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94
3 Neurosonography in Neonates, Infants and Children
3.3.1.6 Lipoma
Typically at corpus callosum or in midline at roof of third ventricle, not associated
with other callosal malformations.
US Appearance :
• Echogenic space-occupying lesion.
3.3.2 Migration and Gyration Alterations and Disturbances
General Remarks
Any disruption of normal radiating migration of neurons from germinal matrix to
peripheral cortex (caused by infection, ischemia metabolic reasons, etc.) can cause
severe malformations and clinical sequelae:
• Most sensitive imaging technique for assessing migration disturbances, heteroto-
pia and similar phenomena: MRI.
• US used as initial tool, may depict gross changes both of gyration as well as
echotexture of affected parenchyma – indicating further imaging.
• Many more malformations and anomalies exist than mentioned – not listed
below as either rare (e.g. brain stem discontinuation, Fig. 3.15a ) or sonographi-
cally diffi cult or impossible to diagnose.
3.3.2.1 Lissencephaly, Pachygyria, Macro- or
Polygyria and Colpocephaly
Defi nition and US Findings :
• Disruption of normal gyration, focally or more extensive.
• Can be completely missing (agyria) or altered, showing many tiny gyri (polymi-
crogyria), few unusually fl at gyri (pachygyria) or enlarged gyri (macrogyria).
a
Fig. 3.15 US in brain malformations. ( a ) Zoomed sagittal midline view: brain stem discontinuity
( dotted line ). ( b ) 3DUS surface rendering: gyration becomes conspicuously visible improving US
potential to depict and demonstrate gyration disorders. ( c ) Coronal view: right-sided hemimega-
lencephaly depicted as focally enlarged and clubbed lateral ventricle with atypical structured and
hyperechoic brain parenchyma
b
c
3.3 Pathologic Findings
Fig. 3.16 Schizencephaly. Parasagittal view depicts
connection between lateral ventricle and external
CSF space. NOTE: Outlining of cleft with cortical
gray matter
• Various forms can be combined with varying severity.
• Usually cortex altered in area of gyration disorder: may fi nd dilated lateral sulcus, enlarged supratentorial ventricular system and unusual position of prominent posterior horns (colpocephaly).
• 3DUS with brain surface rendering may enable improved depiction of gyration
disorders (Figs. 3.15b and 1.28 ) .
3.3.2.2 Megalencephaly
Regional disturbance of brain development, can be generalised or focal/unilateral
(hemimegalencephaly) and may be associated with metabolic disturbances.
US Findings (Fig. 3.15c ):
• If unilateral – asymmetric brain confi guration with enlargement of affected
region/hemisphere.
• Pachygyria, thickened cortex and inhomogenous echogenic disruption of normal
parenchymal echotexture.
• Asymmetry of ventricles with dilatation of the affected side.
• Midline shift towards non-affected side may be present.
• In generalised form – symmetric appearance of above described fi ndings.
95
3.3.2.3 Schizencephaly
Gap in brain parenchyma connecting ventricle to extra-axial CSF system.
If fi lled with CSF – open lip schizencephaly. No fl uid separating the lips – closed
lip schizencephaly.
US Findings :
• Schizencephalic defect seen if CSF fi lled – anechoic CSF connection between
internal and external CSF spaces (Fig. 3.16 ).
• Close lip schizencephaly – harder to diagnose, meticulous observation of course
of cortex and gyri which will not be grossly disrupted by gap, but cortex continues outlining gap borders to wall of ventricle.
• Usually associated hypoplasia of affected hemisphere and ventricular asymmetry of affected side.
96
Fig. 3.17 (Semi-)lobar holoprosencephaly. Single
ventricle without septum pellucidum in coronal view
3 Neurosonography in Neonates, Infants and Children
DDx :
Any kind of porencephalic or cystic defect connecting with ventricle, heterotopia.
NOTE : Cysts usually do not show outlining by cortical grey matter, may connect
with (external) CSF space and are often positioned within normal brain, whereas
schizencephaly is often associated with other malformations (e.g. hypoplasia of corpus callosum).
3.3.2.4 Holoprosencephaly
Rare severe malformation based on lack of hemispheric differentiation of early fetal
brain (Fig. 3.17 ). Several forms:
Alobar Holoprosencephaly
US Findings :
• Single ventricle positioned caudally in midline forming large cystic space.
Thalami fused in midline.
• No third ventricle depictable: no interhemispheric fi ssure, no falx, no corpus callosum and no septum pellucidum. There can be cyclopia (the two eyes fused to
single eye).
• Supratentorial brain consists of single undivided mass.
• CDS: only one ACA (azygos ACA).
Semilobar Holoprosencephaly
A slightly milder manifestation.
US Findings :
• Smaller (still enlarged) single ventricle in midline with remnant of occipital/
temporal horn + respective brain parenchyma.
• Rudimentary falx cerebri/interhemispheric fi ssure seen posteriorly, remnant of
third ventricle.
• Thalami only partially fused, septum pellucidum absent.
• Corpus callosum partially hypoplastic, partially absent.
Lobar Holoprosencephaly
Least severe form.
3.3 Pathologic Findings
Fig. 3.18 Hydranencephaly. Coronal view: huge
dilated CSF space without much supratentorial
braintissue
US Findings :
• Frontal brain incompletely separated – frontal cerebral falx dysplastic or missing
• Ventricular system looks more normal, with enlargement of ventricles and agenesis of septum pellucidum.
• Varying amount of callosal dysgenesis.
De Morsier Syndrome, Septo-Optic Dysplasia
Classifi ed as mild form of holoprosencephaly.
US Findings :
• Partial or complete agenesis of septum pellucidum with frontal fusion of supratentorial ventricular system/frontal horns, potentially some dilatation of lateral
ventricles.
• Dysplastic optic nerves/chiasm not visualised (potentially hypoplastic optic
nerve on transbulbar view).
Agenesis of the Septum Pellucidum
Cannot be differentiated from septo-optic dysplasia by US.
Usually not single entity, but combined with other brain malformations.
97
3.3.2.5 Hydranencephaly
Hemispheres of supratentorial brain replaced by cyst-like fl uid-fi lled spaces. Potentially
caused by hypoxic or ischemic event after normal early brain development.
US Findings :
• Cyst-like structures in area of hemispheres (Fig. 3.18 ).
• Some residual parenchyma may be seen in occipital area vascularised from posterior circulation.
• Brain stem and cerebellum usually look normal.
• Differentiation from holoprosencephaly possible by observing an interhemispheric fi ssure, visualisation of third ventricle and depiction of vessels of anterior circulation (ICA, ACA, MCA).
98
Fig. 3.19 US in tuberous sclerosis. Parasagittal
section, zoomed view of anterior horn of lateral
ventricle with surrounding structures: subependymal
nodules (harmatomas) typical for tuberous sclerosis;
also note the subtle echogenic parenchymal
irregularity consistent with regional white matter
foci (cerebral tubers). NOTE: Cannot be
differentiated from glioma or astrocytoma by US
3 Neurosonography in Neonates, Infants and Children
3.3.3 Phakomatoses
Congenital genetic (inherited) brain malformations with evolving and progressive
pathology, mainly affecting ectodermal structures (nervous system, skin, eyes).
Brain may be normal at birth.
Different forms: Neurofi bromatosis (Type I – von Recklinghausen disease, Type
II with bilateral acoustic neuroma/schwannoma), Sturge-Weber (encephalotrigeminal/meningofacial angiomatosis), Von Hippel-Lindau (CNS angiomatosis) and
tuberous sclerosis (Bourneville-Pringle disease).
US Findings :
• Depend on underlying entity and severity of changes – may often be normal,
parenchymal foci (e.g. in neurofi bromatosis) diffi cult to depict by US.
• Subependymal nodules (hamartoma), cerebral tubers and tumours (glioma,
astrocytoma) depictable, particularly at border of lateral ventricle (Fig. 3.19 ).
• MRI compulsory for work-up.
• Also look for extracerebral manifestations (peripheral neurofi broma, cardiac
rhabdomyoma, renal angiomyolipoma and syndromic cysts, vascular pathology,
etc.) – US used as fi rst screening test.
3.3.4 Cerebral Cysts
Multiple aetiologies, e.g. porencephalic defects after trauma or surgery, cystic transformation after hypoxic, haemorrhagic, and infl ammatory events, syndromic or
dysontogenetic and neuroepithelial cysts and cysts from meninges such as arachnoid cysts.
US Findings :
• All “simple” cysts with mostly anechoic content – internal echoes only after
haemorrhage (or infection).
• Commonly quite spherical, sharp border, no signifi cant membrane and thin wall
• Exhibit posterior acoustic enhancement due to liquid nature, if large enough.
• May show local space occupying effects – may cause hydrocephalus by obstructing CSF drainage.
3.3 Pathologic Findings
99
a
c
Fig. 3.20 Cysts on brain US. ( a ) Parasagittal section: simple (plexus) cyst(s). ( b ) Coronal section:
posthaemorrhagic/post-hypoxic periventricular cyst. NOTE: Sometimes these are diffi cult to distinguish from “physiologic” neuroepithelial cysts. ( c ) Coronal section: porencephalic cyst, fused
with lateral ventricle. ( d ) Coronal brain surface view with linear transducer: teardrop shaped bilat-
eral cortical cysts after subcortical venous haemorrhagic infarctions in NAI. NOTE: Coronal view
with high-resolution linear transducer essential for depicting these changes
b
d
• Sometimes differentiation against cystic/necrotic parts of tumours or dilated
physiological CSF-fi lled structures such as mega cisterna magna diffi cult, also
genesis and entity of cyst often diffi cult to defi ne.
NOTE : US good for depicting cysts, but not always suffi cient for defi ning and char-
acterising aetiology. Other imaging may become necessary, particularly in complex
formations. US also used intraoperatively to guide puncture and drain placement for
treatment of obstructing cysts.
DDx list of cystiform lesions (US image examples of various entities, see
Fig. 3.20 ):
• Physiologic cysts or CSF spaces (remnant of physiological fetal CSF spaces, e.g.
cavum septi pellucidi, cavum vergae, cavum veli interpositi and septum pellucidum cyst), physiologic fl uid-fi lled spaces of meninges and cisterna, choroid
plexus cysts and neuroepithelial/dysgenetic cysts.
• Posthaemorrhagic cysts – typically subependymal or in brain parenchyma
(porencephalic cysts), or subcortical (“tear drop”) in (sub)cortical venous infarctions – typical for NAI/shaken baby syndrome.
100
3 Neurosonography in Neonates, Infants and Children
• Porencephalic cysts after hypoxia/asphyxia and infarction (periventricular
leukencephalomalacia).
• Infl ammatory and postinfl ammatory cysts after abscess, encephalitis or
meningitis.
• Cystic spaces combined with complex malformations and syndromic cysts.
• Arachnoid cysts, chronic subdural hygroma and cystic tumour.
• Cavernous or aneurysmal ectasia of vascular structures in various arteriovenous
malformations – usually recognised by CDS.
3.3.5 Ischemic Encephalopathy
Introduction
Brain hypoxia usually constitutes severe thread:
• In neonates – perinatal asphyxia.
• In older children various accidents (drowning, perioperative complications, e.g.
in cardiac surgery).
• Focal infarction may occur even in neonates which lead to focal ischemic lesions
and potentially secondary haemorrhage.
• Different forms of hypoxic damage associated with immaturity of brain and
varying age-related aetiology (listed in Tables 3.2 and 3.3 ).
NOTE : Reasons and incidence for infarctions partially differ from adults: thrombo-
embolic complications, vasculitis and underlying vascular malformations, coagulopathies, hyperviscosity, infl ammatory conditions, metabolic-toxic events
(metabolic stroke) and systemic conditions (low cardiac output, low blood pressure,
low circulating volume, etc.).
3.3.5.1 Preterm Infant
Periventricular Leukencephalomalacia (PVL)
Typical disease of preterm neonates in oxygen dependent and sensitive areas – periventricular white matter. Bi- or unilateral distribution may relate to watershed areas.
Any kind of perfusion or oxygenation disturbance may lead to oxygen deprivation
and focal defects; areas initially oedematous before eventually becoming necrotic
and cystic.
US Findings (Fig. 3.21 ):
• Affected parenchyma initially hyperechoic, may be patchy and very early or
subtle stages indistinguishable from physiologic immaturity (i.e. hyperechogenicity of periventricular white matter = PVE).
• During follow-up changes may resolve (if no brain damage) – hyperechogenicity
disappears, followed by normal myelination and maturation.
• More severe damage – affected areas increasingly patchy and hyperechoic,
potentially also caused by subtle focal secondary haemorrhage, eventually turn
into an-/hypoechoic cysts. Cysts may become confl uent or fuse with ventricle,
then ventricular borders become irregular and ventricle enlarges in area of defect.
3.3 Pathologic Findings
abc d
egf
Fig. 3.21 PVL and white matter atrophy. ( a , b ) Early PVL in coronal ( a ) and parasagittal ( b )
view – seen as patchy bright focal periventricular echogenicities. ( c ) Parasagittal view: PVL with
multiple confl uent cysts replacing destroyed white matter. Note enlarged extra-axial CSF space.
( d ) Coronal view: Bilateral cystic paraventricular defects in old PVL. Note also enlarged inter-
hemispheric fi ssure as a sign of atrophy. ( e , f ) PVL in older infant with narrowed occipital periven-
tricular white matter on the left side, thus the sulci nearly reach the ventricular wall of the clubbed
and enlarged posterior horn of the lateral ventricle, ( e ) coronal section and ( f ) parasagittal view to
paraventricular space. ( g ) Coronal view: narrowed parenchyma – cortex and sulcus nearly reaching
ventricular border, all white matter destroyed as late sign of PVL
101
• Long term – only subtle changes such as thinned periventricular white matter
with very short distance between sulci and ventricular border with prominent
lateral ventricles that exhibit irregular shape/border may be only US sign.
• 3DUS may be helpful to give a conspicuous overview and to compare with other
sectional imaging.
3.3.5.2 Global or Diffuse Brain Oedema
Typical in severe conditions and mature brain – subdivided in global, cortical, brain
stem and basal ganglia hypoxia.
US Findings :
• In periacute phase: brain looks completely normal.
• After 8–72 h, brain becomes hyperechoic, with loss of cortico-medullary differentiation (“bright brain”), or inversed echogenicity of usually slightly hypoechoic cortex
from hyperechoic white matter (particularly in cortical ischemia). Due to oedema,
CSF spaces become narrowed, particularly obvious at lateral ventricles (Fig. 3.22 ).
• Later, damaged and necrotic areas become cystic or gliotic, the latter diffi cult to
depict on US.
• Finally, brain atrophy – with widening of inner and outer CSF spaces, widening
of sulci, disruption of cortico-medullary differentiation of brain parenchyma
(Fig. 3.23 ).
102
3 Neurosonography in Neonates, Infants and Children
a
Fig. 3.22 Brain US in asphyxia. ( a ) Coronal view: bright brain. ( b ) Linear transducer, coronal
view: cystic degeneration after severe asphyxia
b
a b
Fig. 3.23 Brain atrophy. ( a ) Coronal view in brain atrophy: large IHS/extra-axial CSF space,
somewhat prominent ventricles. ( b ) Coronal view with linear transducer: widened IHF, large extra-
axial CSF space and lateral ventricles
NOTE : Gray scale US fi ndings very nonspecifi c; diagnoses and follow-up of brain
oedema relies on Doppler fi ndings, as increased intracranial pressure will occur
impairing cerebral perfusion – discussed below.
3.3.5.3 Focal Hypoxemia and Ischemia
US Findings
• Initially Normal US
• When oedema manifests – increasing echogenicity due to swelling and oedema
around affected area with some swelling as well as disruption of typical corticomedullary differentiation (Fig. 3.24 ).
• Sometimes inversion of echogenicity of cortex and white matter.
• Potentially secondary haemorrhage – focal patchy echogenicities (Fig. 3.25 ),
sonographically indistinguishable from typical haemorrhagic infarction after
venous thrombosis (except for location – always also assess veins if unclear or
unusual).
3.3 Pathologic Findings
103
a
b
c
Fig. 3.24 US in infarction. ( a ) Coronal view: MCA infarction in subacute stage: increased echo-
genicity oft affected left MCA territory. ( b ) Axial view by TCI: increased echogenicity indicating
infarction of ACA territory. ( c ) Parasagittal view: older stage of an MCA infarction with cystic
transformation
Fig. 3.25 Coronal view: haemorrhagic infarction
in early stage. Coronal view: echogenic, somewhat
triangular shaped defect in frontal area in a baby
with haemorrhagic infarction of the right ACA
territory
• Small focal infarctions are sonographically diffi cult to detect, usually only
depicted in near fi eld when using high-resolution linear transducers.
• Eventually focal infarctions form focal defects: cysts, gliosis (diffi cult to depict
on US), focal atrophy, etc.
• Haemorrhagic areas can form secondary calcifi cations.
NOTE : Infarctions will adhere to distributional areas – may affect either watershed
area or territory of major vessels Sometimes steal phenomena may lead to more diffuse
or multifocal manifestation, e.g. in large vascular malformations with shunt fl ow.