Meninges and Dural Folds

Question 1

What are the 3 memranous layers that surround and protect the brain and spinal cord?

Answer 1

1. Pia mater- most internal. Enters all folds and dips of brain
2. Arachnoid mater- middle layer. Doesn’t enter sulcae but enters large fissures
3. Dura mater- most external. Doesn’t enter any dips or folds

Question 2

What is found in the subarachnoid space?

Answer 2

CSF & blood vessels

Question 3

What is the subdural space

Answer 3

A potential space underneath the dura, between the arachnoid mater

The CSF usually keeps the 2 layers tightly together so no space

Question 4

Describe how the 3 membranous layers surrouning the brain and spinal cord appear

Answer 4

1. Dura- tough, firbrous connective tissue
2. Acrachnoid- soft and translucent membrane
3. Pia- microscopically thin

Question 5

What are the 2 different layers of dura and how do they appear throughout the brain and spinal cord

Answer 5

1. Periosteal- against inner table of bone
2. Meningeal- adjacent to arachnoid

Appear as a single layer for most part but can separate into 2 layers at…

• dural folds
• dural venous sinuses

Question 6

Explain how dural folds and dural venous sinuses form

Answer 6

At certain points the meningeal layer can ‘peel away’ from the periosteal layer

Where the 2 meningeal layers meet again, this is a dural fold

The space created between the meningeal and periosteal layers is the dural venous sinus (a space filled with venous blood)

Question 7

What is a cavernous sinus?

Answer 7

Dural venous sinus located either side of the sella turcica of the sphenoid bone

Full of venous blood, separated by fibrous tissue

Question 8

Name the 2 most significant folds of meningeal dural mater and explain their location

Answer 8

• Falx Cerebri - longitundinal midline dural fold, separates hemispheres of brain
• Tentorium Cerebelli - horizontal plane

Question 9

What are the superior and inferior saggital sinuses?

Answer 9

Superior sinus: a dural venous sinus formed by the falx cerebri

Inferior sinus: a dural venous sinus formed by the posterior part of the falx cerebri

Question 10

What is the function of dural folds in the brain?

Answer 10

Help stabilise the brain and act as rigid dividers

Question 11

How can dural folds be problematic if there is a pressure increase in the skull?

Answer 11

The high pressure can cause parts of the brain under to compress and herniate under the dural folds or through the foramen magnum

Question 12

How are Dural Venous Sinuses connected to each other?

Answer 12

Dural Venous Sinuses connect to each other and recieve blood from cerebral veins

They eventually drain into internal jugular vein

Question 13

What are bridging veins?

Answer 13

Veins that transverse subdural space to connect dural venous sinuses

Question 14

What are emissary veins?

Answer 14

Veins that drain the scalp through the skull, into the dural venous sinuses

(extracranial →intracranial)

Question 15

In what area would an extradural haemorrhage occur?

What characteristic shape does this have on CT and why?

Answer 15

Bleeding in betwen the inner table of bone and the periosteal dura

Distinctive wedge appearance as bleeding strips the periostium off the bone until the area where sutres are reached

Question 16

Where does a subdural haemorrhage occur and which venous structures usually cause the bleed?

Answer 16

Bleeding between the dura mater and the arachnoid mater

Bleeding usually from bridging beins

Question 17

How does a subdural Haemorrhage appear on CT scan?

Answer 17

Banana shaped

Question 18

How does subarachnoid haemorrhage usually occur?

Answer 18

• secondary to trauma
• spontaneous rupture of a blood vessel (aneurysn)

Question 19

Why do patients complain of meningitis like symptoms in a subarachnoid haemorrhage?

Answer 19

• Blood in subarachnoid space mixes with CSF
• Blood irritates surfaces of brain causing headache, photophobia and neck stiffness