Cognition & Senses 2: Neuro-Ophthalmic Exam Flashcards
CRANIAL NERVE ____, the ____ NERVE controls MOST of the EXTRAOCULAR MUSCLES, except for which 3?
name those 3’s innervation & action!
III, OCULOMOTOR
except for…
1. LATERAL RECTUS = ABDUCENT (CN VI), turns globe AWAY FROM CENTER
- RETRACTOR BULBI = ABDUCENT (CN VI), RETRACTS GLOBE into the ORBIT
- SUPERIOR (DORSAL) OBLIQUE = TROCHLEAR (CN IV) ROTATES/INTORTS THE GLOBE NASALLY
what innervates the the IRIS SPHINCTER muscle?
what ACTION does this cause?
OCULOMOTOR (CN III)
this causes MEIOSIS
what are 2 lesions?
what NERVE likely has a lesion & what does it USUALLY do?
- PUPIL IS DILATED
- eye is LATERALLY DEVIATED (STRABISMUS)
the OCULOMOTOR NERVE, which usually causes CONSTRICTION OF PUPIL & MEDIAL PULL OF EYE
what is the LESION?
what is the NERVE affected & what does it USUALLY do?
lesion = eyes are ROTATED/EXTORTED OUTWARD
TROCHLEAR (CN IV) which usually ROTATES/INTORTS GLOBE MEDIALLY
what is the LESION?
what NERVE is affected & what does it USUALLY do?
lesion = eye is MEDIALLY DEVIATED
ABDUCENT (CN VI) nerve affected because USUALLY PULLS EYE LATERAL/OUT
INTERNAL OPHTHALMOPLEGIA
= definition
what is usually the PRESENTATION? & why?
= when the PARASYMPATHETIC FIBERS of the OCULOMOTOR NERVE (CN III) are DYSFUNCTIONAL/LOSS OF INNERVATION
presents with FIXED, DILATED PUPILS bc CAN NO LONGER CONSTRICT IRIS SPHINCTER MUSCLE in PLR
EXTERNAL OPHTHALMOPLEGIA..
= definition
what PRESENTATION is this usually?
= when the SOMATIC/EFFERENT FIBERS in the OCULOMOTOR NERVE (CN III) are DYSFUNCTIONAL
usually presents as LATERAL STRABISMUS
PALPEBRAL REFLEX
= what is it?
involves WHAT 2 NERVES?
what MUSCLE is moved?
what if this is NOT present?
= LIGHT touch to the EYE eliciting a BLINK
involves…
1. TRIGEMINAL (CN V)
2. FACIAL (CN VII)
the ORBICULARIS OCULI muscle moves!
if this is NOT present, CAN BE HARD TO DETECT OTHER EYE REFLEXES
CORNEAL REFLEX…
= what is it?
what 3 NERVES are involved?
if this is NOT present, animal can be…
= reflex CLOSURE of the LID & GLOBE RETRACTION in response to TOUCHING THE CORNEA
3 nerves?
1. TRIGEMINAL (CN V)
2. ABDUCENS (CN VI)
3. FACIAL (CN VII)
if this is NOT present, animal can be DEAD
NORMAL ordered test for EYE EXAM?
- start with PALPEBRAL REFLEX to see IF THE ANIMAL CAN BLINK
- if so, MOVE TO MENACE RESPONSE
MENACE RESPONSE
why is this NOT a reflex?
= what is it? & what does it TEST in the patient?
what 2 things does the PATIENT require for this to be POSITIVE?
what SPECIES is this less effective in?
NOT a reflex because THIS IS A LEARNED RESPONSE
= reflex CLOSURE OF PALPEBRAL FISSURE & TURNING the HEAD AWAY while ONE EYE IS COVERED; this tests VISION
2 things?
1. NORMAL/POSITIVE PALPEBRAL RESPONSE (ability to blink)
2. INTACT VISUAL CORTEX to SEE
this is LESS EFFECTIVE in CATS
when is the MENACE RESPONSE present in…
puppies/kittens?
foals/calves?
puppies/kittens = 10-12 WEEKS
foals/calves = 5-7 DAYS
DAZZLE REFLEX…
= what is it?
what 2 NERVES does this involve?
= INVOLUNTARY AVOIDANCE REFLEX to a BRIGHT LIGHT shined in the EYE or “SQUINTING”
2 nerves…
1. OPTIC (CN II)
2. FACIAL (CN VII)
PUPILLARY LIGHT REFLEX..
= give an EXAMPLE of DIRECT
= give an EXAMPLE of INDIRECT
–> what could you CALL this?
DIRECT = shining LIGHT into the RIGHT EYE and RIGHT PUPIL CONSTRICTS IN RESPONSE
INDIRECT = shining LIGHT into the RIGHT EYE and LEFT PUPIL CONSTRICTS
–> you could call this POSITIVE INDIRECT PLR RIGHT TO LEFT
list 2 DIFFERENT TESTS we can use for VISION TESTING
–> give example for first one
which is NOT ALWAYS indicative of vision?
- tracking MOVING OBJECTS
–> COTTON BALL for dogs, LASER POINTER for cats - MAZE TEST
the ____ & ____ REFLEX DO NOT help assess ____, but they DO help evaluate INTEGRITY of ______ pathways
PLR, DAZZLE, VISION, NEUROANATOMICAL
if a patient has lost the AFFERENT ARM of CN ___, what 3 clinical eye exam signs should we see?
- VISION LOSS
- NO PLR (direct or indirect)
- NO DAZZLE REFLEX
CN II (OPTIC)
if a patient has lost the EFFERENT ARM of CN ___, what 3 findings should we have? ONE IS NORMAL
- NO VISION LOSS
- ONE eye ALWAYS RESPONDS to PLR & DAZZLE
- OTHER EYE DOES NOT RESPOND
if a patient has lost the CORTICAL pathway of CN ___, what 3 findings should we have? ONLY ONE IS ABNORMAL
- VISION LOSS
- NORMAL PLR
- NORMAL DAZZLE
ANISOCORIA definition?
in this presentation, we need to determine WHICH ___ is ____
what 2 TERMS can we use to describe the eyes?
ANISOCORIA = UNEQUAL PUPIL SIZE
in this presentation, we need to determine WHICH PUPIL is NORMAL
2 terms?
1. MYDRIASIS = DILATED PUPIL
2. MIOSIS = CONSTRICTED PUPIL
if you’re in a LIGHT ROOM and a patient has ANISOCORIA, WHICH pupil is likely ABNORMAL?
the MYDRIATIC or DILATED PUPIL is ABNORMAL
what are 3 main OPHTHALMIC CAUSES of MYDRIASIS?
what are 4 OTHER CAUSES? (some include eye)
3 ophthalmic?
1. OPTIC NEURITIS
2. OPTIC NERVE HYPOPLASIA
3. THIRD NERVE PALSY
4 others?
1. DRUGS (atropine)
2. IRIS ATROPHY
3. COMPLETE RETINAL ATROPHY
4. GLAUCOMA
5. FEAR (especially CATS)
MIOSIS causes? (4)
- UVEITIS
- DRUGS (pilocarpine)
- ORGANOPHOSPHATE TOXICITY
- HORNER’S SYNDROME
what DRUG causes…
MYDRIASIS?
MIOSIS?
MYDRIASIS (dilation of pupil) = ATROPINE
MIOSIS (constriction of pupil) = PILOCARPINE
FACIAL NERVE PARALYSIS…
= definition?
5 clinical signs?
treatment? (3)
= INABILITY to MOVE MUSCLES ON FACE
clinical signs?
1. LOSS OF BLINK (can cause EXPOSURE KERATITIS)
- NORMAL MUSCLE TONE on CONTRALATERAL SIDE
- LIP on AFFECTED SIDE FLACCID
- EAR DROOP
- DRY CORNEA
treatment?
1. LUBRICATE THE CORNEA
2. if CORNEAL ULCER, use TOPICAL ANTIBIOTIC
3. if VERY SEVERE, then TEMPORARY TARSORRHAPY (sew lids shut)
what is GENERALLY normal IOP range in SMALL ANIMALS? (need to include 2 things)
what ALTERNATIVELY could be the range?
15-25 mmHg and WITHIN 5 mmHg of EACH OTHER
can also be 10-25 mmHg
what is the NORMAL SCHIRMER TEAR TEST range in mm/min for SMALL ANIMALS?
15-25 mm/min
what is the BASIC DEFINITION of EXPOSURE KERATITIS? & include why it happens
when you CANNOT BLINK and the CORNEA DRIES OUT & FORMS ULCERS & INFLAMMATION
what is the MOST COMMON ETIOLOGY of FACIAL PARALYSIS in…
dogs?
cats? (2)
what is the prognosis?
dogs = IDIOPATHIC
cats? = IDIOPATHIC MAINLY, also NEOPLASIA
PROGNOSIS is GUARDED, depends on the CAUSE!
what is a CORNEAL ULCER?
when there’s an ABRASION on the CORNEAL SURFACE causing the CORNEAL EPITHELIUM to be GONE
HORNER’S SYNDROME..
= definition?
four clinical signs?
= the LOSS of SYMPATHETIC INNERVATION to the EYE & ADNEXA
clinical signs?
1. MIOSIS
2. ENOPHTHALMOS
3. PROTRUSION of THIRD EYELID
4. PTOSIS (lid is droopy)
why can PTOSIS occur in HORNER’S SYNDROME?
due to LOSS OF INNERVATION to MULLER’S MUSCLE IN UPPER LID
what is the PATHOPHYSIOLOGY for HORNER’S SYNDROME?
(main pathway & 3 subs)
the 3 NEURON PATHWAYS responsible for SYMPATHETIC INNERVATION of EYE & ADNEXA, including…
- a FIRST ORDER/CENTRAL NEURON
- SECOND ORDER/PREGANGLIONIC NEURON (of the CRANIAL CERVICAL ganglion)
- THIRD ORDER/POSTGANGLIONIC NEURON (of the CRANIAL CERVICAL ganglion)
if you have FIRST ORDER/CENTRAL LESION causing HORNER’S SYNDROME…
commonality?
commonality = UNLIKELY unless you have SERIOUS NEUROLOGIC DZ in THALAMUS, BRAINSTEM or MYELOPATHIC DEFICITS
if you have SECOND ORDER/PREGANGLIONIC LESION causing HORNER’S SYNDROME…
commonality?
what 2 STRUCTURES is this SECOND ORDER NEURON close to?
what’s the GANGLION?
commonality = more common than first
2 structures?
1. BRACHIAL PLEXUS
2. CAROTID ARTERY
the GANGLION = CRANIAL CERVICAL GANGLION
if you have THIRDORDER/POSTGANGLIONIC LESION causing HORNER’S SYNDROME…
what 2 STRUCTURES are near this THIRD ORDER neuron?
what 1 clinical sign can be associated with it?
2 STRUCTURES?
1. MIDDLE EAR
2. GUTTURAL POUCH
1 clinical sign?
1. SCRATCHING EARS
how do you DIAGNOSE HORNER’S SYNDROME? (2)
what HAPPENS if the PATIENT HAS HORNER’S due a LESION IN THIRD ORDER NEURON?
diagnosis?
1. give ONE DROP of PHENYLEPHRINE into BOTH EYES which NORMALLY DILATES PUPILS
2. if one eye DILATES in response to phenylephrine in LESS THAN 20 MINUTES, then POSTGANGLIONIC LESION
if there’s a LESION IN POSTGANGLIONIC NEURON causing HORNER’S, then it will be HYPERSENSITIVE to ANYTHING THAT STIMULATES IT (called DENERVATION HYPERSENSITIVITY), so QUICKER THAN NORMAL MYDRIASIS (dilation)
what is the MOST COMMON cause of HORNER’S in….
dogs?
cats? (2)
dogs = IDIOPATHIC
cats?
1. HEAD/NECK TRAUMA
2. EAR ISSUES
HORNER’S SYNDROME in GOLDEN RETRIEVERS…
WHERE is the lesion?
prognosis?
WHERE is the lesion = tends to be a POSTGANGLIONIC/THIRD ORDER NEURON LESION
prognosis = GENERALLY GOOD
