Disorders Affecting CN Function Flashcards
Lesions of olfactory nerve can result in what?
an inability to smell
What may also interfere with the function of the olfactory nerve?
Smoking or excessive nasal mucus
What does a complete interruption of the optic nerve result in?
- ipsilateral blindness
- loss of the pupillary light reflex
Complete lesion of oculomotor nerve causes what 6 things?
- Ptosis (drooping of the eyelid)
- Ipsilateral eye looks outward and down
- Diplopia (double vision)
- Deficits in moving the ipsilateral eye medially, downward, and upward
- Loss of pupillary reflex and consensual response to light
- Loss of constriction of the pupil in response to focusing on a near object
Lesion of the trochlear nerve prevents the activation of which muscle? What does this result in?
the superior oblique muscle, which means the ipsilateral eye cannot look downward and inward
What are the symptoms of a trochlear nerve lesion?
- double vision
- difficulty reading
- visual problems when descending stairs
Lesion of the abducens nerve prevents the activation of which muscle? What does this result in?
the lateral rectus muscle, which means the ipsilateral eye will look inward because the pull of the medial rectus muscle is unopposed
What are the symptoms of a abducens nerve lesion?
- double vision
- inability to abduct eye
What does a lesion affecting the medial longitudinal fasciculus produce?
internuclear ophthalmoplegia (INO)
An internuclear ophthalmoplegia (INO) disrupts the connection between what 2 nuclei?
the abducens nucleus and the oculomotor nucleus
What does internuclear ophthalmoplegia result in?
Normal movement of the eye contralateral to the lesion.
The eye ipsilateral to the lesion cannot adduct past the midline when the fellow eye moves laterally.
Complete lesion of the trigeminal nerve causes what?
anesthesia of the area supplied by the ophthalmic, maxillary, or mandibular branch
If only the ophthalmic division of the trigeminal nerve is affected, what is the result?
The afferent limb of the blink reflex will be interrupted, preventing blinking in response to touch stimulation of the cornea.
If only the mandibular division of the trigeminal nerve is affected, what is the result?
The jaw will deviate toward the involved side when the mouth is opened, and the masseter reflex will be lost.
What is Trigeminal Neuralgia?
a dysfunction of the trigeminal nerve that produces severe, sharp, stabbing pain in the distribution of one or more branches of the trigeminal nerve
Bell’s palsy effects the axons of which cranial nerve?
Facial (CN VII)
In patient’s with Bell’s palsy is facial somatosensation affected?
Facial somatosensation is normal, although people may report feeling numbness due to the lack of proprioceptive feedback from the paralyzed muscles
Lesion of the vestibulocochlear nerve causes what?
loss of hearing in the ipsilateral ear
Loss of hearing in one ear interferes with what?
the ability to locate sounds
What are the 2 classifications of deafness as a result of peripheral disorders (the cochlea, organ of Corti or the cochlear nerve of the CN VIII)?
- conductive
- sensorineural
When does conductive deafness occur?
When transmission of vibrations is prevented in the outer or middle ear
What are a couple common causes of conductive deafness?
excessive wax in the outer ear canal or otitis media
Sensorineural deafness is due to what?
Damage to the receptor cells or the cochlear nerve
What are a couple common causes of sensorineural deafness?
- acoustic trauma
- ototoxic drugs
- Ménière’s disease
- acoustic neuroma
What is Tinnitus?
ringing or buzzing in the ears
What does a complete lesion of the glossopharyngeal nerve interrupt?
The afferent limb of both the gag reflex and the swallowing reflex
What is decreased following glossopharyngeal lesion?
Salivation
What does a complete lesion of the vagus nerve result in?
- difficulty speaking and swallowing
- poor digestion
- asymmetrical elevation of the palate
- hoarseness
Complete lesion of the accessory nerve paralyzes the _____ sternocleidomastoid and trapezius muscles
ipsilateral
How can you tell the difference between a cranial nerve lesion and an UMN lesion? Explain why…
Upper motor neuron (UMN) lesions cause paresis rather than paralysis because cortical innervation is bilateral, and the muscles become hypertonic rather than hypotonic.
What does a complete lesion of the hypoglossal nerve result in?
atrophy of the ipsilateral tongue
What is the result when a person with a hypoglossal lesion is asked to stick out their tongue?
the tongue protrudes ipsilaterally rather than in the midline
The problems with tongue control associated with a hypoglossal nerve lesion result in what?
difficulty speaking and swallowing
What is dysphagia?
difficulty with swallowing
Frequent choking, lack of awareness of food in one side of the mouth, or food coming out of the nose may indicate dysfunctions of which cranial nerves?
V VII IX X XII
What is Dysarthria?
poor control of the speech muscles (these patients can understand the spoken language and can write and read)
Dysarthria may be caused by lower motor neuron involvement of which cranial nerves?
V
VII
X
XII
Which cranial nerves can you suspect if the patient has asymmetrical pupils?
II or III
Which cranial nerve can you suspect if the patient has a droopy upper eyelid?
III
Which cranial nerves can you suspect if the patient has abnormal eye position?
III, IV, or VI
Which cranial nerve can you suspect if the patient has drooping or asymmetrical facial muscles?
VII
Which cranial nerves can you suspect if the patient has difficulty with articulating words?
V, VII, X, or XII
