Cranial Nerves Robinson 2025 (1) PDF

Cranial Nerves W. Robinson, DPT, Ph.D. Nervous System & Pain Temple University Neuroanatomy Disclosure I currently have no relationships of any kind with any company whose products or services in any way relate to the practice of medicine, medical education, or research....

Cranial Nerves W. Robinson, DPT, Ph.D. Nervous System & Pain Temple University Neuroanatomy Disclosure I currently have no relationships of any kind with any company whose products or services in any way relate to the practice of medicine, medical education, or research. W. Robinson, DPT, Ph.D. Temple University Neuroanatomy Suggested reading: Neuroscience for Dentistry. O’Kane and Barritt, 2022; – Chapter 9 Teach Me Anatomy articles – The Cranial Nerves – Summary of the Cranial Nerves by Katherine Sanders W. Robinson, DPT, Ph.D. Temple University Neuroanatomy Note: Sensory (afferent) modalities: General somatic sensory (GSS) – general sensation from skin. General visceral sensory (GVS) – general sensation from viscera. Special somatic sensory (SSS) – senses derived from ectoderm (e.g. sight, sound, balance). Special visceral sensory (SVS) – senses derived from endoderm (e.g. taste, smell). Motor (efferent) modalities: General somatic motor (GSM) – skeletal muscles. General visceral motor (GVM) – smooth muscles of gut and autonomic motor. Special visceral motor (SVM) – muscles derived from pharyngeal arches. W. Robinson, DPT, Ph.D. Temple University Neuroanatomy Learning Objectives Following today’s presentation, for each of the Cranial Nerve pairs, you should be able to: Correlate the CN number with its descriptive name Explain their basic sensory and/or motor functions Identify their Central Nervous System origin Identify the cranial fossae and foramina through which they travel Describe the location of ganglia/nuclei Cortical region (origin or destination of signal) Predict signs & symptoms if lesioned W. Robinson, DPT, Ph.D.  Temple University Neuroanatomy CN I CN II-VI CN VII-XII Superior view Inferior view dified from Skull & Cranial Cavity lecture (D102) W. Robinson, DPT, Ph.D. Temple University Neuroanatomy CN I – Olfactory Nerve Sensory only Special sensation of smell (olfaction) Origin: emerges from the forebrain CN I fibers pass through foramina of the cribriform plate (ethmoid) Anterior cranial fossa CN I fibers synapse in olfactory glomeruli in olfactory bulb (continuous with olfactory tract) Projects to olfactory cortex of temporal W. Robinson, DPT, P.D. h Temple University Neuroanatomy Olfactory Nerve (CN I) Olfactory bulb and tract Olfactory fibers (CN I) Olfactory receptors W. Robinson, DPT, Ph.D. Temple University Neuroanatomy CN I – Olfactory Nerve Clinical Relevance – Cribriform plate is weak spot of anterior cranial fossa – Trauma/fracture here can lead to anosmia W. Robinson, DPT, Ph.D. Temple University Neuroanatomy CN II – Optic Nerve Sensory only Special sensation of sight (vision) Origin: emerges from the forebrain CN II (retinal ganglion cell axons) pass through optic canal Optic chiasm in middle cranial fossa; axons continue in optic tract Lateral Geniculate Nucleus of thalamus Optic radiations project to occipital lobe W. Robinson, DPT, P.D. h Temple University Neuroanatomy Optic Nerve (CN II) Optic nerve Optic chiasm Optic tract LGN Optic radiations Inferior view W. Robinson, DPT, Ph.D. Temple University Neuroanatomy CN II – Optic Nerve Clinical Relevance – Optic nerve transection (trauma) or pathologic damage (increased intraocular pressure or tumor) results in anopsia (unilateral blindness) * If this is your patient, you may wish to caution them to be vigilant with eye protection for the functioning eye W. Robinson, DPT, Ph.D. Temple University Neuroanatomy CN III – Oculomotor Nerve Motor only Somatic efferent innervation to several extraocular muscles – Superior rectus – Medial rectus – Inferior rectus – Inferior oblique – + Levator palpebrae superioris Parasympathetic innervation to intraocular muscles – Pupillary constrictor – Ciliary muscle Origin: emerges from midbrain CN III passes into the orbit through the superior orbital fissure Middle cranial fossa Oculomotor nuclei (including Edinger-Westphal) are W. Robinson, DPT, Ph.D. Temple University Neuroanatomy Sudden onset of CN III palsy suggests bad news: trauma, aneurysm, brain herniation W. Robinson, DPT, Ph.D. Temple University Neuroanatomy CN IV – Trochlear Nerve Motor only Somatic efferent innervation to one extraocular muscle – Superior oblique Actions – Intorsion – Depression – Abduction Origin: emerges from dorsal midbrain CN IV passes into the orbit through the superior orbital fissure Middle cranial fossa Trochlear nucleus located in midbrain W. Robinson, DPT, Ph.D. Temple University Neuroanatomy Clinical Presentations – Trochlear palsy Left (affected) eye elevated and Right (affected) eye is extorted due adducted due to unopposed actions to unopposed action of inferior of superior rectus and medial rectus oblique; compensatory head tilt to bring eyes into better alignment W. Robinson, DPT, Ph.D. Temple University Neuroanatomy CN V – Trigeminal Nerve summary* Trigeminal Fissure/foramina Function Ganglia in middle Cortex Nerve emerges within middle cranial fossa / from pons; cranial fossa nuclei within pons Divisions: V1 Ophthalmic Superior orbital Somatic sensory Trigeminal sensory Parietal lobe, fissure ganglion Postcentral gyrus V2 Maxillary Foramen Somatic sensory Trigeminal sensory Parietal lobe, rotundum ganglion Postcentral gyrus V2 Mandibular Foramen ovale Somatic sensory Trigeminal sensory Parietal lobe, & motor ganglion; motor Postcentral gyrus; nucleus in pons Frontal lobe, Precentral gyrus *for more detail, see Trigeminal lecture W. Robinson, DPT, Ph.D. Temple University Neuroanatomy Gross Anatomy Review Optic Nerves Internal carotid artery Pituitary Gland CN III CN IV CN V - Ophthalmic Division CN V - Maxillary Division Cavernous sinus CN V - Mandibular Division Trigeminal ganglion Trigeminal cave (sensory ganglion) (Meckels cave) CN VI CNs VII and VIII CNs IX and X CN XII CN XI W. Robinson, DPT, Ph.D. Temple University Neuroanatomy CN VI – Abducens Nerve Motor only Somatic efferent innervation to one extraocular muscle – Lateral rectus Action: Abduction Origin: emerges from pontomedullary junction CN VI passes into the orbit through the superior orbital fissure Middle cranial fossa Abducens ganglion located in pons Cortex: frontal lobe W. Robinson, DPT, Ph.D. Temple University Neuroanatomy Clinical Presentation – Abducens palsy W. Robinson, DPT, Ph.D. Temple University Neuroanatomy CN VII – Facial Nerve summary* Facial Nerve Motor Function Sensory Ganglia / nuclei Cortex emerges from via (motor) branches functions pontomedullary junction then, Posterior cranial Innervation of muscles General Geniculate fossa of facial expression via sensation: (sensory) ganglia following branches: inconsequential in facial canal Foramina: Temporal Internal acoustic Zygomatic Special: Motor nucleus in Frontal lobe, meatus Buccal Taste; anterior pons Precentral gyrus Mandibular tongue, via Stylomastoid Cervical foramen chorda tympani Additional parasympathetic secretomotor functions* *for more detail, see Facial Nerve lecture W. Robinson, DPT, Ph.D. Temple University Neuroanatomy CN VII Clinical Presentation – Bell’s Palsy Cause: idiopathic Treatment – Corticosteroids … or not – Typically self- resolving within ~6 months – Protect the affected eye Prevent – Drying W. Robinson, DPT, Ph.D. Temple University Neuroanatomy CN VIII – Vestibulocochlear Nerve Sensory only Special sensations CN VIII Lesion – Auditory (hearing) ⁃ Unilateral hearing loss – Vestibular (balance) ⁃ Vertigo Origin: emerges from the pontomedullary junction CN VIII passes through posterior cranial fossa CN VIII exits cranium via internal acoustic meatus Vestibular- and cochlear- ganglia in pons/medulla W. Robinson, DPT, Ph.D. Temple University Neuroanatomy CN VIII – Clinical Considerations With CN VIII lesions at the internal acoustic meatus or in the petrous temporal bone, consider CN VIIW. Robinson, as well DPT, P.D. h Temple University Neuroanatomy CN IX – Glossopharyngeal Nerve Sensory & Motor Functions – Sensory: General: posterior tongue, oropharynx, middle ear, Eustachian tube Special: Taste (posterior tongue) – Motor Somatic: clinically inconsequential Autonomic (parasympathetic): secretomotor to parotid Origin: Medulla CN IX fibers pass through the posterior cranial fossa to exit the jugular foramen Nuclei: located in medulla Taste registers in the insular cortex W. Robinson, DPT, Ph.D. Temple University Neuroanatomy CN IX – Clinical Consideration When testing the gag reflex, the stimulus is detected by the sensory receptors of CN IX – CN X is responsible for the efferent response Since CNs IX, X, & XI pass through the jugular foramen, stenosis or space-occupying lesions in the posterior cranial fossa may affect W. Robinson, DPT, Ph.D. Temple University Neuroanatomy CN X – Vagus Nerve Sensory & motor functions – General sensation: larynx & pharynx – Visceral afferents for thoracic & abdominal organs – Special sensation: taste (epiglottis) – Motor: larynx, pharynx, & soft palate – Parasympathetic innervation Innervates smooth muscle of the trachea, bronchi, gastro-intestinal tract and regulates heart rhythm W. Robinson, DPT, Ph.D. Temple University Neuroanatomy CN X – Vagus Nerve Origin: Medulla CN X fibers pass through the posterior cranial fossa to exit the jugular foramen Nuclei: located in medulla Cortex: Motor commands from frontal lobe Taste registers in the insular cortex W. Robinson, DPT, Ph.D. Temple University Neuroanatomy CN X – Clinical Considerations Complete CN X lesions are rare, but some branches (example: recurrent laryngeal) are susceptible to compression The vagus nerve has far-ranging effects, which pharmacotherapeutics often take advantage of – Beta-blockers, muscarinic agonists & W. Robinson, DPT, Ph.D. Temple University Neuroanatomy CN XI – Spinal Accessory Nerve Motor only Somatic efferent innervation to two muscles – Sternocleidomastoid – Trapezius Origin: emerges from medulla CN XI fibers pass through the posterior cranial fossa to exit the jugular foramen (spinal part of CN XI has fibers that ascend through foramen magnum) Nuclei: located in medulla & upper cervical spinal cord Cortex: Motor commands from frontal lobe W. Robinson, DPT, Ph.D. Temple University Neuroanatomy CN XI– Clinical Considerations W. Robinson, DPT, Ph.D. Temple University Neuroanatomy CN XII – Hypoglossal Nerve Motor only Somatic efferent innervation to tongue muscles – Genioglossus – Hyoglossus – Styloglossus Origin: emerges from medulla CN XII fibers pass through the posterior cranial fossa to exit the hypoglossal canal Hypoglossal nuclei: located in medulla Cortex: Motor commands from frontal lobe W. Robinson, DPT, Ph.D. Temple University Neuroanatomy UMN (CBT) lesions vs. LMN (CN XII) lesions CBT to Hypoglossal nucleus decussates Lesions superior to the hypoglossal nucleus will cause contralateral tongue deviation CN XII to genioglossus is ipsilateral Lesions inferior to the CN From Corticobulbar XII nucleus lecture (D102) W. Robinson, DPT, Ph.D. Temple University Neuroanatomy W. Robinson, DPT, Ph.D.