Ataxia is defined as the loss of control over body movements. The general lack of coordination and an inability to stand or walk effectively are the characteristic symptoms of this condition. Ataxia is a sign of problems in nervous system that produce loss of coordination of the limbs, head, and/or trunk.
There are 3 different clinical types of this condition including,cerebellar, sensory (proprioceptive), and vestibular. Each type of ataxia will be manifested by impaired coordination when walking or standing. While all three types produce changes in limb coordination, changes in the dog's neck and head movement are characteristic of cerebellar and vestibular ataxia.
Proprioception is the sense that indicates whether the body is moving with the required effort, and also where the various parts of the body are located in relation to each other. Sensory (proprioceptive) ataxia occurs as a result of slow compression of the spinal cord. The result is misplacing the feet and progressive weakness as the condition advances. Causes of sensory ataxia include brain diseases, disorders of the brain-stem, which is the stalk-like structure of the base of the brain that attaches to the spinal cord, disorders of the spinal-cord and disorders of the peripheral nerves outside of the brain and spinal cord.
Vestibular ataxia occurs when there is a problem with the nerve connections of the inner ear to the brain. The vestibular system senses the position of the head and body in space, in relation to gravity and movement, helping the animal maintain balance and coordinate eye movements with movement of the head. The vestibulocochlear nerve carries information concerning balance from the inner ear to the brain. Damage to the vestibulocochlear nerve can cause changes in head and neck position, as the affected animal may feel a false sense of movement, or may be having problems with hearing. Symptoms of vestibular ataxia include leaning, tipping, falling or rolling over accompanied by changing types of eye movements, sensory deficits, weakness in the legs (all or one sided), multiple cranial nerve signs, and drowsiness, stupor, or coma.
Cerebral ataxia is the damage to cerebellum — part of brain that regulates the control and coordination of movement. This condition is reflected in uncoordinated motor activity of the limbs, head and neck, taking large steps, stepping oddly, head tremors, body tremors and swaying of the torso.
Common symptoms that are associated with ataxia include
Weakness of the limbs (one, two or all, or only hind legs or the legs on one side of the body)
Tilting head to one side
Trouble hearing – non-responsive to being called to at normal voice pitch
Stumbling, tipping over, swaying
Excessive drowsiness or stupor
Changes in behavior
Abnormal eye movements – may be due to false feeling of movement, vertigo
Lack of appetite due to nausea (symptom of motion sickness from loss of internal equilibrium [balance])
