demystifying the neuro-ophthalmologic exam

SATURDAY NOVEMBER 11, 2017

TODD M. BISHOP, DVM, DACVIM (N)

NEUROLOGY & NEUROSURGERY

UPSTATE VETERINARY SPECIALTIES

DEMYSTIFYING THE NEURO-

OPHTHALMOLOGIC EXAM

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Pupillary control

Visual pathways

Ocular movements

Eyelid innervation

Lacrimation

Anatomic localization

Case examples

LECTURE OUTLINE

11/14/2017CE FALL 2017 | DEMYSTIFYING THE NEURO-OPHTHALMOLOGIC EXAM

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Like every reflex there is …

Sensory (Afferent) component

Motor (Efferent) component

THE PLR


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AFFERENT ARM OF PLR

R= retina

II= optic nerve

OC= optic chiasm

OT= optic tract

PTN= pretectal nucleus

LGN= lateral geniculate nucleus

PSN= parasympathetic nucleus of CN III

III= oculomotor nerve

CG= ciliary ganglion

SCN= short ciliary nerve

R

II

OC

OT

PTNLGN


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CHIASMAL DECUSSATION

Primates=50%

Feline=65%

Canine=75%

Equine, bovine, porcine=80-90%


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FATE OF THE POST-CHIASMAL OPTIC TRACT

20% of fibers synapse in PTN to complete PLR

80% of fibers synapse in LGN bound for the visualcortex

20%80%

PTNLGN


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EFFERENT ARM OF PLR

R= retina

II= optic nerve

OC= optic chiasm

OT= optic tract

LGN= lateral geniculate nucleus

PTN= pretectal nucleus

PSN= parasympathetic nucleus of CN III

III= oculomotor nerve

CG= ciliary ganglion

SCN= short ciliary nerve


PTN

PSN

III

CG

SCN

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GEE WIZ ….

Dogs have 5-8 SCNs

Cats have 2 SCNs:

Nasal and malar branches

Only carry PSN fibers

“D-shaped” pupil


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Pupillary constriction

Parasympathetically mediated (Ach)

Pupillary dilation

Sympathetically mediated (norEpi)

IRIDIAL MUSCULATURE


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SYMPATHETIC

INNERVATION

#1

#2#3

Very uncommon!

#4


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HORNER SYNDROME

Miosis

Ptosis

Enophthalmus

Nictitans protrusion

Episcleral injection


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2.5% phenylephrine

Pupil dilation

resolution of ptosis

Retraction of nictitans

5-8 minutes

Lesion in 2nd LMN

0.001% Epinephrine

Pupillary dilation

20 minutes if 2nd LMN affected

38-40 minutes if 1st LMN affected

PHARMACOLOGIC TESTING: SYMPATHETIC

DISTURBANCES


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0.5% physostigmine

Indirect PNS

UMN lesion → rapid constriction

LMN lesion → no constriction

Normal eye → constriction w/ in 40-60 mins.

2% pilocarpine

Direct PNS

Rapid pupil constriction with either UMN or LMN lesion

Normal eye constricts w/ in 20 mins.

A rule out for iris atrophy (would not constrict)

PHARMACOLOGIC TESTING: PARASYMPATHETIC

DISTURBANCES


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Easy to see mydriasis in bright sunlight (ie. A cat in a window sill).

Easy(ish) to see miosis in the dark.

But what about asymmetric pupils in ambient room light?

Which pupil is affected?

Is one pupil too small or is the other too big?

ANISOCORIA


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If you think a pupil is too big, put a bright light into that eye and observe for complete constriction.

If you think a pupil is too small, bring the patient into the dark and observe for complete dilation.

KEEP IT SIMPLE …



USE A BRIGHT LIGHT!

Non-

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Mydriasis

Oculomotor nucleus/nerve lesion

Iris atrophy

Glaucoma

Posterior synechia

Pharmacological blockade

Miosis

Horner syndrome

Supranuclear inhibition

Uveitis

Keratitis

Posterior synechia

ANISOCORIA


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Is there a direct response to bright light (directed into the temporal retina)

Reaction? Complete? (sluggish?)

Is there a consensual (indirect) response when light in shown in the fellow eye?

WHEN EVALUATING THE PLR


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DYNAMIC CONTRACTION

ANISOCORIA

anisocoria (direct PLR > indirect PLR)

Occurs in non-primates

due to unequal decussation of fibers

75%25%


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“positive test” occurs when illuminated eye dilates rather than constricts

“Marcus-Gunn pupil”

Unilateral retinal or optic nerve lesion

SWINGING FLASHLIGHT TEST


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PARADOXICAL PUPIL

Central chiasm lesion

Symmetric mydriasis

Direct and indirect PLR present

Indirect response > direct response !!!


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CEREBELLAR AFFECTS ON PUPILS

Fastigial lesion Contralateral mydriasis

Ipsilateral nictitans protrusion

Interpositus lesion Ipsilateral mydriasis

Contralateral nictitansprotrusion

F

L


I

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LET’S REVIEW

Afferent Arm PLR abnormal

Vision affected

Efferent Arm PLR abnormal

Vision normal

Cortical lesion (after OT splits) PLR normal

Vision affected

R

II

OC

OT

PTNLGN

PSN


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CONSCIOUS

VISUAL PERCEPTION


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Menace response (12 weeks)

Dazzle reflex

Cotton ball drop

Visual placing reaction

Obstacle course

VISUAL ASSESSMENT


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Response NOT reflex

Closure of palpebral fissure +/- globe retraction, head turn

Puppies develops between 10-12 weeks of age

Cortically mediated response

Requires that the entire visual pathway be intact

CereBELLAR lesion may cause IPSILATERAL menace deficits WITHOUT vision loss!

MENACE RESPONSE


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MENACE RESPONSE


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a subcortically mediated “brainstem” REFELX

Palpebral fissure closes in response to bright stimulus

Lids may open then close

Ipsilateral response > contralateral response

DAZZLE REFLEX


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DAZZLE REFLEX


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OCULAR MOVEMENT CONTROL

CN III (Oculomotor) Medial rectus (adduction)

Dorsal rectus (elevation)

Ventral rectus (depression)

Ventral oblique (extortion)

CN IV (Trochlear) Dorsal oblique (intortion)

CN VI (Abducens) Lateral rectus (abduction)

Retractor bulbi (retraction)


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Vestibulo-ocular reflex (VOR)

a.k.a. Doll’s eye or oculocephalic reflex

Corneal reflex (V-VI/VII)

Resting or positional strabismus

TESTING OCULAR MOVEMENTS


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VESTIBULO-OCULAR REFLEX (VOR)

VIII→MLF →III,IV,VI

Move head horizontal to RIGHT

Smooth pursuit LEFT

Saccade beat RIGHT


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CORNEAL REFLEX (V-VI/VII)


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RESTING STRABISMUS


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Afferent innervation

Medial canthus (V-ophthalmic)

Lateral canthus (V-maxillary)

Efferent innervation

Levator palpebrae superioris (III)

Orbicularis oculi (VII)

Muller’s muscles (SNS in Voph)

* lack of input from any of these → PTOSIS

EYELID INNERVATION


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Palpebral reflex (Voph/max → VII)

Corneal reflex (Voph → VII)

Menace response (II → VII)

Dazzle reflex (II → VII)

TESTING EYELID INNERVATION


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LACRIMATION


VII nucleus (PSN)

VII

major pertosal n.

n. of pterygoid canal

pterygopalatine ganglion

Lacrimal n. (Voph) Zygomaticotemporal n. (Vmax)

lacrimal gland

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VII → V


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Schirmer Tear Test (STT)

Tests for neurogenic KCS

Also look for xeromycteria (zē′rō-mik-tē′rē-ă)

Dry nose on the ipsilateral side

TESTING LACRIMATION SYSTEM


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Neuroparalytic keratitis Exposure keratitis due to facial (VII) paralysis Uncommon complication in dogs and cats due to presence of the

nictitans

Neurotrophic keratitis Trigeminal (V) nerve provides trophic factors necessary for corneal health denervation → epithelial degeneration and stromal edema Progressing to desiccation, neovascularization, opacification, ulceration

and even perforation Some eyes may require enucleation

NEUROGENIC KERATITIS


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Generally non-responsive to topical Cyclosporine and Tacrolimus

Oral pilocarpine therapy may be required:

Directly stimulates denervated gland

Use 2% pilocarpine eye drops as follows:

2 drops per 20 lbs body wt. BID w/ food

Inc. dose by 1-2 drops per week until toxicity (V/D) occurs, then back off one step

May require lifelong therapy

TREATING NEUROTROPHIC KCS


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Ask yourself these questions …

Is the pet BLIND (no menace)?

If so which eye?

Is there ANISOCORIA?

If so, which pupil is too big or too small?

Are the PLRs intact?

If so are they intact directly and consensually?

ANATOMIC DIAGNOSIS (ADX)


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LET’S REVIEW AGAIN!


Vision affected


Vision normal


Vision affected

R

II

OC

OT

PT

NLGN

PSN


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UNILATERAL LEFT RETINAL LESION

BLIND? Yes, ipsilateral (OS).

ANISOCORIA? Yes, ipsilateral mydriasis (OS)

PLRs? Light in OS → no constriction OU

Light in OD → constriction OU

* WARNING: PLRs may persist with advanced retinal disease!


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UNILATERAL LEFT OPTIC NERVE LESION

Same findings as unilateral retinal lesion

Positive swinging flashlight test

ADx: retina or optic nerve


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BLIND?

Yes, bilaterally.

ANISOCORIA?

No, but mydriasis OU.

PLRs?

Light in OS → decreased to no response OU

Light in OD → decreased to no response OU

Paradoxical pupil?

ADx: bilateral retina/optic nerve oroptic chiasm


OPTIC CHIASM LESION

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BLIND? Yes, contralateral (OS)

ANISOCORIA? Yes, but subtle mydriasis (OS)

PLRs? Light in OS both constrict but OS

incomplete Light in OD both constrict but OS

incomplete

Swinging flashlight test is Negative

ADx: similar to retina/optic nerve but anisocoria and PLRs less affected


UNILATERAL RIGHT OPTIC TRACT LESION

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BLIND? No, sighted OU

ANISOCORIA? Yes, mydriasis (OS)

PLRs? Light in OS, constriction OD

Light in OD, constriction OD

ADx: efferent ONLY on leftas vision not affected


OCULAR MOTOR NERVE (NUCLEUS) LESION ON LEFT

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BLIND? Yes, contralateral (OS)

ANISOCORIA? No

PLRs? Light in OS, constriction complete

and symmetric OU

Light in OD, constriction complete and symmetric OU

ADx: lesion must be caudal to where OT splits to PTN and LGN on the right side


UNILATERAL RIGHT CORTICAL LESION

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BILATERAL CORTICAL LESIONS

BLIND? Yes, bilaterally (OU)

ANISOCORIA? No

PLRs? Normal OU

ADx: bilateral occipital lobe

DDx: hypoxia, thiamine, lead, storage diseases


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Sig: 3-yr MI Doberman pinscher

CC: dilated left pupil

Hx: duration of 6 days

Neurologic exam:

Normal menace OU

Left pupil widely dilated in room light

Light OS – only OD constricts

Light OD – only OD constricts

No strabismus; slight ptosis & dec. adduction OS

CASE STUDY #1


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CASE STUDY #1

BLIND?

No, sighted OU

ANISOCORIA?

Yes, mydriasis (OS)

PLRs?

Only OD responds

Bonus Info:

Ptosis OS (Lev. Palp. Sup.)

↓ adduction OS (Med. Rectus)

http://www.omconcept.fr


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Anatomic Diagnosis?

left oculomotor n (III) nucleus or nerve

Definitive Diagnosis?

Germ Cell Tumor


CASE STUDY #1

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Sig: 3-yr FI miniature poodle

CC: seizures, abnormal behavior

Hx: 5 generalized seizures over the past week; 3 day progressive lethargy w/ circling and head pressing

Neurologic exam: Profound lethargy, tends to circle to right w/ normal gait; slow

postural reactions on left side

No menace OU, w/ widely dilated pupils OU

Light OS- no response OU

Light OD- initially no response OU, then when light directly medially toward nasal retina, both pupils constrict

CASE STUDY #2


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CASE STUDY #2

BLIND?

Yes, bilaterally

ANISOCORIA?

No, but mydriasis OU

PLRs?

Only in nasal retina OD

www.pamperedpuppy.com


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CASE STUDY #2

Anatomic Diagnosis?

incomplete optic chiasm vs. bilateral optic tract


Pituitary Macroadenoma


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Sig: 8 yr. MI MIXB

CC: acting blind

Hx: Sudden onset of bumping into objects

Neurologic exam:

No menace OU

Both pupils moderately dilated in room light

Light OS – pupils constrict OU

Light OD – pupils constrict OU

Remainder of neuro exam is WNL

CASE STUDY #3


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CASE STUDY #3

BLIND?

Yes, bilaterally

ANISOCORIA?

No, but mydriasis OU

PLRs?

Intact OU


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CASE STUDY #3

Anatomic Diagnosis? bilateral retina/optic nerve >

optic chiasm

Differential Diagnosis? OPTIC NEURITIS

Pituitary Tumor

SARDS


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Sig: 3 yr. MI Collie

CC: seizures

Hx: generalized seizures monthly for past 8 months

Neurologic exam: No menace OS

Both pupils normal size/symmetry in room light

Light OS – no response OU

Light OD – pupils constrict OU

As you swing from OD to OS, OS dilates to original size. Cover OD w/ hand and OS dilates widely.

CASE STUDY #4


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CASE STUDY #4

BLIND?

Yes, blind OS

ANISOCORIA?

OS widely dilated in dark

PLRs?

Only when light in OD

Positive swinging flashlight test (OS dilates in bright light) http://www.aht.org.uk/images/retina6.jpg


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CASE STUDY #4

Anatomic Diagnosis?

left retina or optic nerve


Coloboma (Collie Eye Anomaly-CEA)

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Sig: 10 yr. FS Boxer

CC: depressed, circling

Hx: 1 month progressive Hx of depression, failure to recognize owner and circling to left

Neurologic exam: Depressed

Circling LEFT

RIGHT-sided postural reaction deficits

No menace OD

Normal pupil size, symmetry and reaction to light

CASE STUDY #5


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CASE STUDY #5

BLIND?

Yes, blind OD

ANISOCORIA?

No, symmetric pupils

PLRs?

Normal OU www.kingdomofpets.com


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CASE STUDY #5

Anatomic Diagnosis?

Left prosencephalon (forebrain)


Glial tumor

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Sig: 10 yr. MC MIXB CC: exophthalmia OS Hx: 1 month progressive history of sneezing, intermittent

epistaxis (left nares) and pain on opening jaw Neurologic exam: No menace OS widely dilated pupil OS Light OS- no response OU Light OD- only OD constricts OS difficult to retropulse

CASE STUDY #6


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CASE STUDY #6

BLIND? Yes, blind OS

ANISOCORIA? Yes, mydriasis OS

PLRs? OD constricts but only

directly


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CASE STUDY #6

Anatomic Diagnosis?

left optic (II) andoculomotor (III) nerves


Chondrosarcoma in the LEFT retrobulbar space


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First, ask yourself …

BLIND?

ANISOCORIA?

PLRs?

What is affected?

PLR and vision?

PLR only?

Vision only?

IN SUMMARY …


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Vision affected


Vision normal


Vision affected


ONE LAST TIME …

R

II

OC

OT

PT

NLGN

PSN

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Michael Davidson, DVM, DACVO for providing an outline and some slides for this talk

Alexander De Lahunta, DVM, Ph.D for his spiritual guidance

Amanda Blackburn, DVM, DACVIM for assistance with image acquisition

A SPECIAL THANKS TO …


demystifying the neuro-ophthalmologic exam

Education