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84
3 Neurosonography in Neonates, Infants and Children
a
Fig. 3.6 Mastoid access with sector transducer. ( a ) Posterior fossa, axial view; note large cistern
(↔). ( b ) Axial view at posterior horn (→) of lateral ventricle with haemorrhage (+ +) and respec-
tive plexus
b
3.2.3 Colour Doppler Sonography (CDS)
Transfontanellar :
• Anterior cerebral artery (ACA) and its branches (particularly the pericallosal)
and basilar artery (BA) – best seen in sagittal sections (Fig. 3.7a, c ).
• Circle of Willis with its major feeding arteries and draining veins – best seen in
coronal section (Fig. 3.7b, e ).
• Internal carotid artery (ICA) – in parasagittal or coronal section (Fig. 3.7b, d, e ).
NOTE : In patients who need cannulisation of CCA (e.g. for ECMO) or after CCA
injury, visualisation of anterior communicating artery is particularly important – if
seen, it indicates suffi cient collateralisation of affected ACA area. Liberally use
CDS, complemented by spectral analysis in relevant vessels.
Transtemporal
Most vessels of circle of Willis are visible (Fig. 3.8a ), particularly:
• Middle cerebral artery (MCA), proximal part of ACA (A1-segment).
• Proximal part of posterior cerebral artery (PCA), posterior and anterior commu-
nicating arteries.
• Depiction of (proximal) ICA, distal ACA and BA diffi cult or impossible.
• This view used for transcranial fl ow evaluation (Fig. 3.8b ).
Venous System
Most veins visible and better seen from transfontanellar access (Fig. 3.7f, g ), for
example:
• Superior sagittal sinus, inferior sagittal sinus, sinus confl uence (torcular hero-
phili), vein of Galen and sigmoid and transverse sinus.
• Large sinus of posterior fossa – additionally use mastoid or transtemporal
approach (Fig. 3.8c ).
NOTE : For assessment of large veins, transducers with suffi cient penetration at
lower frequencies may be necessary and fl ow seetings have to be adapted to low
fl ow velocities.
3.2 Normal Findings
a
85
b
c
f
Fig. 3.7 Major cerebral vasculature on aCDS. ( a ) Schematic drawing how to access the ACA/pericallosal
artery and the basilary artery (BA) in a sagittal section. ( b ) Schematic drawing how to access in a coronal
section. ( c ) Sagittal midline section, aCDS: BA, ICA, ACA and branches seen, duplex sample positioned in
pericallosal artery. ( d ) Parasagittal section CDS depicts the ICA when entering into intracranial portion. ( e )
Coronal CDS demonstrates both ICA as well as the branching into MCA and ACA. ( f ) CDS, coronal sec-
tion tilted occipitally: major veins/venous sinus of posterior fossa depicted (displayed in blue ) and branches
of PCA. ( g ) CDS in sagittal section to evaluate midline veins, particularly the superior sagittal sinus.
Abbreviations:( a ) CDS (amplitude) coded colour Doppler sonography, BA basilar artery, ICA internal
carotid artery, ACA anterior cerebral artery, MCA middle cerebral artery and PCA posterior cerebral artery
d e
g
Measurements
Arterial fl ow velocities as well as RI vary with age, but also with respiration, PCO 2 ,
intrathoracic pressure (crying, ventilation, etc.), cardiac function, heart rate, etc.
Cerebral autoregulation only intact in mature healthy brain – then peripheral vessels
show less dependent fl ow variations. General rule:
• Flow velocities increase with age, RI decrease with age (in childhood).
• Respiratory variation typical of venous fl ow may persist.
86
3 Neurosonography in Neonates, Infants and Children
a
b
c
Fig. 3.8 aCDS – transcranial/transtemporal access (TCI). ( a ) Major arteries of circle of Willis
depicted by aCDS. ( b ) The TCI view used to place sample gate for spectral analysis with a normal
bidirectional arterial fl ow pattern form left and right MCA in the lower part of the image. ( c ) CDS
on TCI/posterior fossa: veins/sinus of posterior fossa can be assessed
Preterms : fl ow velocities 20–40 cm/s, RI = 80–90 %.
Neonates : fl ow velocities 40–50 cm/s, RI = 75–80 % (see Table 3.2 ).
Older neonates and infants : assessed by transtemporal access. Flow velocities
increase; RI decreases to 60–70 %, eventually reach adult values by end of fi rst
year. Physiologic decrease of arterial diastolic velocity with consequent elevated
RI values in patients with persistent ductus arteriosus (PDA) or anaemia
(Table 3.3 ).
Functional Investigations
• Changes in fl ow spectrum, velocities and indices are observed with head positioning, particularly important for depicting infants at risk for sudden infant
death syndrome.
• Physiologic variations in fl ow velocities and RI indices with change of
PCO 2 – used to monitor cerebral perfusion and optimise respirator settings
(e.g. children under hyperventilation for treatment of brain oedema after
hypoxic events).
• Subtle mechanical fontanellar pressure used to assess effect on brain
perfusion – useful for assessment of critical intracranial pressure elevation
(e.g. hydrocephalus) (Fig.
3.9 ).
3.2 Normal Findings
Table 3.2 Brain: Normal values for fl ow velocities (cm/s) and Doppler indices in ACA, ICA
and BA in newborns
ACA BA
Vs 42 + 15 41 + 16 50 + 15
Ves 19 + 8 18 + 7 19 + 7
Ved 11 + 5 11 + 4 11 + 4
TAV 13 + 5 12 + 5 14 + 4
TAMX 21 + 9 19 + 7 22 + 6
RI 0.73 + 0.08 0.72 + 0.09 0.77 + 0.08
PI 2.7 + 0.9 2.7 + 0.7 3.0 + 0.8
Adapted from Deeg KH (1989) Zerebrale Dopplersonographie im Kindesalter. Springer/
Heidelberg, Berlin/New York; Deeg KH, Rupprecht T (1989) Pulsed doppler sonographic measurement of normal values for the fl ow velocities in the intracranial arteries of healthy newborns.
Pediatr Radiol 19:71–78
Abbreviations: ACA anterior cerebral artery, BA basilar artery, ICA internal carotid artery, PI
Pulsatility Index (Vs-Ved/TAV), RI Resistance Index (Vs-Ved/Vs), TAMX time average maximal
velocity, TAV time average fl ow velocity, Ve d end-diastolic velocity, Ve s end systolic velocity and
Vs maximal systolic velocity
ICA
87
• Differences in fl ow velocity and RI values between intra- and extracranial
portion of ICA used to demonstrate normal, slightly or signifi cantly elevated
brain pressure (see hydrocephalus).
3.2.4 Normal Variances in Preterm Babies
3.2.4.1 Periventricular Echogenicities
Physiologically reduced differentiation between gray and white matter due to
immaturity; central nonmyelinated white matter can be relatively echogenic, particularly in periventricular areas.
Periventricular white matter is frequently homogeneously and slightly increased
in echogenicity (often symmetric) in severely premature and very immature neonates (i.e. “PVE” = periventricular echodensity) (Fig. 3.10 ).
NOTE : Findings often diffi cult to differentiate from early hypoxic-oedematous
changes that eventually may lead to periventricular leukomalacia (PVL).
Immature brain also exhibits reduced gyration and prominent CSF spaces (intra-/
extra-axial); embryologic cavities can persist and may be remarkably prominent,
with high-resolution transducers radiate coron depictable (Fig. 3.11 ).
3.2.4.2 Ventricular Asymmetry
To a certain extent, this can be seen as normal variant – does not always indicate
pathology.
88
Table 3.3 Brain: Normal values for fl ow velocities and Doppler indices on TCI-Doppler
investigations
Age
Flow
velocity Artery
Vs
(cm/s)
Ved
(cm/s)
RI MCA 0.47 ± 0.05 0.55 ± 0.05 0.50 ± 0.05 0.53 ± 0.05 0.56 ± 0.06
Adapted from Bode H (1998) Pediatric applications of transcranial Doppler sonography. Springer,
Wien New York, 1988; Krejza J, Mariak Z, Walecki J, Szydlik P, Lewko J, Ustymowicz A (1999)
Transcranial color Doppler sonography of basal cerebral arteries in 182 healthy subjects: age and
sex variability and normal reference values for blood fl ow parameters. AJR 172:213–218
Abbreviations: Vs maximal systolic velocity, Ve d end diastolic velocity, MCA middle cerebral
artery, ACA anterior cerebral artery, ICA internal carotid artery, PCA1 posterior cerebral artery,
fi rst segment and BA basilar artery
Normal age-dependent Resistance Index ( RI ) values and normal fl ow velocities (cm/s) ± sd for
systole ( Vs ), end diastole ( Ve s ) on TCI. Time average mean velocity ( TAV ) and Pulsatility Index
( PI ) less important and not listed
MCA 124 ± 10 147 ± 17 143 ± 13 129 ± 17 110 ± 28
ACA 81 ± 19 104 ± 22 100 ± 20 92 ± 19 79 ± 21
ICA 118 ± 24 144 ± 19 140 ± 14 125 ± 18
PCA1 67 ± 18 84 ± 20 82 ± 11 75 ± 16 71 ± 16
ICA
(siphon)
BA 71 ± 6 88 ± 9 85 ± 17 68 ± 11
MCA 65 ± 11 65 ± 9 72 ± 9 60 ± 8 49 ± 14
ACA 40 ± 11 48 ± 9 51 ± 10 46 ± 11 35 ± 11
ICA 58 ± 5 66 ± 8 68 ± 10 59 ± 9
PCA1 36 ± 13 40 ± 12 42 ± 7 39 ± 8 33 ± 14
ICA
(siphon)
BA 35 ± 6 41 ± 5 44 ± 8 36 ± 7
ACA 0.55 ± 0.05 0.57 ± 0.05 0.57 ± 0.05 0.58 ± 0.05 0.56 ± 0.07
ICA 0.52 ± 0.05 0.60 ± 0.05 0.55 ± 0.05 0.58 ± 0.05
PCA1 0.55 ± 0.05 0.58 ± 0.05 0.55 ± 0.05 0.55 ± 0.05 0.54 ± 0.06
ICA
(siphon)
BA 0.55 ± 0.05 0.60 ± 0.05 0.55 ± 0.05 0.57 ± 0.05
1–2.9 years 3–5.9 years 6–9.9 years
114 ± 21 138 ± 14 132 ± 17 120 ± 21
55 ± 12 62 ± 8 67 ± 11 58 ± 12
0.57 ± 0.05 0.63 ± 0.05 0.55 ± 0.05 0.58 ± 0.05
3 Neurosonography in Neonates, Infants and Children
10–17.9 J
years Adults
Fig. 3.9 Transtemporal DS tracing while applying
fontanellar pressure. Duplex Doppler gate placed in
main MCA branch on a TCI-Doppler acquisition.
Note : Reduction of fl ow velocities when slight
fontanellar compression is applied by fi nger tip
3.2 Normal Findings
89
Fig. 3.10 PVE in preterm infant. Typical increased paraventricular echogenicities (“PVE”) in
severely immature brain of preterm baby. ( a ) Parasagittal section maybe the slightly pathy appearence
may indicate early PVL - only to be decided on follow-up. ( b ) Coronal view tilted occipitally
a
b
3.2.4.3 Ventriculomegaly
Term neonates: ventricles measuring 5–10 mm (at level of foramen of Monro)
called ventriculomegaly.
In older children: ventriculomegaly without other signs of hydrocephalus measuring up to 1.5 cm axial diameter.
3.2.4.4 Cisterna Magna
Size quite variable (range 2–10 mm). Large posterior fossa CSF spaces more common in preterms (Fig. 3.11d, e ).
NOTE : Sometimes differentiation of large cistern (mega cisterna magna) versus
arachnoid cyst or Dandy-Walker “pseudocyst” diffi cult or impossible.
3.2.4.5 Vascular Variations
Many anatomic variations of brain vessels without pathologic implications are
known, only some detectable by CDS.
NOTE : Many systemic or cardiac conditions may infl uence Doppler fi ndings, e.g.
heart malformations with shunt, cardiac insuffi ciency, heart rate, drugs, hypo- and
hypervolaemia, anaemia, dehydration, hyperviscosity, altered respiration, PCO 2
and increased intrathoracic pressure (Fig. 3.12 ). Furthermore, extracranial condi-
tions or position may affect perfusion pattern in cerebral vessels (e.g. SIDS risk in
infants with altered BA fl ow when head is extremely turned to the one or other
side). Thus, not all altered spectral Doppler fi ndings indicate brain disease or cerebral vascular problems; however, they may hint at potential perfusion disturbances
with neurologic sequelae secondary to another underlying condition. Sometimes
CDS is used to grade these conditions in terms of therapeutic needs (i.e. grading
of PDA).
90
3 Neurosonography in Neonates, Infants and Children
a
c
b
d
e
Fig. 3.11 US appearance in preterm babies – typical features and fi ndings. ( a ) Parasagittal sec-
tion – wide CSF space (+ +). ( b ) Coronal section: reduced gyration + prominent periventricular
echoes with echogenic lines of the corona radiata. ( c ) Sagittal midline view: physiologically per-
sisting cavum septi pellucidi et vergae. ( d ) Coronal midline section, posterior fossa: large cisterna
magna. ( e ) Sagittal midline section, posterior fossa: prominent CSF space (cisterna magna)
3.2 Normal Findings
a
91
b
d
e
c
Fig. 3.12 Impact of heart rate and extracranial conditions on Doppler fi ndings: different fl ow
pattern, RI and V
dia, whereas diastolic velocity decreases. ( b , c ) Flow alteration in BA when head is turned
(“Drehung”) – normal fl ow in normal position (“Gerade”). ( d ) Retrograde fl ow (encoded in
blue ) in left vertebral artery in subclavian steal Syndrome. Duplex trace confi rmation, in this
example in a baby after ALTE (acute life threatening event) during extensive head turning, with
consequently inverted fl ow direction of basilar artery (encoded in blue ) ( e )
( a ) Diastolic velocity changes with heart rate - RI increases with bradycar-
diast.
92
3 Neurosonography in Neonates, Infants and Children
3.3 Pathologic Findings
3.3.1 Neural Tube Defects
3.3.1.1 Anencephaly
Most severe malformation, diagnosed prenatally. No postnatal indication for US.
3.3.1.2 Meningomyelocele and Encephalocele
Herniation of meninges, brain parenchyma and/or spinal cord tissue through defect
in osseous containment (skull, spine), parts of CSF system and ventricles can herniate as well.
US Finding
Bone defect detectable using high-resolution transducers or by transtemporal
approach-from contralateral side. The anechoic CSF space protrudes into defect
with variable amounts of brain herniation depending on amount and kind of defect
and malformation (Fig. 3.13a ).
3.3.1.3 Arnold Chiari Malformation
Usually associated with spinal myelo(meningo-)celes (see spine US), with subsequent disturbed relation of midline structures, particularly in posterior fossa.
Typically the cerebellar vermis protrudes through foramen magnum to cervical spinal level (Fig. 3.13b ).
Classifi cation and US Findings
Depending on nomenclature: grade I to grade III, trying to categorise minimal
fi ndings:
• Type I: no dysraphic malformation and only slight caudalisation of lower parts of
cerebellum to foramen magnum.
• Type II: spinal dysraphism often combined with CSF circulation problems caus-
ing hydrocephalus.
• Type III: most severe form – occipito-cervical encephalocele.
ab
Fig. 3.13 Cerebral manifestations of neural tube defects. ( a ) Linear transducer on the occipital
skull: small osseous defect depicted with herniation of fl uid-fi lled meningeal pouch, consistent
with a small occipital meningocele. NOTE: No brain content. ( b ) Curved array, sagittal view from
nuchal approach, neck bent anteriorly: slightly herniated cerebellar vermis (+ +) in Arnold Chiari
syndrome
3.3 Pathologic Findings
93
• Associated malformations: agenesis of septum pellucidum, pronounced massa
intermedia, atypical thickened choroid plexus of lateral ventricle, hypodysplasia
of cerebellum and agenesis or hypoplasia of corpus callosum.
3.3.1.4 Dandy-Walker Malformations
Variable cystic malformation in posterior fossa, associated with atypical shape and
size of posterior fossa + cerebellar hypoplasia.
US Findings :
• Enlarged posterior fossa, dilatation of fourth ventricle, dysgenesis of cerebellar
vermis and associated hydrocephalus with diverging posterior horns.
• Variety of other associated central nervous systems malformations.
Dandy-Walker variant :
Minimal variation of same fi ndings with dysgenesis of vermis and cystic dilatation of fourth ventricle without enlargement of posterior fossa, potentially enlarged
posterior fossa CSF space.
3.3.1.5 Corpus Callosum Malformations
Dysgenesis of partial or total agenesis of corpus callosum.
US Findings :
• Lack of visualisation of entire or parts of corpus callosum as well as the cingulate
gyrus.
• Radial diverging sulci reaching to roof of third ventricle (Fig. 3.14 ).
• Atypical impression of frontal horns of lateral ventricle: lateralised, steerhorn
shape in coronal view.
• Colpocephalic confi guration of posterior horns. Elevation of roof of third ventricle.
• Minimal forms: only regional thinning or discontinuity of corpus callosum.
• Associated malformations, for example: arachnoid cyst, Arnold Chiari and vari-
ous syndromes (Trisomia 8, 13, etc.).
NOTE : Subtle partial agenesis or dysgenesis of corpus callosum more diffi cult to
visualise on US. Clue to diagnosis – atypical form of cingulate gyrus in respective
area, close contact of radially diverging sulci – use coronal view.
Fig. 3.14 Agenesis of corpus callosum. Sagittal
view: no corpus callosum seen. Gyri reach roof of
third ventricle, no gyrus cingulum; additional CDS
and duplex fl ow spectrum of pericallosal artery
which also runs directly on roof of third ventricle