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Category:Cranial Nerve Examination - Horse (view source)
Revision as of 16:05, 9 March 2011
, 16:05, 9 March 2011no edit summary
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* Nerve fibres giving sensation to the face are carried in cranial nerve V - the trigeminal nerve.
−** The trigeminal nerve provides sensory innervation to:
−*** The skin of the face
−*** The ears
−*** The nasal mucosa
−*** The cornea
−** There are three divisions of the trigeminal nerve
−*** The mandibular branch
−*** The maxillary branch
−*** The opthalmic branch
−* Facial sensation is tested by observation for an avoidance response or reflex movement following stimulation.
−** All the divisions of the trigeminal nerve should be tested. This is achieved by:
−*** Stimulation within the nostrils
−*** Stimulation within the ears
−*** Stimulation between the mandibles
−*** Testing the corneal reflex.
−***# Pressure is exerted on the corneal surface through the eyelid.
−***# The opthalmic branch of the trigeminal nerve provides sensory (afferent) input.
−***# Efferent signals are sent via the abducens nerve (CN VI)
−***# The retractor oculi muscle retracts the eye
−====Masticatory muscles====
−* The mandibular branch of the trigeminal nerve carries motor fibres.
−** It is the only division of the trigeminal nerve that does so.
−* The muscles of mastication are innervated by these fibres.
−** The masseter and temporalis muscles are particulaly influenced by the mandibular brach of the trigeminal nerve.
−*** These muscles of mastication are also the easiest to assess.
−*** These muscles should be closely examined for signs of atrophy.
−**** '''Atrophy of the temporalis and masseter muscle indicates damage to the mandibular branch of CN V.'''
−====Facial Expression====
−* The muscles of facial expression are innervated by branches of cranial nerve VII - the facial nerve.
−* The facial nerve also carries the parasympathetic supply to the lacrimal glands.
−** Horses with facial nerve dysfunction are therefore prone to corneal ulceration, due to :
−*** An inability to blink
−*** Poor or absent tear production
−=====Facial Nerve Dysfunction=====
−* Facial nerve dysfunction is common in the horse.
−* It is readily identified by one or more of the following:
−** A lip droop
−** Muzzle deviation
−*** Deviation is towards the normal side.
−** An ear droop
−* Early or mild dysfunction may be reflected by:
−** Slight changes to nostril size
−** Nostril flare
−** Reduced ear movements in response to audible stimuli
−* The branch of CN VII supplying the muzzle and nostrils crosses the vertical mandibular ramus and the surface of the masseter muscle.
−** A lesion to that side of the face, for example a kick, may cause signs confined to the nose.
−** Alternatively, a more central lesion will give both ear and nostril signs.
−=====The Palpebral Reflex=====
−* The palpebral reflex examines the function of both CN V (afferent) and CN VII (efferent).
−* The reflex is elicited by lightly touching the eyelids and watching for reflex closure.
−[[Category:Cranial Nerve Examination - Horse]]
===[[Face Sensation]]===
===[[Face Sensation]]===
−===[[Vestibular System Examination]]===
===[[Vestibular System Examination]]===