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| | ===[[Face Sensation]]=== | | ===[[Face Sensation]]=== |
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| − | * Nerve fibres giving sensation to the face are carried in cranial nerve V - the trigeminal nerve.
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| − | ** The trigeminal nerve provides sensory innervation to:
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| − | *** The skin of the face
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| − | *** The ears
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| − | *** The nasal mucosa
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| − | *** The cornea
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| − | ** There are three divisions of the trigeminal nerve
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| − | *** The mandibular branch
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| − | *** The maxillary branch
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| − | *** The opthalmic branch
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| − | * Facial sensation is tested by observation for an avoidance response or reflex movement following stimulation.
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| − | ** All the divisions of the trigeminal nerve should be tested. This is achieved by:
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| − | *** Stimulation within the nostrils
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| − | *** Stimulation within the ears
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| − | *** Stimulation between the mandibles
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| − | *** Testing the corneal reflex.
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| − | ***# Pressure is exerted on the corneal surface through the eyelid.
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| − | ***# The opthalmic branch of the trigeminal nerve provides sensory (afferent) input.
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| − | ***# Efferent signals are sent via the abducens nerve (CN VI)
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| − | ***# The retractor oculi muscle retracts the eye
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| − | ====Masticatory muscles====
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| − | * The mandibular branch of the trigeminal nerve carries motor fibres.
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| − | ** It is the only division of the trigeminal nerve that does so.
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| − | * The muscles of mastication are innervated by these fibres.
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| − | ** The masseter and temporalis muscles are particulaly influenced by the mandibular brach of the trigeminal nerve.
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| − | *** These muscles of mastication are also the easiest to assess.
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| − | *** These muscles should be closely examined for signs of atrophy.
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| − | **** '''Atrophy of the temporalis and masseter muscle indicates damage to the mandibular branch of CN V.'''
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| − | ====Facial Expression====
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| − | * The muscles of facial expression are innervated by branches of cranial nerve VII - the facial nerve.
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| − | * The facial nerve also carries the parasympathetic supply to the lacrimal glands.
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| − | ** Horses with facial nerve dysfunction are therefore prone to corneal ulceration, due to :
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| − | *** An inability to blink
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| − | *** Poor or absent tear production
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| − | =====Facial Nerve Dysfunction=====
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| − | * Facial nerve dysfunction is common in the horse.
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| − | * It is readily identified by one or more of the following:
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| − | ** A lip droop
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| − | ** Muzzle deviation
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| − | *** Deviation is towards the normal side.
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| − | ** An ear droop
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| − | * Early or mild dysfunction may be reflected by:
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| − | ** Slight changes to nostril size
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| − | ** Nostril flare
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| − | ** Reduced ear movements in response to audible stimuli
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| − | * The branch of CN VII supplying the muzzle and nostrils crosses the vertical mandibular ramus and the surface of the masseter muscle.
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| − | ** A lesion to that side of the face, for example a kick, may cause signs confined to the nose.
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| − | ** Alternatively, a more central lesion will give both ear and nostril signs.
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| − | =====The Palpebral Reflex=====
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| − | * The palpebral reflex examines the function of both CN V (afferent) and CN VII (efferent).
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| − | * The reflex is elicited by lightly touching the eyelids and watching for reflex closure.
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| − | [[Category:Cranial Nerve Examination - Horse]]
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| | ===[[Vestibular System Examination]]=== | | ===[[Vestibular System Examination]]=== |