Skip to content
How It Works
Explore
Resources Ask a Question
Who It's For
Patients Caregivers Providers
Log In Ask a Question
PubMed This is a summary of 32 peer-reviewed journal articles Updated
Neurology · Joubert Syndrome and Dandy-Walker Malformation

Joubert Syndrome vs Dandy-Walker: What is the Difference?

At a Glance

Joubert syndrome and Dandy-Walker malformation both cause an underdeveloped cerebellum and look similar on early ultrasounds. However, fetal MRI shows Joubert features the "molar tooth sign," as it is a systemic genetic condition. Dandy-Walker is primarily a localized structural brain anomaly.

In this answer

6 sections

01

Why They Are Confused on Early Ultrasounds

02

The MRI Difference: The Molar Tooth Sign

03

Different Biological Roots

04

Developmental Expectations: A Wide Spectrum

05

Why Screening Needs Differ

06

Next Steps and Genetic Counseling

Being caught in a diagnostic gray area during pregnancy is incredibly terrifying, especially when doctors are shifting their opinions about your baby’s brain development.

While Joubert syndrome (JS) and Dandy-Walker malformation (DWM) both involve an underdeveloped cerebellum, they are fundamentally distinct conditions [1][2]. Early in pregnancy, both can look identical on a fetal ultrasound because they create a similar-looking fluid-filled space in the lower back of the brain [3][4]. However, as the brain continues to develop, a fetal MRI will reveal very different structural shapes [5]. Biologically, Joubert syndrome is a condition affecting the cells’ microscopic antennae (cilia) throughout the entire body, whereas Dandy-Walker malformation is primarily a structural brain anomaly [1][6]. Because Joubert syndrome affects cellular function system-wide, the developmental expectations and need for ongoing multi-organ screening are vastly different [7][8].

Why They Are Confused on Early Ultrasounds

Misdiagnosis is common early in pregnancy. The cerebellar vermis (the middle part of the cerebellum that controls balance and coordination) does not fully finish developing until later in the second trimester [9][4].

Because of this natural physiological delay, if the vermis is underdeveloped (hypoplasia), it leaves an “empty” space that fills with fluid. On an early 2D ultrasound, the fluid-filled spaces of both Joubert syndrome and Dandy-Walker malformation look remarkably similar [3][4]. Parents often receive a preliminary DWM diagnosis because it is a more commonly known structural anomaly, only to have the diagnosis shift to Joubert syndrome later when the brain structures are more clearly visible [9].

The MRI Difference: The Molar Tooth Sign

A fetal MRI provides a much clearer picture of the mid-hindbrain structures than a standard ultrasound, allowing doctors to firmly distinguish between the two conditions [10][11].

  • Joubert Syndrome: The hallmark of Joubert syndrome is the molar tooth sign (MTS) [12][2]. This is a distinct shape seen on an MRI cross-section of the brain. It happens because the “stems” that connect the cerebellum to the brainstem (superior cerebellar peduncles) grow abnormally thick and elongate horizontally, while the missing vermis prevents the brain from closing normally in the middle [13][14]. The result looks exactly like the root of a molar tooth [15].
  • Dandy-Walker Malformation: DWM does not have the molar tooth sign [16][17]. Instead, its classic presentation includes a massive cystic expansion of the fourth ventricle (a fluid-filled cavity), an abnormally enlarged posterior fossa (the space at the lower back of the skull), and a cerebellar vermis that is pushed upward and rotated [18][2].

Different Biological Roots

At a microscopic level, these conditions operate differently:

  • Joubert Syndrome is a Ciliopathy: It is caused by genetic mutations that impair primary cilia, which are tiny, hair-like structures on the surface of cells [19][6]. Cilia act like cellular antennae, sending and receiving crucial developmental signals [7][6]. Without working cilia, the brain—and other organs—cannot build themselves properly [20].
  • Dandy-Walker is a Structural Malformation: DWM is typically a localized developmental malformation of the back of the skull [12][21]. While it can involve different genetic or environmental factors, it does not typically stem from a systemic failure of cellular cilia [6][22].

Developmental Expectations: A Wide Spectrum

A common fear is what this means for a child’s daily life. It is crucial to know that both conditions exist on a very wide clinical spectrum [23][24].

For Joubert syndrome, almost all children experience hypotonia (low muscle tone) and ataxia (wobbly, uncoordinated movements), which leads to delayed motor milestones like independent walking [25][26]. However, not every child experiences severe intellectual disability. Roughly one-quarter of children with Joubert syndrome have borderline to normal cognitive function [27][23]. Early physical, occupational, and speech therapy can drastically improve functional independence [25][28]. Dandy-Walker malformation also presents on a spectrum, with developmental outcomes largely depending on whether other brain structures are involved [24].

Why Screening Needs Differ

Because primary cilia exist on almost every cell in the body, the genetic mutations that cause Joubert syndrome carry a risk of affecting other organs over time, making proactive monitoring essential [7][29]. While many children do not experience every complication, a child with JS must be regularly monitored for:

  • Kidney Issues: Risk of developing progressive cystic kidney disease [8][29].
  • Eye Problems: Risk of retinal dystrophy, which can impact vision [7][30].
  • Liver Disease: Risk of hepatic fibrosis, which causes scarring of the liver [31][29].

Dandy-Walker malformation is largely a structural brain issue, so care focuses heavily on managing neurological symptoms and hydrocephalus (fluid buildup in the brain) [18][32]. DWM can be syndromic and co-occur with other congenital issues (such as heart defects), so structural screenings remain important, but it does not carry the exact same multi-organ risk profile seen in a ciliopathy [7][32].

Next Steps and Genetic Counseling

Getting an accurate diagnosis is critical for building the right care team [16]. Because Joubert syndrome is usually passed down when both parents carry a recessive gene mutation, and DWM can sometimes be associated with chromosomal abnormalities, consulting a genetic counselor is a vital next step [19]. They can help coordinate specific genetic testing (like a ciliopathy panel) to bring clarity to the diagnosis and guide your family’s next steps.

At a Glance: Joubert vs. Dandy-Walker

Feature Joubert Syndrome (JS) Dandy-Walker Malformation (DWM)
Brain Imaging Hallmark Molar Tooth Sign (MTS) Enlarged posterior fossa & 4th ventricle cyst
Underlying Biology Ciliopathy (affects cellular antennae system-wide) Structural anomaly (often localized)
Primary Systemic Risks Kidneys, eyes, liver Associated structural defects (e.g., cardiac)
Ongoing Screening Routine renal, retinal, and hepatic panels Neurological monitoring (hydrocephalus)

Common questions in this guide

Why do Joubert syndrome and Dandy-Walker malformation look similar on early ultrasounds?
Early in pregnancy, the middle portion of the cerebellum is still developing. In both conditions, an underdevelopment in this area leaves a fluid-filled space that looks remarkably similar on a standard 2D fetal ultrasound, frequently leading to preliminary misdiagnoses.
How does a fetal MRI tell Joubert syndrome and Dandy-Walker apart?
A fetal MRI provides highly detailed images of the brain's mid-hindbrain structures. Joubert syndrome uniquely shows the "molar tooth sign," whereas Dandy-Walker malformation presents with an enlarged posterior fossa and a massive cyst in the fourth ventricle.
What is the biological difference between Joubert syndrome and Dandy-Walker malformation?
Joubert syndrome is a systemic genetic ciliopathy, meaning it affects the microscopic antennae on cells throughout the entire body. Dandy-Walker is typically a localized structural malformation of the skull and brain that does not stem from a system-wide cellular failure.
What ongoing health screenings are needed for a child with Joubert syndrome?
Because Joubert syndrome affects cells system-wide, children require proactive, routine monitoring for progressive cystic kidney disease, liver scarring (hepatic fibrosis), and vision issues like retinal dystrophy.
Will my child be able to walk if they have Joubert syndrome?
Most children with Joubert syndrome experience low muscle tone and coordination challenges that delay motor milestones like walking. However, early physical, occupational, and speech therapies can significantly improve functional independence over time.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Am I far enough along in my pregnancy for a fetal MRI to clearly show whether the 'molar tooth sign' or an enlarged posterior fossa is present?
  2. 2.Should we consider an amniocentesis for targeted genetic testing, and can we consult with a genetic counselor to discuss a ciliopathy panel versus standard chromosomal testing?
  3. 3.If the diagnosis is confirmed as Joubert syndrome, what early baselines should we establish with pediatric specialists for kidney, liver, and eye health after birth?
  4. 4.Given the current imaging, how severe does the cerebellar hypoplasia appear, and what specific challenges might that pose for our baby's early motor development?
  5. 5.If we are dealing with Dandy-Walker malformation, does the imaging show any signs of fluid buildup (hydrocephalus) or other structural anomalies like heart defects?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

Related questions

Does Joubert Syndrome Cause Blindness or Vision Loss?Does Joubert Syndrome Cause Extra Fingers or Toes?Does Joubert Syndrome Cause Hormone Problems?How Often Should Joubert Syndrome Patients Be Screened?Is COACH Syndrome the Same as Joubert Syndrome?Is General Anesthesia Safe for Joubert Syndrome?What Is a Ciliopathy & How Does It Cause Joubert Syndrome?Chance of Having Another Child with Joubert SyndromeWhat are Joubert Syndrome Related Disorders?What is the Life Expectancy for Joubert Syndrome?What is the Molar Tooth Sign in Joubert Syndrome?When Do Children With Joubert Syndrome Walk and Talk?Why Do Babies With Joubert Syndrome Breathe Abnormally?Joubert Syndrome: Why Get Genetic Testing After MRI?

References

References (32)
  1. 1

    Genetics Review: Joubert Syndrome.

    Tran AM, Jnah AJ, De Castro Pretelt MJ

    Neonatal network : NN 2025; (44(3)):159-166 doi:10.1891/NN-2024-0052.

    PMID: 40537162
  2. 2

    Whole exome sequencing reveals novel CEP104 mutations in a Chinese patient with Joubert syndrome.

    Luo M, Cao L, Cao Z, et al.

    Molecular genetics & genomic medicine 2019; (7(12)):e1004 doi:10.1002/mgg3.1004.

    PMID: 31625690
  3. 3

    Hindbrain morphometry and choroid plexus position in differential diagnosis of posterior fossa cystic malformations.

    Paladini D, Donarini G, Parodi S, et al.

    Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology 2019; (54(2)):207-214 doi:10.1002/uog.20120.

    PMID: 30207001
  4. 4

    Delayed rotation of the cerebellar vermis: a pitfall in early second-trimester fetal magnetic resonance imaging.

    Pinto J, Paladini D, Severino M, et al.

    Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology 2016; (48(1)):121-124 doi:10.1002/uog.15782.

    PMID: 26482947
  5. 5

    Case report and a brief review: Analysis and challenges of prenatal imaging phenotypes and genotypes in Joubert syndrome.

    Huang LX, Lu XG, Liu JX, et al.

    Frontiers in genetics 2022; (13()):1038274 doi:10.3389/fgene.2022.1038274.

    PMID: 36468023
  6. 6

    Ahi1 promotes Arl13b ciliary recruitment, regulates Arl13b stability and is required for normal cell migration.

    Muñoz-Estrada J, Ferland RJ

    Journal of cell science 2019; (132(17)) doi:10.1242/jcs.230680.

    PMID: 31391239
  7. 7

    Phenotypic variability in Joubert syndrome is partially explained by ciliary pathophysiology.

    Owens JW, Hopkin RJ, Martin LJ, et al.

    Annals of human genetics 2024; (88(1)):86-100 doi:10.1111/ahg.12537.

    PMID: 37921557
  8. 8

    Case Report: Identification of likely recurrent CEP290 mutation in a child with Joubert syndrome and cerebello-retinal-renal features.

    Spahiu L, Sayer JA, Behluli E, et al.

    F1000Research 2022; (11()):388 doi:10.12688/f1000research.109628.2.

    PMID: 37224330
  9. 9

    Joubert syndrome a rare entity and role of radiology: A case report.

    Ullah I, Khan KS, Afridi RU, et al.

    Annals of medicine and surgery (2012) 2022; (79()):104113 doi:10.1016/j.amsu.2022.104113.

    PMID: 35860112
  10. 10

    Prenatal Diagnosis of Poretti-Boltshauser Syndrome - a Case Report of a Molar Tooth Sign Mimic.

    Pereira-Macedo M, Grangeia A, Braga AC, et al.

    Cerebellum (London, England) 2024; (23(6)):2646-2649 doi:10.1007/s12311-024-01728-4.

    PMID: 39133430
  11. 11

    Prenatal diagnosis of Joubert syndrome by ultrasound and magnetic resonance imaging - report of three cases.

    Yu X, Zhen Z, Li J, et al.

    Taiwanese journal of obstetrics & gynecology 2017; (56(3)):408-409 doi:10.1016/j.tjog.2017.04.028.

    PMID: 28600062
  12. 12

    Analysis of CT and MRI Manifestations of Joubert Syndrome.

    Liao DW, Zheng X

    Journal of the Belgian Society of Radiology 2023; (107(1)):78 doi:10.5334/jbsr.3283.

    PMID: 37781478
  13. 13

    Neuroimaging Characteristics as Diagnostic Tools in Joubert Syndrome and Related Disorders: A Case Report and Literature Review.

    Alhashimi I, Zoghoul S, Khalil SK, et al.

    Cureus 2024; (16(9)):e69872 doi:10.7759/cureus.69872.

    PMID: 39435230
  14. 14

    An unusual association of classical Joubert syndrome with retrocerebellar arachnoid cyst.

    Baldawa S

    Child's nervous system : ChNS : official journal of the International Society for Pediatric Neurosurgery 2016; (32(7)):1181-2 doi:10.1007/s00381-016-3099-x.

    PMID: 27138555
  15. 15

    Late-onset hydrocephalus in a child with Joubert syndrome: a case report.

    Fehrenbach MK, Nestler U, Meixensberger J, et al.

    Child's nervous system : ChNS : official journal of the International Society for Pediatric Neurosurgery 2018; (34(7)):1423-1425 doi:10.1007/s00381-018-3767-0.

    PMID: 29508057
  16. 16

    Joubert Plus syndrome in a child with Dandy-Walker malformation and occipital cephalocele: A case report.

    Mehari TH, Tessema BM, Gebrekidan RG

    Radiology case reports 2025; (20(9)):4701-4705 doi:10.1016/j.radcr.2025.05.103.

    PMID: 40677886
  17. 17

    Prenatal diagnosis of Joubert syndrome: A case report and literature review.

    Zhu L, Xie L

    Medicine 2017; (96(51)):e8626 doi:10.1097/MD.0000000000008626.

    PMID: 29390414
  18. 18

    Refining the Neuroimaging Definition of the Dandy-Walker Phenotype.

    Whitehead MT, Barkovich MJ, Sidpra J, et al.

    AJNR. American journal of neuroradiology 2022; (43(10)):1488-1493 doi:10.3174/ajnr.A7659.

    PMID: 36137655
  19. 19

    Clinical and genetic spectrum from a prototype of ciliopathy: Joubert syndrome.

    Aksu Uzunhan T, Ertürk B, Aydın K, et al.

    Clinical neurology and neurosurgery 2023; (224()):107560 doi:10.1016/j.clineuro.2022.107560.

    PMID: 36580738
  20. 20

    Functional genome-wide siRNA screen identifies KIAA0586 as mutated in Joubert syndrome.

    Roosing S, Hofree M, Kim S, et al.

    eLife 2015; (4()):e06602 doi:10.7554/eLife.06602.

    PMID: 26026149
  21. 21

    Non-classic splicing mutation in the CPLANE1 (C5orf42) gene cause Joubert syndrome in a fetus with severe craniocerebral dysplasia.

    Zhu H, Chen W, Ren H, et al.

    European journal of medical genetics 2021; (64(6)):104212 doi:10.1016/j.ejmg.2021.104212.

    PMID: 33794348
  22. 22

    AN UNUSUAL PRESENTATION OF JOUBERT SYNDROME AND RELATED DISORDERS IN A NEWBORN: PANHYPOPITUITARISM.

    Erol S, Demirel N, Bas AY, et al.

    Genetic counseling (Geneva, Switzerland) 2016; (27(3)):367-371.

    PMID: 30204965
  23. 23

    Joubert Syndrome with Orofacial Digital Features.

    Bhardwaj P, Sharma M, Ahluwalia K

    Journal of neurosciences in rural practice 2018; (9(1)):152-154 doi:10.4103/jnrp.jnrp_338_17.

    PMID: 29456362
  24. 24

    Joubert syndrome: neuroimaging findings in 110 patients in correlation with cognitive function and genetic cause.

    Poretti A, Snow J, Summers AC, et al.

    Journal of medical genetics 2017; (54(8)):521-529 doi:10.1136/jmedgenet-2016-104425.

    PMID: 28087721
  25. 25

    Joubert Syndrome in Children-A Comprehensive Analysis of Quality of Life, Functional Independence and Family Impact.

    Elmaoğlu E, Coşkun AB, Usgu S, et al.

    American journal of medical genetics. Part A 2025; (197(12)):e64213 doi:10.1002/ajmg.a.64213.

    PMID: 40750754
  26. 26

    Ophthalmic, Neurological, Radiological, and Visual Rehabilitation Profile and Outcomes in a Cohort of Patients with Joubert Syndrome.

    Bhate M, Bansal Bhandari S, Jayaraman D, et al.

    Neuro-ophthalmology (Aeolus Press) 2025; (49(3)):249-254 doi:10.1080/01658107.2025.2460176.

    PMID: 40190368
  27. 27

    Whole exome sequencing identified a novel missense alteration in CC2D2A causing Joubert syndrome 9 in a Pakhtun family.

    Khan MI, Latif M, Saif M, et al.

    The journal of gene medicine 2021; (23(1)):e3279 doi:10.1002/jgm.3279.

    PMID: 32989887
  28. 28

    Rehabilitation Approach for Children With Joubert Syndrome and Related Disorders.

    Mano H, Kitamura K, Tachibana M, et al.

    Cureus 2023; (15(5)):e38658 doi:10.7759/cureus.38658.

    PMID: 37288221
  29. 29

    Molar Tooth Sign with Deranged Liver Function Tests: An Indian Case with COACH Syndrome.

    Sanjeev RK, Kapoor S, Goyal M, et al.

    Case reports in pediatrics 2015; (2015()):385910 doi:10.1155/2015/385910.

    PMID: 26075130
  30. 30

    A Case of Joubert Syndrome with Chronic Kidney Disease.

    Shamsudheen MP, Das U, Taduri G, et al.

    Indian journal of nephrology 2021; (31(1)):61-63 doi:10.4103/ijn.IJN_287_19.

    PMID: 33994691
  31. 31

    Any modality of renal replacement therapy can be a treatment option for Joubert syndrome.

    Takagi Y, Miura K, Yabuuchi T, et al.

    Scientific reports 2021; (11(1)):462 doi:10.1038/s41598-020-80712-4.

    PMID: 33432080
  32. 32

    [Clinical and genetic analysis of a family with Joubert syndrome type 10 caused by OFD1 gene mutation].

    Meng C, Zhang KH, Ma J, et al.

    Zhonghua er ke za zhi = Chinese journal of pediatrics 2017; (55(2)):131-134 doi:10.3760/cma.j.issn.0578-1310.2017.02.015.

    PMID: 28173652

This page explains the differences between Joubert syndrome and Dandy-Walker malformation for educational purposes only. Always consult your maternal-fetal medicine specialist or pediatric neurologist for a definitive diagnosis and care plan.

Get notified when new evidence is published on Joubert syndrome and related disorders.

We monitor PubMed for new peer-reviewed studies on this topic and email a short summary when something meaningful changes.