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| ==[[Body, Spinal Cord and Limb Neurological Examination - Horse]]== | | ==[[Body, Spinal Cord and Limb Neurological Examination - Horse]]== |
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− | ===Conscious Proprioception Testing ===
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− | * It is possible to test a horse’s conscious proprioception by altering the position of the limbs in space.
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− | ** Horses should normally replace their limbs to the normal position within a few seconds.
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− | *** There is a degress of individual variability, however, and the test can be difficult to interpret.
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− | * Tests can also be performed by walking or trotting a horse and then suddenly stopping.
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− | ** The animal should be observed to see how quickly it replaces its legs in a normal position.
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− | ===Gait===
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− | * Gait is a combination of higher control of motor function and unconscious proprioception.
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− | * During assessment of gait, the examiner is looking primarily for evidence of '''ataxia''' and/ or '''weakness'''.
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− | ** Each leg should be assessed in turn.
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− | * Defects may be graded on a five-point scale (the Mayhew scale).
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− | ** 0 is normal and 5 is recumbent.
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− | ====Ataxia====
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− | * Defects in unconscious proprioceptive pathways result in ataxia.
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− | ** These pathways originate in muscle spindle stretch receptors and golgi tendon organs.
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− | ** Impulses are relayed via peripheral nerves to the spinal cord.
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− | ** Signals then ascend in pathways to the cerebellum.
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− | *** Primary cerebellar diseases in horses are rare, but classically cause incoordination of the head and limbs.
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− | **** Weakness is not a prominent feature.
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− | **** The cerebellum communicates with the vestibular nuclei, and so cerebellar diseases may sometimes present with vestibular signs.
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− | * Manifestations of ataxia:
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− | ** Exaggerated movements - hypermetria
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− | ** Reduced movements - stilted hypometric movements
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− | ** Both exaggerated and reduced movements - dysmetria.
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− | * Animals may also
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− | ** Sway
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− | ** Place their feet abnormally
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− | *** Horses cross or weave their feet, with abnormal abduction or adduction.
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− | * Signs of spinal ataxia may be exaggerated by lifting the horse's head.
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− | ** This is beacuse it removes the horizon.
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− | ** Similar responses can be generated by walking up and down slopes.
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− | * Circling the horse can also reveal ataxia.
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− | ** The horse may plant its feet and rotate around them without placing them properly.
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− | ** Outward rotation of the pelvic limbs is also a common sign.
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− | *** The term for this is "circumduction".
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− | * Unconscious proprioception may also be tested by backing the horse.
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− | ** Normal horses back with a diagonal gait.
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− | ** Horses with spinal ataxia will often pace when backing.
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− | ====Weakness====
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− | * Weakness usually manifests as toe dragging, stumbling, or knuckling over.
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− | ** It is a good idea to look closely at the horse’s hooves to see if any are abnormally worn.
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− | * Weakness may be caused by dysfunction of either the upper or lower motorneurons.
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− | ** Lower motor neuron weakness.
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− | *** Accompanied by:
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− | **** Muscle flaccidity
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− | **** Muscle atrophy if chronic
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− | *** May sometimes appear similar to lameness.
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− | ** Upper motor neuron weakness.
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− | *** Presents as a lack of control of limb muscle movement.
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− | *** Tested most easily tested by pulling the tail during walking.
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− | **** Pulling the tail while stationary probably primarily tests lower motor neuron control and muscular strength of the pelvic limb.
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− | [[Category:Neurological Examination - Horse]]
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