The primary aim of this study was to estimate the incidence of posterior fossa anomalies (PFA) and assess the associated outcomes in King Abdulaziz Medical City (KAMC), Riyadh. All fetuses diagnosed by prenatal ultrasound with PFA from 2017 to 2021 in KAMC were analyzed retrospectively. PFA included Dandy-Walker malformation (DWM), mega cisterna magna (MCM), Blake\'s pouch cyst (BPC), and isolated vermian hypoplasia (VH). The 65 cases of PFA were 41.5% DWM, 46.2% MCM, 10.8% VH, and 1.5% BPC. The annual incidence rates were 2.48, 2.64, 4.41, 8.75, and 1.71 per 1000 anatomy scans for 2017, 2018, 2019, 2020, and 2021, respectively. Infants with DWM appeared to have a higher proportion of associated central nervous system (CNS) abnormalities (70.4% vs. 39.5%; p-value = 0.014) and seizures than others (45% vs. 17.9%; p-value = 0.041). Ten patients with abnormal genetic testing showed a single gene mutation causing CNS abnormalities, including a pathogenic variant in MPL, C5orf42, ISPD, PDHA1, PNPLA8, JAM3, COL18A1, and a variant of uncertain significance in the PNPLA8 gene. Our result showed that the most common PFA is DWM and MCM. The autosomal recessive pathogenic mutation is the major cause of genetic disease in Saudi patients diagnosed with PFA.

Dandy-Walker syndrome is a rare congenital central nervous system malformation. Dandy-Walker variant is characterised by cerebellar vermian hypoplasia, cystic fourth ventricular dilatation, and normal posterior fossa volume. Various prenatal tests such as ultrasound, fetal magnetic resonance imaging, and amniocentesis can help diagnose Dandy-Walker syndrome. Here, we report a case of the Dandy-Walker variant with meningitis in a neonate admitted to the neonatal intensive care unit due to multiple petechiae on the anterior abdominal wall, accompanied by peripheral cyanosis at the time of birth. Although maximum cases are diagnosed prenatally, some cases might be missed due to inadequate antenatal examination. Magnetic imaging resonance of the brain is best for the diagnosis of Dandy-Walker syndrome postnatally.
UNASSIGNED: case reports; Dandy-Walker malformation, magnetic resonance imaging, meningitis.

Dandy-Walker malformation or syndrome is a rare congenital deformity in which the cerebellar vermis is hypoplastic and upwardly rotated, the fourth ventricle enlarged, and the posterior fossa cystically dilated. It represents the most common type of posterior fossa malformations that are usually diagnosed before the age of one year old. We present a seven-year-old boy with a history of neonatal hypotonia and delayed walking, who presented with speech and language difficulties. His physical examination and cognitive tests were unremarkable. The patient\'s brain magnetic resonance imaging showed a partial defect of the inferior part of the cerebellar vermis and communication between a normal-sized cisterna magna and the fourth ventricle. There were no other coexisting central nervous system or systemic anomalies. This isolated inferior vermian hypoplasia was compatible with an uncommon variant of the Dandy-Walker syndrome. The aim of this report is to provide insight into the importance of implementing a pediatrician-psychiatrist collaboration in the clinical decision-making process of such developmental delay cases. What makes the present case further interesting are the new-onset unprovoked seizures that developed and recurred in the setting of such isolated and less severe posterior fossa anomaly, raising both diagnostic and therapeutic challenges.

Dandy-Walker Syndrome (DWS) is a rare congenital neurological condition characterized by cerebellar and posterior fossa malformations, often presenting a variable clinical spectrum. Common complications include hydrocephalus, necessitating interventions like ventriculoperitoneal (VP) shunts, and endoscopic third ventriculostomy (ETV). We describe the case of a five-month-old infant conceived through in vitro fertilization (IVF), initially presenting with cold-like symptoms, later diagnosed with DWS. The patient underwent VP shunt placement for hydrocephalus management, with subsequent complications requiring shunt revisions and ETV. Vigilant monitoring and timely interventions were crucial for a favorable outcome, highlighting the challenges in diagnosing and managing DWS and the importance of tailored treatment strategies.

Oculogastrointestinal neurodevelopmental syndrome has been described in seven previously published individuals who harbor biallelic pathogenic variants in the CAPN15 gene. Biallelic missense variants have been reported to demonstrate a phenotype of eye abnormalities and developmental delay, while biallelic loss of function variants exhibit phenotypes including microcephaly and craniofacial abnormalities, cardiac and genitourinary malformations, and abnormal neurologic activity. We report six individuals from three unrelated families harboring biallelic deleterious variants in CAPN15 with phenotypes overlapping those previously described for this disorder. Of the individuals affected, four demonstrate radiographic evidence of the classical triad of Dandy-Walker malformation including hypoplastic vermis, fourth ventricle enlargement, and torcular elevation. Cerebellar anomalies have not been previously reported in association with CAPN15-related disease. Here, we present three unrelated families with findings consistent with oculogastrointestinal neurodevelopmental syndrome and cerebellar pathology including Dandy-Walker malformation. To corroborate these novel clinical findings, we present supporting data from the mouse model suggesting an important role for this protein in normal cerebellar development. Our findings add six molecularly confirmed cases to the literature and additionally establish a new association of Dandy-Walker malformation with biallelic CAPN15 variants, thereby expanding the neurologic spectrum among patients affected by CAPN15-related disease.

Although cardinal imaging features for the diagnostic criteria of the Dandy-Walker phenotype have been recently defined, there is a large range of unreported malformations among these patients. The brainstem, in particular, deserves careful attention because malformations in this region have potentially important implications for clinical outcomes. In this article, we offer detailed information on the association of brainstem dysgenesis in a large, multicentric cohort of patients with the Dandy-Walker phenotype, defining different subtypes of involvement and their potential clinical impact.
In this established multicenter cohort of 329 patients with the Dandy-Walker phenotype, we include and retrospectively review the MR imaging studies and clinical records of 73 subjects with additional brainstem malformations. Detailed evaluation of the different patterns of brainstem involvement and their potential clinical implications, along with comparisons between posterior fossa measurements for the diagnosis of the Dandy-Walker phenotype, was performed among the different subgroups of patients with brainstem involvement.
There were 2 major forms of brainstem involvement in patients with Dandy-Walker phenotype including the following: 1) the mild form with anteroposterior disproportions of the brainstem structures \"only\" (57/73; 78%), most frequently with pontine hypoplasia (44/57; 77%), and 2) the severe form with patients with tegmental dysplasia with folding, bumps, and/or clefts (16/73; 22%). Patients with severe forms of brainstem malformation had significantly increased rates of massive ventriculomegaly, additional malformations involving the corpus callosum and gray matter, and interhemispheric cysts. Clinically, patients with the severe form had significantly increased rates of bulbar dysfunction, seizures, and mortality.
Additional brainstem malformations in patients with the Dandy-Walker phenotype can be divided into 2 major subgroups: mild and severe. The severe form, though less prevalent, has characteristic imaging features, including tegmental folding, bumps, and clefts, and is directly associated with a more severe clinical presentation and increased mortality.

G9a, also known as EHMT2, is essential for embryogenesis and has specific functions in multiple developmental processes. G9a inactivation affects development of the nervous system, which is formed with contribution of descendants of progenitor cells expressing the transcription factor Isl1. However, the function of G9a in Isl1-expressing progenitors is unknown. Here, we show that G9a is required for proper development of multiple structures formed with contribution of Isl1-expressing progenitors. A Cre-dependent GFP reporter revealed that the recombinase activity of the Isl1-Cre used in this study to inactivate G9a was reduced to a subset of Isl1-expressing progenitor cells. G9a mutants reached endpoint by 7 weeks of age with cardiac hypertrophy, hydrocephalus, underdeveloped cerebellum and hind limb paralysis, modeling aspects of Dandy-Walker complex. Moreover, neuroepithelium of the lateral ventricle derived from Isl1-expressing progenitors was thinner and disorganized, potentially compromising cerebrospinal fluid dynamics in G9a mutants. Micro-computed tomography after iodine staining revealed increased volume of the heart, eye lens and brain structures in G9a mutant fetuses. Thus, altered development of descendants of the second heart field and the neural crest could contribute to multicomponent malformation like Dandy-Walker.

Dandy-Walker malformation (DWM) is a posterior fossa malformation characterized by a huge posterior fossa cyst in communication with the fourth ventricle. Hydrocephalus is associated with more than 80% of cases and is usually treated by shunting. Despite infection being a common complication of the shunt, abscess formation within the cyst was reported only once.
A neonate affected by DWM developed a posterior fossa abscess following a shunt infection. The purulent collection was refractory to standard treatment (antibiotics and burr hole drainage); therefore, an endoscopic approach was performed in order to remove the purulent collection under direct vision. This material was aspirated with the help of an endoscopic ultrasonic aspirator. The outcome was favorable, with a resolution of infection and re-implantation of the ventriculo-peritoneal shunt. Surprisingly, post-operative radiological examination showed substantial modification of the anatomy of the posterior fossa with disappearing of the Dandy-Walker cyst. To the best of our knowledge, this is the first documented report of a true Dandy-Walker malformation that modified its anatomical appearance over time.
Endoscopic aspiration of intracranial purulent collection should be considered a valid option to manage complicated cases. An endoscopic ultrasonic aspirator may make the procedure more effective and faster.

Prenatal diagnoses of cystic malformations of the posterior fossa mainly encompass arachnoid cysts, Blake\'s pouch cysts and Dandy-Walker syndrome. To date, vermian cysts have not been reported prenatally.
To report a series of fetuses with a vermian cyst.
This was a single-center retrospective study conducted from 2012 to 2021. We included all fetuses presenting with a vermian cyst and excluded all other types of posterior fossa cyst. The cyst was visible at prenatal ultrasound (US) and/or magnetic resonance imaging (MRI). Postnatal imaging and/or clinical outcome data were available.
Sixteen fetuses fulfilled the inclusion criteria with a strong female predominance (n=13). US and MRI were performed at a mean gestational age of 29+5 and 33+1 weeks, respectively. In all patients, the cyst was in the vermian horizontal fissure. The mean longest dimension was about 10 mm. The vermis and other posterior fossa structures were otherwise normal. At postnatal imaging, 13 children underwent brain imaging including 11 MRIs with complete regression (n=9), stability (n=1) and increase in size (n=3) of the cyst. Psychomotor development was normal in 14 children. One child (with an inner ear malformation) showed a slight delay in walking and language acquisition. Slight walking ataxia was present in another child.
We report 16 fetuses with posterior fossa cysts located within the vermis at the level of the horizontal fissure, diagnosed at US and/or MRI and carrying an overall excellent neurological prognosis.

The traditionally described Dandy-Walker malformation comprises a range of cerebellar and posterior fossa abnormalities with variable clinical severity. We aimed to establish updated imaging criteria for Dandy-Walker malformation on the basis of cerebellar development.
In this multicenter study, retrospective MR imaging examinations from fetuses and children previously diagnosed with Dandy-Walker malformation or vermian hypoplasia were re-evaluated, using the choroid plexus/tela choroidea location and the fastigial recess shape to differentiate Dandy-Walker malformation from vermian hypoplasia. Multiple additional measures of the posterior fossa and cerebellum were also obtained and compared between Dandy-Walker malformation and other diagnoses.
Four hundred forty-six examinations were analyzed (174 fetal and 272 postnatal). The most common diagnoses were Dandy-Walker malformation (78%), vermian hypoplasia (14%), vermian hypoplasia with Blake pouch cyst (9%), and Blake pouch cyst (4%). Most measures were significant differentiators of Dandy-Walker malformation from non-Dandy-Walker malformation both pre- and postnatally (P < .01); the tegmentovermian and fastigial recess angles were the most significant quantitative measures. Posterior fossa perimeter and vascular injury evidence were not significant differentiators pre- or postnatally (P > .3). The superior posterior fossa angle, torcular location, and vermian height differentiated groups postnatally (P < .01), but not prenatally (P > .07).
As confirmed by objective measures, the modern Dandy-Walker malformation phenotype is best defined by inferior predominant vermian hypoplasia, an enlarged tegmentovermian angle, inferolateral displacement of the tela choroidea/choroid plexus, an obtuse fastigial recess, and an unpaired caudal lobule. Posterior fossa size and torcular location should be eliminated from the diagnostic criteria. This refined phenotype may help guide future study of the numerous etiologies and varied clinical outcomes.