Review article
Morphological spectrum of prenatal cerebellar disruptions

https://doi.org/10.1016/j.ejpn.2008.09.001Get rights and content

Abstract

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.

Introduction

The high spatial resolution, the excellent tissue contrast, and the multiplanar imaging offered by magnetic resonance imaging (MRI) have facilitated a more accurate and precise identification and description of cerebral and cerebellar developmental abnormalities in children.1 These abnormalities include both malformations and disruptions.

Malformations are defined as morphological defects of an organ, part of an organ, or a larger region of the body resulting from an intrinsically abnormal developmental process.2 Cerebellar malformations such as Dandy–Walker malformation,3, 4 Joubert syndrome,5, 6 or rhombencephalosynapsis7, 8 have been extensively described. Furthermore, classification schemes of cerebellar malformations have been proposed combining imaging with molecular biology.9, 10

Disruptions are defined as morphological defects of an organ, part of an organ, or a larger region of the body resulting from an extrinsic breakdown of, or an interference with, an originally normal developmental process.2 It may well be that genetic factors contribute to the susceptibility to disruptions.

Good examples of disruptions are twin disruption sequence,11 amnion rupture sequence,12 and hydranencephaly.13 Intrauterine death of one foetus in a monochorionic twin pregnancy is associated with high morbidity and mortality in the surviving co-twin. Alternatively, acute blood loss into the dying twin through placental anastomoses may result in hypotension and hypoxic-ischaemic damage to cerebral and visceral tissue in the surviving twin. The ensuing clinical picture often results primarily from the cerebral lesions and is characterised by severe neurological symptoms.11 Amnion rupture sequence represents a disruption sequence characterised by major anomalies of the craniofacial region, body wall, and limbs. The mechanism involved in the pathogenesis may be vascular disruption,12 which includes ischaemic or haemorrhagic lesions. Hydranencephaly is characterised by a virtual absence of the cerebral hemispheres, leaving only glial membranous sacs filled with cerebrospinal fluid. The aetiology includes several disruptive factors such as vascular lesions or infection.13

To date, cerebellar disruptions have received less attention in the literature than cerebellar malformations. Therefore we have reviewed our patients and published cases of cerebellar disruptions in an attempt to facilitate their characterisation on the basis of the morphological pattern and the postulated aetiology.

Section snippets

Case selection

This study addresses only prenatal cerebellar disruptions with the exception of neonatal cerebellar disruption related to very preterm neonates. Therefore cerebellar disruptions occurring outside of this period, such as neonatal cerebellar haemorrhages or profound perinatal hypoxia, have not been included. The conditions listed in Section 3 have been compiled from the following sources: for many years we have been collecting patients with cerebellar disruptions in our clinical practice and from

Global cerebellar hypoplasia

The term “global cerebellar hypoplasia” describes a cerebellum of reduced volume. On midsagittal sections the vermis is small but retains a (near) normal shape. Owing to the reduction in size of the cerebellum, the subarachnoid spaces are passively enlarged.

Global cerebellar hypoplasia is a heterogeneous condition and can be due to a variety of causes, both malformation and disruptions.14 Typical malformations causing global cerebellar hypoplasia include chromosomal aberrations such as

Discussion

The spectrum illustrated demonstrates the importance of cerebellar imaging as a clue to a wide range not only of malformations, but also of disruptions. Disruptive mechanisms can affect the cerebrum and/or the cerebellum. However, cerebrum and cerebellum are variably vulnerable to the different disruptive factors in the prenatal period. On the basis of the disorders described, it appears that in the prenatal period the cerebellum is particularly vulnerable to infections and haemorrhages, as

Conclusion

Cerebellar disruptions appear to be common, potentially mimicking cerebellar malformations, although the pathogenesis is completely different. Cerebellar disruptions presenting different morphological patterns can be caused by the same disruptive agent, such as a cerebellar haemorrhage. This fact reveals that the different disruption patterns are not several independent disorders, but are likely to represent a morphological spectrum of the same pathogenetic mechanism. Therefore, a clear

Acknowledgements

Dr. Poretti was financially supported by a donation from the United Bank of Switzerland (UBS). This donation was made at the request of an anonymous client.

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