1. ANATOMY CRANIAL NERVES ANATOMY Keele Neurology Society Aziza Mohamed Aisha Saleem

2. Introduction Twelve pairs of cranial nerves that originate from the forebrain, brainstem and rostral spinal cord. Form part of the peripheral nervous system – similar properties to spinal nerves. Responsible for sensory, motor and/or autonomic function in mainly* functional regions of head and neck. Integral part of neurological examination.*

3. Cranial Nerve Function Overview Sensory, motor, autonomic or mixed. Can receive afferents or send impulses locally or to regions such as thoracic and abdominal viscera (e.g. CN X Vagus Nerve). Sensory - general somatic afferent, general visceral afferent or special afferent. Motor - general somatic efferent or branchial motor efferents. General or special visceral efferents are also described as - Parasympathetic efferents.

4. Internal Cranium Base – Quick Overview

5. Cranial Nerve Foramina

6. Cranial Nerve I: Olfactory FORAMEN - Cribriform Plate of the Ethmoid Bone Sensory – perception of smell. Transmitted into the frontal lobe from olfactory epithelium. SENSORY SENSORY - Special Afferent

7. Cranial Nerve II: Optic FORAMEN - Optic canal Sensory – perception of vision; detects and transmits light input from optic disc at retina. NB: Contralateral; optic chiasm at the sphenoid wing involves decussation of the nerves into the optic tract. SENSORY SENSORY - Special afferent

8. Cranial Nerve III: Occulomotor FORAMEN - Superior Orbital Fissure Motor - Controls four of the six extraoccular muscles ; superior rectus, inferior rectus, medial rectus and inferior oblique muscles. *Also controls levator palpebrae superioris (upper eyelid muscle) Parasympathetic efferent – innervates sphincter pupillae for pupil constriction and ciliary muscle accommodation of lens at near vision. MOTOR – occulomotor nerve palsy (down and out – neurogenic ptosis causes drooping of the eyelid due to damage to CN III) PARASYMPATHETIC EFFERENTS

9. Cranial Nerve IV: Trochlear FORAMEN - Superior Orbital Fissure Motor - controls the movement of the superior oblique muscle of the eye. Aids internal rotation of eye. *SO4 – Trochlear (CN IV) MOTOR

10. Cranial Nerve V: Trigeminal FORAMEN – Varied: – V 1 [opthalmic] - Superior Orbital Fissure – V 2 [maxillary] - Foramen Rotundum – V 3 [mandibular] - Foramen Ovale Sensory – touch, temperature perception on different regions of face (testing with soft/crude touch and temperature). Motor - Muscles of mastication particularly masseter and temporalis SENSORY - MOTOR -

11. Cranial Nerve VI: Abducens FORAMEN – Superior Orbital Fissure Motor - Lateral rectus muscle of the eye. Enables abduction of the eye. *LR6 – Abducens (CN VI) MOTOR

12. Cranial Nerve VII: Facial FORAMEN – Internal Acoustic Meatus Sensory – special sensory is anterior 2/3 taste of tongue and external acoustic meatus (including auricle) Motor – muscles of facial expressions [5 branches] and neck muscles. Parasympathetic – submandibular, sublingual and lacrimal salivary glands. Also innervates mucous membranes of nasal cavity. SENSORYMOTOR PARASYMPATHETIC EFFERENTS 1.Temporal 2.Zygomatic 3.Buccal 4.Maxillary 5.Cervical

13. Cranial Nerve VIII: Vestibulocochlear FORAMEN – Internal Acoustic Meatus Sensory – special sensory function: – Vestibular division responsible for balance – Cochlear division responsible for hearing SENSORY SENSORY - special afferent

14. Cranial Nerve IX: Glossopharyngeal FORAMEN – Jugular Foramen Sensory – input from the carotid body and sinus (detects changes in PCO 2 and pressure). Taste in posterior 1/3 of tongue. Motor – controls stylopharyngeal muscle for swallowing. Parasympathetic efferent - innervates parotid salivary gland SENSORYMOTOR PARASYMPATHETIC EFFERENTS

15. Cranial Nerve X: Vagus FORAMEN – Jugular Foramen Sensory – varied: – Sensation in larynx, laryngopharynx, including parts of the external acoustic meatus. – Sensory from the aortic body and aortic sinus, thoracic and abdominal viscera. – Taste in the epiglottis and upper pharynx Motor – innervates only one tongue muscle, varied muscles in pharynx and larynx. – Aid in speech and swallowing Parasympathetic efferents – innervates smooth muscles and glands in throat region, thoracic viscera and abdominal viscera upto the midgut. ( 2/3 of Transverse Colon ) SENSORY MOTOR - dysphagia ( ) MOTOR - dysphagia (often seen in patients who’ve suffered from stroke ) PARASYMPATHETIC EFFERENTS

16. Cranial Nerve XI: Accessory FORAMEN - Jugular Foramen Motor – innervates sternocleidomastoid muscle and trapezius muscles of neck and shoulder region. Aids rotation and flexion of head and neck; shrugging move scapula and support arm. MOTOR -

17. Cranial Nerve XII: Hypoglossal FORAMEN - Hypoglossal Canal (lateral to Foramen Magnum) Motor – control of tongue muscles; including pharynx and larynx (muscles of speech and swallowing). MOTOR - “the tongue licks the wound” (damage to the hypoglossal nerve leads to deviation of tongue to ipsilateral side where injury occurred)

18. Origin of Cranial Nerves CN I – Olfactory Bulb (inf. surface of Frontal Lobe) CN I – Olfactory Bulb (inf. surface of Frontal Lobe) CN – Retina CN – Retina CN III – Midbrain CN IV – Midbrain CN V – PONS CN VI – PONS CN VII – PONS CN VIII – PONS CN IX – Medulla CN X – Medulla CN XI – Spinal Cord* CN XII – Medulla Majority of cranial nerves originate from the brainstem (CN III – CN XII [excluding CN XI])

19. Cranial Nerve Nuclei Cranial Nerve Nuclei* *Spinal Accessory Nerve XI – Originates from spinal cord directly

20. Mnemonics Oh Once One Takes The Anatomy Finals Very Good Vacations Are Heavenly. Some Say Marry Money, But My Brother Says Big Business Makes Money. Carl Only Swims South. Silly Roger Only Swims In Infiniti Jacuzzis. Jane Just Hitchhikes. To Zanzibar By Motor Car* [ 5 Branches of Facial Nerve ]

21. Useful Websites & Resources Yale University: http://www.yale.edu/cnerves/http://www.yale.edu/cnerves/ fastbleep: http://www.fastbleep.com/medical-notes/neuro- and-psych/2/95/610http://www.fastbleep.com/medical-notes/neuro- and-psych/2/95/610 UBC (University of British Colombia): http://www.neuroanatomy.ca/ http://www.neuroanatomy.ca/ TeachMeAnatomy: www.teachmeanatomy.co.ukwww.teachmeanatomy.co.uk Mnemonics: file:///S:/Downloads/List%20of%20mnemonics%20for%20the %20cranial%20nerves.pdf file:///S:/Downloads/List%20of%20mnemonics%20for%20the %20cranial%20nerves.pdf

22. References Mike Mahon – Cranial Nerve Neuroanatomy Lecture Neuroanatomy Illustrated Gray’s Anatomy for Students Bear’s Neuroscience Cranial Nerve Neuroanatomy Image 1 - http://d7c2b0wpljtwf.cloudfront.net/var/ezwebin_site/storage/images/media/ima ges/e-anatomy/cranial-nerves-anatomy-diagrams/skull-cranial-base-foramen- cranial-nerves-anatomy-en/2571278-1-eng-GB/skull-cranial-base-foramen-cranial- nerves-anatomy-en_imagelarge.jpg "Brain human normal inferior view with labels en-2" by Brain_human_normal_inferior_view_with_labels_en.svg: *Brain_human_normal_inferior_view.svg: Patrick J. Lynch, medical illustratorderivative work: Beaoderivative work: Dwstultz (talk) - Brain_human_normal_inferior_view_with_labels_en.svg. Licensed under CC BY 2.5 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Brain_human_normal_inferior_view_wit h_labels_en- 2.svg#mediaviewer/File:Brain_human_normal_inferior_view_with_labels_en-2.svg