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Visual Neuroanatomy Efferent Pathways

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Presentation on theme: "Visual Neuroanatomy Efferent Pathways"— Presentation transcript:

1 Visual Neuroanatomy Efferent Pathways
Vivek Patel, MD University of Ottawa Eye Institute Neuro-Ophthalmology

2 Visual Neuroanatomy Afferent – eye to brain Pupillary reflex arc
Efferents – eye movements

3 Extra-Ocular Muscles

4 Infranuclear pathways

5 CN III Innervates Levator, inferior oblique & all recti except lateral rectus Projects ventrally Enters cavernous sinus after crossing PCOM

6 CN III Injuries Categorized by age Older Adults Children Young Adults
Congenital AVM Tumor Young Adults Demyelination Vascular Older Adults Vascular Tumor

7 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


9 IS it nuclear or peripheral ?
It must be nuclear if Bilateral CN III without ptosis Unilateral CN III with bilateral ptosis BUT Complete bilateral CN III Bilateral ptosis May be either!

10 CN IV Nucleus just caudal and dorsal to III
Innervates Contralateral superior oblique Exits brainstem dorsally Longest intracranial course


12 CN IV injuries Intrinsic Trauma Tumor Demyelination Vascular
Medulloblastoma Ependymoma Metastatic Demyelination Vascular Congenital ( high vertical vergence amplitudes and objective excyclotorsion only) Bilateral: V-pattern esotropia and excyclotorsion greater than 15 degrees. Resultant compensatory head position?

13 CN IV injuries Extrinsic Tumor Hydrocephalus / Aqueductal stenosis
Pinealoma Metastatic Hydrocephalus / Aqueductal stenosis

14 Skew Deviation? Supranuclear cause of vertical misalignment
Does not necessarily obey the 3-step test Ipsilateral intorsion (not extorsion as in IV palsy) Interruption of otolith-ocular pathway at some point along it’s course

15 Skew deviation - OTR Vestibulo-cerebellar: Midbrain:
Ipsilateral head tilt Ipsilateral hypotropia Excyclo of hypo eye, incyclo of hyper eye Midbrain: Contralateral head tilt Ipsilateral hypertropia Excylo of hypo eye, incyclo of hyper eye


17 Look for a lesion in: cerebellum Pons midbrain

18 Normal counter-roll R IV palsy Ocular tilt rxn (skew)


20 CN VI Innervates ipsilateral lateral rectus
Interneurons to contralateral medial rectus via MLF Runs near: CN VII MLF and PPRF Vestibular Nuclei Peduncle


22 CN VI Origin: ponto-medullary junction Projects ventrally along clivus
Tethered at apex of the petrous bone by petroclinoid ligament Enters Cavernous sinus


24 CN VI Injuries Vascular Demyelination Trauma Tumor
Anterior inferior cerebellar or paramedian perforators Demyelination Trauma Tumor

25 Cavernous Sinus Site of multiple cranial nerve palsies Vascular Tumor
Idiopathic Tolosa-Hunt

26 Supranuclear control

27 Internuclear Pathways

28 Paramedian Pontine Reticular Formation
Horizontal Gaze center Initiates horizontal eye movements Bilateral, within Pons Projects to ipsilateral CN VI nucleus Lesions of the PPRF cause ipsilateral gaze palsies PPRF lesions do not affect oculocephalic & caloric reflexes


30 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. Trochlear nerve and otolith ocular pathways also use the MLF

31 Vertical Gaze Rostral Interstitial nucleus of the MLF (riMLF) (gaze initiation) Interstitial Nucleus of Cajal (INC) (gaze holding) INC riMLF

32 Upgaze Lateral riMLF projects to contralateral inferior oblique and superior rectus sub-nuclei Remember Superior Rectus fascicle decussates


34 Downgaze Medial riMLF projects downward to ipsilateral superior oblique and inferior rectus sub nuclei Remember the CN IV fascicle decussates Vertical gaze is initiated by Bilateral activation of the riMLF and INC.


36 Alternating cover testing
Cover / uncover testing Quantifying a deviation

37 Name that lesion


39 Benedikt’s Involves Red Nucleus Ipsilateral CN III
Contralateral involuntary movements


41 Weber’s Involves Cerebral peduncle Ipsilateral CN III
Contralateral Hemiparesis




45 PPRF lesion Ipsilateral gaze palsy
Provides the supranuclear input to the abducens nuclear complex. Isolated PPRF lesion will preserve the oculocephalic and caloric reflexes.


47 PPRF & Nuclear sixth Ipsilateral Gaze palsy with
Abnormal oculocephalic and caloric testing


49 1 and ½ syndrome Lesion of PPRF, CN VI nucleus, MLF
Ipsilateral gaze palsy with ipsilateral INO

50 Remember Know the anatomy and you know the lesion.

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