Cranial Nerves Flashcards
What are the Cranial Nerves
- Olfactory
- optic
- oculumotor
- trochlear
- trigeminal
- Abducens
- fascial
- Vestibulocochlear
- Glossalpharyngeal
- vagus
- accessory
- hypoglosssa
What nerves are sensory and what nerves are motor?
- Olfactory - S
- optic - S
- oculumotor -M
- trochlear-M
- trigeminal-B
- Abducens -M
- fascial-B
- Vestibulocochlear - S
- Glossalpharyngeal - B
- vagus -B
- accessory - M
- hypoglosssa - M
Olfactory Nerve
- sensory only
- olfaction/smell
- only sensory input that can reach cortex without synapses in cortex
- olfactory bulb => medial temporal lobe of cerebrum and olfactory cortex in insule => amygdala and parahippocampal gyrus
Optic nerve
- sensory only
- vision
oculomotor
- motor
- serves muscles of the eye
trochlear
Motor
serves superior oblique eye muscle
trigeminal
- Motor and sensory
- sensory from face and mouth
- motor to muscles of mastication
- function in chewing, fascial sensation, sensation from TMJ and teeth, afferent limb of corneal reflex
Abducens
- motor
- serves the lateral rectus eye muscle
CN6
fascial
- motor and sensory
- serves the muscles of fascial expression, lacrimal glands and salivary glands
Vestibulocochlear
- Sensory
- equilibrium and hearing
Glossopharyngeal
- motor and sensory
- serves the pharynx for swallowing
- posterior third of tongue, parotid salivary gland
vagus
- motor and sensory
- sensation from visceral (internal organs)
- parasympathetic motor regulation of visceral organs
accessory
- motor
- serves muscles the move head, neck and shoudle
hypoglosssa
- motor
- serves muscles of the tongue
What occurs with damage to Olfactory and how to test it
- loss of sense of smell = Aanosmia
- test = pungent smells such as coffee, vanila
- close one nostril to test each nerve
What are the three divisions of the trigeminal nerve
V1 = opthalmic branch
V2 = maxillary branch
V3 = mandibular branch
What are the motor connections of the trigeminal nerve
- trigeminal motor nucleus is in pons
- receives bilateral connections from corticobrainstem tract (upper)
- innervates muscles for mastication
- motor axons travel in mandibular branch
- also innervate: tensor tympani, mylohyoid, tensor palatini, diagastric ms
What are the three trigeminal sensory nuclei
Primary/main sensory:
- first order neurons synapse here, light touch and pressure
Mesencephalic nucleus (midbrain)
- proprioceptive info from mm’s of mastication
- transmitted ipsilaterally by axons of CN-V to here
- reticular formation in midbrain
Spinal trigeminal nucleus
- neurons for pain and temperature synapse here (pons/medullar)
How to test the trigeminal nerve
- light tough and pressure for face and head, forehead, cheeks, chin as well as pain and temp
- to test muscular innervation, palpate the temporal/masseter muscles
- have patient clench teeth while observing for jaw deviation or symmetry in muscle contration
Testing trigeminal nerve: masseter reflex
- proprioceptive sensory information from mesencephalic nucleus neurons
- synapse with trigeminal motor nucleus
- normal mandible jerks slightly upward with an UMN lesion this will be exaggerated
testing trigeminal nerve: corneal reflex
- pain information from cornea travels via spinal trigeminal tract to spinal trigeminal nucleus
- internuerons synapse on bilateral fascial nerve nuclei
- motor neurons in fasical nerve innervate obicularis oculi which closes eyelids
What will be seen clinically with deficits with trigeminal nerve lesions
Ipsilateral:
- loss of sensation, paresthesia or numbness of face
- trigeminal neuralgia/tic douloureux
- flaccid paralysis of muscles of mastication
- loss of corneal reflex
- deviation of jaw to ipsilateral side
what might accompany damage to the trigeminal nerve
- ataxia (middle cerebellar peduncle)
- nystagmus (cerebellum)
- vertigo
- tinnitus
- fascial palsy
Trigeminal neuralgia
- severe sharp stabbing pain in area of distribution
- begins and ends abruptly
- primary cause is pressure of blood vessel compressing the nerve
Corticobrainstem tract damage vs trigeminal nerve damage
- due to Bilateral connection, UMN lesions does not usually produce weakness in upper fasical muscles
- but if you damage the trigeminal nerve then there will be ipsilateral muscle weakness on the full 1/2 of face
Fasical motor functions
- fasical nucleus: located in the caudal pons
- muscles of the fascial expression, close the eye, move the lips
- involved in motor portion of corneal reflex (with CN V)
- dampens vibration of stapes
Fasical nerve sensation
- Touch, nocioceptive, and pressure info from pharynx, and skin near the ear canal
- Taste from the anterior 2/3 of the tongue. (to solitary nucleus)
- solitary tract - compact fiber bundle in the posterolateral medulla
fascial nerve visceral functions
- innervates the superior Salivatory Nucleus - in the medulla
- parasympathetic neurons innervate the salivary, nasal, and lacrimal glands
What occurs with fascial nerve damage
- Lesion of the corticobrainstem tract will result in weakness of the lower facial muscles contralateral to the lesion, without affecting the upper face
- Lesion of the facial nerve or motor nucleus: - paralysis of the entire half of the face –Bell’s Palsy
- Motor neurons innervating the upper portion of the face receive bilateral innervation (eyebrows and forehead).
- Motor neurons innervating the lower face receive only contralateral innervation
- ramsay hunt syndrome
- hyperascusis: over sensitivity to certain frequencies
- dry mouth
- corneal dryness
How to examine the fascial nerve
- observe face at rest then have patient raise eyebrows, wrinkle forehead, show teeth, puff out cheeks, close eyes tightly (while examiner attempts to open eyes)
differentiate between bells palsy and CVA
Bell’s Palsy
- inability to wrinkle brow
- dropping eyelid; inability to close eyes
- inability to puff cheecks
- dropping of mouth with inability to smile
CVA
- lower fascial muscles are involved
Ramsay hunt syndrome
- shingles
- fascial paralysis
- ear pain
- blisters on external ear
- occas- mouth blisters
- problems with balance
- vertigo
- hearing
- tinnitus
Glossopharyngeal IX
sensory function
- taste from the posterior third of the tongue
- tactile information from the soft palate pharynx (Gag reflex afferent limb)
Glossopharyngeal IX
Autonomic functions
- Baroreceptors in the carotid sinuses and chemoreceptors in the carotid bodies
Glossopharyngeal IX
Motor functions
- stylopharyngeus muscle (muscle of the soft palate)
- involved in swallow & speech
- motor nucleus is close to motor nuclei for X and IX = nucleus ambiguus
Glossopharyngeal IX
Nerve damage
- Gag reflex and swallowing affected
- Salivation decreased
Vagus nerve X
functions
- Mixed innervation of larynx, pharnx, and viscera
- Regulation of visceral activity, swallowing, speech, taste
Vagus nerve nuclei
- Nucleus Ambiguus (CN IX and X)
- bilateral innervation from the corticobrainstem tract
- innervate the voluntary muscles of the larynx (laryngeal nerve)
- Innervate constrictor muscle of the pharynx (closes to allow food to pass thru esophagus
Vagus nerve
afferent functions
- Touch, proprioceptive & nocioceptive information from the pharynx, larynx,
and part of the external ear
Vagus nerve Autonmic funtions
- Afferent and Efferent axons
- larynx, pharynx, trachea, lungs, heart, gastrointestinal tract (except the lower large intestine), pancreas, gallbladder, and liver
- reduce the heart rate, constrict bronchi, affect speech production, and increase digestive activity.
Vagus Nerve parasympathetic function
- Efferents
- Smooth muscles and glands
- pharynx, larynx, thorax, abdomen
- Reduction of heart rate, constrict the bronchi, and stimulate digestion
Vagus nerve and Glossopharyngeal nerves damage
- Damage to cranial nerve X and IX - commonly associated with each other
- Deficits are usually coupled
- Dysarthria, dysphagia, dysphonia
- diminished or loss of gag reflex
- uvular deviation
- cardiac and GI abnormalities
- dysarthria
Dysarthria-poor control of speech
Dysphagia-difficulty swallowing
Accessory
- Innervates the sternocleidomastoid and the trapezius muscles
- Nuclei are found dorsally in the medulla and in the upper cervical region of the spinal cord
- processes from the spinal cord ascend and enter the skull join with the rest of cranial nerve XI
enters the spinal cord from medulla
Damage to accessory nerve
- Complete lesion of the nerve itself paralyzes the ipsilateral sternocleidomastoid and trapezius muscles
- UMN lesion=paresis—cortical innervation is bilateral; muscle hypertonic
Hypoglossal Nerve
- Innervates the intrinsic and extrinsic muscles of the tongue
- Nucleus of the hypoglossal nerve receives connections from the contralateral corticobrainstem tract
- Hypoglossal nerve innervates the ipsilateral half of the tongue
Hypoglossal nerve: clinical deficits
- paresis or paralysis of the ipsilateral tongue
- fasciculations and atrophy
- ipsilateral deviation with protrusion
Corticobrainstem tract lesion = paresis of the tongue contralateral to the lesion
How to test hypoglossal nerve
stick tongue out and observe
CN II: optic nerve
- photosensitive cells in retina receives visual information from environment
- synpase with retinal output cells
- travels in optic nerve, through optic chiasm then through optic tract
- travels from lateral geniculate body in thalamus to primary isual cortex in occiptial lobe
- travels via optic radiation
visual fields projections
- information from left visual field travels to the right visual cortex
- information from right viusal field travels to the left visual cortex
optic nerve damage
- ipsilateral blindness
- loss of pupillary light reflex (must be able to see the light)
- frequently affect in those with MS
Cranial Nerve III
- motor to levator palpebrae, superior, medial and inferiro rectus and inferiro oblique
- parasymathetics to consonstrictor pupillae and cilary muscles via ciliary ganglion
when light is shown both pupils contrict
CN III lesion
- ptosis: droopy eye
- eye aimed outward and down
- diplophia: double vision
- unable to move the eye medially, down and up
- loss of pupillary light reflex/consensual reflex
- loss of pupil constriction
CN IV: trochlear
- superior oblique muscles for eye rotation (eye rolling)
- pathway: corticobrainstem tract to trochlear nucleus in midbrain, exits dorsally below inferiro colliculus
CN VI: abducens
- corticobrainstem tract neurons
- synpase on abducens nucleus on pons
- travel via abducens nerve to lateral rectus muscles
- moves pupil laterally
test by using a point (like of finger) nad making an H
Coordination of eye movement
- 6 cranial nerves
- 12 eye muscles
- coordination occurs on medial longitudinal fasciculus
- coordinates head and eye movements
- connects bilaterally oculomotor nuceli with each other and with vestibular and spinal accessory nuclei
eye reflexes
- CN II optic (afferent)
- CN III oculomotor) - efferent
- pupillary
- consensual
eye reflex
- Pupillary
- consensual
- shine ligh in eye
ipsilateral pupil constricts - shine light in eye contralateral pupil constricts
how does the consensual reflex work
- Consensual reflex:
- Axon of different neuron in pretectal nucleus crosses midline
- Synapses on contralateral Edinger-Westphal nucleus
- Axon synapses on contralateral ciliary ganglion
- Activates contralateral pupillary sphincter
Accomodation/convergence with eyes
- adjustments to view a near object
- pupils constrict
- increase lens curvature
- eyes converge (adduct)
Sympathetic effects on eyes
- dilate the pupil
- assist on elevating eyelid
- levator palpebrae superioris has dual innervation
- skeletal muscle CN III
- smooth muscle (superior tarsal muscle)
CN VIII: vestibulocochlear
- 2 branches
- cochlear = hearing
- vestibular = balance/where head is in space
CN VIII: vestibulocochlear
cochlear portion
- hearing
- sounds converted from mechnical to neural signals in inner ear
- vibration stimulates hair cells of cochlear nerve
- travels to cochlear nuclei in pontomedullary junction
use of sound information
signals travel from cochlear nuclei
- retiular formation
- inferior colliculus
- primary auditory cortex
- auditory assoication area
- wernicke’s area
How to test the cochlear portion of CN VIII: vestibulocochlear
ring test
- tunning fork
- can you hear it on the both sides the same
- stick on top of head
CN VIII: vestibulocochlear
vestibular branch
- transmits information regarding head position with respect to gravity and head movement
- balance
head impulse test to test this