Cranial Nerves PDF

Cranial Nerves Gulshana Choudhury Module: Oral and Dental Sciences GDC Learning Outcomes 1.1.5 Describe relevant and appropriate dental, oral, craniofacial and general anatomy and explain their application to patient management Intended Learning Outcomes By the end of the session students shou...

Cranial Nerves Gulshana Choudhury Module: Oral and Dental Sciences GDC Learning Outcomes 1.1.5 Describe relevant and appropriate dental, oral, craniofacial and general anatomy and explain their application to patient management Intended Learning Outcomes By the end of the session students should be able to: List the 12 paired cranial nerves Describe the functions of each nerve Outline the anatomical regions they supply Explain the relevance of each nerve to dentistry as applicable Why do I need to know this?  Acland's Video Atlas of Human Anatomy Resources Anatomy.tv Teach me Anatomy Lecture Outline Overview of Function and Summary Cranial clinical and Quiz Nerves relevance What are the Cranial Nerves? 12 paired nerves that arise directly from the brain The first two nerves (olfactory and optic) arise from the cerebrum The remaining ten emerge from the brain stem. The names of the cranial nerves relate to their function and they are also numerically identified in roman numerals (I-XII). Base of skull showing foramina Revision: Sensory and Motor nerves!  General somatic sensory (GSS) – general sensation from skin. Sensory General visceral sensory (GVS) – general sensation from viscera. (afferent) Special somatic sensory (SSS) – senses derived from ectoderm (e.g. sight, sound, balance). Modalities Special visceral sensory (SVS) – senses derived from endoderm (e.g. taste, smell). General somatic motor (GSM) – skeletal muscles. Motor General visceral motor (GVM) – smooth muscles of (efferent) gut and autonomic motor. Special visceral motor (SVM) – muscles derived Modalities from pharyngeal arches. The Cranial Nerves I = Olfactory (sensory) VII = Facial (mixed) II = Optic (sensory) VIII = Vestibulocochlear (sensory) III = Oculomotor (motor) IX = Glossopharyngeal (mixed) IV = Trochlear (motor) X = Vagus (mixed) V = Trigeminal (mixed) XI = Accessory (motor) VI = Abducens (motor) XII = Hypoglossal (motor) How to remember the cranial nerves! Cranial Nerve I - Olfactory Sensory nerve Sensory receptors originate in olfactory epithelium of the nasal cavity Nerve fibres pass through the cribriform plate of the ethmoid bone from the roof of the nasal fossa Pass into the olfactory bulb Function: Sense of smell Damage to Olfactory nerve Total loss of smell Impaired or distorted smell Abnormal taste perception Causes Trauma Tumour Cranial Nerve II - Optic Sensory nerve Fibres originate in retinae of eye and combine to form optic nerve The two optic nerves join at the optic chiasma Function: Vision Damage to Optic nerve Loss of vision depends on where nerve is damaged Blindness in one eye Loss of lateral vision in both eyes Loss of one half of the visual field in both eyes Olfactory and optic nerves (cranial nerves I, II) | Acland's Video Atlas of Human Anatomy Cranial Nerve III - Oculomotor Motor nerve Travels with some parasympathetic fibres to ciliary ganglion Divides into superior and inferior branches Enter orbit through superior orbital fissure of sphenoid  Cranial Nerve III - Oculomotor Eye Supplies four of the six extra-ocular muscles of the eye movements (superior, medial and inferior rectus muscles and inferior oblique muscle) Upper eyelid Supplies the levator palpebrae superioris muscle of the movement upper eyelid Intrinsic Parasympathetic ciliary fibres supply the constrictor eyeball pupillae and ciliary muscles to constrict the pupil & make muscles lens more spherical (short range vision) Damage to oculomotor nerve Clinical Relevance: Oculomotor Nerve Palsy Dropping eyelid (ptosis) Eye moves down and out Medial and upward eye movements impaired The patient is unable to elevate, depress or adduct the eye. Pupil dilated Cranial Nerve IV - Trochlear Motor nerve Arises near junction of midbrain with pons Enters orbit through superior orbital fissure Supplies superior oblique muscle Damage to trochlear nerve Not as noticeable as for damage to oculomotor or abducens nerve Eyeball deviates upwards Double vision Head tilt to compensate Cranial Nerve V - Trigeminal This will be covered in a separate lecture! Cranial Nerve VI - Abducens Motor nerve Arises from abducens nucleus in the pons Enters orbit through superior orbital fissure Supplies lateral rectus muscle of eye Damage to Abducens nerve Affected eye deviates medially Lateral gaze deficit Double vision  Oculomotor, abducent, and trochlear nerves (III, VI, VII) in the cranium | Acland's Video Atlas of Human Anatomy Cranial Nerve VII - Facial This will be covered in a separate lecture! Cranial Nerve VIII - Vestibulocochlear Sensory nerve Also known as Auditory nerve Two divisions, vestibular and cochlear nerves Pass through internal auditory meatus to the medulla oblongata of brainstem Function: special senses of hearing (via the cochlear nerve), and balance (via the vestibular nerve) Damage to Vestibulocochlear nerve Clinical Relevance: Vestibular Neuritis Inflammation of the vestibular branch of the vestibulocochlear nerve Aetiology not fully understood - ?reactivation of the herpes simplex virus. Symptoms: Vertigo – a false sensation that oneself or the surroundings are spinning or moving. Nystagmus – a repetitive, involuntary to-and-fro oscillation of the eyes. Loss of equilibrium (especially in low light). Nausea and vomiting Damage to Vestibulocochlear nerve Clinical Relevance: Labyrinthitis Refers to inflammation of the membranous labyrinth, resulting in damage to the vestibular and cochlear branches of the vestibulocochlear nerve. The symptoms are similar to vestibular neuritis, but also include indicators of cochlear nerve damage: Sensorineural hearing loss The components of the membranous labyrinth. Tinnitus – a false ringing or buzzing sound. Facial and vestibulo-cochlear nerves (cranial nerves VII, VIII) | Acland's Video Atlas of Human Anatomy Cranial Nerve IX - Glossopharyngeal Motor and Sensory Motor fibres arise in medulla oblongata Leaves skull through jugular foramen Several sensory branches and a motor branch  Cranial Nerve IX - Glossopharyngeal Sensory Special sensory Parasympathetic Motor Mucosa of oropharynx Taste to posterior 1/3 Parotid gland Stylopharygeus Posterior 1/3 tongue tongue (secretomotor) muscle of the pharynx Middle ear cavity Damage to Glossopharyngeal nerve Clinical Relevance: Glossopharyngeal neuralgia Relatively rare, 1 in 100,000 Sharp, stabbing pulses of pain in the back of the throat and tongue, the tonsils, and the middle ear Some loss of taste Loss of gag reflex Impaired swallowing Dry mouth due to impairment of parotid gland Causes Neurovascular compression of the nerve Trauma, surgery, infection, tumour Cranial nerve X – Vagus Sensory and Motor Motor fibres arise from the medulla Arises with nerves IX & XI Exits skull through jugular foramen Cranial nerve X – Vagus Motor Sensory Parasympathetic Special Sensory Intrinsic muscles of Skin at back of ear & Innervates smooth Minor role in taste sensation from root of larynx and pharynx, external auditory muscle of the trachea, the tongue and soft palate & striated meatus, mucous bronchi, abdominal epiglottis muscles of upper membrane of epiglottis, organs and gastro- oesophagus lower pharynx & larynx intestinal trac Gustatory afferents from taste buds around epiglottis Parasympathetic to smooth muscle & glands Visceral afferents from respiratory tract & GI tract Innervates heart (cardiac inhibition) Damage to vagus nerve Deviation of uvula away from side of damage Hoarse voice Trouble drinking liquids Loss of the gag reflex Pain in the ear Abnormal blood pressure Nausea, vomiting, abdominal bloating & pain Cranial Nerve XI - Accessory Spinal & cranial components Spinal arises from 5 – 6 most cranial segments of spinal cord & enters cranial cavity through foramen magnum Joins cranial part and emerges through jugular foramen Motor nerve - to trapezius muscle & sternocleidomastoid muscle (spinal part) & muscles of soft palate (cranial part) Cranial part joins the Vagus nerve (X) 44 Sternocleidomastoid and trapezius muscles Damage to accessory nerve Shoulder pain and weakness Limited upper arm movement Asymmetrical shoulder Cranial Nerve XII - Hypoglossal Arises from medulla oblongata Leaves cranial cavity via hypoglossal canal Motor – to intrinsic & extrinsic muscles of tongue (except palatoglossus) Essential for eating, speaking, swallowing Damage to hypoglossal nerve Wasting of tongue on affected side Deviation of tongue to affected side Difficulties eating, speaking, swallowing Summary 12 pairs of cranial nerve Outlined origin, function and relevance Facial nerve (VII) and Trigeminal nerve (V) most relevant to dentistry and outlined in separate lectures https://app.sli.do/event/eMjuTg5FxejUjd1MYszb3y References https://www.youtube.com/watch?v=GJBnwZQ60Ss – Cranial nerves basics https://teachmeanatomy.info/head/cranial-nerves/summary/ https://www.anatomy.tv/titles https://aclandanatomy.com/ Norton, N.S. and Netter, F.H. (2017) Netter's head and neck anatomy for Dentistry. Elsevier (Chapter 3 and 20) Liebgott, B. (2018) The anatomical basis of Dentistry. PHILADELPHIA (U.A.): SAUNDERS.