Sonographic visualization of neonatal posterior fossa abnormalities through the posterolateral fontanelle

A Focus on the Cerebellum: From Embryogenesis to an Age-Related Clinical Perspective

The cerebellum and its functional multiplicity and heterogeneity have been objects of curiosity and interest since ancient times, giving rise to the urge to reveal its complexity. Since the first hypothesis of cerebellar mere role in motor tuning and coordination, much more has been continuously discovered about the cerebellum’s circuitry and functioning throughout centuries, leading to the currently accepted knowledge of its prominent involvement in cognitive, social, and behavioral areas. Particularly in childhood, the cerebellum may subserve several age-dependent functions, which might be compromised in several Central Nervous System pathologies. Overall, cerebellar damage may produce numerous signs and symptoms and determine a wide variety of neuropsychiatric impairments already during the evolutive age. Therefore, an early assessment in children would be desirable to address a prompt diagnosis and a proper intervention since the first months of life. Here we provide an overview of the cerebellum, retracing its morphology, histogenesis, and physiological functions, and finally outlining its involvement in typical and atypical development and the age-dependent patterns of cerebellar dysfunctions.

Superficial anatomy of the neonatal cerebrum - an ultrasonographic roadmap

Neurosonography is an essential imaging modality for assessing the neonatal brain, particularly as a screening tool to evaluate intracranial hemorrhage, hydrocephalus and periventricular leukomalacia. The primary advantages of neurosonography include portability, accessibility and lack of ionizing radiation. Its main limitations are intrinsic operator dependence and the need for an open fontanelle. Neurosonographic imaging acquisition is typically performed by placing a sector transducer over the anterior fontanelle and following sagittal and coronal sweeps. The sensitivity of neurosonography has markedly improved thanks to the adoption of modern imaging equipment, the use of dedicated head probes, and the employment of advanced diagnostic US techniques. These developments have facilitated more descriptive identification of specific cerebral anatomical details, improving understanding of the cerebral anatomy by conventional US. Such knowledge is fundamental for enhanced diagnostic sensitivity and is a key to understanding pathological states. Furthermore, familiarity with normal anatomy is crucial for understanding pathological states. Our primary goal in this review was to supplement these technological developments with a roadmap to the cerebral landscape. We accomplish this by presenting a systematic approach to using routine US for consistent identification of the most crucial cerebral landmarks, reviewing their relationship with adjacent structures, and briefly describing their primary function.

State-of-the-art neonatal cerebral ultrasound: technique and reporting

In the past three decades, cerebral ultrasound (CUS) has become a trusted technique to study the neonatal brain. It is a relatively cheap, non-invasive, bedside neuroimaging method available in nearly every hospital. Traditionally, CUS was used to detect major abnormalities, such as intraventricular hemorrhage (IVH), periventricular hemorrhagic infarction, post-hemorrhagic ventricular dilatation, and (cystic) periventricular leukomalacia (cPVL). The use of different acoustic windows, such as the mastoid and posterior fontanel, and ongoing technological developments, allows for recognizing other lesion patterns (e.g., cerebellar hemorrhage, perforator stroke, developmental venous anomaly). The CUS technique is still being improved with the use of higher transducer frequencies (7.5-18 MHz), 3D applications, advances in vascular imaging (e.g. ultrafast plane wave imaging), and improved B-mode image processing. Nevertheless, the helpfulness of CUS still highly depends on observer skills, knowledge, and experience. In this special article, we discuss how to perform a dedicated state-of-the-art neonatal CUS, and we provide suggestions for structured reporting and quality assessment.

The Utility of Cranial Ultrasound for Detection of Intracranial Hemorrhage in Infants

OBJECTIVE

The objective of this study was to evaluate the sensitivity and specificity of cranial ultrasound (CUS) for detection of intracranial hemorrhage (ICH) in infants with open fontanels.

METHODS

This was a retrospective study of infants younger than 2 years who had a CUS performed for the evaluation of potential ICH. We excluded patient with CUSs that were done for reasons related to prematurity, transplant or oncologic evaluations, routine follow-up or preoperative screen, or congenital and known perinatal anomalies. Two clinicians independently classified each of the patients with ICH into significant or insignificant based on the radiology reports.

RESULTS

Of 4948 CUS studies performed during the 5-year study period, 283 studies fit the inclusion criteria. Patient age ranged from 0 to 458 days, with a median of 33 days. There were 39 total cases of ICH detected, with 27 significant bleeds and 12 insignificant bleeds. Using computed tomography, magnetic resonance imaging, or clinical outcome as criterion standard, the overall ultrasound sensitivity and specificity for bleed were 67% (confidence interval [CI], 50%-81%) and 99% (CI, 97%-100%), respectively. For those with significant bleeds, the overall sensitivity was 81% (CI, 62%-94%), and for those with insignificant bleeds, it was 33% (CI, 1%-65%).

CONCLUSIONS

The sensitivity of CUS is inadequate to justify its use as a screening tool for detection of ICH in young infants.

Ultrasound and CT of the posterior fossa in neonates

Ultrasound, CT and MRI may all be used in the evaluation of the posterior fossa in neonates depending on the clinical scenario. Ultrasonography is particularly valuable for the evaluation of the neonatal brain because of the lack of ionizing radiation and the ability to perform exams at the bedside and, importantly, advancements in ultrasound technology now allow for diagnostic-quality imaging. While CT is still the initial imaging modality of choice in most neurologic emergencies, in the neonate, ultrasound is the first line in nontraumatic emergencies. The goal of this chapter is to discuss the ultrasound technique for evaluation of the cerebellum, to describe the normal sonographic and CT appearance of posterior fossa and to provide the classical findings of the most common cerebellar abnormalities. While ultrasound is able to accurately diagnosis a majority of cerebellar abnormalities in neonates, subsequent MR imaging remains essential to confirm findings and to detect associated abnormalities.

Anatomical subgroup analysis of the MERIDIAN cohort: posterior fossa abnormalities

OBJECTIVE

To assess the diagnostic and clinical contribution of fetal magnetic resonance imaging (MRI) in fetuses of the MERIDIAN cohort diagnosed with abnormalities of the posterior fossa as the only intracranial abnormality recognized on antenatal ultrasound.

METHODS

This was a subgroup analysis of the MERIDIAN study of fetuses with abnormalities of the posterior fossa (with or without ventriculomegaly) diagnosed on antenatal ultrasound in women who had MRI within 2 weeks of ultrasound and for whom outcome reference data were available. The diagnostic accuracy of ultrasound and MRI is reported, as well as indicators of diagnostic confidence and effects on prognosis and clinical management. Appropriate diagnostic confidence was assessed by the score-based weighted average method, which combines diagnostic accuracy with diagnostic confidence data.

RESULTS

Abnormalities confined to the posterior fossa according to ultrasound were found in 81 fetuses (67 with parenchymal and 14 with cerebrospinal fluid-containing lesions). The overall diagnostic accuracy for detecting an isolated posterior fossa abnormality was 65.4% for ultrasound and 87.7% for MRI (difference, 22.3% (95% CI, 14.0-30.5%); P < 0.0001). There was an improvement in 'appropriate' diagnostic confidence, as assessed by the score-based weighted average method (P < 0.0001), and a three-fold reduction in 'high confidence but incorrect diagnosis' was achieved using MRI. Prognostic information given to the women changed after MRI in 44% of cases, and the overall effect of MRI on clinical management was considered to be 'significant', 'major' or 'decisive' in 35% of cases.

CONCLUSIONS

Our data suggest that any woman whose fetus has a posterior fossa abnormality as the only intracranial finding on ultrasound should have MRI for further evaluation. This is on the basis of improved diagnostic accuracy and confidence, which impacts substantially on the prognostic information given to women as well as their clinical management. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

‘State-of-the-Art’ Neonatal Cranial Ultrasound

Cranial ultrasound (cUS) provides bedside imaging access to the neonatal brain. Modern scanners and the use of various acoustic windows give detail not only of the well known pathologies met in the preterm infant, but also allow assessment of more subtle aspects of normal and abnormal brain growth and development. cUS is also very helpful in the early diagnosis of the many aetiologies of neonatal encephalopathy and seizures in the term infant and the subsequent monitoring of progress of hypoxic-ischaemic brain injury. Training issues in cUS need to be addressed.

Cranial ultrasonography of the immature cerebellum: Role and limitations

Cranial ultrasonography (CUS) is a reliable and non-invasive tool to detect frequently occurring brain abnormalities and to monitor brain development and maturation in high risk neonates. Standard CUS views are obtained through the anterior fontanel. However, evaluation of the posterior fossa is often suboptimal with this approach. Cerebellar injury occurs frequently in preterm infants and has important prognostic consequences. Early detection is therefore important. This review focuses on techniques that optimize the performance of CUS when studying the preterm cerebellum, including the use of the mastoid fontanel and the adaptation of focus points and scan frequencies. For illustration, CUS images of the normal posterior fossa anatomy as well as examples of abnormalities that may be encountered in preterm infants are included. We also discuss the limitations of CUS and the role of magnetic resonance imaging.

State of the art cranial ultrasound imaging in neonates

Cranial ultrasound (CUS) is a reputable tool for brain imaging in critically ill neonates. It is safe, relatively cheap and easy to use, even when a patient is unstable. In addition it is radiation-free and allows serial imaging. CUS possibilities have steadily expanded. However, in many neonatal intensive care units, these possibilities are not optimally used. We present a comprehensive approach for neonatal CUS, focusing on optimal settings, different probes, multiple acoustic windows and Doppler techniques. This approach is suited for both routine clinical practice and research purposes. In a live demonstration, we show how this technique is performed in the neonatal intensive care unit. Using optimal settings and probes allows for better imaging quality and improves the diagnostic value of CUS in experienced hands. Traditionally, images are obtained through the anterior fontanel. Use of supplemental acoustic windows (lambdoid, mastoid, and lateral fontanels) improves detection of brain injury. Adding Doppler studies allows screening of patency of large intracranial arteries and veins. Flow velocities and indices can be obtained. Doppler CUS offers the possibility of detecting cerebral sinovenous thrombosis at an early stage, creating a window for therapeutic intervention prior to thrombosis-induced tissue damage. Equipment, data storage and safety aspects are also addressed.

Cerebellar hemorrhage in very low birth weight premature infants: the advantage of the posterolateral fontanelle view

OBJECTIVE

The purpose of this study was to determine the prevalence of cerebellar hemorrhage in very low birth weight infants using the posterolateral fontanelle for ultrasound (US) examination.

METHODS

The study included 125 very low birth weight premature infants (defined as equal or less than 1500 grams at birth) hospitalized in the premature or neonatal intensive care departments that had at least one head US examination including both anterior and posterolateral fontanelle scans.

RESULTS

On US performed through the posterolateral fontanelle, four (3.2%) infants had echogenic posterior fossa lesions interpreted as hemorrhages. None of these lesions were initially or retrospectively observed through the standard anterior fontanelle scan. Two infants died at age 4 and 39 days, respectively. All survivors are being followed up in the hospital's neurodevelopment outpatient clinic.

CONCLUSIONS

Cerebellar hemorrhage may be overlooked on standard anterior fontanelle views. The posterolateral approach may assist in diagnosing these lesions.

Ultrasound detection of posterior fossa abnormalities in full-term neonates

Routine cranial ultrasonography, using the anterior fontanelle as acoustic window enables visualization of the supratentorial brain structures in neonates and young infants. The mastoid fontanelle enables a better view of the infratentorial structures, especially cerebellar hemorrhage in preterm infants. Reports on the usefulness and reliability of cranial ultrasonography using the mastoid fontanelle approach for the detection of posterior fossa abnormalities, focusing only on full-term neonates are limited. This article describes the technique of mastoid fontanelle ultrasonography in full-term neonates and the features of posterior fossa abnormalities that may be encountered in various neonatal disorders and conditions, combined with subsequent MRI in the same patients. Cranial ultrasound through the mastoid fontanelle plays a pivotal role in the early detection of posterior fossa pathology and selection of neonates with an indication for MRI.

Neuroimaging biomarkers of preterm brain injury: toward developing the preterm connectome

For typically developing infants, the last trimester of fetal development extending into the first post-natal months is a period of rapid brain development. Infants who are born premature face significant risk of brain injury (e.g., intraventricular or germinal matrix hemorrhage and periventricular leukomalacia) from complications in the perinatal period and also potential long-term neurodevelopmental disabilities because these early injuries can interrupt normal brain maturation. Neuroimaging has played an important role in the diagnosis and management of the preterm infant. Both cranial US and conventional MRI techniques are useful in diagnostic and prognostic evaluation of preterm brain development and injury. Cranial US is highly sensitive for intraventricular hemorrhage (IVH) and provides prognostic information regarding cerebral palsy. Data are limited regarding the utility of MRI as a routine screening instrument for brain injury for all preterm infants. However, MRI might provide diagnostic or prognostic information regarding PVL and other types of preterm brain injury in the setting of specific clinical indications and risk factors. Further development of advanced MR techniques like volumetric MR imaging, diffusion tensor imaging, metabolic imaging (MR spectroscopy) and functional connectivity are necessary to provide additional insight into the molecular, cellular and systems processes that underlie brain development and outcome in the preterm infant. The adult concept of the "connectome" is also relevant in understanding brain networks that underlie the preterm brain. Knowledge of the preterm connectome will provide a framework for understanding preterm brain function and dysfunction, and potentially even a roadmap for brain plasticity. By combining conventional imaging techniques with more advanced techniques, neuroimaging findings will likely be used not only as diagnostic and prognostic tools, but also as biomarkers for long-term neurodevelopmental outcomes, instruments to assess the efficacy of neuroprotective agents and maneuvers in the NICU, and as screening instruments to appropriately select infants for longitudinal developmental interventions.

Sonographic imaging of the posterior fossa utilizing the foramen magnum

In this essay, we describe our experience with a sonographic technique utilizing the foramen magnum to more clearly define anatomy in the neonatal posterior fossa. This approach can be used as an additional problem-solving tool in neonates with post-hemorrhagic hydrocephalus and a variety of posterior fossa abnormalities. The foramen magnum view is easily mastered and produces diagnostic images with little additional scanning time.

The clinical presentation of preterm cerebellar haemorrhage

The objective of this study was to evaluate clinical symptoms and findings on cranial ultrasound (CUS) in preterm infants with cerebellar haemorrhage through retrospective analysis of all preterm infants with a postnatal CUS or MRI diagnosis of cerebellar haemorrhage admitted in a tertiary care centre between January 2002 and June 2009. Fifteen infants were identified; median gestational age was 25 2/7 weeks and median birth weight 730 g. We discerned six types of haemorrhage: subarachnoid (n = 3), folial (n = 1), lobar (n = 9, of which 4 bilateral), giant lobar (n = 1, including vermis) and contusional (n = 1). Especially in infants with lobar cerebellar haemorrhage, CUS showed preceding or concurrent lateral ventricle dilatation, mostly without intraventricular haemorrhage (IVH). Thirteen infants suffered from notable, otherwise unexplained motor agitation in the days preceding the diagnosis. In conclusion, motor agitation may be a presenting symptom of cerebellar haemorrhage in preterm infants. Unexplained ventriculomegaly can be a first sign of cerebellar haemorrhage and should instigate sonographic exploration of the cerebellum.

Cerebellar hemorrhage in extremely low birth weight infants: incidence, risk factors, and impact on long-term outcomes

Improvements in neuroimaging technology and techniques have contributed to the increased recognition of cerebellar hemorrhage (CBH) in the prererm infant. Studies have indicated that the extremely low birth weight (ELBW) infant (< 1,000 g) is at highest risk for this injury. Associated risk factors include a constellation of antenaral, intrapartum, and neonatal factors, with immaturity, fetal distress, and cardiorespiratory instability in the early neonatal course as significant contributors. The long-term impact of CBH for the ELBW infant is not fully understood, but recent reports suggest that, in addition to motor impairments, deficits in cognitive, language, and social-behavioral function are also apparent. This article reviews the current state of knowledge of cerebellar development, risk factors for injury, and long-term developmental consequences of injury. Implications for nursing practice, education, and research are discussed.

Neonatal cranial ultrasonography: how to optimize its performance

Cranial ultrasonography (CUS) is an excellent and non invasive tool for brain imaging during the neonatal period. It is traditionally performed through the anterior fontanel. Although the advantages of CUS are numerous, there are also diagnostic limitations. Alternative imaging techniques including the use of different transducer types and frequencies and of additional acoustic windows can improve image quality and the diagnostic accuracy of CUS. This review will focus on techniques to be applied for optimizing the performance of CUS in the newborn infant.

Neuroimaging and neurodevelopmental outcomes in preterm infants

Imaging of the preterm infant brain has advanced dramatically beyond the earliest era of transillumination. Computed tomography (CT), a crucial innovation during the early 1970s, allowed noninvasive visualization of intracerebral lesions, particularly hemorrhage. The capability to document brain injury in the preterm infant led to better clarification of links to developmental outcomes. With the development of cranial ultrasound (CUS), and more recently, magnetic resonance imaging (MRI), CT is used rarely for imaging the brain of preterm infants. Despite extensive experience with neonatal neuroimaging, significant questions still remain. Substantial controversies exist pertaining to when and how neuroimaging should be performed and how images should be interpreted.

Using cerebral ultrasound effectively in the newborn infant

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.

Mastoid fontanelle approach for sonographic imaging of the neonatal brain

This pictorial review describes in detail the examination technique used to study the neonatal brain via the mastoid fontanelle and offers a panoramic view of the anatomical structures that can be identified in each US slice. The brain lesions are grouped as congenital malformations, haemorrhage, cerebellar lesions and sinus venous thrombosis. In each section, the additional information obtained through the mastoid fontanelle is provided.

Sonographic maturation of third-trimester cerebellar foliation after birth

The development of cerebellar folia of third-trimester preterms has not been described with ultrasound before. We set out to determine normal development of the pons and cerebellar folia for future measurements of hypoplasia and atrophy. Study sonograms were made in preterms admitted to the neonatal intensive care unit with postmenstrual age (PMA) from 25 wk until term. On a weekly basis, transcranial measurements were made in the axial and coronal planes at the asterion with high-frequency transducers (8.5 and 13 MHz). The axial images showed the pons and fourth ventricle. The coronal images showed cerebellar folia and white matter. In the same coronal plane, the depth of cerebellar fissures at the rostral cerebellar convexity could be observed. A total of 172 cranial sonograms were performed on 98 neonates. The development of folia could be measured with ultrasound through the asterion. We showed that pons area, mean of three fissure depths, hemisphere area, and number of folia in the horizontal fissure correlated significantly with PMA. Hemisphere area described the same trend of growth as the transverse cerebellar diameter used in fetal sonography.

Ultrasound abnormalities preceding cerebral palsy in high-risk preterm infants

OBJECTIVE

To assess sequential high-resolution cranial ultrasound (US) in high-risk preterm infants to predict cerebral palsy (CP).

STUDY DESIGN

Preterm infants were prospectively studied (n=2139), 1636 <or=32 weeks gestational age (GA) (group A) and 503 with a GA of 33 to 36 weeks (group B). US was performed once a week until discharge and at 40 weeks postmenstrual age (PMA), using a 7.5-MHz transducer. Grade III and IV hemorrhage, cystic periventricular leukomalacia (c-PVL), and focal infarction were considered major US abnormalities. A diagnosis of CP was made at a minimum age of 24 months.

RESULTS

Seventy-six (5%) of the 1460 survivors in group A developed CP. US abnormalities were present in 70 of 76 (92%) infants, being major in 58 (83%) and minor in 12 (17%). In 29% of the CP cases with major US abnormalities, cysts were first detected beyond day 28. A further 6 infants without US abnormalities developed CP, and 3 of these infants developed ataxic CP. Twenty-nine (6%) of the 469 survivors in group B developed CP. US abnormalities were present in 28 of 29 (96%) infants, being major in 25 (89%) and minor in 3 (11%). One infant without US abnormalities developed CP. Considering the major US abnormalities, a specificity of 95% and 99% and a sensitivity of 76% and 86% were found for group A and B, respectively. The positive predictive value was 48% in group A and 83% in group B.

CONCLUSION

Seventy-nine percent of our CP cases had major US abnormalities. To detect c-PVL, the most predictive US marker for CP, sequential scans with a 7.5-MHz transducer are required.

Transrectal ultrasonography for problem solving after transvaginal ultrasonography of the female internal reproductive tract

OBJECTIVE

To report the value of transrectal ultrasonography of the female internal reproductive tract as a complementary problem-solving technique after transvaginal ultrasonography in selected patients. To date, transrectal ultrasonography of the female internal reproductive tract has been advocated in lieu of transvaginal ultrasonography for women in whom transvaginal ultrasonography cannot be performed for various reasons.

METHODS

Ten illustrative cases are presented of women for whom transrectal ultrasonography performed after transvaginal ultrasonography provided additional clinically important information regarding the female internal reproductive tract.

RESULTS

Transrectal ultrasonography was helpful in 2 scenarios: (1) women with a retroverted uterus in whom the endometrial stripe was virtually parallel to the ultrasound beam and thus could not be properly measured on transvaginal ultrasonography, and (2) women in whom normal or pathologic adnexal findings were distant from the vagina or obscured by intervening structures during transvaginal ultrasonography but were near the rectum or not obscured during transrectal ultrasonography. In 1 case, transrectal ultrasonography yielded a diagnosis of ectopic pregnancy that was missed prospectively on transvaginal ultrasonography because pain severely limited the examiner's ability to manipulate the transvaginal ultrasound transducer.

CONCLUSIONS

Transrectal ultrasonography of the female internal reproductive tract can provide clinically useful information to complement transvaginal ultrasonography in selected patients.

Posterior fossa abnormalities seen on magnetic resonance brain imaging in a cohort of newborn infants

OBJECTIVE

To describe the nature and frequency of posterior fossa (PF) lesions in infants who underwent magnetic resonance (MR) brain imaging in the neonatal period and to correlate with cranial ultrasound (CUS) findings and clinical outcome.

STUDY DESIGN

A retrospective review of all neonatal MR brain imaging from 1996 to 2001 (n=558). MR images, CUS and case notes were reviewed in infants with PF abnormality.

RESULTS

A total of 20 infants had abnormalities in the PF, which represents 4.7% of abnormalities seen on MR. Out of 10, six term infants had PF extra-axial hemorrhage, three had cerebellar hypoplasia, while one had cerebellar hemorrhage. In the preterm, 8/10 lesions were unilateral; focal cerebellar hemorrhage was seen in 5/10 and extensive hemorrhage with secondary atrophy in 3/10. Out of 20, 17 infants also had supratentorial lesions. Out of 20, 19 had CUS performed, of which 7/19 showed PF abnormality.

CONCLUSION

Intracerebellar hemorrhage was more common in preterm infants than in term infants. These hemorrhages tended to be focal, unilateral and were associated with atrophy.

Intracranial neonatal neurosonography: an update

This article reviews salient features of a normal neonatal cranial ultrasound examination with suggestions concerning techniques that take advantage of new developments in ultrasound technology. It also illustrates pathologic findings in such areas as congenital abnormalities, intracranial hemorrhage, and infection. Recent publications on the subject of neurodevelopmental outcome are explored, pointing out how varying descriptions of intraventricular hemorrhages affect their results.

A new view of the neonatal brain: clinical utility of supplemental neurologic US imaging windows

Anterior fontanelle imaging has traditionally been the mainstay of neonatal cranial ultrasonography (US). However, this traditional approach has limited diagnostic accuracy, which has led to increasing use of two alternate neurologic US imaging techniques: posterior fontanelle imaging and mastoid fontanelle imaging. These alternate techniques can help detect pathologic conditions and structural malformations in the neonatal brain. Posterior fontanelle imaging allows improved detection of intraventricular hemorrhage. This technique better demonstrates subtle differences in echogenicity between clot and a choroid glomus and depicts clot extending into the occipital and temporal horns. Mastoid fontanelle imaging is particularly useful in detecting hemorrhage involving the brainstem, cerebellum, and subarachnoid cisterns. It greatly facilitates clot detection in the fourth ventricle and cisterna magna because the tissues surrounding these structures are normally echogenic. Mastoid fontanelle imaging can also help distinguish holoprosencephaly from aqueductal stenosis and identify small malformations of the posterior fossa. Color Doppler US may help identify normal variants such as calcar avis and lobular choroid plexus, and adjunct magnetic resonance imaging can help distinguish normal structures from a true Dandy-Walker variant. Use of posterior fontanelle imaging and mastoid fontanelle imaging can significantly augment the diagnostic power of neurologic US.

Sonographic assessment of posthemorrhagic ventricular dilatation

Sonography plays a key role in the initial evaluation and monitoring of ventricular dilatation in the newborn. The use of supplemental imaging approaches by the mastoid fontanelle and foramen magnum can help identify the cause and location of obstruction. Duplex Doppler of intracranial vessels during anterior fontanelle compression is a useful indicator of altered cranial compliance in these infants. Additional views of the thoracolumbar spine can help identify which infants will likely benefit from lumbar puncture for therapy of progressive ventricular dilatation.