Andrea Poretti

Computed Tomographic Findings in Microcephaly Associated with Zika Virus

This report describes the characteristics of infants who were exposed to the Zika virus in utero and were born with abnormalities of the central nervous system, as seen on computed tomography.

Diffusion tensor imaging in Joubert syndrome.

BACKGROUND AND PURPOSE: Neuropathologic findings and preliminary imaging studies demonstrated the absence of pyramidal tract and superior cerebellar peduncular decussation in individual patients with Joubert syndrome (JS). We hypothesized that functional-structural neuroimaging findings do not differ between the genetic forms of JS. MATERIALS AND METHODS: MR imaging was performed with a 3T MR imaging-unit. Multiplanar T2- and T1-weighted imaging was followed by diffusion tensor imaging (DTI). Isotropic diffusion-weighted images, apparent diffusion coefficient maps, and color-coded fractional anisotropy maps, including tractography, were subsequently calculated. RESULTS: In all 6 patients studied, DTI showed that the fibers of the superior cerebellar peduncles did not decussate in the mesencephalon and the corticospinal tract failed to cross in the caudal medulla. The patients represented various genetic forms of JS. CONCLUSION: In JS, the fibers of the pyramidal tract and the superior cerebellar peduncles do not cross, irrespective of the underlying mutation.

Joubert Syndrome and Related Disorders: Spectrum of Neuroimaging Findings in 75 Patients

In this nice Clinical Report, the authors review not only the classic features of Joubert syndrome (vermian hypoplasia and molar tooth sign) but also other lesser known features found in 75 patients. All showed vermian abnormalities and molar tooth sign and, in addition, the following findings were also quite common: enlarged posterior fossa, brain stem abnormalities, callosal dysgenesis with malrotation of the hippocampi, cephaloceles, and ventricular dilation. No correlation between imaging findings and genotype was detected. SUMMARY: VH and MTS are the neuroimaging hallmarks of JSRD. We aimed to look at the full spectrum of neuroimaging findings in JSRD and reviewed the MR imaging of 75 patients with JSRD, including 13 siblings and 4 patients with OFD VI. All patients had VH and enlargement of the fourth ventricle. The degree of VH and the form of the MTS were variable. In most patients, the cerebellar hemispheres were normal and the PF was enlarged. Brain stem morphology was abnormal in 30% of the patients. Supratentorial findings included hippocampal malrotation, callosal dysgenesis, migration disorders, cephaloceles, and ventriculomegaly. All patients with OFD VI had a similar pattern, including HH in 2 patients. No neuroimaging-genotype correlation could be found. The wide neuroimaging spectrum in our patients supports the heterogeneity of JSRD. Neuroimaging differences in siblings represent intrafamilial heterogeneity. Due to the absence of a correlation with genotype, neuroimaging findings are of limited value in classifying patients with JSRD.

Neuroimaging of pediatric posterior fossa tumors including review of the literature.

Conventional, anatomical MRI is an essential tool for diagnosis and evaluation of location, quality, and extent of posterior fossa tumors, but offers limited information regarding tumor grade and type. Advanced MRI techniques such as diffusion weighted imaging (DWI) and diffusion tensor imaging (DTI) may improve the specific diagnosis of brain tumors in the posterior fossa in children. In this review the conventional neuroimaging findings, as well as the DWI, and DTI characteristics of common pediatric posterior fossa tumors are discussed and summarized. J. Magn. Reson. Imaging 2012;35:32‐47.

The unique features of traumatic brain injury in children. review of the characteristics of the pediatric skull and brain, mechanisms of trauma, patterns of injury, complications, and their imaging findings--part 2.

Traumatic brain injury (TBI) is a major cause of morbidity and mortality in children. The unique biomechanical, hemodynamical, and functional characteristics of the developing brain and the age‐dependent variance in trauma mechanisms result in a wide range of age specific traumas and patterns of brain injuries. Detailed knowledge of the main primary and secondary pediatric injuries, which enhance sensitivity and specificity of diagnosis, will guide therapy and may give important information about the prognosis. In recent years, anatomical but also functional imaging methods have revolutionized neuroimaging of pediatric TBI. The purpose of this article is (1) to comprehensively review frequent primary and secondary brain injuries and (2) to give a short overview of two special types of pediatric TBI: birth related and nonaccidental injuries. J Neuroimaging 2012;22:e18–e41.

Delineation and Diagnostic Criteria of Oral-Facial-Digital Syndrome Type VI

Oral-Facial-Digital Syndrome type VI (OFD VI) represents a rare phenotypic subtype of Joubert syndrome and related disorders (JSRD). In the original report polydactyly, oral findings, intellectual disability, and absence of the cerebellar vermis at post-mortem characterized the syndrome. Subsequently, the molar tooth sign (MTS) has been found in patients with OFD VI, prompting the inclusion of OFD VI in JSRD. We studied the clinical, neurodevelopmental, neuroimaging, and genetic findings in a cohort of 16 patients with OFD VI. We derived the following inclusion criteria from the literature: 1) MTS and one oral finding and polydactyly, or 2) MTS and more than one typical oral finding. The OFD VI neuroimaging pattern was found to be more severe than in other JSRD subgroups and includes severe hypoplasia of the cerebellar vermis, hypoplastic and dysplastic cerebellar hemispheres, marked enlargement of the posterior fossa, increased retrocerebellar collection of cerebrospinal fluid, abnormal brainstem, and frequently supratentorial abnormalities that occasionally include characteristic hypothalamic hamartomas. Additionally, two new JSRD neuroimaging findings (ascending superior cerebellar peduncles and fused thalami) have been identified. Tongue hamartomas, additional frenula, upper lip notch, and mesoaxial polydactyly are specific findings in OFD VI, while cleft lip/palate and other types of polydactyly of hands and feet are not specific. Involvement of other organs may include ocular findings, particularly colobomas. The majority of the patients have absent motor development and profound cognitive impairment. In OFD VI, normal cognitive functions are possible, but exceptional. Sequencing of known JSRD genes in most patients failed to detect pathogenetic mutations, therefore the genetic basis of OFD VI remains unknown. Compared with other JSRD subgroups, the neurological findings and impairment of motor development and cognitive functions in OFD VI are significantly worse, suggesting a correlation with the more severe neuroimaging findings. Based on the literature and this study we suggest as diagnostic criteria for OFD VI: MTS and one or more of the following: 1) tongue hamartoma(s) and/or additional frenula and/or upper lip notch; 2) mesoaxial polydactyly of one or more hands or feet; 3) hypothalamic hamartoma.

Morphological spectrum of prenatal cerebellar disruptions

There is increasing evidence that the cerebellum is susceptible to both prenatal infections and haemorrhages as well as being vulnerable in extremely preterm babies, but not to perinatal and postnatal hypoxic-ischaemic injuries. Starting with the imaging appearance we describe and illustrate a spectrum of prenatal cerebellar disruptions: cerebellar agenesis; unilateral cerebellar hypoplasia; unilateral cerebellar cleft; global cerebellar hypoplasia; vanishing cerebellum in myelomeningocele; and disruption of cerebellar development in preterm infants. We discuss neuroradiological characteristics, possible disruptive events, and clinical findings in the different morphological patterns. Remarkably, the same disruptive agent can cause different neuroradiological patterns, which appear likely to represent a morphological spectrum. The analysis of imaging patterns is crucial in recognising cerebellar disruptions. Recognition of cerebellar disruptions and their differentiation from cerebellar malformations is important in terms of diagnosis, prognosis, and genetic counselling.

Cerebellar hypoplasia: differential diagnosis and diagnostic approach.

Cerebellar hypoplasia (CH) refers to a cerebellum with a reduced volume, and is a common, but non‐specific neuroimaging finding. The etiological spectrum of CH is wide and includes both primary (malformative) and secondary (disruptive) conditions. Primary conditions include chromosomal aberrations (e.g., trisomy 13 and 18), metabolic disorders (e.g., molybdenum cofactor deficiency, Smith–Lemli–Opitz syndrome, and adenylosuccinase deficiency), genetic syndromes (e.g., Ritscher‐Schinzel, Joubert, and CHARGE syndromes), and brain malformations (primary posterior fossa malformations e.g., Dandy–Walker malformation, pontine tegmental cap dysplasia and rhombencephalosynapsis, or global brain malformations such as tubulinopathies and α‐dystroglycanopathies). Secondary (disruptive) conditions include prenatal infections (e.g., cytomegalovirus), exposure to teratogens, and extreme prematurity. The distinction between malformations and disruptions is important for pathogenesis and genetic counseling. Neuroimaging provides key information to categorize CH based on the pattern of involvement: unilateral CH, CH with mainly vermis involvement, global CH with involvement of both vermis and hemispheres, and pontocerebellar hypoplasia. The category of CH, associated neuroimaging findings and clinical features may suggest a specific disorder or help plan further investigations and interpret their results. Over the past decade, advances in neuroimaging and genetic testing have greatly improved clinical diagnosis, diagnostic testing, recurrence risk counseling, and information about prognosis for patients and their families. In the next decade, these advances will be translated into deeper understanding of these disorders and more specific treatments.

Outcome of severe unilateral cerebellar hypoplasia

Aim  Complete or subtotal absence of one cerebellar hemisphere is exceptional; only single cases have been described. We aimed to assess the long‐term outcome in children with severe unilateral cerebellar hypoplasia (UCH).

Diffusion tensor imaging and fiber tractography in brain malformations

Diffusion tensor imaging (DTI) is an advanced MR technique that provides qualitative and quantitative information about the micro-architecture of white matter. DTI and its post-processing tool fiber tractography (FT) have been increasingly used in the last decade to investigate the microstructural neuroarchitecture of brain malformations. This article aims to review the use of DTI and FT in the evaluation of a variety of common, well-described brain malformations, in particular by pointing out the additional information that DTI and FT renders compared with conventional MR sequences. In addition, the relevant existing literature is summarized.