When does CNS development start?
approximately 5th menstrual week
where does fusion start in the CNS?
Fusion starts in the midtrunk of embryo – extending to the cranial and caudal ends
What thickens to form the brain and spinal cord
walls of neural tube
Walls of neural tube thicken to form the brain and spinal cord
CNS develops from…
CNS develops from thickened area of ectoderm called the neural plate
neural tube is derived from…
the neural plate and is open temporarily at the rostral and caudal ends
__________ END CLOSES, FROM THE THORAX SUPERIORLY AT __________ WEEKS
Cranial end closes , from the thorax superiorly at 5 ½ menstrual weeks
If Cranial end closes , from the thorax superiorly at 5 ½ menstrual weeks…. WHAT CLOSES _____ WEEK LATER?
Cranial end closes , from the thorax superiorly at 5 ½ menstrual weeks
Caudal end closes at ½ week later
what enlarges + flexes and during what week to become the brain?
6th week cephalic end enlarges and flexes to become the brain
cerebral spinal fluid (CSF) is produced by what?
CSF- produced by Choroid plexus
where/what locations is the Cerebral spinal fluid (CSF) located?
Location: Medial walls of lateral ventricles
Roof of the 3rd ventricle
Roof of the 4th ventricle
describe the pathway of cerebral spinal fluid
1) Lateral ventricles –>
through the
2) interventricular foramen of Monroe –>
which goes into
3) Third ventricle –>
and down into
4) aqueduct of Sylvius (cerebral aqueduct) –>
into the
5) Fourth ventricle –>
out through
6)
a - Foramen of Magendie (median aperture)
b - Foramina of Luschka (lateral apertures) –>
into the
7) Subarachnoid space
what is the function of CNS
CSF
–> found in the brain and spine
–> acts as a cushion/buffer for brain’s cortex, providing a basic mechanical & immunological protection to the brain inside the skull
–>and serves a vital function in cerebral autoregulation of cerebral blood flow.
–> occupies the
1) subarachnoid space (the space between the arachnoid mater and the pia mater)
2) and the ventricular system around and inside the brain and spinal cord.
It constitutes the content of the ventricles, cisterns, and sulci of the brain, as well as the central canal of the spinal cord
what happens to the fetal head at the end of the first trimester
- Cranial bones begin to ossify
- Choroid plexus fill the lateral ventricles almost entirely
what occurs in weeks 13-15
Anterior horns of the lateral ventricles are now devoid of choroid plexus
Anterior horns may appear prominent simulating ventriculomegaly
Corpus callosum begins development at 12 weeks and is complete by 18 to 20 weeks
Before 18 to 22 weeks the cerebellum, cerebellar vermis & cisterna magna are difficult to recognize
in what weeks does the
Anterior horns of the lateral ventricles are now devoid of choroid plexus
Anterior horns may appear prominent simulating ventriculomegaly
weeks 13-15
when does the corpus callous begin to develop and when is finished developing?
begins development: week 12
complete: 18 to 20 weeks
Before ___________ the cerebellum, cerebellar vermis & cisterna magna are difficult to recognize
18 to 22 weeks
what is important to note for each level of the normal ventricles and intracranial anatomy on the transverse view (levels 1 through 4)
1: At this level the periventricular lines image within the cerebrum
2: The choroid plexus images within the ventricles
3: The BPD and HC measurement level
4: Level for measurement of the cerebellum, cistern magna, and nuchal fold
2–4: Recommended as part of a routine obstetric examination in the second and third trimester
ACP = choroid plexus
CSP = cavum septum pellucidum
FH = frontal horn
LV = lateral ventricle
MB = midbrain
OH = occipital horns
Th = thalamus
TV = third ventricle
What are the standard transracial views in 2nd and 3rd trimester
1.Ventricular view - Higher level than the thalamic view - atrial measurement here.
- Thalamic view - BPD, OFD & HC level
- Cerebellar view
Pia/arachnoid mater covering cerebral sulci appears echogenic at ___________. ______ not visualized prior to this.
25 to 26 weeks
Sulci
Periventricular lines
what is it?
location?
represents?
Periventricular lines (bilateral echogenic areas)
Location: in the cerebrum & run parallel to the falx cerebri at the superior level.
Represent: blood vessels superior to the lateral ventricles
a normal measurement of the lateral ventricle should not exceed…
10 mm
At how many weeks: the atrial size remains unchanged This is the ventricular point of measurement for Ventriculogmegaly
13 to 40
what is the ventricular point of measurement for Ventriculogmegaly
13 to 40 weeks
