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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5795_Библиотеки_им_академика_М_И_Перельмана.pdf
128
M. Riccabona
8.3 Pathologic Findings
8.3.1 Neural Tube Defects
8.3.1.1 Anencephaly
Most severe malformation, diagnosed prenatally. No postnatal indication for US.
8.3.1.2 Meningomyelocele andEncephalocele
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.8.13a).
8.3.1.3 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.8.13b).
Classification and US Findings
Depending on nomenclature: grade I to grade III, trying to categorise minimal
ndings:
Fig. 8.13 Cerebral manifestations of neural tube defects. (a) Linear transducer on the occipital
skull: small osseous defect depicted with herniation of uid-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
8 Neurosonography inNeonates, Infants andChildren
129
• 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 causing hydrocephalus.
• Type III: most severe form—occipito-cervical encephalocele.
• 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.
8.3.1.4 Dandy–Walker Malformations/Spectrum
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 ndings with dysgenesis of vermis and cystic dilatation
of fourth ventricle without enlargement of posterior fossa, potentially enlarged posterior fossa CSF space.
8.3.1.5 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.8.14).
• Atypical impression of frontal horns of lateral ventricle: lateralised, staghorn
shape in coronal view.
• Colpocephalic conguration of posterior horns. Elevation of roof of third
ventricle.
• Minimal forms: only regional thinning / tapering or discontinuity of corpus
callosum.
• Associated malformations, for example: arachnoid cyst, Arnold–Chiari and various syndromes (Trisomia 8, 13, etc.).
Note
Subtle partial agenesis or dysgenesis of corpus callosum more difcult to visualise
on US.Clue to diagnosis—atypical form of cingulate gyrus in respective area, close
contact of radially diverging sulci—use coronal view.
130
M. Riccabona
ab
Fig. 8.14 Agenesis of corpus callosum. (a) Sagittal view: no corpus callosum seen. Gyri reach
roof of third ventricle, no gyrus cingulum; additional CDS and duplex ow spectrum of pericallosal artery which also runs directly on roof of third ventricle. (b) Coronal section demonstrates
prominent “Probst” bundles and stag-horn conguration of lateral ventricles with missing crossing bres
8.3.1.6 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.
8.3.2 Migration andGyration Alterations andDisturbances
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, heterotopia and similar phenomena: MRI.
• US used as initial tool, may depict gross changes both of gyration and 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.8.15a) or sonographically difcult or impossible to diagnose.
8 Neurosonography inNeonates, Infants andChildren
Fig. 8.15 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 hemimegalencephaly depicted as focally enlarged and clubbed lateral ventricle with atypical structured and
hyperechoic brain parenchyma
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8.3.2.1 Lissencephaly, Pachygyria, Macro- or Polygyria
andColpocephaly
Definition and US Findings
• Disruption of normal gyration, focally or more extensive.
• Can be completely missing (agyria) or altered, showing many tiny gyri
( polymicrogyria), few unusually at gyri (pachygyria) or enlarged gyri
(macrogyria).
• Various forms can be combined with varying severity.
• Usually cortex altered in area of gyration disorder: may 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 (Fig.8.15b see also section on 3DUS).
8.3.2.2 Megalencephaly
Regional disturbance of brain development, can be generalised or focal/unilateral
(hemimegalencephaly) and may be associated with metabolic disturbances.
US Findings (Fig.8.15c)
• If unilateral—asymmetric brain conguration 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 the above described ndings.
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Fig. 8.16 Schizencephaly. Parasagittal view
depicts connection between lateral ventricle and
external CSF space. Note: Outlining of cleft with
cortical grey matter
M. Riccabona
8.3.2.3 Schizencephaly
Gap in brain parenchyma connecting ventricle to extra-axial CSF system.
If lled with CSF—open lip schizencephaly. No uid separating the lips—closed
lip schizencephaly.
US Findings
• Schizencephalic defect seen if CSF lled—anechoic CSF connection between
internal and external CSF spaces (Fig.8.16).
• 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.
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).
8.3.2.4 Holoprosencephaly
Rare severe malformation based on lack of hemispheric differentiation of early foetal brain (Fig.8.17). 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 ssure, no falx, no corpus callosum and no septum pellucidum. There can be cyclopia (the two eyes fused to
single eye).
ab
8 Neurosonography inNeonates, Infants andChildren
Fig. 8.17 (Semi-)lobar holoprosencephaly. Single ventricle without septum pellucidum in coronal view (a)—more impressive perception when viewed more posteriorly (b)
133
• 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 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.
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
Classied as mild form of holoprosencephaly.
134
M. Riccabona
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 oftheSeptum Pellucidum
Cannot be differentiated from septo-optic dysplasia by US.
Usually not single entity, but combined with other brain malformations.
8.3.2.5 Hydranencephaly
Hemispheres of supratentorial brain replaced by cyst-like uid-lled spaces.
Potentially caused by hypoxic or ischemic event after normal early brain
development.
US Findings
• Cyst-like structures in area of hemispheres (Fig.8.18).
• 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 ssure, visualisation of third ventricle and depiction of vessels of anterior circulation (ICA, ACA, MCA).
Fig. 8.18 Hydranence phaly. Coronal view: huge
dilated CSF space without much supratentorial
brain tissue
8 Neurosonography inNeonates, Infants andChildren
135
8.3.3 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: Neurobromatosis (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 neurobromatosis) difcult to depict by US.
• Subependymal nodules (hamartoma), cerebral tubers and tumours (glioma,
astrocytoma) depictable, particularly at border of lateral ventricle (Fig.8.19).
• MRI compulsory for workup.
• Also look for extracerebral manifestations (peripheral neurobroma, cardiac
rhabdomyoma, renal angiomyolipoma and syndromic cysts, vascular pathology,
etc.)—US used as rst screening test.
8.3.4 Cerebral Cysts
Multiple aetiologies, e.g. porencephalic defects after trauma or surgery, cystic transformation after hypoxic, haemorrhagic and inammatory 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 signicant membrane and thin wall.
Fig. 8.19 US in tuberous sclerosis. Parasagittal
section, zoomed view of anterior horn of lateral
ventricle with surrounding structures:
subependymal nodules (hamartomas) 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
136
ac
M. Riccabona
• Exhibit posterior acoustic enhancement due to liquid nature, if large enough.
• May show local space-occupying effects—may cause hydrocephalus by obstructing CSF drainage.
• Sometimes differentiation against cystic/necrotic parts of tumours or dilated
physiological CSF-lled structures such as megacisterna magna difcult, also
genesis and entity of cyst often difcult to dene.
Note US good for depicting cysts, but not always sufcient for dening 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.8.20):
• Physiologic cysts or CSF spaces (remnant of physiological foetal CSF spaces,
e.g. cavum septi pellucidi, cavum vergae, cavum veli interpositi and septum
pellucidum cyst), physiologic uid-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 (“teardrop”) in (sub)cortical venous infarctions— the latter typical for NAI/shaken baby syndrome.
• Porencephalic cysts after hypoxia/asphyxia and infarction (periventricular
leukencephalomalacia).
• Inammatory and postinammatory 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.
b
Fig. 8.20 Cysts on brain US. (a) Parasagittal section: simple (plexus) cyst(s). (b) Coronal section:
posthaemorrhagic/post-hypoxic periventricular cyst. Note: Sometimes these are difcult 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 bilateral
cortical cysts after subcortical venous haemorrhagic infarctions in NAI. Note: Coronal view with
high-resolution linear transducer essential for depicting these changes
d
8 Neurosonography inNeonates, Infants andChildren
137
8.3.5 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 and locations of hypoxic damage associated with immaturity of
brain and varying age-related aetiology (listed in Tables 8.2 and 8.3).
Note Reasons and incidence for infarctions partially differ from adults: thrombo-
embolic complications, vasculitis and underlying vascular malformations, coagulopathies, hyperviscosity, inammatory conditions, metabolic-toxic events
(metabolic stroke) and systemic conditions (low cardiac output, low blood pressure,
low circulating volume, etc.).
8.3.5.1 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.8.21)
• 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 conuent or fuse with ventricle, then ventricular borders become irregular and ventricle enlarges in area
of defect.
• 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.