Ventricular System, Vascular System, Hematomas, and Hemorrhages (Stephens)

Question 1

• 4 ventricles (communicating cavities) that are lined w/ ependyma which forms complex vascular folds, choroid plexuses (where CSF is produced)
• locations of ventricles: right and left lateral ventricles in each cerebral hemisphere, 3rd ventricle between the thalami, and 4th ventricle between the cerebellum and pons
• CSF drains toward 4th ventricle into subarachnoid space at or above foramen magnum, mostly at the level of superior sagittal venous sinus

Answer 1

ventricular system

Question 2

• bilateral, C-shaped ventricles in the core of each cerebrum
• lateral wall is corpus callosum, floor is caudate nucleus
• septum pellucidum separates the ventricles midsagittally w/ occasional presence of smal midline cavity (septum cavum)
• anterior horn: center of the frontal lobe; body: center of parietal lobe; posterior horn: center of the occipital lobe; inferior horn: center of the temporal lobe

Answer 2

lateral ventricles

Question 3

What is the clinical relevance of the lateral ventricles and hydrocephaly?

Answer 3

• lateral ventricles frequently enlarged in cases of hydrocephaly
• tube or shunt may be inserted into ventricle to shunt CSF to either venous system or peritoneal cavity
• maintaining patency of these shunts is a chronic neurosurgical problem

Question 4

• located adjacent to midline, below fornix
• connects lateral ventricles and 3rd ventricle
• can be obstructed by tumors (ex: choroid plexus ependymomas in 3rd ventricle)

Answer 4

interventricular foramen of Monroe

Question 5

• thin verticle chamber ventricle in the midline between the thalami
• continuous w/ 2 lateral ventricles via interventricular foramina and 4th ventricle via cerebral aqueduct of Sylvius

Answer 5

third ventricle

Question 6

• narrow canal located in the center of the midrain
• represents the boundary between the tectum and midbrain tegmentum
• drains the third ventricle into the fourth
• midbrain tumors (ex: astrocytomas) may obstruct this area and cause hypertrophy of lateral and third ventricles (supratentorial internal hydrocephalus)

Answer 6

cerebral aqueduct

Question 7

• ventricle shaped like a four-sided pyramid
• base (anterior wall): rhomoid fossa (formed by tegmentum of metencephalon and apex (fastigium) directed towards cerebellum)
• continuous w/: third ventricle via cerebral aqueduct, cerebellomedullary cistern via medial and lateral foramen, and blind-ending central canal at obex

Answer 7

fourth ventricle

Question 8

• space that extends from the obex of the fourth ventricle to spinal cord (C5-8)
• syringomyelia: enlargement of this space which causes it to develop into a cavity (syrinx) in the center of the SC (myelia); sx of bilateral anesthesia of shoulder and upper extremities

Answer 8

central canal

Question 9

• expansions (widenings) of the subarachnoid space that is caused by various recesses on or narrowings of the surface of the brain
• two of the larger of these are cerebellomedullary (cisterna magna, large CSF filled space, superior to foramen magnum and posterior to medulla) and superior (cisterna ambiens, posterior to pineal gland)

Answer 9

subarachnoid cisterns

Question 10

• produces CSF
• convoluted evagination of highly vascular pia mater, surface is covered by single layer of ependymal cells
• located on the floor of the lateral ventricles and roofs of the third and fourth ventricles

Answer 10

choroid plexus

Question 11

What is the general composition of CSF?

Answer 11

(similar to blood ultrafiltrate)

• higher conc of sodium, chloride, and magnesium
• lower conc of potassium, calcium, glucose, and protein
• normally clear and colorless (cloudy or red/orange/yellow colored CSF may indicate infection or subarachnoid hemorrhage)
• specific gravity ~1 allows CNS to float at nearly neutral buoyancy
• presence of more than six lymphocytes or erythrocytes is abnormal

Question 12

What is the normal volume and pressure of CSF?

Answer 12

• pressure: 20-25 ml of CSF in ventricles and 140 ml in system total (600-700 ml prod each day)
• pressure: ranges between 100-200 mm of water

Question 13

• where CSF exits subarachnoid space
• protrude into venous lacunae
• contain pressure-controlled valves that drain most CSF
• CSF resorption is active and passive, involving active transport, colloidal osmotic pressure, and hydrostatic pressure

Answer 13

arachnoid villi

Question 14

What is the relationship of arachnoid villi, hemorrhage, and chemical meningitis?

Answer 14

• hemorrhage can cause arachnoid villi to be temporarily clogged by RBC’s, resulting in hydrocephalus
• after hemorrhage (or neurosurgery) lysis of RBC’s can alter electrolyte composition of CSF, irritating the meninges (chemical meningitis)

Question 15

Describe the generally movement of CSF:

Answer 15

• flows from ventricular system to subarachnoid space
• resorbed into venous system by venous lacunae adjacent to superior sagittal sinus
• flow assisted by movements of vertebral column and pulsations of arteries in subarachnoid space

Question 16

• an increase in cerebral mass and/or size due to presence of excessive amount of CSF in ventricular system, subarachnoid space, or both
• can be compensated for by enlargement of head at cranial sutures in infants/young children, however it leads to increased intracranial pressure in adults
• clinical signs: internal strabismus (abducens palsy, “sundown” eyes) and papilledema
• can result in mental retardation due to damage of cortical matter
• tx: shunt or tube inserted into ventricle or cistern to drain excess CSF

Answer 16

hydrocephaly

Question 17

• excessive accumulation of CSF in subarachnoid space w/ concomitant enlargement of that space by compression of CNS
• can be supratentorial, infratentorial, or both
• supratentorial: most commonly a/w senile atrophy of cortex (e.g. Alzheimer’s)
• infratentorial: seen in combination w/ communicating hydrocephalus

Answer 17

external hydrocephalus

Question 18

• condition where CSF does not drain into subarachnoid space
• may be due to obstruction of interventricular foramen (third ventricle choroid plexus ependymoma), cerebral aqueduct (midbrain astrocytoma), and medial and lateral foramina (Arnold-Chiari malformation, Dandy-Walker cyst)
• results in dilation of ventricles proximal to obstruction
• may be present in combo w/ infratentorial external hydrocephalus (which is communicating hydrocephalus)

Answer 18

internal hydrocephalus

Question 19

• combo of infratentorial external and internal hydrocephalus
• space between tentorial notch and midbrain (only communication for CSF from posterior cranial fossa to supratentorial region) may become obstructed doe to adhesions and fibrosis of subarachnoid spaces from past inflammation (e.g. infantile meningitis), cerebral edema, or uncal herniation
• CSF can move through ventricular system into infratentorial subarachnoid space, but cannot circ over cerebrum to be resorbed at arachnoid villi
• result: hypertropy of ventricles (internal hydro), and accum of CSF in infratentorial subarach space (ext hydro)
• tx: shunt inserted into cerebellomedullary cisten (cisterna magna) to drain excess CSF

Answer 19

communicating hydrocephalus

Question 20

1. Cerebrospinal fluid is produced in the ______
2. Cerebrospinal fluid is resorbed in the ______
3. Atrophy of the cerebral cortex may result in _____
4. Occlusion of the cerebral aqueduct would result in ____ of the _____ and _____
5. Occlusion of the right interventricular foramen would result in the ____ of the ____
6. Obstruction of the subarachnoid space at the level of the tentorial notch may result in _____
7. CSF enters subarachnoid space via the ____ and ____
8. Secondary to a subarachnoid hemorrhage, blood in the CSF may occlude the ____ and result in _____

Answer 20

1. Cerebrospinal fluid is produced in the coroid plexus
2. Cerebrospinal fluid is resorbed in the arachnoid villi
3. Atrophy of the cerebral cortex may result in supratentorial external hydrocephalus
4. Occlusion of the cerebral aqueduct would result in hypertrophy of the lateral and third ventricles

*** 5. Occlusion of the right interventricular foramen would result in the dilation of the right lateral ventricle

6. Obstruction of the subarachnoid space at the level of the tentorial notch may result in communicating hydrocephalus

*** 7. CSF enters subarachnoid space via the ____ and ____

8. Secondary to a subarachnoid hemorrhage, blood in the CSF may occlude the arachnoid villi and result in hydrocephalus