Meninges And Dural Venous Sinuses

Question 1

What are the meninges?

Answer 1

3 membranous layers surrounding the brain and spinal cord

Question 2

What are the 3 layers of the meninges (Innermost to outermost)

Answer 2

• Pia Mater: Firmly attached to surface of brain
• Arachnoid Mater: Delicate avascular middle layer
• Dura Mater: Tough outer layer, made up of 2 layers

Question 3

What are the bumps and dips of the brain called? Which meningeal layer follows these contours?

Answer 3

Bumps- Gyri
Dips- Sulci

Pia Mater

Question 4

Describe the arachnoid mater’s relationship to Pia Mater

Answer 4

• Superficial to Pia Mater

- Trabeculae extend downward from its inner surface and become continuous with Pia Mater

Question 5

What is the region between the Arachnoid and Pia mater?

What is it full of?

Answer 5

Sub-arachnoid space

Full of CSF, veinous and arterial blood vessels

Question 6

What does the term Leptomeninges mean?

Answer 6

Combined term for Pia and Arachnoid mater

Question 7

The Dura Mater consists of 2 layers.

Compare them

Answer 7

Outer Periosteal;

• Firmly attached to skull
• Contains meningeal arteries
• Continuous with periosteum on outer surface of skull
• Not continuous with spinal dura matter through Foramen magnum

Inner Meningeal;
- Continuous with spinal dura mater through foramen magnum

Question 8

Describe the relationship between the Inner Dural layer and Arachnoid Mater

What is the clinical significance of this?

Answer 8

Arachnoid Mater pushed up against Inner Meningeal Layer by CSF

Forms the Subdural space (a potential space)

Question 9

What does the Arachnoid Mater look like

Answer 9

Translucent

Question 10

What are 2 types of locations where the 2 layers of the dura mater separate from each other?

Answer 10

• Dural venous sinuses (blood between 2 layers)

- Dural partitions/ folds, which project inwards and incompletely separate parts of brain

Question 11

What is the Extradural space?

Answer 11

A potential space between dura mater and bone

Can fill with blood from a meningeal artery rupture or torn Dural venous sinus

Question 12

Name 4 Dural Folds

Answer 12

• Falx Cerebri (Vertical)
• Tentorum Cerebelli (Horizontal)
• Falx Cerebelli
• Diaphrgam Sellae

Question 13

What is the Falx Cerebri?

Answer 13

• A crescent shaped downward projection of meningeal dura mater, that separates the left and right hemisphere

Question 14

Name the attachments of the Falx Cerebri

Answer 14

Anterior: Crista Galli of ethmoid bone (and frontal crest of frontal bone)

Posterior: Blends with Tentorum Cerebelli

Question 15

What is the Tentorum Cerebelli?

Answer 15

• A horizontal projection of meningeal dura mater, that separates the Cerebellum from the posterior parts of the cerebral hemispheres

Question 16

What are the attachments of the Tentorum Cerebelli?

Answer 16

Posteriorly: Occipital bone along grooves of Transverse Sinuses

Laterally: Superior border of Petrous part of Temporal bone

Question 17

Describe the Anterior and Medial borders of Tentorum Cerebelli

Answer 17

Are free, forming an oval opening in the midline (The Tentorial Notch), through which midbrain passes

Question 18

What do the Dural Folds do? (In general)

Answer 18

• Help to stabilise brain and act as rigid dividers

Question 19

Considering the Dural Folds, what can happen when intra-cranial pressure rises?

(Such as due to a bleed)

Answer 19

Can lead to compression/ herniation of parts of brain against the Dural Folds or Through Foramen Magnum

(Can lead to mental consequences)

Question 20

What connects the back of the Inferior Saggital Sinus to the Superior Saggital Sinus before it branches off into Transverse sinuses?

Answer 20

Straight Sinuses

Question 21

What is the Inferior Petrosal Sinus?

Answer 21

Connects posterior Cavernous Sinus to Sigmoid Sinus, just before SS leaves skull base

Question 22

What is the Superior Petrosal Sinus?

Answer 22

Connection between posterior Cavernous Sinus and Transverse Sinus, just before TS becomes Sigmoid Sinus

Question 23

What are Bridging and Emissary Veins

Answer 23

Bridging: Connect Dural Veinous Sinuses to Cerebral Veins

Emissary: Connect Dural Veinous Sinuses to Scalp Veins (This is how scale infections can enter skull)

Question 24

What are the 3 spaces between the meningeal layers where blood can accumulate

Where else can bleeding occur?
How?

Answer 24

• Extradural (Bone and Dura)
• Subdural (Dura and Arachnoid)
• Subarachnoid (Arachnoid and Pia)
• Within the brain tissue itself (Intra-cerebral haemorrhage)
• Contusions, tearing of white matter etc.

Question 25

What can increased intracranial pressure due to haemorrhage cause?

Answer 25

• Brain tissue damage/ compression
• Brainstem displacement/ damage
• Cranial nerve compression/ damage/ irritation

Question 26

Which artery runs between Periosteal Dura and Inner Table of bone?

Why is its anterior branch particularly susceptible to damage/ rupture in trauma?

Answer 26

Middle Meningeal Artery

Runs underneath Pterion (Thinnest part of calvaria)

Question 27

How does Extradural haemorrhage affect Periosteal dura mater?

Answer 27

Causes it to tear off of Periosteum

Question 28

How does an Extradural Haemorrhage present on a CT scan?

Why is it this colour?

Answer 28

• Bright white lentiform/ Biconvex shape
• Fresh blood looks bright white on CT

(Shape is because lateral filling of blood is limited)

Question 29

How does an Extradural Haemorrhage patient usually present?

Answer 29

• Significant head trauma-> Loss of consciousness
• Appear normal when they come around
• Significant rapid neurological deterioration after a brief period (an hour or so)

Question 30

What is a Lucid Interval? (Occurs in Extradural haemorrhage)

Answer 30

Period between loss of consciousness and rapid neurological deterioration, where patient seems normal

Question 31

What type of blood usually causes a Subdural Haemorrhage?

Answer 31

Veinous blood from Bridging Vein

Question 32

Subdural haemorrhages can happen via significant trauma OR minor head injury, particularly in older patients.

Why is this?

Answer 32

As we age our brain shrinks slightly, putting more tension on the Bridging Veins, increasing the risk of them rupturing/ tearing/ being damaged

Question 33

How does a Subdural haemorrhage appear on a CT?

Why does it have this shape?

Answer 33

• Bright white, crescent shape

- The bleed can fill subdural space of entire hemisphere on which it occurs

Question 34

How does a Subdural Haemorrhage patient present?

Answer 34

• Initially normal, may have headache

- Gradually deterioration of Neurological condition (As it is a Veinous bleed not arterial bleed)

Question 35

What important arteries are in the Subarchnoid Space?

Answer 35

Cerebral arteries, forming the Circle of Willis

Usually an arterial bleed

Question 36

What are 2 causes of Subarachnoid Haemorrhage?

Answer 36

• Usually due to trauma

- Spontaneous blood vessel rupture (Aneurysms, can form at Circle of Willis)

Question 37

In a Subarachnoid Haemorrhage, why do we get sudden, severe headaches?

Why can we use a Lumbar Puncture to diagnose this?

Answer 37

• Blood is highly irritant to meninges, therefore headache

- Blood enters subarachnoid space and mixes with CSF

Question 38

Subarachnoid haemorrhages are often fatal.

What are the chances of survival if picked up by CT within 24 hours?

What about within 6 hours?

What if CT is inconclusive?

Answer 38

• <24hrs: 93%
• <6hrs: 100%

Do a Lumbar puncture and look for Hb degradation products

Question 39

How does a Subarachnoid Haemorrhage appear on a CT?

Answer 39

• Bright white shape around base of brain, where aneurysms are known to occur (Circle of Willis)