Elsevier

Early Human Development

Volume 82, Issue 12, December 2006, Pages 827-835
Early Human Development

Using cerebral ultrasound effectively in the newborn infant

https://doi.org/10.1016/j.earlhumdev.2006.09.018Get rights and content

Abstract

Cranial ultrasound is the most available and easily repeatable technique for imaging the neonatal brain. Its quality and diagnostic accuracy depend on various factors; the suitability of the ultrasound machine for neonatal cranial work, the use of optimal settings and probes, appropriate scanning protocols, the use of a variety of acoustic windows and, not least, the scanning experience of the examiner. Knowledge of normal anatomy and the echogenicities of different tissues in normal and pathological situations as well as familiarity with the physiological and pathological processes likely to be encountered is vital. This paper assesses the value and appropriate use, safety and diagnostic accuracy of modern, high-quality ultrasound in evaluating the brain of the preterm and term born infant. Issues of concern regarding teaching, supervision and experience of the examiner are also addressed.

Introduction

Cranial ultrasound (cUS) is the most readily available and easily repeatable technique for imaging the neonatal brain. In contrast to other neuro-imaging tools such as magnetic resonance imaging (MRI) and computed tomography (CT), it can be done bedside with little disturbance to the infant. Neonatal cUS has been used for over 25 years and early studies on intraventricular (IVH) and parenchymal haemorrhage (HPI), post-haemorrhagic ventricular dilatation and cystic periventricular leukomalacia (PVL) have helped greatly our understanding of risk factors for neurodevelopmental abnormalities. Advances in technology have improved the quality of cUS imaging such that it can be a reliable tool for following brain development and showing the most frequently occurring forms of cerebral injury in the preterm and term born infant brain. The range of cUS diagnoses has increased with the recognition of more subtle patterns of injury and the appreciation of features suggestive of developmental, metabolic and infectious disorders.

In recent years concerns have been raised that cUS is not able to detect more subtle abnormality in the preterm infant [1], [2], [3], [4] and that it is not reliable for detecting lesions in the term infant with HIE and focal infarction. The arrival of MRI with its multi-slice coverage of the whole brain and large range of sequences has led a very negative press as far as cUS is concerned. This negativity is not well supported by comparative studies where both techniques receive the same time and expertise regarding image acquisition and analysis [5], [6].

The quality of cUS imaging and its diagnostic accuracy, as with any other imaging technique, depends on many factors. These include not only the suitability of the equipment for neonatal cranial work and the use of appropriate settings and probes, but also scanning at appropriate times depending on the pathology being sought, the use of different acoustic windows and not least the experience and expertise of the examiner.

This review assesses the value of appropriate timing of modern, high-quality cUS in evaluating both the preterm and term born infant brain and highlights the current areas of emphasis in this important field of neonatal medicine.

Section snippets

Scanning protocols

There are some technical guidelines on scanning quality and image acquisition [7] but there is no universal agreement about optimal timing for neonatal cUS. Scanning protocols vary considerably between different neonatal units. This variability reflects the different purposes for scanning which include diagnosis, assessing aetiology and predicting outcome, and the population of infants examined, imaging skills and interest of the examiner, the availability of an ultrasound scanner on the

Acoustic windows

The standard acoustic window used for imaging the neonatal brain is the anterior fontanelle. However, the cerebellum, brainstem and posterior subcortical WM may be poorly visualized using this approach. The detection of cerebellar abnormality via the anterior fontanelle is complicated by the echogenic appearance of the tentorium and cerebellar vermis. The cerebellum is increasingly recognized as an important structure not only for motor control but also for cognitive and behavioural

Safety

Although sequential cUS is clearly very important, its potential hazards and burden for the often sick and unstable newborn infant should be kept in mind. These include extra handling, applying pressure and cold gel to the fontanelle, the risk of dislodging tubes or lines or introducing infection from equipment that is not kept clean or from the operator. Most of these issues are relatively easy to prevent when appropriate safety and hygienic precautions are taken. All ultrasound equipment for

Teaching and experience and accuracy of cUS

Many studies have cast doubt on the accuracy of cUS for detecting cerebral abnormalities predictive of unfavourable outcome. Some have suggested that only in 40–50% of preterm infants with CP [38], [39], lesions were detectable on cUS though this contention is not supported by the study of De Vries [14]. Few studies have assessed the skills of the examiner and interpreter. In a study [4] comparing cUS and MRI no major lesions were missed on cUS [1], [2], [3] though subtle WM change on cUS and

Conclusions

Current evidence is that cUS imaging using modern machines, probes, a variety of acoustic windows and sequential scanning at optimal times gives high-quality images that are diagnostically accurate. Issues of teaching, supervision and experience for both paediatric and radiological staff need to be addressed and collaboration between paediatric and radiology departments is needed to improve protocols, image quality and interpretation. Whilst MRI does have advantages over cUS and clear clinical

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