S2) Meningeal Layers, Dural Folds and Dural Venous Sinuses Flashcards Preview

(LUSUMA) Head, Neck & Neuroanatomy > S2) Meningeal Layers, Dural Folds and Dural Venous Sinuses > Flashcards

Flashcards in S2) Meningeal Layers, Dural Folds and Dural Venous Sinuses Deck (24)
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1
Q

There are 3 membranous sacs that surround the brain.

Identify them

A
  • Dura
  • Arachnoid
  • Pia
2
Q

Describe the structure of the three membranous layers around the brain

A
  • Dura: tough fibrous membrane
  • Arachnoid: soft translucent membrane
  • Pia: microscopically thin, delicate closely adherent to surface of brain
3
Q

What additional feature is found between the membranous layers of the brain?

A

Potential spaces:

  • Subarachnoid space – between pia and arachnoid mater
  • Subdural space – between dura and arachnoid mater
4
Q

The dura consists of two layers.

Identify and describe them

A
  • Periosteal: endosteum lining inner bones of skull (cranial floor)
  • Meningeal: layer adjacent to arachnoid
5
Q

The periosteal and meningeal layers are closely adhered but separate in some areas.

What is the result of this?

A
  • Dural folds
  • Dural venous sinuses (spaces which become venous channels)
6
Q

Identify the two dural folds

A
  • Falx cerebri
  • Tentorium cerebelli
7
Q

Describe the structure of the tentorium cerebelli

A
  • Tentorium cerebelli is a strong fold of dura mater roofing over the posterior cranial fossa
  • It has a tentorial notch and is attached at the midline to the falx cerebri
8
Q

Describe the structure and function of the falx cerebri

A

Falx cerebri is a large fold of meningeal layer of dura mater that descends vertically between the cerebral hemispheres

9
Q

Generally, dural folds stabilise the brain.

Explain how these folds can contribute to herniation

A
  • A rise in pressure inside the skull leads to herniation
  • Can be secondary to a bleed, compressing and displacing the brain against rigid dural folds and/or through foramen magnum
10
Q

What are dural venous sinuses?

A

Dural venous sinuses are venous blood filled spaces created by the separation of meningeal from periosteal layer of dura

11
Q

Describe the drainage of blood into dural venous sinuses

A

Venous blood from cerebral veins (in the subarachnoid space) traverses the subarachnoid space and drains into the sinuses

12
Q

Describe the drainage of blood from the dural venous sinuses

A

Dural venous sinuses drain into internal jugular vein (eventually)

13
Q

Describe the location of the dural venous sinuses

A

Major dural venous sinuses lie at the margins of borders of falx cerebri and tentorium cerebelli and on cranial floor

14
Q

Identify the following dural venous sinuses:

  • Superior sagittal sinus
  • Inferior sagittal sinus
  • Transverse sinus
  • Sigmoid sinus
  • Cavernous sinus
A
15
Q

What is an intracranial haemorrhage?

A

An intracranial haemorrhage is bleeding in ‘spaces’ between meningeal layers due to head trauma or the rupture of a blood vessel (aneurysm)

16
Q

Bleeding from blood vessels in the meningeal layers will cause accumulation of blood in which potential spaces?

A
  • Extradural
  • Subdural
  • Subarachnoid
17
Q

Bleeding can also occur within the brain tissue itself.

What is this called?

A

Intracerebral haemorrhage

E.g. contusions, tearing of white matter

18
Q

Why are intracranial haemorrhages so dangerous?

A

Addition of ‘volume’ to an already fixed space (the skull) leads to rise in pressure and damage to brain tissue and other structures e.g. cranial nerves

19
Q

Briefly, what type of bleeding occurs in an extradural haemorrhage?

A

Arterial bleed – middle meningeal artery

20
Q

Briefly, what type of bleeding occurs in a subdural haemorrhage?

A

Venous bleed – bridging veins

21
Q

Briefly, what type of bleeding occurs in a subarachnoid haemorrhage?

A

Arterial bleed – circle of Willis

22
Q

How does a subarachnoid haemorrhage occur?

A
  • Secondary to trauma or spontaneous rupture of blood vessel e.g. aneurysm
  • Blood leaks into subarachnoid space, mixing with CSF
23
Q

What is the common cause of subarachnoid haemorrhages?

A

A branch of ‘Circle of Willis’ ruptures (the arterial circuit responsible for supplying brain structures)

24
Q

Describe the CT imaging of the head for a subarachnoid haemorrhage

A
  • 93% picked up if within 24 hours and 100% if within 6 hours
  • Lumbar puncture if CT inconclusive: sample CSF to identify presence of blood