ANA 301 Dura Venous Sinuses, Ventricles & Cisterns

Question 1

What are the Dura venous sinuses?

Answer 1

They are venous channel found between the periosteal and meningeal layers of dura mater in the brain

Question 2

What is the main function of the dura venous sinuses?

Answer 2

Absorb CSF through arachnoid granulations

Receive valveless emissary vein to maintain an equilibrium of venous pressure

Drain the blood from the brain and cranial cavity

Question 3

Characteristics of the sinuses?

Answer 3

Lined by endothelium
Devoid of muscular coat
Devoid of muscular coat

Question 4

The sinuses include

Answer 4

Superior sagittal sinus
Inferior sagittal sinus
Straight sinus
Transverse sinus
Sigmoid sinus
Occipital sinus
Cavernous sinus

Question 5

Features of the Superior sagittal sinus

Answer 5

Occupies the upper fixed border of the falx cerebri
It begins at the crista galli and ends at near the internal occipital protuberance at the confluence of sinuses

Question 6

Communication of the superior sagittal sinus

Answer 6

on each sides of the sinus are 2 – 3 irregularly shaped venous spaces called lacunae
The sinus communicates wit h these spaces through smaller openings
Numerous arachnoid villi / granulations project into the lacunae

Question 7

What are arachnoid granulations?

Answer 7

Arachnoid granulations (collections of arachnoid villi) are prolongations of the arachnoid that protrude through the meningeal layer of the dura mater into the dural venous sinuses, especially the lateral lacunae, and effect transfer of CSF to the venous system
They are usually observed in the vicinity of the superior sagittal, transverse, and some other dural venous sinuses.
Arachnoid granulations are structurally adapted for the transport of CSF from the subarachnoid space to the venous system

Question 8

What are pacchionian bodies and what is their importance?

Answer 8

Enlarged arachnoid granulations (often called pacchionian bodies) may erode bone, forming pits called granular foveolae in the calvaria

Question 9

Characteristics of the Inferior sagittal sinus

Answer 9

occupies the free lower margin of the falx cerebri
It runs backward and joins the great cerebral vein at the free margin of the tentorium cerebelli to form the straight sinus

Question 10

Characteristics of the Straight sinus

Answer 10

is formed by the union of the inferior sagittal sinus with the great cerebral vein
It runs inferoposteriorly along the line of attachment of the cerebral falx to the cerebellar tentorium, where it joins the confluence of sinuses

Question 11

The confluence of sinuses is also known as a the____________

Answer 11

torcular herophili

Question 12

How is the transverse sinus formed?

Answer 12

The straight sinus ends by turning to the left (sometimes to the right) to form the transverse sinus

Question 13

Characteristics of the transverse sinus

Type of structure, what it is continuous with, margin etc

Answer 13

The transverse sinuses are paired structures that begin at the internal occipital protuberance

The right transverse sinus is usually continuous with the superior sagittal sinus, and the left is continuous with the straight sinus

Each sinus occupies the attached margin of the tentorium cerebelli, grooving the occipital bone and the posteroinferior angle of the parietal bone
They end by turning downward as the sigmoid sinuses

Question 14

Why could one transverse sinus be larger than one? What do you call the larger the transverse sinus, which one is larger?

Answer 14

Due to asymmetric drainage of blood
Larger-dominant sinus
Left sinus

Question 15

Characteristics of Sigmoid sinus

Answer 15

It’s a direct continuation of the transverse sinus
follow S-shaped courses in the posterior cranial fossa forming deep grooves in the temporal and occipital bones
Each sigmoid sinus turns anteriorly and then continues inferiorly as the IJV after traversing the jugular foramen

Question 16

Characteristics of Occipital sinus

Answer 16

is a small sinus occupying the attached margin of the falx cerebelli and ends superiorly in the confluence of sinuses
The occipital sinus communicates inferiorly with the internal vertebral venous plexus
Extends from foramen magnum to external occipital protuberance

Question 17

Characteristics of Cavernous sinus

Answer 17

Paired dural venous sinus
situated on either side of the sphenoid bone
Extent: Front - superior orbital fissure
Back: apex of the petrous part of the temporal bone
Interior: transversed by reticular fibres (spongy)
Measurements: L: 2cm B: 1cm
Formation: separation between meningeal and endosteal layer of the dura mater

Question 18

Clinical importance of the cavernous sinus

Answer 18

It is of great clinical importance because of the connection and structures that pass through them

Question 19

The cavernous sinuses receive blood from the

Answer 19

cerebral veins
the superior and inferior ophthalmic veins (from the orbit)
emissary veins (from the pterygoid plexus of veins in the infratemporal fossa)

Question 20

Clinical anatomy of cavernous sinus

What it can lead to

Answer 20

These connections provide pathways for infections to pass from extracranial sites into intracranial locations

In addition, because structures pass through the cavernous sinuses and are located in the walls of these sinuses they are vulnerable to injury due to inflammation

Question 21

Structures passing through each cavernous sinus (from medial to lateral) are:

Answer 21

*Internal carotid artery
- surrounded by sympathetic plexus
- runs along the floor (carotid sulcus)
- turns upward to pierce the roof (carotido-clinoid foramen)

*Abducent nerve [VI]
- enters below petro-sphenoid ligament
- inferolateral to ICA

Question 22

Structures in the lateral wall of each cavernous sinus are, from superior to inferior:

Answer 22

• the oculomotor nerve [III]
•the trochlear nerve [IV]
•the ophthalmic nerve [V1]
•the maxillary nerve [V2]

Question 23

What connects the right and left cavernous sinus?

Answer 23

Connecting the right and left cavernous sinuses are the intercavernous sinuses on the anterior and posterior sides of the pituitary stalk

Question 24

Sphenoparietal sinuses

Answer 24

• drain into the anterior ends of each cavernous sinus
• These small sinuses are along the inferior surface of the lesser wings of the sphenoid and receive blood from the diploic and meningeal veins

Question 25

superior and inferior petrosal sinuses

Answer 25

• are small sinuses situated on the superior and inferior borders of the petrous part of the temporal bone on each side of the skull
• Each superior sinus drains the cavernous sinus into the transverse sinus,
• and each inferior sinus drains the cavernous sinus into the internal jugular vein

Question 26

What are brain ventricles?

Answer 26

Communicating cavities within the CNS that are lined by ependymal cells, which produce, contain, and circulate CF

Question 27

List the ventricles

Answer 27

Two lateral ventricles (right and left)
•3rd ventricle
•4th ventricle

Question 28

The lateral ventricles

Answer 28

*Anterior/ frontal horn
location: frontal lobe
roof: corpus callosum (trunk)
floor: corpus callosum (rostrum)
anterior: corpus callosum (genus)

*a body/ central part, which occupies the parietal lobe

• posterior / occipital horn,
  location: occipital lobe
  roof and lateral wall: tapetum of corpus callosum
  medial wall: calcar alvis ( produced by calcarine sulcus) and bulb of posterior horn (formed by forceps of major)

*inferior /temporal horn
location: temporal lobe
roof: tapetum, tail of caudate nucleus, amygdaloid nucleus, and stria terminalis
floor: hippocampus, fimbria of hippocampus and collateral eminence

Question 29

The 3rd ventricle

Answer 29

Roof: Fornix and tella choroida
Floor: hypothalamus’
Laterally: thalamus and hypothalamus
Posteriorly: opening to the cerebral aqueduct, posterior commissure, pineal recess and habenular commissure
Anteriorly: lamina terminalis

Question 30

The 4th ventricle:

Answer 30

Floor: the posterior surface of the pons and cranial portion of the medulla
Laterally: superior and inferior cerebellar peduncles
Roof: tent-shaped roof projects into cerebellum

Question 31

Clinical anatomy of the ventricles

Answer 31

If they are blocked, CSF accumulates and the ventricles distend, producing compression of the substance of the cerebral hemispheres
Excess fluid in the ventricles lead into the over enlargement of the head to form hydrocephalus
●Note: CSF is produced by the choroid plexus in the ventricular system of the brain
●The main function of the choroid plexus is to remove water from blood and release it as cerebrospinal fluid (CSF)

Question 32

What are Subarachnoid cisterns

Answer 32

•they are expanded areas within the subarachnoid space where the pia mater and arachnoid membrane are not in close approximation
•The cisterns are usually named according to the structures related to them

Question 33

What are the unpaired sinuses

Answer 33

Superior sagittal sinus
Inferior sagittal sinus
Straight sinus
Occipital sinus
Anterior intercavernous sinus
Posterior intercavernous sinus
Basilar venous plexus

Question 33

Classifications of Dura Venous Sinuses

Answer 33

Paired
Unpaired

Question 34

What are the paired sinuses

Answer 34

Transverse sinus
Sigmoid sinus
Cavernous sinus
Superior petrosal sinus
Inferior petrosal sinus
Spheno-parietal sinus
Petro-squamous sinus
Middle meningeal sinus

Question 35

Presenting parts of the cavernous sinus

Answer 35

Roof and lateral wall: meningeal layer
Floor and medial wall: endosteal layer
Structures piercing roof:
- 3rd & 4th cranial nerve
- ICA

Question 36

Relations of the cavernous sinus

Answer 36

Superiorly:
Optic chiasma
ICA

Inferiorly: sphenoidal air sinus
Medially: pituitary gland
Laterally: cavum trigeminale & temporal lobe (uncus)

Question 37

Tributaries of the cavernous sinus

Answer 37

1. Superior ophthalmic vein
2. A branch of the interior ophthalmic vein
3. Central vein of the retina
4. Superficial middle cerebral vein
5. Inferior cerebral vein
6. Sphenoparietal sinus
7. Anterior trunk f middle meningeal sinus

Question 38

Communications of the cavernous sinus

Answer 38

1. With transverse sinus - via superior petrosal sinus
2. With IJV - via inferior petrosal sinus
3. With pterygoid venous plexus - via emissary vein pass through ovale, spinosum, vesalii and lacerum
4. With facial vein by 2 routes:
   - Direct superior ophthalmic vain and angular vein
   - Indirect: with pterygoid plexus via deep facial mean
5. With superior sagittal sinus via superficial middle cerebral and superior anastomotic vein
6. With opposite cavernous sinus via anterior and posterior intercavernous. sinuses

Question 38

Factors regulating blood flowing cavernous sinus

Answer 38

Expansile position of ICA
gravity
change of position of head

Question 39

Foramens of the ventricles include

Answer 39

• The interventricular foramen (Foramen of monro)
• The cerebral aqueduct (Foramen of Sylvius
• The median aperture (also known as the medial aperture and Foramen of Magendie)
• lateral apertures (also called the Foramina of Luschka)

Question 40

The interventricular foramen (Foramen of monro)

Answer 40

The interventricular foramen (Foramen of monro) forms the communicating canal between the lateral ventricle on either side and the third ventricle at the junction of the roof and the anterior wall.

It has a diameter of 3–4 mm, and is bounded anteriorly by the junction of the body and the columns of the fornix and posteriorly by the anterior pole of the thalamus, and has a posterior concavity.

Question 41

The cerebral aqueduct

Answer 41

The cerebral aqueduct is a canal between the third and fourth ventricles was made by Galen.

Question 42

Median and lateral aperture

Answer 42

The median aperture (also known as the medial aperture, and foramen of Magendie) drains cerebrospinal fluid (CSF) from the fourth ventricle into the cisterna magna.

The two other openings of the fourth ventricle are the lateral apertures (also called the foramina of Luschka), one on the left and one on the right, which drain cerebrospinal fluid into the cerebellopontine angle cistern.

The median foramen on axial images is posterior to the pons and anterior to the caudal cerebellum.

Question 43

Functions of CSF

Answer 43

1. cushions and protects the CNS from trauma
2. Provides mechanical buoyancy and support for the brain
3. Serves as a reservoir and assists in the regulation of the contents of the skull
4. Nourishes the CNS
5. Removes metabolites from the CNS
6. Serves as a pathway for the pineal secretion to reach the pituitary gland

Question 44

Factors of CSF flow

Answer 44

1. Pulsation of the cerebral & spinal arteries
2. Movements of the vertebral column
3. Respiration & coughing
4. Changing of the positions

Question 45

What is the BBB

Answer 45

The blood-brain barrier is a selective semi-permeable membrane between the blood and the interstitium of the brain, allowing cerebral blood vessels to regulate molecule and ion movement between the blood and the brain

Question 46

Papilledema

Answer 46

The optic nerves are surrounded by sheaths derived from the pia, arachnoid and dura mater. There is an extension of the intracranial subarachnoid space forward around the optic nerve to the back of the eyeball
A rise in CSF pressure caused by an intracranial tumor will compress the thin walls of the retinal vein as it crosses the extension of the subarachnoid space to enter the optic nerve.
This will result in congestion of the retinal vein, bulging forward of the optic disc, and edema of the disc, the last cndiiton is referred to as papilledema

Question 47

Hydrocephalus and it’s causes

Answer 47

An abnormal increase in the volume of CSF within the skull

Causes can be:
1. Blockage of the circulation of CSF
2. Diminished absorption of CSF
3. Excessive formation of CSF

Question 48

Communicating hydrocephalus

Answer 48

Communicating hydrocephalus, also known as nonobstructive hydrocephalus, is caused by impaired CSF reabsorption in the absence of any obstruction of CSF flow between the ventricles and subarachnoid space.

This may be due to functional impairment of the arachnoidal granulations (also called arachnoid granulations or Pacchioni’s granulations), which are located along the superior sagittal sinus, and is the site of CSF reabsorption back into the venous system.

Question 49

Various neurologic conditions may result in communicating hydrocephalus, including:

Answer 49

subarachnoid/intraventricular hemorrhage, meningitis, and
congenital absence of arachnoid villi.

Scarring and fibrosis of the subarachnoid space following infectious,
inflammatory, or hemorrhagic events can also prevent reabsorption of CSF, causing diffuse ventricular dilatation

Question 50

Non-communicating hydrocephalus

Answer 50

Non-communicating hydrocephalus, or obstructive hydrocephalus, is caused by a CSF-flow obstruction.

Foramen of Monro obstruction may lead to dilation of one, or if large enough (e.g., in colloid cyst), both lateral ventricles.

The aqueduct of Sylvius, normally narrow, may be obstructed by a number of genetic or acquired lesions (e.g., atresia, ependymitis, hemorrhage, or tumor) and lead to dilation of both lateral ventricles, as well as the third ventricle.
Fourth ventricle obstruction leads to dilatation of the aqueduct, as well as the lateral and third ventricles (e.g., Chiari malformation).

The foramina of Luschka and foramen of Magendie may be obstructed due to congenital malformation (e.g., Dandy-Walker malformation).

Question 51

Hydrocephalus treatment

Answer 51

Hydrocephalus treatment is surgical, creating a way for the excess fluid to drain away. In the short term, an external ventricular drain (EVD), also known as an extraventricular drain or ventriculostomy, provides relief. In the long term, some people will need any of various types of cerebral shunt. It involves the placement of a ventricular catheter (a tube made of silastic) into the cerebral ventricles to bypass the flow obstruction/malfunctioning arachnoidal granulations and drain the excess fluid into other body cavities, from where it can be resorbed.
Most shunts drain the fluid into the peritoneal cavity (ventriculoperitoneal shunt), but alternative sites include the right atrium (ventriculoatrial shunt), pleural cavity (ventriculopleural shunt), and gallbladder. A shunt system can also be placed in the lumbar space of the spine and have the CSF redirected to the peritoneal cavity (lumbar-peritoneal shunt).

An alternative treatment for obstructive hydrocephalus in selected people is the endoscopic third ventriculostomy (ETV), whereby a surgically created opening in the floor of the third ventricle allows the CSF to flow directly to the basal cisterns, thereby shortcutting any obstruction, as in aqueductal stenosis. This may or may not be appropriate based on individual anatomy

Question 52

Diseases involving CSF

Answer 52

Meningitis
Blockage of the subarachnoid space in the vertebral canal
Tumors of the fourth ventricle
Kernicterus

Question 53

Meningitis

Answer 53

Meningitis is a serious infection of the meninges, the membranes covering the brain and spinal cord. It is a devastating disease and remains a major public health challenge. The disease can be caused by many different pathogens including bacteria, fungi or viruses, but the highest global burden is seen with bacterial meningitis.

Several different bacteria can cause meningitis.Streptococcus pneumoniae,Haemophilus influenzae,Neisseria meningitidisare the most frequent ones. N. meningitidis, causing meningococcal meningitis, is the one with the potential to produce large epidemics.

Question 53

Kernicterus

Answer 53

Kernicterus isa type of brain damage that can result from high levels of bilirubin in a baby’s blood.

It can cause athetoid cerebral palsy and hearing loss.

Kernicterus also causes problems with vision and teeth and sometimes can cause intellectual disabilities.

Question 53

CHOROID PLEXUS CYST

Answer 53

During fetal development, some choroid plexus cysts may form. These fluid-filled cysts can be detected by a detailed second trimester ultrasound. The finding is relatively common, with a prevalence of ~1%. Choroid plexus cysts are usually an isolated finding (Drugan et al., 2000). The cysts typically disappear later during pregnancy, and are usually harmless. They have no effect on infant and early childhood development (Digiovanni et al., 1997).

Cysts confers a 1% risk of fetal aneuploidy (Peleg et al., 1998).The risk of aneuploidy increases to 10.5-12% if other risk factors or ultrasound findings are noted. Size, location, disappearance or progression, and whether the cysts are found on both sides or not do not affect the risk of aneuploidy. 44-50% of Edwards syndrome (trisomy 18) cases will present with choroid plexus cysts, as well 1.4% of Down syndrome (trisomy 21) cases. ~75% of abnormal karyotypes associated with choroid plexus cysts are trisomy 18, while the remainder are trisomy 21 (Drugan et al., 2000).

Question 54

Layers punctured in a lumbar punture

Answer 54

skin
fat
supraspinous ligament
interspinous ligament
between or through the ligamenta flava
epidural fat and veins
dura
subdural space
arachnoid