Pontocerebellar hypoplasia in extreme prematurity: clinical and neuroimaging findings

Not Dandy Walker variant: a review of prominent retrocerebellar CSF space in children

The prominent retrocerebellar cerebrospinal fluid (CSF) space can be frequently encountered on paediatric neuroimaging studies. In cases involving abnormal vermian development where imaging does not align with the established criteria of Dandy-Walker malformation (DWM), the term "Dandy-Walker variant or continuum" has been historically employed to describe the aberrant posterior fossa development. Instead, the emphasis is on a more elaborate description of the findings in the posterior fossa. Moreover, combining the findings in the supratentorial brain can occasionally predict certain neurogenetic disorders that mimic Dandy-Walker phenotype. The present review demonstrates and differentiates the imaging features of various entities that result in an enlarged retrocerebellar CSF space, such as inferior vermian hypoplasia (IVH) and several neurogenetic conditions.

Classic "PCH" Genes are a Rare Cause of Radiologic Pontocerebellar Hypoplasia

The term Pontocerebellar Hypoplasia (PCH) was initially used to designate a heterogeneous group of fetal-onset genetic neurodegenerative disorders. As a descriptive term, PCH refers to pons and cerebellum of reduced volume. In addition to the classic PCH types described in OMIM, many other disorders can result in a similar imaging appearance. This study aims to review imaging, clinical and genetic features and underlying etiologies of a cohort of children with PCH on imaging. We systematically reviewed brain images and clinical charts of 38 patients with radiologic evidence of PCH. Our cohort included 21 males and 17 females, with ages ranging between 8 days to 15 years. All individuals had pons and cerebellar vermis hypoplasia, and 63% had cerebellar hemisphere hypoplasia. Supratentorial anomalies were found in 71%. An underlying etiology was identified in 68% and included chromosomal (21%), monogenic (34%) and acquired (13%) causes. Only one patient had pathogenic variants in an OMIM listed PCH gene. Outcomes were poor regardless of etiology, though no one had regression. Approximately one third of patients deceased at a median age of 8 months. All individuals had global developmental delay, 50% were non-verbal, 64% were non-ambulatory and 45% required gastrostomy feeding. This cohort demonstrates that radiologic PCH has heterogenous etiologies and the "classic" OMIM-listed PCH genes underlie only a minority of cases. Broad genetic testing, including chromosomal microarray and exome or multigene panels, is recommended in individuals with PCH-like imaging appearance. Our results strongly suggest that the term PCH should be used to designate radiologic findings, and not to imply neurogenerative disorders.

Differentiating Genetic Forms of Pontocerebellar Hypoplasia From Acquired Lesions Resembling Pontocerebellar Hypoplasia: Clinical, Neurodevelopmental, and Imaging Insight From 19 Extremely Premature Patients

It is well established that extreme prematurity can be associated with cerebellar lesions potentially affecting the neurologic prognosis. One of the commonly observed lesions in these cases is pontocerebellar hypoplasia resulting from prematurity, which can pose challenges in distinguishing it from genetically caused pontocerebellar hypoplasia. This confusion leads to unacceptable and prolonged diagnostic ambiguity for families as well as difficulties in genetic counseling. Therefore, it is crucial to identify the clinical and neuroradiologic features allowing to differentiate between acquired and genetic forms of pontocerebellar hypoplasia in order to guide clinical practices and improve patient care. In this regard, we report in the present manuscript the clinical, developmental, and radiologic characteristics of 19 very premature children (gestational age <28 weeks, now aged 3-14 years) with cerebellar lesions and discuss the causal mechanisms. Our findings support the notion that a combination of specific clinical and radiologic criteria is essential in distinguishing between acquired and genetic forms of pontocerebellar hypoplasia.

The relationship between neuroimaging and motor outcome in children with cerebral palsy: A systematic review - Part A. Structural imaging

BACKGROUND

Conventional Structural Magnetic Resonance Imaging (sMRI) is a mainstay in Cerebral Palsy (CP) diagnosis.

AIMS

A systematic literature review was performed with the aim to investigate the relationship between structural brain lesions identified by sMRI and motor outcomes in children with CP.

METHODS

Fifty-eight studies were included. The results were analysed in terms of population characteristics, sMRI (classified according to Krägeloh-Mann & Horber, 2007), gross and fine motor function and their interrelation.

OUTCOMES

White matter lesions were the most common brain lesion types and were present in 57.8 % of all children with uCP, in 67.0 % of all children with bCP and in 33 % of the group of mixed subtypes. Grey matter lesions were most frequently registered in children with dyskinesia (n = 42.2 %). No structural anomalies visualized by sMRI were reported in 5.7 % of all cases. In all lesion types, an equal distribution over the different gross motor function classification system categories was present. The included studies did not report sufficient information about fine motor function to relate these results to structural imaging.

CONCLUSIONS AND IMPLICATIONS

The relationship between brain structure and motor outcome needs to be further elucidated in a representative cohort of children with CP, using a more standardized MRI classification system.

Developmental cerebellar cognitive affective syndrome in ex-preterm survivors following cerebellar injury

Cerebellar injury is increasingly recognized as an important complication of very preterm birth. However, the neurodevelopmental consequences of early life cerebellar injury in prematurely born infants have not been well elucidated. We performed a literature search of studies published between 1997 and 2014 describing neurodevelopmental outcomes of preterm infants following direct cerebellar injury or indirect cerebellar injury/underdevelopment. Available data suggests that both direct and indirect mechanisms of cerebellar injury appear to stunt cerebellar growth and adversely affect neurodevelopment. This review also provides important insights into the highly integrated cerebral-cerebellar structural and functional correlates. Finally, this review highlights that early life impairment of cerebellar growth extends far beyond motor impairments and plays a critical, previously underrecognized role in the long-term cognitive, behavioral, and social deficits associated with brain injury among premature infants. These data point to a developmental form of the cerebellar cognitive affective syndrome previously described in adults. Longitudinal prospective studies using serial advanced magnetic resonance imaging techniques are needed to better delineate the full extent of the role of prematurity-related cerebellar injury and topography in the genesis of cognitive, social-behavioral dysfunction.

Terminology in morphological anomalies of the cerebellum does matter

Neuroimaging plays a key role in the diagnostic work-up of morphological abnormalities of the cerebellum. Diagnostic criteria for numerous morphological anomalies of the cerebellum are based on neuroimaging findings. Various morphological patterns have been described on neuroimaging including cerebellar hypoplasia, cerebellar agenesis, pontocerebellar hypoplasia, cerebellar dysplasia, cerebellar dysmorphia, and cerebellar atrophy. These patterns have specific differential diagnoses. The familiarity with the diagnostic criteria is mandatory for a correct diagnosis and a targeted work-up to avoid unnecessary investigations. A correct diagnosis is essential for early therapy, prognosis, and counseling of the affected children and their family.