Cranial Nerves Flashcards
How many pairs of cranial nerves are there?
12
What are cranial nerves prone to compression due to?
Inflammation, tumours or fractures
What do the symptoms due to problems with cranial nerves relate to?
The function of the nerves
What are the different kinds of fibres that cranial nerves may contain?
Somatic motor fibres (supply striated muscle)
Visceral motor fibres (cranial division of the parasympathetic supply innervates smooth muscles and glands)
Visceral sensory (afferent inputs from pharynx, larynx, heart, lungs, gut etc)
General sensory (afferent input from skin and mucous membranes)
Special sensory (taste, smell, vision, hearing and balance)
Are the cell bodies of sensory (afferent) fibres inside or outside of the CNS?
Outside
Are the cell bodies of somatic motor fibres inside or outside of the CNS?
Inside
Are the cell bodies of autonomic motor fibres inside or outside of the CNS?
Inside and outside
What are each of the cranial nerves called?
Olfactory (CN I)
Optic (CN II)
Oculomotor (CN III)
Trochlear (CN IV)
Trigeminal (CN V)
Abducent (CN VI)
Facial (CN VII)
Vestibulocochlear (CN VIII)
Glossopharyngeal (CN IX)
Vagus (CN X)
Accessory (CN XI)
Hypoglossal (CN XII)
What kind of fibres does the olfractory nerve carry?
Special sensory (smell)
What kind of fibres does the optic nerve carry?
Special sensory (vision)
What kind of fibres does the oculomotor nerve carry?
Somatic motor (extraocular muscles, superior, medial, inferior rectus and inferior oblique and eye lid - levator palpebrae superioris)
Visceral motor (parasympathetic to pupil causing contriction and to ciliary muscle causing accomodation of the lens)
What kind of fibres does the trochlear nerve carry?
Motor (eye movements)
What kind of fibres does the trigeminal nerve carry?
Mixed (sensation from face and mouth, controls muscles of mastication so sensory and motor)
What kind of fibres does the abducent nerve carry?
Motor (eye movement)
What kind of fibres does the facial nerve carry?
Mixed (muscles of facial expression, parasympathetic, taste)
What kind of fibres does the vestibulocochlear nerve carry?
Special sensory (hearing and balance)
What kind of fibres does the glossopharyngeal nerve carry?
Mixed (swallowing, sensation from tongue, parasympathetic)
What kind of fibres does the vagus nerve carry?
Mixed (muscles of the throat, parasympathetic, visceral sensory)
What kind of fibres does the accessory nerve carry?
Motor (soft palate, throat and neck)
What kind of fibres does the hypoglossal nerve carry?
Motor (tongue)
Where is the receptor for the olfractory nerve?
Olfactory epithelium of nasal cavity
What route does the olfactory nerve take?
Passes through foraminifera in cribiform plate of ethmoid bone and enters olfactory bulk in the anterior cranial fossa
Fracture of what can tear the olfactory nerve and cause anosmia (loss of smell)?
Cribiform plate
What is the pathway of the optic nerve?
1) Enters via optic canal
2) Nerve join to form optic chiasm
3) Fibres from medial (nasal) half of each retina cross to form optic tract
What does a secetion of right optic nerve cause?
Blindness through right eye
What does a section of optic chiasm cause?
Loss of periphery vision (bitemporal hemianopsia)
What does a section of right optic nerve cause?
Blindess in left temporal and right nasal fibres (left homonymous hemianopsia)
In relation to the optic nerve, what can an increase in CSF pressure cause?
Papiloedema (optic nerve swells)
What is the pathway of the oculomotor nerve?
What are clinical applications of oculomotor damage?
Drooping of upper eyelid
Eye abducted and pointing down
No pupillary reflex
No accomodation of the lens
What muscles does the oculomotor nerve supply?
Extraocular muscles
Superior, medial, inferior rectus
Inferior oblique
Levator palpebrae superioris
What impact does the oculomotor nerve have on the pupil and lens of the eye?
Pupil constriction
Accomodation of the lens
What is the pathway of the trochlear nerve?
Emerges from dorsal surface of the midbrain and exits via the superior orbital fissure
What is a clinical application of trochlear nerve damage?
Diplopia when looking down (double vision)
What is the medical term for double vision?
Diplopia
What is the pathway of the abducent nerve?
Emerges between pons and medulla and exits via the superior orbital fissure
What is the clinical application of abducent damage?
Medial deviation of the affecting eye causing diplopia
What are the 3 branches of the trigeminal nerve?
Opthalmic branch (V1)
Maxillary branch (V2)
Mandibular branch (V3)
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 is the pathway of the maxillary branch of the trigeminal nerve?
Emerges from the pons
Travels through the trigeminal ganglion and exits the foramen rotundum
What are the components of the maxillary branch of the trigeminal nerve?
General sensory (from face over maxillar, maxillary teeth, temporomandibular joint, mucosa of nose, maxillary sinuses and palate)
What are the components of the mandibular branch of the trigeminal nerve? <3
General sensory (from face over mandibular teeth, tempromendibular joint, mucosa of mouth and anterior 2/3rds of tongue
Somatic motor (muscles of mastication, part of digastric, tensor veli palatinin and tensor tympani)
What are clinical applications of damage to the mandibular branch of the trigeminal nerve?
Paralysis of muscles of mastication
Loss of corneal or sneezing reflex
Loss of sensation to the face
Trigeminal neualgia (chronic pain that affects the trigeminal nerve)
What is the pathway of the facial nerve?
Emerges between pons and medulla
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 galivary glands, lacrimal glands, glands of nose and palate)
Special sensory (taste from anterior 2/3rds of tongue and soft palate
General sensory (from external acoustic meatus)
What are clinical applications for damage to the facial nerve?
Bell’s palsy
What are signs of Bell’s palsy?
Cannot frown, close eyelids or bare teeth
What cranial nerve is most frequently injured and why?
Facial nerve due to long pathway through bone
What is the pathway of the vestibulocochlear nerve?
Emerges from between pons and medulla
Exits via internal acoustic meatus, dividing into vestibular and cochlear nerves
What are the components of the vestibulocochlear nerve?
Special sensory (vestibular sensation from semicircular ducts, utricle, saccule gives sense of position and movement, and hearing from spiral organ)
What are clinical applications for damage to the vestibulocochlear nerve?
Tinnitus (ringing in ears)
Deafness (conductive vs sensorineural)
Vertigo (loss of balance)
Nystagmus (involuntary rapid movements of the eyes)
What is the medical term for ringing in the ears?
Tinnitus
What is the pathway of the glossopharyngeal nerve?
Emerges from medulla
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 and carotid sinus)
Visceral motor (parasympathetic innervation of parotid gland)
Somatic motor (to sylopharyngeus, helps with swallowing)
What are clinical applications for damage to the glossopharyngeal nerve?
Loss of gag refle and taste from back of tongue
Associated with injuries to CN X and CN XI, known as jugular foramen syndrome
What is the pathway of the vagus nerve?
Emerges from medullar
Exits via jugular foramen then basically everywhere
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 (from pharynx, larynx, trachea, bronchi, heart, oesophagus, stomach, intestine)
Visceral motor (parasympathetic innervation muscle in bronchi, gut, heart)
Somatic motor (to pharynx, palate, larynx and oesophagus)
What are clinical applications to damage of the vagus nerve?
Damage to pharyngeal branches cause difficulty swallowing
Damage to laryngeal branches causes difficulty speaking
What is the pathway of the accessory nerve?
Small cranial (medulla) and large spinal roots exits via jugular foramen
What are components of the accessory nerve?
Somatic motor (striated muscle of soft palate, pharynx and larynx, and to sternocleidomastoid and trapezius)
What are clinical applications of damage to the accessory nerve?
Weakness in turning head and shrugging shoulder
What is the pathway of the hypoglossal nerve?
Energes from medulla
Exits through the hypoglossal canal
What are the components of the hypoglossal nerve?
Somatic motor (to muscles of tongue)
What are clinical applications for damage to the hypoglossal nerve?
Vulnerable to damage during tonsillectomy
Causes paralysis and atrophy of ipsilateral half of tongue, so tip deviates towards affected side
