What is Dandy-Walker Malformation?

Dandy-Walker malformation, also known as DWM, is a rare brain condition. The condition is characterized by underdevelopment or absence of a part of the brain called the vermis, enlargement of the brain’s fourth ventricle connected to a large brain cyst, a displacement of certain brain structures, and an enlargement of the back part of the skull. The first time DWM was described was in 1887, with the name “Dandy-Walker” given in 1954.

Medical experts often use the terms “Dandy-Walker complex” and “Dandy-Walker spectrum” to describe this condition. It’s worth noting that many people diagnosed with DWM also have a condition known as hydrocephalus, which is the buildup of too much cerebrospinal fluid in the brain. DWM is the most common brain malformation at the back of the skull.

Within the range of DWM, there are three categories, which are: Dandy-Walker malformation, Dandy-Walker variant, and simple posterior fossa cistern widening. Dandy-Walker variant is characterized by underdevelopment of the vermis, enlargement of the fourth brain ventricle, and normal size of the back part of the skull. However, medical professionals are moving away from these specific categorizations as they can be confusing. Instead, they opt to describe the individual abnormalities in each case.

While many people with DWM don’t experience symptoms for several years, others may have various health issues which lead to an earlier diagnosis. The primary focus of treatment is often to relieve symptoms of hydrocephalus and other effects related to the back part of the skull, often including surgical procedures much like ventriculoperitoneal and cystoperitoneal shunting.

What Causes Dandy-Walker Malformation?

In the past, DWM, a brain malformation, was thought to be caused by the closing of specific passages in the brain’s fourth ventricle, leading to its enlargement and underdevelopment of a brain part called the vermis. However, recent studies point out that DWM is actually a result of issues during the development of the rhombencephalon, another part of the brain. this leads to variances in the underdevelopment of the vermis and enlargement of certain cysts. There seem to be two main ways this brain malformation starts: the halt in the development of the vermis and issues with the openings in the fourth ventricle, which lead to an enlarged structure called Blake’s pouch that puts pressure on the vermis.

DWM could occur alone or be tied to genetic abnormalities, conditions passed down through families, syndromes, infections present at birth, and various other health conditions. Brain disorders related to DWM include malformations in the cortical part of the brain, holoprosencephaly, abnormalities in the development of the corpus callosum, and issues with neural tube development.

Rare mutations in certain genes like FOXC1 (found in locus 6p25.3), ZIC1, and ZIC4 (found in locus 3q24), FGF17, LAMC1, and NID1 have been reported in some cases.

Risk Factors and Frequency for Dandy-Walker Malformation

Dandy-Walker Malformation (DWM) and its related conditions occur in about 1 in 350,000 live births in the US. These malformations make up around 1% to 4% of all cases of a condition called hydrocephalus. Most people with DWM show signs of increased pressure in the skull, often due to hydrocephalus and a cyst in a part of the skull called the posterior fossa. The primary goal of treatment is usually to control this skull pressure, often through surgery.

  • Some medical centers report death rates between 12% and 50% associated with these malformations.
  • Treating hydrocephalus with a medical procedure called shunting can greatly improve survival rates.
  • The rate of deaths in the fetal stage directly links to the presence of abnormalities outside the central nervous system (CNS).

Signs and Symptoms of Dandy-Walker Malformation

Dandy-Walker Malformation (DWM) is a condition that affects the brain and can show up in different ways depending on the severity, the presence of hydrocephalus (water on the brain), and any other health issues the person may have. Most people with this condition start showing signs and symptoms during their first year of life. These signs and symptoms are usually related to increased pressure within the skull.

The most common symptom seen in 90% to 100% of patients is a larger than normal head size, which usually appears during the first few months of life. Some people with DWM might also have abnormalities in the heart, face, limbs, and digestive or reproductive systems, which might be the first thing that doctors notice.

Hydrocephalus is very common in patients with DWM; about 75% of cases will have this condition by the age of 3 months, and eventually, almost 90% of the patients will have it. A study that looked at 42 patients with DWM found that all of them had hydrocephalus at the time of diagnosis, 88% had a smaller than normal central part of the cerebellum (vermian hypoplasia), and 59% had a smaller than normal overall cerebellum (cerebellar hypoplasia).

Testing for Dandy-Walker Malformation

Ultrasound is commonly the first approach in checking a baby’s brain while in the womb. This process looks at several parts of the brain like the head shape, cerebellum, and spine. It can also help find if there are any abnormalities often linked with Dandy-Walker Malformation, a rare condition affecting the brain.

During the ultrasound, a part of the brain known as the cisterna magna is measured. Previous studies have shown that if it’s noticed to be larger than normal, it may suggest the baby may have certain brain abnormalities. However, if no other irregularities are found, a larger cisterna magna is generally not a cause for concern.

For diagnosing Dandy-Walker Malformation, there’s a set of criteria known by radiologists. This involves identifying specific changes in the brain’s structure such as a large cyst in the back of the brain or the absence or reduction of certain parts of the brain.

In addition to ultrasound, Magnetic Resonance Imaging (MRI), which is a type of scan, can provide a clearer picture of the baby’s brain after the 20th week of pregnancy. It can help find and describe any brain malformations not clearly seen by the ultrasound. An ultrasound can potentially detect Dandy-Walker Malformation after the 18th week of pregnancy, but an MRI can confirm the diagnosis.

For patients suspected to have Dandy-Walker Malformation, both karyotyping (a test to look at the chromosomes) and postnatal imaging may be suggested. These help confirm findings and search for other possibly associated abnormalities.

Finally, measuring specific angles in the brain help distinguish between normal findings and signs of Dandy-Walker Malformation. Other potential abnormalities linked with Dandy-Walker Malformation include occipital encephalocele (a sac-like protrusion at the back of the skull), polymicrogyria (numerous small folds on the brain surface), and disorders affecting the corpus callosum, a part of the brain that connects the two halves.

Treatment Options for Dandy-Walker Malformation

Treatment primarily focuses on managing the symptoms and related health issues. Most patients display symptoms due to increased pressure inside the skull, mainly caused by excess water on the brain (hydrocephalus) and cysts in the back part of the skull. This is why the aim is generally to manage this internal pressure, and this is usually done through surgery.

There are different types of surgical treatments available. The patient may undergo a procedure to have a ventriculoperitoneal (VP) or cystoperitoneal (CP) shunt installed. These shunts help redirect the fluid from the brain to other parts of the body. Some patients might be suitable for less invasive procedures performed via an endoscope, such as an endoscopic third ventriculostomy (ETV), which creates a new pathway for the fluid to escape from the brain.

In diagnosing the Dandy-Walker malformation (DWM), it is important for doctors to also consider other conditions that may show similar symptoms. These include:

  • Conditions related to the brain’s back part such as arachnoid cysts which might cause dangerous brain pressure sometimes
  • Cystic hygroma, which is a large fluid-filled cyst
  • Blake’s pouch cyst, which is a build-up of excess fluid in the brain
  • Mega cisterna magna, where there’s an excessive accumulation of cerebrospinal fluid
  • Vermian hypoplasia, a condition where part of the brain’s cerebellum is underdeveloped

Moreover, in the diagnosis, they might also consider certain syndromes that are known to be associated with DWM. These include but are not limited to:

  • Aase-Smith syndrome
  • Cerebro-ocular muscular syndrome
  • Coffin-Siris syndrome
  • Cornelia de Lange syndrome
  • Aicardi syndrome

Other disorders needing ruling out are more complex brain malformation syndromes such as Joubert syndrome, tectocerebellar dysraphia and neocerebellar dysgenesis.

John Smine and Mike Harrison (text@company)))

What to expect with Dandy-Walker Malformation

The outcome for patients with DWM – a type of brain malformation – can be different from case to case, depending on several factors. These include how severe the malformation is, how quickly the condition is diagnosed and treated, and whether there are any complications connected with the condition. In cases where the cerebellum (part of the brain involved in coordinating movements) is less affected and there isn’t too much pressure within the skull, people could experience fewer neurological problems and can, with the right treatment and support, lead pretty normal lives. But if the case is more severe with bigger abnormalities in the cerebellum, patients have a greater risk of facing developmental delays, learning disabilities, coordination problems, and an accumulation of fluid in the brain known as hydrocephalus.

In severe situations, children with untreated hydrocephalus have a high risk of passing away early; half of them don’t live past the age of 3, and only around 20% to 23% manage to reach adulthood. The adults who do survive often have issues related to motor skills, vision, and hearing.

Another factor to note is the size of the fetal lateral ventricle – part of the brain – which can be measured using ultrasound during pregnancy. As per a previous study, a size between 11 mm to 15 mm carries a 21% risk of developmental delay. If the size is greater than 15 mm, that risk goes above 50%.

Another thing to consider is that in patients with non-tumor related hydrocephalus, the overall risk of epilepsy is roughly 30%. The functional outcome, or how the patient will be able to function on a daily basis, is influenced by several factors, such as any other abnormalities in the brain, any other symptoms outside the central nervous system, epilepsy, and other congenital or present-at-birth abnormalities.

Possible Complications When Diagnosed with Dandy-Walker Malformation

Dandy-Walker Malformation (DWM) can bring about a variety of neurological and developmental problems. The main complication is hydrocephalus, which causes an increase in pressure inside the skull. Symptoms such as headaches, vomiting, and hindrances in thinking and understanding (cognitive impairments) can arise from this pressure increase. Prompt treatment is critical because of these symptoms. Shunting, a common treatment, may have complications like infection or malfunction.

Patients with DWM might also struggle with motor and coordination problems due to abnormalities in the cerebellum, which can affect their daily life and well-being. Issues such as cognitive and intellectual disabilities, speech and language issues, behavioural concerns can be common, making this condition complex to manage. Also, the anomalies in body structure that come with DWM might lead to other complications, such as the risk of syringomyelia or abnormalities in the spinal cord.

  • Increased pressure inside the skull
  • Headaches
  • Vomiting
  • Cognitive impairments
  • Infections from shunting
  • Shunting malfunction
  • Motor and coordination problems
  • Cognitive and intellectual disabilities
  • Speech and language issues
  • Behavioural concerns
  • Syringomyelia or spinal cord abnormalities

There is a possibility of chromosomal abnormalities in 16 percent of DWM patients who have no other health issues. DWM can also be linked with abnormalities in the structure of the face, limbs, heart, and genitourinary or gastrointestinal systems.

Preventing Dandy-Walker Malformation

The development of a part of the brain called the cerebellar vermis varies between individuals and typically completes during the earlier part of pregnancy. In some cases, this development process might finish around the 18th week of pregnancy. Thus, using brain imaging to diagnose a condition known as Dandy-Walker Malformation (DWM) before 16 to 18 weeks may lead to premature or inaccurate results. It’s important to bear in mind that another brain structure, the cisterna magna, also hasn’t reached its final state during the first half of pregnancy. So, a wide opening in the brain’s cerebellomedullary cistern doesn’t necessarily indicate problems with the vermis at this stage. Hence, to ensure accuracy, doctors should recheck the cerebellum around weeks 20 to 22 of pregnancy for any abnormalities in the vermis.

It is advised to offer patients showing signs of Dandy-Walker complex a full fetal ultrasound and a karyotype test (a test that analyzes the structure and number of chromosomes in a cell).

Last but not least, if a patient’s cisterna magna (a normal part of the brain) appears larger than usual, but there are no other abnormal signs in the back of the brain, this shouldn’t be a cause for concern. In such instances, a larger cisterna magna might not hold any significant clinical implications.

Frequently asked questions

Dandy-Walker Malformation is a rare brain condition characterized by underdevelopment or absence of a part of the brain called the vermis, enlargement of the brain's fourth ventricle connected to a large brain cyst, a displacement of certain brain structures, and an enlargement of the back part of the skull.

Dandy-Walker Malformation (DWM) and its related conditions occur in about 1 in 350,000 live births in the US.

The signs and symptoms of Dandy-Walker Malformation (DWM) can vary depending on the severity of the condition, the presence of hydrocephalus (water on the brain), and any other health issues the person may have. However, most people with DWM start showing signs and symptoms during their first year of life, which are usually related to increased pressure within the skull. The most common symptom seen in 90% to 100% of patients is a larger than normal head size, which typically appears during the first few months of life. In addition to the enlarged head size, some people with DWM may also have abnormalities in other parts of their body, such as the heart, face, limbs, and digestive or reproductive systems. These abnormalities in other body parts may be the first thing that doctors notice when diagnosing DWM. It is also important to note that hydrocephalus is very common in patients with DWM, with about 75% of cases developing this condition by the age of 3 months. Eventually, almost 90% of patients with DWM will have hydrocephalus. A study that looked at 42 patients with DWM found that all of them had hydrocephalus at the time of diagnosis. Additionally, 88% of the patients had a smaller than normal central part of the cerebellum (vermian hypoplasia), and 59% had a smaller than normal overall cerebellum (cerebellar hypoplasia).

Dandy-Walker Malformation can occur due to issues during the development of the rhombencephalon, leading to underdevelopment of the vermis and enlargement of certain cysts. It can also be tied to genetic abnormalities, conditions passed down through families, syndromes, infections present at birth, and various other health conditions.

The other conditions that a doctor needs to rule out when diagnosing Dandy-Walker Malformation are: - Arachnoid cysts - Cystic hygroma - Blake's pouch cyst - Mega cisterna magna - Vermian hypoplasia - Aase-Smith syndrome - Cerebro-ocular muscular syndrome - Coffin-Siris syndrome - Cornelia de Lange syndrome - Aicardi syndrome - Joubert syndrome - Tectocerebellar dysraphia - Neocerebellar dysgenesis

The types of tests needed for Dandy-Walker Malformation include: - Ultrasound: This is commonly the first approach in checking a baby's brain while in the womb. It looks at several parts of the brain and can help find any abnormalities associated with Dandy-Walker Malformation. - Magnetic Resonance Imaging (MRI): This type of scan provides a clearer picture of the baby's brain and can help find and describe any brain malformations not clearly seen by ultrasound. - Karyotyping: This test looks at the chromosomes and can help confirm the diagnosis of Dandy-Walker Malformation. - Postnatal imaging: This is done after the baby is born and helps confirm findings and search for other associated abnormalities. - Measurement of specific angles in the brain: This helps distinguish between normal findings and signs of Dandy-Walker Malformation.

Dandy-Walker Malformation is primarily treated by managing the symptoms and related health issues. The main focus of treatment is to manage the increased pressure inside the skull, which is often caused by excess water on the brain and cysts in the back part of the skull. Surgery is usually the preferred method of treatment, and there are different types of surgical treatments available. These may include the installation of a ventriculoperitoneal (VP) or cystoperitoneal (CP) shunt to redirect the fluid from the brain to other parts of the body. In some cases, less invasive procedures performed via an endoscope, such as an endoscopic third ventriculostomy (ETV), may be suitable to create a new pathway for the fluid to escape from the brain.

The side effects when treating Dandy-Walker Malformation include: - Increased pressure inside the skull - Headaches - Vomiting - Cognitive impairments - Infections from shunting - Shunting malfunction - Motor and coordination problems - Cognitive and intellectual disabilities - Speech and language issues - Behavioural concerns - Syringomyelia or spinal cord abnormalities

The prognosis for Dandy-Walker Malformation can vary depending on the severity of the malformation, the timing of diagnosis and treatment, and the presence of complications. In cases where the malformation is less severe and there is not too much pressure within the skull, individuals may experience fewer neurological problems and can lead relatively normal lives with the right treatment and support. However, in more severe cases with larger abnormalities in the cerebellum, there is a greater risk of developmental delays, learning disabilities, coordination problems, and hydrocephalus.

A neurologist or a neurosurgeon.

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