019 the intracranial region Flashcards
what are the 2 key parts/bone elements of the skull?
- neurocranium - top and back of skull ( main areas)
- viscerocranium - face and jaw
what are fontanelles?
large membranous filled gaps in the skull for movement and deformation during birth and postnatal growth to accommodate the developing brain
- mostly close during the 1st year of life
what holds the bones in the skull together?
- sutures = immobile fibrous joints, mostly made up of type 1 collagen
- are there until about age 21 when they start to ossify
what is the pterion?
- spot above the ear where the parietal, frontal, sphenoid, and temporal bones join together
- it is the weakest part of the skull
- the middle meningeal artery runs underneath it = a trauma here can cause epidural haematoma
what is the intracranial region floor divided into?
3 fossae / depressions
- anterior, middle and posterior cranial fossae
- go down like steps
what is a?
sphenosquamous suture
what is b?
squamous suture
what is c?
squamous part of temporal bone
what is d?
parietal bone
what is e?
parietomastoid suture
what is f?
lambdoid suture
what is g?
asterion
what is h?
occipital bone
what is i?
occipitomastoid suture
what is j?
mastoid part of temporal bone
what is k?
mastoid process
what is l?
tympanic part of temporal bone
what is m?
styloid process
what is n?
condylar process
what is o?
angle of mandible
what is p?
ramus of mandible
what is q?
zygomatic process of temporal bone
what is r?
coronoid process
what is s?
temporal process of zygomatic bone
what is t?
body of mandible
what is u?
mental foramen
what is v?
alveolar part of mandible
what is w?
maxilla
what is x?
zygomatic bone
what is y?
zygomaticofacial foramen
what is z?
nasal bone
what is 1?
lacrimal bone
what is 2
zygomaticotemporal foramen (deep)
what is 3?
sphenoid bone
what is 4?
frontal bone
what is 5?
pterion
what is 6?
coronal suture
what is 7?
sphenoparietal suture
what is a?
sagittal suture
what is b?
parietal bone
what is c?
squamous part of occipital bone
what is d?
occipitalmastoid suture
what is e?
superior nuchal line
what is f?
inion
what is g?
external occipital crest
what is h?
inferior nuchal line
what is i?
mastoid process
what is j?
mastoid notch
what is k?
external occipital protuberance
what is l?
lambdoid suture
what is m?
sutural bone
what are the key structures in the anterior cranial fossa?
- frontal, ethmoid and sphenoid bones
- frontal crest
- crista galli of ethmoid bone
- cribriform plate of ethmoid bone
- body and lesser wings of sphenoid bone
- foramen cecum
what are the key structures of the middle cranial fossa?
- sphenoid, temporal and parietal bones
- optic canal
- tegmen tympani
- arcuate eminence
- foramen rotundum, ovale, spinosum and lacerum
- greater wings of sphenoid bone
- superior orbital fissure
what are the key structures of the posterior cranial fossa?
- occipital, temporal, parietal and tiny bit of sphenoid bone
- clivus
- jugular tubercle
- internal acoustic meatus
- jugular foramen
- hypoglossal canal
- foramen magnum
- internal occipital crest and protuberance
where is the supra-orbital foramen and what passes through it?
- just superior of the eye socket in the frontal bone anteriorly
- supra orbital nerve and vessels
where is the infra-orbital foramen and what passes through it?
- just inferior of the eye socket and lateral to nose in the maxilla bone, anteriorly
- infra orbital nerve and vessels
where is the mental foramen and what passes through it?
- one on each side on the body of the mandible anteriorly
- mental nerve and vessels
where is the zygomaticofacial foramen and what passes through it?
- zygomatic bone near the eye socket in the middle of the bone (lateral)
- zygomaticofacial nerve
where is the parietal foramen and what passes through it?
- either side of the sagittal suture, near the lambdoidal suture
- emissary veins
where is the incisive foramen and what passes through it?
- behind the teeth on the hard palate
- nasopalatine nerve, sphenopalatine vessels
where is the greater palatine foramen and what passes through it?
- at the back of the palate
- greater palatine nerve and vessels
where is the lesser palatine foramen and what passes through it?
- at the back of the palate
- lesser palatine nerve and vessels
where is the pterygoid canal and what passes through it?
- middle cranial in the temporal bone, just posterior to sphenoid lesser wings (inferiorly)
- nerve of pterygoid canal and vessels
where is the foramen ovale and what passes through it?
- middle cranial fossa in the sphenoid bone
- mandibular division of the trigeminal nerve and the lesser petrosal nerve
where is the foramen spinosum and what passes through it?
- middle cranial fossa in the sphenoid bone (almost at temporal bone)
- middle meningeal artery
where is the foramen lacerum and what passes through it?
- where the temporal bone touches the body of sphenoid
- filled with cartilage
where is the carotid canal and what passes through it?
- middle cranial fossa, L shape either side of sphenoid/occipital meeting in the temporal bone (inferior)
- internal carotid artery and nerve plexus
where is the foramen magnum and what passes through it?
- posterior cranial fossa, huge opening in the occipital bone
- brain stem, spinal cord, vertebral arteries and nerve plexuses; anterior spinal artery, posterior spinal arteries, roots of accessory nerve, meninges
where is the condylar canal and what passes through it?
- in the occipital bone just lateral to the foramen magnum
- emissary veins
where is the hypoglossal canal and what passes through it?
- in the occipital bone, lateral to the foramen magnum and occipital condyle
- hypoglossal nerve and vessels
where is the jugular foramen and what passes through it?
-posterior cranial fossa in the temporal bone just medial to the styloid process, anterior to occipital bone
- internal jugular vein, inferior petrosal sinus, glossopharyngeal nerve, vagus nerve, accessory nerve
where is the stylomastoid foramen and what passes through it?
- posterior cranial fossa in the temporal bone, posterior to styloid process and lateral to occipital bone
- facial nerve
where is the foramen cecum and what passes through it?
- on the frontal crest in the frontal bone
- emissary veins to nasal cavity
where is the olfactory foramen and what passes through it?
- cribriform plate of the ethmoid bone
- olfactory nerve
where is the optic canal and what passes through it?
- middle cranial fossa, in the sphenoid bone between the lesser and greater wings
- optic nerve, ophthalmic artery
where is the superior orbital fissure and what passes through it?
- between the lesser and greater wings of the sphenoid bone
- oculomotor nerve, trochlear nerve, ophthalmic division of the trigeminal nerve, abducens nerve, ophthalmic veins
where is the foramen rotundum and what passes through it?
- medial in the greater wing of the sphenoid bone
- maxillary division of the trigeminal nerve
where are the hiatus’ for the greater and lesser petrosal nerves?
- medial temporal bone just posterior to sphenoid bone
where is the internal acoustic meatus and what passes through it?
- medial temporal bone in the posteior cranial fossa
- ## facial nerve, vestibulocochlear nerve and labyrinth artery
what is cranial nerve 1 and what is its function?
- Olfactory nerve
- sense of smell
- special afferent
what is the pathway of the olfactory nerve?
the receptors are in the nasal cavity, the central processes enter the cranial cavity through the cribriform plate of the ethmoid bone
- they then terminate by synapsing with secondary neurons in the olfactory bulbs on the cribiform plate, wither side of the crista galli
what is the clinical findings of a lesion of CNI?
- injury to cribriform plate or congenital absence
- loss of smell (anosmia)
what is cranial nerve 2 and what is its function?
- optic nerve
- vision
- special afferent
what is the pathway of the optic nerve?
- special afferent fibers return information to the brain from photoreceptors in the retina
- neuronal processes leave the retinal receptors and are carried by the optic nerves to the brain via the optic canals in the sphenoid bone between lesser and greater wings
what is the clinical findings of a lesion of CNII?
- direct trauma to orbit, or disruption of optic pathway t brain, e.g. tumour or hemorrhage
- blindness/visual field abnormalities
- loss of pupillary constriction
what is cranial nerve 3 and what is its function?
- oculomotor nerve
- innervates most eye movement muscles (levator palpebrae superioris, superior rectus, inferior rectus, medial rectus, inferior oblique) = general somatic efferent
- innervates sphincter pupillae for pupillary constriction and ciliary muscles for the accommodation of lens for near vision = general visceral efferent
what is the pathway of the oculomotor nerve?
- it leaves the anterior surface of the brainstem between the midbrain and the pons
- enters the anterior edge of the tentorium cerebelli, continues anteriorly in the lateral wall of the cavernous sinus
- leaves the cranial cavity through superior orbital fissure
what are the clinical findings of a lesion of CNIII?
- pressure from an aneurysm arising from cerebral or cerebellar artery, or pressure from a herniating cerebral uncus or cavernous sinus mass/thrombosis
- dilated pupil, ptosis (drooping eyelid), loss of normal pupillary reflex, eye moves down and out
what is cranial nerve 4 and what is its function?
- trochlear nerve
- innervates superior oblique muscle of the eye ( see down and in)
- general somatic effect
what is the pathway of the trochlear nerve?
- arises in the midbrain and is the only cranial nerve to exit from the posterior surface of the brainstem
- enters the inferior surface of the free edge of the tentorium cerebelli, continues in an anterior direction in the lateral wall of the cavernous sinus and enters the orbit through the superior orbital fissure
what are the clinical findings of a lesion of CNIV?
- orbital fracture or damage of nerve around brain stem
- inability to look down and in ( no innervation to superior oblique muscle)
what is cranial nerve 5 and what are its branches?
- trigeminal nerve
- i = ophthalmic
- ii = maxillary
- iii = mandibular
what is the function of CNVi?
- ophthalmic division of the trigeminal nerve
= sensory of eye, conjunctiva, orbital contents, nasal cavity, frontal sinus, ethmoidal cells, upper eyelid, dorsum of nose, anterior part of scalp, dura in anteiror cranial fossa, superior part of tentorium cerebelli
= general somatic afferent
what is the function of CNVii?
- maxillary division of the trigeminal nerve
= sensory of dura in middle cranial fossa, nasopharynx, palate, nasal cavity, upper teeth, maxillary sinus, skin covering the side of the nose, lower eyelid, cheek, upper lip
= general somatic afferent
what is the function of CNViii?
- mandibular division of the trigeminal nerve
= sensory of skin of lower face, cheek, lower lip, anterior part of external ear, part of external acoustic meatus, temporal fossa, anterior 2/3 of tongue, lower teeth, mastoid air cells, mucous membrane of cheek, mandible, dura in middle cranial fossa
= general somatic afferent
muscle = temporalis, masseter, medial and lateral pterygoid, tensor tympani, tensor veli palatini, anterior belly of digastric and mylohyoid muscle
what is the pathway of CNVi?
- (from trigeminal ganglion, from pons)n passes forward in the dura of the lateral wall of the cavernous sinus, leaves the cranial cavity and enters the orbit through the superior orbital fissure
what is the pathway of CNVii?
- branch from trigeminal ganglion (from pons) passes forward in the dura mater of the lateral wall of the cavernous sinus just inferior to the ophthalmic nerve
- leaves the cavity through foramen rotundum and enters pterygopalatine fossa
what is the pathway of CNViii?
- leaves the inferior margin of the trigeminal ganglion (from the pons) and leaves the skull through the foramen ovale and enters the infratemporal fossa
what are the clinical finding of a lesion of the trigeminal nerve?
- sudden shooting pains in face
- numbness in skin of face and anterior parts of tongue
- weakness of muscles of mastication (difficulty chewing and speaking)
what is cranial nerve 6 and what is its function?
- abducens nerve
- innervates the lateral rectus muscle (move eye laterally)
- general somatic efferent
what is the pathway of CNVI?
- abducens nerve arises from the brainstem between the pons and medulla and passes forward piercing the dura covering clivus
- continuing upward in a dural canal, it crosses the superior edge of the petrous part of temporal bone, enters and crosses the cavernous sinus and enters the orbit through the superior orbital fissure
what is the clinical findings of a lesion of CNVI?
- inability of lateral eye movement
- cavernous sinus lesion
what is cranial nerve 7 and what is its function?
- facial nerve
- General somatic afferent = sensory from part of external acoustic meatus and auricle
- Special afferent = taste from anterior 2/3 of tongue
- General visceral efferent = innervates lacrimal gland, submandibular and sublingual salivary glands, mucous membranes of nasal cavity, hard and soft palates
- Branchial efferent = innervates face expression muscles, scalp from 2nd pharyngeal arch, stapedius, posterior belly of digastric, stylohyoid muscles
what is the pathway of the facial nerve?
- attaches to the lateral surface of the brainstem between the pons and medulla
- has a large motor root and smaller sensory root ( the intermediate nerve)
- the roots cross the posterior cranial fossa and leave the cranial cavity through the internal acoustic meatus
- after entering the facial canal in the petrous part of temporal bone, the 2 roots fude and form the facial nerve
- the nerve then enlarges as geniculate ganglion which gives off branches e.g. greater petrosal, nerve to stapedius, chorda tympani
- then exits skull through stylomastoid foramen
what are the clinical findings of a lesion in CNVII?
- paralysis of facial muscles
- abnormal/ no taste of anterior 2/3 of tongue
- due to damage of parotid gland (nerve passes through it), injury to temporal bone, viral inflammation of nerve, brainstem injury
what is cranial nerve 8 and what is its function?
- vestibulocochlear nerve
- vestibular part = for balance
- cochlear part = for hearing
= somatic afferent
what is the pathway of the vestibulocochlear nerve?
- attaches to lateral surface of brainstem between pons and medulla, after emerging from the internal acoustic meatus and crossing the posterior cranial fossa
- the 2 divisions combine into a single nerve in the petrous part of the temporal bone
what are the clinical findings of a lesion of CNVIII?
- progressive unilateral hearing loss and tinnitus
- also cause vertigo/dizziness
- tumour at the cerebellopontine angle, inner ear infection
what is cranial nerve 9 and what is its function?
- glossopharyngeal nerve
- General visceral afferent = sensory from carotid body and sinus
- General somatic afferent = sensory of posterior 1/3 of tongue, palatine tonsils, oropharynx, mucosa of middle ear, pharyngotypmanic tube, mastoid air cells
- Special afferent = taste from posterior 1/3 of tongue
- General visceral efferent = innervates parotid salivary gland
- Branchial efferent = innervates stylopharyngeus muscle
what is the pathway of the glossopharyngeal nerve?
arises as several rootlets on the anterolateral surface of the upper medulla oblongata
- the rootlets cross the posterior cranial fossa and enter the jugular foramen, within it the roots merge to form the glossopharyngeal nerve
- branching from the glossopharyngeal nerve just outside the jugular foramen is the tympanic nerve which reenters the temporal bone, into the middle ear cavity and forms the tympanic plexus
what are the clinical findings of a lesion of CNIX?
- loss of taste to posterior 1/3 of tongue and sensation of soft palate
- due to brainstem lesion or penetrating neck injury
what is cranial nerve 10 and what is its function?
- vagus nerve
- General somatic afferent = sensory from larynx, laryngopharynx, deeper part of auricle, part of acoustic meatus, dura in posterior cranial fossa
- General visceral afferent = sensory from aortic body chemoreceptors and aortic arch baroreceptors, oesophagus, bronchi, lungs, heart, abdominal viscera of the foregut and midgut
- Special afferent = taste from the epiglottis and pharynx
- General visceral efferent = innervates smooth muscle and glands of pharynx, larynx, thoracic viscera, and abdominal viscera of fore and midgut
- Branchial efferent = innervates 1 tongue muscle (palatoglossus), muscles of soft palate except for tensor veli palatini (CNIX), pharynx, except stylopharyngeus (CNIX) and larynx
What is the pathway of the vagus nerve?
- arises as a group of rootlets on the anterolateral surface of the medulla just inferior to CNIX rootlets
- the rootlets cross the posterior cranial fossa and enter the jugular foramen
- within the foramen the rootlets merge to form vagus nerve
- immediately outside foramen 2 ganglia form, superior (jugular) and inferior (nodose) containing cell bodies
what are the clinical findings of a lesion in vagus nerve?
- brainstem lesion or penetrating neck injury
- soft palate deviation, with deviation of uvula to normal side, vocal cord paralysis (cant speak)
what is cranial nerve 11 and what is its function?
- accessory nerve
- Branchial efferent = innervates sternocleidomastoid and trapezius muscles
what is the pathway of the accessory nerve?
- unique cranial nerve as its roots arise from motor neurons in the upper 5 segments of the cervical spinal cord
- these fibres leave the lateral surface of the spinal cord, joining together as they ascend and enter the cranial cavity through foramen magnum
- then it descends in the neck to innervate the trapezius and sternocleidomastoid muscles
what is the clinical findings of a lesion of CNXI?
- paralysis of sternocleidomastoid and trapezius muscle (difficulty rotating and laterally bending head/neck and shrugging shoulders)
- penetrating injury to posterior triangle of neck
what is cranial nerve 12 and what is its function?
- hypoglossal
- General somatic efferent = innervates hyoglossus, genioglossus, styloglossus (extrinsic tongue muscles) and all intrinsic muscles of the tongue
what is the pathway of the hypoglossal nerve?
- arises as several rootlets from the anterior surface of medulla
- passes laterally across posterior cranial fossa and exits through hypoglossal canal
what is the clinical findings of a lesion of CNXII?
- atrophy of ipsilateral muscles of the tongue and deviation towards the affected side
- speech disturbance
- penetrating injury to neck and skull base pathology
what nerves are involved in the corneal / blink reflex?
- afferent = trigeminal nerve, ophthalmic division
- efferent = facial nerve
what nerves are involved in the gag reflex?
- afferent = glossopharyngeal nerve
- efferent = vagus nerve
what nerves are involved in the pupillary light reflex?
- afferent = optic nerve
- efferent = oculomotor nerve
what is the function of general somatic afferent nerves?
- perception of touch, pain, temperature to the brain
- e.g. trigeminal, facial, glossopharyngeal, vagus
what is the function of general visceral afferent nerves?
- sensory input from viscera to brain
- e.g. glossopharyngeal, vagus
what is the function of special afferent nerves?
- smell, taste, vision, hearing and balance receptors to brain
- e.g. olfactory, optic, facial, vestibulocochlear, glossopharyngeal, vagus
what is the function of general somatic efferent nerves?
motor innervation to skeletal muscle
- e.g. oculomotor, trochlear, abducens, hypoglossal
what is the function of general visceral efferent nerves?
motor innervation to smooth muscle, heart muscle and glands
e.g. oculomotor, facial, glossopharyngeal, vagus
what is the function of branchial efferent/special visceral efferent nerves?
motor innervation to skeletal muscles derived from pharyngeal arch mesoderm
- e.g. trigeminal, facial, glossopharyngeal, vagus, accessory
what are the 5 layers of the scalp?
S = skin
C = dense connective tissue
A = epicranial aponeurosis (defining layer for gaping and non-gaping injuries)
L = loose areolar connective tissue, allows free movement of scalp, emissary veins can track infections here
P = periosteum of skull bones, can be detached quite easily
what are the 3 layers of meninges?
- dura, arachnoid, pia
describe features of the dura mater
- thick tough outermost meninge below the periosteum
- 2 layers:
- periosteal layer = firmly attached to periosteum, contains meningeal arteries
- inner meningeal layer = close contact with arachnoid mater - 2 layers of dura separate from each other at dural partititions (e.g. falx cerebri) and intracranial structures
what are the 4 dural partitions in the cranial cavity?
- falx cerebri
- tentorium cerebelli
- falx cerebelli
- diaphragma sellae
describe the falx cerebri
- crescent shaped downwards vertical projection of dura mater the splits the 2 hemispheres
- attached anteriorly to crista galli of ethmoid bone and frontal crest of frontal bone
- posteriorly attaches to tentorium cerebelli
describe the tentorium cerebelli
- horizontal projection of dura mater, covers and separates the cerebellum
- attached posteriorly to the occipital bone and laterally to the superior border of petrous part of the temporal bone
- tentorial notch where the anterior and medial borders are free
describe the falx cerebelli
- small midline projection of dura matter posteriorly between the 2 cerebellar hemispheres
- attached posteriorly to internal occipital crest and superiorly at tentorium cerebelli
describe the diaphragma sellae
- small horizontal shelf of meningeal dura mater covers the hypophyseal fossa in the sella turcica of sphenoid bone
- there is an opening in the centre of the diaphragma sellae through which passes the infundibulum , connecting the pituitary gland with the base of the brain
describe features of the arachnoid mater
- middle meninge
- separated from dura mater via subdural space
- the cerebral veins drain into the sagittal sinus, the veins have to cross the subdural space
- separated from pia mater by the subarachnoid space which contains CSF
- arachnoid mater form arachnoid villi which go into the cranial sinuses and regulate the drainage of cerebrospinal fluid into the venous circulation
- longitudinal fissure between the 2 hemispheres
what is the role of arachnoid villi?
go into the cranial sinuses and regulate the drainage of CSF into venous circulation
describe the pia mater
inner most meninge
- thin delicate membrane that closely invests the surface of the brain and follows its contours
what is the clinical significance of arachnoid villi?
- interruption of normal CSF absorption, due to subarachnoid hemorrhages, can lead to CSF building up in the brain causing hydrocephalus (dilation of cerebral ventricular system
what is an infection of arachnoid and pia mater called?
- rare infection of the leptomeninges = meningitis
- usually blood-borne route, though sometimes from trauma or nasal cavity through cribiform plate or ear infection through mastoid air cells
- can be overwhelmingly inflamed, causing sepsis with cerebral irritation and the patient can rapidly go into a coma and die
what are the main arteries supplying the head and neck?
carotid arteries (internal and external)
what are the main veins draining the head and neck?
- jugular veins (internal and external)
describe the arterial supply of the dura mater
- ethmoidal arteries –> anterior meningeal arteries (anterior cranial fossa)
- maxillary artery –> middle meningeal arteries which split into anterior and posterior branches at the pterion (middle cranial fossa) = through foramen spinosum
- ascending pharyngeal artery –> posterior meningeal artery (posterior cranial fossa) = through hypoglossal canal
- also meningeal branches from occipital (through jugular and mastoid foramen) and vertebral arteries (through foramen magnum)
( all branches off external carotid artery)
what is the innervation of the dura mater?
- ## meningeal branches of all 3 divisions of the trigeminal nerve, and the vagus nerve and C1,2,3
what are the 2 main arteries that supply the brain?
- vertebral arteries (posterior)
- internal carotid (anterior)
what artery do the 2 vertebral arteries join together to form?
- basilar artery
what is the circle of Willis?
a linkage of all the cerebral arteries in the brain to ensure equalisation of blood pressure throughout the brain and gives alternative pathways of blood to the brain if 1 is blocked/ruptured
- mainly supplied from internal carotid and vertebral arteries
describe the circle of Willis from posterior to anterior
- right and left vertebral arteries join together and form the basilar artery in the middle
- anterior spinal artery and posterior inferior cerebellar arteries branch off the vertebral arteries posteriorly to supply back of brain
- anterior inferior cerebellar artery branches off posterior basilar artery
- many pontine arteries branches off the basilar artery
- then anterior to that the superior and then posterior cerebellar arteries branch
- posterior communicating arteries connect both left and right internal carotid arteries to left and right posterior cerebral arteries
- anterior choroidal, ophthalmic, middle cerebral and anterior cerebral arteries branch off internal carotid artery
- anteiror communicating artery between the 2 anterior cerebral arteries makes a full circle
where do the vertebral arteries originate from?
aortic arch –> subclavian –> vertebral arteries
where do the internal carotids originate from?
aortic arch –> brachiocephalic trunk/common carotid –> internal carotid
in the circle of Willis, what branches do the vertebral arteries give off?
- anterior spinal artery
- posterior inferior cerebellar artery
- join to form basilar artery
in the circle of Willis, what branches do the internal carotid arteries give off?
- anterior choroidal artery
- ophthalmic artery
- middle cerebral artery
- anterior cerebral artery
what is the pathway of the internal carotid artery?
- enters skull via carotid canal
- travels within the petrous part of the temporal bone
- crosses over the foramen lacerum (which is filled with fibrocartilage)
- enters the cavernous sinus and travels through it
- ends near the optic chiasm where it splits into its end branches = anterior and middle cerebral arteries
what do cranial sinuses do?
- collect venous blood from cerebral veins, meninges and cranial bones and drains into the jugular vein
what are the names of the venous sinuses in the head?
- superior and inferior sagittal
- straight
- transverse
- sigmoid
- occipital
- cavernous
- sphenoparietal
- superior and inferior petrosal
- basilar
where is the superior sagittal sinus?
- superior border of falx cerebri
- follows sagittal suture from front to back of skull
where is the inferior sagittal sinus?
- inferior border of falx cerebri
- ends at straight sinus/ anterior edge of tentorium cerebelli
where are the transverse, sigmoid, straight sinuses?
- superior sagittal sinus confluences at the meeting between flax cerebri and tentorium cerebelli
- straight sinus comes out of this going posterior to anterior down midline
- transverse goes horizontal following edge of tentorium cerebelli and sigmoid sinus branches off this
where is the cavernous sinus?
- around the sphenoid bone, just posterior to optic chiasm and anterior to sphenoid sinuses
- surrounds pituitary gland
what passes through the cavernous sinus?
Wall anterior to posterior:
- oculomotor nerve 3
- trochlear nerve 4
- trigeminal nerve (ophthalmic and maxillary division) 5
inside anterior to posterior:
- internal carotid
- abducens 6
what does the cavernous sinus receive blood from?
- cerebral, ophthalmic, emissary veins
what are the 5 types of brain hemorrhages?
- epidural/extradural ( between skull and dura mater)
- subdural (between dura and arachnoid mater)
- subarachnoid ( between arachnoid and pia mater, in subarachnoid space
- intraventricular
- intraparenchymal
what usually causes epidural hemorrhage?
- arterial damage, usually middle meningeal artery beneath the pterion (trauma/hit to the head)
what usually causes subdural hemorrhage?
- torn cerebral veins going towards sagittal sinus due to trivial injury
- more common in young and elderly as they have smaller brains and more csf = greater stress on cerebral veins
what usually causes subarachnoid hemorrhage?
- significant cerebral trauma causing intracerebral aneurysm from vessels in the circle of Willis
what do epidural hemorrhages look like on a CT scan?
- lens shape area at edge of skull where bleed is
- shift of falx cerebri/midline of brain due to pressure
what do subdural hemorrhages look like on a CT scan?
- crescent shape area along edge of skull where bleed is
- shift of falx cerebri/midline of brain due to pressure
what do subarachnoid hemorrhages look like on a CT scan?
- appear diffuse, not well defined/ hard to see edge of bleed - spread across brain
- tracks along sulci and fissures of brain
what is an intraventricular bleed in the brain and what does it look like on a CT scan?
- bleed inside the ventricles
- often associated with subarachnoid and intraparenchymal hemorrhages
- see blood filling ventricle on CT scan (light area in dark ventricle
what is an intraparenchymal bleed in the brain and what does it look like on a CT scan?
- inside the brain tissue
- often due to high blood pressure, trauma, or tumour
- causes rounded formation on CT scan
what does 1 show?
- loose connective tissue between the aponeurosis and the periosteum
- in scalping injuries this is where separation often occurs
- infection can easily spread in this layer
- blunt trauma can result in a haemorrhage in this layer which can spread forward causing a black eye
what does 2 show?
rupture of the middle meningeal artery by fracture at the pterion causing epidural haematoma
- under pressure the blood progressively separates dura from bone
what does 3 show?
tear of cerebral vein where it enters cranial venous sinus
- cause subdural haematoma
- the tear separates a thin layer of meningeal dura from that which remains attached to the periosteal layer
- as a result the hematoma is covered by an inner limiting membrane derived from the meningeal dura
what does 4 show?
- aneurysm
- ruptured aneurysm of vessels 0f the cerebral arteries cause subarachnoid hemorrhage and it spreads directly into CSF
