DeLahunta Chapter 6 - GSE LMN Cranial nerves Flashcards
Through which foramen do the following cranial nerves exit the cranium/skull?
Optic
Oculomotor
Trochlear
Trigeminal - ophthalmic
Abducens
T-maxillary
T-mandibular
Facial
Vestibulocochlear
Glossopharyngeal
Vagus
Hypoglossal
Optic canal
Orbital fissure (oculomotor, ophthalmic, abducens, trochlear)
Round foramen (maxillary)
Oval foramen (mandibular)
Facial (internal acoustic meatus - inside, outside - stylomastoid foramen)
Vestibulocochlear (internal acoustic meatus, stays inside)
Glossopharyngeal-Vagus-accesory (jugular foramen- tympanococcipital fissure)
Hypoglossal (hypoglossalo canal)
***in some horses there is a trochlear foramen
Which are the extraocular muscles and which their innervation?
1) dorsal rectus –> oculomotor
2) medial rectus –> oculomotor
3) lateral rectus –> abducens
4) ventral rectus –> oculomotor
5) dorsal oblique –> trochlear
6) ventral oblique –>oculomotor
7) retractor bulbi –>abducens
oculomotor n. does also levator palpebrae superioris.
Which lesion causes the strabismus below:
a) ventral or ventrolateral positional?
b) ventrolateral (or lateral) static
c) medial
d) extorsion (dorsolateral)
a) vestibular n.
b) oculomotor n.
c) abducens or pseudoabducens palsy (oculomotor supranuclear centers contralateral)
d) trochlear
What is the cause of congenital medial strabismus, or congenital pendular nystagmus, in oriental breeds?
Increased decussation of fibres at the optic chiasm
What muscles of mastication are innervated by CN V and CN VII?
Also which other muscles CN V innervates?
CN V (trigeminal):
masticatory muscles:
1) masseter
2) temporalis
3) lateral and medial pterygoid
4) rostral digastriculs
plus:
-mylohyoidus m.
-tensor veli palatini m.
CN VII (facial):
masticatory mucle: caudal disastricus
plus muscles of facial expression (mimicry muscles)
What is the cause of middle ear effusion seen with trigeminal nerve dysfunction?
denervation of tensor veli palatini m. responsible for the opening of euthachian tube –> not working –> not draining the middle ear
What are the causes, and respective frequency, of unilateral masticatory muscle atrophy in dogs?
(https://pubmed.ncbi.nlm.nih.gov/30556930/)
Trigeminal pNST 50%, other tumour 20.6%, no findings/idiopathic in 28.6%
What is the reported sensitivity and specificity for the use of 2M antibodies to diagnosed MMM? What are the reasons for false negatives?
(https://vetneuromuscular.ucsd.edu/cases/2012/June/Melmed.MMM.Compend.pdf)
Sensitivity 85-90%, specificity 100%
False negatives due to pre treatment with steroids, or end stage disease
What clinical and neurological signs may be seen with bilateral trigeminal neuritis in dogs?
Clinical:
1) dropped jaw
2) foamy saliva and viscous in the corner
3) sensation of face loss (1/3 of patients) -involvement of GSA
4) Horner syndrome (involvement of postganglionic sympathetic axons joining the ophthalmic nerve)
5) neurotrophic keratitis (if ophthalmic nerve affected)
What clinical signs will be seen with CN VII paralysis in dogs? How does this different in horses and farm animals? [why in horses more obvious facial ptosis - LAOM more important in eye opening in horses!!!! SOS]
dogs:
-facial/lip drop
-absent palpebral/menace response
-neuroparalytic KCS (absent blink or parasympathetic preganglionic neurons to the lacrimal gland of 3rd eyelid …)
-loss of sensation of the ear (auriculopalpebral nerve)
HORSES:
-dropped ear
-dropped eyelashes
-contralateral deviation of the nose because of the unoposed contracture of healthy side
COWS:
-no muzzle deviation
-but dropped ear and eyelid
Why can a nystagmus result in a movement of the upper eyelid?
Because the facial nerve (auriculopalpebral) which innervates LAOM is supposed to have interconnection with vestibular nuclei.
What condition is associated with otitis media/interna in horses, and what is it?
Temporohyoid osteopathy – a bony proliferation of the stylohyoid tympanhyoid and temporal bone. Inflammatory and mechanical hypotheses exist. Prevents any movement of the hyoid apparatus associated with vocalisation or swallowing. Facial paralysis with or without vestibular signs may preceed the fracture caused by otitis, or follow the fracture
What is the reported recovery rate in idiopathic facial nerve paresis? What MRI features are correlated with a worse prognosis for recovery?
(https://pubmed.ncbi.nlm.nih.gov/31867719/)
37.5%
(https://pubmed.ncbi.nlm.nih.gov/33942951/)
T2 and T1 pre hyperintensity of the caudal digastricus muscle was correlated (atrophy or enhancement of muscle or nerve enhancement was NOT correlated)
What comprises the nucleus ambiguus?
The GSE cell bodies of CN IX, X and XI
What are the two most common signs of guttural pouch mycosis? What area is most frequently affected and what neurological structures are located in this area?
Dysphagia and epistaxis
The dorsocaudal medial compartment is most commonly affected, which contains the pharyngeal branches of CN IX and X
What laryngeal muscle does the recurrent laryngeal nerve NOT innervate? What muscle is responsible for adduction of the vocal folds?
1) Cricothyroid m
2) Cricoarytenoideus dorsalis m
What does the trochlear nerve innervate and what is unique about this cranial nerve?
Within the periorbita, the trochlear neurons innervate the dorsal oblique muscle. This is the only cranial nerve with GSE neurons that innervates a muscle solely on the side opposite from its nucleus.
Describe the anatomy behind the vestibulo-ocular reflex.
Moving the head stimulates the sensory receptors in the inner ear that are innervated by the vestibular portion of cranial nerve VIII. Impulses are relayed into the vestibular nuclei in the medulla and then passed rostrally via the medial longitudinal fasciculus to the abducent, trochlear, and oculomotor nuclei. As the animal’s head is moved to the right, both eyes will exhibit a rapid movement, a jerk, toward the right. This is a normal right nystagmus. As the head is moved back to the left, both eyes will jerk to the left, which is a normal left nystagmus. In neuroanatomic terms, when the head is moved to the right, the right eye will jerk to the right via contraction of the lateral rectus innervated by the abducent nerve, and at the same time, the left eye will jerk to the right via the contraction of the medial rectus innervated by the oculomotor nerve. When the head is swung back to the left, the opposite innervations and muscles will be activated. This action tests the function of cranial nerves III and VI as well as the vestibular nerve (VIII) and the pathway of the medial longitudinal fasciculus through the brainstem. These are conjugate eye movements related to the movement of the head and have nothing to do with vision.
What does a lesion of the abducent neuron cause clinically?
Lesions of the abducent neurons cause paralysis of the lateral rectus and retractor bulbi muscles. Loss of the lateral rectus innervation results in a medial strabismus
