Dandy-Walker Syndrome
Dandy-Walker syndrome
Definition
Dandy-Walker syndrome refers to a group of specific, congenital (present at birth) brain malformations, and is a common cause of hydrocephalus (increased fluid in the brain).
Description
Dandy-Walker syndrome is more often referred to as Dandy-Walker malformation (DWM) or Dandy-Walker complex. The condition is named for doctors Walter E. Dandy and Arthur E. Walker, who described the signs and symptoms of the condition in the early 1900s.
The brain contains four ventricles, which are inner, hollow portions filled with cerebrospinal fluid (CSF). The first and second (lateral) ventricles are inside the cerebral hemispheres, and the third and fourth ventricles are below them, closer to the brainstem. DWM consists of a specific group of brain malformations, including enlargement of the fourth ventricle, complete or partial agenesis (lack of development) of the cerebellar vermis (the middle portion of the cerebellum , which lies directly behind the cerebral hemispheres), and cyst formation and dilation of the posterior fossa (a small, hollow section between the lower cerebellum and skull).
A further defining characteristic of DMW is blockage or closure of the foramina (openings) of Magendie and Luschka, two channels at the base of the brain through which CSF normally flows. When these openings are obstructed, CSF produced in the ventricles has no outlet for normal circulation. This causes fluid pressure to build, and the ventricles to enlarge (always the fourth, and often the third and lateral ventricles).
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.
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) .
Treatment team
A neurosurgeon would perform any surgical procedures (such as shunts) needed to help relieve hydrocephalus or intracranial cysts. Depending on the severity of any neurological symptoms and the presence or absence of other congenital malformations, various specialists involved in the care of a child with DWM can include a neonatologist (specialist in the care of newborns), developmental pediatrician, geneticist, neurologist , specialized nursing care, and occupational/physical therapists (OT/PT).
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.
Clinical trials
There are no clinical trials for Dandy-Walker syndrome.
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.
Resources
BOOKS
Volpe, Joseph, J. Neurology of the Newborn, 4th edition. Philadelphia: W.B. Saunders Company, 2001.
PERIODICALS
Ecker, Jeffrey L., et al. "The Sonographic Diagnosis of Dandy-Walker and Dandy-Walker Variant: Associated Findings and Outcomes." Prenatal Diagnosis 20 (2000): 328–332.
Klein, O., et al. "Dandy-Walker Malformation: Prenatal Diagnosis and Prognosis." Childs Nervous System 19 (August 2003): 484–9.
Koble, Nicole, et al. "Dandy-Walker Malformation: Prenatal Diagnosis and Outcome." Prenatal Diagnosis 20 (2000): 318–327.
OTHER
NINDS Dandy-Walker Syndrome Information Page. The National Institute of Neurological Disorders and Stroke. April 2, 2003 (March 30, 2004). <http://www.ninds.nih.gov/health_and_medical/disorders/dandywalker.htm>.
ORGANIZATIONS
Dandy-Walker Syndrome Network. 5030 142nd Path W, Apple Valley, MN 55124. (952) 423-4008.
Hydrocephalus Association. 870 Market Street, Suite 705, San Francisco, CA 94102. (888) 598-3789; Fax: (415) 732-7044. <http://www.hydroassoc.org>.
Hydrocephalus Research Foundation. 1670 Green Oak Circle, Lawrenceville, GA 30243. (770) 995-9570; Fax: (770) 995-8982.
Hydrocephalus Support Group, Inc. PO Box 4236, Chesterfield, MO 63006-4236. (636) 532-8228; Fax: (314) 995-4108.
National Hydrocephalus Foundation. 12413 Centralia Road, Lakewood, CA 90715-1623. (888) 857-3434; Fax: (562) 924-6666. <http://nhfonline.org>.
Scott J. Polzin, MS, CGC