Nerves of the Head Flashcards
Cranial Nerve I
- Olfactory
- Sensory
- Special sense: olfaction
Cranial Nerve II
- Optic
- Sensory
- Special sense: sight
- Goes through optic canal
Cranial Nerve III
- Occulomotor
- Motor
- Innervates: dorsal, ventral, and medial rectus mm., ventral oblique m., and levator palpebrae superioris m.
- Parasympathetic innervation to iris sphincter m. (constriction of pupil)
- Leaves the orbital fissure
Cranial Nerve IV
- Trochlear
- Motor
- Innervates: dorsal oblique m.
- Leaves orbital fissure
Cranial Nerve V
- Trigeminal
- Sensory and Motor
- 3 branches: Ophthalmic, Maxillary, Mandibular
CN V: Ophthalmic Branch
- Sensory
- Leaves orbital fissure
- Innervates: globe, periorbita, nasal mucosa, and medial aspect of the palpebrae
CN V: Maxillary Branch
- Sensory
- Round foramen > alar canal > rostral alar foramen
- Continues through infraorbital canal as the infraorbital nerve
- Innervates: superior eyelid, nasal mucosa, superior teeth, superior lip and nose
CN V: Mandibular Branch
- Sensory and Motor
- Through oval foramen
- Branches: buccal, lingual, inferior alveolar, mylohyoid, auriculotemporal
- Motor innervation to muscles of mastication
Cranial Nerve VI
- Abducens
- Motor
- Innervates: lateral rectus m. and retractor bulbi m.
- Through orbital fissure
Cranial Nerve VII
- Facial
- Motor and Sensory
- Innervates: muscles of facial expression, digastricus m.
- Taste to caudal 1/3 of tongue
- Parasympathetic to lacrimal gland and salicary gland
- Branches: dorsal and ventral buccal, auriculopalpebral
- Through stylomastoid foramen
Cranial Nerve VIII
- Vestibulocochlear
- Sensory
- Hearing and balance
- Through internal acoustic meatus
Cranial Nerve IX
- Glossopharyngeal
- Sensory: caudal 1/3 of tongue, and pharyngeal mucosa
- Motor: pharynx
- Parasympathetic: parotid and mucosal gland
- Through jugular foramen and tympano-occipital fissure
Cranial Nerve X
- Vagus
- Sensory and Motor
- S: general visceral afferent, ear canal, larynx, pharynx, esophagus, trachea, thoracic and abdominal viscera
- M: (PS) heart, lungs, abdomen, (S) pharynx and esophagus
- Through jugular foramen and the tympano-occipital fissure
Cranial Nerve XI
- Accessory
- Motor
- Innervates: mastoid part of sternocephalicus and cleidocephalicus mm., cervical part of cleidocephalicus m., and trapezius m.
- Through jugular foramen and tympano-occipital fissure
Cranial Nerve XII
- Hypoglossal
- Motor
- Innervates: extrinsic and intrinsic muscles of the tongue
- Through hypoglossal canal
What would a lesion of CN 1 look like?
How would you test the nerve?
- animal off feed/decreased appetite
- more likely secondary to other etiology
Treat:
- hold out treat while animal is blindfolded
- don’t use ammonia or noxious stimulant
What would a lesion of CN II look like?
How would you test the nerve?
- disruption in sense of sight: blindness
- often noted only after environment changes
Test:
- pupillary light reflex
- menace response
- visual placement reaction
- obstacle course
- tracking of a moving object
What is the Pupillary Light Reflex?
What does it mean if it is negative?
- shine light into one eye, both pupils should constrict
- CN II recognizes light, CN III constricts pupil
- if the pupil is dilated, CN III is damaged
What would a lesion of CN III look like?
How would you test the nerve?
- strabismus: static deviation of affected eye
- eye will move lateral
Test
- tracking of moving object while keeping head stready: look for bilateral movement
- PLR
- normal eye position
What would a lesion of CN IV look like?
- abnormal rotation of pupil: ventral pupil will be pulled medially by ventral oblique
- lateral rotation of pupil
- strabismus
What would a lesion of CN V Ophthalmic branch look like?
- decreased/absent corneal reflex: no sensation to cornea
- decreased/absent palpebral relfex if touching medial canthus
What would a lesion of CN V Maxillary branch look like?
- decreased/absent palpebral reflex if touching lateral canthus
- decreased/absent response to pinching of upper lip
What would a lesion of CN V Mandibular branch look like?
- decreased/absent response to pinching of lower lip
- decreased/absent ability to close mouth/poor jaw tone
- atrophy of temporalis muscle
What would a lesion of CN VI look like?
- medial strabismus
- decreased/absent ability to retract the globe (absent corneal reflex)
- would not see third eyelid sweep across cornea
What nerves are needed to coordinate eye movement?
Oculomotor (III)
Trochlear (IV)
Abducent (VI)
What would a lesion of CN VII look like?
- decreased/absent palpebral reflex
- decreased/absent menace response
- decreased/absent response to pinching of upper or lower lip (can still feel pain)
- deviated philtrum to normal side
- dropping/lack of facial expressions on affected side
What would a lesion of CN VIII look like?
- decreased/absent hearing
- head tilt, head turn, nystagmus, circling, leaning, ataxia
What would a lesion of CN IX look like?
- trouble with eating/swallowing
- dysphagia (cough, gag, choke)
- decreased gag reflex
What would a lesion of CN X look like?
- decreased/absent gag reflex
- increased heart rate, decreased gut sounds
What would a lesion of CN XI look like?
- possible gait change and altered head movement associated with inability to use innervated muscles
- atrophy of neck muscles
- laryngeal paralysis
What would a lesion of CN XII look like?
- difficulty eating/drinking
- tongue set off to unaffected side
- decreased tongue tone
- complete paralysis of tongue if bilaterally affected
What nerves are tested in the palpebral reflex?
Afferent: trigeminal
Efferent: facial
What nerves are tested in the corneal reflex?
Afferent: ophthalmic branch of trigeminal
Efferent: abducens
What nerves are tested in the menace response?
Afferent: optic
Efferent: facial
What nerves are tested in the pupillary light reflex?
Afferent: optic
Efferent: occulomotor
What nerves are tested in the gag reflex?
Afferent and efferent: glossopharyngeal and vagus
