Anatomy Cranial Nerves

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Cranial Nerve 1: Olfactory Nerve arises?: Arises from olfactory trigone on inferior surface of the forebrain. Tract moved forward on anterior cranial folla floor and ends as two swelling (olfactory bulbs) atop cribiform plate.
-Pass from bulb through the dura and cribiform plate to roof of nasal cavity below
Cranial Nerve 2: optic nerve arises?: Originate: lateral geniculate bodies at base of diencephalong. Pass forward and conver at optic chiasma (not all fibers cross). Passing forward are the left and right optic nerves (still tracts).
-pierce dura to pass through optic forament to enter orbit, -enters posterior aspect of eyeball to synapse with rod and cone cells of retina.
Cranial Nerve 3: Oculomotor Nerve arises?: Emerges from interpenduncular fossa of the midbrain and travels forward to -pierces dura of triangular field to enter cavernous sinus
-travels along lateral sinus wall
-leaves through superior orbital fissurep
Cranial Nerve 4: Trochlear Nerve arises?: Only one to arise form dorsum of brainstem. Slender thread from below the inferior colliculus of the midbrain and encircles brainstem to pass anteriorly.
-pierces dura of triangular field to enter cavernous sinus
-travels along lateral sinus wall
-leaves through superior orbital fissure
Cranial Nerve 5: Trigeminal Nerve arises?: Orinates: pons as thick sensory root and a smaller motor root
-travels anteriorly over petrous rid and pushes the dura ahead of it to produce trigeminal (meckel's) dural cave
-within case, stem dilates as broad flat trigeminal ganglion
Cranial Nerve V-1: Opthalmic Nerve (branch of trigeminal) arises?: -Leaves ganglion and cave to enter cavernous sinus anteriorly
-travels forward along lateral wall of sinus and exits superior orbital fissure to orbit
Cranial Nerve V-2: Maxillary Nerve (branch of trigeminal) arises?: -Leaves cave and passes anteriorly through posteroinferior portion of cavernous sinus
-leaves sinus by passing through foramen rotundum to area of pterygopalatine fossa
Cranial Nerve V-3: Mandibular Nerve (branch of trigeminal) arises?: -Leaves cave and drops straight down through foramen ovale to infratemporal region
-motor portion of trigeminal travels only with mandibular division
Cranial nerve 6: Abducens Nerve arises?: -arise from ventral aspect between Medulla and pons
-ascends on clivus
-pierces dura to run below dura
-passes over petrous temporal ride and enters cavernous sinus
-passes through sinus below internal carotid arter and exits through superior orbital fissure (orbit)
Cranial nerve 7: Facial nerve arises?: -Leaves lateral aspect of brainstem between pons and medulla
-passes laterally, pierces dura and exits through internal auditory meatus to enter petrous temporal bone
-traverses the bone through winding facial canal
-exits inferiorly at base of skull through stylomastoid foramen
Cranial Nerve 8: vestibulocochlear nerve arises?: -arises from brainstem lateral to facial nerve
-runs to internal auditory meatus and enters petrous temporal bone to supply inner ear
-within petrous temporal bone divides into cochear portion to cochlea and vestibular potion to semicircular canals
Cranial Nerve 9: glossopharyngeal nerve arises?: -arises three or four rootlets from lateral aspect of medulla
-converge as one bundle and pass to jugular foramen
-pierces dura and exits through forament to external base of skull
Cranial nerve 10: Vagus Nerve arises?: -arises as several rootlets from medulla
-in line with and below rootlets of glossopharyngeal
-rootlets combine and pass laterally to pierce dura and exit through jugular foramen to neck below
Cranial nerve 11: Accessory Nerve arises?: Arises from
-(1) cranial portion arises as several converging rootlets below vagus nerve
-(2) spinal portion arises from motor spinal contribution of spinal cord segments C1 to C6.
-filaments unite as they ascend upward thorugh foramen magnum and join cranial portion
-pierces dura exits through juglar foramen
-cranial portion splits off to join and distributed along with vagus nerve
-spinal portion exits alone through jugular foramen
-
Cranial Nerve 12: Hypoglossal Nerve arises?: -arises from medulla in cleft between the olive and pyramid as several rootlets
-rootlets combine, pierce dura, and exit through hypoglossal canal
Special sensory of olfactory nerve 1?: -receptor epithelial cells synapse with neurons in olfactory bulb whcih is connecto to brain by olfactory tract (technically part of brain)
Special sensory of olfactory nerve 1 clinical test?: -sense of smell, differentiate odors
Special sensory of optic nerve 2?: -ganglionic cells in retina
-convey information from eye to brain via optic nerve and tracts
Special sensory of optic nerve 2 clinical test?: -Reading eye chart/color/field of view
-visual field determined by examining when patient observes an object moving from lateral to medial
oculomor nerve 3 motor?: -contained in cavernous sinus to enter superior orbital fissure
-Motor to all extrensic muscles of eye, excluding lateral rectus and superior oblique
-CN III after entering superior orbital fissure divides into superior and inferior divisions
-superior division serves as motor innervation to superior rectus and levator palpebrae superior muscle
-inferior division motor to inferior rectus, inferior oblique and medial rectus
Oculomotor nerve 3 preganglionic parasympathetic?: -fibers travel with inferior division and synapse in ciliary ganglion suspended from nasociliary nerve (brach of trigeminal V1)
-post ganglionic fibers pass to the orbit via short ciliary nerves to innervate ciliary muscle and sphincter pupillae muscle of the eye
occulomotor nerve 3 perceived dysfunction?: -damage may cause paralysis of all extraoccular muscles except superior oblique and lateral rectus
-will result in lateral strabismus which is eye turns out because lateral rectus pulls it laterally; i.e. it is unopposed by medial rectus
-ptosis
what is ptosis?: -upper eyelid droops, due to dysfunction of levator palpabrae (innervated by occulomotor nerve aka CN 3)
Clinical test of oculomotor (CN 3)?: -patient asked to follow finger with eyes as it moves up, down, medial, lateral
--watch for crossing of eyes during convergence
-examine pupillary reflex with light shining on and off in each eye
-- compare contractions and dilations
--tests for lack of pupillary light reflex (parasympathetic componenets damaged) so sphincter pupillae msucle does not function and pupil does not decrease in diameter when light shined into eye
Trochlear nerve (CN IV)?: -motor = courses through cavernous sinus and enters orbit through superior orbital fisure;
-superior oblique
-innervates superior oblique muscle of eye
Trochlear nerve (CN IV) clinical test?: -if one of the abducens is damaged, eyes do not move in parallel
-have follow finger up, down, medial, lateral
Trigeinal nerve three branches?: -opthalmic (sensory)
-maxillary (sensory)
-mandibular (sensory and motor)
trigeminal major sensory nerve of?: -face
-teeth (and supporting structures)
-anterior portion of oral cavity
-mucous membrane of the head with cutaneous sensation
Trigeminal provides motor innervation to?: -muscles of massication
-tensor tympani
-tensor (veli)palantine
-mylohyoid
-anterior belly of digastric
Opthalmic V1 3 sensory branches?: -lacrimal nerve
-frontal nerve
-nasociliary nerves
Lacrimal nerve: from opthalmic V1 (trigeminal)
-sensory information from lateral part of upper eyelid, conjunctiva, and lacrimal gland
-runs posteriorly between lateral rectus muscle and roof of orbit to join the frontal and nasocilliary nerves at superior orbital fissure
Frontal nerve: -divides into
-supraorbital nerve which carries sensation from forehead and scalp
-supratrochlear nerve carries sensation from bridge of nose, medial part of upper eyelid, medial forehead
-courses along roof of orbite towards superior orbital fissure and joined by lacrimal and naso ciliiary
nasociliary nerve branches?: -infratrochlear N
-posterior ethmoidal n
-anterior ethmoidal n.
-long ciliary n.
Associationed with ciliary ganglia of CNIII, i.e. ganglion is suspended from nasociliary branch
infratorchelar n.?: branch of nasociliary nerve
-sensory to skin of upper eyelids, lacrimal sac, and side of nose
posterior ethmoidal n?: branch of nasociliary nerve
-go through posterior ethmoidal foramen
-distribute to mucous membrane of posterior ethmoidal air cells and sphenoid sinus
anterior ethmoidal n?: branch of nasociliary nerve (terminal portion)
-passes through anterior ethmoidal foramen, enters nasal cavity and forms two branches internal and external nasal
-supplies anterior ethmoidal cells and then enter anterior fossa of cranium
-terminal brach: external nasal branch, sensory to skin on lower 1/2 of nose
long ciliary nerves?: brach of nasociliary nerve
-accompany short ciliary n. from ciliary ganglion
-pierce sclera around optic n.
-are sensory to eyeball, eg cornea
Perceived dysfunction of opthalmic nerve (CN III)?: -damage to V1 will inhibit the corneal reflex and will reduce or inhibit sensation over the area covered by V1
Clinical test for opthalmic nerve (CN III)?: -test for corneal reflex with wisp of cotton
-prick forehead with pin (pain), apply warm and cold objects (temperature)
Maxiilary nerve V2?: -purely sensory
-arises from trigeminal ganglion, runs forward in the inferior part of cavernous sinus
-leave middle cranial foss through the foramen rotundum
-enters pterygopalatine fossa, leaves through pterygomaxillary fissure
-in pterygopalatine fossa associates with pterygopalatine ganglia (part of CN 7) which is suspended from maxillary division
-fibers from CN V2 pass through ganglia nad have no role in its function
-enter infratemporal fossa and then the floor of the orbit through the inferior orbital fissure
-contianues as the infraorbital n. which exits through the infraorbital canal and foramen
Maxillary nerve V2 sensory informatin from?: -maxilla and overlying skin
-nasal cavity
-palate
-nasopharynx
-meninges of anterio and middle cranial fossa carried to CNS by branches of maxillary of trigeminal
Maxillary branches of trigeminal?: -zygomatic nerve
-infraorbital nerve
-posterior superior alveolar nerve
-middle superior alveolar nerve
-anterior superior alveolar nerve
Zygomatic nerve: brach of maxillary nerve
-divides into zygomaticofacial nerve providing sensation form the cheek and -zygomaticotemporal nerve distributed to the skin of the side of the face
posterior superior alveolar nerves: brach of maxillary nerve
-arise from the maintrunk of hte maxillary nerve
-provides branches to the mucous membrane of the cheek and the adjacent gingiva
-enters same named foramen in maxilla to supply maxillary sinus and molar teeth
infraorbital nerve: brach of maxillary nerve
-after pterygopalatine fossa, maxillary nerve enter the floors of the orbit, thus becoming infraorbital nerve
middle superior alveolar nerve: brach of maxillary nerve
-innervates maxillary sinus, molar, and premolar teeth
anterior superior alveolar nerve: brach of maxillary nerve
-maxillary sinus and anterior teeth,
dental plexus: posterior, middle, and anterior superior alveolar nerves intermingle forming a dental plexus before innervating hte upper teeth
-infraorbital nerve exits skull via same named foramen, -provides innervation to lower eyelid via inferior palpebral branches, side of the nose via external nasal branches, and upper lip via superior labial branches
branches through the pterygopalatine ganglion include?: -pharyngeal = sensory to pharynx
-greater palatine = sensory to hard palate
-lesser palatine = sensory to soft palate
-nasopalatine = anterior region of hard palate and septum of nose
-nasal branches =nasal cavity
NOTE: will also carry sympathetic and parasympathetic modalities
Perceived dysfunction of V2 (maxillary): Will reduce or inhibit sensation over V2 zone
Clinical test of V2 (maxillary): stroke sensory zone of V2 as you would for V1, cotton, pin, then hot and cold
Mandibular nerve (V3): -sensory and motor
-leave middle cranial fossa through foramen
-anterior division (mainly motor)
-posterior division (mainly sensory)
branches from main mandibular trunk?: -recurrent meningeal nerve = ascends back into the skull through foramen spinosum with middle meningeal arter, it supplies the dura
-nerve to tensor tympani muscle
-nerve to tensor veli palatini muscle
-nerve to medial pterygoid muscle
Branches from anterior mandibular?: -motor branches = supply motor innervation to muscle of mastication (temporalis, masseter, and lateral pterygoid muscles)
-Sensory branches
--buccal nerve= only sensory branch from anterior division, sensory to buccal mucosa, does not innervate buccinator msucle (that is done by buccal branch of facial nerve)
Branches from posterior mandibular division?: Lingual, inferior alveolar n, auriculotemporal nerve
lingual n?: branch of poster mandibular division
-provides sensory innervation to mucous membrane of anterior 2/3 of tongue, lingual gingiva, and others advjacent to tongue
-joined by chorda tympani brach of CN 7 which serves 2 functions
(1) special sensory fibers carrying taste from anterior 2/3 tongue
(2) preganglionic parasympathetic fibers destined for the submandibular ganglion (secretomotor to submandibular and sublingual and other minor salivary glands)
Inerior alveolar nerve?: branch of poster mandibular division
-mixed nerve (sensory and motor)
-before entering mandiular forament it gives motor branches to mylohyoid muscle and anterior belly of digastric muscle
-after entering mandibular foramen is only sensory to mandibular teeth, gingiva, chin, and lower lip
-exits mandible as mental nerve
auriculotemporal n: -purely sensory to temporal regions and TMJ
-has two roots that encircle middle meningeal arter
-carries postganglionic parasympathetic axons (secretomotor) from otic ganglion to parotid gland
Perceived dysfunction of mandibular nerve (V3): -loss of senssation on the v3 zone
-paralysis of muscles of mastication
clinical test for mandibular nerve (V3): -stroke sensory zone for sensory component
-for motor ask patient to clench jaws, open and move side to side against resistance
Abducens N (CN 6): Motor
-enters cavernous sinsu and enters orbit through superior orbital fissure
-innervates lateral rectus muscle of eye
-abducens injury results in paralysis of lateral rectus
Perceived dysfunction of Abducens (CN 6)?: damage causes double vision and paralysis of lateral rectus msucle, thus eye remains rotated medially
(clincial test follow finger)
Facial nerve CN 7 leaves from where?: stylomastoid foramen
Internal auditory meatus of Facial nerve CN 7 has two roots?: 1. motor root innervates muscles derived from second branchial arch
2. second (nervus intermedius) contains sensory and autonomic fibers (parasympathetic)
-special sensory fibers for taste anterio 2/3 of tongue
-chordae tympani (parasympathetic and taste
Branches of facial nerve before exiting stylomastoid foramen: - post auricular brach, occipitofrontalist and auricular muscles
- nerve to stapedius muscle (ear)
Branches of facial nerve after exiting stylomastoid foramen: -branch to stylohyoid and posterior belly of digastric
branches in parotid gland: -temporal branch=muscle of external ear and part of frontalis
-zygomatic branch= remainder of frontalis, orbicularis oculi
-buccal branch= buccinator, upper half of orbicularis oris and the dilator msucles inserting into upper lip
- mandibular branch= muscles of lwoer lip
- cervical branch=platysma
visceral motor component (parasympathetic) of facial nerve importance?: -responsible for control of all major glands of the head except for parotid gland (auricomotor nerve from otic ganglion which preganglion is V3)
What do the superior salivatory nucleus of nervus intermedius divide into?: -greater petrosal nerve (to lacrimal and nasal glands)
--parasympathetic nerves synapse in pterygopalatine ganglion before innervating lacrimal glands, and of palate and nasal mucosa
-chorda tympani (submandibular and sublingual glands)
Pterygopalatine ganglion arises?: hangs from maxillary division of trigeminal nerve (V2) in ptergypaltine fossa
What three types of nerve fibers does the pterygopalatine ganglion receive?: -Sensory branches= from maxillary
-sympathetic branches= postganglionic fibers from superior cervical ganglion as the deep petrosal nerve
-parasympathetic preganglionic fibers from facial N.
ONLY parasympathetic fibers synapse in ganglion
Outgoing nerves from pterypalatine ganglion: -greater paltine nerves
-lesser palatine nerve
-nasopalatine nerve
-short sphenopalatine
-pharyngeal branches
Outgoing nerves from pterygopalatine ganglion: nasopalatine nerve: -exits through sphenopalatine foramen to enter the nasal cavity,
-descends to incisive canal and emerges onto hard palate, -branches are nasal to nasal septum and palate to the palatal mucosa
Outgoing nerves from pterypalatine ganglion -lesser palatine nerve: exits through lesser palatine canal to supply mucosa and glands of soft palate
Outgoing nerves from pterypalatine ganglion -greater paltine nerves: exits greater palatine foramen onto mucosa of hard palate
Outgoing nerves from pterypalatine ganglion -short sphenopalatine: -exits through the sphenopaltine foramen to enter the nasal cavity
-supply lateral wall of nasal cavity
Outgoing nerves from pterypalatine ganglion -pharyngeal branches: -exits through the sphenopalatine foramen
-supplies roof of the pharynx
Modalities in nasal, greater, and lesser palatines and pharyngeal nerves includ:: -sensory (via CN V2)
-parasympathetic (CN 7) via greater petrosal nerve
-sympathetic (via deep petrosal nerve; post ganglionic fibers from superior sympathetic ganglion)
Chordae tympani nerve (taste)arises: -arises from facial nerve within facial canal
-passes through middle ear betwen tympanic membrane and handle of malleus
-leaves skull through petrotympanic fissure to join lingual nerve in infratemporal region
-taste fibers distributed to anterior 2/3's of tongue via the lingual nerve
-sensory fibers convey taste from anterior 2/3 of tongue
Chordae tympani nerve (parasympaethic)arises: -synapse in submandibular ganglion which is suspended form lingual nerve
-major source of parasympathetic innervation to the glands of the mouth
-sympathetic postganglionic fibers come from superior cervical ganglion via facial artery
Perceived dysfunction of facial nerve due to injury of terminal branches?: -lesions of terminal branches produce imbalance of the muscles of facial expression
-unilateral expressionless drooping of the face
-paralysis of orbicularis oculis seen by lack of corneal blink
-paralysis of orbilaris oris seen by drooling and problems eating
NOTE: inflammation of nerve withing facial canal is most common cause of bells palsy
-stroke on one side can cause face to sag due to inability to make facial expression
Perceived dysfunction of facial nerve due loss of special sensory component?: -loss of taste to anterior 2/3's of tongue
-lesion to chorda tympani and lingual nerve result in loss of taste, general sensation, and secretion
and paralysis of muscles of mastication
Clinical test for facial nerve: -test for sweet and saly on anterior 2/3's of tongue
-observe tearing with pungent fumes (ammonia)
-observe symmetry of face when asked to do facial expressions
Vestibulocochlear (CN 8): -vestibular nerve for balance and cochlear nerve for hearing joined as a common nerve entering internal acoustic meatus
-cochlear nerve has its peripheral process in organ of Corti (membranous labyrynth), while cell bodies in spiral ganglion
-
Vestibulocochlear (CN 8) perceived dysfunction: -loss of hearing by air conduction indicates lesion or damage to middle ear, loss of bone conduction indicates nerve deafness
-clinical test (test with tuning fork for air and bone conduction)
Glossopharyngeal Nerve (CN 9) Motor: -nerve to stylopharyngeus=innervates only one muscle stylopharyngeus
Glossopharyngeal Nerve (CN 9) sensory: pharyngeal plexus (composed of CN 9 sensory, CN 10 motor and sympathetics)
-sensory to auditory tube, tympanic cavity, palatine fossa, and nasopharynx
-main trunk ends supplying posterior pharyngeal wall while other continue to posterior 1/3 of tongue
Glossopharyngeal Nerve (CN 9) special sensory: taste from posterior 1/3 of tongue
Glossopharyngeal Nerve (CN 9) parasympathetic: tympanic nerve (contains preganglionic fibers) which reenters skull and forms plexus in middle ear cavity
-from plexus arises lesser petrosal nerve which provides preganglion parasympathetic fibers to otic ganglion
-otic ganglion just outside foramen ovale
-postganglionic fibers (secretomotor) and otic ganglion preganglionic synapse and join with auricotemporal n. for distribution into parotid gland
Glossopharyngeal Nerve (CN 9) Carotid sinus: -small branch of CN 9 descend along with interal carotid arter
-nerve functions as bararoceptor within the carotid sinus
Note: vagus part baroceptor also
Glossopharyngeal Nerve (CN 9) perceived dysfunction: -damage to this nerve would reduce or inhibit gag reflex and difficulty swallowing
-reduce sensation on posterior 1/3 of tongue
-blood pressure altered
Glossopharyngeal Nerve (CN 9) Clinical tests: -test gag reflex, swallowing, positions of uvula
-test touch reception on posterior 1/3 of tongue
-neuralgia gives rise to pain, precipitated by swalling or protrusion of tongue
Vagus Nerve (CN 10) arises: -exits posterior cranial fossa via jugular formane and descends in carotid sheath
Vagus Nerve (CN 10) Motor: -innervates msucles of pharynx, via pharyngeal plexus, larynx, and palate
Vagus Nerve (CN 10) sensory: -external auditory meatus, larynx, thorax, and abdomen (visceral afferents)
Vagus Nerve (CN 10) special sensory: taste to epiglottis
Vagus Nerve (CN 10) parasympathetic: innervates viscera of neck, thorax, and abdomen (ganglia many within organs)
Vagus Nerve (CN 10) recurrent laryngeal nerve: -ascends back into the neck on
-supply intrinsic muscles of larynx (except cricothyroid) with motor innervation
Vagus Nerve (CN 10) perceived dysfunction: -hoarseness due to weakness or paralysis of vocal cord
-paralysis of soft palate results in difficulty in swallowing (regurgitation)
Vagus Nerve (CN 10) clinical test: -ask patient to say 'ahh', uvula deviates to unapposed (healthy) side due to action of intact healthy side muscles acting on soft palate
Spinal accessory (XI) aka 11: -Cranial root joins CN 10 and is source of vagal motor fibers
-Spinal root innervates trapezius and sternocleidomastoid msucles
Spinal accessory (XI) aka 11 Perceived dysfunction and clinical test: -damage would reduce or inhibit the movemend of head and shoulders
-ask patient to shrug shoulder for test of trapeqius, turn head against moderate resistance for test of sterncledomastoid
Hypoglossal (CN XII): Motor- innervates all muscles of tongue except palatoglossal
-upper root of ansa cervicalis travels with a portion of CN 12 but is not functionally realted
Hypoglossal (CN XII) perceived dysfunction and clinical test: -lesion results in paralysis of all glossal muscles (except palatoglossus) affected side becomes atrophic
-when tongue is protruded out it deviates towards the affected sid eand that side appear shrunken and wrinkled
-have patients protrude and retract tongue (if damaged tongue deviates to affected side)

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