De Lahunta Chpt 6

Question 1

Which nerve innervates the:

1) Cricoarytenoideus dorsalis muscle
2) Cricothyroideus muscle
3) What is the clinical sign caused by dysfunction of the cricoarytenoideus dorsalis m.?

Answer 1

1. caudal laryngeal nerve (CN X)
2. cranial laryngeal nerve (CN X)
3. inspiratory dypsnea. Roaring in horses

Question 2

What 3 muscles are innervated by the external branch of the accessory n.?

Answer 2

Trapezius m.
Sternocephalicus m.
Cleidocephalicus m.

Question 3

What is the course of the internal branch of the accessory nerve and what muscles does it innervate?

Answer 3

Some cranial roots from medullary cell bodies of CN XI after exiting the jugular foramen, join the vagus nerve to form the internal branch of the accessory nerve. It innervates intrinsic muscles of the larynx, cervical esophagus, and cranial thoracic esophagus

Question 4

What are 3 dog breeds that have inherited laryngeal paralysis? Give a description of each one.

Answer 4

Bouvier des Flandres. 4-6 mo. Autosomal dominant genetic disorder. Bilateral abiotrophy caudal nucleus ambiguous

Rottweiler 8-10 wk old progressive laryngeal paresis and progressing to UMN gait abnormality. Neuronal vacuolation and spinocerebellar degeneration à encephalomyelopathy and polyneuropathy

Leonbergers 1-3 YO male laryngeal paralysis followed in a few weeks by progressive sciatic-tibial nerve deficit. Sex-linked recessive.

Other breeds: Young Siberian x Husky cross; bull terriers; dalmations

Question 5

Congenital megaesophagus vs. Late onset megaesophagus.

1) What are the breeds and what is the pathogenesis?
2) What disease is the late onset megaesophagus thought to be a form of?

Answer 5

1) Congenital: reflex esophageal dysfunction
Breeds: German Shepherd, Lab Retr, Great Dane, Shar Pei, Newfoundland
Inherited in: wirehaired Fox terrier, Miniature Schnauzer

2) Late onset MG is thought to be a form of focal MG

Question 6

Guttural Pouch Mycosis.

Causative agent?
Most common site of inflammation?
What are the clinical signs assoc with that?

Answer 6

commonly caused by aspergillus

Most common site of inflamm is the dorsocaudal aspect of the medial compartment
CN 9 and 10 course ventral to guttural pouch à dysphagia
Erosion into internal carotid aa. Or maxillary aa. à epistaxis
Laryngeal hemiparesis
Horner’s syndrome
+/- facial n. paresis, hypoglossal n. paresis, vestibular n. dysfunction

Question 7

What is the most impt muscle to open the glottis and increase airway size?

Answer 7

Cricoartenoideus dorsalis m.

Question 8

Equine laryngeal hemiparesis / hemiplegia

Describe the pathogenesis.

Answer 8

Horses with long necks are at risk

Left hemiparesis – left recurrent laryngeal n. has longer course around ligamentum arteriosum and aortic arch. - - Really bilateral but worse on the left
Denervation atrophy of laryngeal m. that are innervated by the recurrent laryngeal nerve.
Dying back neuropathy. Inability of neurons of the motor nucleus of the accessory nerve to maintain integrity of such long motor neurons.
The cricoarytenoideus dorsalis m. is the most essential to open the glottis and increase airway size.

Question 9

Name 2 large animal toxicities that can cause laryngeal paralysis/paresis

Answer 9

1) Chronic lead toxicity in horses causes polyneuropathy that includes recurrent laryngeal n. paresis
2) Organophosphate haloxone anthelmintic to arabian foals starting at 2 yers of age cause laryngeal paralysis

Question 10

1) Unilateral tongue atrophy is almost pathognomonic for what disease in the horse?
2) And what is a common cause for tongue paresis in the cattle?

Answer 10

1) S. neurona

2) L. monocytogenes causing encephalitis

Question 11

Horse with dysphagia resulting from leukoencephalomalacia. What is the causative agent and pathogenesis?

Answer 11

“moldy corn toxicity”

ingestion of mycotoxin fumonisin B1
produced by fungus Fusarium moniliformis

Note: dysphagia is caused by acute dysruption of UMN corticonuclear tracts that control voluntary cranial nerve function

Question 12

Cattle with dysphagia caused by acute prosencephalic hemorrhagic necrosis. What is the causative pathogen and pathogenesis?

Answer 12

caused Histophilus somnus resulting in vasculitis

Note: dysphagia is caused by acute dysruption of UMN corticonuclear tracts that control voluntary cranial nerve function

Question 13

Listeria monocytogenes

1) Describe the pathogenesis
2) What is the treatment?

Answer 13

Invade sensory nerve endings in oral mucosa –> migrate via nerves to the pons via trigeminal nerve.

+/- facial paralysis, vestibular ataxia and head tilt

Treat with large doses penicillin

Question 14

Equine Herpesvirus 1

Answer 14

causes vasculitis of small bld vessels in CNS –> thrombosis and myelopathy with ischemia or hemorrhagic infarction of parenchyma.

Clinical signs always acute and nonprogressive after 72 hr.

+/- TL spine white matter lesion –> ataxia and paresis of pelvic limbs. Also usually have a mild tone in tail and anus. And difficulty emptying bladder

Usually no CN signs with this disorder

Question 15

What are the cranial nerves involved in cavernous sinus syndrome?

Answer 15

Cavernous sinus syndrome:
o	O – oculomotor nerve
o	T – trochlear =-nerve
o	O – ophthalmic branch of trigeminal nerve
o	M – maxillary branch of trigeminal nerve
o	C – Internal carotid artery
o	A – Abducent nerve
o	T – trochlear nerve

Question 16

In Siamese cats, what eye positional abnormality can be considered normal?

Answer 16

Bilateral medial strabismus

Question 17

What cranial nerves exit through the orbital fissure

Answer 17

CN 3, 4, 5 (ophthalmic), 6

Question 18

At what level of the brain does the trigeminal nerve exit and what are the courses of the 3 different branches as it leaves the cranium?

Answer 18

The trigeminal nerve leaves the brain stem at the level of the pons, rostral to the trapezoid body. It passes through the trigeminal canal (located on the medial aspect of the petrosal bone) and divides into three nerves: ophthalmic, maxillary and mandibular. These nerves leave through foramina located in the wing of the sphenoid bone. The ophthalmic nerve leaves the cranial cavity through the orbital fissure together with the oculomotor, trochlear and abducent nerves. The maxillary nerve enters the round foramen, that opens into the alar canal, and exits through the rostral alar foramen. The mandibular nerve leaves through the oval foramen.

Question 19

2 extra-axial neoplasms that occur in the middle fossa of young dogs

Answer 19

germ cell neoplasm, meningioma

Question 20

Does the VENTRAL oblique muscle intort or extort the eye?

Which cranial nerve is this innervated by?

Dysfunction of this cranial nerve results in what kind of strabismus?

Answer 20

extort

CN 3

Ventrolateral strabismus

Question 21

Does the DORSAL oblique muscle introit or extort the eye?

Which cranial nerve is this innervated by?

Dysfunction of this cranial nerve results in what kind of strabismus?

Answer 21

Intort

CN 4

Dorsomedial

Question 22

Does the trochlear nerve innervate the trochlearis m. ipsilateral or contralateral to its nucleus?

Answer 22

contralateral

Question 23

Ruminant with dorsomedial strabismus

Answer 23

polioencephalomalacia from thiamine deficiency

Question 24

Middle ear effusion from trigeminal nerve dysfunction. what is the pathogenesis?

Answer 24

Dysfunction of the mandibular branch of the trigeminal nerve results in denervation of the tensor veil palatine m., responsible for regulation of normal tone of auditory tube

Question 25

Name the 5 muscles of mastication

Answer 25

masseter, temporal, pterygoid, rostral digastricus, mylohyoideus

Question 26

Most common cause of acute inability to close the mouth in dogs.

What is the pathogenesis

What does histopathology show?

Answer 26

bilateral nonsuppurative trigeminal neuritis

Autoimmune, predominantly primary demyelinating disease. Axonal degeneration is rare.

Lymphoplasmacytic perivascular cuffing with macrophages engulfing degenerate myelin
(note: similar lesion to canine polyardiculoneuritis)

Question 27

Bilateral trigeminal neuritis. What other CN dysfunction may there be?

Answer 27

1/3 of dogs have loss of facial sensation

A few dogs may have Horner’s (involvement of postganglionic sympathetic axons joining the ophthalmic nerve near is origin from trigeminal nerve)

Rarely some dogs may have mild facial neuritis and paresis.

Question 28

Bilateral trigeminal neuritis in horse and ruminant?

Answer 28

horse - sarcocystic neurona

ruminant - Listeria monocytogenes

Question 29

Stapedius muscle innervated by which CN?

Answer 29

CN 7

Question 30

Tensor tympani innervated by which CN?

Answer 30

CN 5 (mandibular branch)

Question 31

Tensor velli palatini innervated by which CN?

Answer 31

CN 5 (mandibular branch)

Question 32

Levator velli palatini innervated by which CN?

Answer 32

levator veli palatini (innervated by the glossopharyngeal and vagus nerves), when this muscle acts in combination with the tensor vela palatine, they opens the orifice of the auditory tube into the pharynx.

Question 33

sensation to the rostral 2/3 of tongue

Answer 33

CN5, CN7

Question 34

Course of the facial nerve in general as it leaves the brainstem

Answer 34

leave the brain stem ventrolaterally at the rostral portion of the trapezoid body. They are surrounded by a common sheath of dura mater together with the vestibulocochlear nerve. Travels with vestibulocochlear nerve through internal acoustic meatus (in petrous temporal bone). Becomes dorsal to CN8 and then enter facial canal (in temporal bone), at this point joined by postganglionic sympathetic fibers and emerg through stylomastoid foramen → innervate face.
- facial nerve at the level of the petrous temporal bone have parasympathetic GVE axons in major petrosal nerve.

Question 35

Stanchion paralysis

Answer 35

Cattle stanchion paralysis. If move head out of stanchion injure auriculopalpebral n as crosses over zygomatic arch. Eyelid paresis/paralysis. +/- ear droop or loss of motion if auricular branch of auriculopalepbral n involved.

Question 36

Horses with compression injury of facial nerve when tabled for surgery. What are the neuro deficits?

Answer 36

buccal branches of the facial nerve course laterally across the caudal border of ramus of mandible. Can be injured from compression also if halter not removed
Neuro deficits:
- drooped inferior lip
- deviated nose and superior lip
- eyelid and ear position and movement are normal

Question 37

Otitis media in horses resulting in dysphagia

Answer 37

Proliferative bone lesion affecting articulations of the stylohyoid, tympanohyoid, and temporal bones. Proliferation results in ankylosis of articulations –> movement of hyoid apparatus to swallow is prevented. Vocalization may leads to fracture of temporal bone.

Question 38

Glossopharyngeal n course from brainstem to exit cranium

what structures does it innervate?

Answer 38

• nucleus ambiguus →jugular foramen → emerg through tympano-occipital fissure → joined by a branch of vagus to innervate pharynx and palate

also provides Parasymp innervation to salivary glands