Meninges and dural folds

Question 1

What is the meninges?

Answer 1

Three membranous layers that surround and protect the brain and spinal cord

Question 2

What are the 3 layers of the meninges?

Answer 2

pia mater - covers the whole CNS (every fissure and sulcus) and brain steam
arachnoid mater - loose connective tissue just surround fissures
dura mater - outer most layer

Question 3

What is between pia mater and arachnoid layer?

Answer 3

subarachnoid space containing blood vessels and CSF

Question 4

What are the leptomeninges?

Answer 4

pia and arachnoid layers collectively

Question 5

What is between arachnoid layer and dura mater?

Answer 5

potential space called the subdural space HOWEVER< normally the pressure of the CSF in the subarachnoid space pushes the arachnoid layer to the dura mater

Question 6

What is the dura mater?

Answer 6

tough fibrous membrane - fuses with the periosteum lining inner table of skull bones

Question 7

What is special about the arachnoid layer?

Answer 7

it is soft and translucent

Question 8

What are the 2 layers of dura?

Answer 8

periosteal and meningeal

Question 9

What is the periosteal layer of dura?

Answer 9

the part against the inner table of bone

Question 10

What is the meningeal layer?

Answer 10

the part adjacent to the arachnoid

Question 11

Where do these 2 layers separate?

Answer 11

They are normally closely adhered, but they separate where there are dural fold and dural venous sinuses

Question 12

What is a dural fold?

Answer 12

• Meningeal dura form it as a fold coming toward the midline - it runs in between fissures on the cranial vault e.g.
  Falx cerebri : (longitudinal fissure) seperates both cerebral hemispheres
  Tentorium cerebelli : (lateral fissure) seperetes occipital from cerebellum

Question 13

What is a dural venous sinus?

Answer 13

Meningeal dura separates from periosteal layer and a plexus of veins are found there
- they are connected to eacother and receive blood from cerebral veins

Question 14

What is the clinical significance of dural folds?

Answer 14

they are very rigid and help stabilise the brain acting as rigid dividers
- a rise in intracranial pressure secondary to bleed etc can lead to compression and herniation of parts of brain under the dural folds or through the foramen magnum

Question 15

Where do dural venous sinuses ultimately drain into?

Answer 15

IJV as soon as they pass through the jugular foramen

Question 16

What do bridging veins do?

Answer 16

connect cerebral veins in the subarachnoid space to the dural venous sinus

Question 17

What do emissary veins do?

Answer 17

connect scalp veins in the dense connective tissue to the dural venous sinuses

Question 18

What is the difference in their paths through the head and brain?

Answer 18

Bridging veins traverse the subdural space but emissary veins travers through the skull

Question 19

What can head traumas lead to?

Answer 19

intracranial haemorrhage - blood vessels run along in-between the meningeal layers

Question 20

What can head traumas lead to?

Answer 20

intracranial haemorrhage - blood vessels run along in-between the meningeal layers

Question 21

Where can you get haemorrhaging?

Answer 21

in the spaces between the meningeal layers;
Extradural
subdural
subarachnoid
intracerebral

Question 22

What is an extradural haemotoma caused by?

Answer 22

• MMA bleed (arterial)
• lucid interval - unconscious then ok then deteriorate
• often secondary to trauma to side of head (pterion)
• doesn’t cross suture lines as the periosteal dural is stripped off the inner bone - the dura is strongly adhered to the suture lines
• get a biconvex shape on CT scan

Question 23

What is a subdural haemotoma caused by?

Answer 23

• bridging veins bleed (venous)
• looks like a banana on CT scan
• mainly elderly (brain shrinks causing bridging veins to be stretched making them easier to snap cortical atrophy
• mild injury - later onset of symptoms as blood has time to pool (in dural venous sinuses)

Question 24

What is a subarachnoid haematoma caused by?

Answer 24

• secondary to trauma or spontaneous rupture of blood vessel (anurysm) - usually branch of circle of willis
• severe sudden onset headache
• blood leaks into suparachnoid space and mixes with CSF
• need to perform lumbar puncture for confirmation

Question 25

Why can meningitis and subarachnoid haematoma have similar symptoms?

Answer 25

The blood becomes an irritant to the meninges - wouldn’t get the other symptoms of infection though with a sub arachnoid haematoma