Meningeal Layers, Dural Folds and Dural Venous Sinuses Flashcards
what r cranial meninges? functions
-
membranous coverings of the brain that lie immediately internal to the cranium
Protect the brain.
Form the supporting framework for arteries, veins, and venous sinuses.
Enclose a fluid-filled cavity, the subarachnoid space, which is vital to the normal function of the brain.
describe the layout of the cranial meninges
pia: highly vascular (chna plstic wrap around brain) protects brain from bacteria and pathogens
subarachnoid space> CSF
Arachnoid matter: non vascular (spiders web) stuck to pia, has arahnoid villi, which drains CSF from subarachnoid space into venous sinus
subdural space!
Dura:
- -periostal (stuck to inner surface of skull itself!) dense, collagen fibers!
- -meningeal stuck to periostial BUTTTTT it seperates at a point from the peristal dura! creating a space!
where the 2 layers of the dura seperate!>> the space becomes occupied w, dural venous sinuses!
name layer in order, from out to in
location of CSF and blood vessels between these layers.
Describe the reflections of the dura mater and the formation of the venous sinuses,
including their connection with the internal jugular vein and cerebral veins.
the meningeal layer strips of the periostal layer
by this “stripping”, the venous sinus is formed btw the 2 dura layers!
cool fact, with age, the arachnoid villi grows across the sinus and protrude pits in the iner table of the skull base “granular fovea”
Describe the dural folds and how theyre formed, function
the meningeal layer strips of the periostal layer to form dural infoldings
divide the cranial cavity into compartments
- Falx cerebri : seperates both cerebral hemispheres
- Tentorium cerebelli : speretes occipital from cerebellum
- Falx cerebelli : seperetes both hemispheres of cerebellum
- Diaphragma sellae (sellar diaphragm).
clincinal relevance of dural folds
the r extremely rigid,
A rise in pressure inside the skull can lead to to portions of the brain to herniate beaneath their edges!
what r dural venous sinuses? where do they attach? include their path starting from IJV
Venous blood filled spaces created by separation of meningeal from periosteal layer of dura.
They r attached to the free margins of the dural folds.
The falx cerebri has a dural venous sinus on both edges
the larger venous sinuses r attched to the inside of the cranial bone.
what r feautures of the dural sinuses? and their clinical relevance
they collect blood from which structres?
- wall lacks muscle>> prevents it from contracting when injured> life threatening bleed!
- no valves> direction of blood flow depends on ur position not on valves
brain, calvaria, orbital cavity
what r emissiary veins? clinical relevance?
valvuless veins that make connections among the sinuses, diploic vein, and extracranial veins of scalp.
create a route by which bacteria fromt he scalp can spread to the dura matter & dural venous sinuses
Intracranial Haemorrhage types
bleeding btw calvaria and brain
- epidural hemmorhage
- subdural hemmorhage
- subarachnoud hemmorhage
subdural Haemorrhage
- causes
- structure ruptured
- common location in brain
- age group & why
- patient presentation
- CT features
- complication
- prognosis
subdural
caused by rupture of bridging vein,
(banana shape)
because bleeding source is venous, raised intracranial pressure & mass effect develop more SLOWLY & a subdural hematoma may develop in a weeks
subarachnoid hemmorhage
- causes
- structure ruptured
- common location in brain
- age group & why
- patient presentation
- CT features
- complication
- prognosis
Secondary to trauma or spontaneous rupture of blood vessel e.g. aneurysm
– Usually a branch of ‘Circle of Willis’
usually caused by a sudden ride in bp!
bc the hemmorage is into CSF fluid, blood can be detected in a lumbar puncture!
symptoms: sudden, excruiciating headache accompanied by a stiff neck.
Epidural/extradural hematoma
- causes
- structure ruptured
- common location in brain
- age group & why
- patient presentation
- CT features
- complication
- prognosis
epi-dural (above dura)
middle meningeal A.
egg shaped
Symptoms: transient loss of conciousness, follwed by 1-5 hrs later by a 2nd decline of conciousness. called the “lucid interval”
what is the lucid interval?
the interval between the injury and the appearance of symptoms in a epidural hemmorage.
This is why patients with head injuries are often admitted to hospital for a brief period.
what is a Berry Aneurysm?
- sites of formation
- risk factors
- Largely asymptomatic but symptoms may arise if compressing on nearby structures or during early stages of rupture
- Around 3% of population may have one or more aneurysm (We dont know those who have got a berry anuerysm)
- Surgical clipping and endovascular coiling can be performed if risk of rupture is high
Risk Factors:
- Family history
- Hypertension
- Heavy alcohol consumption Abnormal connective tissue
- Autosomal Dominant Polycystic Kidney Disease, Ehlers-Danlos, Neurofibromatosis, Marfan’s Disease
Explain why bleeding can be profuse and difficult to stop from an incised scalp
wound involving the dense connective tissue layer
The blood vessels to the scalp are adhered to dense connective tissue, preventing the vasoconstriction that normally occurs in response to damage. The blood supply to the scalp is made up of many anastomoses, which contribute to profuse bleeding.
Following some head injuries involving the scalp blood can track forward
causing bruising to appear around the eyes. Within which layer of the scalp has
this bleeding likely occurred and from what sort of blood vessels (arterial or
venous)?
Venous - emissary veins
Occipitofrontalis anterior attachment is skin over forehead and eyebrows Loose connective tissue which goes all the way around the orbital causing racoon eyes
Following a non-penetrating injury (no open wound) to the scalp e.g. hit your head hard against a door frame,
why does the haematoma form a well circumscribed lump (see image)? Within which layer of the scalp has this bleeding likely occurred?
