Session 2 - osteology

Question 1

what method do of ossification do the bones of the calvaria (skull cap or vault) undergo

Answer 1

intramembranous ossification

Question 2

what method do of ossification do the bones of the cranial floor undergo

Answer 2

endochondral ossification

Question 3

what is between the inner and outer table of the calvaria

Answer 3

spongy bone called diploe

Question 4

why are edges of the bones of the skull serrated and at what point do these suture line begin to ossify

Answer 4

prevents slippage and movement

ossify around puberty from inside to outside

Question 5

what is strongly adhered to the suture line

Answer 5

periosteum and it is continuous from the outer table along the suture line to the inner table

Question 6

what type of haematoma can extend into the other side of the brain and why

Answer 6

subgaleal (sub aponeurotic) as the heamatoma is above the periosteum

Question 7

what are fontanelles

Answer 7

they are large areas of unossified membranous gaps between flat bones of calvaria which are present int the infant skull

Question 8

why is it important that babies have fontanelles

Answer 8

allows for alteration of the skill size and shape during child birth and permit the growth of infant brain

Question 9

when do the anterior and posterior fontanelles fuse

Answer 9

anterior- 18 months- 2 years

posterior- 1-3 months

Question 10

what is the rare condition in which you get early fusion of fontanelles and suture called ad why is this porblematic

Answer 10

craniosyntosis

it impedes the development of the brain and alters the shape of the skull

Question 11

what should be the shape of the anterior fontanelle in a healthy baby and why is it palpated in newborns

Answer 11

slightly convex shape

used to assess intracranial pressure and state of hydration

Question 12

what are the two main fracture types

Answer 12

linear- pass full thickness of the skull, fairly straight and involve no bone displacement
depressed- fragment is displaced inwards and towards the brain

Question 13

what is likely to be injured to a basilar skull fracture

Answer 13

cranial nerves

prone to causing CSF leaks

Question 14

what area of the skull is most likely to fracture

and which blood vessle underlines it

Answer 14

the pterion as it is the thinnest area of skull

middle meningeal artey

Question 15

what clinical features are seen on a patient with a basilar skull fracture

Answer 15

CSF leaking from nose
racoon eyes
battle eyes
blood behind eardrum

Question 16

what are the three meningeal layers that surrounds the brain called and what is there appearance like

Answer 16

dura - tough fibrous membrane
arachnoid- soft translucent membrane
pia- microsopically thin, delicate and closely adhered to the surface of the brain

Question 17

what is the name of the space between the dura and the arachnoid called

Answer 17

the subdural space

Question 18

what is the name of the space between the pia and the arachnoid called

Answer 18

subarachnoid space

Question 19

what is found within the subarachnoid space

Answer 19

CSF and cerebral blood vessles

Question 20

what are the two layers of dura

Answer 20

periosteal- endosteum lining the inner bones of the skull

meningeal- layer adjacent to arachnoid

Question 21

what does the separation of the two layers of dura form

Answer 21

dural folds

dural venous sinuses (spaces which becomes venous channels)

Question 22

what feeds into the dural venous sinus and what does the dural venous sinus drain into

Answer 22

the cerebral veins feed into the dural venous sinus

they dural venous sinus drains into the internal jugular vein

Question 23

in which cranial fossa does the cerebellum sit

Answer 23

posterior cranial fossa

Question 24

what are the two dural folds called

Answer 24

falx cerebri-sagitala plane

tentorium cerbelli- transverse plane

Question 25

why do we have dural folds

Answer 25

helps to stabilise the brain and acts as rigid dividers

Question 26

what is the negative of having rigid dural folds

Answer 26

a rise in pressure inside the skull can lead to compression and displacement of brain against folds and or through foramen magnus can lead to herniation of brain though foramen magnum

Question 27

what is a dural venous sinus

Answer 27

its is space that is created by the seperation of the meningeal and periosteal layers of dura and is filled with venous blood

Question 28

what is an extrdural haemorrhage and how does it look on CT

Answer 28

``` extradural haematoma (EDH), also known as an epidural haematoma, is a collection of blood that forms between the inner surface of the skull and outer layer of the dura, which is called the endosteal layer (periosteal dura). bleeding most commonly die to a torn middle meningeal artery (Arterial blood) looks like a lens shape ```

Question 29

what is a subdural haemorrhage and how it look on a CT

Answer 29

Subdural haemorrhage (SDH) is a collection of blood accumulating in the subdural space, the potential space between the dura and arachnoid mater of the meninges around the brain. crescent shaped- cannot go to other side of beain as it Venous blood- usually from bridging veins falx cerebri will prevent spread of blood to other side

Question 30

in what age group is subdural hemorrhage more likely to occur and why

Answer 30

elderly | weaker bridging veins

Question 31

what is a subarachnoid haemorrhage

Answer 31

usually secondary due to trauma or because of spontaneous rupture of a blood vessel (circle of willis) blood leaks into subarachnoid space mixing with CSF sudden and often fatal arterial bleed

Question 32

what trasnverses the space between the dura and the arachnoid

Answer 32

bridging veins