The Visual and the occulo-motor system

Netta Levin MD PhDfMRI unit ,Department of

NeurologyHadassah Hebrew-University

Hospital Jerusalem, Israel

Visual Neuroanatomy

• Afferent – eye to brain

• Pupillary reflex arc

• Efferents – eye movements

Visual Neuroanatomy

• Afferent – eye to brain

• Pupillary reflex arc

• Efferents – eye movements

C.N.Ⅲ,Ⅳ&Ⅵ : Ocular nerves

CN III: Oculomotor nerve CN IV: Trochlear nerve CN VI :Abducens nerve

•Visual inspection: ocular alignment, lids •Smooth pursuits •Saccades •Nystagmus •6 cardinal directions of gaze

C.N.Ⅲ,Ⅳ&Ⅵ : Ocular nerves

Extraocular movements (H and X)

Extra-Ocular Muscles

CN III

• Innervates Levator, inferior oblique & all recti except lateral rectus

• Projects ventrally • Enters cavernous

sinus after crossing PCOM

CN III Subnuclei

All subnuclei are ipsilateral EXCEPT• Levator subnucleus forms a fused central

nucleus• Superior rectus subnuclei decussate to innervate

contralateral superior rectus muscle

IS it nuclear or peripheral ?

It must be nuclear if• Bilateral CN III without ptosis• Unilateral CN III with bilateral

ptosisBUT• Complete bilateral CN III• Bilateral ptosisMay be either!

CN IV

• Nucleus just caudal and dorsal to III

• Innervates Contralateral superior oblique

• Exits brainstem dorsally

• Longest intracranial course

CN VI

• Origin: ponto-medullary junction• Projects ventrally• Innervates ipsilateral lateral rectus

Cavernous Sinus

• Site of multiple cranial nerve palsies

• Vascular• Tumor• Idiopathic

– Tolosa-Hunt

Supranuclear control

Supranuclear control

Internuclear Pathways

• PPRF :Paramedian Pontine Reticular Formation

• MLF : Medial longitudinal fasciculus

Paramedian Pontine Reticular Formation

• Horizontal Gaze center– Initiates horizontal eye movements

• Projects to ipsilateral CN VI nucleus• Lesions of the PPRF cause ipsilateral gaze

palsies

MLF• Midbrain to cervical spine• Composed of interneurons: ipsilateral CN VI to

contralateral CN III.• fascicle for horizontal gaze and vertical gaze that

connects the VI and III nuclear complexes.

Damage to the MLF

Damage to the MLF+PPRF

Visual Neuroanatomy

• Afferent – eye to brain

• Pupillary reflex arc

• Efferents – eye movements

• Pupillary function - Light reflex (C.N.Ⅱ&Ⅲ)

• Dim lights • Fix gaze on opposite wall to eliminate effects

of accommodation • Shine bright light obliquely into each pupil • Look for both direct (same eye) and

consensual (opposite eye) reaction • Record pupil size and shape

PupilsPupils

1st Order – Retina to Pretectal Nucleus in B/S(at level of Superior colliculus)2nd Order – Pretectal nucleus to E/W nucleus(bilateral innervation!)3rd Order – E/W nucleus to Ciliary Ganglion4th Order – Ciliary Ganglion to Sphincterpupillae (via short ciliary nerves)

• Pupillary function

• Normal pupils are equal in size and shape and are situated in center of iris

• Pupillary size varies with intensity of ambient light, but at average intensity is ~3-4 mm

-Miosis < ~2 mm -Mydriasis > ~5 mm -Anisocoria = pupillary asymmetry

Constricted (mioisis)• Sympathetic

(pupillodilator) denervation

• DrugsPilocarpineMorphine

Dilated (mydriasis)• Parasympathetic(pupilloconstrictor) denervation

•Lesion of the third CN•DrugsAtropineCocaine

• Pupillary function

Visual Neuroanatomy

• Afferent – eye to brain

• Pupillary reflex arc

• Efferents – eye movements

• Visual acuity • Visual fields • Fundoscopy • Afferent limb of pupillary function

C.N.Ⅱ Optic: vision

Hold card at comfortable reading distance • Cover 1 eye • Glasses on (looking for optic nerve lesion, not refractive error)

C.N.Ⅱ Optic: vision

• Visual acuity

C.N.Ⅱ Optic: vision

• Visual fields

C.N.Ⅱ Optic: vision

• Fundoscopy

Optic Optic radiationradiation

Occipital Occipital callosalcallosal

Optic Optic tracttract

Optic Optic nervenerve

How do we divide the visual cortexinto separate areas?

• Retinotopic mapping

• Functional signature

Visual cortex

How do we divide the visual cortexinto separate areas?

• Retinotopic mapping

• Functional signature

Visual cortex

Retinotopic organization of visual areas.

Visual stimuli

Polar stimuli

Eccentricity mapping: Foveal to Peripheral vision

anterior posterior

V1

Retinotopic mapping

Eccentricity mapping

Lesions in the visual pathways

Retinal damage

Macular degeneration

How do we divide the visual cortexinto separate areas?

• Retinotopic mapping

• Functional signature

Visual cortex

There are many visual centers Two Visual streams

Functional mapping

Faces vs. Places processing activationFunctional mapping

Lesions in the visual pathways

Cortical damage

Prosopagnosia

Prosopagnostic patient

Activation within face related region

Activation within place related

region

Visual ImpairmentsVisual Impairments

• Young man presented with the complaint that he cannot see to the left or the right sides of his visual fields while looking straight ahead.

Monocular - Binocular

Pre–chiasmatic – monocularChiasmatic / Post-chiasmatic - binocular

Non-congruent inferior binocular field defects

Congruent partial hemianopia

Congruency – Incongruency

Posterior lesions are more congruent

• 70 Y/O female• Sudden onset – diplopia, dysphagia ->

-> ataxia -> dysarthria -> impaired consciousness

• EXAM – Somnolent, EOM – disconjugate, Gag – decreased, bilateral Babinsky

• Visual Fields?

Spared binocular macular vision

• Bilateral PCA stroke (tip of the basilar)

• Macular Sparing

Localizing the lesionLocalizing the lesion

• Monocular visual field defects indicatelesions anterior to the optic chiasm

• Bitemporal defects are the hallmark ofchiasmal lesions

• Binocular homonymous hemianopia resultfrom lesions in the contralateralpostchiasmal region

• 18 Y/O male

• Sudden onset of blindness (following argument with girl friend)

• Signs of preserved sight

• Visual fields - tunnel vision

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• 60 y/o • Presenting with confusion• Pt denies neurological deficits• On exam –

–No sensory / motor signs–Confabulations to questions–Visual fields to confrontation – uncooperative

• 60 y/o • Presenting with confusion• Pt denies neurological deficits• On exam –

– No sensory / motor signs– Confabulations to questions– Visual fields to confrontation –

uncooperative

– Anton Syndrome – •Cortical blindness • Anosognosia

• 25 y/o female• Headaches for the last month• + Transient visual obscurations

(TVO’s)• + Diplopia (Horizontal? Veritcal?)• + Tinnitus• Referred by Opthalmologist• PMH - Acne

• 25 y/o female

• Headaches for the last month

• + Transient visual obscurations (TVO’s)

• + Diplopia (Horizontal? Veritcal?)

• + Tinnitus

• Referred by Opthalmologist

Dx ?

Idiopatic Increased Intracranial Hypertension

• 25 y.o. female

• New onset of reduced visual acuity and pain with eye movement

• 25 y.o. female

• New onset of reduced visual acuity and pain with eye movement

On examination

• Reduced visual acuity

• Decreased red saturation

• Relative Afferent Pupillary Defect (RAPD)

RAPDRAPD

Optic neuritis is a disease of the optic nerve, causing acute visual loss. Optic neuritis can be clinically isolated but more often can arise as one of the manifestations of multiple sclerosis

VEPVEP

Thanks!