Week 5 Flashcards
(11 cards)
What is the sonographic appearance of a cystic hygroma?
Is a congenital lymphatic malformation appearing as a multiloculated, anechoic, cystic mass protruding from the back of the fetal neck. It can have thin septations and is associated with chromosomal abnormalities (Turner, T 13,18,21).
Larger or septated lesions can lead to hydrops. Postnatally can cause breathing and feeding issues depending on size and location and will require surgery.
What factors can compromise the quality of imaging?
Reduced resolution due to maternal habitus
The extensive list of structures that require imaging
The distraction of mother and family who are included as part of the examination and can be difficult
What is ventriculomegaly and hydrocephalus and its sonographic appearance
Ventriculomegaly - General marker of abnormal brain development and can be mild, moderate or overt. It can be isolated but is associated with increased risk of heterogeneous CNS and non-CNS anomalies. Can cause developmental delay and is a marker of aneuploidy. Ventriculomegaly refers to enlarged ventricles >10mm. The head itself may be normal but the ventricles are enlarged.
Hydrocephalus refers to enlarged ventricles associated with increased intracranial pressure/and or head enlargement.
Occurs as a result of CSF obstruction (intraventricular obstructive hydrocephalus). Or the site of the block may be outside the ventricular system or there may be failure of absorption (extraventricular obstructive hydrocephalus or communicating hydrocephalus).
Routine assessment of the fetal head requires a measurement of the lateral ventricles. Describe this measurement in detail and what are the important criteria to predict outcome if the ventricles are dilated
Mild ventriculomegaly is indicative of cases with atrial widths of 10-12 mms. Moderate has a good outcome. Overt is defined based off an atrial width of more than 15 mm in the second or third trimester. Can result from neural tube defects and midline anomalies.
What are some neural tube defects?
Anencephaly
Encephaloceles
Spina bifida
Exencephaly
What is anencephaly, encephaloceles, spina bifida, and acrania?
Acrania - absence of cranial vault, or calvaria
Anencephaly - absence of cranial facial bones/brain tissue/diencephalone structures. Difficult to diagnose as the cranial vault may not have ossified yet. Difficult to diagnose prior to 10 weeks GA.
Encephaloceles - Herniations of intracranial structures through a defect in the cranium. May only contain meninges and CSF (cranial meningocele) or brain tissue (encephalocele). It can be isolated or associated with other anomalies or syndromes involving the head, spine, face, skeleton or kidneys. Looks like a cystic mass at the surface of the skull. Differentials include cystic hygroma, hemangioma, teratoma, branchial cleft cyst and scalp edema.
Exencephaly - Anencephaly where the cranial vault, cerebral hemispheres, and diencephalic structures are gone, the orbits still remain, but the missing structures are replaced by an amorphous vascular neural mass that resemble brain structures uncovered by bone.
Spina Bifida - Spinal lesion (open or closed). Open lesions are most commonly diagnosed and are most common and almost all open lesions have intracranial changes. Closed lesions, no brain abnormalities. The characteristic head changes to open spina bifida include, ventriculomegaly, lemon sign, banana sign, CM effacement, and small BPD and HC.
What needs to be assessed to identify midline anomalies?
CSP, falx, and lateral ventricles.
What are some sonographic features of open spina bifida and what is the crash sign?
The crash sign describes the posterior displacement and deformation of the mesencephalon against the occipital bone due to reduced intracranial pressure caused by CSP fluid leakage.
Lemon sign head (indentation of frontal lobes) due to reduced intracranial pressure
Banana sign cerebellum
Ventriculomegaly due to obstructive hydrocephalus secondary to arnold-chiari malformation
Disruption of normal ossification pattern of spine
Enlarged choroid plexus and dry brain sign due to low surrounding CSP.
Brain Stem thickening and increased BSOBs distance ratio
What do small cystic appearances within the midline most likely represent?
A cavum vergae
Cavum septum interpositum
Herniating third ventricle
Tiny arachnoid cysts
What are the most common substantive midline abnormalities and explain what they are
Agenesis of the corpus callosum
Holoprosencephaly:
Cerebral malformations resulting from incomplete cleavage of the primitive forebrain into two cerebral hemispheres; brain hemispheres don’t separate properly. There can be three different types of these:
Alobar = lacking two hemispheric lobes, no cerebral separation into two hemispheres:
single ventricle
no falx or interhemispheric fissure
thalamic fusion
absent corpus callosum
Semilobar = partial formation of lobes, partial cleavage into hemispheres:
absence of the falx
thalamic fusion
Lobar = two hemispheres are present:
absence of the septum pellucidum
What is the subtype of this abnormality (holoprosencephaly)?
The subtype of this abnormality is known as the middle interhemispheric variant.
