Neonatal Neurosonography: A Pictorial Essay: Euroradiology
Neonatal Neurosonography: A Pictorial Essay: Euroradiology
Neonatal Neurosonography: A Pictorial Essay: Euroradiology
Correspondence: Dr. Venkatraman Bhat, 309, Greenwoods Apt, Royal Gardenia, Bommasandra, Bangalore ‑ 560 099, Karnataka, India.
E‑mail: bvenkatraman@gmail.com
Abstract
Neurosonography is a simple, established non‑invasive technique for the intracranial assessment of preterm neonate. Apart from
established indication in the evaluation of periventricular haemorrhage, it provides clue to wide range of pathology. This presentation
provides a quick roadmap to the technique, imaging anatomy and spectrum of pathological imaging appearances encountered
in neonates.
Introduction Indications
Sonographic examination of the neonatal brain remains an The main indication for this examination is the demonstration
invaluable assessment tool in experienced hands. Many or exclusion of an intracranial hemorrhage in a preterm
radiologists are not quite familiar with the spectrum of neonate. The technique is additionally used for the
imaging appearances of the neonatal intracranium due follow‑up of intraventricular hemorrhage (IVH)‑related
to inadequate exposure. Many specific clinical questions complications to look for evolving findings pertaining to
can be resolved by optimally utilizing this simple ischemia. Other broader indications include demonstration
informative tool. Portability of the study, lack of need of congenital structural anomalies, intracranial vascular
to transport baby to radiology services, and the wealth lesions, and also its use as a simple screening tool in the
of diagnostic information available from a large open exclusion of gross intracranial pathology.
anterior fontanelle makes this study a highly challenging
one. [1] This pictorial essay attempts to highlight the Cranial USG Technique
common indications for neurosonography, its basic
techniques, sonographic anatomy, and the spectrum There are essential steps to be followed before the
of pathological imaging appearances seen in neonates. procedure. Most of the examination is performed bedside
With an ever‑growing innovation in technique and an with the neonate within the incubator. Examination is
increasing affordability of state‑of‑the‑art equipment, preferably done through the cranial incubator opening.
there is a greater need for the radiological community to Care should be taken not to move the infant or to cause
be well acquainted with various facets of this diagnostic any disturbance to incubator temperature. Pressure over
tool. the anterior fontanelle is to be avoided, especially in a
critically ill premature neonate. All aseptic precautions
Access this article online are to be followed in accordance with the protocols of the
Quick Response Code: neonatal ICU.
Website:
www.ijri.org
Best results are obtained with a high‑frequency phased
array transducer (5-8 MHz) with a small footprint probe.
DOI: High‑resolution images are obtained in preterm neonates
10.4103/0971-3026.143901
by using probe frequency of 7.5 MHz. Technical difficulty
may be encountered in obtaining the best image in the case
Indian Journal of Radiology and Imaging / November 2014 / Vol 24 / Issue 4 389
Bhat and Bhat: Neonatal neurosonography: Pictorial essay
of a small anterior fontanelle [Figures 1 and 2]. Phased Screening via other supplemental fontanelle and obtaining
array transducers of small footprint and wide insonation high‑resolution images from them may have added value.
angle (up to 140°) help to obtain examination of diagnostic This technique has been shown to improve detection of
quality. posterior fossa hemorrhages and in the evaluation of the
transverse sinuses.[7] Mastoid and posterior fontanelle
Neurosonography starts with gray-scale imaging performed approaches are useful in the demonstration of a subtle
via the anterior fontanelle in the coronal and sagittal intraventricular bleed in the occipital horn, in patients
planes. [2‑4] Generally, six to eight coronal images are with suspected holoprosencephaly and demonstration of
obtained, beginning at the anterior frontal lobes and a minor bleed in the brain stem and adjacent cerebellum.[7]
extending to the occipital lobes posterior to the lateral To complete the examination, high‑resolution linear‑array
ventricle trigones[5] [Figure 3]. The transducer is then rotated transducer images are obtained for detailed interrogation
90° and five sagittal images are obtained, including a midline of the convexity subarachnoid space and superficial cortex
and two parasagittal views of right and left hemispheres as well as deeper brain structures.[3] Linear images can be
encompassing the peripheral cortex[4,5] [Figure 4]. Color adjunctively obtained via any fontanelle for the evaluation
Doppler images for arterial and venous structures may of underlying anatomical structure or vessels.
be obtained for the screening of vascular structures.[6]
Documentation of Doppler imaging of the circle of Willis Translation of brain anatomy to sonography needs
and the region of vein of Galen is an essential part of understanding of sonographic physical principles. The
the assessment [Figure 5]. Spectral tracing with peak general principles of sonography apply to intracranial
systolic velocity (PSV), end‑diastolic velocity (EDV), and study. Cerebrospinal fluid (CSF) spaces are anechoic,
resistive index (RI) need to be recorded for evaluation whereas the choroid plexus, small hemorrhages, and areas
of ischemia. Power Doppler imaging has also been of infarction appear hyperechoic. On ultrasonography
recommended by some authors to search for areas of (USG), gray matter tends to be hypoechoic and white
hyper‑ or hypo‑vascularity in suspected vascular occlusion, matter tends to be hyperechoic Secondly, the normal brain
ischemia, or infarction.[3] is always nearly symmetric. This fact allows for detection
Figure 3: Illustration of coronal USG examination, showing frontal and Figure 4: Illustration of sagittal and parasagittal USG examination,
posterior parietal planes showing mid-sagittal and ventricular planes
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of early changes of infarction or focal ischemia. Bilateral infarct.[9] Lastly, the periventricular white matter is normally
symmetric changes due to a systemic process may lead to homogeneous in echogenicity and is equally or less
errors in interpretation. A third fact involves interpretation echogenic than the adjacent choroid plexus.[4,6] Asymmetry
of visible layers of the normal cortex. The superficial pia or heterogeneity of the periventricular white matter is
mater should be seen as a thin, well‑defined hyperechoic suggestive of an abnormality, such as periventricular
layer immediately overlying the hypoechoic cortical gray leukomalacia (PVL). Normal anatomical illustrations are
matter, which in turn overlies the hyperechoic white shown in Figures 6‑9.
matter.[8].
An understanding of normal variation is essential
Failure to distinctly visualize these normal layers is to neurosonographic interpretation. Cavum septum
indicative of abnormalities such as focal hemorrhage or pellucidum is present in up to 50–61% of normal
neonates[10] [Figure 10]. Minor asymmetry in the frontal
horns or bodies of ventricles is often observed. Also, the
echogenicity of periventricular parenchyma is variable.
Being relatively echogenic in premature neonates, it
might be wrongly interpreted as PVL. Massa intermedia
can be quite variable in size in normal and pathological
conditions [Figure 11]. When posterior fontanelle approaches
are utilized, prominent calcar avis and lobulated glomus of
the choroid should be observed as normal variations.[7]
Intracranial Hemorrhage
Germinal matrix hemorrhage
One of the most important indications of neurosonography
is the demonstration of intracranial hemorrhage in a
premature infant. Routine screening cranial USG should
be performed in all infants of under 30 weeks gestation,
once between 7 and 14 days of age and should be optimally
Figure 5: Illustration demonstrating arterial and venous anatomy in repeated between 36 and 40 weeks postmenstrual age.[11‑13]
mid sagittal plane In term infants, non‑contrast computed tomography (CT)
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Figure 8: Coronal and parasagittal images of preterm (28 weeks) infant showing intracranial anatomy. Note the smooth surface of the immature
brain. Distribution of the lobes colored
A B
A B
Figure 10 (A, B): Coronal USG demonstrating cavum septum (star)
(A) and relation of vascular structures (B). Note that there are low-level
echoes of cerebral gray and white matter, with subtle differences in
the echoes of cortex and white matter. CSF spaces in Sylvian and
inter-hemispherical region (arrows) are hyperechoic. Cerebellum is
hyperechoic in relation to cerebral hemispheres
C D
Figure 9 (A-D): Doppler images (A and B) demonstrating circle of Willis.
Coronal USG demonstrating the vein of Galen. (C) Parasagittal study showing
the small periventricular veins in the region of caudothalamic groove (D)
A B
Figure 11 (A, B): (A) Sagittal USG demonstrating a relatively large
massa intermedia (arrow) (B) Illustrates the relatively hyperechoic Figure 12A: The figure demonstrates the location and the extent of
peritrigonal white matter(open arrow) in a normal neonate the germinal matrix (colored pink)
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is preferred. Areas of potential bleeding arise in the dilatation. Grade 3 hemorrhages show ventricular
zones of primitive germinal matrices, which are more extension and show minimal increase in the ventricular
extensive around the periventricular regions of the lateral dimensions [Figures 14 and 15]. Grade 4 hemorrhages,
ventricles and around the temporal horns [Figure 12A]. presently considered as venous infarct, present with a
The extent of germinal matrix diminishes with progressive predominant intraparenchymal component of hemorrhage,
maturity, limiting it to the region of caudothalamic often with a sizable mass effect [Figures 16‑19]. Posterior
groove. Germinal matrix hemorrhages are seen as areas of fossa hemorrhage is uncommon and can be demonstrated
increased echogenicity in the region of the caudothalamic when sizable. Hemorrhages of grade 3 and 4 are associated
groove. Germinal matrix hemorrhages were classified with neurological deficits or learning disability. [1]
into four categories by Papile based on the extent of Evolution of hemorrhage is demonstrated with follow‑up
hemorrhage [Figure 12B][14] [Table 1]. sonograms [Figure 20].
Figure 12B: Diagrammatic representation of IVH classification by Figure 13: Coronal and sagittal sonographic images demonstrating a
Papile (modified) grade 1 hemorrhage at the caudothalamic groove
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Structural information is easily available in premature Other anomalies that can be diagnosed using
and mature infants on sonography. Initial evaluation of neurosonography include Dandy–Walker syndrome
anomalies can be concluded with reasonable certainty. [Figure 33], agenesis of the corpus callosum
Hydrocephalus contributes to a large number of cases that [Figures 34 and 35], Arnold–Chiari malformation, and
can be diagnosed and followed up by neurosonography. vascular malformations. Unusual course of the anterior
Extent of hydrocephalus, level of obstruction, and thickness cerebral artery in cases of agenesis of the corpus callosum,
of the cerebral mantle can be obtained for subsequent described as sunburst appearance, can be conclusively
follow‑up. Biventricular, bifrontal ratio is measured at the shown by gray-scale and Doppler examination. Also,
level of foramen of Monro for quantitative follow‑up of
hydrocephalus [Figures 27 and 28]. Grossly dilated ventricular
A B
Figure 27 (A, B): Coronal illustration at the level of interventricular
foramen, showing the measurements for bifrontal/ventricular ratio Figure 28: Coronal images at two levels showing hydrocephalus
(A). USG in a patient with hydrocephalus showing measurement of secondary to germinal matrix hemorrhage on the left side. Note the
ventricular/bifrontal ratio (B) dilated third ventricle due to obstruction at the level of the aqueduct
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Figure 29: Severe hydrocephalus due to congenital aqueductal stenosis. Sagittal image (C) showing a dilated third ventricle and completely
collapsed fourth ventricle. Obstruction is at the level of aqueduct (arrow)
A B
Figure 30 (A, B): (A, B) Coronal and sagittal USG demonstrating severe
hydrocephalus in a patient with agenesis of the corpus callosum and
midline interhemispheric cyst (open arrows)
Figure 31: Severe hydrocephalus mimicking hydrancephaly. There
is a minimal residual cerebral mantle. Note the small posterior fossa
associated findings like colpocephaly and the additional
anomalies of the posterior fossa can be shown [Figure 35].
Hydrancephaly and severe hydrocephalus, although gross hydrocephalus.[7] Additional detailed information
easily demonstrated, cannot be distinguished with regarding the posterior fossa can also be obtained through
certainty on sonography alone. Dysplastic atrophic brain this route.
is occasionally seen on sonography. These lesions are seen
without the context of ischemia in the early perinatal Mineralizing Vasculopathy
period. Typically, the brain is small in size, hyperechoic
without differentiation of the gray and white matter, An appearance of linear bright branching streaks or patches,
and shows multiple cysts of varying size. Lesions are either unilaterally or bilaterally along the basal ganglia region
bilateral and often asymmetric [Figure 36A and B]. Direct is suggestive of mineralizing vasculopathy [Figures 38 and
examination over the cranial swelling can be performed 39]. These hyperechoic streaks resembling a branched
by sonography. Large cephaloceles [Figure 37], dermoid candlestick are due to the calcification of the walls of
cyst, and cephalhematoma can be diagnosed. the thalamostriatal and lenticulostriatal medium‑sized
perforating arteries, associated with wall hypercellularity,
Examination through the mastoid fontanelle can be intramural and perivascular deposition of amorphous
very useful in differentiating holoprosencephaly from basophilic material. Mineralizing vasculopathy is a
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A B
Figure 37 (A, B): Large occipital meningocele with multiple layers of
meninges and cystic cerebral parenchyma shown on USG (A). Coronal
examination showing the dysplastic cystic changes in the brain (B)
Vascular Lesions
A B
The dilated vessels of the arteriovenous malformations tend
Figure 36 (A, B): (A and B) USG images in two different patients
to appear as cystic lesions on neurosonography [Figure 40].
demonstrating dysplastic cerebral parenchyma with hyperechoic and
cystic parenchymal changes. Note the gross widening of CSF spaces Doppler images might also demonstrate dilated feeding
indicating loss of volume and draining vessels. The typical spectral pattern for
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A B
A B Figure 41 (A, B): (A) High-resolution images of the subarachnoid
spaces; normal high-convexity subarachnoid space is demonstrated
(yellow arrows). (B) Shows a dilated subarachnoid space with internal
echoes in a patient with pyogenic meningitis (black arrows)
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