Review developmental anatomy of the brain and intracranial vascular structures.
Identify the sonographic appearance of the normal brain in neonates and infants.
Describe the systematic evaluation of the neonatal brain.
Discuss Doppler evaluation of intracranial vessels.
Describe the physiologic and maturation differences in the sonographic appearance of the preterm and term neonatal brain.
Illustrate ischemic injury of the preterm and term infant.
Identify the risk factors for the development of an intracranial hemorrhage (ICH) and illustrate the sonographic appearance of ICH.
Describe the mechanism, etiologies, and sonographic appearance of hydrocephalus.
Identify types of traumatic hemorrhage including birth trauma and non-accidental injury.
Identify ultrasound findings in the setting of congenital infections.
List common pathologies including congenital malformations of the brain that can be visualized sonographically.
Describe the evaluation of cranial sutures to assess for craniosynostosis.
posterior portion of the brain composed of two hemispheres; lies below the tentorium
surrounds the brain and the spinal cord to protect the brain and spinal cord from injury
largest section of the brain; divided into two hemispheres joined by the corpus callosum
echogenic cluster of cells located within the lateral ventricles responsible for the production of CSF
largest white matter structure in the brain; contains nerve tracts that allow communication between the right and left hemispheres of the brain
fold of dura mater that divides the two hemispheres of the brain
soft spot between the cranial bones; anterior, posterior, and mastoid fontanelles are used as acoustic windows during sonographic examination of the neonatal brain
various infolds of the cerebral cortex, surrounded by sulci
lack of oxygen
human baby 1 month to 1 year of age
membranous coverings of the brain and spine
human baby less than 1 month of age
cyst or cavity in the brain usually as a result of a destructive lesion
linear structures that separate gyri
fibrous, immovable joints that connect the skull bones
paired ovoid structures in the central brain responsible for relaying nerve impulses and carrying sensory information into the cerebral cortex
located in the center of the brain, one beneath each cerebral hemisphere, next to the third ventricle. The thalami can be thought of as relay stations for nerve impulses carrying sensory information into the cerebral cortex.
beam thickness effect and will often allow visualization of the normal third ventricle. When dilated, it can be imaged quite easily. Continuing with further posterior angulation, the echogenic CP can be seen in the floor of the lateral ventricle and in the roof of the third ventricle. This scan is slightly posterior to the third ventricle. The echogenic V-shaped tentorium can be seen in this scan anterior to the cerebellum. Posterior to the vermis of the cerebellum is the CM. The Y-shaped Sylvian fissure can also be seen in this plane (Fig. 21-4). With more posterior angulation, the next scan demonstrates the echogenic star-shaped quadrigeminal cistern posterior to the thalami. Posterior to the tentorium is the posterior fossa containing the echogenic cerebellum (Fig. 21-5).
sulci, which contains the pericallosal artery. The vascular pulsations from these vessels can be appreciated on real-time imaging. Inferior to the corpus callosum is the third ventricle. Anterior to the echogenic vermis of the cerebellum is the triangular-shaped fourth ventricle. The moderately echogenic midbrain is anterior to the fourth ventricle, and the echogenic cerebellar vermis is posterior to the fourth ventricle (Fig. 21-9). The CM is seen inferior to the vermis and should always be visualized. Absence of the CM is indicative of pathology. Parasagittal images are obtained by angling the transducer from the midline through the right and left cerebral hemispheres from medial to lateral (or lateral to medial). The main anatomic landmark in the next image is the caudothalamic groove. The anterior extent of the CP tapers to a point into this groove, which is formed by the head of the caudate nucleus anteriorly and the thalamus posteriorly. The head of the caudate nucleus is slightly more echogenic than the thalamus. In the premature neonate, the fragile germinal matrix (GM) is located in these areas and is a common site for hemorrhage (see further discussion under the section on Intracranial Hemorrhage). This is an area where a magnified image plane is recommended (Fig. 21-10). With continued angulation laterally, the next image is through the lateral ventricle. The frontal horn of the lateral ventricle is more medial than the occipital horn; thus, to visualize the entire ventricle, the anterior part of the transducer needs to be angled obliquely with the front end of the transducer angled medially and the posterior part angled slightly more lateral. This parasagittal section will visualize a good portion of the frontal horn and body of the lateral ventricle. The thalamus is seen inferior to the head of the caudate nucleus, and the CP should taper into the caudothalamic groove (Fig. 21-11). Angling more laterally, the highly echogenic glomus of the CP is seen filling the trigone of the lateral ventricle and has a comma-shaped configuration because it courses posterior toward the temporal horn (Fig. 21-12). There should be no CP extending anterior to the third ventricle or into the occipital horn. Several images may be needed to image the complete ventricular system. The temporal horn or occipital horn will need to be imaged separately because it is not always possible to
line up the entire ventricular system in one plane. In a nondilated ventricular system, the temporal and occipital horn may be difficult to visualize. As on the coronal section, the periventricular white matter lateral and posterior to the trigones of the lateral ventricles requires careful evaluation. This area should not be brighter than the CP. Angling more lateral to the ventricle, the next scan demonstrates the far lateral periventricular white matter tracts and the echogenic Sylvian fissure. On real-time scanning, the middle cerebral artery (MCA) branches can be seen pulsating within this fissure (Fig. 21-13).3
FIGURE 21-7 Occipital lobes. Coronal image taken posterior to the occipital horns of lateral ventricles shows the normal echogenic periventricular white matter (arrows) and the occipital cortex.
FIGURE 21-8 Sagittal scan planes. Sagittal/parasagittal imaging planes via the anterior fontanelle approach.
conditions and structural malformations in the brainstem, cerebellum, and subarachnoid cisterns. The PF provides an enhanced view of the glomus of the CP, its extension into the body and temporal horn of the ventricle. It allows better visualization of the occipital horn, facilitating the detection of intraventricular blood clot from normal structures, like the calcar avis (Fig. 21-14). The MF depicts a superior view of the cerebral peduncles, thalamus, quadrigeminal cistern, cerebellar hemispheres, vermis, and the CM by avoiding the echogenic tentorium (Fig 21-15).
intracranial pressure, asphyxia, brain injury, and brain death. Doppler may be performed through the anterior fontanelle or transtemporal, through the sphenoid fontanelle (Fig. 21-18). Placing probe 1 cm anterior and superior to the tragus of the ear enables access to the circle of Willis, a ring of vessels that sit at the base of the brain. It is formed anteriorly by the internal cerebral artery (ICA) as it terminates into the MCA, anterior cerebral artery (ACA), and posterior communicating artery (Fig. 21-19) and joins with the vertebrobasilar system, composed of the vertebral and basilar arteries. The role of the circle of Willis is to supply collateral circulation and decrease blood pressure, through pressure equilibrium, in the brain. The MCA provides approximately 80% of blood to the cerebral hemispheres. The ACA and pericallosal artery are well seen through the anterior fontanelle, whereas the MCA is best evaluated from the transtemporal acoustic window (owing to the parallel angle of insonation). The resistive index (RI) (defined as PSV – EDV / PSV) is influenced by several factors, including peripheral vascular resistance, blood volume, and flow velocity. An increase in diastole will result in a decreased RI, whereas a decrease in diastole will result in an increased RI. Resistive indices decrease from full-term to preterm neonates owing to the maturation of cerebrovascular autoregulation (Table 21-1). Larger cerebral arterial vessels typically yield values between 0.71 and 0.80 in most neonates; resistive indices may also be influenced by a variety of conditions related to hemodynamics (Table 21-2).2
Venous drainage of the brain can be assessed by imaging the veins and dural venous sinuses. Superficial veins empty into the SSS and lie on the surface of the cerebral hemispheres. Deep veins, including the internal cerebral vein and vein of Galen (VoG), drain into the straight sinus. Optimization of the Doppler technique is key in obtaining diagnostic information.
FIGURE 21-16 Color Doppler. Normal sagittal color flow midline image depicting the anterior cerebral artery (ACA), internal carotid artery (ICA), basilar artery (BA), and pericallosal artery (arrow) as it courses over the corpus callosum.
FIGURE 21-18 Normal arterial spectral Doppler flow pattern of the anterior cerebral artery (ACA) (A) and middle cerebral artery (MCA) (B).
FIGURE 21-19 Transtemporal view of the circle of Willis. A: Anterior cerebral artery (ACA—A1 segment), middle cerebral artery (MCA—M1 segment), posterior cerebral artery (PCA). B: MR (Magnetic Resonance) angiogram depicting the circle of Willis.
TABLE 21-1 Normal Arterial Doppler Hemodynamics in the Newborn (ACA)
TABLE 21-2 Conditions that Influence the Resistive Index