Meningeal Layers, Dural Folds and Dural Venous Sinuses Flashcards
What are the layers of the meninges?
From outermost to innermost
DAP
Dura mater
Arachnoid mater
Pia mater
What are the bumps in the brain called?
Gyri
What are the dips in the brain called?
Sulci
What are the fissures of the brain?
Longitudinal
Lateral x2
Describe the Pia mater
Microscopically thin
Delicate adherence to surface of brain
Follows every sulci + fissure
Describe the arachnoid mater
Soft fibrous translucent membrane
Doesn’t descend into sulci or lateral fissures
Does descent longitudinal fissure
What are the leptomeninges?
Pia and arachnoid mater
What does an infection in the leptomeninges cause?
Meningitis
Describe the dura mater
- Tough fibrous membrane
- Has two layers while in the skull: periosteal + meningeal
- Separation of the layers forms: dural folds + dural venous sinuses
What is the subarachnoid space?
The space between the Pia + arachnoid mater
What does the subarachnoid space contain?
CSF
Cerebral arteries + veins
What are the two layers of the dura while in the skull?
- periosteal: part against inner table of bone (periosteum)
- meningeal: part adjacent to arachnoid
What forms when the two layers of the dura separate?
Dural folds
Dural venous sinuses
What is the dural fold in the longitudinal fissure called?
Falx cerebri
What is the dural fold in the lateral fissure called?
Tentorium cerebelli
Function of dural folds
- Act as rigid dividers
- Help to stabilise the brain: falx cerebri <> | tentorium cerebelli ^v
What can a rise in intracranial pressure cause?
Compression + displacement of parts of the brain against dural folds and/or through the foramen magnum
What are dural venous sinuses?
Venous blood filled spaces created by separation of meningeal + periosteal layer of dura
Where do dural venous sinuses drain into?
Internal jugular vein
What dural venous sinuses are at the superior and inferior margins of falx cerebri?
Superior Sagittal sinus
Inferior Sagittal sinus
What connects the cavernous sinus to the sigmoid sinus?
Superior + inferior petrosal sinuses
What meets at the confluence of sinuses?
- Superior sagittal sinus
- Straight sinus (drains inferior sagittal sinus)
- Occipital sinus
- Transverse sinus x2
Outline the route of venous blood from the confluence of sinuses to the cavernous sinus
- confluence of sinuses
- transverse sinus
- sigmoid sinus
- superior + inferior petrosal sinus
- cavernous sinus
What connects the inferior Sagittal sinus to the superior sagittal singus?
ISS > straight sinus which meets the SSS at the confluence of sinuses
How do cerebral veins drain into dural sinuses?
Bridging veins
How do scalp (extracranial) veins drain into the dural venous sinuses?
Emissary veins
Link to test sinuses
https://sketchfab.com/3d-models/dural-venous-sinuses-deep-veins-c044a5d3e3374ce2b208ccf590ef3473
What are the types of intracranial haemorrhage?
Extradural/epidural
Subdural
Subarachnoid
What is an intracranial haemorrhage?
Head trauma can lead to bleeding in potential spaces between meningeal layers
What is an intracerebral haemorrhage?
Bleeding occurs within the brain tissue itself
What is a characteristic shape of an extra dural haemorrhage on a CT scan?
Biconvex shape with edges limited by bond to sutures
Where does an extradural haemorrhage occur between?
Inner table of bone + periosteum
How does fresh blood appear on a CT?
Bright white
What is a characteristic history for a patient with an extradural haemorrhage?
- trauma to side of head
- loss of consciousness
- normal after regaining consciousness
- deterioration ~1 hours later
Is the deterioration more rapid in a extradural or subdural haemorrhage and why?
Extradural haemorrhage
Bleed of arterial blood compared to venous blood
What causes a subdural haemorrhage?
Venous bleed usually form bridging veins
What is the weakest point in a bridging vein?
The point of connection with the dural venous sinus
What is the characteristic shape of an subdural haemorrhage on a CT?
Crescent shape
Not defined edges
Causes of a subarachnoid haemorrhage
Secondary to trauma
Spontaneous rupture of blood vessel
e.g. aneurysm
Why is the circle of Willis a place where spontaneous rupture of blood vessels could occur?
Area of anastomoses
Aneurysms can occur
How do you identify a subarachnoid haemorrhage?
- patient complains of thunderclap headache
- CT image
- lumbar puncture if CT if inconclusive: sample CSF to identify presence of blood (haemoglobin degradation products)
From the superior sagittal sinus, what is the route that venous blood takes as it leaves the cranial cavity?
Superior sagittal sinus
Confluence of sinuses
Transverse sinus
Sigmoid sinus
Internal jugular vein
Connections of the falx cerebri
- superior: top of skull
- inferior: corpus collosum
- anterior: anterior skull
- posterior: posterior skull
What is a characteristic history for a patient with an extradural haemorrhage?
Older patients
Alcoholics
On anticoagulants
Bump to head
Gradual decline
A patient complains of the worst headache of their life, what is the most likely diagnosis?
Subarachnoid haemorrhage
What layers is a subdural haemorrhage between?
Dura mater + Arachnoid mater
What layers is a subarachnoid haemorrhage between?
Arachnoid mater + pia mater
