Clinically Relevant Anatomy of Space Occupying Lesions

Question 1

Monro Kellie hypothesis

Answer 1

• -Cranial compartment is incompressible and volume inside cranium is fixed
• -Cranium and its constituents create a state of volume equilibrium, such that an increase in the volume of one constituent must be compensated for by a decrease in the volume of another
• -The principle buffers to increased volume are CSF and blood volume to a lesser extent

Question 2

give an example of an acute and subacute expanding intracranial pathology

Answer 2

• acute - bleed
• subacute - tumour

Question 3

5 layers of scalp - outside to in

Answer 3

• Skin
• Connective tissue
• Aponeurosis
• Loose connective tissue
• Pericranium

Question 4

aponeurosis layer

Answer 4

tendon layer between frontalis and occipitalis muscles

Question 5

why do scalp lacerations bleed excessively

Answer 5

scalp arteries form a rich anastomotic network

Question 6

which layer are the scalp arteries found in

Answer 6

Connective tissue layer

Question 7

which arteries form the anastomotic network in the scalp

Answer 7

internal and external carotid

Question 8

what is the pericranium

Answer 8

periosteum enveloping the skull (outer membrane of bone that is responsible for bone formation)

Question 9

which types of joints are sutures, and what is their purpose

Answer 9

fibrous, to prevent cracks spreading between different skull bones

Question 10

why is the pterion a disadvantage

Answer 10

• thinnest part of skull (frontal, temporal, parietal and sphenoid)
• directly above middle meningeal artery

Question 12

which bone is the carotid canal found in,and what goes through it

Answer 12

temporal bone, internal carotid artery

Question 13

what gives rise to the pain of meningitis

Answer 13

stretching of the dura mater

Question 14

nerve supply to dura mater

Answer 14

sensory supply from CN V

Question 15

describe the structure of the dura mater

Answer 15

• 2 layers: outer periosteal and meningeal
  
  • in parts these are close together
  • in parts there are dural venous sinuses between them

Question 16

diaphragm sellae

Answer 16

sheet of dura mater over the pituitary fossa, has a hole to allow the pituitary stalk through

Question 17

tentorium cerebelli

Answer 17

dura mater sheet over the cerebellum, separating cerebral hemispheres from cerebellum

Question 18

where does the tentorium cerebelli attach

Answer 18

to the ridges of the petrous temporal bones

Question 19

falx cerebri

Answer 19

• midline dura mater sheet
• separates the right and left cerebral hemispheres

Question 20

attachments of the falx cerebri

Answer 20

• crista galli of ethmoid bone anteriorly
• internal aspect of sagittal suture
• internal occipital protuberance posteriorly

Question 21

Answer 21

internal occipital protuberance

Question 22

Answer 22

external occipital protuberance

Question 23

outline the venous drainage of the brain

Answer 23

• cerebral veins drain venous blood from the brain into dural venous sinuses
• dural venous sinuses drain into internal jugular vein at jugular foramen

Question 24

which dural venous sinus drains into the IJV

Answer 24

sigmoid sinus

Question 25

where do the dural venous sinuses confluence

Answer 25

at the internal occipital protuberance

Question 26

why are facial veins atypical

Answer 26

* they have thicker walls so wont collapse and have no valves * this means bacteria could travel up them to the ophthalmic veins and towards cavernous sinus

Question 27

cavernous sinus contents

Answer 27

CNIII, IV, V1, V2, VI and internal carotid artery

Question 28

Answer 28

Question 29

Answer 29

also, left CCA and subclavian artery

Question 30

Answer 30

Question 31

which artery supplies the lateral aspect of the cerebral hemisphere

Answer 31

left and right middle cerebral artery

Question 32

which artery supplies the medial aspect of the right and left cerebral hemisphere

Answer 32

R and L anterior cerebral artery

Question 33

where is the visual cortex located in the brain

Answer 33

posterior aspect

Question 34

which artery supplies the posterior aspect of R and L cerebral hemispheres (including visual cortex)

Answer 34

posterior cerebral artery

Question 35

Answer 35

?? are ophthalmic arteries

Question 36

where is the circle of Willis located in the skull

Answer 36

subarachnoid space

Question 37

outline CSF flow through ventricles of the brain

Answer 37

CSF formed in the choroid plexuses of each **lateral ventricle** flows into the 3^rd ventricle, where more CSF is added by the choroid plexus here. It flows through the cerebral aqueduct of midbrain into the 4^th ventricle, where another choroid plexus adds more CSF. The central canal of the spinal cord is continuous with the 4^th ventricle. CSF then enters the **subarachnoid space** through 3 openings in the roof of the 4^th ventricle: (some CSF enters the central canal of teh spinal cord, whichb is continuous withb the 4th ventricle) * Single medial aperture (Magendie) * Paired lateral apertures (Luschka

Question 38

describe the reabsorption of CSF

Answer 38

CSF then returns to venous blood from subarachnoid space by entering **dural venous sinuses** through **arachnoid granules** into the **superior sagittal sinus**. The dural venous sinuses drain into the IJV at the jugular foramen.

Question 39

management of hydrocephalus

Answer 39

* ventricular peritoneal shunt - sited within the peritoneal cavity

Question 40

where in the head is the middle meningeal artery located

Answer 40

between the bone and dura (remmeber can be damaged by pterion fracture)

Question 41

where in the ehad is the circle of willis located

Answer 41

subarachnoid space

Question 42

where in the mater layers are the cerebral veins located

Answer 42

they cross the subarachnoid space to drain into the dural venous sinuses

Question 43

what kind of aneursym causes a subarachnoid haemorrhage

Answer 43

circle of Willis eg berry aneurysm, these are often congenital

Question 44

what typically causes an extradural haemorrhage

Answer 44

* between bone and dura * eg ruptured middle meningeal artery * can occur after trauma to the pterion

Question 45

what typically causes a subdural haemorrhage

Answer 45

* between dura and arachnoid * eg torn cerebral veins * occurs after falls in the elderly and those with a drinking problem

Question 46

why is L3/4 the best space for a lumbar puncture

Answer 46

* the cauda equina is here not the spinal cord (ends at L2) - these roots are less easily damaged than the conus medullaris * the vertebrae are not fused here (like the sacrum)

Question 47

Answer 47

Question 48

what goes through the anterior and posterior sacral foraminae

Answer 48

anterior and posterior rami of sacral spinal nerves

Question 49

supratentorial herniation: cingulate (subfalcine)

Answer 49

frontal lobe is pushed under the falx cerebri - most common type

Question 50

supratentorial herniation: central

Answer 50

squeezed through a notch in the tentorium cerebelli

Question 51

supratentorial herniation: uncal

Answer 51

brain the uncus (medial part) of the temporal lobe herniates inferior to the tentorium cerebelli

Question 52

supratentorial herniation: transcalvarial

Answer 52

brain squeezes through a fracture/gap in the skull

Question 53

infratentorial herniation

Answer 53

can be upward or downward (into the foramen magnum)

Question 54

which nerve can an uncal herniation damage

Answer 54

CNIII - ipsilateral fixed dilated pupil

Question 55

what do the vertebral arteries branch off

Answer 55

R and L subclavian arteries

Question 56

what can damage to the epidural venous plexus cause

Answer 56

* epidural haematoma * can compress the spinal cord and cause cauda equina if large enough