B5.052 Skull, Scalp, Cranial Fossa, Nose and Paranasal Sinuses Flashcards
skull functions
protects brain
exclusive site of 4/5 sense: sight, olfaction, taste, hearing
openings of both respiratory and digestive tracts
what is the diploic space
space in between the inner and outer table of cortical bone
causes of widening of the diploic space
sickle cell anemia thalassemia iron deficiency anemia renal osteodystrophy hyperparathyroidism
what is Paget’s disease?
causes an increased head size, thickening of skull bones, particularly frontal bone
headaches and hearing loss caused by impinging upon nerves exiting the skull
epidemiology of Paget’s disease
1-2% of Caucasians over 55
uncommon in people under 40
tends to occur in families (having a relative with Pagets makes you 7-10x more likely to develop it)
cause of Paget’s disease
unknown
potentially a slow acting virus
diagnosis of Paget’s disease
skull x-ray
mild elevation of serum alk phos
why is alk phos elevated in Pagets
produced by osteoblastic cells as they try to rebuild bone
treatment for Paget’s
bisphosphonates (induce apoptosis of osteoclasts)
calcitonin
common types of skull fractures
linear 69%
depression 11%
basilar 4%
result of depression fractures
inner table of bone often more extensively fractured than outer table
often cause extradural or epidural hemorrhage
describe the structure of a newborn’s skull
bones of a newborn’s calvaria are joined by dense connective tissue fibrous joints called sutures
softness of bones and looseness of sutures allow compression (molding) through the birth canal and rapid brain growth
small face, only unilamellar bone, no diploe, glabella, superciliary arches, or mastoid processes
styloid process has not fused to temporal bone yet
what is a fontanelle
sites of fibrous sutures where several bones meet
anterior fontanelle
future site of bregma (front part of hear)
junction of coronal and sagittal sutures
closes at 18-24 months
posterior fontanelle
future site of lamba
junction of sagittal and lamdoid sutures
closes at 9 months
premature suture/fontanelle closure
more concerning than a late closure
potential to limit CNS growth
what is craniosynostosis
premature closure of the sutures leads to deformities of the head which inhibit proper brain development
epidemiology of craniosynostosis
1 in 2000 births (75% males, 25% females)
part of a syndrome in 15-40% of patients, but usually isolated
risk factors and treatment of craniosynostosis
environmental factors can increase risk
surgical treatment generally required between 6-12 months or brain growth may be impaired
petrous part of temporal bone
wedge between sphenoid and occipital bones and encloses internal ear
dural sinuses sit on top
sella turcica
superior surface of body of sphenoid bone
forms hypophyseal fossa for the pituitary gland
sphenoid bone
body contains pituitary
lesser wing helps form the posterior edge of anterior cranial fossa
greater wing helps for floor of anterior edge of middle cranial fossa
palate expander
used to expand cartilaginous suture line (generally turns from cartilage to bone during puberty) between maxilla and palatine bones
only work if midline suture is cartilaginous
what are le Fort fractures
common patterns of facial fractures
most people survive unless CNS is affected
le fort I
separates maxillary teeth from rest of face
le fort II
separates upper teeth and nose from the rest of the face
le fort III
fracture through upper portion of the orbits, separating the face from the rest of the skull
5 layers of scalp
- skin
- connective tissue
- aponeurosis
- loose connective tissue
- periostium
connective tissue of scalp
highly vascular with blood vessels attached to the aponeurosis below
aponeurosis of scalp
dense connective tissue
loose connective tissue of scalp
layer upon which aponeurosis glides
periosteum of scalp
dense connective tissue attached to the bone with Sharpey’s fibers
what is the functional scalp
three outer layers of the scalp
skin
connective tissue
aponeurosis
discuss the structure of the functional scalp
dense connective tissue aponeurosis is continuous with the dense connective tissue surrounding the occipitalis posteriorly and the frontalis anteriorly
both muscles are derived from the second branchial arch and are supplied by cranial nerve VII
occipitalis muscle origin
superior nuchal line
scalping
can occur when hair is caught in machinery
3 outer layers (hair, skin, connective tissue, and epicranial aponeurosis) are pulled away as a unit and skull with periosteal connective tissue layer is left exposed
scalp can be reattached if bleeding is controlled
why might a patient die from scalping?
if knocked unconscious
arteries serving the scalp run in the connective tissue layer on top of the epicranial aponeurosis, tend to limit smooth muscle from contracting, allowing continued blood loss
“danger zone” of scalp
loose connective tissue
infection may easily spread within this zone and may also spread intracranially via emissary veins
what are emissary veins
connect the outside of the skull with the dural intracranial sinuses
normal blood flow from inside outward, but no valves so sometimes reverse
lacerations through epicranial aponeurosis
tend to gap widely due to pulling of the frontalis and occipitalis muscles
tend to bleed profusely due to lack of arterial contraction
direct pressure can usually stop it
surgical flaps on scalp
central region of forehead works well because it contains supratrochlear nerve, artery, and vein
can be used to reconstruct a nose
function of the CSF
mechanical and protective support for the brain
brain “weight” is 90% less in water than in air
ion sink for brain excitability
volume of CSF
total: 125-150 mL
75 mL surround the brain, 75 mL surrounds the spinal cord
description of CSF
clear fluid
pink- bleed suspected
cloudy- bacterial or viral infection
pressure = 70-180 mm
describe the production and movement of the CSF
60% is produced in the choroid plexuses within the lateral 3rd and 4th ventricles
passes the interventricular foramina into the 3rd ventricle
down the cerebral aqueduct of the fourth ventricle
out either the median aperture or the two lateral apertures
subarachnoid cisterns
large subarachnoid space
cerebellomedullary cistern
large subarachnoid space at the base of the skull
absorption of CSF
absorbed back into venous blood through arachnoid villi along the superior sagittal sinus
some absorbed along the length of the spinal cord
what is a spinal tap leak
sometimes after a spinal tap has been performed, CSF continues to leak at the site
under pathological conditions which increase intracranial pressure above the tentorium cerebelli (subdural hematoma) or decrease in pressure below tentorium cerebelli (CSF leak from spinal canal) the brain may herniate through the tentorial incisure
what is an extracranial hematoma
goose egg
typically above galea, rarely below
what is the pterion
junction of 4 bones: greater wing of sphenoid, frontal, parietal, and temporal bones
forms an H like structure
what is special about the pterin
skull is particularly thin
frontal branch of the middle meningeal artery runs along the inner surface
causes an epidural hematoma if ruptured
epidural hemorrhage
bleeding from a torn meningeal vessel may lead to an extradural accumulation of blood that can rapidly compress the brain, progressing to herniation or death if not evacuated
what can cause an epidural hemorrhage
depression fracture of the skull
extradural/epidural space
“potential” space superficial to dura matter
subdural space
“potential” space between the dura and then fluid impermeable (membranous) layer of arachnoid
subarachnoid space
real space filled with CSF
how much CSF produced daily
500 ml
list the layers of the meningeal coverings and spaces
skull epidural potential space dura matter subdural potential space arachnoid matter subarachnoid space pia matter brain
subdural hemorrhage
acute or chronic classifications
depends on the pressure of the vessel torn
most often in elderly people, cerebral veins are torn as the enter the superior sagittal sinus following head trauma
cerebral vein tearing
blood leakage may be slow
cerebral artery tearing
blood may spread quickly and over a large area (hemisphere) compressing the brain
most frequent cause of subdural hemorrhage
tearing of the bridging veins between rain surface and dural sinus
can occur as the result of a relatively minor trauma
those at greatest risk of subdural hemorrhage
children (thinner veins) aged adults (longer bridging veins)
subarachnoid hemorrhage
typically due to rupture of an aneurysm as arteries pass within the subarachnoid space
blood in CSF
symptoms of subarachnoid hemorrhage
severe headache stiff neck loss of consciousness often produced by hypertension and results in paralytic strokes spinal tap = bloody
principal sites of cerebral aneurysms
90% on anterior half of circle of Willis (from internal carotid arteries)
10% from posterior circulation off of vertebral arteries
what are arachnoid granulations
hypertrophy of the arachnoid villi results in arachnoid granulations which may form pits on the inner table of cranial bones along the superior sagittal sinus
function of arachnoid villi
site where cerebrospinal fluid returns to venous blood along the superior sagittal sinus
2 pairs of arteries that supply brain blood
- internal carotid arteries
2. vertebral arteries
branches of internal carotid arteries
ophthalmic arteries anterior cerebral arteries anterior communicating artery middle cerebral arteries posterior communicating arteries
ophthalmic arteries
supply eye, orbit, and forehead
anterior cerebral arteries
supply frontal lobes
anterior communicating artery
between anterior cerebral arteries
middle cerebral arteries
supply temporal lobes
posterior communicating arteries
join posterior cerebral arteries
vertebral arteries
pierce the atlantooccipital membrane and dura matter, enter into the subarachnoid space, pass up through the foramen magnum and unite to form a single basilar artery which runs up along the clivus of the occipital bone
branches of vertebral arteries
posterior inferior cerebellar arteries anterior inferior cerebellar arteries superior cerebellar arteries posterior cerebral arteries posterior communicating arteries
posterior cerebral arteries
supplies occipital and temporal lobes
3 types of headaches
- vascular
- muscular contraction
- traction and inflammatory types
sinusitis
inflammation of one or more of the paranasal sinuses, but usually refers to bacterial infection of the sinuses, secondary viral infections or allergic rhinits
acute sinusitis
starts w cold-like symptoms
runny, stuffy nose and facial fain
may start suddenly and last 2-4 weeks
subacute sinus inflammation
4-12 weeks
chronic sinusitis
12 weeks or longer
function of nasal cilia
extremely important in clearing nose, particularly in posterior 2/3 of nasal cavity
basal movement of mucous
posteriorly towards nasopharynx and is most pronounced over middle and inferior conchae
what can adversely affect nasal cilia
heat, cold, dryness, and drugs
secondary infections much more likely if cilia don’t function
deviated nasal septum
occurs in 30% of adults
midline structure of nose frequently deviates to one side or the other
severe deviation of nasal septum
may occlude a nasal fossa, preventing adequate drainage of nose and sinuses
interferes with flow of air on one side
what is anosmia
loss of sense of smell
what can cause anosmia
head trauma may result in shearing of the olfactory nerves as they pass through the cribriform plate
may be early sign of a degenerative brain disease (Parkinson’s or alzheimer’s)
nasal arteries supplying Keisselbach’s area
anterior ethmoid artery
sphenopalatine artery
greater palatine artery
superior labial artery
which nasal arteries can be manually compressed
greater palatine artery
superior labial artery
epistaxis
nosebleed
frequent site is at Kiesselbach’s area
dry air and nose picking may contribute
can be arterial or venous
what is Kiesselbach’s area and why is it susceptible to nosebleeds
4 names arteries (as discussed above) participate in the formation of a rather superficial anastomotic network on the nasal septum just posterior to the vestibular area
what to do for a nosebleed from kiesselbachs plexus
apply pressure on upper lip and hard palate behind incisors cutting off blood from septal branch of the superior labial artery and branches from the greater palatine artery that pass through the incisive formen
discuss the anesthetic process from a broken nose
- topical anesthetic applied to nasal mucosa
- anesthetic injected at bridge of nose bilaterally to block branches of anterior ethmoidal nerves
- needle inserted via nasal vestibule to reach infraorbital nerves
clinical tidbits about toddler’s tendency to stick things up their noses
conchae and meatuses provide excellent sites for lodging of foreign objects and may make them difficult to detect
sphenoid sinus pain
referred to top of head
ethmoid sinus pain
referred to medial and/or lateral to the eyes
frontal and maxillary sinus pain
generally caused by tapping on bone superficial to the sinus
frontal sinus location and drainage
location= under middle turbinate drainage= infundibulum /frontonasal duct
anterior ethmoid sinus location and drainage
location = under middle turbinate drainage = hiatus semilunaris
middle ethmoid sinus location and drainage
location = under middle turbinate drainage = ostia of ethmoid bulla
posterior ethmoid sinus location and drainage
location= under superior turbinate drainage = ostia of posterior ethmoid air cells
sphenoid sinus location and drainage
location = sphenoethmoidal recess drainage = sphenoid ostium
maxillary sinus location and drainage
location = under middle turbinate drainage = maxillary ostium in hiatus semilunaris
