JVD 2019 #1 A Salivation Abnormality with Trigeminal Nerve Dysfunction in Dogs Kent

Question 1

in A Salivation Abnormality with Trigeminal Nerve Dysfunction in Dogs Marc Kent JVD 2019- What are the major branches of the trigeminal nerve (CN V)? And their functions?

Answer 1

3 major branches: Ophthalmic, maxillary and mandibular nerves. All 3 provide somatic sensory function to majority of head.
MN nerve also provides somatic motor innervation to muscles of mastication, mylohyoideus & tensor veli pataltini m.
MN branch also provides conduit for postganglionic parasympathetic axons to salivary glands.

Question 2

Clinical signs of trigeminal nerve disease:

Answer 2

Muscle atrophy due to denervation of temporalis & masseter m. (trigeminal & MN nerve branch)
Atrophy of pterygoid m. causes enopthalmos & elevation of third eyelid
Bilateral dysfunction of MN nerve= inability to close mouth (then prehend, chew, etc ‘dropped jaw’)
loss of cutaneous sensation

Question 3

Does the trigeminal nerve provide parasympathetic innervation to the salivary glands?

Answer 3

MN nerve is only a conduit to distribute parasympathetic axons to the salivary glands. Although parasympathetic axons travel along with the mandibular nerve, the trigeminal nerve itself does not, per se, provide parasympathetic innervation.

Question 4

Outline parasympathetic innervation to the mandibular & sublingual glands

Answer 4

Cell bodies for the preganglionic parasympathetic neurons are in parasympathetic nucleus of the facial nerve.
Preganglionic axons course through the facial nerve, where they eventually join with the lingual nerve, a branch of the mandibular nerve, to synapse in the mandibular ganglion or sublingual ganglion. Postganglionic axons innervate the mandibular and sublingual glands, respectively

Question 5

Outline parasympathetic innervation to the parotid & zygomatic glands

Answer 5

cell bodies for the preganglionic parasympathetic neurons are located in the parasympathetic nucleus of the glossopharyngeal nerve.
Preganglionic axons course through the glossopharyngeal nerve to synapse at the otic ganglion.1 Postganglionic axons join with the auriculotemporal nerve, a branch of the mandibular nerve, to innervate the parotid and zygomatic glands.

Question 6

Salivary sign of dysfunction of the trigeminal or MN nerve reported in study?

Answer 6

Accumulation of thick, foamy saliva adhered to the mucosa of the dorsocaudal aspect of oral cavity. With unilateral dysfxn, this accumulates on the ipsilateral area of the parotid & zygomatic duct papilla.

Question 7

Cutaneous sensory loss testing for trigeminal dysfunction

Answer 7

MX nerve= reduced/absent palpebral reflex when stimulating the lateral canthus of eye
Ophthalmic nerve= reduced/absent palpebral reflex with stim of medial canthus of eye &/or reduced/absent response to stimulation of rostral-most nasal septal mucosa
(still maintain menace response & voluntary closure of palpebral fissure)

Question 8

MRI findings in study

Answer 8

11 dogs w MRI of head
5 dogs -unilateral trigeminal nerve enlargement which extended caudally to compress the ipsilateral side of the pons (brain stem)
3 dogs -unilateral trigeminal nerve enlargement within the trigeminal canal, which continued as enlargement of the mandibular nerve with no invasion of the brain stem
2 dogs- bilateral dysfunction-the trigeminal nerve and the mandibular nerve were subjectively enlarged and displayed strong and uniform contrast enhancement
In all unilateral - atrophy and contrast enhancement of the muscles of mastication were present on the side ipsilateral to the affected nerve. Bilateral atrophy and contrast enhancement of the muscles of mastication were present in the 2 dogs with bilaterally enlarged trigeminal nerves. Three dogs had effusion in the tympanic cavity on the side ipsilateral to the affected nerve.