Cranial Nerves Flashcards
What is the pathway of the olfactory nerve?
Receptors in olfactory epithelium, fibres pass through foraminifera in cribriform plate of ethmoid bone and enter olfactory bulb in anterior cranial fossa
What are the components of the olfactory nerve?
Special sensory - smell
What are clinical applications of the olfactory nerve?
Fractured cribriform plate may tear olfactory nerve fibres causing anosmia
What is the pathway of the optic nerve?
Enters via optic canal, nerves join to form optic chiasm
Fibres from medial half of each retina cross to form optic tract
What are the components of the optic nerve?
Special sensory - vision
What are the clinical applications of the optic nerve?
Increase in CSF pressure can cause papilloedema
Section of right optic nerve causes blindness through right eye
Section of optic chiasm causes loss of peripheral vision
Section of right optic tract causes blindness in left temporal and right nasal fields
What is the pathway of the oculomotor nerve?
Emerges from midbrain and exits via superior orbital fissure
What are the components of the oculomotor nerve?
Somatic motor - extraocular muscles
Visceral motor - parasympathetic to pupil causing constriction and to ciliary muscle causing accommodation of lens
What are the clinical applications of the oculomotor nerve?
Drooping of upper eyelid (ptosis)
Eyeball abducted and pointing down
No pupillary reflex
No accommodation of lens
What is the pathway of the trochlear nerve?
Emerges from dorsal surface of mid brain and exits via superior orbital fissure
What are the components of the trochlear nerve?
Somatic motor - superior oblique muscle
What are the clinical applications of the trochlear nerve?
Diplopia when looking down
What is the pathway of the opthalmic branch of the trigeminal nerve?
Emerges from pons, travels through trigeminal ganglion and exits via superior orbital fissure
What are the components of the opthalmic branch of the trigeminal nerve?
General sensory - from cornea, forehead, scalp, eyelids, nose and mucosa of nasal cavity and sinuses
What are the clinical applications of the opthalmic branch of the trigeminal nerve?
Loss of corneal or sneezing reflex
Trigeminal neuralgia - gentle touch becomes painful or there is constant pain
What is the pathway of the maxillary branch of the trigeminal nerve?
Emerges from the pons, travels through trigeminal ganglion and exits via foramen rotunda
What are the components of the maxillary branch of the trigeminal nerve?
General sensory - from face over maxilla, maxillary teeth, TMJ, mucosa of nose, maxillary sinus and palate
What are the clinical applications of the maxillary branch of trigeminal nerve?
Loss of sensation in face
Trigeminal neuralgia
What is the pathway of the mandibular branch of the trigeminal nerve?
Emerges from pons, travels through trigeminal ganglion and exits via foramen ovale
What are the components of the mandibular branch of the trigeminal nerve?
General sensory - from face over mandible, mandibular teeth, TMJ joint, mucosa of mouth and 2/3rds of tongue
Somatic motor - muscles of mastication, part of digastric, tensor veil palatine and tensor tympani
What are the clinical applications of the mandibular branch of the trigeminal nerve?
Paralysis of muscles of mastication
Trigeminal neuralgia
What is the pathway of the abducens nerve?
Emerges between pons and medulla and exits via superior orbital fissure
What are the components of the abducens nerve?
Somatic motor - lateral rectus muscle
What are the clinical applications of the abducens nerve?
Medial deviation of affected eye causing diplopia
What is the pathway of the facial nerve?
Emerges between pons and medulla and exits via internal acoustic meatus, facial canal and stylomastoid foramen
What are the components of the facial nerve?
Somatic motor - muscles of facial expression and scalp, stapedius of middle ear, part of digastric muscle
Visceral motor - parasympathetic innervation of submandibular and sublingual salivary glands, lacrimal glands, glands of nose and palate
Special sensory - taste from anterior 2/3rds of tongue and soft palate
General sensory - external acoustic meatus
What are the clinical applications of the facial nerve?
Most frequently injured due to long pathway through bone
Bells palsy - can’t frown, close eyelid or bare teeth
What is the pathway of the vestibulocochlear nerve?
Emerges from between pons and medulla and exits via internal acoustic meatus
What are the components of the vestibulocochlear nerve?
Special sensory - vestibular sensation from semicircular ducts, utricle, saccule gives sense of position and movement
Hearing from spiral organ
What are the clinical applications of the vestibulocochlear nerve?
Tinnitus
Deafness
Vertigo
Nystagmus
What is the pathway of the glossopharyngeal nerve?
Emerges from medulla and exits via jugular foramen
What are the components of the glossopharyngeal nerve?
Special sensory - taste from posterior 1/3rd of tongue
General sensory - cutaneous sensation from middle ear and posterior oral cavity
Visceral sensory - sensation from carotid body & carotid sinus
Visceral motor - parasympathetic innervation of parotid gland
Somatic motor - to stylopharyngess, helps with swallowing
What are the clinical applications of the glossopharyngeal nerve?
Loss of gag reflex
Associated with injuries to CNs X and XI - jugular foramen syndrome
What is the pathway of the vagus nerve?
Emerges from medulla and exits via jugular foramen
What are the components of the vagus nerve?
Special sensory - taste from epiglottis and palate
General sensory - sensation from auricle, external acoustic meatus
Visceral sensory - pharynx, larynx, trachea, bronchi, heart, oesophagus, stomach
Visceral motor - parasympathetic innervation muscle in bronchi, gut, heart
Somatic motor - pharynx, palate and oesopahgus
What are the clinical applications of the vagus nerve?
Damage to pharyngeal branches cause difficulty in swallowing
Damage to laryngeal branches causes difficulty in speaking
Prominent notice of damage is to somatic motor component
What is the pathway of the accessory nerve?
Small cranial and large spinal roots exit via jugular foramen
What are the components of the accessory nerve?
Somatic motor - striated muscle of soft palate, pharynx and larynx and to sternocleidomastoid and trapezius
What are the clinical applications of the accessory nerve?
Weakness in turning head and shrugging shoulders
What is the pathway of the hypoglossal nerve?
Emerges from medulla and exits through the hypoglossal canal
What are the components of the hypoglossal nerve?
Somatic motor - to muscles of tongue
What are the clinical applications of the hypoglossal nerve?
Vulnerable to damage during tonsillectomy
Causes paralysis and atrophy of ipsilateral half of tongue - tip deviates towards affected side
