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During a clinical examination, horizontal eye movements (strabismus) or an absent [[Neurological_Eye_Examination_-_Horse#The_pupillary_light_reflex_(PLR)|pupillary light reflex (PLR)]] may indicate a problem.
 
During a clinical examination, horizontal eye movements (strabismus) or an absent [[Neurological_Eye_Examination_-_Horse#The_pupillary_light_reflex_(PLR)|pupillary light reflex (PLR)]] may indicate a problem.
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====Trochlear nerve (IV====
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====Trochlear nerve (IV)====
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The trochlear nerve is part of the cranial nerve group responsible for innervation of the [[Skull and Facial Muscles - Anatomy & Physiology#Facial_Muscles|muscles of the head]]. The trochlear nerve originates from the dorsal midbrain and is a motor nerve. It is composed of '''general somatic efferent fibres''' and is the smallest of the cranial nerves.
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After leaving the dorsal midbrain, its axons decussate (cross) and then run in a rostral direction through the cavernous sinus before exiting the skill via the [[Skull and Facial Muscles - Anatomy & Physiology#Major Foramen and Canals|'''orbital fissure''']].  In the horse, it may also exit via a seperate trochlear foramen.  Finally, it runs to innervate the 'dorsal oblique muscle' muscle of the contralateral eye.
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During a clinical examination, a dorso-lateral strabismus may indicate a problem with this nerve.
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====Trigeminal nerve (V)====
 
====Trigeminal nerve (V)====
 
====Opthalmic nerve (V1)====
 
====Opthalmic nerve (V1)====
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