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Introduction: Differential radiologic diagnosis of cystic malformations of the posterior fossa is often difficult with conventional imaging techniques because of overlapping features of these entities. Posterior fossa cystic malformations occupy the cerebrospinal fluid (CSF) spaces. They may create secondary dynamic effects on the movements of CSF. The aim of this study was to investigate CSF flow alterations in posterior fossa cystic malformations with CSF flow MR imaging. Methods: The study included 40 patients with cystic malformations of the posterior fossa. The patients underwent cardiac-gated phase-contrast cine MR imaging. CSF flow was qualitatively evaluated using an in-plane phase-contrast sequence in the midsagittal plane. The MR images were displayed in a closed-loop cine format. Results: Twelve of the patients had communicating arachnoid cyst, seven had non-communicating arachnoid cyst, ten had mega cisterna magna, six had Dandy-Walker malformation, two had Dandy-Walker variant, and three had Blake's pouch cyst. CSF flow MR imaging indicated the regions of no, slow or higher flow, direction of flow, and abnormal cystic fluid motion. Each malformation displayed a distinct CSF flow pattern. Conclusion: Phase-contrast cine MR imaging for CSF flow evaluation may be a useful adjunct to routine MR imaging in the evaluation of the cystic malformations of the posterior fossa because it can improve the specificity in differentiating such malformations.

PHACE and PHACES are acronyms for a syndrome of variable expression comprising posterior cranial fossa malformations, facial haemangiomas, arterial anomalies, aortic coarctation and other cardiac disorders, ocular abnormalities and stenotic arterial disease. We review five girls and three boys aged 1 month-14 years with disorders from this spectrum. Six had large facial haemangiomas but recent reports suggest that small haemangiomas may occur; hence our inclusion of two possible cases. We also focus on the recently recognised feature of progressive intracranial arterial occlusions, present in four of our patients, later than previously recognised, from 4 to 14 years of age. We suggest that many elements of this disorder could reflect an abnormality of cell proliferation and apoptosis.

We present a case of trans-sphenoidal encephalomeningocele in association with a posterior cranial fossa malformation which fulfils the criteria for the Dandy-Walker complex [1]. Congenital cardiovascular defects were also present. An abnormality of neural crest development may be responsible for the combined occurrence of these anomalies.

Abnormal cerebrospinal fluid (CSF) collections within the posterior fossa are defined by the Dandy-Walker complex (DWC) and by arachnoid cysts (AC). The DWC includes the Dandy-Walker malformation (DWM), the Dandy-Walker variant (DWV) and the mega-cisterna magna (MCM). In addition, Tortori-Donati et al. added persistent Blake's pouch cyst (BPC) as an independent entity within the DWC. BPC represents a posterior ballooning of the superior medullary velum into the cisterna magna. All of these malformations are overlapping developmental anomalies characterized by varying degrees of malformation of the medullary vela, the cerebellar vermis and hemispheres, the fourth ventricle choroid plexus, the posterior fossa subarachnoid cisterns and the enveloping meningeal structures. We present two cases of persistent BPC detected in two adult women without history of gestational or subsequent growth problems. They underwent neuroradiological investigation because of headache and because of recurrent episodes of loss of consciousness, respectively. The MRI findings included tetraventricular hydrocephalus, wide communication of the fourth ventricle and the cystic posterior fossa (i.e. BPC), inferior posterior fossa mass effect with or without hypoplasia of both the cerebellar vermis and the medial aspects of the cerebellar hemispheres, and absence of communication between fourth ventricle and the basal subarachnoid space in the midline posteriorly. Persistent BPC is defined by a failure of embryonic assimilation of the area membranacea anterior within the tela choroidea associated with imperforation of the foramen of Magendie. Typically this condition becomes symptomatic early in life. In the current cases the normal function of the laterally positioned foramina of Luschka probably helped to maintain some CSF flow between intraventricular and subarachnoid spaces, with the establishment of a precarious equilibrium characterized by a compensatory enlargement of the cerebral ventricular system (i.e. hydrocephalus).

We report a neonate in whom clinical and radiologic studies revealed features of both neurocutaneous melanosis and a Dandy-Walker malformation. We suggest that the association of these two conditions is perhaps not chance.

Half of patients with the Dandy-Walker malformation (DWM) have normal intellectual development. We aimed to identify feature on MRI associated with good intellectual prognosis. We reviewed 20 patients with DWM diagnosed on MRI, mean age 14.6+/-9.9 years. We assessed their intellectual development and related it to the MRI features. We found two groups with a statistically different intellectual outcome. All 14 patients with normal intellectual development had a normal lobulation of the vermis, without supratentorial anomalies. Of the six patients with mental retardation, three had an abnormal vermis, together with dysgenesis of the corpus callosum. In the other three, there were normal vermian anatomy with associated anomalies. Normal lobulation of the vermis, in the absence of any supratentorial anomaly, appears to be a good prognostic factor in DWM. Preservation of cerebrocerebellar pathways and neonatal plasticity could explain the normal intellectual development. These findings might be useful in prenatal diagnosis.

We report a boy with Menkes' disease in whom MRI revealed delayed myelination of the white matter, brain atrophy and tortuosity of the intracranial vessels. The characteristic MRI features of Menkes' disease were accompanied by a Dandy-Walker variant.

We present the cranial MRI findings in a 4-month-old girl with an atretic parietal cephalocele associated with multiple cerebral and ocular anomalies including lobar holoprosencephaly, a Dandy-Walker malformation, agenesis of the corpus callosum, grey-matter heterotopia, extra-axial cysts in various locations, bilateral microphthalmia and a retroocular cyst.

Wyburn-Mason syndrome is a neurocutaneous disorder which typically presents with unilateral vascular abnormalities involving the facial structures, orbits and brain. We would like to present the clinical and radiological features in a newborn who had bilateral manifestations of this disorder and review the literature.

The clinical and roentgenographic findings in ten patients with infratentorial retrocerebellar cysts are presented. An approach to the neuroradiological evaluation of retrocerebellar cysts and their differential diagnosis are discussed.

Cerebrospinal fluid images (cisternograms) are obtained after injection of an appropriate radiopharmaceutical into the subarachnid space. Abnormal accumulations of radioactivity may be seen in cisternographic images of patients with localized enlargement of the CSF space. A number of these patterns including post craniotomy defects, leptomeningeal, porencephalic, and posterior fossa cysts, and focal atrophy on the external cranial surface as well as meningoceles, myelomeningoceles and cerebellar atrophy are demonstrated.

A study of arterial vascular changes in different types of cerebellar defects is presented. PICA was found to be hypoplastic or aplastic in a large number of cases. In cases of cerebellar defects involving mostly the vermis, the hypoplastic PICA was frequently associated with a compensatory hyperdevelopment of HCA or MCA. Anomalies at the origin of the vertebral arteries associated with hypoplastic PICA were common.

A case of Dandy-Walker syndrome was diagnosed by ultrasound during the 30th week of pregnancy, observed again more clearly at 33 weeks and confirmed by CT after birth.

A description is given of the vascular features of the vertebral angiogram observed in patients with midline tumours. Supratentorial tumours are most likely to cause displacement of the posterior choroidal arteries and the thalamic veins. Examples of tumours of the hypothalamus, thalamus, pineal body, splenium of the corpus callosum and tectorial membrane of the midbrain are present. Infratentorial tumours are most likely to displace the posterior inferior cerebellar arteries, the precentral cerebellar vein and the pontomesencephalic vein. Examples are given of tumours of the pons cerebelli and the fourth ventricle, and of cysts in the cisterna magna.