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!
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