pregnancy by ultrasound as early as 12–14 weeks after conception, although ultra-sounds later in pregnancy are more sensitive. A level II ultrasound, a more detailed examination that can only be performed 18 weeks or later after conception, may be suggested to confirm the diagnosis of DWM and will look for the presence of other malformations. An amniocentesis, a procedure to analyze fetal chromosomes, is also usually offered.
After birth, DWM may be suspected because of physical or neurological signs, but it is only possible to establish the diagnosis of DWM by performing imaging studies of the brain through a computed tomography (CT) scan or magnetic resonance imaging (MRI).
What are the coincident malformations seen with Dandy-Walker Syndrome?
Coincidence with some other anomalies is another important feature of dandy walker syndrome. Disease may be together with the absence of an intracranial structure, "corpus callosum" which connects both cerebral hemispheres to each other and provides interrelationship between. Facial anomalies, extremity malformations and heart anomalies can be seen with disease.
Treatment
The primary treatment for DWM and associated hydrocephalus is the placement of a ventriculoperitoneal (VP) shunt. This is a procedure in which a neurosurgeon places one end of a small tube in a ventricle in the brain, and threads the other end under the skin down to the peritoneal (abdominal) cavity. The tube helps to direct excess CSF to the peritoneal cavity where it is reabsorbed by the body.
In some cases, the neurosurgeon may attempt a procedure called endoscopic fenestration. In this procedure a small, flexible viewing device, called an endoscope, is inserted into the brain and an opening is made between the third and fourth ventricles or in the foramina at the base of the brain. It is hoped that opening these passages will equalize CSF pressure throughout the central nervous system.
Other treatments include those for the symptoms of hydrocephalus and cerebellar agenesis, such as anti-seizure medications, and OT/PT for neuromuscular problems.
Recovery and rehabilitation
Some children recover completely after a shunt is placed, while others receive partial benefit. Shunting procedures are not always successful, and they carry a risk for serious infection. A child who retains neurologic deficits will likely require long-term care by a neurologist and OT/PT. Special accommodations for home care may also be needed.
Prognosis
Prognosis for DWM varies anywhere from excellent to fatal. The overall prognosis for DWM that occurs and is diagnosed as part of a known syndrome will depend on the possible prognoses for that particular syndrome, although the presence of DWM may have a negative impact. In other cases, DWM without other anomalies has a much better prognosis. As noted, prognosis is also critically dependent on the degree of hydrocephalus already present at birth or at the time of diagnosis.
What research is being done?
The NINDS conducts and supports a wide range of studies that explore the complex mechanisms of normal brain development. The knowledge gained from these fundamental studies provides the foundation for understanding abnormal brain development and offers hope for new ways to treat and prevent developmental brain disorders such as Dandy-Walker Syndrome.
General Discussion
Dandy-Walker Malformation is a rare malformation of the brain that is present at birth (congenital). It is characterized by an abnormally enlarged space at the back of the brain (cystic 4th ventricle) that interferes with the normal flow of cerebrospinal fluid through the openings between the ventricle and other parts of the brain (foramina of Magendia and Luschka). Excessive amounts of fluid accumulate around the brain and cause abnormally high pressure within the skull, swelling of the head (congenital hydrocephalus), and neurological impairment. Motor delays and learning problems may also occur. Dandy-Walker Malformation is a form of "Obstructive" or "Internal Noncommunicating Hydrocephalus," meaning that the normal flow of cerebrospinal fluid is blocked resulting in the widening of the ventricles.
References:
http://www.geocities.com/murat_yil/dandy.html http://www.answers.com/topic/dandy-walker-syndrome http://www.ninds.nih.gov/disorders/dandywalker/dandywalker.htm http://www.bchealthguide.org/kbase/nord/nord275.htm
