Dandy Walker Malformation

 Dandy Walker Malformation

Dandy-Walker malformation (DWM) or syndrome is a posterior fossa anomaly characterized by agenesis or hypoplasia of the vermis and cystic enlargement of the fourth ventricle causing upward displacement of tentorium and torcula. Most patients have hydrocephalus at the time of diagnosis. DMW is the most common posterior fossa malformation, and it typically occurs sporadically. This activity reviews the presentation of Dandy-Walker malformation and highlights the role of the interprofessional team in its management.

Objectives:

Review the etiology of Dandy-Walker malformation.

Describe the presentation of Dandy-Walker malformation.

Summarize the treatment of Dandy-Walker malformation.

Review the importance of improving care coordination among interprofessional team members to improve outcomes for patients affected by Dandy-Walker malformation.

Synonyms

Dandy-Walker Cyst

Dandy-Walker Deformity

Dandy-Walker Syndrome

DWM

Hydrocephalus, Internal, Dandy-Walker Type

Hydrocephalus, Noncommunicating, Dandy-Walker Type

Luschka-Magendie Foramina Atresia

Signs & Symptoms

The symptoms of Dandy Walker syndrome typically include developmental delay, low tone (hypotonia) or later high tone (spasticity), poor coordination and balance (ataxia), and sometimes enlarged head circumference and increased pressure within the skull due to hydrocephalus. Mental retardation occurs in fewer than half, most often in those with severe hydrocephalus, chromosome abnormalities or other birth defects. Seizures occur in 15-30% of those affected. Respiratory control centers in the brainstem are sometimes affected and can lead to respiratory failure, again most likely with severe hydrocephalus. The age at diagnosis varies depending on the onset and severity of hydrocephalus, and presence of other birth defects or medical problems.

The clinical presentation and imaging features of DWM overlap with isolated cerebellar vermis hypoplasia (CVH) and mega-cisterna magna (MCM), and these have been classified together as a spectrum of anomalies known as the Dandy-Walker complex. But emerging experience suggests that this is an oversimplification that may contribute to inaccurate information about both outcome and genetic risks. CVH consists of a small vermis without the striking upward rotation of the vermis, cystic enlargement of the 4th ventricle or enlarged posterior fossa that characterize typical DWM. This malformation has also been called the “Dandy-Walker variant”, a potentially confusing term. The available data regarding outcome is limited, but this is often more severe than in typical DWM. MCM is characterized by an enlarged posterior fossa despite normal or very nearly normal size of the cerebellum. The increased size is associated with an enlarged fluid collection beneath and often behind the cerebellum. This has been reported as a normal variant, but emerging experience suggests that it may be associated with developmental disabilities although these are usually less severe than seen in DWM or CVH. The uncertainty in prognosis for these three overlapping conditions is accounted for by both natural variability and difficulty in distinguishing them.

Causes

DWM results from defects in early embryonic development of the cerebellum and surrounding structures. A few patients have chromosome abnormalities including deletion of chromosome 3q24.3 (the location of the first DWM genes, known as ZIC1 and ZIC4), 6p25 or 13q32.2-q33.2, or duplication of 9p. In the remainder, it is probably due to other more complex genetic and perhaps environmental factors (teratogens) as the recurrence risk in siblings less than 5%. A few examples of affected siblings with isolated Dandy-Walker malformation have been reported, suggesting autosomal recessive or X-linked inheritance, but most of these are probably CVH and not typical DWM. In these families, the recurrence risk is higher, up to 25%. DWM may also occur as part of a genetic syndrome that includes multiple birth defects, such as the PHACES syndrome of facial hemangioma, heart and sternal defects and DWM. Many other syndromes and chromosome abnormalities have been reported with DWM, but most of these appear to have CVH rather than typical DWM.

Disorders with Similar Symptoms

Symptoms of the following disorders can be similar to those of Dandy-Walker malformation. Comparisons may be useful for a differential diagnosis:

Hydrocephalus is a condition in which abnormally widened (dilated) cerebral spaces in the brain (ventricles) inhibit the normal flow of cerebrospinal fluid (CSF). The cerebrospinal fluid accumulates in the skull and puts pressure on the brain tissue. An enlarged head in infants and increased cerebrospinal fluid pressure are frequent findings but are not necessary for the diagnosis of hydrocephalus. There are several different forms of hydrocephalus: communicating hydrocephalus, non-communicating hydrocephalus or obstructive hydrocephalus, internal hydrocephalus, normal pressure hydrocephalus, and benign hydrocephalus. (For more information on this disorder, choose “hydrocephalus” as your search term in the Rare Disease Database.)

Walker-Warburg syndrome (WWS) is a rare genetic multisystem disorder characterized by muscle disease and brain and eye abnormalities. The specific symptoms and severity of WWS vary greatly from case to case. The most consistent features are a smooth appearance of the surface of the brain due to lack of normal folds (lissencephaly), malformations of other brain structures (cerebellum and brain stem), various developmental abnormalities of the eyes, and progressive degeneration and weakness of the voluntary muscles (congenital muscular dystrophy). WWS is considered to be a form of muscular dystrophy and is inherited as an autosomal recessive genetic condition. (For more information on this disorder, choose “Walker Warburg” as your search term in the Rare Disease Database.)

Diagnosis

Dandy Walker malformation is diagnosed with the use of ultrasound, CT and MRI. Prenatal diagnosis of Dandy-Walker malformation is sometimes made by ultrasound or fetal MRI.

Standard Therapies

Treatment

Hydrocephalus associated with Dandy Walker syndrome is treated with surgery to insert a tube to redirect the fluid that surrounds the brain and to assist fluid drainage into other parts of the body that can absorb the fluid.

A supportive team approach for children with Dandy-Waller malformation is often warranted and may include special education, physical therapy and other medical, social or vocational services.

Genetic counseling is recommended for families that have a child with Dandy Walker malformation.