Cranial Nerves Jeffrey K. Marchant, Ph.D.

Transcription

1 Cranial Nerves Jeffrey K. Marchant, Ph.D. CN I olfactory CN II optic CN III oculomotor CV IV trochlear CN V trigeminal CN VI abducent CN VII facial CN VIII vestibulocochlear CN IX glossopharyngeal CN X vagus CN XI spinal accessory CN XII - hypoglossal

2 I II III VI XII V IV VII/VIII IX/X XI

3 Cranial nerves originate from the brainstem*, in order from rostral to caudal midbrain I II III IV brainstem pons V VI VII VIII *except CN I and II that are extensions of the forebrain medulla oblongata XII XI IX X

4 Cranial nerves originate from nuclei* within the brainstem** *motor: somatic visceral sensory: somatic visceral special **except CN I and II that are extensions of the forebrain

5 Nerves shown* are traveling within subarachnoid space (bathed in CSF) and pierce the dura to exit the cranial cavity where they become part of the peripheral nervous system dura mater covering middle cranial fossae I II III IV V VI VII VIII IX X XII XI *except CN I & II which are considered "tracts" (extensions of the brain, covered by meninges) note: part of dura mater has been partially removed on right

6 Sensory only these are all special sensory Motor only these may be all somatic motor or both somatic & visceral motor Mixed these may be somatic & visceral motor and somatic & special sensory I II III* IV V VI VII* VIII IX* X* XII XI *carry parasympathetics (ie visceral motor to glands and smooth/cardiac muscle)

7 Cranial nerves may consist of one or more (sometimes all) types of fibers: Special sensory smell, sight, taste, hearing/balance Visceral sensory afferents from organs Somatic sensory touch, temperature, pain, pressure (skin & mucosal membranes) Somatic motor voluntary (skeletal, striated) muscles Visceral motor smooth muscle, cardiac muscle, glands

8 CN I olfactory, special sensory only olfactory epithelium lateral wall nasal septum olfactory bulb crista galli olfactory tract (extension of the brain) olfactory nerves nasal septum lateral wall of nose

9 Olfactory nerves (CN I) pass through cribiform plate (ethmoid bone) and synapse with neurons (mitral cells) in olfactory bulb crista galli

10 CN I olfactory medial and lateral olfactory stria olfactory bulb olfactory tract prepiriform area amygdala

11 CN I

12 CN II Optic, special sensory only optic nerve (also tract, covered by meninges) optic chiasm optic tract lateral geniculate nucleus visual cortex

13 Optic nerves (CNII) pass through optic canals within sphenoid bone (lesser wing)

14 CN II in optic canal* *together with ophthalmic artery

15 retinal ganglion cells light optic nerve axons of retinal ganglion cells, collectively, make up the optic nerve

16 Light from each eye travels to both sides of brain: -required for depth perception -permits bilateral pupillary light reflex Accessory oculomotor (Edinger-Westphal) nucleus lateral geniculate nucleus visual cortex within occipital lobes

17 CN III oculomotor, all motor (somatic & visceral) Extraocular muscles innervated by CN III: superior rectus inferior rectus medial rectus inferior oblique levator palpebrae superioris CN III CN VI CN IV CN I lateral rectus - CN VI superior oblique - CN IV Right orbit

18 CN III oculomotor, all motor (somatic & visceral) CNIII tendonous ring * * superior and inferior divisions

19 Occulomotor (CN III) nerve enters orbit through the superior orbital fissure (gap between lesser and greater wings of sphenoid bone) GW LW. optic canal tendonous ring for muscle attachment

20 Parasympathetic nervous system (craniosacral) sympathetic nervous system (T1-L2, thoracolumbar)

21 pre- ganglionic fibers post- ganglionic fibers to thorax & abdomen

22 CN III parasympathetic component: to sphincter pupillae and ciliary muscles pre-ganglionic axons brainstem Accessory oculomotor nucleus (Edinger-Westphal nucleus) post-ganglionic axons (short ciliary nerves) targets: ciliary ganglion sphincter pupillae m. ciliary m.

23 Occulomotor parasympathetic component Edinger Westphal nucleus ciliary ganglion preganglionic parasympathetic CNIII postganglionic parasympathetic pre- ganglionic fibers post- ganglionic fibers

24 Parasympathetic target muscles: sphincter pupilae (constricts iris) ciliary muscle (rounds lens) constrictor pupilae ciliary muscle

25 Diagnostic value of CN III: CN III ridge along petrous part of temporal bone Loss/slowness of pupillary reflex may indicate brainstem damage and/or bleeding that compresses CN III against petrous ridge

26 CN IV and VI all somatic motor CN IV, trochlear, superior oblique m. CN VI, abducent, lateral rectus m. LR 6 S0 4 superior oblique trochlea (L. pulley) superior oblique trochlea CN IV lateral rectus CN IV superior view right eye CN VI Right orbit

27 Trochlear (CN IV) & abducent (CN VI) nerves enters orbit through the superior orbital fissure (gap between lesser and greater wings of sphenoid bone) CN IV GW. LW. optic canal CN VI

28 I CN III CN IV CN VI

29 CN V Trigeminal (sensory & motor) -major sensory nerve to face and head outside (and including) the dura mater V 1 V 2 ophthalmic division (V 1 ) motor nucleus V 3 trigeminal ganglion* mandibular division (V 3 ) maxillary division (V 2 ) *sensory, pseudounipolar neurons, no synapses (analogous to DRG)

30 CN V Trigeminal (sensory & motor) -major sensory nerve to face and head outside (and including) the dura mater ophthalmic division (V 1 ) V 1 - ophthalmic V 2 - maxillary (sup. orbital fissure) (foramen rotundum) mandibular division (V 3 ) maxillary division (V 2 ) V 3 -mandibular (foramen ovale)

31 CN V Trigeminal (sensory & motor) -major sensory nerve to face and head outside (and including) the dura mater ophthalmic division (V 1 ) supraorbital nerve (supraorbital foramen) mandibular division (V 3 ) maxillary division (V 2 ) infraorbital nerve (infraorbital foramen) mental nerve (mental foramen)

32

33 CN V Dermatome* Dural innervation ant. & post. ethmoidal meningial branches C2,3 cervical plexus tentorial nerve C2,3 C2 * boundaries much more distinct (less overlap) than dermatomes associated with spinal nerves

34 Ophthalmic division (V 1 ) all somatic sensory superior orbital fissure tentorial n. lacrimal n. frontal n. nasociliary n. supraorbital supratrochlear infratrochlear V 1 Internal sensory regions: nasal cavity paranasal sinuses meninges

35 Maxillary division (V 2 ) all somatic sensory foramen rotundum zygomatic V 2 infraorbital descending palatine posterior superior alveolar Internal sensory regions: nasal cavity paranasal sinuses maxillary teeth hard/soft palate meninges

36 Mandibular division (V 3 ) somatic motor & sensory V 3 foramen ovale buccal auriculotemporal lingual inferior alveolar Internal sensory regions: tongue (ant. 2/3) lower teeth external ear drum cheek (buccal region) meninges mental

37 Mandibular division (V3) motor component Four muscles of mastication, plus... lateral pterygoid temporalis masseter medial pterygoid

38 Accessory muscles of mastication: digastric (ant. belly) myelohyoid tensor tympani tensor veli palatini

39 CN VII facial (somatic motor, visceral motor, special sensory, general sensory) styloid process mastoid process internal acoustic meatus (entrance to facial canal) stylomastoid foramen (exit from facial canal for CN VII somatic motor division)

40 CN VII somatic motor branches to muscles of facial expression*: temporal posterior auricular zygomatic buccal digastric branch cervical mandibular facial nerve * additional muscles innervated by CN VII include: stylohyoid posterior belly of digastric and stapedius

41 CN VII parasympathetic & sensory branches: internal acoustic meatus (entrance to facial canal) CN V chorda tympani* greater petrosal* stylomastoid foramen (exit for motor division CN VII somatic motor route *parasympathetic and sensory components

42 CN VII parasympathetic component: to sublingual, submandibular, lacrimal, nasal/palatine glands intermediate nerve (pre-ganglionic axons for two pathways) brainstem superior salivatory nucleus chorda tympani n. submandibular ganglion greater petrosal n. pterygopalatine ganglion post-ganglionic axons* targets: glands (*often unnamed, but will need to piggy-back on other named nerves - and/or blood vessels - to reach targets)

43 CN VII parasympathetic component: to sublingual, submandibular, lacrimal, nasal/palatine glands intermediate n. (two paths) emerging from superior salivatory nucleus pterygopalatine ganglion greater petrosal nerve lingual nerve (V 3 ) nasal and palatine glands chorda tympani (joining lingual n. from V 3 ) submandibular ganglion sublingual and submandibular glands

44 CN VII special sensory component: taste to anterior 2/3 of tongue nucleus of the solitary tract geniculate ganglion (Sensory) chorda tympani sensory fibers special sensory fibers to anterior 2/3 of tongue

45 Learn pathways by creating a lesion... X X X X

46 CN VIII Vestibulocochlear (special sensory) vestibular system balance cochlea - hearing CN VII internal acoustic meatus CN VIII cochlear & vestibular divisions internal acoustic meatus

47 CN IX glossopharyngeal (somatic motor, visceral motor, special & general sensory) CN IX jugular foramen

48 CN IX somatic motor, special & general sensory: V 3 - sensory VII - taste IX taste + sensory CN X jugular foramen glossopharyngeal nerve special & general sensory to posterior 1/3 of tongue motor branch to stylopharyngeus general sensory to pharynx carotid body carotid sinus

49 CN IX parasympathetic component: visceral motor to parotid gland CNs VII & VIII entering internal acoustic meatus greater petrosal nerve (CN VII) lesser petrosal carotid canal tympanic canaliculus jugular foramen jugular foramen (with internal jugular vein) carotid canal tympanic nerve in canaliculus

50 foramen ovale (V 3 ) preganglionic fibers synapse at otic ganglion* and post-ganglionic fibers then follow auriculotemporal nerve (V 3 ) to parotid** lesser petrosal nerve emerging from middle ear *otic ganglion lies just medial to V 3 as it emerges from foramen ovale so not visible in this image ** sole purpose for otic ganglion is to provide postganglionic fibers to parotid (think "parotic" gland)

51 CN X vagus (somatic motor, visceral motor, special & general sensory) general sensory CN X (emerging from jugular foramen) parasympathetic: to thorax, abdomen & recurrent laryngeal -GI tract -heart -lungs, etc. superior laryngeal nerve special sensory motor: -pharyngeal constrictors -laryngeal muscles -most palatal muscles

52 CN XI spinal accessory (somatic motor to sternocleidomastoid and trapezius muscles) nucleus ambiguus "cranial root" jugular foramen foramen magnum spinal root Spinal nucleus sensory information via C3, C4 sternocleidomastoid trapezius

53 CN XII hypoglossal (somatic motor only) hypoglossal canal olive pyramids CN XII

54 CN XII hypoglossal (somatic motor only) genioglossus hypoglossal n. C1 fibers join hypoglossal and then become part of superior root of ansa cervicalis styloglossus geniohyoid hyoglossus upper & lower genial spines (note: palatoglossus in innervated by CN X)

55 Cranial nerves with parasympathetic components (CN III, VII, IX, X)

56 CN I olfactory CN II optic CN III oculomotor CV IV trochlear CN V trigeminal CN VI abducent CN VII facial CN VIII vestibulocochlear CN IX glossopharyngeal CN X vagus CN XI spinal accessory CN XII - hypoglossal