CHAPTER 22: – NON-INFECTIOUS DISEASES OF THE CENTRAL NERVOUS SYSTEM
Introduction
Two common symptoms of nervous system dysfunction are . Injury or disease in either the brain or the spinal cord can result in one or both of these conditions being apparent. and
Ataxia is a term used to describe general
of muscle contraction
and/or movement and may involve a loss of proprioception. Dysmetria is used to describe uncoordinated movement where the animal has difficulty judging the ____ a limb has been moved or has difficulty determining the amount of force necessary to move a limb to a set point. Hypermetria is clinically seen as an exaggeration of the swing phase of the stride, where the limb is lifted much higher off the ground than is normal or necessary. Hypometria is usually seen as toe-dragging, stumbling or knuckling at the fetlock, as the limb is not lifted high enough to clear the ground.
Head Trauma (Traumatic Brain Injury)
Trauma to the head is usually acute and can easily occur in a number of circumstances. Kicks or other blows to the head from other horses, running head first into a wall, trailer accidents, rearing and hitting the head on the ceiling, or rearing, falling over backwards and hitting the head on the ground or struggling from an entrapment can all cause injury to the sensitive material that make up the brain. Brain injury can result from direct insult by the skull itself or osseous fragments, from a foreign object or forces upon the brain. The skull protects the brain from much of the mild trauma that the head may be subject to, but the hardness of the skull may contribute to the damage. When a moving object makes contact with the stationary head the area of brain injury is most likely to be under the site of impact. This type of brain injury is called . When the moving head impacts a stationary object the brain experiences rapid deceleration and bangs off of the inside of the skull at the area of impact, then bounces in the opposite direction to bang into the inside of the skull at a point opposite to the initial site of impact. This type of brain injury is called and is characterized by two or more areas of injury in unassociated areas of the brain. There are two common patterns of brain injury associated with head trauma; diffuse injury & focal injury. Diffuse axonal injury occurs as a result of forces that cause different parts of the brain to move at different speeds. This causes tearing or stretching of the axons within the brain thereby breaking down the communication pathways between neurons of the brain. Diffuse axonal injury is commonly seen in motor vehicle accidents
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