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Ophthalmology > Neuro-ophthalmology > Flashcards

Neuro-ophthalmology Flashcards

1
Q

What are the cranial nerves with ophthalmic implications?

A 
CN II - Optic
CN III - Oculomotor
CN IV - Trochlear
CN V - Trigeminal 
CN VI - Abducens
CN VII - Facial
CN VIII - Vestibulocochlear
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2
Q

What does the optic nerve do?

A

Vision

PLR

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3
Q

What does oculomotor nerve do?

A
  • Motor to D, M, V rectus muscles
  • Motor to ventral oblique muscles
  • Motor to levator palpebrae superioris
  • PS innervation to pupillary and ciliary constrictor muscle
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4
Q

What does the trochlear nerve do?

A

Motor to dorsal oblique muscle

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5
Q

What does the trigeminal nerve (CN V) do? What branch does this?

A

Ophthalmic branch:

  • corneal and conjuctival sensation
  • skin sensation of medial region of eyelid

Maxillary branch:
- skin sensation of lateral region of eyelids

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6
Q

What does the abducens nerve (CN VI) do?

A
  • Motor to lateral rectus muscle
  • Motor to retractor bulbi muscles
  • Sympathetic innervation to muscles of cat 3rd eyelid
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7
Q

What does the facial nerve do?

A
  • Motor to orbicularis oculi muscle (closes eyelids)

- PS innervation to lacrimal gland

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8
Q

What does the vestibulocochlear nerve (CN VIII) do?

A
  • Sensory for hearing, balance, and ocular motility
  • Position with regard to gravity
  • Keeps body, including eyes, aligned in space
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9
Q

What is the visual pathway?

A
  1. photon of light passes through media of eye
  2. hits inner layer of retina
  3. strikes visual pigments in photoreceptor disks (rods and cones)
  4. converted to electrical impulse
  5. relayed to bipolar cells
  6. relayed to ganglion cells whose axons form optic nerve
  7. crosses over with contralateral optic nerve @ optic chiasm (decussation)
  8. terminate in lateral geniculate nucleus
  9. optic radiations terminate in visual cortex of occipital lobes (cerebrum)
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10
Q

T/F

If the animal is blind, there is no PLR

A

False

~ 20% of fibers of optic tract diverge b/f reaching lateral geniculate nucleus and are involved in generating PLR

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11
Q

Percentage of decussation varies among species. What is the percentage in cats, dog, cow, horse, sheep, pigs, fish, birds and amphibians?

A

65% - cats
75% - dogs
90% - cow, horse, sheep, pig
100% - fish, bird, reptile

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12
Q

What cranial nerves are involved in the PLR?

A

CN II and CN III

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13
Q

what nucleus in the brain is involved in the PLR? Visual pathway?

A

PLR - pretectal nucleus and PS nucleus of CN III

Visual pathway - lateral geniculate nucleus

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14
Q

What is a photopic versus scotopic exam?

A

Photopic - observe and compare pupil size in diffuse room light

Scotopic - observe and compare pupil size in darkened room

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15
Q

What most commonly causes abnormal PLR?

A

Pupillary function abnormality

  • iris atrophy
  • posterior synechia
  • uveitis
  • lens luxation
  • glaucoma
  • atropine administration
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16
Q

Characteristics of afferent arm lesions of the PLR

A
  1. pupil will dilate maximally and symmetrically
  2. visual deficits if part of afferent arm is also involved with visual pathway (retina to LGN)
  3. unilateral - anisocoris (side depends on if lesion is rostral or caudal to optic chiasm)
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17
Q

When may visual deficits be seen with an abnormal PLR?

A

If part of the visual pathway that is also involved in the PLR pathway is damaged (retinal to LGN)

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18
Q

Characteristics of efferent arm lesion of PLR (CNIII)

A
  • Uncommon
  • No vision loss
  • Almost always unilateral
  • Injured side has abnormal PLR regardless of eye stimulated (direct or conscensual deficit)
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19
Q

T/F

Isolated efferent arm lesions of the PLR are NEVER associated with vision loss

A

True - as long as they are isolated efferent arm lesions

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20
Q

What is the afferent arm of the menace response?

A
  • Retina
  • Optic nerve
  • Visual tract
  • Visual cortex
21
Q

What is the efferent arm of the menace response?

A
  • Facial nerve
22
Q

What nerves are associated with the menace response?

A

CN II and CN VII

23
Q

If you see a deficit in menace response, what reflex should you check before saying it is truly a menace deficit? Why?

A

Palpebral reflex

Want to make sure CN VII is working and animal can functionally blink

24
Q

What cranial nerves are related to the Dazzle reflex?

A

CN II and CN VII

25
Q

What is the afferent arm of the dazzle reflex?

A

Retina
Optic nerve
Visual tract
Rostral colliculus

26
Q

T/F

You need to see in order to have a dazzle reflex

A

False

27
Q

What is the efferent arm of the dazzle reflex?

A

Facial nerve (CN VII)

28
Q

If you have a dazzle reflex what does this tell you?

A

Doesn’t mean they can see. It does mean there is an intact retina, optic nerve, and visual tract

29
Q

What cranial nerves are associated with the palpebral reflex?

A

CN V and CN VII

30
Q

Afferent arm of the palpebral reflex?

A

Ophthalmic branch of CN V (skin of med canthus)

Maxillary branch of CNV (skin of lat canthus)

31
Q

Efferent arm of the palpebral reflex?

A

Contraction of orbicularis oculi muscle (CN VII)

32
Q

What cranial nerves are associated with the corneal reflex?

A

CN V, CN VI, and CN VII

33
Q

Afferent arm of corneal reflex?

A

Ophthalmic branch of CNV

34
Q

Efferent arm of corneal reflex?

A
  • Contraction of orbicularis oculi m. (CN VII)

- Eyelid closure and contraction of retractor bulbi muscles (CNVI) –> Retraction of the globe

35
Q

What cranial nerves do we assess with the vestibulo-ocular reflex?

A

CN VIII
CN III
CN IV
CN VI

36
Q

Afferent arm of the vestibulo-ocular reflex?

A

CN VIII

semicircular canals sense linear acceleration in response to head rotation

37
Q

Efferent arm of the vestibulo-ocular reflex?

A

CN III, IV, and VI

equal and conjugate eye movements

38
Q

What is congenital anomaly in Siamese cat?

A

wiring of the visual pathway is not normal –> inappropriate decussation of fibers

39
Q

There are three components to the sympathetic innervation to the eye… what are they?

A
  1. Central neuron: hypothalamus to T1-T3
  2. Preganglionic neuron: paravertebral sympathetic chain to cranial cervical ganglion
  3. Postganglionic neuron: cranial cervical ganglion through middle ear to orbit
40
Q

What does the postganglionic neuron innervate in the sympathetic innervation to the eye?

A

iris dilator muscle

41
Q

What are central (1st order) causes of Horner’s syndrome?

A
  • cervical spine lesions
  • Neoplasia
  • Embolic infarct, disk compression
42
Q

What are preganglionic (2nd order) causes of Horner’s syndrome?

A
  • Brachial plexus avulsion
  • anterior mediastinal lymphosarcoma (cats)
  • Neck injuries (misplaced injections in equine)
43
Q

What are postganglionic (3rd order) causes of Horner’s syndrome?

A
  • Otitis media or interna, tumors
  • Orbital tumors
  • Guttural pouch disease (equine)
44
Q

What are the ocular structures innervated by sympathetic nerves?

A
  • Iris dilator muscle
  • Muller’s muscle (elevates upper eyelid)
  • Muscularis orbitalis
  • Smooth muscle to nictitating membrane (retracts it)
45
Q

How can you relate the clinical signs to anatomy of eye controlled by sympathetic NS?

A
  • Miosis: loss of dilator mm. function
  • Ptosis: Mueller’s mm. paralysis
  • Enophthalmos: loss of tone from muscularis orbitalis
  • Protrusion of nictitans: loss of smooth mm. tone to nictitans and enophthalmos
46
Q

What are you thinking of if there is vision loss and absent PLR?

A

Vitamin A deficiency

47
Q

What are you thinking if there is vision loss with intact PLR?

A
  • Polioencephalomalacia
  • Lead poisoning
  • Thromboembolic meningoencephalitis
  • Listeriosis
  • Ketosis and hypoglycemia
48
Q

What are some causes of facial nerve paralysis in large animals?

A
  • Guttural pouch infection
  • Temporohyoid osteopathy
  • Trauma/ prolonged recumbency
  • fractures of stylohyoid, petrous temporal bone, or ramus of mandible
  • Inner ear disease
  • EPM

Ophthalmology (5 decks)

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