lecture 10 Flashcards
Ventricle of the Brain and CSF
where do the ventricles stem from?
neuronal canal gives rise to the ventricles of the adult brain
what are the ventricles filled with?
they are filled with CSF
how is the choroid plexus important to the ventricles?
The choroid plexus, which secretes the CSF that fills the ventricles and the subarachnoid space, arises from tufts of cells that appear in the wall of each ventricle during the first trimester.
how does the choroid plexus develop?
○ Arises from tufts of cells that appear in the wall of each ventricle during the first trimester
in the development of the choroid plexus, how does the choroid fissure develop?
Developing arteries in the immediate vicinity invaginate the roof of the ventricle to form a narrow groove
so inside the ventricular space, what represents the primordial choroid plexus, with respect to the development of the choroid plexus?
The involuted ependymal cells and blood vessels
as the development of the choroid plexus develops, what happens to the choroid plexus?
the choroid plexus enlarges → forms villi → secrete CSF
why is the end of first trimester important fo the choroid plexus?
it is functional, openings in the 4th ventricle are patent, CSF is circulating in the ventricular system and subarachnoid space
how is the choroid plexus in each ventricle represented?
into a series of folds called villi
describe the villi of the choroid plexus?
consists of a core of highly vascularized connective tissue derived from the pia mater and a simple cuboidal covering which is derived from ependymal cells.
how common are choroid plexus tumor?
rare, if they occur it will most likely be in the 4th ventricle
how does the shape of the ventricular system conform?
it conforms to the changes in the surrounding part of the brain
lateral ventricles flow the enlarging cerebral hemispheres
the third ventricle remains a single midline space
in the development of the ventricles we have the cerebral aqueduct, how is this formed and why is it important?
Proliferation of the neural elements of the mesencephalon; This creates a constricted region in the ventricular system → flow of CSF may be easily blocked
how does the occlusion of the cerebral aqueduct occur?
Can be a result of gliosis due to infection or developmental defect of the forebrain, rupture of the amniotic sac, or forking of aqueduct
Tumors in the midbrain
what is the pathophysiology in the occlusion of the cerebral aqueduct?
● Results on lack of communication between the 3rd and 4th ventricles and blocks the withdrawal of CSF from the 3rd ventricle
how does the cerebral aqueduct communicate?
Communicates rostrally with the 3rd ventricle and caudally with the 4th ventricle
in the beginning stages of the development of the 4th ventricle, the ventricles and central canal first form a _______?
a closed system
what happens in the 2nd and 3rd months in the development of the 4th ventricle?
three openings form in the roof of the fourth
what does the caudal layer of the roof of the 4th ventricle consist of?
a layer of ependymal cells internally and connective tissue externally
where do small bulges in the caudal roof appear?
at the lateral extremes of the fourth ventricle thinning the membrane and breaking it down → foramen of Magendie (medial) and foramina of Luschka (lateral)
T/F, the development of 4th ventricle have foramen of Luschka (lateral aperture) on either side? T/F, the Foramen of Magendie (median aperture) is located on the midsection ?
T; T
what foramen communicate with CSF? why is this important?
foramen of Luschka and Magendie; Communicating means CSF can go through between the ventricular system = goes into subarachnoid space
where are the lateral ventricles located ?
○ The junction of the body with the posterior and inferior horns constitutes the atrium of the lateral ventricle
what structure is found in the atrium?
the glomus
what could be seen in the CT scan in adults, mostly elderly, of the lateral ventricles?
calcifications
what could we say about the lateral ventricles if glomus changes position and ventricle changes shape/volume?
may be pathologic process or space occupying lesion
what is the floor of the body of the lateral ventricle made of?
made up of the thalamus
what does the lateral wall of the lateral ventricle contain?
the caudate nucleus throughout its extent
what does the medial wall of the lateral ventricle contain?
the hippocampal formation in it
what does the rostral end of the lateral ventricle contain?
have a large group of cells in it (amygdaloid complex)
what cavity is located in the third ventricle?
the cavity of the diencephalon
where is the third ventricle in relation to the diencephalon?
low to the lateral ventricle
describe the space the third ventricle is located within?
narrow, vertically oriented midline space
what does the third ventricle communicate with? what view plane can we see it from?
Communicates rostrally with lateral ventricles and caudally with cerebral aqueduct; sagittal view
how is the rostral wall and floor formed in the third ventricle?
The rostral wall is formed by a short segment of the anterior commissure and lamina terminalis
The floor is formed by the optic chiasm and infundibulum
what recycles unused CSF?
arachnoid granulations in the subarachnoid space
what is hemorrhaging in the ventricles?
blood accumulating in the ventricular spaces in the brain
what causes hemorrhaging in the ventricles?
Rupture of an intracranial aneurysm (especially those located immediately adjacent to the 3rd and 4th ventricles)
severe head trauma
malformation of blood vessels
bleeding of a tumor
what is ependyma?
simple cuboidal epithelium that Line the ventricles of the brain and central canal of the spinal cord
what do ependymal cells contain?
contain abundant mitochondria and are metabolically active.
what percent fo ependymomas constitute of all glial cell neoplasms?
5% - 6%
where are ependymomas located?
60% to 75% are located in the spaces of the posterior fossa, may also be found within the spinal cord or in the region of the cauda equina.
in what age group are ependymomas occur?
most frequently in children younger than 5 years of age.
signs/symptoms of ependymoma? or rather what are the S/S if there are lesions located in the supratentorial? if there are lesions
supratentorial: hydrocephalus or seizure activity
infratentorial: nausea, vomiting, headache, compression of cranial nerves, symptoms related to hydrocephalus
what is hydrocephalus?
Blockage of CSF movement or failure of the absorption mechanism; Increased CSF volume, enlargement of ventricles, increase CSF pressure
where does the blockage usually occur for patients with hydrocephalus?
cerebral aqueduct
what is obstructive hydrocephalus?
Result from an obstruction somewhere within the ventricular system or within the subarachnoid space
what are the two sites hydrocephalus can occur?
intraventricular and extra ventricular sites
intraventricular: interventricular foramen, cerebral aqueduct, caudal portions of the 4th ventricle, foramen of the fourth ventricle (communicating hydrocephalus)
extraventricular: any place in the subarachnoid space (non-communicating hydrocephalus)
what is communicating hydrocephalus?
Flow of CSF in ventricular system and into subarachnoid space is NOT impaired, all parts of the ventricular system are enlarged
in communicating hydrocephalus, what is movement of CSF like in the subarachnoid space into the venous system?
partially or totally blocked
what medical condition can also be a factor in communicating hydrocephalus?
Overproduction of CSF in patients with papilloma of the choroid plexus may also be a factor
what is hydrocephalus ex Vacuo?
○ Not a true hydrocephalus
○ In elderly population (80+)
○ Generalized atrophy of the brain resulting in ventricles that are relatively larger owing to the loss of white matter
○ Brain tissue is shrinking
○ No increase in intracranial pressure
○ No neurologic deficits other than those that may be related to brain atrophy
○ Treatment is not indicated
what is normal pressure hydrocephalus?
○ CSF pressure is elevated episodically when measured over time
○ Effects usually elderly patients (65+)
○ Brain tissue atrophy
○ Diagnostic triad: urinary problems, impaired gait, and dementia
○ Treatment is a shunting procedure to reduce CSF pressure and volume → all of the symptoms lessen
○ Place stunt in lateral ventricles and opens into abdominal cavity and CSF goes into the abdominal cavity
what is the diagnostic triad in normal pressure hydrocephalus?
Patients with normal-pressure hydrocephalus experience a diagnostic triad consisting of urinary problems (frequency, urgency, or incontinence), impaired gait, and dementia
