The canine vestibular system or apparatus is an organ of balance. The vestibular system senses the position of the head and body in space, in relation to gravity and movement.
The purpose of the vestibular system is to synchronize eye movements and maintain posture, balance, and coordination.
Simply put, the system tells the dog’s brain if the dog is standing, sitting down or lying down, falling, spinning in circles, etc. It keeps the body in balance and prevents the dog from falling over.
The vestibular system consists of sensors (deep inside the inner ear adjacent to the hearing receptors) and a specialized control center (at the back of the brain).
The balance sensors detect the position of the head in space while the dog is standing or when he is moving. The information on the position of the head is converted into electrical signals which are sent to the brain.
Vestibular information is processed in the the balance control center which is in the lower portion of the brain in the brainstem and cerebellum.
The processed information is then sent out as messages to the rest of the body to coordinate the body so that the dog is kept upright.
Messages are also sent to the muscles in order to control movement of the eyes to change the position of the eyes according to the position of the head.
Canine vestibular disease refers to any abnormality of the dog’s vestibular system.
Vestibular disease in dogs affects the ability of the dog’s brain to recognize abnormal body positions. In addition, vestibular disease affects the brain’s ability to correct these abnormalities.
There are two forms of canine vestibular disease – Central vestibular disease and peripheral vestibular disease.
Central vestibular disease occurs as a result of an abnormality within the brain.
Peripheral vestibular disease occurs due to inner ear abnormalities. Most cases of vestibular disease in dogs are peripheral.
Symptoms of Canine Vestibular Disease
If a dog has a problem in his vestibular system, he cannot properly perceive his orientation, i.e. he will not know which way is up; he may not know if he is standing up straight or slanted, and he will feel very dizzy.
Both central and peripheral vestibular disease in dogs have symptoms such as:
- Head tilt
- A loss of balance and coordination (ataxia)
- Nystagmus – abnormal eye movements – the eyes can go side to side (horizontal), up and down (vertical) or rotary (circular)
However, there are certain different symptoms that differentiate peripheral vestibular disease from central vestibular disease in dogs.
Firstly, in peripheral vestibular disease, the abnormal eye movements are limited to rotary or horizontal nystagmus, not vertical. However, dogs with central vestibular disease have horizontal, rotary and vertical nystagmus.
In addition, dogs with peripheral vestibular disease usually do not have body weakness and there are no mental changes.
Rolling is rarely observed. However, they may have facial paralysis so that one side of the face seems to be drooping.
For dogs with central vestibular disease, they tend to roll, have poor foot placement with a lot of staggering or stumbling.
They also have weakened jaw, and possible head tremor. Finally, they may suffer from depression.
Onset of symptoms can be very sudden. The signs of head tilt, circling and staggering may lead many dog parents to suspect stroke. However, strokes are rare in dogs.
Causes of Canine Vestibular Disease
Most cases of vestibular disease are the result of a condition known as “idiopathic vestibular syndrome”, which is a disease of unknown cause (idiopathic).
Sometimes this condition is also referred to as “geriatric vestibular syndrome”, or “old dog vestibular syndrome”.
This usually affects middle-aged to older dogs (mean age 12.5 years).
The onset is sudden and the dog shows symptoms of head tilting, staggering and stumbling, erratic eye movements, and sometimes vomiting.
At times, some such symptoms can be serious and incapacitating. Signs peak in 24 hours and most dogs improve spontaneously within 2 weeks, although some dogs may have a slight but permanent head tilt.
Other causes of vestibular disease in dogs include:
- Middle or inner ear infections
- Toxicity (e.g., use of toxic antibiotics in the ear)
- Metabolic diseases (e.g. hypothyroidism)
- Trauma to the head
- Brain diseases, such as encephalitis (inflammation of the brain) and brain tumors
Diagnosis and Treatment of Canine Vestibular Disease
Initial diagnosis is based on recognition of the specific signs.
However, to determine if the dog is suffering from peripheral or central vestibular disease, further tests (such as blood tests, x-rays, CT or MR) are needed to see if a tumor or brain abnormality is present.
The dog is said to have peripheral vestibular disease if a brain tumor or abnormality is ruled out.
Initial treatment of both peripheral and central vestibular disease is to reduce the symptoms so that the dog can function normally.
For example, medications will be given if the dog suffers from dizziness or vomiting caused by motion sickness.
Then further treatment is needed to address the underlying root cause.
For example, a dog suffering from central peripheral disease caused by a brain tumor will need treatment for the brain tumor which may be surgery, radiation therapy and/or chemotherapy.
Dogs suffering from peripheral vestibular disease usually can recover in about two weeks. After recoverly, some dogs may experience a slight but permanent head tilt.
Dogs suffering from central vestibular disease may not recover totally.