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Cranial Nerves https://teachmeanatomy.info/head/cranial-nerves/summary/Tuesday 14th December Tuesday 7 December Wednesday 8 December th Friday 17 December st Tuesday 2 December• I – Olfactory Sensory Some Say • II – Optic Sensory • III – Oculomotor Motor Money • IV – Trochlear Motor Matters But • V – Trigeminal Both • VI – Abducent Motor My • VII – Facial Both Brother • VIII – Vestibulocochlear Sensory Says • IX – Glossopharyngeal Both Big • X – Vagus Both Brains • XI – Spinal accessory Motor Matter More • XII - Hypoglossal Motor CN I - Olfactory Pathway: 1. Receptors are located in the nasal mucosa Function – Sense of smell 2. Olfactory axons enter skull through cribriform plate 3. Olfactory neurons terminate in the olfactory bulb 4. 2° neurons pass through olfactory tract and olfactory stria 5. The fibers terminate in the primary olfactory cortex Examination: • Ask if they have noticed any Relevant pathology: changes in their sense of smell • Temporary anosm –iaOVID-19, meningitis, other infection • Ask the patient to identify a • Permanent anosmia– Brain tumour, trauma smell one nostril at a time • Progressive anosmia– Parkinson’s, Alzheimer's CN II - Optic Function – Vision Pathway: 1. Axons from retinal ganglion cells converge to form optic nerve 2. This passes through the optic canal into cranial cavity 3. Nerves converge at the optic chiasm 4. Medial fibers decussate and lateral fibers remain ipsilateral 5. Fibers enter optic tract and terminate in the lateral geniculate nucleus 6. Fibers pass through optic radiation and terminate in the visual cortex Examination: • Ask if they’ve noticed any changes in their vision • Light reflex • Accommodation reflex • Visual fields • Snellen chart • Color vision • Ophthalmoscopy https://commons.wikimedia.org/wiki/File:Neural_pathway_diagram.svghttps://geekymedics.com/visual-pathway-and-visual-field-defects/ CN III - Oculomotor Function: Pathway: • Motor – superior, medial, and 1. Originates from the oculomotor nucleus in the midbrain inferior rectus, inferior oblique, 2. Emerges from the anterior midbrain, inferior to the posterior cerebral artery and superior to the superior cerebellar artery levator palpabrae superioris 3. Pierces the dura mater • Parasympathetic– sphincter pupillae and ciliary muscles 4. Enters the cavernous sinus 5. Exits the cranial cavity via the superior orbital fissure 6. Divides into superior and inferior branch Examination: • Ask if they’ve noticed any Relevant pathology: changes to their vision Oculomotor nerve palsy. Common causes include; • Light reflex • Raised ICP • Accommodation reflex • Posterior communicating artery aneurysm • H test • Myasthenia gravis and MS • Cavernous sinus infection CN IV – Trochlear Pathway: Function: 1. Arises from the dorsal surface of the midbrain Motor innervation to the superior 2. Passes anteriorly around the brainstem and runs in the subarachnoid oblique space 3. Pierces the dura mater at the margin of the tentorium cerebelli 4. Runs along the lateral wall of the cavernous sinus 5. Enters the orbit through the superior orbital fissure Examination: Key point– Although the muscle attaches to the superior surface of the • Ask if they’ve had any double vision recently sclera, it acts to depress and intort the eyeball due to it passing through • Inverted V test/H test the trochlea and changing direction Relevant pathology.– Trochlear nerve palsy can result in vertical diplopia and a head tilt away from the affected side CN VI– Abducens Pathway: Function: Motor innervation to the lateral 1. Arises from the brainstem at the pons-medullary junction rectus 2. Transverses the pontine cistern of the subarachnoid space 3. Pierces the dura mater to enter theDorello’s canal 4. Enters cavernous sinus 5. Enters bony orbit through the superior orbital fissure Abducens nerve palsy: Examination: H test • Symptoms are failure of eye abduction and diplopia • The most common/first nerve to be affected by raised ICP due to its long course through the brainAll eye tests combined • double visionnt if they have noticed any changes to their vision or • Light reflex • Accommodation reflex • Visual fields • Snellen chart • Colour vision • H test • Ophthalmoscopyhttps://www.seevividly.com/info/Physiology_of_Vision/The_Brain/Visual_System/Eye_Muscles https://medschool.co/signs/limitation-of-extraocular-movementLesions to CN III, IV , and VI: CN V – Trigeminal Pathway: Function: 1. At the pons the sensory nuclei merge to form the sensory root, and • Sensory – skin, mucous membranes, and sinuses of the the motor nucleus forms a motor root face 2. In the MCF the sensory root expands into the trigeminal ganglion • Motor – Muscles of mastication 3. The three divisions of the nerve arise from the ganglion V1 – Travels in lateral cavernous sinus and exits through superior orbital fissure Examination: V2 – Travels in lateral cavernous sinus and exits through foramen rotundum V3 – Exits through foramenovale and enters infratemporal fossa Test sensation to 3 areas of the face Muscles of mastication – Open jaw to check for mandibular deviation, Relevant pathology: clench teeth while feeling masseter • AFFERENT limb of the corneal reflex and temporalis • Trigeminal neuralg– iacauses pain across the distribution of the nerveOphthalmic Maxillary Mandibular Nasociliary Nasopalatine Mental Lacrimal Greater palatine Masseteric Frontal Infraorbital Nerve to mylohyoid Posterior superior alveolar Lingual Middle superior alveolar Incisive Anterior superior alveolar Buccal Zygomatic Nerve to medial pterygoid Lesser palatine Meningeal Auricotemporal Inferior alveolar Deep temporal CN VII - Facial Function: Pathway: • Motor – Muscles of facial expression 1. Arises form at the pons-medullary junction • Sensory – taste to anterior 2/3 of 2. Enter petrous temporal bone through internal auditory meatus tongue, external ear 3. Enters facial canal where the roots combine, and swells to • Parasympathetic– nasal glands, form the geniculate ganglion lacrimal gland, submandibular & 4. Exits the skull through the stylomastoid foramen sublingual salivary glands 5. Gives off motor branches to the stylohyoid and posterior belly of digastric 6. Enters parotid gland and terminates into 5 branches Examination: • Muscles of facial expression – purse lips, scrunch eyes, raise eyebrows etc • Taste to anterior 2/3rds of tongue Relevant pathology: • Ask if noises have been louder than normal recently • UMN lesion will spare the muscles of the upper face • Ask if they have had dry eyes or a dry • LMN lesion will cause paralysis of all muscles of one side of the mouth face CN VIII – Vestibulocochlear Pathway: Function: 1. Vestibular component arises from the p -onedullary junction Hearing – via the organ of Corti 2. Cochlear component arises from the inferior cerebellar peduncle Balance – via the otolith organs and 3. Componants combine to for the vestibulocochlear nerve the semicircular canals 4. Emerges from the brain at the cerebellopontine angle 5. Exits cranium via the internal acoustic meatus 6. Separates back into the vestibular and cochlear nerves 7. Vestibular nerve extends to tut icule, saccule, and semi-circular canals 8. Cochlear nerve extends to the spiral organ of corti Examination: • Ask if they’ve had any problems with their hearing and balance Relevant pathology: • Weber and Rinne's test • Commonly injured during a basilar skull fracture • Audiogram • Vestibular neuriti due to inflammation of the vestibular branch • Labyrinthitis – inflammation of the membranous labyrinth causes damage to both branches CN IX – Glossopharyngeal Function: • Sensory – Oropharynx, carotid body and Pathway: 1. Arises from lateral medulla between the olive and inferior sinus, posterior 1/3 of tongue, middle ear cerebellar peduncle cavity, Eustachian tube 2. Passes through posterior cranial fossa • Parasympathetic– innervation to parotid 3. Exits cranium through jugular foramen gland • Motor – stylopharyngeus muscle of the 4. Descends down the neck anterolateral to the ICA 5. Passes stylopharyngeus and gives off several branches pharynx 6. Passes between the superior and middle pharyngeal constrictors to enter the pharynx Examination: • Ask if they have had a dry mouth Responsible for the AFFERENT limb of the gag reflex • Test taste of the posterior 1/3 of tongue CN X – Vagus Pathway: 1. Arises form lateral medulla Sensory 2. Passes through the posterior cranial fossa • External acoustic meatus • Laryngopharynx and larynx 3. Exits skull through jugular foramen • Visceral sensation to the heart and abdominal 4. Passes through the neck in the carotid sheath viscera 5. Enters the thorax and passes through the mediastinum Motor 6. Enters abdomen through theoesophageal • Muscles of the soft palate except tensorvelipalatini • Muscles of the pharynx except the stylopharyngeus hiatus • Muscles of the larynx Parasympathetic • Innervates smooth muscle of the trachea, bronchi, GI tract Examination : • Regulates heart rhythm Check the soft palate and uvula Hoarse voice and bovine cough CN XI – Spinal accessory Pathway: 1. Spinal portion passes through foramen magnum to enter cranial Function: cavity Innervates the sternocleidomastoid 2. Cranial portion arises from the lateral medulla oblongata and trapezius muscles 3. Spinal and cranial roots briefly unite and leave through the jugular foramen 4. Spinal portion descends along internal carotid artery, pierces sternocleidomastoid, and supplies fibers to the trapezius 5. Cranial portion combines with vagusnerve Examination: Ask the patient to shrug their shoulders and rotate their head, Relevant pathology: both independently and against Accessory nerve palsy is most commonly iatrogenic, due to procedures resistance such as cervical lymph node excision CN XII - Hypoglossal Pathway: 1. Arises from the medulla between the pyramid and olive Function: Innervates all of the muscles of the 2. Crosses the posterior cranial fossa tongue except the palatoglossus 3. Exits cranium via the hypoglossal canal 4. Contributes to the Ansa cervicalis in the neck 5. Descends medial to the angle of the mandible and turns forwards 6. Passes between mylohyoid and hyoglossus muscle 7. Enters the tongue Examination: • Ask the patient to stick their tongue out Relevant pathology: • Ask them to press their tongue A hypoglossal nerve palsy will cause tongue deviation TOWARDS the against their cheek damaged sidePassmedicine.comPharyngeal Arches Arch 1 Trigeminal Arch 2 Facial Arch 3 Glossopharyngeal Arch 4 Superior laryngeal branch of the vagus Arch 6 Recurrent laryngeal branch of theagus Osmosis.orgKahoot QuizThank you for listening Does anyone have any questions? Ella.Snowdon@student.manchester.ac.uk