L2: Meninges

Question 1

Meninges (3)

Answer 1

1. Dura mater (outer and inner layers)
2. Arachnoid mater
3. Pia mater

Question 2

Dura mater layers

Answer 2

Dura mater = thick, tough, outer covering of brain
Outer periosteal layer: contains meningeal arteries, is continuous w periosteum of outer surface of skull at foramen magnum and other intracranial foramina

Inner meningeal layer: continuous w spinal dura mater through foramen magnum

Question 3

Arachnoid mater features

Answer 3

Deep to dura mater
Thin, avascular membrane
Contains trabeculae
The subarachnoid space contains cerebral veins and arteries
Does not enter grooves or fissures except longitudinal fissure between hemispheres
Arachnoid granulations (into superior sagittal sinus)

Question 4

Pia mater features

Answer 4

Invests surface of brain

Question 5

Falx cerebri

Answer 5

Downward projection between 2 cerebral hemispheres

Question 6

Falx cerebelli

Answer 6

Midline projection in post cranial fossa between 2 cerebellar hemispheres

Question 7

Tentorium cerebelli

Answer 7

Horizontal projection, separates cerebellum in post cranial fossa from post parts of cerebral hemispheres
In midline there is oval opening (tentorial notch) where midbrain passes

Question 8

Diaphragma sellae

Answer 8

Small horizontal shelf at sphenoid bone, opening in centre which infundibulum (connects pituitary gland) and accompanying blood vessels pass

Question 9

Arterial supply to dura mater

Answer 9

Arteries to dura mater travel in outer periosteal layer of dura, all are small arteries except MMA

MMA (middle cranial fossa through foramen spinosum, from maxillary a)
Ant branch: passes almost vertically, crosses pterion
Post branch: passes in posterosuperior direction

Question 10

Ant and post meninges arterial supply

Answer 10

Anterior meninges:
Ant branch of MMA + anterior meningeal a (from ethmoidal a)

Posterior meninges:
post branch of MMA + post meningeal a (from ascending pharyngeal a) + branches from occipital a and vertebral a

Question 11

Innervation of dural partitions

Answer 11

Trigeminal n divisons: V1, V2, V3

Also [X] and cervical C1/2, C3 (sometimes)

Question 12

Venous sinuses

Answer 12

Sup. sagittal sinus = empty into R transverse sinua via confluence of sinuses

Inf. sagittal sinus = empty into straight sinus (joined by great cerebral v)

Straight sinus = empty into L transverse sinus via confluence of sinuses

Confluence of sinuses = empty into transverse sinuses

Transverse sinuses (L,R) = empty into sigmoid sinuses

Sigmoid sinuses = empty into internal jugular veins

Cavernous sinuses = empty into superior and inferior petrosal sinus

Question 13

Cavernous sinus contents

Answer 13

Within wall: [III], [IV], [V1], [V2]

Within sinus: internal carotid a, [VI]

Question 14

Cavernous sinus thrombosis

Answer 14

Opthalmic veins drain to cavernous sinus so infection in eye e.g. perioribtal cellulitis can enter skull
–> meningitis
(req antibiotics)

Question 15

Venous drainage of brain

Answer 15

Network of small venous channels -> larger veins -. dural venous sinuses -> internal jugular v

Veins emptying into sinuses:

1. Cerebellar veins (through subarachnoid space), cerebral veins and veins draining brainstem
2. Diploic veins (between int and ext tables of compact bone)
3. Emissary veins (run between outside of cranial cavity and dural venous sinuses)

Question 16

Clinical significance of emissary veins

Answer 16

Have no valves and bacteria from scalp laceration can enter brain veins emissary veins –> meningitis

Question 17

Extradural haemorrhage

Answer 17

Arterial origin usually MMA in temporoparietal region. Almost always due to skull fracture.
Blood collects between clavarium and periosteal layer of dura
(lentiform shape on CT)

Question 18

Subdural haemorrhage

Answer 18

Cerebral venous damage and is between periosteal dura and meningeal dura.
Requires little force to expand this space and damage cerebral veins crossing from brain to superior sagittal sinus.
esp in people with cerebral atrophy or on anticoag
Chronic subdural haemorrhage most common, but an acute bleed can follow high velocity trauma

Question 19

Subarachnoid haemorrhage

Answer 19

Cerebral artery damage/intracerebral bleed.
Usually ruptured cerebral artery aneurysm of circle of willis
Sudden severe headache, vomiting and frequently loss of consciousness