Neonatal Head 1

What is primary imaging modality for high-risk and unstable premature infants and why?

sonography - because it is portable, nonionizing, noninvasive

What is Prematurity?

a birth occurring before term or 37 weeks of gestation

Are most infants in the late-preterm category (34 to 36 weeks' gestation)?

no, most are often spared neurological impairment

How does the risk of neurological impairment change with increasing prematurity at birth?

the risk increases the more premature an infant is at birth

1What gestational age and weight does a baby have during late preterm (or near-term)?

34 to <37 weeks, weighing <2500g(5lb, 8oz) at birth

What gestational age and weight does a baby have during moderately preterm?

32 to <34 weeks, weighing 2000g(5lb, 5oz) at birth

What gestational age and weight does a baby have during very preterm?

28 to <32 weeks, weighing <1500g(3lb, 5oz) at birth

What gestational age and weight does a baby have extremely preterm?

<28 weeks, weighing <1000g(2lb, 3oz) at birth

Name one of the primary health concerns for premature infants:

neurologic impairment

What is the percentage of hemorrhage for premature (preterm)neonates: <34 week's gestation?

40 - 70%

What is the percentage of hemorrhage for neonates: 26 week's gestation?

40 - 50%

What is the percentage of hemorrhage for neonates: over 32 week's gestation?

<5%

What may develop in 12-20% under 2000g(5lb, 5oz) birth weight?

multifocal necrosis or periventricular leukomalacia (PVL)

Any neonate who suffered a difficult delivery associated with hypoxia or asphyxia may be examined for ______.

multifocal necrosis or periventricular leukomalacia (PVL)

What are the two phases of development and their timeframes?

embryonic (conception to 8 weeks) and fetal (8 weeks to the end of gestation)

What are the two processes involved in development?

gene expression and environmental input

Neuron production starts day ____, mostly complete by __________.

42, midgestation

What do neurons do during development?

neurons migrate and make connections with other neurons

When is this process of the neurons migrating and making connections completed?

by the end of the prenatal period

What is the structure of the embryo on day 14?

a 2-layered structure

What happens on day 21?

the embryo undergoes gastrulation, resulting in 3 layers: endoderm, mesoderm, and ectoderm

Which layer contains neurectodermal stem cells and what do they form?

the ectoderm, it gives rise to the brain and central nervous system

When do the neural plate develop?

18 to 20 days after conception

What do the neural plate form?

neural tube and neural crest

Neural tube differentiates into CNS, which consists of _______ and _________.

the brain and spinal cord

Neural crest gives rise to most of structures in ____________ system.

peripheral nervous

What structures are contained within the cranial cavity?

the brain, its surrounding meninges, and portions of the cranial nerves, arteries, veins, and venous sinuses

What are unossified spaces between the bones of the infant skull that allow for compression at birth and rapid brain growth?

fontanels

How do fontanels assist in sonography?

they provide acoustic windows to image the brain

What 2 fontanels we scan through?

anterior and posterior (mastoid)

Which fontanel is the largest at birth?

anterior fontanel

The anterior fontanel provides a window from ___ to ___ months of age.

9 to 12

If hydrocephalus is present, it is felt to be bulging where?

in the anterior fontanel

What are the three meninges that surround and protect the brain?

dura mater, arachnoid mater, and pia mater

Which meninge lies directly against the brain parenchyma?

pia mater

Which meninge is located in the middle?

arachnoid mater

Which meninge is the tough, double-layered outer membrane?

dura mater

Where is the subarachnoid space located?

between the pia mater and arachnoid mater

What does the subarachnoid space contain?

cerebrospinal fluid (CSF) and branches of the arteries and veins of the brain

What is the significance of the interaction between the vascular channels (arteries and veins) and CSF?

it plays an important role in the blood-brain barrier

What is the falx cerebri?

a fibrous structure that separates the two cerebral hemispheres

What is the tentorium cerebelli?

a V-shaped echogenic structure that separates the cerebrum and cerebellum and is an extension of the falx cerebri

Where are the lateral ventricles located?

within the cerebral hemispheres

What fills the lateral ventricles?

cerebrospinal fluid (CSF)

What is the function of CSF in the lateral ventricles?

it surrounds and protects the brain and spinal cord from physical impact

Where are the lateral ventricles located in relation to the brain?

on either side of the brain

How do the lateral ventricles communicate with the third ventricle?

through the interventricular foramen (foramen of Monro)

Into how many segments are the lateral ventricles divided?

four segments

What are the four segments of the lateral ventricles?

frontal horn, body, occipital horn, and temporal horn

Where is the third ventricle located?

inferior and midline between the lateral ventricles

What forms the roof of the third ventricle?

the corpus callosum

At what gestational age is the third ventricle not visualized?

beyond 32 weeks of gestation

What connects the third and fourth ventricles?

the aqueduct of Sylvius

Why is the aqueduct of Sylvius clinically important in neonates?

is the most common site for intraventricular blockage of CSF

What is the shape of the fourth ventricle?

diamond-shaped

Where is the fourth ventricle located?

within the pons (upper portion of the brainstem), between the cerebellar peduncles

What forms the floor of the fourth ventricle?

the medulla oblongata