Dandy Walker Syndrome is known by several different names.  It is the result of abnormal development of the cerebellum and fourth ventricle and is often associated  with hydrocephalus.  It occurs 1 in 25,000 babies and females are affected more often. The disorder was first described in 1954, and was named Dandy Walker Syndrome in 1954 .There are certain characteristics associated with it.  Specific symptoms may appear early in infancy or in older children.  The prognosis is only moderately favorable.  There are specific imaging findings of Dandy Walker Syndrome.

Key Words

Dandy Walker Syndrome, cerebellum, fourth ventricle, hydrocephalus, ultrasound
 
 

 Dandy Walker is known by several names such as Dandy Walker Syndrome, Dandy Walker Malformation, Dandy Walker Cyst, and Dandy Walker Variant (1).  "The Dandy Walker Syndrome is a spectrum of disorders resulting from abnormal development of the cerebellum with associated maldevelopment of the fourth ventricle (2)."

 It occurs 1 in 25,000 babies and more often in females.  It accounts for approximately 1-4% of hydrocephalus cases (3).  In 1914, the disorder was first described by Dandy and Blackfan (4).  In 1954, Benda designated the disorder as Dandy Walker Syndrome and also reported a familial occurrence (5).  The cause is thought to from "abnormal embryogenesis of the roof of the fourth ventricle before the sixth or seventh gestational week (6).

 There are certain Dandy Walker characteristics.  Examples include fourth ventricle enlargement, the cerebellar vermis is partially or completely absent, and in the posterior fossa there is a cyst formation.  See Figure 1-1.  Hydrocephalus, increased intracranial pressure, may be present (7).  There may also be atresia of the Luschka and Magendie foramina (2).  The large cysts in the posterior fossa are made up of cerebral spinal fluid (CSF) (3).The cyst forms while the brain develops during early embryonic development.  The cyst usually has many blood vessels running through it.  If the blood vessels connects to the brain this would prohibit surgical removal (1).
 
 

Figure 1-1 demonstrates a Dandy Walker Cyst

 Slow motor development and progressive macrocrania are symptoms which occur many times in early infancy.  Symptoms of hydrocephalus in older children may include irritability, vomiting, convulsions, and/or cerebellar dysfunction signs such as ataxia and nystagmus (jerky eye movement) (7).  Also, in older children there may be delayed development such as inability to walk, poor coordination, or intellectually delayed (3). Increased head circumference, an occiput that bulges, cranial nerve dysfunction, unusual breathing patterns (7), weak neck muscles, poor control of the head, and spasticity are other symptoms.  20-30% may have seizures.  30% of patients have developmental malformations outside of the central nervous system (CNS).  Examples include cleft lip, cleft palate, cardiac malformations, orthopedic problems, respiratory problems, and urinary structural abnormalities (3).  Around 50% of the time Dandy Walker Malformation is associated with other intracranial anomalies (6).  Associated neural anomalies include "agenesis of the posterior cerebellar vermis, agenesis of the corpus callosum, aqueductal stenosis, seterotopias (8), microcephaly, macrocephaly, encephalocele, and lipomas.  See Figure 2-1.  Examples of chromosomal anomalies are Trisomies 13, 18, and 21 (6).  Associated non-neural anomalies include "abnormal lumbar vertebrae, polydactyly, syndactyly, polycystic kidneys, cataracts, retinal dysgenesis, and choroid coloboma (8)."  Dandy Walker Syndrome may be dramatic or totally asymptomatic (7)The treatment includes a shunt from the interior of the brain or cyst is put in so there is continuous drainage of the blocked CSF that is not flowing.  The primary malformation of the brain involves the maldevelopment of the cerebellum and is associated with a cyst in the area.  "The primary malformation of the brain, however, cannot be corrected, (3)."  The prognosis is only moderately favorable, even if there is early and correct treatment of the hydrocephalus (7).  The prognosis is also dependent upon the presence or absence of associated anomalies (6).
 
 

Figure 2-1 demonstrates Agenesis of the Corpus Callosum

The enlargement of the fourth ventricle and the absent vermis can be seen before 20 weeks by ultrasound.  Dandy Walker cysts cause elevation of the tentorium,  which can be seen by ultrasound, and elevation of the torcula, which cannot be seen by ultrasound (2).  Therefore, Dandy Walker Syndrome is usually diagnosed before birth by ultrasound (1).  If it is not diagnosed before birth, the majority are usually diagnosed within the first year of life (3).  A diagnosis can be definitely made by Ultrasound, Computed Tomography (CT), or Magnetic Resonance Imaging (MRI) (5).On ultrasound the posterior fossa cyst can have various sizes.  There will be splaying of the cerebellar hemispheres because of complete or partial agenesis of the cerebellar vermis.  The two cause the cisterna magna to be enlarged.  There may also be ventriculomegaly (6).  See Figures 3-1 and 4-1.  An x-ray of the skull demonstrates the posterior fossa as being enlarged with superior displacement of torcular herophie and the lateral sinus grooves.  CT and MRI demonstrates a large and badly misshapened fourth ventricle; a cyst that is large, ependymal-lined, and may extend into the spinal canal causing hypoplastic and superiorly displaced cerebellar hemispheres; the posterior vermis may be hypoplastic or absent; and enlargement of the aqueduct of Sylvius, third and lateral ventricles (8).  See Figure 5-1.
 
 

Figure 3-1 demonstrates Dandy Walker involving the vermis and cisterna magna.

 

  Figure 4-1 demonstrates Ventriculomegaly. 

Figure 5-1 demonstrates a MRI image of Dandy Walker.

Dandy Walker Syndrome has certain characteristics, symptoms, and imaging findings.  These are important for the physician to help in the treatment.  The specific ultrasound imaging findings are significant to the sonographer.

1. www.geocities.com
2. Callen, Peter W.  Ultrasonography in Obstetrics and Gynecology.  W.B. Saunders Company.  1994.  Pp. 192-194.
3. www.bcm.tmc.edu.com
4. www.nyneurosurgery.org
5. www.specialchild.com
6. Hagen-Ansert, Sandra.  Textbook of Diagnostic Ultrasonography.  Volume 1.  5th edition.  Mosby.  2001.  Pp.  776, 784, 785.
7. www.ninds.nih.gov.com
8. www.icondata.com