eMedicine Specialties > Radiology > Pediatrics

Dandy-Walker Malformation

Lutfi Incesu, MD, Professor, Department of Radiology, Ondokuz Mayis University School of Medicine; Chief, Neuroradiology and MR Unit, Department of Radiology, Ondokuz Mayis University Hospital, Turkey
Anil Khosla, MBBS, Assistant Professor, Department of Radiology, Section of Neuroradiology, Mallinckrodt Institute of Radiology, Washington University School of Medicine, Veterans Affairs Medical Center of St Louis

Updated: Sep 11, 2009

Introduction

Background

Dandy-Walker malformation is a rare congenital malformation that involves the cerebellum and fourth ventricle. Dandy-Walker malformation is characterized by agenesis or hypoplasia of the cerebellar vermis, cystic dilatation of the fourth ventricle, and enlargement of the posterior fossa. A large number of concomitant problems may be present, but Dandy-Walker malformation is recognized whenever these 3 features are found. Approximately 70-90% of patients have hydrocephalus, which often develops postnatally. Dandy-Walker malformation may be associated with atresia of the foramen of Magendie and, possibly, the foramen of Luschka.^1,2,3

Dandy-Walker malformation was first described by Dandy and Blackfan in 1914.⁴ Since the original description, additional studies have reported on the various morphologic features of the syndrome. Not until 1954 did Benda first emphasize that atresia of the cerebellar outlet foramina is not an essential feature of the condition and suggested the now widely accepted term Dandy-Walker malformation.⁵

Studies by D'Agostino in 1963 and Hart et al in 1972 further defined the characteristic triad of Dandy-Walker malformation as consisting of (1) complete or partial agenesis of the vermis, (2) cystic dilatation of the fourth ventricle, and (3) an enlarged posterior fossa with upward displacement of lateral sinuses, tentorium, and torcular herophili. This triad is typically found in association with supratentorial hydrocephalus, which should be considered a complication rather than part of the malformation complex.^6,7

Dandy-Walker complex

Classically, posterior fossa cystic malformations have been divided into Dandy-Walker malformation, Dandy-Walker variant, mega cisterna magna, and posterior fossa arachnoid cyst. Precisely differentiating the malformations may not be possible using imaging studies. Dandy-Walker malformation, variant, and mega cisterna magna are currently believed to represent a continuum of developmental anomalies on a spectrum that has been termed the Dandy-Walker complex.^8,9,10

Dandy-Walker complex is characterized by an enlarged posterior fossa; a high position of the tentorium, with upward displacement of the lateral sinuses; torcular herophili associated with varying degrees of vermian aplasia or hypoplasia; and a cystic dilatation of the fourth ventricle that nearly fills the entire posterior fossa. Since the vermis is present in posterior fossa arachnoid cyst, this is considered separately from Dandy-Walker malformation.

Dandy-Walker variant

This sagittal T1-weighted MRI shows agenesis of the corpus callosum and a hypoplastic inferior vermis in a 13-year-old girl with thoracal scoliosis and Dandy-Walker variant. The fourth ventricle is slightly enlarged, but the posterior fossa typically is normal in size.

• Dandy-Walker variant consists of vermian hypoplasia and cystic dilatation of the fourth ventricle, without enlargement of the posterior fossa.

Mega cisterna magna

This sagittal T1-weighted MRI shows a large retrocerebellar cerebrospinal fluid collection and a normal fourth ventricle and vermis in a patient with mega cisterna magna in Dandy-Walker malformation.

• Mega cisterna magna consists of an enlarged posterior fossa secondary to an enlarged cisterna magna, with a normal cerebellar vermis and fourth ventricle.

Arachnoid cyst

A posterior fossa arachnoid cyst in a 15-month-old girl with a lumbar pilonidal sinus. The sagittal T1-weighted MRI shows a large posterior fossa cyst that is compressing the cerebellar hemispheres, vermis, fourth ventricle (arrow), and brainstem.

• Retrocerebellar arachnoid cysts of developmental origin are uncommon but clinically important. True retrocerebellar arachnoid cysts displace the fourth ventricle and cerebellum anteriorly and show significant mass effect. Because there are different surgical therapy approaches for posterior fossa arachnoid cyst and Dandy-Walker malformation, it is essential to differentiate between the 2 entities.¹¹

Recent studies

Salihu et al studied infant mortality in non-Hispanic black and non-Hispanic white neonates with Dandy-Walker syndrome and found that Dandy-Walker syndrome has one of the largest black-white disparities in postneonatal survival. Neonatal mortality was similar for non-Hispanic blacks and non-Hispanic whites, but non-Hispanic blacks had an 8-fold increased risk for postneonatal mortality. Adjustment for fetal growth and other maternal and infant characteristics resulted in a 10-fold increased risk of mortality for non-Hispanic black infants, as compared to non-Hispanic whites. Adjustment for preterm birth reduced the risk differential, but non-Hispanic black infants were still more than 6 times as likely to die during the postneonatal period than non-Hispanic whites.¹²

In another study by Salihu and co-workers, infants with Dandy-Walker syndrome and 2 or more affected organ systems were approximately 6 times as likely to die postneonatally as were patients with isolated Dandy-Walker syndrome. According to the authors, these findings confirm the widely held belief that Dandy-Walker syndrome is a heterogeneous, rather than a homogeneous, disorder.¹³

Pathophysiology

Dandy-Walker malformations are formed during embryogenesis. Insults of varying severity to both the developing cerebellar hemispheres and the fourth ventricle are currently believed to be the genesis of this anomaly.

Multiple theories have been offered to explain the diffuse manifestations of Dandy-Walker malformation, but no single theory has proven satisfactory or has been widely accepted. Theories regarding the origin of the malformation have centered on defects in embryogenesis.

Dandy and Blackfan (in 1914) and Taggart and Walker (in 1942) believed that the massive dilatation of the fourth ventricle originates in a congenital obstruction of the outlets of Luschka and Magendie. This theory includes the presence of a developmental cerebellar defect that begins before embryologic differentiation of the fourth ventricle foramina and results in blockage or atresia of the foramina of Magendie and Luschka and then, in turn, results in cystic transformation of the roof of the fourth ventricle and in an obstructive (noncommunicating) hydrocephalus, in which a cyst arises from compromised absorption of CSF.^4,14,15

The most comprehensive theory is that of dysembryogenesis involving the hindbrain:

• An insult that leads to developmental arrest in the formation of the hindbrain, with lack of fusion of the cerebellum in the midline, can be localized temporally between the 7th and 10th gestational weeks. This results in persistence of the anterior membranous area, which extends and herniates posteriorly. Simultaneous formation of the foramen of Magendie, tentorium, superior longitudinal sinus, straight sinus, torcular herophili, and lateral sinuses helps explain their association with Dandy-Walker malformation.

Inheritance

The etiology of Dandy-Walker malformation is heterogeneous, and familial occurrence has been reported as well. A few cases resulting from autosomal recessive genes have been reported, although in most patients, the cause of Dandy-Walker malformation is not known. Genetic counseling is critical to estimate the risk of recurrence of genetic disorders in family members.^1,16,17,18

Etiologic heterogeneity and a low recurrence risk in siblings (1-5%) for Dandy-Walker malformation have been noted, and an increased frequency of associated congenital heart disease, cleft palate, and neural tube defects appears to exist. An unusual case of an infant with both Ellis-van Creveld and Dandy-Walker syndromes as well as homozygosity for an unusually long heterochromatic segment of the long arm of chromosome 9 (9qh+) was reported. An extensive tabulation of single gene disorders, chromosomal aberrations, teratogen-induced conditions, sporadic forms, or forms with undetermined inheritance associated with Dandy-Walker malformation were also found. In a large series, an abnormal karyotype was found in 5 of 17 patients.¹

Predisposing factors

Predisposing factors for Dandy-Walker malformation include gestational exposure to rubella (in the first trimester), cytomegalovirus, toxoplasmosis, warfarin, alcohol, and isotretinoin.

Frequency

United States

The incidence of Dandy-Walker malformation is 1 case per 25,000-35,000 live births. Dandy-Walker malformation accounts for approximately 1-4% of hydrocephalus cases.¹⁹

Mortality/Morbidity

Overall mortality rates of 12-50% have been reported in Dandy-Walker malformation in the pediatric neurosurgical literature. Associated congenital anomalies contributed to 83% of postnatal deaths. Mortality rates have improved significantly over the past 30 years as a result of better anesthesia and shunting devices and the reduction of posterior fossa exploration. Sudden and unexpected death is an uncommon but well-recognized occurrence in patients with Dandy-Walker malformation.¹²

The prognosis is difficult to formulate, and it is only moderately favorable, even when hydrocephalus is treated early and correctly. In one study, 3 patients with isolated Dandy-Walker cysts with hydrocephalus diagnosed in utero were treated at birth with shunting, and all 3 had normal outcomes. An extreme range of severity is seen in this malformation. The presence of multiple congenital defects may affect survival adversely. Some people live with Dandy-Walker variant their entire lives without developing any symptoms. Some infants may have it in association with other syndromes, resulting in severe complications or death.^20,21

Sex

Dandy-Walker malformation occurs more frequently in females than in males. The male-to-female ratio was 1:3 in one Spanish series.

Age

Depending on the time of onset and degree of hydrocephalus, the age at diagnosis varies from birth to older childhood. Presentation in adulthood has been reported but is unusual.²² Patients with Dandy-Walker variant are more likely to present in adulthood than in infancy or childhood.²³

Anatomy

Most definitions of Dandy-Walker malformation have included dysgenesis of the vermis, cystic dilatation of the fourth ventricle, and enlargement of the posterior fossa with elevation of the tentorium/torcula.

Dandy-Walker malformation consists of a malformation of the roof of the fourth ventricle and of the cerebellum. The cerebellum is poorly developed and is displaced upwards and laterally.
The enlarged fourth ventricle balloons out backward. The fourth ventricle is grossly misshapen because it is a membrane-wrapped cyst that extends into the foramen magnum. The membrane-wrapped cyst may lift and displace the posterior portion of the brain, as well as cause an internal obstruction of normal CSF flow, with resultant hydrocephalus.

A sagittal T1-weighted magnetic resonance imaging (MRI) scan in a 5-year-old girl (also see Images 2-3 in Multimedia Section) shows a large posterior fossa cyst elevating the torcular herophili and sinus rectus (short arrow). The hypoplastic vermis is everted over the posterior fossa cyst (long arrow). The cerebellar hemispheres and brainstem (b) are hypoplastic. Thinned occipital squama is seen (arrowheads).

This sagittal T1-weighted MRI scan in an 11-day-old boy (also see Image 5 in Multimedia Section) shows agenesis of the corpus callosum, a hypoplastic brainstem (b), elevation of the torcular herophili (lambdoid-torcular inversion, large arrow), a large fourth ventricle, and a markedly hypoplastic vermis that is rotated superiorly (small arrow).

An axial T2-weighted MRI (also see Image 1 and Image 3, in Multimedia Section) scan that shows hydrocephalus, a large cerebrospinal fluid cyst in the posterior fossa, thinned occipital bone (arrows), and hypoplastic cerebellar hemispheres with a winged appearance (c).

An axial T1-weighted MRI (also see Images 1-2, in Multimedia Section) scan showing ventriculomegaly and a superiorly displaced posterior fossa cyst.

An axial computed tomography (CT) scan in a 7-year-old girl with hydrocephalus showing a large cerebrospinal fluid cyst in the posterior fossa and hypoplastic cerebellar hemispheres with a winged appearance (c).

Common findings of Dandy-Walker malformation include the following:

• Enlarged posterior fossa
• Varying degrees of cerebellar and vermian hypoplasia or complete vermian absence (see Image 1, Image 4)
• Cyst formation in the posterior fossa (see Image 1, Image 4, Image 6)
• Vermian remnant everted above the posterior fossa cyst (see Image 1, Image 4)
• Hypoplastic cerebellar hemispheres winged anterolaterally (outward) in front of the cyst (see Image 2, Image 6)
• Absence of the foramina of Luschka and Magendie
• Obstructive hydrocephalus secondary to cystic dilatation of the fourth ventricle (70-90%; see Images 2-3, Image 6)
• Abnormally high position of the straight sinus, torcular herophili, and tentorium (see Image 1, Image 3, Image 5)
• Sinus confluence and lateral sinuses elevated above the lambdoid sutures (high tentorial insertion, also called lambdoid-torcular inversion; see Image 1, Image 4)
• Aqueductal obstruction, which may affect the need for supratentorial decompression (and is, therefore, an important component)
• If callosal agenesis coexists (20-25%), development of dilatation of the occipital horns (colpocephaly; see Images 4-5)
• Possible brainstem compression and hypoplasia; the degree of pontine hypoplasia is directly related to the degree of cerebellar hypoplasia (see Image 1, Image 4)²⁴
• Thinning and bulging of the occipital bones (see Images 1-2, Image 4)

Associated central nervous system (CNS) abnormalities of Dandy-Walker malformation are reported in 70% of children.

• Dysgenesis of the corpus callosum (20-25%; see Images 4-5)³
• Lipoma of the corpus callosum
• Holoprosencephaly (25%)
• Porencephaly
• Dysplasia of the cingulate gyrus (25%)
• Schizencephaly
• Polymicrogyria/gray matter heterotopia (5-10%)
• Cerebellar heterotopia
• Occipital encephalocele (7%)³
• Microcephaly
• Dermoid cysts
• Malformation of the cerebellar folia (25%)
• Malformation of the inferior olivary nucleus
• Hamartoma of the tuber cinereum
• Syringomyelia²
• Klippel-Feil deformity
• Spina bifida²⁰
• Lumbosacral meningoceles
• Spinal lipoma

Non-CNS-associated malformations are reported in 20-33% of children.

• Orofacial deformities and cleft palate (6%)
• Polydactyly and syndactyly¹⁷
• Cardiac anomalies²⁵
• Urinary tract abnormalities (polycystic kidneys)²²
• Cataracts, retinal dysgenesis, and choroid coloboma
• Facial hemangioma
• Hypertelorism
• Meckel-Gruber syndrome¹
• Neurocutaneous melanosis^24,26

Presentation

Patients with Dandy-Walker malformation present with developmental delay, enlarged head circumference, or signs and symptoms of hydrocephalus. The clinical presentation depends to some extent on the particular combination of developmental anomalies in each infant.^10,20,27

An estimated 80% of patients have normal ventricles at birth and, by age 1 year, 80% have ventriculomegaly. Hydrocephalus is present in approximately 90% of patients at the time of diagnosis.

If no other anomalies are present, the only symptom can be an abnormal enlargement of the head. Typical signs of increased intracranial pressure seen in older children and adults may be absent in infants secondary to the ability of the head to increase in size. Macrocrania is usually the consequence of hydrocephalus but, in some patients, it results from massive enlargement of the posterior fossa by the posterior fossa cyst. In this situation, macrocrania precedes the development of hydrocephalus, giving the skull a characteristic dolichocephalic shape, with bulging of the occiput.

Difficulty with balance, spasticity, and poor fine motor control are common. The degree of developmental delay appears to be related to the level of control of hydrocephalus and to the extent of supratentorial anomalies. Interference with respiratory control centers in the brainstem may cause respiratory failure. Seizures occur in 15-30% of patients.

Hearing or visual difficulties, systemic abnormalities, and CNS abnormalities are associated with poor intellectual development. Subnormal intelligence (intelligence quotient <83) is manifested in 41-71% of patients. More severe intellectual impairment has been observed in patients with agenesis of the corpus callosum.

Preferred Examination

Dandy-Walker malformation is best diagnosed with the help of ultrasonography (US) and magnetic resonance imaging (MRI). US may be the initial examination performed because it can be done portably and without sedation, as well as allowing multiplanar imaging.^21,28

The introduction of modern imaging techniques, specifically MRI, has radically changed the evaluation of symptoms related to the posterior fossa.

MRI is usually performed for detailed evaluation of Dandy-Walker malformation lesions and complications after the diagnosis is suspected using computed tomography (CT) and US. MRI can best define the relationship between the cyst and the fourth ventricle, and it can detect vermian rotation and the signs of vermian dysgenesis.

MRI allows surgeons to accurately view the cerebellum and associated structures, determine which form the malformation has taken, and gauge the progress of the malformation. MRI also demonstrates which space should be shunted first. Recently, MRI has been frequently used for diagnosing fetal craniospinal anomalies.

Since it can distinguish between hydrocephalus associated with Dandy-Walker and hydrocephalus associated with other etiologies, CT scanning is also useful in Dandy-Walker malformation.

The classic abnormal findings of Dandy-Walker malformation described on cranial CT and MRI can also be demonstrated on cranial sonography. US is routinely used during the antenatal period as a screening method, and it is particularly used for postnatal follow-up studies of hydrocephalus. US evaluation of posterior fossa cystic abnormalities in the newborn is best accomplished via a posterolateral fontanelle approach or through the cisterna magna posteriorly.

In recent years, plain radiography has been primarily used in the evaluation of shunt malfunction as well as for diagnosing associated anomalies.

Limitations of Techniques

Plain radiographs have diagnostic importance in the evaluation of shunt malfunction and bone abnormalities.

CT is an effective diagnostic method; however, it exposes the infant to ionizing radiation. Clearly distinguishing the subtypes of Dandy-Walker complex on axial CT images is difficult. In addition, evaluating subtle supratentorial pathologies and associated abnormalities on CT scans may not be easy because its routine use is constrained by the axial plane.

MRI is relatively expensive. High-quality MRI scans require patient cooperation or sedation.

US is limited because it is heavily operator-dependent. Abnormalities such as the gyral, dural, tentorial, and skull anomalies that accompany Dandy-Walker malformations are not clearly depicted by US.

Differential Diagnoses

Arachnoid Cyst
Epidermoid, Brain

Other Problems to Be Considered

Isolated fourth ventricle
Mega cisterna magna
Joubert syndrome
Tectocerebellar dysraphia

The differential diagnosis of posterior fossa cystic lesions is summarized below.

Dandy-Walker malformation

Complete or partial cerebellar vermian hypoplasia
Cystic dilatation of fourth ventricle
Large posterior fossa
High torcular and transverse sinuses
Hydrocephalus

Dandy-Walker variant

Varying cerebellar primarily inferior vermian hypoplasia
Varying enlargement of the fourth ventricle
Normal posterior fossa volume

Mega cisterna magna

Normal cerebellar hemispheres and vermis
Large retrocerebellar CSF collection communicates with fourth ventricle
Normal fourth ventricle
Occasionally, quite enlarged posterior fossa

Posterior fossa arachnoid cyst

Noncommunicating posterior fossa cyst
Normal but distorted vermis and cerebellum
Normal but displaced fourth ventricle
Usually enlarged posterior fossa

Radiography

Findings

On conventional radiographs, the posterior fossa is disproportionately enlarged, with characteristic thinning and bulging of the occiput. Increased pressure from the massively dilated fourth ventricle along with prominent CSF pulsations through the cyst fluid causes widening of the diastatic lambdoid sutures and erosive scalloping of the occiput. Torcular herophili and lateral sinus grooves are located high above the lambdoid angle (torcular-lambdoid angle inversion).⁹

Degree of Confidence

Plain radiographs have diagnostic importance in imaging bony abnormalities and in the evaluation of ventriculoperitoneal shunt malfunction.

Computed Tomography

Findings

CT is used to diagnose Dandy-Walker malformation and to follow ventricular shunt function in shunted patients. Nonenhanced CT examination successfully delineates multiple components of Dandy-Walker malformation, which includes partial or complete absence of the cerebellar vermis; posterior fossa cyst contiguous with the fourth ventricle; small and widely separated cerebellar hemispheres; anterior and lateral displacement of hypoplastic cerebellar hemispheres; anterior displacement of pons; elevated imprint of the transverse sinuses, with thinning and bulging of the bones of the posterior fossa; scalloping of petrous pyramids; and hydrocephalus.

An axial computed tomography (CT) scan in a 7-year-old girl with hydrocephalus showing a large cerebrospinal fluid cyst in the posterior fossa and hypoplastic cerebellar hemispheres with a winged appearance (c).

An axial CT scan in a 1-day-old boy that shows a large posterior fossa cyst, separation of the lambdoid sutures (large arrows), and concavity of the petrous ridges (small arrows).

Degree of Confidence

CT scans can depict the malformation relatively well, but a slice may miss the relevant presence of the vermis. Clearly distinguishing Dandy-Walker complex subtypes using axial CT images is difficult.

False Positives/Negatives

See Degree of Confidence, above.

Magnetic Resonance Imaging

Findings

Malformations of the CNS are best delineated using MRI. The diagnosis is straightforward when typical MRI findings are present. MRI is usually required for better anatomic resolution prior to surgical intervention.²⁸

Nonenhanced routine cranial MRI can image the altered anatomy and provide excellent images in all projections (sagittal, axial, coronal), of which the sagittal view is one of the most useful.

A sagittal T1-weighted magnetic resonance imaging (MRI) scan in a 5-year-old girl (also see Images 2-3 in Multimedia Section) shows a large posterior fossa cyst elevating the torcular herophili and sinus rectus (short arrow). The hypoplastic vermis is everted over the posterior fossa cyst (long arrow). The cerebellar hemispheres and brainstem (b) are hypoplastic. Thinned occipital squama is seen (arrowheads).

This sagittal T1-weighted MRI scan in an 11-day-old boy (also see Image 5 in Multimedia Section) shows agenesis of the corpus callosum, a hypoplastic brainstem (b), elevation of the torcular herophili (lambdoid-torcular inversion, large arrow), a large fourth ventricle, and a markedly hypoplastic vermis that is rotated superiorly (small arrow).

This sagittal T1-weighted MRI shows agenesis of the corpus callosum and a hypoplastic inferior vermis in a 13-year-old girl with thoracal scoliosis and Dandy-Walker variant. The fourth ventricle is slightly enlarged, but the posterior fossa typically is normal in size.

An enlarged posterior fossa, cyst formation in the posterior fossa, anterolaterally winged cerebellar hemispheres (winged outward), absence of falx cerebelli, and scalloping of petrous pyramids are well-demonstrated on T1-weighted images (see Images 1-5).

Sagittal MRI can help evaluate an abnormally high position of the straight sinus, torcular herophili, tentorium, high tentorial insertion (lambdoid-torcular inversion), hypoplastic and compressed brainstem, and obstructive hydrocephalus secondary to cystic dilatation of the fourth ventricle in patients with Dandy-Walker malformation.²⁴

An axial T1-weighted MRI (also see Image 4, in Multimedia Section) showing an elevated, anteriorly displaced torcular herophili (arrow) and a superiorly displaced posterior fossa cyst.

Assessing the presence of associated supratentorial anomalies is important, since the prognosis for patients is much better in the absence of the anomalies (see Image 2, Image 4, Image 8). MRI affords an accurate, objective, and detailed identification of supratentorial anomalies. Recently, MRI and US have been used as diagnostic tools in the antenatal period.

Degree of Confidence

MRI is reliable and is the diagnostic method of choice in differentiating Dandy-Walker malformation from other posterior fossa pathologies.

False Positives/Negatives

MRI findings in Dandy-Walker malformation may be confused with mega cisterna magna, arachnoid cyst, isolated fourth ventricle, and Joubert syndrome.

This sagittal T1-weighted MRI shows a large retrocerebellar cerebrospinal fluid collection and a normal fourth ventricle and vermis in a patient with mega cisterna magna in Dandy-Walker malformation.

A posterior fossa arachnoid cyst in a 15-month-old girl with a lumbar pilonidal sinus. The sagittal T1-weighted MRI shows a large posterior fossa cyst that is compressing the cerebellar hemispheres, vermis, fourth ventricle (arrow), and brainstem.

Joubert syndrome in an 8-month-old boy. The axial CT scan obtained near the pontomesencephalic junction shows a batwing configuration of the fourth ventricle and unusual definition of the superior cerebellar peduncles at this level (arrows). The vermis is dysgenetic, and the 2 cerebellar hemispheres appose each other in the midline.

Ultrasonography

Findings

Classic abnormal findings described on cranial CT and MRI scans can also be demonstrated on cranial sonography. Commercially available equipment is used, with transducers of 3-7.5 MHz (depending on the size of the patient's head). Transducers of 5-7.5 MHz are used for newborns, and transducers of 3-5 MHz are used for older infants.

On US, a large posterior fossa midline cyst that communicates with the fourth ventricle is best demonstrated on midline sagittal sections. The anterolaterally displaced hypoplastic cerebellar hemispheres are best seen in the coronal projection. Sagittal and coronal sections can demonstrate enlargement of the posterior fossa, high position of the tentorium, and dilated third and lateral ventricles.

Scans performed with the transducer can show a large posterior fossa cyst and hypoplastic cerebellar hemispheres. This is accomplished by using the transfontanel approach as well as by placing the transducer directly over the posterior or posterolateral fontanelle.

In these patients, it is important to assess the supratentorial compartment for associated anomalies, such as callosal agenesis.

Using US, Dandy-Walker malformation is usually discovered before birth, although prominence of the cisterna magna is often confused with Dandy-Walker malformation in utero.

An in utero sonogram of Dandy-Walker malformation; note the abnormal cerebellar vermis in association with a posterior fossa cyst (arrow) and splaying of the cerebellar hemispheres. Image courtesy of Ecker et al.

Degree of Confidence

US is heavily operator-dependent. Associated findings of Dandy-Walker malformation, such as pachygyria, polymicrogyria, heterotopias, and dural abnormalities, may be missed.

False Positives/Negatives

Fetal US can demonstrate Dandy-Walker malformation and variant, but caution should be exercised because the normal developing cerebellum can mimic hypoplasia.

Angiography

Findings

Radiographic angiography can demonstrate angiographic features of Dandy-Walker malformation. In the arterial phase, the posterior cerebral vessels are elevated. The superior cerebellar arteries are displaced anterosuperiorly above the posterior cerebral arteries. The posterior inferior cerebellar arteries (PICAs) are shortened, with high tonsillar loop. The inferior vermian branches of the PICA are absent. In some patients, the entire PICA is absent or hypoplastic. In the venous phase, arteriography shows absence of the inferior vermian veins, elevation of the great vein of Galen, and high position of the transverse sinuses.³³

Intervention

Treatment usually consists of a shunt to treat associated hydrocephalus. The neurosurgeon can shunt the cyst (cystoperitoneal), the ventricles (ventriculoperitoneal), or both.^20,34

Medicolegal Pitfalls

• Failure to diagnose Dandy-Walker malformation with hydrocephalus in a neonate or a child can cause serious neurologic complications.
• A faulty diagnosis, such as mega cisterna magna or arachnoid cyst instead of Dandy-Walker malformation, can lead to morbidity and mortality.

Special Concerns

• US can be performed during pregnancy, and the diagnosis of Dandy-Walker malformation can be made antenatally. To confirm the diagnosis and gain detailed information, MRI evaluation can be used antenatally.²⁸
• Genetic counseling may be needed because a familial occurrence has been reported. Fetal karyotyping is also recommended for chromosomal analysis.^1,16,18

Multimedia

Media file 1: A sagittal T1-weighted magnetic resonance imaging (MRI) scan in a 5-year-old girl (also see Images 2-3 in Multimedia Section) shows a large posterior fossa cyst elevating the torcular herophili and sinus rectus (short arrow). The hypoplastic vermis is everted over the posterior fossa cyst (long arrow). The cerebellar hemispheres and brainstem (b) are hypoplastic. Thinned occipital squama is seen (arrowheads).

Media file 2: An axial T2-weighted MRI (also see Image 1 and Image 3, in Multimedia Section) scan that shows hydrocephalus, a large cerebrospinal fluid cyst in the posterior fossa, thinned occipital bone (arrows), and hypoplastic cerebellar hemispheres with a winged appearance (c).

Media file 3: An axial T1-weighted MRI (also see Images 1-2, in Multimedia Section) scan showing ventriculomegaly and a superiorly displaced posterior fossa cyst.

Media file 4: This sagittal T1-weighted MRI scan in an 11-day-old boy (also see Image 5 in Multimedia Section) shows agenesis of the corpus callosum, a hypoplastic brainstem (b), elevation of the torcular herophili (lambdoid-torcular inversion, large arrow), a large fourth ventricle, and a markedly hypoplastic vermis that is rotated superiorly (small arrow).

Media file 5: An axial T1-weighted MRI (also see Image 4, in Multimedia Section) showing an elevated, anteriorly displaced torcular herophili (arrow) and a superiorly displaced posterior fossa cyst.

Media file 6: An axial computed tomography (CT) scan in a 7-year-old girl with hydrocephalus showing a large cerebrospinal fluid cyst in the posterior fossa and hypoplastic cerebellar hemispheres with a winged appearance (c).

Media file 7: An axial CT scan in a 1-day-old boy that shows a large posterior fossa cyst, separation of the lambdoid sutures (large arrows), and concavity of the petrous ridges (small arrows).

Media file 8: This sagittal T1-weighted MRI shows agenesis of the corpus callosum and a hypoplastic inferior vermis in a 13-year-old girl with thoracal scoliosis and Dandy-Walker variant. The fourth ventricle is slightly enlarged, but the posterior fossa typically is normal in size.

Media file 9: This sagittal T1-weighted MRI shows a large retrocerebellar cerebrospinal fluid collection and a normal fourth ventricle and vermis in a patient with mega cisterna magna in Dandy-Walker malformation.

Media file 10: A posterior fossa arachnoid cyst in a 15-month-old girl with a lumbar pilonidal sinus. The sagittal T1-weighted MRI shows a large posterior fossa cyst that is compressing the cerebellar hemispheres, vermis, fourth ventricle (arrow), and brainstem.

Media file 11: Joubert syndrome in an 8-month-old boy. The axial CT scan obtained near the pontomesencephalic junction shows a batwing configuration of the fourth ventricle and unusual definition of the superior cerebellar peduncles at this level (arrows). The vermis is dysgenetic, and the 2 cerebellar hemispheres appose each other in the midline.

Media file 12: An in utero sonogram of Dandy-Walker malformation; note the abnormal cerebellar vermis in association with a posterior fossa cyst (arrow) and splaying of the cerebellar hemispheres. Image courtesy of Ecker et al.

Media file 13: An antenatal sonogram that shows Dandy-Walker malformation (arrow) in a fetus (same patient as in Image 14 in Multimedia Section). Courtesy of Umit Aksoy, MD, Uludag University, Bursa, Turkey.

Media file 14: An antenatal MRI showing Dandy-Walker malformation in a fetus (same patient as in Image 13 in Multimedia Section). Courtesy of Umit Aksoy, MD, Uludag University, Bursa, Turkey.

Media file 15: A CT scan depicting Dandy-Walker malformation.

Media file 16: An axial CT scan showing the sinus confluence (large arrow) and sinus transversus (small arrows) displaced superiorly in Dandy-Walker malformation (lambdoid-torcular inversion).

References

1. Murray JC, Johnson JA, Bird TD. Dandy-Walker malformation: etiologic heterogeneity and empiric recurrence risks. Clin Genet. Oct 1985;28(4):272-83. [Medline].

2. Richter EO, Pincus DW. Development of syringohydromyelia associated with Dandy-Walker malformation: treatment with cystoperitoneal shunt placement. Case report. J Neurosurg. Mar 2006;104(3 Suppl):206-9. [Medline].

3. Cakmak A, Zeyrek D, Cekin A, Karazeybek H. Dandy-Walker syndrome together with occipital encephalocele. Minerva Pediatr. Aug 2008;60(4):465-8. [Medline].

4. Dandy WE, Blackfan KD. Internal hydrocephalus: an experimental, clinical and pathological study. Am J Dis Child. 1914;8:406-82.

5. BENDA CE. The Dandy-Walker syndrome or the so-called atresia of the foramen Magendie. J Neuropathol Exp Neurol. Jan 1954;13(1):14-29. [Medline].

6. D'AGOSTINO AN, KERNOHAN JW, BROWN JR. THE DANDY-WALKER SYNDROME. J Neuropathol Exp Neurol. Jul 1963;22:450-70. [Medline].

7. Hart MN, Malamud N, Ellis WG. The Dandy-Walker syndrome. A clinicopathological study based on 28 cases. Neurology. Aug 1972;22(8):771-80. [Medline].

8. Altman NR, Naidich TP, Braffman BH. Posterior fossa malformations. AJNR Am J Neuroradiol. Mar-Apr 1992;13(2):691-724. [Medline].

9. Barkovich AJ, Kjos BO, Norman D, Edwards MS. Revised classification of posterior fossa cysts and cystlike malformations based on the results of multiplanar MR imaging. AJR Am J Roentgenol. Dec 1989;153(6):1289-300. [Medline].

10. Sasaki-Adams D, Elbabaa SK, Jewells V, Carter L, Campbell JW, Ritter AM. The Dandy-Walker variant: a case series of 24 pediatric patients and evaluation of associated anomalies, incidence of hydrocephalus, and developmental outcomes. J Neurosurg Pediatrics. Sep 2008;2(3):194-9. [Medline].

11. Strand RD, Barnes PD, Poussaint TY, Estroff JA, Burrows PE. Cystic retrocerebellar malformations: unification of the Dandy-Walker complex and the Blake's pouch cyst. Pediatr Radiol. 1993;23(4):258-60. [Medline].

12. Salihu HM, Kornosky JL, Alio AP, Druschel CM. Racial disparities in mortality among infants with Dandy-Walker syndrome. J Natl Med Assoc. May 2009;101(5):456-61. [Medline].

13. Salihu HM, Kornosky JL, Druschel CM. Dandy-Walker syndrome, associated anomalies and survival through infancy: a population-based study. Fetal Diagn Ther. 2008;24(2):155-60. [Medline].

14. Raybaud C. Cystic malformations of the posterior fossa. Abnormalities associated with the development of the roof of the fourth ventricle and adjacent meningeal structures. J Neuroradiol. 1982;9(2):103-33. [Medline].

15. Taggart JK, Walker AE. Congenital atresia of the foramens of Luschka and Magendie. Arch Neurol Psychiat. 1942;48:583-612.

16. Bordarier C, Aicardi J. Dandy-Walker syndrome and agenesis of the cerebellar vermis: diagnostic problems and genetic counselling. Dev Med Child Neurol. Apr 1990;32(4):285-94. [Medline].

17. Cavalcanti DP, Salomao MA. Dandy-Walker malformation with postaxial polydactyly: further evidence for autosomal recessive inheritance. Am J Med Genet. Jul 16 1999;85(2):183-4. [Medline].

18. Ulm B, Ulm MR, Deutinger J, Bernaschek G. Isolated Dandy-Walker malformation: prenatal diagnosis in two consecutive pregnancies. Am J Perinatol. 1999;16(2):61-3. [Medline].

19. Lavanya T, Cohen M, Gandhi SV, Farrell T, Whitby EH. A case of a Dandy-Walker variant: the importance of a multidisciplinary team approach using complementary techniques to obtain accurate diagnostic information. Br J Radiol. Oct 2008;81(970):e242-5. [Medline].

20. Kalidasan V, Carroll T, Allcutt D, Fitzgerald RJ. The Dandy-Walker syndrome--a 10-year experience of its management and outcome. Eur J Pediatr Surg. Dec 1995;5 Suppl 1:16-8. [Medline].

21. Phillips JJ, Mahony BS, Siebert JR, Lalani T, Fligner CL, Kapur RP. Dandy-Walker malformation complex: correlation between ultrasonographic diagnosis and postmortem neuropathology. Obstet Gynecol. Mar 2006;107(3):685-93. [Medline].

22. Menon RK, Nadkarni TD, Desai KI, Goel A. Dandy-Walker malformation associated with polycystic kidneys: Goldston syndrome revisited. J Clin Neurosci. Oct 2006;13(8):875-7. [Medline].

23. Sato K, Kubota T, Nakamura Y. Adult onset of the Dandy-Walker syndrome. Br J Neurosurg. Feb 1996;10(1):109-12. [Medline].

24. McClelland S 3rd, Charnas LR, SantaCruz KS, Garner HP, Lam CH. Progressive brainstem compression in an infant with neurocutaneous melanosis and Dandy-Walker complex following ventriculoperitoneal shunt placement for hydrocephalus. Case report. J Neurosurg. Dec 2007;107(6 Suppl):500-3. [Medline].

25. Ecker JL, Shipp TD, Bromley B, Benacerraf B. The sonographic diagnosis of Dandy-Walker and Dandy-Walker variant: associated findings and outcomes. Prenat Diagn. Apr 2000;20(4):328-32. [Medline].

26. Marnet D, Vinchon M, Mostofi K, Catteau B, Kerdraon O, Dhellemmes P. Neurocutaneous melanosis and the Dandy-Walker complex: an uncommon but not so insignificant association. Childs Nerv Syst. Aug 27 2009;[Medline].

27. Hadzagic-Catibusic F, Maksic H, Uzicanin S, Heljic S, Zubcevic S, Merhemic Z, et al. Congenital malformations of the central nervous system: clinical approach. Bosn J Basic Med Sci. Nov 2008;8(4):356-60. [Medline].

28. Kölble N, Wisser J, Kurmanavicius J, Bolthauser E, Stallmach T, Huch A, et al. Dandy-walker malformation: prenatal diagnosis and outcome. Prenat Diagn. Apr 2000;20(4):318-27. [Medline].

29. Yildiz H, Yazici Z, Hakyemez B, Erdogan C, Parlak M. Evaluation of CSF flow patterns of posterior fossa cystic malformations using CSF flow MR imaging. Neuroradiology. Sep 2006;48(9):595-605. [Medline].

30. Bromley B, Nadel AS, Pauker S, Estroff JA, Benacerraf BR. Closure of the cerebellar vermis: evaluation with second trimester US. Radiology. Dec 1994;193(3):761-3. [Medline].

31. Hata T, Yanagihara T, Matsumoto M, Hanaoka U, Ueta M, Tanaka Y, et al. Three-dimensional sonographic features of fetal central nervous system anomaly. Acta Obstet Gynecol Scand. Aug 2000;79(8):635-9. [Medline].

32. Russ PD, Pretorius DH, Johnson MJ. Dandy-Walker syndrome: a review of fifteen cases evaluated by prenatal sonography. Am J Obstet Gynecol. Aug 1989;161(2):401-6. [Medline].

33. Wolpert SM, Haller JS, Rabe EF. The value of angiography in the Dandy-Walker syndrome and posterior fossa extra-axial cysts. Am J Roentgenol Radium Ther Nucl Med. Jun 1970;109(2):261-72. [Medline].

34. Cedzich C, Lunkenheimer A, Baier G, Müller J, Kühner A. Ultrasound-guided puncture of a Dandy-Walker cyst via the lateral and III ventricles. Childs Nerv Syst. Sep 1999;15(9):472-6. [Medline].

Keywords

Dandy-Walker malformation, Dandy-Walker, Dandy-Walker syndrome, Dandy-Walker cyst, Dandy-Walker deformity, Dandy Walker, cerebellum, cerebellar disease, brain disease, central nervous system disease, Luschka-Magendie foramina atresia

Contributor Information and Disclosures

Author

Lutfi Incesu, MD, Professor, Department of Radiology, Ondokuz Mayis University School of Medicine; Chief, Neuroradiology and MR Unit, Department of Radiology, Ondokuz Mayis University Hospital, Turkey
Lutfi Incesu, MD is a member of the following medical societies: American Society of Neuroradiology and Radiological Society of North America
Disclosure: Nothing to disclose.

Coauthor(s)

Anil Khosla, MBBS, Assistant Professor, Department of Radiology, Section of Neuroradiology, Mallinckrodt Institute of Radiology, Washington University School of Medicine, Veterans Affairs Medical Center of St Louis
Anil Khosla, MBBS is a member of the following medical societies: American College of Radiology, American Roentgen Ray Society, American Society of Neuroradiology, North American Spine Society, and Radiological Society of North America
Disclosure: Nothing to disclose.

Medical Editor

Charles M Glasier, MD, Professor, Departments of Radiology and Pediatrics, University of Arkansas for Medical Sciences; Chief, Magnetic Resonance Imaging, Vice-Chief, Pediatric Radiology, Arkansas Children's Hospital
Charles M Glasier, MD is a member of the following medical societies: American College of Radiology, American Society of Neuroradiology, Radiological Society of North America, and Society for Pediatric Radiology
Disclosure: Nothing to disclose.

Pharmacy Editor

Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand
Disclosure: Nothing to disclose.

Managing Editor

Marta Hernanz-Schulman, MD, FAAP, Professor, Radiology, Radiological Sciences, and Pediatrics, Director, Department of Pediatric Radiology, Radiologist-in-Chief, Director, Department of Diagnostic Imaging, Vanderbilt University Medical Center, Vanderbilt Children's Hospital
Marta Hernanz-Schulman, MD, FAAP is a member of the following medical societies: American Institute of Ultrasound in Medicine and American Roentgen Ray Society
Disclosure: Nothing to disclose.

CME Editor

Robert M Krasny, MD, Resolution Imaging Medical Corporation
Robert M Krasny, MD is a member of the following medical societies: American Roentgen Ray Society and Radiological Society of North America
Disclosure: Nothing to disclose.

Chief Editor

James G Smirniotopoulos, MD, Professor of Radiology, Neurology, and Biomedical Informatics, Chairman, Department of Radiology and Radiological Sciences, Uniformed Services University of the Health Sciences
James G Smirniotopoulos, MD is a member of the following medical societies: American College of Radiology, American Roentgen Ray Society, American Society of Head and Neck Radiology, American Society of Neuroradiology, American Society of Pediatric Neuroradiology, Association of University Radiologists, and Radiological Society of North America
Disclosure: Nothing to disclose.

Related eMedicine topics

Arteriovenous Malformations

Atrioventricular Septal Defect, Complete

Management of Spina Bifida, Hydrocephalus and Shunts

Arachnoid Cyst

Ataxia with Identified Genetic and Biochemical Defects

Corpus Callosum, Agenesis


Clinical guidelines

ACR Appropriateness Criteria® ataxia. American College of Radiology - Medical Specialty Society. 1999 (revised 2006). 10 pages. NGC:005547


Clinical trials

Brain Development Research Program

© 1994- by Medscape.
All Rights Reserved
(http://www.medscape.com/public/copyright)