HN Lecture 5

dural folds

-cerebral falx -cerebellar tentorium -cerebellar falx -sellar diaphragm also location of dural venous sinuses btw internal and external dural layers or within folds of internal layer. All lined with endothelium

cavernous sinuses

R&L on either side of sella turcica of middle cranial fossa. R&L communicate via intercavernous sinuses. Somewhat different from other dural venous sinuses bc consist of large plexus of extremely thin-walled vv

vertebral artery

a branch of subclavian, ascends and enters transverse foraminal canal at C6. Exits at C1 and turns medially to enter thru foramen magnum; R & L terminate by joining to form basilar a in cranial cavity which supplies the brain. Branches of this supply spinal cord

hydrocephaly

a condition caused by excess CSF because it CSF is continually produced and in this case there is an interruption of its return to the bloodstream

leptomeninx (leptomeninges)

arachnoid and pia collectively make it up; inflammation of it (leptomeningitis) results from pathogenic microbes and infection and inflammation usually confined to subarachnoid space and here

cranial dura

consists of two layers (periosteal and meningeal layers); potential epidural space exists between periosteal layer of the dura and the cranial bone. Has rich vascular supply primarily thru 3 divisions of trigeminal n & some upper cervical spinal n. Arterial supply from middle maningeal a (branch of maxillary a in infratemporal fossa of deep face) and remainder from internal carotid, external carotid, and vertebral aa

cerebral and cerebellar veins

drain venous blood from brain tissue to dural venous sinuses; referred to as bridging veins b/c must bridge subarachnoid space to gain access to &open into dural venous sinuses

trigeminal nerve (CN V)

emerges from brainstem as separate motor and sensory roots. Ganglion housing cell bodies of general sensory neurons is located in small depression on floor of middle cranial fossa just anterior to petrous crest. Has three divisions emerging from ganglion

facial nerve (CN VII)

enters facial canal of petrous temporal bona via internal auditory meatus

danger triangle of the face

facial v communicates with cavernous since via deep facial v, pterygoid plexus and ophthalmic vv. So, infections of facial v from lacerations of nose or squeezing of pimples on side of nose and upper lip may spread to cranial dural sinuses

vestibulocochlear nerve (CN VIII)

fibers of vestibular apparatus and cochlea emerge into cranial cavity via the internal acoustic meatus

cerebrospinal fluid (CSF)

formed by choroid plexuses located deep within certain portions of ventricular system of brain; gains access to subarachnoid space via openings in roof of 4th ventricle; similar comp to ultra-filtrate of plasma; approx 400mL formed a day and much of it returned to blood thru arachnoid granulations

strong blow to side of head could...

fracture the thin bone overlying the middle meningeal aa (in region of pterion); in such fractures the middle meningeal a may be torn, resulting in arterial blood being actively pumped into the epidural space and resulting in an epidural hematoma

glossopharyngeal nerve (CN IX)

in cranial cavity this nerve is represented by numerous small nerve bundles that exit cavity w/ vagus n and spinal accessory n in jugular foramen

dural venous sinuses

in dural folds and occur btw internal and external dural layers or within folds of internal layer. All lined with endothelium receive venous blood from the brain and transmit it thru and out of cranial cavity. Valveless structures so blood flow in either direction and most drain to internal jugular vv -Tributaries: cerebral and cerebellar vv; diploic vv; emissary vv

pia and arachnoid cranial meninges

in the cranial cavity the arachnoid is connected to pia by meshwork of fine trabeculae; large cisterns of CSF (comparable to lumbar cistern of spinal meninges) occur in locations where space between pia and arachnoid is increased. Subarachnoid space contains major aa and vv of brain tissue subarachnoid hemorrhage leaves extravasated blood from ruptured blood vessels acculumates here neither has direct n or a supplies

meningeal layer

inner layer of cranial dura which more closely follows contours of the brain; usually adherent to other layer but detached where it dips into longitudinal and transverse cerebral fissures of the brain. Structures it forms are called dural folds or dural reflections and prevent cranium from moving

mandibular division (V3) of trigeminal ganglion

motor root joints sensory component at its origin from trigeminal ganglion and it accesses the infratemporal fossa via foramen ovale

spinal accessory nerve (CN XI)

nerve takes origin from superior cervical spine; fibers converge into single bundle that ascends thru foramen magnum and exits cranial cavity thru jugular foramen with glossopharyngeal and vagus nerves

hypoglossal nerve (CN XII)

numerous small nerve bundles exit cranial cavity via hypoglossal canal located in wall of foramen magnum

vagus nerve (CN X)

numerous small nerve bundles exit the cranial cavity with glossopharyngeal and spinal accessory n in jugular foramen

internal carotid artery

originates at superior border of thyroid cartilage from a bifurcation; ascends in carotid sheath w/ no branches &picks up postgang symp fibers from superior cervical ganglion to form carotid symp plexus. At base of skull, enters carotid canal thru carotid foramen of petrous temporal bone. Courses upward along medial side of tympanic cavity and exits foramen lacerum. Enters cavernous sinus and goes to anterior clinoid process then gives off ophthalmic a and passes thru optic canal then passes out of cavernous sinus, turns backward and terminates by dividing into anterior and middle cerebral aa

periosteal layer

outer layer of cranial dura firmly attached to the inner bony surface of the cranial cavity

spinal meninges

pia mater: delicate membrane in intimate contact with the spinal cord; extends into every fissure arachnoid mater: closely lines outer dura mater; btw arachnoid mater and underlying pia mater is the subarachnoid space filled with CSF and contains major arteries and spinal cord. Drua mater: outermost and thickest meninx; fat-filled epidural space exists outside the dura and within vertebral canal

cerebellar falx

sickle-shaped fold of dura that extends into the fissure between R and L cerebellar lobes

cerebral falx

sickle-shaped fold of dura that extends into the longitudinal cerebral fissure of the brain (fissure separating R and L cerebral hemispheres); has a relatively rigid (sharp) inferior edge

communications of cavernous sinuses

superior ophthalmic v, superior petrosal sinus, inferior petrosal sinus, basilar plexus (located on basioccipital clivus in direct com w/ internal vertebral venous plexus thru foramen magnum and during coughing or heavy straining can force venous blood distally), pterygoid plexus of deep face (in direct com with midface via deep facial vein)

dural venous sinuses

superior sagittal, inferior sagittal, straight, confluence of sinuses, transverse, sigmoid, a occipital, cavernous, superior and inferior petrosal

diploic veins

thin walled veins within diploe of calvaria that drain venous blood from calvarial bone. They communicate with veins in scale in addition to dural venous sinuses. Valveless and venous blood can go internally to dural venous or externally to face and scalp. Can spread infections

emissary veins

transverse cranial apertures and foramina to make connections between veins in the face or scalp and dural venous sinuses in the cranial cavity; valveless and venous blood can go internally to dural venous or externally to face and scalp. Can spread infections

sellar diaphragm

transverse fold of dura that extends over hypophyseal fossa of sphenoid bone; securing pituitary gland in place. A central aperture in it transmits the infundibulum of the pituitary gland.

cerebellar tentorium

transversely-oriented fold of dura that extends into the transverse cerebral fissure of the brain; tentorial notch is an opening in the tentorium for passage of the brainstem; the anterior, free edge of the tentorial notch has a relatively rigid edge. On either side of tentorial notch, it is attached to the petrous crests of petrous temporal bone

abducens nerve (CN VI)

travels thru interior of cavernous sinus on the lateral side of internal carotid a to access orbit via superior orbital fissure

maxillary division (V2) of trigeminal ganglion

travels within the lateral, dural wall of cavernous sinus to access pterygopalatine fossa via foramen rotundum

ophthalmic division (V1) of trigeminal ganglion

travels within the lateral, dural wall of cavernous sinus to access the orbit via the superior orbital fissure

arachnoid granulations

tufts of arachnoid matter that protrude into the walls of the dural venous sinuses, esp superior sagittal sinus. Sites where excess CSF is expressed from the subarachnoid space into the venous blood

post lumbar puncture headaches

usually caused by traction on the dura mater due to a change in CSF pressure in subarachnoid space

subdural (dural border) hemorrhage

when brain does move b/c of strong blow to head, bridging veins can be sheared from connections to dural venous sinuses and extravasated blood from torn bridging veins collects btw dura and arachnoid