Diagnostic ultrasound ( PDFDrive )

CHAPTER 45 Neonatal and Infant Brain Imaging 1517
A B C
FIG. 45.6 Normal Paramedian Sagittal Anatomy. (A) Schematic drawing. B, Body of lateral ventricle; CB, cerebellum; CN, caudate nucleus;
CP, choroid plexus; CTG, caudothalamic groove; F, frontal lobe; FH, frontal horn; O, occipital lobe; OH, occipital horn; P, parietal lobe; SF, sylvian
issure; T, thalamus; TH, temporal horn. (B) Sagittal sonogram, paramedian view. Black C, Choroid plexus; FL, frontal lobe; P, parietal lobe; T, thalamus;
white c, caudate nucleus; arrow, caudothalamic groove. (C) Parasagittal sonogram of cerebral cortex.
recognize, because this is the most common site of germinal
matrix hemorrhage (GMH) in the subependymal region of the
ventricle.
More pronounced lateral angulation will demonstrate the
peripheral aspect of the ventricles and the more lateral cerebral
hemisphere, including the temporal lobes (see Fig. 45.6C) where
the MCA branches extend toward the ventricle.
Sagittal sonography almost always reveals a normal hyperechoic
peritrigonal blush 21 in the parietal lobe just posterior and superior
to the ventricular trigones on parasagittal views (see Fig. 45.6B).
It is caused by the interface of numerous parallel ibers that are
perpendicular to the longitudinal angle of the ultrasound beam
passing through the anterior fontanelle. his is an anisotropic
efect artifact that occurs when the beam is perpendicular to
the ibers through the anterior fontanelle. A similar area of
increased echogenicity is not seen on sonograms obtained through
the posterior fontanelle, because with that angulation, the long
axis of the ultrasound beam and the iber tracts are almost
parallel.
Posterior Fontanelle Imaging
Posterior fontanelle imaging is very useful to evaluate the occipital
horns for the diagnosis of intraventricular hemorrhage (IVH).
he posterior fontanelle lies in the midline at the junction of
the lambdoid and sagittal sutures; it is open only until about 3
months of age 22 (Fig. 45.7). he transducer should be angled
slightly of midline with the anterior portion of the probe
directed slightly medially, to demonstrate the lateral ventricular
trigone with its occipital horn in the near ield (Fig. 45.8). he
choroid glomus will be seen with extensions into the ventricular
body and temporal horn. he occipital horn does not contain
choroid plexus and should be completely anechoic. Angling the
transducer into the let and right parasagittal planes will display
each occipital horn. hese planes are extremely useful for detecting
dependently layering clot and clot attached to the choroid
plexus.
Anterior Fontanelle
Posterior Fontanelle
Mastoid Fontanelle
FIG. 45.7 Acoustic Windows: Anterior, Posterior, and Mastoid
Fontanelles.
Mastoid Fontanelle Imaging
he mastoid fontanelle allows assessment of the brainstem and
posterior fossa, which are not well demonstrated in the standard
planes through the anterior fontanelle. he ultrasound transducer
is placed about 1 cm behind the helix of the ear and 1 cm above
the tragus. he mastoid fontanelle is located at the junction of
the squamosal, lambdoidal, and occipital sutures (see Fig. 45.7,
Video 45.3). Posterior fossa axial images, with the anterior portion
of the transducer angled slightly cephalad, will demonstrate the
fourth ventricle, posterior cerebellar vermis, cerebellar hemispheres,
and the cisterna magna. hese axial images should be
displayed with the top of the head to the let (Fig. 45.9). he
radiating folia of the cerebellar hemispheres contain relatively
hypoechoic neural tissue and are surrounded by echogenic
leptomeninges in the multiple cerebellar issures. 23 In the roof
of the fourth ventricle lies the normal echogenic fourth ventricular
choroid plexus. 24 Behind the fourth ventricle is the