CRANIAL NERVES ANATOMY

1. 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, motorand/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 - 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- 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: • V1 [opthalmic]- Superior Orbital Fissure • V2 [maxillary]- Foramen Rotundum • V3 [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. SENSORY MOTOR PARASYMPATHETIC EFFERENTS Temporal Zygomatic Buccal Maxillary 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- special afferent

14. Cranial Nerve IX:Glossopharyngeal • FORAMEN – Jugular Foramen • Sensory – input from the carotid body and sinus (detects changes in PCO2 and pressure). Taste in posterior 1/3 of tongue. • Motor – controls stylopharyngeal muscle for swallowing. • Parasympathetic efferent - innervates parotid salivary gland SENSORY MOTOR 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 visceraupto the midgut. (2/3 of Transverse Colon) SENSORY 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 – 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* *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/ • fastbleep: http://www.fastbleep.com/medical-notes/neuro-and-psych/2/95/610 • UBC (University of British Colombia): http://www.neuroanatomy.ca/ • TeachMeAnatomy: www.teachmeanatomy.co.uk • Mnemonics: 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/images/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_with_labels_en-2.svg#mediaviewer/File:Brain_human_normal_inferior_view_with_labels_en-2.svg