Dandy-Walker syndrome and agenesis of the cerebellar vermis: diagnostic problems and genetic counselling

Fetal Cerebellar Vermis Circumference Measured by 2-Dimensional Ultrasound Scan: Reference Range, Feasibility and Reproducibility

Purpose: To provide 2-dimensional ultrasonographic (2D-US) normograms of cerebellar vermis biometry, as well as to evaluate the feasibility and the reproducibility of these measurements in clinical practice. Materials and Methods: A prospective cross-sectional study of 328 normal singleton pregnancies between 18 and 33 weeks of gestation. Measurements of the fetal cerebellar vermis circumference (VC) in the mid-sagittal plane were performed by both a senior and a junior operator using 2D-US. VC as a function of gestational age (GA) was expressed by regression equations. In 24 fetuses 3-dimensional (3D) reconstructed planes were obtained in order to allow comparisons with 2D-US measurements. The agreement between 2D and 3D measurements and the interobserver variability were assessed by interclass correlation coefficients (ICC). Results: Satisfactory vermis measurements could be obtained in 89.9% of cases. The VC (constant= - 12.21; slope=2.447; r=0.887, p<0.0001) correlated linearly with GA. A high degree of consistency was observed between 2D and 3D ultrasound measurements (ICC=0.846 95% CI 679-0.930) as well as between measurements obtained by different examiners (ICC=0.890 95% CI 989-0.945). Conclusion: 2-dimensional ultrasonographic measurements of cerebellar vermis throughout gestation in the mid-sagittal view seem to be feasible and reproducible enough to be potentially used in clinical practice. Such measurements may supply a tool for accurate identification of posterior fossa anomalies, providing the basis for proper counseling and management and of these conditions.

Primary cerebellar agenesis presenting as isolated cognitive impairment

Primary cerebellar agenesis is a rare entity. To the best of our knowledge, eleven living cases have been reported till date. Most of these were associated with some degree of motor impairment. We present a case of cerebellar agenesis in a child who presented with cognitive abnormalities leading to poor performance at school. No motor impairment was seen. Among the eleven cases reported earlier, only one case showed lack of motor impairment.

Malformazioni cistiche della fossa cranica posteriore

Le malformazioni cistiche della fossa cranica posteriore comprendono: il complesso di Dandy-Walker e le cisti aracnoidee. All'interno del cosiddetto complesso di Dandy-Walker vengono poi classificate: la malformazione di Dandy-Walker (MDW) verae propria, la Dandy-Walker variante (DWV) e la megacisterna magna (MCM). Il complesso di Dandy-Walker sarebbe costituito da malformazioni cistiche della fossa posteriore che da un punto di vista embriogenetico rappresenterebbero un continuum dalle forme più complesse (MDW) alle forme meno gravi (MCM). Esse raggruppano anomalie di sviluppo variamente associate del verme, della tela corioidea, dello spazio subaracnoideo retro-cerebello-bulbare e delle strutture durali, strutture che si formano e si posizionano simultaneamente tra la VII e la X settimana di vita fetale. La definizione della MDW include classicamente: una agenesia parziale o completa del verme associata ad ipoplasia degli emisferi cerebellari, una dilatazione cistica del IV ventricolo e una espansione della fossa posteriore associata ad alta inserzione del tentorio, del torculare di Erofilo e dei seni trasversi. Nella DWV esistono molte somiglianze anatomiche con la MDW, tuttavia l'elemento cardine nella distinzione fra le due e una rotazione del verme meno accentuata rispetto alia MDW. La MCM è un'anomala dilatazione della cisterna magna che comunica liberamente con il sistema ventricolare e gli spazi subaracnoidei in assenza di grossolane alterazioni del cervelletto. Da un punto di vista anatomo-patologico rappresenta una evaginazione della tela corioidea del IV ventricolo. Infine le cisti aracnoidee della fossa cranica posteriore sono formazioni a contenuto liquorale che si sviluppano nel contesto della membrana aracnoidea. Essa rappresenta quindi una entità diversa da un punto di vista anatomo-patologico dal continuum delle malformazioni del complesso di Dandy-Walker anche se difficile può essere la diagnosi differenziale fra MCM e cisti aracnoidea quando quest'ultima è posta nella stessa sede della MCM.

Quantitative Evaluation of the Fetal Cerebellar Vermis Using the Median View on Two-Dimensional Ultrasound

Background

Evaluation of the cerebellum and vermis is one of the integral parts of the fetal cranial anomaly screening.

Objectives

The aim of this study was to create a nomogram for fetal vermis measurements between 17 and 30 gestational weeks.

Patients and Methods

This prospective study was conducted on 171 volunteer pregnant women between March 2013 and December 2014. Measurements of the fetal cerebellar vermis diameters in the sagittal plane were performed by two-dimensional transabdominal ultrasonography.

Results

Optimal median planes were obtained in 117 of the cases. Vermian diameters as a function of gestational age were expressed by regression equations and the correlation coefficients were found to be highly statistically significant (P < 0.001). The normal mean (± standard deviation) for each gestational week was also defined.

Conclusion

This study presents the normal range of the two-dimensional fetal vermian measurements between 17 and 30 gestational weeks. In the absence of a three-dimensional ultrasonography, two-dimensional ultrasonography could also be used confidently with more time and effort.

Perinatal and short-term neonatal outcomes of posterior fossa anomalies

OBJECTIVE

To describe the perinatal and neonatal outcomes for fetuses with posterior fossa (PF) anomalies - mega-cisterna magna (MCM), persistent Blake's pouch (PBP) or the Dandy-Walker continuum (DWC) - using a new classification.

METHODS

46 cases with PF anomaly diagnosed on ultrasound (US) between 16 and 28 weeks' gestation were included. The images were reviewed and classified as one of the following: MCM, PBP or DWC. Outcomes were obtained from patient records.

RESULTS

30 cases with DWC, 6 with MCM, and 10 with PBP were identified. Associated anomalies were present in all groups, but more frequent in DWC. Agenesis of the corpus callosum and ventriculomegaly were more common in DWC than in MCM or PBP. Only fetuses with DWC were found to have chromosomal abnormalities. Perinatal outcomes differed significantly, with terminations of pregnancy more frequent in DWC. In the immediate postnatal period, infants with DWC had worse outcomes than those with MCM and PBP. Across all groups, those with associated anomalies had worse outcomes than those with an isolated PF anomaly.

CONCLUSION

Infants antenatally diagnosed with DWC had worse perinatal and short-term neonatal outcomes than those with MCM or PBP. Those with associated anomalies had uniformly poorer outcomes than those with isolated anomalies.

Development of the human cerebellum and its disorders

The cerebellum arises from two anatomically and molecularly different proliferative compartments: the cerebellar ventricular zone and the rhombic lip. The protracted development makes the cerebellum vulnerable to a broad spectrum of developmental disorders, of which the more frequent (the Dandy-Walker and related malformations and the pontocerebellar hypoplasias) are discussed in this article. Several genes for congenital malformations of the human cerebellum have recently been identified, including genes causing Joubert syndrome, the Dandy-Walker malformation, and pontocerebellar hypoplasias.

The Dandy-Walker variant: a case series of 24 pediatric patients and evaluation of associated anomalies, incidence of hydrocephalus, and developmental outcomes

OBJECT

The Dandy-Walker complex is a continuum of aberrant development of the posterior fossa that has been associated with multiple congenital anomalies, radiographic abnormalities, and developmental delay. The Dandy-Walker variant (DWV) is a unique entity believed to represent a milder form of the complex, and is characterized by a specific constellation of radiographic findings. In this retrospective case series, the authors report the association of the DWV with other congenital anomalies, the associated radiographic findings linked with DWV, and the developmental outcome in this population.

METHODS

The charts and radiographs of 10 male and 14 female patients treated between 2000 and 2006 were examined. The patients' mean gestational age was 35.6 weeks (range 23-41 weeks), and the mean follow-up period was 5.1 years (range 1 month-15 years).

RESULTS

Three patients died. Associated anomalies included cardiac (41.7%), neurological (33.3%), gastrointestinal (20.8%), orthopedic (12.5%), and genitourinary (12.5%) abnormalities. Less common were pulmonary and psychiatric findings. Developmental delay was identified in 11 of the 21 patients for whom follow-up was available. Five of 6 patients with isolated DWV had a normal developmental course. Radiographic findings associated with DWV included corpus callosum dysgenesis in 20.8%, ventricular enlargement in 29%, and vermian rotation in 8.3%. Shunts were placed in 4 of 7 patients with ventriculomegaly. Using the two-tailed Pearson correlation, the authors determined that developmental outcome was solely affected by neurological deficits and that ventricular enlargement predicted the need for shunt placement.

CONCLUSIONS

The DWV was associated with both extra- and intracranial anomalies. Associated radiographic abnormalities including ventriculomegaly were observed. Hydrocephalus requiring cerebrospinal fluid diversion may be indicated. Isolated DWV was associated with a good developmental outcome.

The Fetal Cerebellar Vermis

Fetal magnetic resonance provides a new tool in the imaging of the posterior fossa and is proving useful in cases that are difficult to assess sonographically by allowing further assessment of the fourth ventricle, cisterna magna, and vermian growth and development. We describe various criteria with which to evaluate vermian growth, including vermian biometry and the relationship between the superior and inferior lobes. We demonstrate 2 markers of normal vermian development: the primary fissure and fastigial point. We illustrate the tegmento-vermian angle, "closure" of the fourth ventricle, and communication of the fourth ventricle with the basal cisterns during development and in several disorders. We correlate those features with the expected embryological course of development and illustrate identification of these features and associated abnormalities of the posterior fossa, brain stem, and central nervous system in mid-trimester scans of fetuses with abnormal development. Correlation with contemporaneous ultrasound examinations is demonstrated.

Trimyelia with divergent cord pathways and three foramina magni

OBJECT

We report the rare finding of trimyelia with divergent cord pathways in a 33 5/7-week-old fetus who died shortly after spontaneous vaginal delivery.

METHODS

The main autopsy findings were three separate and distinct spinal cords, arising from the medulla and exiting through three separate foramina magni. The two lateral cords coursed toward each upper extremity and the medulla split into two halves that rejoined to form a central cervical cord. Further evaluation of this anomaly revealed agenesis of the cerebellar vermis and cystic dilation of the fourth ventricle. Microscopic cross-sections of the two lateral cords demonstrated well-formed central canals, white matter, and central gray with motor neurons. Sections of the abnormal mid-cervical cord demonstrated abnormally structured cord parenchyma without central canals.

CONCLUSIONS

Some features were consistent with iniencephaly; however, defects of the occipital bone, anterior spina bifida, and shortening of the spinal cord were absent. Although agenesis of the cerebellar vermis and cystic dilation of the fourth ventricle indicate Dandy-Walker syndrome, other features such as hydrocephalus, agenesis of the corpus callosum, infundibular hamartomas, and malformations of the inferior olives or an occipital encephalocele were absent. The possible pathogenesis of this intriguing pathological entity is briefly discussed.

Molar tooth sign in fetal brain magnetic resonance imaging leading to the prenatal diagnosis of Joubert syndrome and related disorders

Joubert syndrome is a rare autosomal recessive disorder characterized by ataxia, developmental delay, and oculomotor and respiratory abnormalities in relation to cerebellar vermian and midbrain dysgenesis. The midbrain dysgenesis is responsible for the molar tooth sign on axial magnetic resonance imaging (MRI). This classic hallmark of Joubert syndrome has been identified in other disorders sharing overlapping clinical and radiologic features with Joubert syndrome. Recent identification of two different genes points to genetic heterogeneity in this group of disorders, now entitled Joubert syndrome and related disorders, making a genetic prenatal diagnosis not readily available. In addition, fetal ultrasonography lacks sensitivity in regard to posterior fossa malformation. Fetal MRI is now acknowledged as the method of choice to delineate posterior fossa malformation in a fetus. The identification of a molar tooth sign has, however, rarely been documented by a fetal brain MRI. We report a case of Joubert syndrome diagnosed prenatally using fetal MRI. We also discuss the etiology of Joubert syndrome in view of the recent genetic advances and murine models of cerebellar dysgenesis.

Brain stem and cerebellar findings in Joubert syndrome

Joubert syndrome is often missed clinically and radiologically if not enough attention is paid to its subtle and variable clinical presentation and the imaging findings in the posterior fossa. The purpose of this paper is to illustrate the brain stem and cerebellar imaging findings in Joubert syndrome. Awareness of the clinical and neuroimaging findings in Joubert syndrome and maintenance of a high index of suspicion are essential to correctly diagnose this rare congenital malformation.

MRI of the fetal posterior fossa

MRI is a useful tool to complement US for imaging of the fetal posterior fossa (PF). In France, the discovery of a PF malformation in the fetus frequently leads to termination of pregnancy (80% in a personal series). However, despite improved accuracy in the diagnosis of PF abnormalities, prognosis remains uncertain. The first objective of this review is to document the normal MRI landmarks of the developing fetal PF. Because of their thinness, the visibility of the cerebellar fissures is dramatically delayed on MRI compared to macroscopic data. An important landmark is identification of the primary fissure of the vermis, normally seen at around 25-26 weeks' gestation (WG) on the sagittal slice, separating the larger posterior lobe from the anterior lobe (volume ratio around 2:1). The prepyramidal and secondary fissures are usually only identifiable after 32 WG and the hemispheric fissures are difficult to see until the end of pregnancy. Considering the signal changes, high signal on T2-weighted (T2-W) sequences is seen from 25 WG in the posterior part of the brain stem (tegmentum and ascending sensory tracts) related to myelination. The low signal intensities seen within the cerebellum on T2-W images correspond to high cellularity of grey matter (deep nuclei), as there is no myelination within the white matter before 38 WG. The second objective is to highlight the signs highly predictive of a poor neurological prognosis. Lack of pontine curvature or vermian agenesis without a PF cyst (small volume of PF) is greatly associated with poor neurological status. The third objective is to propose a diagnostic strategy in difficult cases where prognosis is important, e.g. the Dandy Walker continuum. Analysis of the cerebellum is often impossible if a PF cyst is present (whatever its nature) as the mass effect usually blurs the foliation and even impairs evaluation of the normal ratio between the posterior and anterior lobes of the vermis. Isolated cerebellar hypoplasias raise the question of prognosis and genetic counselling. Such uncertainties require an amniocentesis and a careful search for other anomalies (cerebral and extracerebral). Unilateral abnormalities of a cerebellar hemisphere can be associated with good neurological status if they are isolated. The final objective is to discuss other rare PF fetal abnormalities, such as vascular malformations and tumours.

Midbrain disconnection: an aetiology of severe central neonatal hypotonia

A full term girl exhibited massive hypotonia related to severe posterior fossa abnormalities consisting of pontocerebellar hypoplasia with midbrain disconnection. The latter was due to lack of one and marked hypoplasia of the other cerebral peduncles. In addition, there was mild vermian and cerebellar hypoplasia. Compared to usual pontocerebellar hypoplasia, the midbrain disconnection is a distinctive feature of our case. It is a rare malformation only three similar cases have previously been described.

Rat Mutations cvd and hob with Cerebellar Malformations Map to Chromosome 2

In this paper, we executed genome mapping and comparative mapping analyses for cvd and hob, autosomal recessive mutations with cerebellar vermis defect and cerebellar dysplasia in the rat. For the linkage analysis, we produced three sets of backcross progeny, (ACI x CVD)F(1) and (F344 x CVD)F(1) females crossed to a cvd homozygous male rat, and (HOB x WKY)F(1) males crossed to hob homozygous female rats. Analysis of the segregation patterns of simple sequence length polymorphism (SSLP) markers scanning the whole rat genome allowed the mapping of these autosomal recessive mutations to rat Chromosome (Chr) 2. The most likely gene order is D2Mgh12 - D2Rat86 - D2Mit15 - D2Rat185 - cvd - D2Rat66 - D2Mgh13, and D2Mit18 - Fga -D2Mit14 - D2Rat16 - hob - D2Mgh13. Crossing test between a proven cvd heterozygous and a hob heterozygous rats demonstrated their allelism. Furthermore, comparative mapping indicated the cvd locus corresponds to mouse chromosome 3 and a strong candidate gene Unc5h3, a causative gene for the rostral cerebellar malformation mouse, was implicated.

Human malformations of the midbrain and hindbrain: review and proposed classification scheme

Although a great deal of interest in the genetics and etiology of cerebral, particularly forebrain, malformations has been generated in the past decade, relatively little is known about the basis of congenital malformations of the structures of the posterior fossa, namely the midbrain, cerebellum, pons, and medulla. In this review, we present a classification scheme for malformations of the midbrain and hindbrain based on their embryologic derivation, highlight four of the conditions associated with such abnormalities, and describe the genetics, prognosis, and recurrence risks for each. We describe several disorders in addition to Joubert syndrome with the distinctive radiologic sign known as the "molar tooth sign," comprised of midbrain and hindbrain malformations. We discuss Dandy-Walker malformation, its classical definition, and the surprisingly good outcome in the absence of other brain malformations. We consider the heterogeneous entity of cerebellar vermis hypoplasia and describe the recently identified gene associated with an X-linked form of this condition. Finally, the pontocerebellar hypoplasias are discussed in the context of their generally progressive degenerative and severe course, and the differential diagnosis is emphasized. We anticipate that as imaging technologies improve, differentiation of the various disorders should aid in efforts to identify the causative genes.

Malformations of the posterior fossa: current perspectives

Posterior fossa malformations are a special group of central nervous system anomalies that present during infancy with hypotonia, developmental delay, microcephaly, or hydrocephalus. Recent discoveries of the genetic and epigenetic factors that control hindbrain ontogenesis explain some of these disturbances in cerebellar development. A comprehensive classification of posterior fossa malformations is proposed with particular attention to Dandy-Walker malformation, Joubert syndrome, and other cerebellar hypoplasias. A rare form of cerebellar hypertrophy which caused repeated obstruction at the foramen magnum is recognized. The importance of the cerebellum in language, cognition, and brain growth is stressed.

The development of the fetal vermis: an in-utero sonographic evaluation

OBJECTIVE

To establish a nomogram for fetal vermis measurements during gestation.

METHODS

A prospective cross-sectional study of normal singleton pregnancies. Measurements of the fetal vermis width (in the axial plane) and height (in the sagittal plane) were performed by high-resolution transabdominal ultrasonography between 18 and 38 weeks of gestation in 256 fetuses.

RESULTS

Adequate vermis measurements were obtained in 256 fetuses. Vermian width and height as a function of gestational age and biparietal diameter were expressed by regression equations and the correlation coefficients were found to be highly statistically significant (P < 0.0001). The normal mean (+/- SD) for each gestational week was defined.

CONCLUSIONS

The present data offer the normal range of the vermian measurements throughout gestation. These values may allow intrauterine assessment of the development of the cerebellar vermis, as well as the posterior fossa.

Dandy-Walker like malformation in a Fischer-344 rat

A spontaneous cerebellar malformation was found in a 32-day-old male Fischer 344 rat. The cerebellar malformation was composed of a vermis defect and markedly dilated fourth ventricle. The cerebellar hemispheres were separated, with the left hemisphere being smaller than the right one. Degenerative/inflammatory lesions consisting of macrophage/lymphocyte infiltration, spheroidal calcium depositions, and astrocytic gliosis were seen adjacent to the cerebral aqueduct. Abnormally arranged hyperplastic ependymal cells were observed beneath the fourth ventricle in the medulla oblongata. The gross findings of the present case resemble those of the human Dandy-Walker malformation. While a precise mechanism remains to be elucidated, degenerative/inflammatory lesions in the present rat may be involved in the pathogenesis of this malformation.

Neonatal cranial ultrasound

Neonatal cranial ultrasound continues to be a popular initial imaging modality because of the safety, low-cost, and portability of the examination. The higher frequency transducers and enhanced ability for signal processing that is possible with current ultrasound machines improves visualization of complex congenital anomalies, complications of pregnancy, and birth and neoplastic processes. This article reviews these conditions so that the reader will have a baseline knowledge of the ultrasound findings. With the use of neonatal cranial ultrasound, recognition of the maximum diagnostic information available on the sonogram and appropriate use of other cross-sectional imaging modalities are improved.

Cystic malformation of the posterior cerebellar vermis in transgenic mice that ectopically express Engrailed-1, a homeodomain transcription factor

In WEXPZ-En-1 transgenic mice, Engrailed-1, a homeodomain-containing transcription factor, is ectopically expressed in the developing brain under control of the Wnt-1 enhancer. En-1 is a developmental regulatory control gene which has an essential role in the formation of the midbrain and cerebellum. Approximately 28% of WEXPZ-En-1 + mice develop cystic malformations of the posterior lobe of the cerebellar vermis, fourth ventricular dilatation, and postnatal hydrocephalus. These anatomic features are also found among the spectrum of posterior fossa malformations in humans. Expression characteristics of the WEXP transgene suggest that the neuropathology observed in WEXPZ-En-1+ mice stems from overexpression of En-1 during fetal and neonatal phases of cerebellar development. These observations raise the possibility that abnormal regulation of Engrailed genes, or targets of Engrailed, may be involved in the pathogenesis of cystic central nervous system malformations of the posterior fossa in humans.

Joubert's syndrome: new cases and review of clinicopathologic correlation

The authors report on seven patients, six males and one female, with Joubert's syndrome who underwent developmental evaluation, neurologic and ophthalmologic examinations, and magnetic resonance imaging of the brain. All patients had severe developmental delay, hypotonia, impairment of smooth visual pursuit, and saccadic eye movements. Six had jerky eye movements and ptosis was observed in two patients and retinal dystrophy in one. The posterior lobe of the vermis was absent in all patients and the small rudimentary anterior lobe lacked fusion in the midline, with cleft formation in five patients. Malformation of the pontomesencephalic junction, with prominent superior cerebellar peduncles and deep interpeduncular fossa, was observed in all patients. Abnormal cerebellar-brainstem and cerebellocortical connections because of the lack of the posterior vermis and dysplasia of the deep cerebellar nuclei might be responsible for the abnormal eye movements and retarded development in Joubert's syndrome. Correlation between radiologic findings and clinical symptoms and the possible role of abnormal patterning of the midbrain-hindbrain by homeotic genes during embryonic development are reviewed.

Familial congenital saccade initiation failure and isolated cerebellar vermis hypoplasia

The underlying lesion in congenital saccade initiation failure (c-SIF) ('congenital ocular motor apraxia', 'Cogan's apraxia') is uncertain. Often no abnormality can be found, yet in others a midline cerebellar abnormality has often been reported. We examined this cerebellar association in a brother and sister. In addition to standard ophthalmological and neurological examinations, both siblings underwent ocular motor testing and neuroradiological investigations including CT and MRI. Both siblings exhibited the typical signs of c-SIF, including headthrusting, synkinetic blinking, missed-nystagmus quick phases, mild developmental delay, and speech difficulties. CT and MRI revealed cerebellar vermis hypoplasia in the brother, but appeared normal in the sister. No other neuroradiological abnormalities were detected. These cases highlight the wide variability in the association of vermis abnormalities with c-SIF, despite the inheritance and similar clinical manifestations. They show that either: (1) the vermis is causal in saccade triggering, but that c-SIF may result from very subtle damage that is beyond MRI resolution in some cases; or (2) that a vermis abnormality per se is not causative but only a marker of another subtle abnormality, either structural or possibly biochemical.

Non-progressive congenital ataxias

Congenital ataxias (CA) are rare, predominantly non-progressive syndromes characterized by marked hypotonia, developmental delay followed by the appearance of ataxia. Most children show marked speech and cognitive developmental problems. Non- progressive CA (NPCA) can be divided into pure CA without additional symptoms and syndromes with CA. Pure CA can be due to cerebellar malformations as (hereditary or non-hereditary) cerebellar hypoplasia, Dandy Walker syndrome, or occasionally supratentorial abnormalities. Ataxic syndromes are less frequent, but more distinctive. There are syndromes (e.g. Joubert syndrome) where ataxia is a cardinal feature and others where ataxia is only an occasional symptom. Acquired ataxias, due to congenital cytomegalovirus infection or perinatal problems, form a small third group. In about half of all cases with NPCA, aetiology and inheritance are still unknown. Diagnosis of NPCA is made by a typical history and careful clinical examination. Diagnosis of a more distinctive ataxic syndrome may be possible on clinical grounds. Neuroimaging with special attention to the posterior fossa will aid accurate clinical classification. Early progressive ataxias require careful differentiation from other types.

Prenatal sonographic diagnosis of vermal agenesis

Agenesis of the vermis as detected during gestation by ultrasonography may indicate the existence of various malformation arrays or syndromes. We report on our observations of five cases of complete vermal agenesis that were detected at 22-31 weeks of gestation. All had a vertex presentation and transvaginal sonography established the diagnosis of vermal agenesis. Two of the vermal agenesis cases had no associated anomalies outside the central nervous system (CNS). In one, the cerebellar cleft was the only abnormality present and the other also had lobar holoprosencephaly. The three remaining fetuses had trisomy 13 and featured various additional extra-CNS anomalies. The association of complete vermal agenesis and trisomy 13 has not been previously reported. Our experience with this series suggests that supplementation with vaginal fetal sonography is a valuable tool for obtaining a more accurate view of the posterior fossa whenever a cyst or a cyst-like abnormality is detected by transabdominal sonography. A finding of isolated vermal agenesis appears to mandate a careful search for additional anomalies and the performance of karyotype analysis.

Bilateral porencephaly, cerebellar hypoplasia, and internal malformations: two siblings representing a probably new autosomal recessive entity

We report on 2 sibs with bilateral porencephaly, absence of the septum pellucidum, and pancerebellar hypoplasia including absence of the vermis. Situs inversus and tetralogy of Fallot was present in one, and an atrial septal defect in the other. This constellation of findings is discussed against the background of familial porencephalies and schizencephalies, familial cerebellar hypoplasias, and asplenia/polysplenia syndromes. It is concluded that the described constellation of findings constitutes a new entity of probably autosomal recessive inheritance.

Hereditary cerebellar vermis defect in the Lewis rat

We report a new rat model of hereditary cerebellar vermis defect. Mutant rats exhibited hind-leg paralysis from about 14 days old. Gross pathology showed the cerebellar vermis defect, fused cerebellar hemispheres and cyst formation. Ectopic dysplastic cerebellar tissues existed in the cerebello-pontine junctional zones. Mild disarrangement of lamination was also observed in the fused cerebellar hemispheres. The present mutant may serve as a valid model for studying the cerebellar vermis defect under the genetic control.

Vermian agenesis without posterior fossa cyst

We report 11 cases of vermian partial agenesis without posterior fossa cyst or hemispheric abnormalities. Characteristic MR signs were: absence of the posterior lobe, hypoplasia of the anterior lobe, a narrow sagittal cleft separating the hemispheres ("buttocks sign") and fourth ventricle deformity. The main clinical signs were complex oculomotor dysfunction and developmental delay. None of the patients had respiratory symptoms. Consideration is given to the relationship between Joubert syndrome and this entity as well as to embryological data.

Posterior fossa abnormalities in children with infantile spasms

In order to explore possible pathophysiologic involvement of the brain stem in infantile spasms, we retrospectively compared clinical and electroencephalographic (EEG) features of 14 children with infantile spasms who had gross posterior fossa abnormalities on neuroimaging studies with 84 children with infantile spasms who had either normal neuroimaging (n = 19) or supratentorial abnormalities (n = 65). Children with posterior fossa abnormalities how lower mean initial and follow-up developmental quotients compared to those with normal imaging or supratentorial abnormalities alone. Age of onset of infantile spasms, latency to treatment, response to steroids, and follow-up EEG pattern were not significantly different among the three groups. Six children (6%) had Dandy-Walker cysts, an association rarely reported with infantile spasms. We conclude that the presence of posterior fossa abnormalities in patients with infantile spasms portends a relatively poor developmental outcome.

Association of facial hemangiomas with Dandy-Walker and other posterior fossa malformations

Cutaneous hemangiomas are common benign tumors of infancy that only rarely are associated with malformations in other tissues or organs. We report nine infants with large facial hemangiomas who also had Dandy-Walker malformations or similar posterior fossa abnormalities. On the basis of the experience with our patients and with those previously reported, we recommend radiographic imaging studies of the brain of infants with large, aggressive facial hemangiomas to rule out posterior fossa defects.

Prenatal diagnosis of Dandy-Walker malformation in a family displaying X-linked inheritance

The diagnosis of Dandy-Walker malformation was made on the ultrasonographic evaluation of a 33-week male fetus. Pedigree analysis revealed a family history of isolated Dandy-Walker malformation in three other males, suggesting an X-linked recessive inheritance pattern.

Early neurological manifestations and brain anomalies in Marden-Walker syndrome

We report on an infant with the Marden-Walker syndrome. In addition to the consistent neurological abnormalities described previously in this syndrome, the infant had a striking neurological constellation, absence of primitive reflexes, jerky eye movements, failure to habituate to repeated stimuli, inadequate behavior development, and absence of orientation responses to visual or auditory stimuli. Muscle biopsy showed a similar pattern to the congenital fiber-type disproportion. Ultrasonograms and magnetic resonance imaging of his brain demonstrated absence of corpus callosum, colpocephaly, hypoplastic brainstem, hypoplasia of the inferior vermis and of the cerebellar hemispheres. These findings further delineate this syndrome and suggest that prenatal central nervous system (CNS) dysfunction, mainly of the cerebellum and brainstem, may play a significant role in the pathogenesis of the Marden-Walker syndrome.

Joubert syndrome: a review

We review 72 previously reported and 29 new patients with the possible diagnosis of Joubert syndrome. We define diagnostic criteria for this syndrome and present the data available in 94 patients that fulfill our criteria. We present the data regarding the clinical, neuroradiological, and ophthalmological manifestations and the prognosis of these 94 patients. We propose a classification of the patients with this diagnosis in 2 groups: those with retinal dystrophy and those without. Retinal dystrophy runs true in families and was never absent when renal cysts were reported.

The Dandy-Walker syndrome: the value of antenatal diagnosis

The Dandy-Walker syndrome can be accurately diagnosed in utero by sonographic demonstration of characteristic morphologic changes in the fetal posterior fossa. Three cases of Dandy-Walker syndrome are described. The associated intracranial and extracranial anomalies are reviewed, and the value of antenatal diagnosis is discussed.

The agyria-pachygyria complex: a spectrum of cortical malformations

Agyria-pachygyria is a relatively common brain malformation in humans as shown by the recent experience with CT scan and MR imaging. However, the specificity of imaging is not completely established and it is not known whether all cases with a thick cortical ribbon and a smooth surface correspond histologically to actual agyria-pachygyria or may belong to different pathological anomalies such as polymicrogyria. The extent, distribution and detailed structure of agyria-pachygyria vary widely and the clinical features are accordingly very diverse. Rather than one entity, pachygyric cortical abnormalities form a broad spectrum that raises different clinical, nosological and genetic problems. Therefore, a precise analysis of each case is necessary to establish the prognosis and risk of recurrence.