ALL THE THINGS Flashcards
What 2 skulls do humans have?
neural skull
facial skull
What does the neural skull do for the brain?
it provides protection
What does the facial skull do?
provides support for the teeth, attachment of muscles, etc.
Which skull predominates in the fetus and neonate?
the neural skull predominates
Are the bones of the fetal neurocranium fused?
NO
What are the intervening spaces of the fetal neurocranium filled with?
fibrous membranes
What are Fontanelles?
Larger intervening spaces
What are the main fontanelles?
anterior
sphenoidal
mastoid
What is the anterior fontanelle?
separates the single frontal and two parietal bones
What is the sphenoidal fontanelles?
occupies the area between the sphenoid, parietal, temporal, and frontal bones
What is the mastoid fontanelle?
area between the temporal, occipital, and parietal
What is something normal that the fontanelles do that may seem abnormal?
pulsate
What is indicative of fontanelle pathology?
deformations such as a bulge or depression
What are the fontanelle’s replaced by?
sutures
What are the sutures of the skull?
Sagittal suture (separates left and right parietal bones)
Coronal suture
Lambdoid suture (separates the occipital bone from the parietal and temporal lobes)
What is premature closure of the fontanelles or sutures called and what does it lead to?
craniosynostosis
leads to cranio-facial abnormalities like Crouzon syndrome
How many bones make up the neural skull?
8 bones!
2 parietal 2 temporal 1 frontal 1 occipital 1 sphenoid 1 ethmoid
How many bones make up the facial skull?
14 bones!
2 maxillae (upper jaw) 2 palatine bones (associated with palate) 2 nasal bones 2 inferior conchae 2 zygomatic bones 2 lacrimal bones (tears) 1 vomer 1 mandible (lower jaw)
What are the important foramina of the skull?
superior orbital foramen
superior orbital fissure
infraorbital foramen
mental foramen (chin)
What prominent features are seen from the posterior view of the skull?
sutures
What are Womian Bones?
seen on X-rays as fractures
Associated with Down Syndrome and Brittle Bone syndrome
What is the interior of the skull divided into?
3 fossae that contain regions of the brain as well as the foramina and fissueres that serve as exits from the cranial vault for nerves and vessels
What are the fossae of the skull?
anterior
middle
posterior
What is significant about the anterior fossa?
contains the anterior and inferior parts of the frontal lobes
What forms the anterior fossa?
orbital plate
What is significant about the middle fossa?
butter fly shaped
supports the temporal lobes of the brain and serves to anchor the tentorial fold. Also contains the Sella turcica
Where does the middle fossa extend?
from the crests of the sphenoid bone anteriorly, the greater wings of the sphenoid, and the squamous parts of the temporal bones laterally, and the petrous portion of the temporal bones posteriorly.
What is the sella turcica?
“Turkish saddle”
houses the pituitary gland and many passages for nerves and vessels.
Where does the posterior fossa end?
it ends at the Foramen magnum
What is significant about the posterior fossa?
largest and deepest of the 3 fossa
houses the cerebellum, pons and medulla
How far does the sphenoid bone stretch?
all the way across the cranial fossae (left to right)
What are the points of attachment of the dura mater?
crista galli
clinoid processes
petrous portions of the temportal bone
internal occipital ridge
The crista galli is a projection of what?
the ethmoid bone
Where are the clinoid processes found?
on the sphenoid bone
Where are the petrous bridges found?
temporal bones
Why is the basal view of the skull the most complex?
has many foramina
What injury is common with people sustaining blunt head trauma?
skull base fractures that vary in severity depending on which foramina are affected
What is the Pterion?
a landmark that defines the union of 4 bones:
patietal
frontal
sphenoid
squamous part of temporal
Besides the scalp, what else offers protection to the brain?
2 lamina
meninges - Dura mater, arachnoid space, pia mater
What is the Dura Proper?
it is the inner layer of Dura that is flush with the dura mater of the spinal cord
What is the outer layer of the skull called?
periosteum
What restrains movement of the brain?
dural folds
What does the cranial dura split into?
dural sinues containing venous blood
What are the most importan dural folds?
falx cerebri
tentorium cerebeli
What does the falx cerebri do?
along with the tentorium, prevents the brain from moving side to side
What is the origin of the falx?
from the crista galli
What does the falx form?
the folds between hemispheres
What do the petrous ridge and the clinoid process form?
the “tent” where the brain stem comes through
What is the other smaller dural fold?
dorsum sellae; covers the pituitary fossa
What are the 3 important sites of vulnerability for the brain?
epidural space
sub-dural space
arachnoid granulations
Why is the epidural space vulnerable?
fractures of the skull can lead to this becoming a real space filled with blood
Why is the sub-dural space a vulnerable area?
major sub arachnoid veins must traverse this space to access the superior sagittal sinus and are vulnerable to tearing
Why are the arachnoid granules vulnerable?
CSF exits here
high venous pressure can block the exit of CS and caus ventricles to expand
What is the weakest point of the skull and why?
pterion
skull is thinnest here
What can cause an epidural hematoma to occur?
if one or both lamina of the skull is fractured such that the dura is torn in the region occupied by a meningeal artery, the vessel will rupture and arterial blood will fill up the space
What happens when blood accumulates in the epidural space?
blood forms a focalized swelling that displaces the brain
How is the trauma of an epidural hematoma judged?
by the level of consciousness
alert
stupor
partial coma
deep coma
What does an epidural hematoma look like on a CT?
presents with a lenticular shape
What can happen if displacement due to epidural hematomas is severe?
the temporal lobe can herniate over the tentorium over the brainstem compressing CN III
A severe case of epidural hematoma causing severe displacement can present with what symptoms?
occulomotor palsies
pupillary dilation
ptosis (drooping eyelid)
disruption of the cortico spinal tract leading to motor deficits
What kind of pressure is involved in causing an epidural hematoma?
arterial pressure
What will cause a subdural hematoma?
if trauma causes a shear fore that damages a vein as it traverses this space, venous blood will accumulate in the space
How does a subdural hematoma appear on a CT?
bright
The extent of a subdural hematoma is determined by what?
venous pressure; injury can continue to progress long after initial trauma
As a subdural hematoma becomes more chronic, how does it appear on a CT?
more opaque
What syndromes are subdural hematomas often associated with?
shaken baby syndrome
“roller coaster syndrome”
What is a contusion?
tear in the fabric of the brain that damages blood vessels, glial cells and neurons and usually leads to motor and sensory deficits
What kind of Parkinson’s can a contusion cause?
trauma-induced Parkinson’s
How do contusions appear overtime?
calcified
What are concussions?
blows to the head that result in brief dizziness, disorientation, and sometimes periods of unconsciousness
Multiple minor concussions can lead to what?
they can have a cumulative effect and can cause Chronic traumatic encephalopathy (CTM)
In order to assess head trauma, what scale do we use?
The Glasgow Scale
What is one PARTICULARLY serious consequence of head trauma?
CSF leakage
What is the source of CSF?
ventricular system
What connects the 3rd ventricle to the 4th ventricle?
the Iter
What is another name for the Iter?
cerebral aqueduct of Sylvius
Where is CSF formed?
choroid plexuses in each ventricle
What path does CSF take to get to the subarachnoid space?
lateral ventricles —> foramina of Monroe —> 3rd ventricle —> Iter —> 4th ventricle —> foramina of Luschka and Magendie
What is the volume of the sub-arachnoid space?
150 mL
How much CSF is produced each day?
300 mL
Blockage of the Iter will cause what?
CSF build up in the lateral and 3rd ventricles resulting in Hydrocephalus
What causes congenital hydrocephaly?
infections in the mother during pregnancy (chicken pox, etc.)
What causes acquired hydrocephaly?
injury, brain tumor, infections, etc.
What is compressed in a hydrocephalic patient?
thalamus, basal ganglia, internal capsul
How would you treat a hydrocephalic patient?
by inserting a shunt that passes the CSF from the ventricles to the venous system
What is Pneumocephalus?
a fracture of the frontal sinus that allows the CSF to escape through the nose
How many venous systems are there?
emissary veins
diploic veins
venous sinuses
veins of the subarachnoid space
These are all interconnected
What are the venous systems continuous with?
capillary networks in the pia mater that receive blood from the brain
Where do the superior/inferior cerebral veins drain and where do they merge?
superior/inferior sagittal sinuses
(INFERIOR ONLY)
- –> Great vein of Galen
- –> straight sinus
Merge at the confluens of the sinuses in the occipital region
Where does blood in the venous sinuses ultimately exit?
the internal jugular veins
Increased venous pressure in the superior sagittal sinus can do what?
prevent the arachnoid granulations from opening that will result in increased pressure in the ventricular system
Why is the Cavernous sinus clinically significant?
the facial, angular, and opthalmic vein are all connected to the region of the cavernous sinus
infections adjacent to the nose can spread to the sinus easily and they are tough to treat
pituitary tumors can also interfere with blood flow here
Weakening of the internal carotid artery with formation of an aneurism in the cavernous can lead to what?
the aneurysm can bust, changing the blood pressure in the sinus to arterial
this will cause pulsating exopthalmos
What is pulsating exopthalmos?
swelling of the opthalmic veins in the orbit
What are some symptoms/signs of pulsating exopthalmos?
protruding eyeball that retracts with heartbeat
detectable pulse in the orbit that can be blocked by carotid compression
Bruit (blood flow) can be detected via stethoscope
What are the 2 types of hemorrhagic strokes?
intracerebral (within the brain)
subarachnoid
What causes a hemorrhagic stroke?
a weakened vessel ruptures and bleeds into the surrounding brain
occurs at either an aneurysm or an arteriovenous malformation (AVM)
Where are the striate arteries?
first branches of the middle cerebral artery
What will cause a classic stroke?
embolism dislodges from thrombosis in the carotid artery to pass upward to block the striate arteries
resultant ischemia will damage axons passing through the internal capsul thus causing a paralysis and loss of sensation contralaterally
What are the common sites for aneurysms at the circle of Willis?
Anterior communicating artery
Bifurcation of the internal carotid & Posterior communicating artery
Bifurcation of middle cerebral artery
Basilar artery bifurcation
Remaining posterior circulation arteries
