Cranial Neuropathy Flashcards
What’s the function and clinical manifestation of CN I?
Olfactory n,
sense of smell
disorder = inability to smell
What’s the function and clinical manifestation of CN II?
Optic n,
vision
disorder = blind, dilated/ unresponsive pupils
What’s the function and clinical manifestation of CN III?
Occulomotor n,
Eye movement (extra-ocular muscle) & pupil constriction (parasympathetic)
disorder: ventrolateral strabismus, dilated pupils, diminished/absent PLR
What’s the function and clinical manifestation of CN IV?
Trochlear n,
Eye movement
disorder: dorsomedial strabismus
What’s the function and clinical manifestation of CN V?
Trigeminal n.
Sensory to face;
motor to muscles or mastication
disorder: rubbing/pawing @ face, head muscle atrophy, dropped jaw if bilateral motor
What’s the function and clinical manifestation of CN VI?
Abducent n.
Eye movement (lateral rectus & retractor bulbi)
disorder: medial strabismus
What’s the function and clinical manifestation of CN VII?
Facial n,
Motor to facial expression, saliva and tear production (parasympathetic);
Sensory to rostral tongue
Disorder: inability to close eyelid, move ear, or retract lips; hemifacial tetany, deviation of the nasal philtrum (contralateral), dry eye, drooling
What’s the function and clinical manifestation of CN VIII?
Vestibulocochlear n,
Balance and hearing
Disorder: head tilt, deaf, vestibular ataxia, positional strabismus, nystagmus
What’s the function and clinical manifestation of CN IX?
Glossopharyngeal n.
Sensory and motor to the pharynx
Disorder: diminished gag reflex, difficulty swallowing
What’s the function and clinical manifestation of CN X?
Vagus n
sensory and motor to pharynx, larynx, and viscera (movement of throat)
Disorder: loss of voice, coughing, regurgitation. Diminished gag reflex, dysphagia, laryngeal paralysis, megaesophagus
What’s the function and clinical manifestation of CN XI?
Accessory n
motor to trapezius (movement of neck and shoulder)
Disorder: difficult to appreciate
What’s the function and clinical manifestation of CN XII?
Hypoglossal n
Motor to tongue muscles
Disorder: atrophy of tongue, inability to retract tongue if bilateral; difficulty eating
What changes can be noted on ophthalmic exam with optic neuritis?
Posterior segment of the eye:
- optic disc swelling
- vascular congestion
- hemorrhage
- peripapillary neuroretinitis
What are some differentials for optic disc swelling?
papilledema/ optic nerve edema; accompanied by uveitis and glaucoma
What are some causes of optic neuritis?
- Infectious (canine distemper, fungal, mycotic)
- immune-mediated
- tumour
- idiopathic
How can you differentiate between optic neuritis and SARDS (sudden acquired retinal degeneration syndrome)?
Optic neuritis –> ERG = normal, SARDS ERG = extinguished
What’s the prognosis for vision recovery with optic neuritis?
guarded to poor
Which nerves innervate the extra-ocular muscles?
Oculomotor (CN III): pupil constriction
Trochlear (CN IV): eye position
Abducent (CN VI): eye position
Which cranial nerves are involved in cavernous sinus (CSS) / orbital fissure (OFS) syndrome?
CN III, IV, VI, V (ophthalmic or maxillary branches)
Due to close proximity of these axons on the floor of the skull adjacent to the cavernous sinus prior to exiting the skull through the orbital fissure
What are the clinical signs of cavernous sinus (CSS) / orbital fissure (OFS) syndrome?
- external and internal ophthalmoplegia (muscle paralysis)
- ptopsis
- reduced corneal sensitivity (CN V)
- neurotrophic keratitis
What’s the most common cause of cavernous sinus (CSS) / orbital fissure (OFS) syndrome?
primary or metastatic tumour
in cats, infectious is possible too
What’s the most commonly affected branch in trigeminal neuropathy?
Motor (mandibular branch); isolated sensory branches (ophthalmic / maxillary ) = rare
What are some signs dysfunction of the mandibular branch of CN V?
- dropped jaw (flaccid bilateral paresis)
What are some differentials for dropped jaw?
- mechanical jaw function (TMJ fracture/ avulsion)
- pain associated with jaw movement (myositis, retrobulbar mass)
- inflammatory (neospora, toxoplasma)
- idiopathic
- neoplastic
What’s Pontomedullary syndrome?
If it’s not just peripheral CN V –> ie. involving pons
may have c/s due to dysfunction in CN VI-XII; central vestibular signs, and altered mentation (depressed)
What’s the most common cause of trigeminal neuritis in the dog?
idiopathic
concurrent facial n. paralysis possible; Horner’s also possible
What’s a common cause of acute, unilateral atrophy of the muscles of mastication?
Trigeminal nerve sheath tumour (ipsilateral)
- can have altered facial sensation (rubbing/ pawing at face; pain)
- Horner’s
- facial n involvement
What are some signs of facial nerve paralysis/ neuropathy?
- acute inability to close the eyelids, drooping of ear/lip/ drooling (ipsilateral)
What are some causes of facial neuropathy?
- otitis media/ interna
- trauma (bulla osteotomy)
- idiopathic (75% of dogs, 25% of cats)
- CN VIII can also be affected: vestibular signs
What’s the prognosis of idiopathic facial neuropathy?
spontaneous recovery in dogs is possible: 3-8 weeks
Which cranial nerves are involvement in swallowing?
CN IX, X, XI, XII
What cranial nerves are involved in prehension of food?
Jaw (CN V), lip (CV VII), tongue (XII)
What are some common causes of swallowing disorders?
- primary myopathies
- polyneuropathy
- neuromuscular junctional disorders
caudal brain stem lesions
Which CN innervate the esophagus?
XI and XII
Which CN innervates the larynx?
XII, and recurrent laryngeal nerve
What are the clinical signs associated with Horner’s Syndrome?
- ptosis
- enophthalmos
- prolapsed 3rd eyelid
- miosis (small pupil)
Describe the 3-neuron oculosympathetic pathway.
1st order neuron: UMN/ central, originates in the rostral brainstem –> goes down spine to synapse on 2nd order: cell bodies located in T1-T3 –> goes up via the vagosympathetic trunk to synapse on the 3rd order: post-ganglionic neurons in the cranial cervical ganglion –> projects to eye and adnexa
How can pre- vs post-ganglionic disorders be differentiated?
Phenylephrine test
If mydriasis develops within 20min, then it’s post ganglionic. If it takes more than 20min, then it’s pre-ganglionic
