OB GYN (Part 2) Boards Ch. 23 - 25

SUBCHORIONIC HEMORRHAGE

- Small, benign subchorionic hemorrhages can be seen during a routine first-trimester ultrasound examination - subchorionic hemorrhage is essentially a bleed between the endometrium & the gestational sac, & therefore may be referred to as a perigestational hemorrhage.

Placenta and Umbilical Cord

- The developing placenta may be noted at the end of first trimester as a well-defined, crescent-shaped homogenous mass of tissue, along the margins of the gestational sac. - placenta is formed by the decidua basalis, the maternal contribution of the placenta, and the chorion frondosum, the fetal contribution. - umbilical cord is visible during the later half of the first trimester as a tortuous structure connecting the fetus to the developing placenta.

Decidual reaction

- The effect on the endometrium in the presence of a pregnancy

EMBRYONIC DEMISE

- With transvaginal imaging, cardiac activity should be detected in the pole that measures 4- 5 mm - The causes of embryonic death are often idiopathic but may be linked w/ chromosomal abnormalities. - Clinically, patients present small for dates & typically have vaginal bleeding w/ a closed cervix. - it is important to evaluate the appearance of the yolk sac, as a yolk sac that is echogenic, abnormally shaped, or calcified carries an increased risk for ensuing embryonic demise. LINICAL FINDINGS OF EMBRYONIC OR FETAL DEMISE 1. Vaginal bleeding 2. Small for dates 3. Closed cervix 4. Low (based on LMP) hCG SONOGRAPHIC FINDINGS OF EMBRYONIC OR FETAL DEMISE 1. No detectable fetal heart activity in a pole that measures 4 to 5 mm 2. Irregularly shaped fetus 3. Irregularly sized gestational sac 4. Irregular-appearing yolk sac (misshapen, calcified, or echogenic)

falx cerebri

- a double fold of dura mater located within midline of the brain

Meckel-Gruber syndrome

- a fetal syndrome associated w/microcephaly, occipital encephalocele, polydactyly, and polycystic kidneys

anencephaly

- a neural tube defect that is described as the absence of the cranium and cerebral hemispheres

Cistern

- a prominent space within the skull that contains cerebrospinal fluid; a cistern is created by the separation of the arachnoid membrane and pia mater

corpus callosum

- a thick band of white matter that provides communication between right and left halves of the brain

Colpocephaly

- abnormal lateral ventricle shape in which there is a small frontal horn and enlarged occipital hornabnormal lateral ventricle shape in which there is a small frontal horn and enlarged occipital horn

Macrocephaly

- an enlarged head circumference

Mega Cisterna Magna

- an enlargement of the cisterna magna as defined by a depth of >10 mm

gastroschisis

- birth defect of the abdominal (belly) wall. The baby's intestines are found outside of the baby's body, exiting through a hole beside the belly button.

Cebocephaly

- close-set eyes (hypotelorism) and a nose w/ a single nostril - Cebocephaly is part of a group of defects called holoprosencephaly.

NORMAL SONOGRAPHIC FINDINGS DURING THE FIRST TRIMESTER: Decidual Reaction (Weeks 3 to 4)

- decidual reaction of the endometrium is essentially the first sonographically identifiable sign of a pregnancy. In essence, the endometrium is preparing itself for the implantation of the conceptus. - The decidualized endometrium will appear thick & echogenic as a result of the continued production of progesterone by the corpus luteum - endometrium can also appear thick/echogenic during the secretory phase of the endometrial cycle & in the presence of an ectopic pregnancy. A correlation between hCG levels & sonographic findings should be performed.

Arachnoid cyst

- develop between the surface of the brain and the cranial base or on the arachnoid membrane, one of the three meningeal layers that cover the brain and the spinal cord. - benign cysts within the brain that do not communicate with the ventricular system

Cerebral Aqueduct (Aqueduct of Sylvius)

- duct that connects the third ventricle of the brain to the fourth ventricle; also referred to as the aqueduct of Sylvius

hCG AND THE DISCRIMINATORY ZONE

- hCG can be detected in the maternal urine & serum (blood). - hCG is detected in the maternal blood as early as 23 days menstrual age. - Typically, a 5-mm gestational sac will be seen at approx. 5 menstrual weeks. - Normal hCG levels double every 48 hours in the first trimester. - High & low levels of hCG compared w/ LMP & sonographic findings can be indicative of an abnormal pregnancy - hCG level will continue to rise until the end of the first trimester, at which time it plateaus & slowly decreases w/ advancing gestation TABLE 23-1 Human Chorionic Gonadotropin Levels Compared with Normal Pregnancy Nature of Pregnancy hCG Level Ectopic pregnancy = Low Anembryonic pregnancy = Low Abortion (miscarriage) = Low Twin pregnancy = High Molar pregnancy = Very High

meningocele

- herniation of the cranial or spinal meninges due to an open cranial or spinal defect

Brain stem

- lower part of the brain composed of the pons, midbrain, and medulla oblongata

interthalamic adhesion (massa intermedia)

- mass of tissue, located in the third ventricle within the midline of the brain, which connects the two lobes of the thalamus; also referred to as the massa intermedia

Lissencephaly

- "smooth brain"; condition where there is little to no gyri or sulci within the cerebral cortex

Dandy-Walker Malformation and Mega Cisterna Magna

- (DWM) is actually a classification within a larger group of anomalies referred to as the Dandy-Walker complex - Dandy-Walker complex is a spectrum of posterior fossa abnormalities that involve the cystic dilatation of the cisterna magna & 4th ventricle. - DWM is thought to be caused by a developmental abnormality in the roof of the 4th ventricle. - sono findings of DWM include an enlarged cisterna magna that communicates w/ a distended 4th ventricle through a defect in the cerebellum. - cerebellar vermis is either completely absent or hypoplastic. As a result, the tentorium, the structure that separates the cerebrum from the cerebellum, is elevated. - agenesis of the corpus callosum, ventriculomegaly, holoprosencephaly, & cephaloceles are all associated anomalies that can co-exist w/ DWM - Mega cisterna magna present when only the cisterna magna is enlarged, measuring more than >10 mm in depth. - Consequently, the 4th ventricle is normal w/ mega cisterna magna & enlarged only w/ DWM * Important to note; early 2nd trimester, the inferior portion of the cerebellar vermis may not be formed, thus making it appear as if the fetus has partial agenesis of the vermis. * For that reason, care must be taken to visualize an intact cerebellar vemis. If the cerebellar vermis is absent & the 4th ventricle is enlarged, then DWM must be suspected!

Arnold-Chiari II Malformation & Spina Bifida

- Arnold-Chiari II or Chiari II malformation is a group of cranial abnormalities associated w/ the neural tube defect spina bifida. - Spina bifida may result in a mass that protrudes from the spine. This mass can be referred as a meningocele or myelomeningocele, depending on its contents - Most common location of spina bifida is within the distal lumbosacral region. - Several notable changes occur within the brain & skull w/ spina bifida - Frontal bones become flattened & will yield a lemon shape to the cranium, which is referred to as the "lemon" sign - Cerebellum will become displaced inferiorly & posteriorly & appear curved in the presence of spina bifida, which is referred to as the "banana" sign - As a result of the cerebellum being displaced inferiorly, the cisterna magna is completely destroy. - posterior fossa abnormality such as Chiari II malformation should be suspected if the cisterna magna is not visualized.

EMBRYOLOGIC DEVELOPMENT OF THE FETAL BRAIN

- By 4.5 wks the neural plate (structure) will form the central nervous system. - neural plate will give rise to the neural tube, which will become the spine & the brain. - Initially, the brain is separated into 3 primary vesicles: prosencephalon (forebrain), mesencephalon (midbrain), and rhombencephalon (hindbrain). - Sonographically, the rhombencephalon may be noted within the fetal cranium during the first trimester

Corpus Callosum

- Corpus Callosum forms late in gestation, but should be completely intact b/w 18 & 20 weeks. - (CC) connects the two lobes of the cerebrum - (CC) consists of 4 parts: 1) Rostrum 2) Genu 3) Body 4) Splenium -Fetal development of the (CC) is from anterior to posterior. - sonographic app. of the corpus callosum is that of an echogenic band of tissue within the midline of the brain

Agenesis of the Corpus Callosum & Cavum Septum Pellucidum

- Corpus Callosum functionally provides a pathway for communication b/w the 2 cerebral hemispheres & is completely formed by 18 weeks. - CSP, located inferior to the corpus callosum, & develop at the same time. - There can be partial/ complete absence of the corpus callosum - Most often, if the corpus callosum is absent, the CSP will be absent as well. * Their non-existence has been linked to as many as 50-200 different syndromes & anomalies such as holoprosencephaly, Dandy-Walker malformation, aqueductal stenosis, trisomy 18, trisomy 8, and trisomy 13.

Head Circumference (HC)

- HC measurement is typically more accurate than BPD because this measurement is independent of the fetal head shape, consequently providing a more consistent parameter for estimating gestational age.

THE EFFECTS OF FETAL INFECTIONS ON THE BRAIN

- Maternal serum screening for intrauterine infections resulting from toxoplasmosis, other agents, rubella, cytomegalovirus, & Herpes simplex virus (TORCH) - Cytomegalovirus has been listed as the most common in utero infection - sonographic intracranial findings consistent w/ intrauterine infections are the calcifications around the ventricles & ventriculomegaly

FETAL INTRACRANIAL TUMORS

- Most common intracranial tumor found in utero is the teratoma.Teratomas contain tissues such as hair, sebum, & fat & most often appear as complex masses that distort the normal architecture of the brain. - Choroid plexus papillomas are found within the choroid plexus & produce an increase in the production of CSF, which in turn leads to ventriculomegaly. - sonographic findings associated w/ brain tumors are macrocephaly & intracranial calcifications. - Corpus callosum lipomas may also be present w/ agenesis of the corpus callosum. A lipoma will appear as a solid echogenic mass.

Nuchal Fold Measurement and Nuchal Translucency Measurement

- Nuchal thickening, edema, or redundant skin in the back of the neck is a common finding during the 2nd trimester in fetuses w/ Down syndrome - Meas. of >6 mm or larger is considered abnormal. (Nuchal fold) - Nuchal fold meas. are performed later in gestation compared to nuchal translucency meas. Nuchal folds are typically measured anywhere between 15 & 19 weeks - Nuchal translucency meas. can be performed earlier & is most accurately meas. between 11 & 14 weeks * important to note that the nuchal thickening may completely resolve as the pregnancy progresses

SCHIZENCEPHALY

- Rare birth defect. It causes slits or clefts in the cerebral hemispheres of the brain. These clefts may appear on one or both sides of brain. They may be filled with cerebrospinal fluid. - SONOGRAPHIC FINDINGS OF SCHIZENCEPHALY: 1. Fluid-filled clefts within the cerebrum 2. Agenesis of the cavum septum pellucidum and corpus callosum (50% of the time) 3. Ventriculomegaly

Porencephaly

- Rare condition in which a cyst communicates w/ the ventricular system - Can occur after the fetus has experienced hemorrhage within one or both of the cerebral hemispheres. - As the hemorrhage changes states, it will form into a cystic cavity & will eventually communicate w/ the lateral ventricle of the affected side. - Arachnoid cysts can be confused w/ porencephaly. It is important to note that arachnoid cysts will not communicate w/ the ventricular system. SONOGRAPHIC FINDINGS OF PORENCEPHALY: 1. Cystic mass that communicates with the lateral ventricle 2. Most often unilateral

Acrania (Anencephaly & Exencephaly)

- Remains one of the Most Common neural tube defects. - Acrania is defined as the absence of the cranial vault above the bony orbits. - two main subtypes that are related to the amount of cerebral tissue present, anencephaly & exencephaly. 1) Anencephaly- is considered when there are no cerebral hemispheres present, whereas 2) Exencephaly- denotes a normal amount of cerebral tissue. - Nonetheless, the cranium is absent, making this condition fatal. - Sono appearance of anencephaly has been described as having "froglike" facies, or bulging eyes, & absence of the cranial vault

Lateral Ventricle Measurement

- The section (atrium) of the lateral ventricle is the optimal site for measuring the lateral ventricle, b/c it is the first region where ventricular enlargement occurs. - normal lateral ventricle does not typically measure more than 10 mm at the level of the atrium.

Holoprosencephaly and Fetal Facial Abnormalities

- Whenever any form of holoprosencephaly is suspected, a thorough facial evaluation should be performed - facial abnormalities that have been linked w/ holoprosencephaly are hypotelorism, cebocephaly (monkey-like head), ethmocephaly, cyclopia, & cleft lip with or without cleft palate

Holoprosencephaly

- a cephalic disorder in which the prosencephalon (the forebrain of the embryo) fails to develop into two hemispheres. Normally, the forebrain is formed and the face begins to develop in the fifth & sixth weeks of human pregnancy. - can also affect facial features, including closely spaced eyes, small head size, and sometimes clefts of the lip and roof of the mouth, as well as other birth defects. - may be detected w/ endovaginal imaging as early as the first trimester. - 3 main types of holoprosencephaly: 1) Alobar (most severe )- absence of the corpus callosum, CSP, 3rd ventricle, interhemispheric fissure, and falx cerebri. There will also be evidence of a horseshoe shaped monoventricle & thalamus lobes may be fused & echogenic 2) Semilobar- incomplete forebrain division. 3) Lobar- Infants w/ lobar holoprosencephaly may experience severe mental retardation. Trisomy 13 (Patau syndrome), is present in 50% - 70% of fetuses diagnosed w/ holoprosencephaly. - Although the (lobar) form can be consistent w/ life, (alobar) holoprosencephaly is the most severe form, often resulting in neonatal death. - cerebellum & brain stem remain intact. - 2 most disturbing external findings associated w/ holoprosencephaly: 1) Cyclopia, a condition in which orbits are fused & contain a single eye, & 2) Proboscis, a false nose situated above the orbits - Other facial anomalies: such as 1) Anophthalmia (absence of one or both eyes) 2) Hypotelorism (abnormal decrease distance b/w the two eyes), 3) Median cleft lip 4) Cebocephaly (developmental anomaly of head characterized by a monkey-like head, with a defective small, flattened nose w/a single nostril or absent nose & closely set eyes) may be detected during a fetal sonogram as well.

Turner syndrome

- a chromosomal aberration where one sex chromosome is absent; may also be referred to as monosomy X

Porencephaly

- a condition in which a cyst, most often caused by an intraparenchymal hemorrhage, communicates w/ a lateral ventricle

Ethmocephaly

- a condition in which there is no nose & a proboscis separating two close-set orbits; associated with holoprosencephaly

Aneuploidy

- a condition of having an abnormal number of chromosomes

triploidy

- a fetus that has three of every chromosome * Three sets, or 69 chromosomes, are called a triploid set

holoprosencephaly

- a group of brain abnormalities consisting of varying degrees of fusion of the lateral ventricles, absence of the midline structures, and associated facial anomalies

Beckwith-Wiedemann syndrome

- a growth disorder syndrome synonymous w/ enlargement of several organs including the skull, tongue, and liver

Micrognathia

- a small mandible & recessed chin

FETAL NECK ABNORMALITIES Cystic Hygroma

- abnormal accumulation of lymphatic fluid within the soft tissue. The most common location of a cystic hygroma is within the neck, although it may be found within the axilla. * should not be confused w/ increased nuchal translucency or nuchal fold thickening - have been found in many syndromes & chromosomal abnormalities such as Turner syndrome, fetal hydrops, aneuploidy, trisomy 21, trisomy 18, and trisomy 13. SONOGRAPHIC FINDINGS OF A CYSTIC HYGROMA: 1. Cystic neck mass divided in the midline by a thick f ibrous band of tissue 2. The mass may contain smaller cystic areas with internal septations

CEREBRAL MALFORMATIONS: Ventriculomegaly & Hydrocephalus

- abnormal enlargement of ventricles within the brain is referred to as ventriculomegaly. - Hydrocephalus is typically reserved for the cases of ventriculomegaly that are more severe & are caused by some type of obstruction to the flow of CSF. - Ventriculomegaly is Most Common cranial abnormality - Sono finding of the "dangling choroid" sign describes the echogenic choroid plexus, hanging limp, & surrounded by CSF, within the dilated lateral ventricle (>10 mm). This finding is exceedingly specific for ventriculomegaly. - Hydrocephalus can be described as Mild, Moderate, or Severe. - Two main types of hydrocephalus: 1) Communicating hydrocephalus - is apparent when the obstruction lies outside of the ventricular system 2) Noncommunicating hydrocephalus - when obstruction level is located within the ventricular system. - Aqueductal stenosis, remains the most common cause of hydrocephalus in fetus

Anophthalmia

- absence of the eye(s). - failure of the optic vesicle to form & has been linked w/ multiple abnormalities & chromosomal aberrations, including trisomy 13 & trisomy 18. - hypertelorism, a disorder more accurately diagnosed utilizing the interocular diameter - most common cause of hypertelorism is the existence of an anterior cephalocele that displaces the orbits laterally. (also associated w/ craniosynostosis & many chromosomal abnormalities.)

hydrops (fetal)

- an abnormal accumulation of fluid in at least two fetal body cavities

TORCH infections

- an acronym that stands for toxoplasmosis, other infections, rubella, cytomegalovirus, and herpes simplex virus; this group of infections may be acquired by a woman during pregnancy

Vein of Galen aneurysm

- an arteriovenous malformation that occurs within the fetal brain and is associated with congestive heart failure

epignathus

- an oral teratoma

Macroglossia

- an unusual protuberance of the tongue. Severe enlargement of the tongue

omphalocele

- anterior abdominal wall defect where there is herniation of the fetal bowel and other abdominal organ into the base of the umbilical cord

The Cerebrum

- brain can be divided into two main parts, the cerebrum & the cerebellum - There are six cerebral lobes: the frontal lobe, two temporal lobes, two parietal lobes, & the occipital lobe. - cerebrum can be further divided into a right and left hemisphere by the interhemispheric fissure. - falx cerebri, a double fold of dura mater, is located within the interhemispheric fissure (linear echogenic coursing midline fetal brain) - cerebral hemispheres are linked in the midline by the corpus callosum, a thick band of tissue that provides communication b/w right & left halves of the brain. - meninges are 3 protective tissues layers that cover the brain and the spinal cord: innermost= pia mater middle= arachnoid membrane outermost= dura mater

Biparietal Diameter (BPD)

- can be taken after the first trimester has ended, typically starting b/w 13 & 14 weeks. - BPD is obtained in the axial plane at the level of the CSP, thalamus, and falx cerebri (same level as the 3rd ventricle, which may be seen b/w the two lobes of the thalamus

Transcerebellar Measurement

- cerebellum grows @ a rate of 1 mm per week b/w 14 & 21 weeks & thus correlates agreeably w/ the gestational age of the fetus - 16-week fetus will measure approx. 16 mm

Aqueductal Stenosis (aqueduct of Sylvius)

- cerebral aqueduct (aqueduct of Sylvius), located b/w 3rd & 4th ventricle of the brain, may be narrowed, thus preventing the flow of CSF from the 3rd to the 4th ventricle. - This obstruction level will cause the 3rd ventricle & both lateral ventricle to expand, whereas the 4th ventricle remains normal.

Ventricular System

- composed 4 ventricles, whose primary function is to provide cushioning for the brain. - Each ventricle is lined by a membrane called the ependyma. - paired lateral ventricles are located on both sides of the falx cerebri within the cerebral hemispheres - referred to as right & left ventricles but may also be called the first & second ventricles - each lateral ventricle consists of a frontal, temporal, and occipital horn - Within the atria of both lateral ventricles lies the echogenic configuration of the choroid plexus, the mass of cells responsible for cerebrospinal fluid (CSF) production in the fetus - Choroid plexus may also be found in the roof of the third & fourth ventricles. - lateral ventricle communicates w/ the 3rd ventricle in the midline of the brain at the foramen of Monro (interventricular foramina) - 3rd ventricle connects to the 4th ventricle inferiorly by means of a long, tubelike structure called (aqueduct of Sylvius, or the cerebral aqueduct). -4th ventricle is located anterior to the cerebellum within the midline of the brain. - has three apertures or openings through which CSF travels - There are 2 lateral apertures that are also referred to as the foramina of Luschka. These two apertures allow CSF to travel from the 4th ventricle to the subarachnoid space around the brain. Another opening of the 4th ventricle, located in the midline, is the median aperture, also referred to as the foramen of Magendie - This opening allows CSF to pass from the 4th ventricle to the cisterna magna and subarachnoid space. - Arachnoid granulations, also referred to as arachnoid villi, are responsible for the reabsorption of CSF into the venous system

Choroid Plexus Cysts

- cysts located within the choroid plexus of the lateral ventricles. - small cysts are frequently encountered during a routine sonographic examination & typically regress by the end of the 3rd trimester, although they are associates w/ an increased risk of trisomy 18 (edwards). * measure more than >2 mm, appear round & anechoic, & have smooth walls

NEURAL TUBE DEFECTS AND THE BRAIN

- defects occur when the embryonic neural tube fails to close. Among the list of neural tube defects are cephaloceles, various spinal dysraphisms, anencephaly, & spina bifida. - Anencephaly & spina bifida are the most common neural defects, occurring in 1 per 1,000 pregnancies. - Although several causes have been implicated, such as maternal diabetes & the use of valproic acid (seizure medication), chromosomal anomalies, including Edwards syndrome (trisomy 18), Patau syndrome (trisomy 13), & triploidy, have all been linked with neural tube defects. - Screening neural tube defects is achieved by a combination of sonography, amniocentesis, and/or maternal serum screening. - Maternal serum screening, also referred to as the triple-screen, combines: laboratory values of hCG, estriol, & maternal serum alpha-fetoprotein (MSAFP), particularly, helpful for detecting neural tube defects is the MSAFP component of this test. - (AFP) is initially produced by the yolk sac, fetal gastrointestinal tract, & the fetal liver. AFP exits the fetus through an opening in the neural tube if one is present (i.e., an opening in the cranium or spine), thus allowing for a greater amount to pass into the maternal circulation. - increased levels of AFP may not always mean that a neural tube defect is present. Elevated levels of AFP are also found w/ omphalocele, gastroschisis, multiple gestations, fetal demise, & incorrect gestational dating.

Cisterna Magna Measurement

- depth of the cisterna magna should not measure more than 10 mm or less than 2 mm - Measurement >10 mm is consistent w/ mega cisterna magna & Dandy-Walker complex, whereas a measurement <2 mm is worrisome for Arnold-Chiari II malformation.

Hydranencephaly

- fatal condition in which the entire cerebrum is replaced by a large sac containing CSF - With hydranencephaly, the falx cerebri partially or completely absent, whereas the brain stem & basal ganglia are maintained & surrounded by CSF. There will be no cerebral cortex identified. - Hydranencephaly can be difficult to differentiate w/ the sonographic findings of hydrocephalus & alobar holoprosencephaly. - It is important to note that w/ both hydrocephalus & holoprosencephaly there will be a rim of cerebral tissue maintained, whereas w/ hydranencephaly there is no cerebral mantle present. - Hydranencephaly is typically a fatal condition, w/ death occurring in the first year of life.

Fetal Mouth, Lip, and Mandible

- fetal lip typically closes between 7 & 8 weeks, while the palate closes by 12 weeks - Cleft lip & cleft palate are among the most common congenital abnormalities & have been associated w/ many syndromes & congenital anomalies, such as holoprosencephaly, trisomy 13, & amniotic band syndrome - Cleft lip can be unilateral, bilateral, or midline in location - Macroglossia is defined as an unusual protuberance of the tongue. It is most commonly associated w/ Beckwith-Wiedemann syndrome & Down syndrome. - Macroglossia can be difficult to differentiate from epignathus, which is a mostly solid-appearing oral teratoma. Teratomas most often contain complex tissue, while the enlarged tongue is completely solid. - Micrognathia, a small mandible & recessed chin, is associated w/ trisomy 13 & trisomy 18 & has been found in several other syndromes & chromosomal aberrations. Micrognathia is best visualized in the sagittal view of the fetal face

sulci

- grooves within the brain

(Ch. 25) Fetal Face & Neck Amniotic band syndrome

- group of abnormalities associated with the entrapment of fetal parts in the amnion, often resulting in fetal amputations or clefting

spinal dysraphism

- group of neural tube defects that describe some manifestation of incomplete closure of the spine

pia mater

- innermost layer of the meninges

FETAL INTRACRANIAL HEMORRHAGE (INTRAVENTRICULAR HEMORRHAGE)

- intracranial hemorrhage is a common finding in premature infants weighing less than 1500g and those born before 32 weeks gestation - Maternal use of cocaine, trauma, & a history of amniocentesis are all listed as predisposing condition of fetal intracranial hemorrhage; however, the most common risk factor for fetal intrauterine intracranial hemorrhage has been listed as maternal platelet disorders. - Most often, the origin of intracranial hemorrhage, also referred to as intraventricular hemorrhage, is within the germinal matrix. - germinal matrix is a group of thin-walled, pressure-sensitive vessels located in the subependymal layer of the ventricles - These vessels are prone to rupture secondary to their thin walls. - hemorrhage can spread into the lateral ventricle, often leading to noncommunicating hydrocephalus, as the clot obstructs the flow of CSF within the narrowed regions of the ventricular system - Hemorrhage can also occur within the parenchyma of the brain (cerebrum). - Localized areas of hemorrhage within the cerebral hemispheres will eventually lead to the formation of cystic cavities that communicate w/ the ventricular system, a condition known as porencephaly.

Lissencephaly

- literally means "smooth brain." - condition in which there are no gyri (folds or ridges) within the cerebral cortex -Agyria (w/out gyri), & the absence of sulci within the brain, is not typically diagnosed until the 3rd trimester or postnatally & almost always carries a poor prognosis SONOGRAPHIC FINDINGS OF LISSENCEPHALY: 1. Lack of sulci and gyri within the cerebrum

The Cerebellum

- located in the posterior fossa of the cranium - consists of two hemispheres, right & left, that are coupled at the midline by the cerebellar vermis - cerebellar tonsils, named for their shape, are located on the undersurface of the cerebellum & become distorted with spina bifida & Arnold-Chiari malformations (condition- brain tissue extends into the spinal canal, present at birth)

binocular diameter

- measurement made from the lateral margin of one orbit to the lateral margin of the other orbit

Cavum Septum Pellucidum (CSP)

- midline brain structure, located at the anterior portion of the brain b/w the frontal horns of the lateral ventricles. - appear as an anechoic "box-shaped" structure - CSP should always be seen b/w 18-37 weeks. - closure of (CSP) is normal in later gestation & often occurs before birth or shortly thereafter - CSP does not communicate w/ the ventricular system & its absence is associated w/ multiple cerebral malformations.

Thanatophoric Dysplasia (dwarfism)

- most common lethal skeletal dysplasia (severe disorder of bone growth) characterized by a cloverleaf skull with frontal bossing and hydrocephalus - severe skeletal disorder characterized by extremely short limbs and folds of extra (redundant) skin on the arms and legs. Other features of this condition include a narrow chest, short ribs, underdeveloped lungs, and an enlarged head with a large forehead and prominent, wide-spaced eyes.

Prosencephalon (forebrain)

- primary brain vesicle also referred to as the forebrain; becomes the lateral ventricles, cerebral hemispheres, third ventricle, thalamus, hypothalamus, pineal gland, and pituitary gland

Cephaloceles

- protrusions of intracranial contents through a defect in the skull - can also be distinguished by their location - Most common location for a cephalocele is in the occipital region - cephaloceles may also have frontal & parietal positions - common findings in Meckel-Gruber syndrome & have varying sonographic appearances based on their content. SONOGRAPHIC FINDINGS OF CEPHALOCELES: 1. Open cranial defect (typically posterior in location) 2. Small or obliterated cisterna magna 3. Complex mass protruding from the cranium

NORMAL FETAL SKULL AND BRAIN ANATOMY

- skull consists of eight cranial bones. These bones are connected by structures known as sutures - B/c of the flexibility of sutures, the fetal cranial bones remain slightly mobile until delivery to facilitate the passage of the skull through the birth canal. - Premature fusion of the sutures is termed craniosynostosis. Consequently, craniosynostosis leads to an irregular-shaped skull. - Spaces that exist b/w the forming fetal bones are referred to as fontanelles, or "soft spots" - Several fontanelles persist in the postnatal period & into infancy. - Fontanelles are often utilized as sonographic windows during neurosonographic examinations to evaluate newborns for intracranial hemorrhage or suspected brain anomalies. - anterior fontanel, when completely filled with bone, is referred to as the [bregma], whereas the posterior fontanel is referred to as the [lambda].

Subependymal (layer)

- the area just beneath the ependymal lining of the lateral ventricles

Rhombencephalon (hindbrain)

- the primary brain vesicle also referred to as the hindbrain; becomes the cerebellum, pons, medulla oblongata, and fourth ventricle

Fetal Orbital Abnormalities

- there are 3 measurements that can be obtained in the transverse plane of the fetal face at the level of the eyes 1) Ocular diameter - performed from the lateral wall of the orbit to the medial wall of the same orbit. * This meas. should only be slightly smaller than Interocular meas. 2) Interocular diameter- length between the both orbits. 3) Binocular diameter- lateral margin of one orbit to the lateral margin of the other orbit. * obtained at the same level, & it includes both of the orbits.

Thalamus

- two lobes of the thalamus are located on both sides of the 3rd ventricle. - The massa intermedia/ interthalamic adhesion passes through the 3rd ventricle to connect the two lobes of the thalamus

Cephalic Index & Fetal Head Shape

- useful tool for indicating the shape of the fetal head - Brachycephalic (brachycephaly) head shape is one that is considered round or short and wide - Dolichocephaly (Scaphocephaly) denotes an elongated, narrow head shape. - Other abnormal skull shapes include strawberry, lemon, and cloverleaf. These abnormal shapes are associated w/ fetal anomalies - normal-sized to medium-sized skull is termed Mesocephalic. - formula used to calculate the cephalic index considers the BPD & the OFD as in: cephalic index = BPD/OFD x 100 - cephalic index of less than <75 denotes a dolichocephalic shape, whereas an index of more than >85 denotes a brachiocephalic shape.

Fetal Intracranial Vascular Anomalies

- vein of Galen aneurysm is an arteriovenous malformation that occurs within the fetal brain. - sono findings: vein of Galen aneurysm is that of a large, anechoic mass within the midline of the cranium that when interrogated w/ color & pulsed Doppler fills w/ turbulent venous & arterial flow. SONOGRAPHIC FINDINGS OF VEIN OF GALEN ANEURYSM: 1. Anechoic mass within the midline of the brain that contains turbulent arterial and venous flow when interrogated with pulsed and color Doppler. 2. Fetal hydrops 3. Cardiomegaly (caused by cardiac overload)

folate

- vitamin that has been shown to significantly reduce the likelihood of neural tube defects; also referred to as folic acid

FACIAL ANOMALIES OF ALOBAR HOLOPROSENCEPHAL

1. Cyclopia 2. Hypotelorism 3. Proboscis 4. (Median) cleft lip 5. Anophthalmia 6. Cebocephaly SONOGRAPHIC FINDINGS OF ALOBAR HOLOPROSENCEPHALY: 1. Horseshoe-shaped monoventricle 2. Fused echogenic thalami 3. Absence of the cavum septum pellucidum, interhemispheric fissure, falx cerebri, corpus callosum, and third ventricle 4. Normal cerebellum and brain stem

SONOGRAPHIC FINDINGS OF DANDY-WALKER MALFORMATION

1. Enlargement of the cisterna magna 10 mm in the anteroposterior dimension 2. Communication of the enlarged cisterna magna with a dilated 4th ventricle 3. Agenesis or hypoplasia of the cerebellar vermis 4. Varying degrees of ventriculomegaly

SONOGRAPHIC FINDINGS OF MEGA CISTERNA MAGNA

1. Enlargement of the cisterna magna 10 mm in the anteroposterior dimension 2. Normal cerebellum and 4th ventricle

SONOGRAPHIC FINDINGS OF ARNOLD-CHIARI II MALFORMATION

1. Lemon sign—lemon-shaped cranium with flattened frontal bones 2. Banana sign—banana-shaped cerebellum 3. Obliterated cisterna magna 4. Colpocephaly 5. Enlarged massa intermedia 6. Hydrocephalus 7. Open spinal defect

SONOGRAPHIC FINDINGS OF AGENESIS OF THE CORPUS CALLOSUM AND CAVUM SEPTUM PELLUCIDUM

1. Partial or complete absence of the corpus callosum and absence of the cavum septum pellucidum (after 18 weeks) 2. "Sunburst" sign—radial arrangement of the sulci 3. Colpocephaly—small frontal horns and enlarged occipital horns (teardrop-shaped lateral ventricles) 4. Elevated and dilated third ventricle

DOPPLER INTERROGATION OF THE FETAL BRAIN

Doppler of the Middle Cerebral Artery: - Doppler assessment of the middle cerebral artery (MCA) has been shown effective at evaluating for hypoxia in fetuses small for dates. - Pulsatility index (PI) of the MCA varies w/ gestational age but normally decreases as the pregnancy progresses toward term - resistance pattern of the MCA should be greater than that of the umbilical artery & thus should be compared when fetal shunting is suspected.

TABLE 24-5 Fetal Head Shapes and Associated Anomalies

Head Shape /Associated Anomalies Lemon: - Chiari II malformation Strawberry: - Trisomy 18 Cloverleaf: - Thanatophoric dysplasia (dwarfism Skeletal Disorder) Microcephaly: - TORCH infections - Trisomy 13 & trisomy 18 - Meckel-Gruber syndrome - Fetal alcohol syndrome Macrocephaly: - Hydrocephalus - Hydranencephaly - Intracranial tumors - Familial inheritance - Beckwith-Wiedemann syndrome Brachycephaly: - Craniosynostosis - Trisomy 21 (Downs) - Trisomy 18 (Edwards) Dolichocephaly: - Craniosynostosis

Midline Brain Anatomy

Midline Brain Anatomy: - Falx cerebri - Interhemispheric fissure - Corpus callosum - Cavum septum pellucidum - Third ventricle - Aqueduct of Sylvius (cerebral aqueduct) - Fourth ventricle - Cerebellar vermis - Cisterna magna - Interthalamic adhesion (massa intermedia) Bilateral Brain Structures (located both sides of midline): - Hemispheres of the cerebellum - Hemispheres of the cerebrum - - Lobes of the thalamus - Foramen of Monro (interventricular foramina) - Lateral ventricles - Choroid plexus (within lateral ventricles)

Choriocarcinoma

Most Malignant form of gestational trophoblastic disease w/ possible metastasis to the liver, lungs, and vagina - growing cancer that occurs in a woman's uterus. The abnormal cells start in the tissue that would normally become the placenta. This is the organ that develops during pregnancy to feed the fetus.

Posterior Fossa Abnormalities and Their Sonographic Findings

Posterior Fossa Abnormality: 1) Mega cisterna magna Sono Findings: - Enlargement of the cisterna magna >10 mm in the anteroposterior dimension - Normal cerebellum 2) Dandy-Walker malformation Sono Findings: - Enlargement of the cisterna magna >10 mm in the anteroposterior dimension - Absent cerebellar vermis - Enlarged 4th ventricle 3) Arnold-Chiari II malformation Sono Findings: - Obliterated cisterna magna - Banana-shaped cerebellum - Lemon-shaped skull

Fetal Sutures and Their Locations

Sutures Coronal suture: B/w the frontal and two parietal bones Sagittal suture: B/w the two parietal bones Lambdoidal suture: B/w the parietal bones & occipital bone Squamosal sutures (2): B/w the parietal bones & temporal bones Metopic suture: Located within the frontal bone along the midline of the forehead

Decidua Basalis

The endometrial tissue at the implantation site, and the maternal contribution of the placenta. * The fetal part of the placenta is known as the chorion. The maternal component of the placenta is known as the decidua basalis.

24-7 Table Providing the Different Types of Cephaloceles and Their Contents

Type of Cephalocele: - Meningocele Meninges only - Encephalocele Brain tissue only - Encephalomeningocele Both meninges and brain tissue - Encephalomeningocystocele Meninges, brain tissue, and lateral ventricle

Turner Syndrome

a chromosomal aberration where one sex chromosome is absent; may also be referred to as monosomy X * chromosomal condition that alters development in females. Women with this condition tend to be shorter than average and are usually unable to conceive a child (infertile) because of an absence of ovarian function

eclampsia

a sequela of preeclampsia in which uncontrollable maternal hypertension & proteinuria lead to maternal convulsions & possibly fetal & maternal death

Dandy-Walker complex

a spectrum of posterior fossa abnormalities that involve the cystic dilatation of the cisterna magna and fourth ventricle

29. The condition in which there is no nose and a proboscis separating two close-set orbits is: a. Ethmocephaly b. Epignathus c. Micrognathia d. Cebocephaly

a. Ethmocephaly

Anembryonic Gestation (blighted Ovum)

an abnormal pregnancy in which there is no evidence of a fetal pole or yolk sac within the gestational sac.

Pseudogestational Sac

appearance of an abnormally shaped false gestational sac within the uterine cavity as a result of an ectopic pregnancy; this often corresponds w/ the accumulation of blood & secretions within the uterine cavity

12. A cystic hygroma is found in all of the following condition except: a. Edwards syndrome b. Hydranencephaly c. Turner syndrome d. All of the above

b. Hydranencephaly

11. Compared with a normal IUP, the ectopic pregnancy will have a? (Ch.23) a. High hCG b. Low hCG c. Markedly elevated hCG d. High AFP

b. Low hCG

Subchorionic Hemorrhage

bleed between the endometrium and the gestational sac at the edge of the placenta

5. The most common cause of hypertelorism is: a. Dandy-Walker malformation b. Anencephaly c. Anterior cephalocele d. Holoprosencephaly

c. Anterior cephalocele

23. All of the following are sonographic findings consistent with ectopic pregnancy except? (Ch.23) a. Decidual thickening b. Complex free fluid within the pelvis c. Bilateral, multiloculated ovarian cysts d. Complex adnexal mass separate from the ipsilateral ovary

c. Bilateral, multiloculated ovarian cysts

12. The first sonographically identifiable sign of pregnancy is the? (Ch.23) a. Amnion b. Yolk sac c. Decidual reaction d. Chorionic cavity

c. Decidual reaction

3. All of the following are midline brain structures except: a. Interhemispheric fissure b. Cavum septum pellucidum c. Lobes of the thalamus d. Third ventricle

c. Lobes of the thalamus

10. The optimal scan plane to visualize micrognathia is: a. Transverse b. Axial c. Sagittal d. Coronal

c. Sagittal

11. What chromosomal aberration is most often associated with holoprosencephaly? a. Anophthalmia b. Trisomy 21 c. Trisomy 13 d. Trisomy 18

c. Trisomy 13 (Patau Syndrome)

17. A strawberry-shaped skull is commonly associated with: a. Trisomy 21 b. Trisomy 15 c. Trisomy 18 d. Trisomy 13

c. Trisomy 18

Methotrexate

chemotherapy drug used to attack rapidly dividing cells like those seen in an early pregnancy; this drug is often used to manage ectopic pregnancies

Conception

combination of a female ovum with a male sperm to produce a zygote; also referred to as fertilization

Aneuploid

condition of having an abnormal number of chromosomes.

Dandy-Walker malformation

congenital brain malformation in which there is enlargement of the cisterna magna, agenesis of the cerebellar vermis, and dilation of the fourth ventricle

22. All of the following are clinical features of an ectopic pregnancy except? (Ch.23) a. Pain b. Vaginal bleeding c. Shoulder pain d. Adnexal ring

d. Adnexal ring

24. The most common cause of hydrocephalus in utero is: a. Cerebral hemorrhage b. Holoprosencephaly c. Brain tumors d. Aqueductal stenosis

d. Aqueductal stenosis

17. The most common pelvic mass associated with pregnancy is the? (Ch.23) a. Uterine leiomyoma b. Dermoid cyst c. Theca luteum cyst d. Corpus luteum cyst

d. Corpus luteum cyst

27. Elevation of the tentorium and an enlarged cisterna magna that communicates with a dilated fourth ventricle is consistent with: a. Arnold-Chiari II malformation b. Schizencephaly c. Mega cisterna magna d. Dandy-Walker malformation

d. Dandy-Walker malformation

28. Agenesis or hypoplasia of the cerebellar vermis results in what cerebral malformation? a. Arnold-Chiari II malformation b. Schizencephaly c. Mega cisterna magna d. Dandy-Walker malformation

d. Dandy-Walker malformation

30. All of the following may be sonographic findings in the presence of an ectopic pregnancy except? (Ch.23) a. Pseudogestational sac b. Corpus luteum cyst c. Adnexal ring d. Double sac sign

d. Double sac sign

30. Following an intracranial hemorrhage, a cyst is noted within the cerebrum that communicates with the lateral ventricle. This is referred to as: a. Schizencephaly b. Lissencephaly c. Holoprosencephaly d. Porencephaly

d. Porencephaly

28. All of the following are clinical findings consistent with a molar pregnancy except? (Ch.23) a. Vaginal bleeding b. Hypertension c. Uterine enlargement d. Small for dates

d. Small for dates

(Ch. 25) 3. The most frequently encountered chromosomal abnormality associated with holoprosencephaly is: a. Triploidy b. Trisomy 21 c. Trisomy 18 d. Trisomy 13

d. Trisomy 13

14. Micrognathia is a condition found in: a. Trisomy 21 b. Hydranencephaly c. Beckwith-Wiedemann syndrome d. Trisomy 18

d. Trisomy 18

(Ch. 24) 1. The choroid plexus cyst could be associated with an increase risk of: a. Trisomy 13 b. Trisomy 4 c. Arnold-Chiari II malformation d. Trisomy 18

d. Trisomy 18 (Edwards)

hyperemesis gravidarum

excessive vomiting during pregnancy

Chorionic Villi

fingerlike projections of gestational tissue that attach to the decidualized endometrium and allow transfer of nutrients from the mother to the fetus

cyclopia

fusion of the orbits

Amnion

inner sac which contains the embryo & amniotic fluid; echogenic curvilinear structure that may be seen during the first trimester within the gestational sac

Discriminatory zone

level above (level exceeding 1,000-2,000 mIU/mL) which an imaging scan should reliably visualize a gestational sac within the uterus in a normal intrauterine pregnancy

focal myometrial contraction

localized, painless contractions of the myometrium in the gravid uterus that should resolve within 20 to 30 minutes

mean sac diameter

measurement of the gestational sac to obtain a gestational age; achieved by adding the measurements of the length, width, and the height of the gestational sac and dividing by 3

Arachnoid membrane

middle layer of the meninges

hydatidiform mole

most common form of gestational trophoblastic disease in which there is excessive growth of the placenta and high levels of human chorionic gonadotropin; typically benign

alobar holoprosencephaly

most severe form of holoprosencephaly

Mesocephalic

normal head shape microcephaly = small head

monoventricle

one large ventricle within the brain; associated with holoprosencephaly

Chorion

outer membrane of a gestation that surrounds the amnion and developing embryo

Preeclampsia

pregnancy-induced maternal high blood pressure & excess protein in the urine after 20 wks gestation

Brachycephalic

round skull shape

Adnexal Ring Sign

sonographic sign which describes the appearance of an ectopic pregnancy within the fallopian tube

Chorionic Cavity (Extraembryonic Coelom)

space between the chorionic sac and amniotic sac that contains the secondary yolk sac; also referred to as the extraembryonic coelom

Choroid plexus

specialized cells within the ventricular system responsible for cerebrospinal fluid production

secondary yolk sac

structure responsible for early nutrient transfer to the embryo; the yolk sac seen during a sonographic examination of the early gestation

Vitelline duct

structure that connects the developing embryo to the secondary yolk sac

Embryo

term given to the developing fetus before 10 weeks gestation embryonic demise- death of an embryo before 10 weeks gestation

Aqueductal stenosis

the abnormal narrowing of the cerebral aqueduct

intradecidual sign

the appearance of a small gestational sac in the uterine cavity surrounded by the thickened, echogenic endometrium

Zygote

the cell formed by the union of two gametes; the first stage of a fertilized ovum

Double Decidual Sign

the normal sonographic appearance of the decidua capsularis (surrounds ges. sac) and decidua parietalis (lining the uterus) separated by the anechoic fluid-filled in uterine cavity

Rhombencephalon (Hindbrain)

the primary brain vesicle also referred to as the hindbrain; becomes the cerebellum, pons, medulla oblongata, and fourth ventricle

invasive mole

type of gestational trophoblastic disease in which a molar pregnancy invades into the myometrium and may also invade through the uterine wall and into the peritoneum

germinal matrix

- group of thin-walled blood vessels and cells within the subependymal layer of the fetal brain responsible for brain cell migration during fetal development

Beckwith-Wiedemann syndrome

- growth disorder syndrome synonymous w/ enlargement of several organs including the skull, tongue, and liver

NORMAL SONOGRAPHIC FINDINGS DURING THE FIRST TRIMESTER: Gestational Sac (Weeks 4 to 5)

- 1st definitive sonographic sign of an intrauterine pregnancy is identification of the gestational sac within the decidualized endometrium - blastocyst is the developmental stage of the conceptus that implants into the uterine cavity - blastocyst gives rise to the gestational sac, or chorionic sac. - The early gestational sac appears as a small, anechoic sphere within the decidualized endometrium. It will grow at a rate of 1 mm per day in early pregnancy. - intradecidual sign denotes the appearance of the small gestational sac in the uterine cavity surrounded by the thickened, echogenic endometrium. - To differentiate an intrauterine gestational sac from the pseudogestational sac (ectopic preg.), sonographers can assess the endometrium for evidence of the double sac sign or double decidual sign - The double sac sign denotes the typical appearance of the two distinct layers of decidua, the decidua capsularis (inner layer) and decidua parietalis (outer layer), separated by the anechoic fluid-filled uterine cavity - The measurement of the gestational sac is the earliest sonographic measurement that can be obtained to date the pregnancy. - Mean Sac Diameter (MSD) is achieved by adding the measurements of the length, width, and the height of the gestational sac & dividing by 3. - gestational sac meas. is a relatively accurate form of dating that can be used until a fetal pole is sonographically recognized. - When the gestational sac seems visually disproportional to the size of the embryo, that is, too small or too large compared to the size of the embryo, an MSD measurement can be exceedingly beneficial in determining if asymmetry (misshape) truly exists An irregularly shaped gestational sac can be a sign of impending pregnancy failure TABLE 23-2 A List of Various Embryologic Tissues and Their Description Embryologic Tissues: Chorionic cavity The space b/w the gestational sac & the amniotic sac. The location of the secondary yolk sac. Chorion frondosum The decidualized tissue at the implantation site containing the chorionic villi. The fetal contribution of the placenta. Chorion laeve The portion of the chorion that does not contain chorionic villi. Chorionic villi Fingerlike extension of trophoblastic tissue that invades the decidualized endometrium. Decidua basalis The endometrial tissue at the implantation site. The maternal contribution of the placenta. Decidua capsularis The portion of the decidua opposite the uterine cavity, across from the decidua basalis. Decidua parietalis (vera) The decidualized tissue along the uterine cavity adjacent to the decidua basalis.

NORMAL SONOGRAPHIC FINDINGS DURING THE FIRST TRIMESTER: Embryo (5-6 weeks)

- By 6 weeks, the embryo can be seen located within the amniotic cavity adjacent to the yolk sac, w/ transvaginal sonography. - Occasionally, a tiny heartbeat is often seen before an embryo can be measured, w/ sonographic documentation of heart activity being present between 5 & 6 wks. - Heart motion can be detected in a 4-mm embryo, w/ motion certainly evident within the 5-mm embryo. - embryo will grow at a rate of 1 mm per day in the first trimester - Embryonic heart rate is considered normal at 100 to 115 bpm between 5 & 6 menstrual weeks. The heart rate increases to 140 bpm by 9 menstrual weeks. From second trimester to term, the fetal heart rate ranges from 120 to 140 bpm. - Bradycardia is associated w/ a poor prognosis & is often the first sonographic sign of an eminent embryologic demise - Most accurate sonographic measurement of pregnancy is the crown rump length (CRL). measurement can be taken throughout the first trimester, & typically until second-trimester biometric measurements can be obtained.

NORMAL SONOGRAPHIC FINDINGS DURING THE FIRST TRIMESTER: Embryo (7-8 weeks)

- Fetal limb buds are readily identified by 7 wks. - fetal head at this time is proportionally larger than the body. - Within the fetal head, a cystic structure may be noted. This most often represents the rhombencephalon, or hindbrain

Chorionic & Amniotic Cavities (5.5 weeks)

- Gestational sac consists of two cavities: 1) chorionic cavity 2) amniotic cavity - chorionic cavity lies between the amnion & chorion. It contains the yolk sac & fluid. - The amniotic cavity contains simple appearing amniotic fluid & the developing embryo. - amniotic membrane, or amnion, can be seen within the gestational sac as a thin, echogenic line loosely surrounding the embryo * amnion & chorion typically fuse around the middle of the first trimester, but may not be totally fused until 16 weeks gestation.

NORMAL SONOGRAPHIC FINDINGS DURING THE FIRST TRIMESTER: Embryo (9-12 weeks)

- Physiologic bowel herniation begins at 8 weeks, which marks the developmental stage when the midgut migrates into the base of the umbilical cord (Fig. 23-6). This phenomenon is developmentally normal. - if physiologic bowel herniation does not resolve by 12 weeks, a follow-up examination is often warranted. - end of the first trimester, the fetal limbs are much more readily identifiable w/ sonography. - Inside the fetal head, the lateral ventricles may be noted, containing the echogenic choroid plexus - Fetal movement, the stomach, urinary bladder, umbilical cord, & spine can also be noted by the end of the first trimester.

ECTOPIC PREGNANCY

- ectopic pregnancy is the most common cause of pelvic pain w/ a positive pregnancy test. - An ectopic pregnancy is defined as a pregnancy located anywhere other than the endometrial or uterine cavity. - Women w/ a history of assisted reproductive therapy (technology), fallopian tube scarring, and/or pelvic inflammatory disease are among the list of patients who are at high risk - Most common location of an ectopic pregnancy is within the fallopian tube, specifically the ampullary portion of the tube. Other locations for ectopic implantation include the isthmus of the tube, the fimbria, abdomen, cornu of the uterus (interstitial of tube), ovary, and cervix, w/ the least common locations - (rare) patients can have an ectopic pregnancy/intrauterine pregnancy co-existing. This is termed a heterotopic pregnancy. Patients who are undergoing assisted reproductive therapy are at increased risks for heterotopic pregnancies. - classic clinical triad of an ectopic pregnancy includes pain, vaginal bleeding, & a palpable abdominal/pelvic mass - Other clinical findings include amenorrhea, positive pregnancy test, low hCG, shoulder pain (secondary to intraperitoneal hemorrhage w/ diaphragmatic irritation), low hematocrit (with rupture), & cervical tenderness. - Other sonographic findings include the adnexal ring sign, an adnexal mass, a large amount of free fluid within the pelvis & in Morison pouch (with complex free fluid representing hemoperitoneum), a pseudogestational sac, & a poorly decidualized endometrium - interstitial, or cornual pregnancy. This portion of the uterus is highly vascular & is prone to excessive hemorrhage. Interstitial pregnancies are considered potentially life threatening because the pregnancy may progress normally until spontaneous rupture occurs. - Methotrexate(drug) destroys rapidly dividing cells, such as those found in an early pregnancy. This drug works well in most ectopic pregnancies when they are confined to the fallopian tube. - However, when the pregnancy is located within the cornua or cervix, an ultrasound-guided injection of potassium chloride into the embryo or gestational sac can be performed SONOGRAPHIC FINDINGS OF ECTOPIC PREGNANCY: 1. Extrauterine gestational sac containing a yolk sac or embryo 2. Adnexal ring sign 3. Adnexal mass 4. Large amount of free fluid within the pelvis or in Morison pouch (hepatorenal space) 5. Complex free fluid could represent hemoperitoneum 6. Pseudogestational sac 7. Poor decidual reaction 8. Endometrium containing blood

NORMAL SONOGRAPHIC FINDINGS DURING THE FIRST TRIMESTER: Nuchal Translucency (11 - 14 weeks)

- evaluation of the nuchal translucency (NT) has become a vital part of early first-trimester screening. - This translucency is represented by a thin membrane along the posterior aspect of the fetal neck, which can be measured sonographically. - The most common abnormalities associated w/ increased fetal nuchal translucency are trisomy 21, trisomy 18, Turner syndrome, & congestive heart failure. - measurement of this area is performed in the sagittal plane to the fetus, w/ the fetus in a neutral position (Fig. 23-10). - nuchal translucency is optimally measured between 11- 14 weeks gestation, when the crown rump length measures between 45-85 mm * Most often a measurement greater than 3 mm between 11- 14 weeks is considered abnormal & warrants a follow-up examination and fetal karyotyping. TABLE 23-3 Sonographic Guidelines for a Nuchal Translucency Measurement: Guidelines for Nuchal Translucency Measurement : 1. The margins of the NT edges must be clear enough for proper placement of the calipers. 2. The fetus must be in the midsagittal plane. 3. The image must be magnified so that it is filled by the fetal head, neck, & upper thorax. 4. The fetal neck must be in a neutral position, not flexed and not hyperextended. 5. The amnion must be seen as separate from the NT line. 6. The (+) calipers on the ultrasound must be used to perform the NT measurement. 7. Electronic calipers must be placed on the inner borders of the nuchal space with none of the horizontal crossbar itself protruding into the space. 8. The calipers must be placed perpendicular to the long axis of the fetus. 9. The measurement must be obtained at the widest space of the NT.

hydranencephaly

- fatal condition in which the entire cerebrum is replaced by a large sac containing cerebrospinal fluid

NORMAL SONOGRAPHIC FINDINGS DURING THE FIRST TRIMESTER: Secondary Yolk Sac (5.5 weeks)

- first structure seen w/ sonography within the gestational sac is the secondary yolk sac - located within the chorionic cavity, between the amnion & chorion. This cavity may also be referred to as the extraembryonic coelom or extracelomic space. - yolk sac produces alpha-fetoprotein & plays an important role in angiogenesis & hematopoiesis during early embryologic development. - vitelline duct, also referred to as the omphalomesenteric duct, which contains one artery and one vein. - constriction in the yolk sac encloses a small part of yolk sac within the embryo, forming the primitive digestive tube. Connection of the yolk sac to the embryonic digestive system (mindgut) is gradually reduced to a small tube called the vitelline duct * yolk sac can be measured during the first trimester & should be imaged & evaluated for irregular shape, echogenicity, and size.

gyri

- folds in the cerebral cortex

holoprosencephaly

- group of brain abnormalities consisting of varying degrees of fusion of the lateral ventricles, absence of the midline structures, & associated facial anomalies

Arnold-Chiari II malformation

- group of cranial abnormalities associated with spina bifida - condition in which brain tissue extends into the spinal canal, present at birth

GESTATIONAL TROPHOBLASTIC DISEASE (Molar Pregnancy)

- group of disorders that are the result of an abnormal combination of male & female gametes - (Trophoblast) relates to the cells that surround the developing gestation - trophoblastic cells produce hCG. GTD results in the excessive growth of the trophoblastic cells. Therefore, there are excessive amounts of hCG in the maternal circulation. - Clinical findings: of GTD include hyperemesis gravidarum, a markedly elevated hCG level (typically over 100,000 mIU/mL), vaginal bleeding, hypertension, uterine enlargement, & even possible preeclampsia or eclampsia - Sonographic findings of a complete molar pregnancy include a large complex mass within the uterus w/ a "vesicular, snowstorm appearance," containing multiple cystic spaces representing hydropic chorionic villi - The ovarian mass associated w/ a molar pregnancy & elevated hCG is the theca lutein cyst. These masses are typically bilateral & appear as large, multiloculated adnexal masses. - GTD includes hydatidiform mole, invasive mole, & choriocarcinoma. This disease has malignant potential, other imaging modalities & hCG monitoring is typically warranted. The most common sites of metastatic involvement are the lungs, liver, & vagina. However, other organs may be affected. Treatment for GTD includes D&C, hCG monitoring, hys-terectomy, and chemotherapy. CLINICAL FINDINGS OF COMPLETE MOLAR PREGNANCY: 1. Hyperemesis gravidarum (severe type of nausea & vomiting during pregnancy) 2. Markedly elevated hCG level 3. Vaginal bleeding 4. Enlarged uterus 5. Possible preeclampsia or eclampsia 6. Hypertension SONOGRAPHIC FINDINGS OF COMPLETE MOLAR PREGNANCY 1. Large complex mass within the uterus 2. "Vesicular snowstorm appearance" secondary to placental enlargement 3. Multiple, variable-sized cysts replacing the placental tissue (hydropic chorionic villi) 4. Bilateral ovarian theca lutein cysts

NORMAL CONCEPTION & THE FIRST SIX WEEKS (pg. 239)

- mature ovum is released through ovulation (day 14 menstrual cycle), Graafian follicle ruptures/liberates the ovum into the peritoneal cavity - fimbria (fallopian tube) transports ovum into distal portion of the tube called the infundibulum - Conception, also referred to as fertilization (occurs) - sperm, which can live up to 72 hours, unites w/ the egg in the distal one third of the fallopian tube, most likely in the (ampulla) - Conception usually occurs within 24 hrs after ovulation. - combination of the sperm + ovum produces a structure referred to as the (zygote). - zygote undergoes rapid cellular division & eventually forms into a cluster of cells called the (morula). - Morula continues to differentiate & form a structure referred to as the (blastocyst). - Outer tissue layer of the blastocyst is comprised of syncytiotrophoblastic tissue, also referred to as trophoblastic cells. The inner part (blastocyst cavity) of the blastocyst will develop into the embryo, amnion, umbilical cord, & the primary & secondary yolk sacs. The outer part, the trophoblastic tissue, will develop into the placenta and chorion. - (Days 20 or 21) of menstrual cycle, the blastocyst begins to implant into the decidualized endometrium at the level of the uterine fundus. - By (28 days) complete implantation has occurred & all early connections have been established between the gestation & the mother - blastocyst makes these links w/ the maternal endometrium via small projections of tissue called (chorionic villi). The implantation of blastocyst within the endometrium may cause some women to experience a small amount of vaginal bleeding. This is referred to as implantation bleeding. - 4th week of gestation is an extremely dynamic stage in the pregnancy. The primary yolk sac regresses during week 4th & two separate membranes are formed. The outer membrane is the chorionic sac or gestational sac. Within the gestational sac is the amnion or amniotic sac. end of week 4, the secondary yolk sac becomes wedged between these two membranes in an area called the chorionic cavity or extraembryonic coelom. - developing embryo is located b/w the yolk sac & amnion at 4 weeks. At this time, the (alimentary canal) is formed. It will become the foregut, midgut, & hindgut. The neural tube also begins to develop at this time. The neural tube will become the fetal head & spine. - By 5th week, suspicion of pregnancy abounds, as the woman misses scheduled onset of menses for the month. Within the developing gestation, the embryonic heart begins to beat for the first time. - By 6th week, all internal & external structures are in the process of forming.

Arachnoid granulations

- nodular structures located along the falx cerebri that reabsorb cerebrospinal fluid into the venous system

Communicating Hydrocephalus

- obstruction of cerebrospinal fluid from a source outside of the ventricular system

foramen magnum

- opening in the base of the skull through which the spinal cord exits

Cerebral peduncles

- paired structures located anterior to the cerebral aqueduct (aqueduct of sylvius)

MISCARRIAGE AND ABORTION

- several categories of abortions: including threatened, complete, incomplete, missed, inevitable, septic, and elective. - Clinical findings consistent w/ a miscarriage include vaginal bleeding, pelvic cramping, & the passage of the products of conception. - Many miscarriages are idiopathic. However, first-trimester miscarriages have been linked w/ ovarian abnormalities, aneuploid fetuses, maternal infections, physical abuse, trauma, drug abuse, maternal endocrine abnormalities, & anatomic factors - hCG levels are lower than normal w/ miscarriage compared w/ levels in a normal intrauterine pregnancy. Types of Abortion: 1) Threatened abortion - Vaginal bleeding before 20 weeks gestation; closed cervical os Sono: Low fetal heart rate 2) Complete (spontaneous) abortion - All products of conception expelled Sono: No intrauterine products of conception identified Prominent endometrium, which may contain hemorrhage 3) Incomplete abortion - Part of the products of conception expelled Sono: Thickened and irregular endometrium Enlarged uterus 4) Missed abortion - Fetal demise with retained fetus Sono: No detectable fetal heart motion detected. Abnormal fetal shape 5) Inevitable abortion - Vaginal bleeding with dilated cervix Sono: Low-lying gestational sac Open internal os of cervix

dangling choroid sign

- sonographic sign associated w/ hydrocephalus when the choroid plexus is noted hanging freely within the dilated lateral ventricle

Choroid plexus

- specialized cells within the ventricular system responsible for cerebrospinal fluid production

Meninges

- the coverings of the brain and spinal cord

Dura mater

- the dense fibrous outer layer of the meninges

neural plate

- the early embryologic structure that develops into the central nervous system neural tube- embryologic formation that results from fusion of the two folded ends of the neural plate

cisterna magna

- the largest cistern in the skull; located in the posterior portion of the skull

Lobar holoprosencephaly

- the least severe form of the holoprosencephaly

Chorion Frondosum

- the part of the chorion, covered by chorionic villi, that is the fetal contribution of the placenta.

Mesencephalon (Mindbrain)

- the primary brain vesicle also referred to as the midbrain; becomes the cerebral peduncles, quadrigeminal plate, and cerebral aqueduct

Cerebrospinal fluid

- the protective & nourishing fluid of the brain & spinal cord produced by the cells of the choroid plexus