Cranial Ultrasound Rekha Meesa, MD Section of Pediatric Radiology

Cranial Ultrasound Rekha Meesa, MD Section of Pediatric Radiology
Mott Children’s Hospital, University of Michigan

Embrology End of three weeks a. Forebrain b. Midbrain c. Hindbrain
a. Telencephalon-Cerebral Hemispheres b. Diencephalon – Top of brainstem Midbrain a. Mesencephalon – Upper brain stem Hindbrain a. Metencephalon – Middle brain stem and cerebellum b. Myelencephalon – Lowest part of brain stem & part of spinal cord.

Embryonic Development
SonographyCME.com, Neonatal Cranial Ultrasound

Meninges 3 membranes protect brain and spinal cord Falx Cerebri
a. Partition between two hemispheres Tentorium Cerebelli a. Separates cerebral hemispheres from cerebellum Falx Cerebelli a. Downward from tentorium cerebelli btw two cerebral hemispheres

SonographyCME.com, Neonatal Cranial Ultrasound

Cerebrum (Telencephalon)
Cerebral hemispheres Cerebral Cortex White Matter Basal Ganglia

Diencephalon Between cerebral hemispheres, around third ventricle
a. Thalamus b. Hypothalamus c. Epithalamus

Ventricular System b. Body c. Occipital Horns d. Temporal Horns
Lateral Ventricles: a. Frontal Horns b. Body c. Occipital Horns d. Temporal Horns Third Ventricle Fourth Ventricle

Fissures and Sulci Interhemispheric fissure Central Sulcus
Sylvian Fissure Parieto-Occipital Fissure Transverse Fissure Fissure of Rolando

Fissures and Sulci Sylvian Fissure or Lateral Sulcus
a. Divides frontal and parietal lobe from above and temporal lobe from below b. One of earliest developing sulci of brain c. First appears around fourteenth gestational week. d. Middle cerebral artery courses in Sylvian Fissure

Cavum Septi Pellucidi Lies in midline between frontal horns and bodies of lateral ventricles Thin triangular space filled with cerebral spinal fluid a. Begins to close during 6th month of gestation b. Completely obliterated by 3-6 months of age

Germinal Matrix Highly vascular tissue, in early gestation forms entire wall of ventricular system Regresses after 3rd month, starting from third ventricle, then temporal and occipital horns 6 months – persists only over head of caudate nucleus and at border with thalamus

Introduction Portable High-resolution images
Nearly always initial examination of choice, especially in unstable, premature infants.

Primary Uses Hydrocephalus
Periventricular, intraventricular, and intracerebral hemorrhage. Ischemic lesions Infection (bacterial meningitis) Congenital anomalies Others (tumors, craniosynostosis, etc)

Technique Neonatal brain sonography performed through anterior fontanelle a. Usually begins closure at about 9 months and complete by about 15 months b. May remain open after this period in premature infants, in patients with increased intracranial pressure, chromosomal abnormalities, etc.

Technique Images obtained in coronal and sagittal planes through anterior fontanelle. a. Coronal images: transducer transversely across anterior fontanelle and angling ultrasound beam from anterior to posterior. b. Sagittal images: transducer longitudinally on anterior fontanelle and angling medially to laterally.

Equipment Frequency selected to maximize resolution and depth of penetration 7.5 MHz phased array or vector transducer- adequate for evaluation of premature infant 5 MHz – term or older, larger infants with closing fontanelles High-resolution, linear array for superficial structures.

Coronal sections b. Foramen of Monro
6 standard coronal scans a. Frontal horns anterior to foramen of Monro b. Foramen of Monro c. Posterior aspect of third ventricle through thalami d. Quadrigeminal cistern e. Trigones of the lateral ventricles f. Parietal and Occipital horns.

Coronal Imaging planes

Sagittal sections Midline Caudothalamic groove
Body of each lateral ventricle Each cerebral cortex

Sagittal Imaging Planes

Technique Posterior and Mastoid fontanelle views also obtained.
a. Posterior fontanelle closes about 3 months of age. b. Mastoid fontanelle may remain open until 2 years of age. Axial, Coronal, and Sagittal views through posterior fontanelle. a. Located slightly above external occipital protrusion. a. Neonatal head turned to one side. b. Sagittal views through midline of each occipital horn c. Coronal views through occipital horns posterior to choroid plexus.

Technique b. Transducer behind pinna of ear and above tragus.
Mastoid views: a. Junction of squamosal, lambdoidal, and occipital sutures. b. Transducer behind pinna of ear and above tragus. c. Obtained at least at two levels: 1. Brainstem and posterior fossa d. Useful for evaluating brainstem, posterior fossa, and cerebral circulation.

Posterior fontanelle view
Axial scans a. Trigones of lateral ventricles b. Occipital horn is better visualized

US image obtained through the posterior fontanelle with the transducer positioned directly over the calcarine fissure () demonstrates the body of the right lateral ventricle () as well as the occipital horn () and a choroid glomus (G []).

US image obtained with the transducer positioned slightly cephalad to the calcarine fissure () provides an excellent view of the body of the right lateral ventricle () as well as the occipital () and temporal () horns and the choroid glomus (G []). Because the patient was supine, the posterior fontanelle was not accessible.

Mastoid fontanelle scan
Axial images: brainstem and posterior fossa Anterior axial images at level of brainstem: third ventricle, cerebral peduncles, thalamus, basilar cisterns. Posterior images: fourth ventricle, posterior vermis, folia of cerebellar hemispheres, tentorium, and cisterna magna.

(a) US image of the midbrain obtained through the mastoid fontanelle shows an echogenic line denoting a collapsed third ventricle and aqueduct () as well as the cerebral peduncle (), thalamus (), and quadrigeminal plate cistern (Q []), which blends into the upper cerebellum. The perimesencephalic cistern () and tentorium () are also seen.

US image of the posterior fossa obtained through the mastoid fontanelle depicts the fourth ventricle (), posterior vermis (), cisterna magna (), and cerebellar hemisphere (CH []).

Intracranial Hemorrhage
4 major types a. Subdural b. Primary subarachnoid c. Intracerebellar d. Intraventricular (IVH)

Subdural hematoma

Benign Macrocrania Extraventricular obstructive hydrocephalus
6 months to 2 years a. Head circumference above 97th percentile b. Prominence of subarachnoid spaces c. Cause is idiopathic d. Normal variant

If enlargement of the subarachnoid spaces persists during infancy, brain doesn’t fill the space in cranial cavity. Craniocerebral disproportion from any cause (external hydrocephalus, internal hydrocephalus, arachnoid cyst, or chronic subdural hematoma) makes patient more susceptible to subdural hemorrhage after a inconsequential trauma.

http://www. medscape. com/AANS/NF/1999/v07. n04/nf0704. 05

Germinal Matrix Intraventricular Hemorrhage (GM-IVH)
Major cause of mortality and morbidity in premature infants Can occur in up to 20% of infants delivered at less than 32 weeks gestation Site of origin: Subependymal germinal matrix Located between caudate nucleus and thalamus Highly vascular and stress sensitive region

GM-IVH Grading scale between I to IV More common in males 2:1 ratio
Hemorrhage in acute or subacute setting - Hyperechoic focus

Left Grade 1 GMH

Grade 2 GMH

Grade 1 hemorrhage – None to minimal intraventricular hemorrhage
a. Infants often asymptomatic b. Most resolve completely, may appear cystic Grade 2 – Presence of blood in a non-dilated ventricular system. - Hemorrhage filling less than 50% of ventricular area

Grade III: Intraventricular blood and ventricular dilation.
a. Some degree of neurologic deficit Grade IV: a. Extension of intraventricular hemorrhage in premature infants or complication of infarction or asphyxia in full-term infants. b. Prognosis often poor c. Porencephalic cysts form

Intraventricular Hemorrhage

Prognosis Grade 1 and 2: Generally good
Grade 3 and 4: Variable long-term deficits a. Outcome in grade 3 is usually good if no parenchymal injury Hydrocephalus is a common complication

Periventricular Leukomalacia
Echogenic area adjacent to lateral ventricles In 2-3 weeks become a cluster of small cysts due to necrosis Etiology multifactorial a. Vulnerable vascular network b. Poor cerebral vascular auto-regulation c. Vulnerability of premature newborn infant white matter d. Intrauterine infection or inflammation

PVL Prognosis depends on extensivity of lesions
Significant percentage of premature infants with PVL develop cerebral palsy, intellectual impairment or visual disturbances. > 50% of infants with PVL or grade III hemorrhage develop cerebral palsy.

Flaring: Slightly echogenic periventricular zone, seen in many premature infants in first week of life Normal variants vs. PVL grade 1 If persists beyond first week of life, definition of PVL grade 1.

PVL Cystic lesions are often not present in first week
Hyperechogenicity of periventricular white matter a. Often resolves without development of cystic PVLM b. In some, cystic change develops

First week and 10 days later

PVL vs. anisotropy

Cystic changes of PVL left occipital lobe

Extensive PVL

PVL vs. Intraparenchymal Hemorrhage
IPH a. More premature, smaller infants b. First 4 days of life c. Often asymmetric and unilateral d. Often has mass effect PVL a. Later (10 days to 6 wks) b. More symmetrical, bilateral, no mass effect

Bacterial Meningitis Echogenic widening of brain sulci, meningeal thickening and hyperemia Bacteremia and sepsis Initial seeding of central nervous system via choroid plexus. Into CSF and can cause inflammation of ventricular system (ventriculitis) Inflammation of meninges follows

Sonographic findings in bacterial meningitis in neonates and young infants, Pediatr Radiol February; 38(2): 129–137

Bacterial meningitis Arachnoiditis
a. Vasculitis especially in small and medium-size veins that traverse subarachnoid space b. Inflammation to walls of bridging and cortical veins cause thrombophlebitis and vascular occlusion - cortical infarcts

Sonographic findings in bacterial meningitis in neonates and young infants, Pediatric Radiology February; 38(2): 129–137

Former 25 weeker with group B strep meningitis: Multiple bilateral echogenic lesions in the cerebral cortex and heterogenous echogenicity in the basal ganglia are consistent with cerebritis, small hemorrhages and ischemic brain injury. Mild/moderate dilatation of the lateral ventricles (bifrontal diameter 3.1 cm) and third ventricle not significantly changed from the MRI. Echogenic material in the occipital horns and layers in the frontal horns are consistent intraventricular hemorrhage. Cystic lesions are seen lateral to the frontal horns in the 3 and 9 o' clock positions consistent with periependymal germinolysis

Meningitis

Bacterial virulence factors and inflammatory cytokines contribute to inflammatory process.
Diffuse cerebral edema, increased intracranial pressure, alterations of cerebral blood flow. Lipopolysaccharides in bacterial cell wall a. Blood-brain disruption b. Arachnoiditis and ventriculitis c. Generalized encephalopathy d. Neuronal loss, gliosis and periventricular leukomalacia. 1. Diffuse cerebral cortical and white matter atrophy, hydrocephalus, multicystic encephalomalacia, proencephaly and ventricular septations.

Newborn infant a. Steptococcus group B, Escherichia coli, and Listeria monocytogenes Acute phase of meningitis a. Marked vasodilation of cortical vessels Later stages b. Global reduction in cerebral blood flow due to impairment of cerebral auto-regulation and brain edema.

Color Doppler Color doppler can be used to distinguish subarachnoid fluid from subdural collection Benign enlargement of subarachnoid spaces from subdural effusions. When subarachnoid fluid is present cortical vessels on the brain surface are surrounded by fluid, whereas fluid in the subdural space compresses the cortical vessels along the surface of the brain

Intraventricular findings
Ventriculitis includes an irregular and echogenic ependyma, the presence of intraventricular debris and stranding, often associated with ventricular dilatation Inflammation in ventricles a. Intraventricular adhesions and formation of septae b. Can cause compartmentalization in ventricles, leading to intraventricular cyst formation

Parenchymal findings in bacterial meningitis
Areas of abnormal brain echogenicity reported in 12 – 65% of infants with bacterial meningitis Lesions – focal or diffuse Cerebritis, infarction, secondary hemorrhage or early abscess.

Brain Edema Acute meningitis: intra and extracellular edema can occur
Compression of ventricles Increased intracranial pressure a. Increased RI 1. Increased pulsatility of arterial flow 2. Venous thrombosis

Diffuse brain swelling with extra axial fluid and possible right parenchymal hemorrhage and HIE

Hydrocephalus Communicating – decreased absorption of CSF due to obstruction of arachnoid villi by blood and debris or development of arachnoiditis Obstructive – obstruction of CSF flow Two major causes in infants: intraventricular hemorrhage and meningitis

Hydrocephalus Ventricular dilatation in 14 – 65% of infants with bacterial meningitis Level of obstruction to CSF flow often outside ventricular system a. Can occur within narrowest portions of ventricles 1. Aqueduct of Sylvius 2. Exit foramina of fourth ventricle

Differentiate from hydraencephaly and holoprosencephaly

Hydrocephalus SonographyCME.com, Neonatal Cranial Ultrasound

Hydrocephalus with acqueductal stenosis

Holoprocencephaly Spectrum of cerebral abnormalities resulting from incomplete cleavage of the forebrain. Absent interhemispheric fissure. There are three types according to the degree of forebrain cleavage. a. Alobar type - most severe, characterized by a monoventricular cavity and fusion of the thalami. b. Semilobar type - partial segmentation of the ventricles and cerebral hemispheres posteriorly with incomplete fusion of the thalami. c. Lobar holoprosencephaly - normal separation of the ventricles and thalami but absence of the septum pellucidum. The first two types are often accompanied by microcephaly and facial abnormalities.

Differential Diagnosis
Hydranencephaly a. In utero compromise of anterior cerebral circulation b. Anoxia, infection, thrombophilic states, maternal toxins c. Cerebral hemispheres are nearly absent but falx cerebri, thalami, brainstem, and cerebellum are intact. Hydrocephalus (thin cortical mantle in hydrocephalus distinguishes from hydranencephaly)

Dandy Walker Complex Dandy-Walker complex: spectrum of abnormalities of the cerebellar vermis, cystic dilation of the fourth ventricle and enlargement of the cisterna magna. Classified into (a) Dandy-Walker malformation (complete or partial agenesis of the cerebellar vermis and enlarged posterior fossa) (b) Dandy-Walker variant (partial agenesis of the cerebellar vermis without enlargement of the posterior fossa) (c) Mega-cisterna magna (normal vermis and fourth ventricle). Ultrasonographically, contents of the posterior fossa are visualized through a transverse suboccipito-bregmatic section of the fetal head. Dandy‑Walker malformation: Cystic dilatation of the fourth ventricle with partial or complete agenesis of the vermis; In more than 50% of the cases there is associated hydrocephalus and other extracranial defects.

Dandy Walker Malformation and meningitis

Chiari 2 Lacunar skull Small posterior fossa with crowding of structures Cerebellar tonsils herniate through foramen magnum Hydrocephalus a. Colpocephaly b. Stenogyria “Beaked” tectum Large massa intermedia “Kink” of cervicomedullary junction

Intracranial Cysts Choroid Plexus Cyst Arachnoid Cyst Schizencephaly
Arteriovenous Fistula Porencephaly

Choroid Plexus cyst Cyst > 2mm within choroid plexus
Variable size and number Unilateral or bilateral Often incidental findings of uncertain clinical significance Associated signs of trisomy 18 a. Abnormal posturing b. Facial cleft c. Congenital heart disease d. Neural tube defects e. Omphalocele

Arachnoid Cyst Extra-axial cyst displaces brain parenchyma Unilocular
Avascular Common over convexities

Schizencephaly Clefts in gray matter extending from cortical surface to ventricle (pia to ependyma) Lined by dysplastic gray matter Unilateral: Seizures or mild motor deficit Bilateral: Developmental delay, paresis, microcephaly, spasticity

Porencephalic Cyst Intracerebral cavitation due to injury
Often connected with lateral ventricle Look for associated intracranial hemorrhage Mild ventriculomegaly may progress to encephalomalacia/porencephaly over time

Cavum Vellum Interpositum vs. Arachnoid Cyst

Vein of Galen Aneurysmal Malformation
Arteriovenous fistula between deep choroidal arteries and median prosencephalic vein of Markowski Most common extracardiac cause of high-output heart failure in new born Transcatheter embolization at 4-6 months.

Vein of Galen Arteriovenous Malformation

References SonographyCME.com, Neonatal Cranial Ultrasound
Sonographic findings in bacterial meningitis in neonates and young infants, Pediatr Radiol February; 38(2): 129–137.

Cranial Ultrasound Rekha Meesa, MD Section of Pediatric Radiology

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