Lab 5

Question 2

What cranial nervces emerge from the midbrain?

Answer 2

Oculomotor and Trochlear

Question 3

What cranial nerves emerge from the pons?

Answer 3

Trigeminal nerve

Question 4

What cranial nerves emerge from the medulla?

Answer 4

Abducent

Facial

Vestibulocochlear

Glossopharyngeal

Accessory

Hypoglossal

Question 5

What cranial nuclei contribute to CN III?

Approximately where in the brainstem is it located?

Answer 5

Motor nucleus of the oculomotor nerve, parasympathetic nucleus of the oculomotor nerve

These nuclei are located in the rostral colliculi

see pg 154

Question 6

What cranial nuclei contribute to CN IV?

Where are they located?

Answer 6

motor nucleus of the trochlear nerve (motor function only!)

located in the caudal colliculi

see figure 10-2B

The trochlear nerve is an exception to the rule of non-crossing over! It innervates the contralateral dorsal oblique

Question 7

What nuclei contribute to CN V?

Where are they located?

Answer 7

Motor nucleus of the trigeminal nerve - in the dorsolateral area of the pons

3 sensory nuclei: mesencephalic nucleus of the trigeminal nerve (in the midbrain), the pontine sensory nucleus of the trigeminal nerve (in the pons), the ncleus of the spinal tract of the trigeminal nerve (in the medulla oblongata)

Question 8

What nuclei contribute to CN VI?

Where are they located?

Answer 8

Motor nucleus of the abducent nerve - motor only

located immediately ventral to the genu of the facial nerve, in the medulla

see page 180

Question 9

Which nuclei contribute to CN VII?

Where are they located?

Answer 9

Motor nucleus of the facial nerve - #2

parasympathetic nucleus of the facial nerve - #3

nucleus of the solitary tract (sensory nucleus of the facial nerve) - #4

Question 10

Which nuclei contribute to CN VIII?

Where are they located?

Answer 10

Vestibular nuclei - lateral floor of the fourth venticle on either side of the medulla oblongata - 4 nuclei (rostral, lateral, medial, caudal) see fig 12-16A

Cochlear nuclei - (dorsal and ventral)

The trapezoid body is made up of fibers that carry auditory signals from the ventral cochlear nuclei and the dorsal nucleus of the trapezoid body

Question 11

Which nuclei contribute to CN IX?

Where are they located?

Answer 11

Sensory - nucleus of the solitary tract in the medulla (remember that these fibers are carrying signals from the taste buds, etc., to this nucleus)

Motor - nucleus ambiguus in medulla - innervates muscles of pharynx

Paraympathetic nucleus of the glossopharyngeal nerve - in the medulla - innervates parotid and zygomatic salivary glands

Question 12

Which nuclei contribute to CN X?

Where are they located?

Answer 12

Sensory - nucleus of the solitary tract - in the medulla

motor - nucleus ambiguus - muscles of pharynx, larynx, esophagus - in the medulla

parasympathetic nucleus of X - cardiac muscle, smooth muscle in esophagus and gut - in the medulla

Question 13

Another pic with nuclei

don’t panic, you don’t have to memorize all of this, it’s just to give you an idea of which nerves might be affected if different parts of the brain are lesioned

Answer 13

Question 14

Which nuclei contribute to CN XI

Answer 14

Cranial root: Nucleus ambiguus

Spinal root: motor nucleus of the accessory nerve

Question 15

Identify the foramina - also be able to ID the cribitform plate, canal for the trigeminal nerve, internal acoustic meatus, jugular foramen, hypoglossal foramen and tympano-occiptal

Answer 15

See pages 144-145 for things not labeled here

3. ethmoid foramen
4. optic canal
5. orbital fissure
6. rostral alar foramen
7. caudal alar foramen
8. oval foramen

Question 16

Be able to identify the facial canal - remember they had a red string going through it - see back of notecard

Answer 16

string is inserted into the stylomastoid foramen to reach the area where the facial canal is separated from the middle ear by thin connective tissue

see Fig 12-9 and 19-1

Question 17

Run the neuro-dog program to check for palpebral and 3rd eyelid relfexes if these nerves are lesioned:

CN V, CN VI, CN VII - do them one at a time

Answer 17

If CN V is lesioned - no palpebral reflex, corneal relfex or 3rd eyelid response - on same side as lesion

If VI is lesiond - no 3rd eyelid reflex, medial strabismus - same side as lesion

If VII is lesioned - no blink, no palbebral reflex, no corneal reflex - same side as lesion

Question 18

See page 187 and review the reflex circuits involved for palpebral, corneal, and tearing reflexes

Question 19

Identify the nuclei

Answer 19

A. pontine sensory nucleus of the trigeminal nerve in the pons

B. Motor nucleus of the trigeminal nerve

C. Motor nucleus of the facial nerve in the rostral medulla

Remember that they lie within the brain stem, not on the surface as illustrated in these pics

Question 20

Answer 20

Structure - cerebellum

space - fourth ventricle

Question 21

ID these structures

Answer 21

1. trigeminal nerve
2. motor nucleus of the trigeminal nerve
3. pontine sensory nucleus of the trigeminal nerve

Question 22

Explain clinical problems associated with lesion a or lesion b

Answer 22

Lesion a - ophthalmic innervates (sensory) the upper eyelid, eyeball, lacrimal gland, nasal mucosa - important in sneezing response to irritation of mucosa

lesion b - mandibular nerve affected - muscles of mastication paresis or paralysis, no contraction of tensor tympani in response to loud sounds. Loss of sensory innervation to oral cavity, lower lip. lower teeth, nasal passage, rostral 2/3 of the lingual mucosa

see page 165 for dermatome

Question 23

The right eye does not blink. Furthermore, when the right medial canthus is touched, the right eye fails to close. What is wrong with this dog?

Answer 23

The right facial nerve is damaged (or the motor nucleus of the facial nerve)

Negative palpebral relfex could point to a trigeminal nerve (ophthalmic) injury, since they would not feel you toching their medial canthus.

Question 24

Both eyes blink, but touching the right medial canthus fails to induce blinking. Where is the lesion?

Answer 24

Pointine sensory nucleus of CN V or on the ophthalmic nerve (on the right side)

Since the dog can blink, we know it is not the facial nerve that is damged. Lack of palpebral reflex points to lack of sensory innervation to the medial canthus in this instance.

Question 25

Where might the lesion be when there are neither corneal nor palpebral reflexes on the left side?

Answer 25

nerves involved in corneal reflex: ophthalmic nerve (pontine sensory nucleus of CN V) + abducent nerve (motor nucleus of CN VI) + facial nerve (motor nucleus of CN VII) (facial b/c dog will blink in response as well as retract eyeball)

nerves involved in palpebral reflex: ophthalmic (pontine sensory nucleus of CN V) + facial nerve (motor nucleus of CN VII)

If neither are present, the lesion could be in the left pontine sensory nucleus of the trigeminal nerve -most likely

Question 26

Touching the nose usually triggers the animal to pull back the head. If the animal shows no problem moving the head, but does not respond to touching the nose, what nerve(s) could be injured?

Answer 26

Maxillary branch of the trigeminal nerve, or the pontine sensory nucleus of the trigeminal nerve (see pg 169)

Lesions of maxilary nerve interfere with ipsilateral sensation of the maxillary area

Question 27

Where might the lesion be in a dog that shows a lateral deviation of the tongue to the left?

Answer 27

Motor nucleus of the hypoglossal nerve or in the hypoglossal nerve itself.

Remember that this one is kind of weird - If the lesion is early, the tongue will deviate to the normal side in a resting or panting dog, but to the lesiond side if the dog licks.

If the lesion is chronic, the tongue will deviate to the lesioned side whether the dog is just resting or licking.

Question 28

When a meningioma involves the orbital fissure, what clinilcal signs would you expect to see?

Answer 28

Nerves that run through orbital fissure:

Oculomotor, abducent, trochlear, ophthalmic branch of trigeminal

Oculomotor damage: ventrolateral strabismus, ptosis, puillary dilation

abducent damage: medial strabismus, lack of third eyelid response

trochlear damage: extortion of the ipsilateral eye - very dificult to diagnose in dog - remember that if the nerve is damaged at the point where it exits the skull, it’s ipsilateral, but if it’s damaged at the motor nuclues of CN IV, it will be contralateral

ophthalmic damage: lack of corneal and palpebral reflex