Complicated Cranial Nerves - Part 1 PDF

Complicated Cranial Nerves – Part 1 Naida Jakirlic, OD, FAAO Head & Neck Anatomy Fall 2024  Learning Objectives ▪ Review key concepts pertaining to the autonomic nervous system ▪ Describe in detail the branches of CN III ▪ Describe in detail the complicated pathways of CN III and the various st...

Complicated Cranial Nerves – Part 1 Naida Jakirlic, OD, FAAO Head & Neck Anatomy Fall 2024  Learning Objectives ▪ Review key concepts pertaining to the autonomic nervous system ▪ Describe in detail the branches of CN III ▪ Describe in detail the complicated pathways of CN III and the various structures it innervates ▪ Describe in detail the ophthalmic and maxillary branches of CN V and the various structures they innervate 2  Autonomic Nervous System ▪ Innervates: ▪ Smooth muscle (walls of blood vessels, muscles of iris) ▪ Cardiac muscle ▪ Glands ▪ Two types of fibers: ▪ Visceral Afferent ▪ Visceral Efferent Autonomic Nervous System ▪ Visceral afferents ▪ Carotid body and sinus (CN IX) ▪ Visceral efferents ▪ Sympathetic ▪ Skin of face and anterior scalp ▪ Smooth muscles and glands ▪ Blood vessels ▪ Parasympathetic ▪ Smooth muscles and glands of head and neck via CN III, VII, IX, and X Visceral Efferent Sympathetic Parasympathetic ▪ Energy expenditure ▪ Energy conservation ▪ Preganglionics: T1-2 ▪ Preganglionics: CN III, VII, IX, X ▪ Synapse: cervical sympathetic ganglia ▪ Synapse: 4 cranial parasympathetic ganglia or directly on target glands ▪ Postganglionics: arterial plexuses of ICA and ECA ▪ Postganglionics: distributed via branches of CN V ▪ Goosebumps, sweating, vasoconstriction, ▪ Salivation, lacrimation, mucus secretion, thickening of saliva, pupil dilation vasodilation, pupil constriction, accommodation Sympathetic ganglia Parasympathetic ganglia ▪ Site of preganglionic parasympathetic synapses from CN III, VII, IX, and X ▪ Four ganglia suspended by CN V ▪ V1: ciliary ganglion (smooth muscle of eye) ▪ V2: pterygopalatine ganglion (lacrimal gland, mucus glands of nose and palate) ▪ V3: submandibular and otic (salivary glands) ▪ Hitchhiking fibers: visceral efferents and special afferents carried in branches of trigeminal nerve (CN V) Questions? 9 Oculomotor Nerve (CN III) ▪ GE: striated muscles of eye and eyelid ▪ Levator palpebrae superioris ▪ Superior rectus ▪ Inferior rectus ▪ Medial rectus ▪ Inferior oblique ▪ VE: smooth muscles of eye ▪ Parasympathetics to pupillary sphincter muscle and ciliary muscle Oculomotor Nerve Two types of nuclei: located in midbrain at the level of the superior colliculi ▪ Oculomotor nucleus: GE ▪ Edinger-Westphal nucleus: VE Oculomotor Nerve ▪ Pathway ▪ Leaves midbrain ▪ Travels lateral to posterior communicating artery ▪ Enters cavernous sinus wall ▪ Divides into superior and inferior divisions anterior to cavernous sinus ▪ Enters SOF and passes through annulus of Zinn 14  Pathways of the Oculomotor Nerve (CN III) Visceral Efferent (CN III) Levator palpebrae superioris General Efferent (CN III) Superior rectus Inferior rectus Medial rectus Inferior oblique Superior Orbital Fissure III Eye Pupillary constrictor Ciliary Ciliary muscle ganglion Nose Slide source: Dr. Rega’s lecture notes 16 Oculomotor nerve: clinical considerations ▪ CN III palsy: intracranial aneurysm until proven otherwise ▪ Signs: ▪ Eye is down and out ▪ Complete ptosis ▪ Pupil is dilated and non-reactive to light https://youtu.be/AEL0xeJ_NSw Primary Gaze Supraduction Right gaze Primary Gaze Infraduction Left gaze 18 18 Questions? 19 Trigeminal nerve (CN V) ▪ Largest cranial nerve ▪ Sensory root: large root in the pons, part of midbrain, and part of medulla ▪ Motor root: separate from the sensory root in the pons 21 22 Trigeminal Ganglion ▪ Aka semilunar ganglion: contains cell bodies of incoming GA fibers from the head & neck ▪ Sits on petrous portion of the temporal bone in Meckel’s cave ▪ Aka trigeminal cave ▪ Covered by meninges ▪ Surrounded by CSF ▪ Three divisions ▪ V1: ophthalmic nerve ▪ V2: maxillary nerve ▪ V3: mandibular nerve Trigeminal Nerve (CN V) ▪ GA: sensation from most of head and neck ▪ GE: motor innervation ▪ Muscles of mastication ▪ Tensor tympani: dampens sound ▪ Anterior belly of digastric: accessory muscle of mastication ▪ Mylohyoid: elevates tongue and hyoid for swallowing ▪ Tensor veli palatini: tenses soft palate Trigeminal Nerve ▪ Suspends 4 parasympathetic ganglia ▪ Ciliary ganglion: postganglionic parasympathetics to smooth muscles of eye ▪ Pterygopalatine ganglion: postganglionic parasympathetics to lacrimal gland ▪ Otic ganglion: postganglionic parasympathetics to parotid gland ▪ Submandibular ganglion: postganglionic parasympathetics to submandibular and sublingual glands (via chorda tympani) Trigeminal Nerve ▪ Carries hitchhiking fibers ▪ SA: taste from anterior 2/3 of tongue and palate (chorda tympani to V3) ▪ Sympathetics from internal carotid artery plexus – innervation of smooth muscles of the eye and blood vessels of the anterior structures ▪ Parasympathetics from CN III, VII, and IX V1: Ophthalmic Nerve ▪ Smallest division ▪ GA only ▪ Travels in lateral wall of cavernous sinus ▪ 4 branches posterior to superior orbital fissure ▪ Frontal ▪ Nasociliary ▪ Lacrimal ▪ Tentorial nerve to the meninges V1  Frontal Nerve ▪ Enters orbit via SOF outside the tendinous ring ▪ Passes between roof of orbit and LPS muscle ▪ Divides into two nerves: ▪ Supraorbital ▪ Supratrochlear V1  Frontal Nerve Branches ▪ Supraorbital ▪ Passes through supraorbital notch/foramen ▪ Innervates frontal sinus, upper eyelid, forehead, scalp ▪ Supratrochlear ▪ Curves around superomedial margin of orbit ▪ Innervates conjunctiva, medial eyelid, forehead  V1  Nasociliary nerve ▪ Passes through SOF and common tendinous ring ▪ Runs along medial wall of orbit ▪ Suspends ciliary ganglion V1  Nasociliary nerve branches  Long ciliary: GA, hitchhiking sympathetic fibers ▪ Infratrochlear  Iris ▪ Conjunctiva ▪ Eyelid  Cornea ▪ Lacrimal sac  Short ciliary: GA, hitchhiking sympathetic & parasympathetic fibers ▪ Caruncle  Ciliary body ▪ Side of nose  Iris sphincter  Anterior ethmoidal  Posterior ethmoidal Trigeminal  Ophthalmic  Nasociliary n. Trigeminal  Ophthalmic  Nasociliary  Infratrochlear Trigeminal  Ophthalmic  Nasociliary  Short ciliary Carry GA fibers back to trigeminal ganglion Carry hitchhiking parasympathetic fibers (VE) to the iris sphincter and ciliary muscles Carry hitchhiking sympathetic fibers to the eye from ICA plexus to blood vessels of the iris and ciliary body Trigeminal  Ophthalmic  Nasociliary  Long ciliary Carry GA fibers from the eyeball and cornea back to the trigeminal ganglion Carry hitchhiking sympathetic fibers from the ICA plexus to the dilator pupillae muscle of the iris Trigeminal n.  Ophthalmic n.  lacrimal nerve ▪ Passes into orbit outside the common tendinous ring ▪ GA innervation to ▪ Lacrimal glands ▪ Conjunctiva ▪ Lateral eyelid ▪ Receives hitchhiking post-ganglionic parasympathetic fibers from pterygopalatine ganglion ▪ VE innervation to lacrimal gland via greater petrosal branch of CN VII Trigeminal nerve  Ophthalmic nerve  Lacrimal nerve Ophthalmic Nerve (V1) Summary ▪ Frontal ▪ Supraorbital ▪ Supratrochlear ▪ Nasociliary ▪ Infratrochlear ▪ Short ciliary ▪ Long ciliary ▪ Anterior ethmoidal ▪ Posterior ethmoidal ▪ Lacrimal ▪ Tentorial nerve V2: Maxillary Nerve ▪ Second major division of CN V ▪ GA only ▪ Suspends pterygopalatine ganglion and carries hitchhiking fibers ▪ Postganglionic parasympathetics to lacrimal gland and nasal and palatal mucosa ▪ Postganglionic sympathetics from ICA to same targets V2: Maxillary Nerve ▪ Course ▪ Trigeminal ganglion ▪ Lateral wall of cavernous sinus ▪ Foramen rotundum ▪ Pterygopalatine fossa ▪ Branches out into several divisions V2: Maxillary Nerve ▪ Branches ▪ Zygomatic ▪ Infraorbital ▪ Greater palatine ▪ Lesser palatine ▪ Nasopalatine ▪ Meningeal branch  V2  Zygomatic Nerve ▪ Formed by merging of zygomaticofacial and zygomaticotemporal nerves within the lateral aspect of the orbit ▪ Zygomaticofacial nerve: sensation from skin of cheek ▪ Zygomaticotemporal nerve: sensation from skin of the temporal region ▪ Conveys hitchhiking post-ganglionic parasympathetic fibers from the pterygopalatine ganglion to the lacrimal nerve https://www.youtube.com/watch?v=Ci8hvbEdF-g https://www.youtube.com/watch?v=v2261IPz3W8 Trigeminal nerve  Maxillary nerve  Zygomatic nerve  V2 V1 V1 V2 Trigeminal nerve  Maxillary nerve  Infraorbital nerve V2: Maxillary Nerve Questions? 52