Cranial Nerves (2) Flashcards
What is Cranial Nerve I?
Olfactory Nerve
How long are CN I nerve fibers?
Only a few millimeters long
Where does CN I run from?
From uppermost recess in nasal cavity through cribiform plate
What does CN I synapse with?
The olfactory bulb
What does CN I connect with? What implications does this have?
Connects extensively with the limbic system. Can evoke memory and emotions
What process can CN I cells undergo?
CN I cells can undergo mitosis
When do you see lesions of CN I?
Facial fractures
What happens with a lesion of CN I?
Complete or partial loss of smell
How do you test CN I?
Test familiar odors
What is CN II?
Optic nerve
Where does CN II originate?
In the retina
What is CN II myelinated by?
Oligodendrocytes (part of CNS)
Where does CN II enter the skull?
Enters middle cranial fossa via optic canal
What happens to fibers from each optic nerve?
Fibers from each optic nerve cross at optic chasm
What happens with a lesion of CN II?
Blindness or visual field loss
How do you test CN II?
Test the visual fields
What is CN III?
Oculomotor
WHere is the nucleus for the occulomotor nerve?
CN III has a nucleus in the rostral midbrain
Where does CN III exit the midbrain?
CN III exits the brain at the interpeduncular fossa
Where does CN III exit the brain?
superior orbital fissure
What nerves exit the superior orbital fissure?
CN’s III, IV, V1. VI
What muscles does CN III enervate?
Inferior oblique Superior Rectus inferior rectus Medial rectus Levator palpebrae
What action does the levitator palpebrae do?
Opens the eyelid
What type of innervation does CN III provide to ciliary ganglion and what does this accomplish?
Provides preganglionic parasympathetic fibers to the cillary ganglion which innervate sphincter of the iris enabling the pupillary light reflex
What 7 things could happen with a lesion of CN III?
- Eyelid ptosis at rest
- External strabismus at rest (unopposed lateral rectus)
- Inability to move affected eye vertically or medially
- Dilation of pupil
- Loss of pupillary light reflex
- Loss of vergence
7 diplopia
Which eye muscles are not innervated by CN III?
Superior oblique
lateral rectus
How do you test CN III?
Eye movements
Pupillary light reflex
Vergence
What is CN IV?
Trochlear
Where is the CN IV nucleus located?
In the caudal midbrain
Where does CN IV exit the midbrain?
dorsally below the inferior colliculus
Where does CN IV exit the skull?
Through the superior orbital fissure
What muscles does CN IV innervate?
The occulomotor nerve innervates the superior oblique muscle
WHat happens with a lesion to CN IV?
A lesion to the trochlear nerve may result in:
inability to move eye inferior when adducted
May cause diplopia
Hypertropia
What is hypertropia?
affected eye vertically deviates upward and in extorsion
How do you test CN IV?
Eye movements
What is CN V?
Trigeminal nerve
What are the different parts of the trigeminal nerve?
CN V has
V1,V2, and V3
What is V1?
opthalamic portion of CN V
What is V2?
maxillary portion of CN V
What is V3?
Mandibular portion of CN V
Where is the motor and primary sensory nucleus of CN V located?
Located in the rostral pons
WHere does CN V exit the brainstem?
Exits at midpons
What is the large sensory ganglion associated with CN V? Where is this ganglion located?
Trigeminal or semilunar ganglion, which is located in a depression in middle cranial fossa
Where does V1 exit the skull?
Exits middle cranial fossa through the superior orbital fissure
Where does V2 exit the skull?
exits the middle cranial fossa via the foramen rotundum
Where does V2 exit the skull?
exits the middle cranial fossa through the foramen ovale
What does CN V supply sensation to?
The face and part of the head
What motor innervation does CN V supply?
Supplies motor innervation to the muscles of mastication (masseter, temporal is, medial/lateral pterygoids)
What is Tic Douloureux?
Trigeminal neuralgia.
Characterized by brief periods of intense pain experienced over one of the divisions of CN V. Can be treated pharmacologically but also may surgically cut the nerve removing all sensation
What is the corneal blink reflex?
WHen you touch the cornea with a small piece of cotton. NOrmal response is a blink
What nerves does the corneal blink reflex test?
Test CN V and CN VII
What is the jaw jerk reflex analogous to?
Analogous to the deep tendon reflex
What is a positive response to the jaw jerk reaction?
reflexive contraction of jaw when hit with reflex hammer.
Normally absent; sign of upper motor neuron lesion if present
What does a lesion of CN V result in?
Loss of sensation in face and head
Loss of corneal blink reflex
Loss of muscles of mastication
How do you test CN V?
sensation of face
Corneal blink reflex
muscle strength of muscles of mastication
What is CN VI?
Abducens
Where is the CN VI nucleus located?
In caudal pons
Where does CN VI exit the brainstem?
Medially at the pontomedullary junction
Where does CN VI exit the skull?
Through the superior orbital fissure
What muscle does CN VI innervate?
The abducens innervates the lateral rectus muscle.
What is the result of a lesion of CN VI?
Medial strabismus (esotropia)
Inability to abdyct the eye
Diplopia
How do you test CN VI?
eye movements
What is CN VII?
Facial Nerve
Where is the nucleus for CN VII?
In the caudal pons
Where does CN VII exit the brainstem?
Pontomedullary jxn
Where does CN VII exit the posterior cranial vault?
Internal acoustic meatus
What part of the temporal bone does CN VII go through?
THe petrous portion
Where is the sensory portion of CN VII located?
Geniculate is embedded in the temporal bone
Where does the CN VII exit the skull?
Stylomastoid foramen
What does CN VII innervate?
Facial muscles
What part of the tounge does CN VII innervate?
THe anterior 2/3 of the tounge
What glands does CN VII innervate?
submandibular, sublingual gland and lacrimal gland
What happens with a lesion of CN VII?
Bells palsy (paralysis of the muscles of facial expression
loss of corneal blink reflex (with CN V)
Loss of taste on anterior 2/3 of tongue
What is CN VIII?
Vestibularcohclear
What are the two divisions of CN VIII?
Vestibular and cochlear divisions
What is the function of the vestibular division of CN VIII?
Regulates posture, equilibrium responses
Coordinates eye movement
What happens with a lesion of the VEstibular division?
Loss of equilibrium
Nystagmus
Vertigo
Nausea
How do you test the vestibular division of CN VIII?
Caloric test
“COWS”
What happens with a lesion of the cochlear division of CN VIII?
Tinnitus
Deafness
What is the difference between nerve deafness and conduction deafness?
Nerve deafness is decreased hearing due to nerve damage while conduction deafness is decreased hearing due to middle ear problems
What is Rinne’s Test?
Tuning fork held against mastoid until it can’t be heard. THen tuning fork is placed in from of ear
What is a normal response to Rinne’s test?
Normal-Air conduction is better than bone so pt can hear fork when its placed in front of ear
What is an abnormal response to Rinne’s test?
Fork can only be heard through mastoid process. Sign of conduction deafness
What is Webers test?
Tuning fork is held on vertex of sull
What is a normal response to Webers test?
Can hear tuning fork equally well in both ears
What happens if you have conduction deafness during the Weber test?
You will hear the ringing louder in the affected ear
What happens if you have nerve deafness in one ear with the Weber test?
You will hear the tuning fork louder in the unaffected ear
What is CN IX?
Glossopharyngeal
Where is the nucleus of CN IX located?
Rostral medulla
Where does CN IX exit the brainstem?
Postolivary sulcus
Where does CN IX exit the posterior cranial fossa?
Through the jugular foramen
Where are the sensory ganglion of CN IX located?
outside of the skull
What sensory innervation does CN IX provide?
Sensory innervation of pharynx and posterior 1/3 of tounge
What parasympathetic innervation does CN IX give off?
parasympathetic innervation of parotid gland
What muscles does CN IX innervate?
stylopharyngeus muscle
What happens with a lesion of CN IX?
Loss of gag reflex
loss of taste on posterior 1/3 of tongue
How do you test CN IX?
Test taste on posterior 1/3 of tongue
Test gag reflex
What is CN X?
Vagus nerve
Where is the nucleus of CN X?
In the rostral medulla
Where does CN X exit the brainstem?
Exits at post olivary sulcus
Where does CN X exit the posterior cranial vault?
Exits at jugular foramen
What sensory innervation does CNX give off?
Sensory innervation to the pharynx, larynx and viscera
What parasympathetic innervation does CN X give off?
Parasympathetic innervation to abdominal viscera
What motor innervation does CN X give off?
motor innervation to pharyngeal and laryngeal muscles
What happens with a bilateral lesion of CN X?
Usually fatal
What happens with unilateral lesion of CN X?
dysarthria and difficulty in swallowing
loss of gag reflex
Which CN’s are tested when you check the gag reflex?
CN IX and X
What are the two divisions of CN XI?
Spinal and Cranial root
What spinal cord segments do the spinal portion of CN IX arise from?
C2-C5/6
Where does the spinal portion of CN XI enter the posterior cranial fossa?
Enters through the foramen magnum
Where does the spinal portion of CN XI separate from the cranial portion of CN XI?
Separates before leaving the jugular foramen
What does the spinal portion of CN XI innervate?
Motor innervation of SCM and Trapezius
Where does the cranial root of CN XI originate?
Near the dorsal motor nucleus of vagus
What happens with a lesion of CN XI?
Weakness in ipsilateral SCM and trapezius
How do you test CN XI?
Muscle test SCM and trapezius
What is CNX!!?
Hypoglossal
Where is the nucleus of CN XII?
in the rostral medulla
What does CN XII innervate?
The nerves of the tongue
Where does CN XII exit brainstem?
In preolivary sulcus
What happens with a lesion of CN XII?
- Inability to prodrude tongue in midline (unilateral)
2. With bilateral lesion, difficulty swallowing and eating
How do you test CN XII?
Test tongue movements and swallowing eval
