Cranial Sonography: Techniques and Image

Interpretation

Lisa H. Lowe

Zachary Bailey

OBJECTIVE

• To discuss the modern approach for cranial ultrasound of grey scale technique and interpretation

• Use of linear imaging and use of multiple fontanels and screening doppler techniques

Cranial ultrasound technique

• Performed using linear array transducer via anterior fontanel in coronal and sagittal planes

• 6 to 8 coronal images from frontal lobes ant to frontal horns of lateral ventricle to occipital lobes posterior to lateral ventricle trigones

• Sagittal midline view of corpus callosum and cerebellar vermis and bilateral parasagittal images

• Four doppler images for screening vascular structures, arterial system for patency and resistance to flow by obtaining color doppler images of circle of Willis obtained via anterior or temporal fontanel to localize MCA or ICA and obtain spectral tracing with PSV, EDV and RI

• Venous system is evaluated for patency by obtaining color doppler images of sagittal sinus and vein of Galen

• Areas of hyper or hypovascularity for vascular ischemia or infarction

• CD via posterior fontanel or foramen magnum used for screening for patency of transverse sinuses

• Linear transducer via anterior fontanel allow detailed interrogation of convexity of subarachnoid space and superficial cortex and deep brain matter.

Cranial ultrasound interpretation

GREY SCALE IMAGING

CORONAL VIEWS

SAGITTAL VIEW

PARASAGITTAL VIEW

DOPPLER IMAGING

Conclusion

• With modern protocols used in cranial sonography is highly accurate in detection of cranial abnormalities

discussion

• Coronal brain scans of skull with transducer held along anterior fontanalle six standard frozen images are acquired1. Most anterior scan is anterior to frontal horn of

lateral ventricle contains• Frontal lobes of cerebral cortex• Orbits deep to internal floor of skull base

Orbital ridges

Frontal lobes

Interhemispheric fissure

INTERHEMISPHERIC FISSURE

CHOROID PLEXUS

FRONTAL LOBES

• Next is section through frontal horns of lateral ventricle : symmetric anechoic and comma shaped

– Structures from superior to inferior in midline are

1. Interhemispheric fissure2. Cingulate sulcus3. Genu and anterior body of corpus callosum4. Septum pellucidum5. Lateral to putamen is the echogenic septum pellucidum6. Inferiorly the ICA bifurcates to form ACA and MCA which

appear echogenic

INTERHEMISPHERIC FISSURE

CINGULATE SULCUS

GENU AND BODY OF CORPUS CALLOSUM

SEPTUM PELLUCIDUM

FRONTAL HORNS OF LATERAL VENTRICLE

TEMPORAL LOBES

ICA BIFURCATION TO ACA AND MCA

• More posteriorly the body of lateral ventricles and either cavum septum pellucidum are noted

• Other structures are

1. Thalami on either side of 3rd ventricle2. Deep to thalami is the brainstem3. Lateral to lentiform nucleus is the deep white matter of

brain called the centrum semiovale

THALAMUS

CAUDATE NUCLEUS

SYLVIAN FISSURE

3RD VENTRICLE

CAVUM SEPTUM PELLUCIDUMBODY OF LATERAL VENTRICLE

BRAINSTEM (PONS)

INTERNAL CAPSULE

• More posteriorly the body of lateral ventricle becomes more rounded and size of caudate nucleus decreased in size posterior to foramen of Monroe

• Echogenic matter in floor is choroid plexus

• Prominent thalami • Posterior fossa contain echogenic vermis• If cavum septum pellucidum is cystic

posteriorly it is labelled as cavum vergae• Temporal horns of lateral ventricle are

seen only in case of hydrocephalus

BODY OF LATERAL VENTRICLE

CHOROID PLEXUS

THALAMUS POSTERIOR FOSSA WITH VERMIS

CAVUM VERGAE

• Posterior sections reveal :-– Trigone or atrium of lateral ventricle is visualised – Echogenic glomus of choroid plexus obscures lumen of

CSF

GLOMUS

PARIETAL LOBE

CENTRUM SEMIOVALE

• Most posterior section :-1. Occipital lobe2. Occipital horns of lateral ventricle angled posterior to

cerebellum

SAGITTAL BRAIN SCANS

1. Midline– Curving line of corpus callosum– Cystic cavum septum pellucidum– Cerebellar vermis

• Shallow angulation 10 to either sides :-– Normal lateral ventricles– Anterior sector medial and posterior sector lateral – Caudate nucleus and thalamus with in arms of ventricle– Caudothalamic groove area to recognise germinal matrix

hemorrhage– Normal hyperechoic blush posterior and superior to

ventricular trigones on parasagittal views– Normal peritrigonal echogenity

FRONTAL LOBE

CAUDOTHALAMIC GROOVE

CAUDATE NUCLEUS

THALAMUS

CHOROID PLEXUS

SYLVIAN FISSURE

INSULAR CORTEX

TEMPORAL LOBE

Through posterior fontanalle

• AFFORDED GREATER ACCURACY IN DETECTION OF INTRAVENTRICULAR HEMORRHAGE THAN ANTERIOR FONTANALLE IMAGING WHEN VENTRICLES ARE NOT DILATED

• POSTERIOR FONTANALLE IMAGING ALSO HELPED IN DETERMINING POSTERIOR FOSSA MALFORMATIONS

LATERAL VENTRICLE

THALAMUS

OCCIPITAL LOBE

CHOROID

TRIGONE OF LATERAL VENTRICLE

Doppler sonography

SYLVIAN FISSURE

THALAMUS

MCA

BRAINSTEM

CORPUS CALLOSUM

PONS

BRANCH OF PERICALLOSAL ARTERY

CEREBELLUM

OCCIPITAL LOBE

4TH VENTRICLE

CINGULATE GYRUS

CIRCLE OF WILLIS MCA

CEREBELLUM VERMIS

BRAINSTEM

CIRCLE OF WILLIS

MCA

TEMPORAL LOBES

Normal variants and pitfalls that mimics pathologic abnormalities

• Immature sulcation in premature infants• Persistent fetal fluid filled spaces• Mega cisterna magna• Asymmetric ventricular size• Choroid plexus variants• Periventricular cystic lesions• Hyperechoic white matter pseudolesions or

periventricular halo• Lenticulostriate vasculopathy

• Immature sulcation– Infants born before the 24th week possess a

smooth cerebral cortex exhibiting only the sylvian fissures.

– a diagnosis of lissencephaly should not be made in patients younger than 24 weeks’ gestational age

• Persistent fetal fluid filled spaces– Persistent fetal fluid–filled spaces, a common

finding in healthy neonates, include the cavum septi pellucidi (CSP), cavum vergae, and cavum veli interpositi.

– The CSP is the most anterior and the most common of the fetal fluid–filled spaces.

– Persistent fetal fluid–filled spaces occasionally persist into adulthood and are a normal variant of no significance

• Mega cisterna magna1. The typical cisterna magna is less than 8 mm

in both the sagittal and axial planes 2. A mega cisterna magna, which some believe

is due to cerebellar damage and volume loss, measures greater than 8 mm and is seen in 1% of postnatally imaged brains

3. A mega cistern magna is a normal variant distinguished from an arachnoid cyst by its lack of mass effect and from a Dandy Walker malformation by the presence of the cerebellar vermis

• Assymetric ventricles1. Normal ventricles measure less than 10 mm in

transverse diameter, with 60% of full term and 30% of premature infants having ventricles smaller than 2–3 mm

2. Asymmetry between the sizes of the ventricles has been observed in 20–40% of infants

• Choroid Plexus Variants1. It does not extend past the caudothalamic

grooves into the frontal horns or past the ventricular atria into the occipital horns.

2. Echogenic material anterior to the caudothalamic groove or in the dependent portions of the occipital horns suggests germinal matrix and intraventricular hemorrhage

3. Lobular or bulbous variants of the choroid plexus occur most frequently in the glomus within the ventricular atria and lateral ventricles

4. Choroid cysts smaller than 1 cm are incidentally noted in 1% of infants at autopsy

• Periventricular Cystic Lesions1. Cystic lesions in the periventricular region

include connatal cysts, subependymal cysts,and white matter cysts due to periventricular leukomalacia

2. Connatal (or subfrontal) cysts are seen most often during the early postnatal period and may regress spontaneously

3. The sonographic appearance includes bilateral symmetric cysts located adjacent to the frontal horns, just anterior to the foramina of Monro. The cysts frequently appear in multiples and take on a classic appearance that has been likened to a string of pearls

4. Two indistinguishable cysts are located at the caudothalamic groove, including a subependymal cyst due to germinal matrix hemorrhage and a germinolytic cyst due to metabolic disorders such as Zellweger syndrome

5. cysts found in the white matter adjacent to lateral ventricles are typically the result of periventricular leukomalacia,which is caused by hypoxic ischemic injury in the premature infant

• Hyperechoic White Matter Pseudolesion or Periventricular Halo1. Hyperechoic white matter pseudolesions, or

periventricular halos, may appear as artifacts due to anisotropic effect

2. Additional images obtained at a 90° angle resolve the finding and prevent misinterpretation

3. periventricular white matter pseudolesions and halos are normally less echogenic than the adjacent choroid plexus

• Lenticulostriate Vasculopathy1. thought to be due to thickening of the

lenticulostriate artery walls secondary to a variety of pathologic conditions and infections

2. lenticulostriate vasculopathy often occurs without a specific cause being identified and thus remains a nonspecific finding seen on sonography as unilateral or bilateral branching,linear, or punctate increased echogenicity within the thalami