# Canine Ataxia



## pitbullmamanatl (Jun 1, 2010)

By Dr. Nastasha Olby
As nearly everyone involved with American Staffordshire terriers knows, the breed has been afflicted with an inherited disease that causes progressive incoordination (ataxia). Different areas of the nervous system control coordination and it is important to understand that disease of any type (e.g. cancer, infection or degeneration) affecting these areas of the nervous system can cause incoordination. The important areas of the nervous system for control of coordination are the cerebellum, the vestibular system and the spinal cord, and all three areas interconnect. This article attempts to briefly describe and explain the different signs that can occur when disease affects these areas. The typical diagnostic approach to a dog presenting with ataxia is also explained.

a) The cerebellum is responsible for controlling the rate, range and force of movements and when it fails, animals become incoordinated (ataxic) and tend to stand with their feet far apart to stabilize themselves. They may develop a high stepping gait (also called dysmetria or goose stepping because of its appearance), and they find it difficult to judge a movement and so develop a sign called intention tremor. This is most obvious when an animal is really intent on a task such as eating and their head will literally tremor from side to side making it difficult for them to accomplish the task. The classic signs of cerebellar disease can therefore be summarized as wide based stance, ataxia characterized by dysmetria, and intention tremor, and the signs are readily recognized by veterinarians. As the cerebellum does not control strength animals with cerebellar disease are not weak. However, the cerebellum does connect closely with the vestibular system and cerebellar disease can cause signs of vestibular disease (described below) in addition to the more typical cerebellar signs. This can produce some confusion when evaluating animals.
b) The vestibular system involves both a sensory system in the inner ear and its projections to the brainstem and cerebellum. The vestibular system compares information generated as a result of head movements and the force of gravity from both inner ears and aligns the head and body in a normal posture against gravity. It also ensures that your eye movements respond to head movements in such a fashion that you can fix on an image when your head is moving. Signs of vestibular disease are typically worse on one side than the other (except in the case of degenerative diseases), for example, a middle ear infection can spread to the inner ear and affect the information coming in from that side. Typical signs include a head tilt (that can be dramatic); flicking of the eyes from side to side or up and down (nystagmus); abnormal position of the eyes (one eye looks down while the other looks straight ahead: strabismus); vestibular ataxia (incoordination) characterized by leaning, falling and circling to the side of the head tilt (the body is trying to align itself with respect to gravity based on wrong information); and nausea. If the part of the vestibular system in the brainstem is involved, you can also see weakness, and changes in consciousness, sometimes leading to coma.
c) The spinal cord conveys sensory information on the position of the limbs to the brain. Damage to the spinal cord interrupts this information causing the final form of ataxia: sensory ataxia. Affected animals will cross their legs when walking, giving them a drunken appearance, and may walk on the back of their paws because they fail to correct paw position properly. Typically the animals will also be weak.

My usual approach as a neurologist to a dog presenting with ataxia (incoordination) is to complete a careful neurological examination and from that distinguish between cerebellar, vestibular and sensory ataxia. This allows me to localize the problem to one area of the nervous system and I then use other information (e.g. how quickly did the signs come on, are they getting better or worse, how old is the animal, what other medical history does it have), to generate a list of possible causes. This in turn allows me to recommend further diagnostic tests (which in neurology often means imaging the brain using a CT scanner or MRI, and taking a sample of spinal fluid). Once these tests have been run we arrive at a diagnosis and determine the most appropriate treatment.

The inherited neurodegenerative disease that has emerged as a problem in Amstaffs affects the cerebellum, but involves in particular the portion of the cerebellum that connects to the vestibular system. We therefore see a mix of vestibular signs (e.g. nystagmus) and cerebellar signs. This can lead to a failure to consider this as a possible diagnosis (it does not appear like the most classic cerebellar disorder) and to the possibility of pure vestibular diseases representing the more sinister diagnosis of hereditary ataxia.

We do commonly see vestibular syndromes that are much less concerning in Amstaffs. One is 'idiopathic vestibular syndrome.' This is a disease of the inner ear for which the underlying cause is unknown but the brain itself is not involved. This disease causes very sudden onset of a head tilt, falling, nausea and nystagmus: the signs can be very dramatic and it is typical for an owner to think their dog has had a stroke. There is no curative treatment and in general the signs resolve or greatly improve on their own within 2 - 4 weeks. We will usually check a thyroid panel and blood pressure in affected dogs, but they are often normal and imaging of the brain and CSF analysis are normal. We also see infections of the middle ear (otitis media/interna) cause very similar signs of head tilt, falling and nystagmus. Often the animal's ear is painful. This can sometimes be diagnosed by a very good examination of the ear, but it can be difficult to see as far as the middle ear in dogs and a CT scan of the head may be necessary. This disease must be treated with antibiotics and sometimes surgery is indicated to remove all the infection and inflammation from the middle ear.

Both of these vestibular diseases are sometimes associated with paralysis of muscles of the face on the same side as the head tilt: called facial paralysis. This results in drooping of the face, inability to close the eye, accumulation of food in the cheek and drooling, all on the same side as the head tilt. In the case of otitis media, the nerve running to the facial muscles also runs through the middle ear and can be coincidentally affected by the infection. In the case of idiopathic vestibular syndrome, sometimes we see idiopathic facial paralysis at the same time. In this latter instance we suspect that the unidentified disease process affecting the vestibular system is also affecting the facial nerve, although more usually these idiopathic disease occur separately. Importantly, facial paralysis is not a component of hereditary ataxia. If you notice your dog is incoordinated, the first step is to take them to your veterinarian so that they can do a neurological examination. If they suspect a spinal cord or brain problem, they may then decide to refer you to a neurologist to complete the more specialized diagnostic tests and get a definitive diagnosis from which the best treatment can be planned. A full list of neurologists is available on the following website: www.acvim.org. If you are not interested in a full neurological work up, they may be able to discuss the possible causes and the treatment and prognosis (outcome) for each of these diseases to help you to make a decision about the next step.


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## angelbaby (Feb 4, 2010)

Good post , makes me wonder did we miss this with rocky? alot of the symptoms are what he had although they fit the anti freeze poisoning as well that the vet suspected . Feel kinda bad what if it was this and we didnt know to check for it , the vet never mentioned anything like this Good post though one to keep in the back of my head for future refrence to , hopefully never needed.


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## pitbullmamanatl (Jun 1, 2010)

angelbaby said:


> Good post , makes me wonder did we miss this with rocky? alot of the symptoms are what he had although they fit the anti freeze poisoning as well that the vet suspected . Feel kinda bad what if it was this and we didnt know to check for it , the vet never mentioned anything like this Good post though one to keep in the back of my head for future refrence to , hopefully never needed.


Anything is possible girl. You did the right thing though xoxox


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