Paolo Tortori-Donati

Spinal dysraphism: A review of neuroradiological features with embryological correlations and proposal for a new classification

Abstract Our purpose was to review the neuroradiological features of spinal dysraphism and to correlate them with clinical findings and up-to-date embryological theory. We also aimed to formulate a working classification which might prove useful in clinical practice. We reviewed series of 986 children referred to our Spina Bifida Centre in the past 24 years. There were 353 children with open spinal (OSD) and 633 with closed (skin-covered) spinal (CSD) dysraphism. By far the most common open abnormality was myelomeningocele, and all patients with OSD had a Chiari II malformation. CSD was categorised clinically, depending on the presence of a subcutaneous mass in the back. CSD with a mass mainly consisted of lipomas with dural defects and meningoceles, and accounted for 18.8 % of CSD. CSD without a mass were simple (tight filum terminale, intradural lipoma) or complex (split cord malformations, caudal regression). Our suggested classification is easy to use and to remember and takes into account clinical and MRI features; we have found it useful and reliable when making a preoperative neuroradiological diagnosis in clinical practice.

Cystic malformations of the posterior cranial fossa originating from a defect of the posterior membranous area : Mega cisterna magna and persisting Blake's pouch : two separate entities

Cystic malformations of the posterior cranial fossa are all but arachnoid cysts contained within the general context of the Dandy-Walker complex and may be further classified in two groups on the basis of their embryological origin: anomalies of the anterior membranous area (AMA) and anomalies of the posterior membranous area (PMA). Whether the latter group of malformations can be regarded as separate entities is still quite controversial. The present authors give a detailed account of the various embryological stages in the formation of the posterior cranial fossa and its contents and propose the identification of two anomalies derived from a defect of the PMA: the mega cisterna magna (MCM) and the persisting Blakes pouch, a new entity with different MRI features from MCM. Criteria for their recognition are discussed, stressing the capital importance of a differential diagnosis in view of the radically different therapeutic approach.

Magnetic resonance imaging of spinal dysraphism.

Spinal cord development occurs through three consecutive periods. Gastrulation (weeks 2-3) is characterized by conversion of the embryonic disk from a bilaminar to a trilaminar arrangement and establishment of a notochord. Primary neurulation (weeks 3-4) produces the uppermost nine tenths of the spinal cord. Secondary neurulation and retrogressive differentiation (weeks 5-6) result in formation of the conus tip and filum terminale. Defects in these early embryonic stages produce spinal dysraphisms, which are characterized by anomalous differentiation and fusion of dorsal midline structures. Spinal dysraphisms may be categorized clinically into two subsets. In open spinal dysraphisms, the placode (non-neurulated neural tissue) is exposed to the environment. These disorders include myelomeningocele, myeloschisis, hemimyelomeningocele, and hemimyelocele, and are always associated with a Chiari II malformation. Closed spinal dysraphisms are covered by intact skin, although cutaneous stigmata usually indicate their presence. Two subsets may be identified based on whether a subcutaneous mass is present in the low back. Closed spinal dysraphisms with mass comprise lipomyeloschisis, lipomyelomeningocele, meningocele, and myelocystocele. Closed spinal dysraphisms without mass comprise complex dysraphic states (ranging from complete dorsal enteric fistula to neurenteric cysts, split cord malformations, dermal sinuses, caudal regression, and spinal segmental dysgenesis), bony spina bifida, tight filum terminale, filar and intradural lipomas, and persistent terminal ventricle. Magnetic resonance imaging is the imaging method of choice for investigation of this complex group of disorders.

Intracranial contrast-enhancing masses in infants with capillary haemangioma of the head and neck: intracranial capillary haemangioma?

Abstract Contrast-enhancing intracranial masses are rarely found in infants with extracranial capillary haemangiomas (CH). We aimed to assess their nature and progression in three patients undergoing CT and/or MRI. The changes in size of both extra- and intracranial lesions were recorded. In a fourth case, a single examination was obtained. All patients harboured one or two enhancing intracranial nodular, meningeal-based lesions. Diffuse leptomeningeal enhancement of the cerebellar surface was also seen in one, which disappeared at follow-up. In all but one of the cases, the intracranial lesions were on the same side as the extracranial CH. These lesions and the extracranial CH demonstrated parallel changes in size (suggesting that both represent CH) during follow-up of 1–2 years: the size of intracranial lesions and the extracranial CH decreased in two cases, whereas it was unchanged in the third. One patient had a persistent trigeminal artery, while another had cerebellar atrophy with high signal in the cortex on T2-weighted images. In some cases, extracranial CH are part of PHACE syndrome; the association with intracranial CH might represent a peculiar phenotype of this rare vascular phakomatosis. As extracranial CH are known to regress spontaneously in the majority of cases, a conservative approach is recommended also for presumed intracranial CH; surgery should be avoided unless follow-up studies demonstrate growth.

Medulloblastoma in children : CT and MRI findings

Our purpose was to determine whether medulloblastoma (MB) shows specific neuroradiological features which may be employed in differential diagnosis from other common posterior cranial fossa tumours in childhood. Preoperative MRI was performed on 20 children with MB, and preoperative CT in 17 of them. All underwent surgery and histopathological diagnosis. There was a constant relationship between high density on CT and low signal on T1-weighted images. Signal behaviour on T2-weighted images and the degree of contrast enhancement were more variable. Most tumours arose in the midline, from the cerebellar vermis, involving the fourth ventricle, but hemisphere and extra-axial neoplasms were also seen. The combination of high density on CT and low signal on T1-weighted images is highly suggestive of MB and may assist preoperative differential diagnosis from other posterior cranial fossa tumours.

Posterior fossa and arterial abnormalities in patients with facial capillary haemangioma: presumed incomplete phenotypic expression of PHACES syndrome

We report on the neuroradiological studies performed on three infants with capillary haemangioma (CH) of the head and neck with associated posterior fossa and arterial abnormalities. Posterior fossa malformations were represented by cerebellar hemispheric and vermian hypoplasia and cerebellar cortical dysgenesis, whereas arterial anomalies included bilateral agenesis, kinking, and looping of the internal carotid arteries. One patient had marked exophthalmos due to intraorbital CH. We suggest that these patients had an incomplete phenotypic expression of PHACES syndrome, a vascular phakomatosis characterised by the variable association of posterior fossa malformations, CH, arterial anomalies, coarctation of the aorta and cardiac defects, eye abnormalities, and sternal and medioventral defects. Evidence suggests that PHACES syndrome is not a random association but a true phakomatosis; further studies are awaited to shed light on a possible genetic background. The phenotypic spectrum is broad and still largely unexplored, and precise diagnostic criteria have not yet been identified. A causal teratogenic influence, possibly related to anomalous expression of vascular growth factors and their modulators, is suggested to occur between gestational weeks 3 and 5.5

Phenotypic characterization of hypomyelination and congenital cataract.

To define the clinical and laboratory findings in a novel autosomal recessive white matter disorder called hypomyelination and congenital cataract, recently found to be caused by a deficiency of a membrane protein, hyccin, encoded by the DRCTNNB1A gene located on chromosome 7p21.3‐p15.3.

Leukoencephalopathy with vanishing white matter:: an adult onset case.

Leukoencephalopathy with vanishing white matter (VWM) is an autosomal recessive disorder also known as childhood ataxia with central hypomyelination (CACH). Typically, the onset is in late infancy or early childhood with spasticity, cerebellar ataxia, and a relatively mild mental impairment.1 The course is chronic progressive with episodes of rapid deterioration after infection and minor head trauma. MRI shows a diffuse abnormality of the cerebral white matter with variable cerebellar atrophy mainly affecting the vermis. With time, there is evidence of white matter rarefaction leading to cystic degeneration. Increasing portions of the cerebral white matter vanish …

Rhombencephalosynapsis with facial anomalies and probable autosomal recessive inheritance: a case report

We report a 16‐year‐old boy, born to consanguineous parents, with mental retardation, gait disturbances and dysarthria; brain magnetic resonance showed features consistent with rhombencephalosynapsis. This condition is characterised by a hypoplastic single‐lobed cerebellum. The interest of this case is the presence of common ancestors, pointing to an autosomal recessive inheritance of the malformation.

Genetic Disorders Affecting White Matter in the Pediatric Age

Pediatric white matter disorders can be distinguished into well‐defined leukoencephalopathies, and undefined leukoencephalopathies. The first category may be subdivided into: (a) hypomyelinating disorders; (b) dysmyelinating disorders; (c) leukodystrophies; (d) disorders related to cystic degeneration of myelin; and (e) disorders secondary to axonal damage. The second category, representing up to 50% of leukoencephalopathies in childhood, requires a multidisciplinar approach in order to define novel homogeneous subgroups of patients, possibly representing “new genetic disorders” (such as megalencephalic leukoencepahlopathy with subcortical cysts and vanishing white matter disease that have recently been identified). In the majority of cases, pediatric white matter disorders are inherited diseases. An integrated description of the clinical, neuroimaging and pathophysiological features is crucial for categorizing myelin disorders and better understanding their genetic basis. A review of the genetic disorders affecting white matter in the pediatric age, including some novel entities, is provided.