Oct9 M2-Anatomy - Cranial Cavity - Notes

Question 1

3 levels, shelves, for the brain in the cranial cavity

Answer 1

• anterior fossa (shelf for frontal lobe)
• middle fossa (shelf for temporal lobe)
• posterior fossa (shelf for cerebellum)

Question 2

why laceration of the scalp could lead to profuse bleeding and spreading of infection into dural venous sinuses

Answer 2

EMISSARY veins (that’s the name) comm between scalp, from under skin and fat (CT deep to skin containing LOT of blood vessels) through skull to dural venous sinus (infection can travel this way)

Question 3

big vessel seen on top of dura mater

Answer 3

middle meningeal artery (imp for trauma and surgery)

Question 4

what meninges have to remove to see brain (sulci and gyri)

Answer 4

dura and arachnoid (if leave arachnoid, don’t see well)

Question 5

landmark of the middle meningeal a (where is it)

Answer 5

• is at the pterion on the temporal skull. a place where 4 bones fuse so bone there fragile in fractures so prob for this artery
• imprint of this artery on the inside of the skull bc of its high P

Question 6

pterion location

Answer 6

1 finger width post and 2 fingers width sup to top of the orbit

Question 7

importance of the dural projections (inner meningeal layer of dura leaves the outer periosteal)

Answer 7

hold the brain in the cranial cavity so it has to follow the head movement

Question 8

2 main projections

Answer 8

• between two hemispheres (falx cerebri)

- between temporal lobes and cerebellum (tentorium cerebelli)

Question 9

important dural venous sinuses (look like veins) in the brain

Answer 9

• superior sagittal sinus (related to falx cerebri)
• inferior sagittal sinus (related to falx cerebri bottom)
• transverse sinus (superficial one (like sup sagittal) related to the tentorium cerebelli)
• straight sinus (travelling from the intersection of the transverse sinus and superior sagittal sinus in the back, towards the front of the brain and fuses with inf. sagittal sinus)

Question 10

straight sinus path

Answer 10

• from intersection of sup sagitt and transverse in the back
• horizontally forward a bit
• then joinds the inf. sagittal sinus
• inf. sagittal sinus arches (like shape of the head) to the front

Question 11

where does the dural venous blood from dural venous sinuses in the brain drain into internal jugular vv

Answer 11

• most imp is the transverse sinuses

- they travel forward laterally to form the internal jugular vv

Question 12

veins other than in the cranial cavity that partially drain into the dural venous sinuses

Answer 12

• ophthalmic v is continuous with the cavernous sinus in the back and is continuous with the facial v in the front
• the facial v drains into the internal jugular v inferiorly (below level of the brain)
• serve as a rescue path for venous blood in case of increased ICP to avoid increased ICP as much as possible*

Question 13

where cavernous sinus drains (note: ophthalmic v drains in it)

Answer 13

in a collateral** (is the important bypass), which then drains in the transverse sinus. like that on each side

Question 14

imp charact of ophthalmic v + facial v

Answer 14

all have no valves, nothing making the blood flow unidirectional

Question 15

danger triangle in the face

Answer 15

triangle between middle of eyebrows and sides of the mouth, including the nose
-the two sides of the triangle (between edges of mouth and in between eyebrows) delineate the facial vv

Question 16

why called the danger triangle

Answer 16

• any cut in this triangle can lead to infection going through facial v, then into ophthalmic v. then cavernous sinus
• infection can accum in the cavernous sinus (note: cavernous sinus imp and relating many things including CNs)

Question 17

cavernous sinuses anat

Answer 17

• bottom = sphenoid bone with outer perisoteal dura
• top = inner meningeal dura that went off the outer periosteal
• pituitary in middle of the sinus
• sinus on each side are connected
• optic chiasm is out of pituitary and on top of the sinus
• internal carotid aa travelling in middle of sinus on each side (lat to pit)
• CNs III, IV, IV (bit more medial), V1 and V2 (note V2 quickly leaves) (top to bottom) travel on each side INSIDE the sinus laterally

Question 18

why is the cavernous sinus a danger space

Answer 18

many imp structures
susceptible to
-fistula (between aa and vv)
-thrombus

Question 19

how CNs exit the cranial cavity

Answer 19

through foramina of the skull. they take the dura mater with them. the dura is then called the epineurium (outermost layer of dense irregular connective tissue surrounding a peripheral nerve)

• VII and VIII exit together. (VIII goes lat to middle ear)
• IX, X and XI exit together

Question 20

where are the midbrain colliculi (sup and inf on both sides)

Answer 20

in the back (dorsal view), so don’t see them in the usual ventral view of the midbrain***. don’t confuse them with mamillary bodies on ventral surface

Question 21

how brain connects to cerebellum

Answer 21

via the pons

Question 22

how CN I exits the skull (what foramina)

Answer 22

cribriform plates. (small holes in the bone)

Question 23

what foramina for CN II (optic)

Answer 23

optic canal

Question 24

what foramina for CN III, IV and VI (and also for V1) (oculomotor, trochlear and abducens)

Answer 24

superior orbital fissure

Question 25

what foramina for VII and VIII (facial and vestibulo-cochlear)

Answer 25

internal acoustic meatus

Question 26

what foramina for IX, X and XI (glossopharyngeal, vagus and spinal accessory)

Answer 26

jugular foramen

Question 27

CNs relation to tentorium cerebelli in the base of the skull

Answer 27

tentorium cerebelli covers CNs III, IV, V and VI before they exit laterally, so they first hide under it (under the dura) before exiting and then they exit the skull

Question 28

meaning of the CNs exiting in specific locations

Answer 28

pathologies at exit affects the diff CNs passing there

• thrombus on right jugular foramen can compress the CNs IX, X and XI
• get weakness of neck (XI), hoarseness and speech prob (X) and dysphagia (IX)

Question 29

3 main trunks of trigeminal n and their exit

Answer 29

• V1 = superior orbital fissure. travels anteriorly (is the one that travels all the way anteriorly to the orbit)
• V2 = foramen rotundum. therefore leaves cav. sinus early
• V3 = foramen ovale
• see split underneath the dura of tentorium cerebelli if remove it*

Question 30

trigeminal n. fct

Answer 30

sensation of face, lip, teeth, nasal cavity, every tissue for sensation (tooth ache, burnt tongue, sinuses hurt)

Question 31

(DNM NAMES OF THE CANALS) V2: 4 diff pathways it can take after exits via foramen rotundum

Answer 31

• inferior orbital fissure (ant inf = travels diagonally downward forward) to go to the face)
• palatine canal (dives inferiorly) to roof of oral cavity
• goes backwards via the pharyngeal canal to reach the nasopharynx (note there is a canal to the cranial cavity on top of the pharyngeal canal called the pterygoid canal but V2 DOESN’T GO THERE)
• sphenopalatine foramen (upwards) to the nasal cavity

Question 32

where does V3 go

Answer 32

foramen ovale. to reach cheek, tongue and mandible

note: V2 upper part of cheek. what’s above the edge of the mouth. V1 = medial part of the face eyes, forehead and nose

Question 33

what divisions of CN V does the dentist freeze

Answer 33

V1 and V2

Question 34

when test with pinprick sensation on the face, what are you testing

Answer 34

the SUPERFICIAL parts of V1, V2 and V3.

Question 35

trigeminal neuralgia def

Answer 35

a whole branch of CN V is inflamed

• for ex, V2 is inflamed, you touch the cheek and the pt feels pain in their nasal cavity = referred pain.
• nasal cavity is also in V2 territory

Question 36

sensory inn. of CN V

Answer 36

• carries sensory info of deep structures as early as the meninges
• V1 goes out the superior orbital fissure and then gives the meningeal branch of V1 which goes to the back of the head by travelling on top of tentorium cerebelli
• V1 IS ALSO WHAT GIVES HEADACHES

Question 37

clinical case: can’t move eye (extraocular muscles affected) + hx of prior lip infection + prob in cavernous sinus on CT what is the problem

Answer 37

compression of nerves in cavernous sinus (CN III, IV, V, VI)