Paradoxical Vestibular Disease
Vestibular disease is typically found in dogs with tumors of the choroid plexus. A component of the central vestibular system, the choroid plexus is the area in the cerebral ventricles of the brain that produces cerebrospinal fluid. The key sign of vestibular disease is a head tilt. The more common vestibular disease produces a head tilt toward the side of the brain with the tumor; paradoxical vestibular disease causes the head to tilt away from the side with the lesion.
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Vestibular System
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The vestibular system is responsible for two very important tasks: it keeps the eyes steady while the head moves to maintain a stable visual image, and it coordinates the position of the head with the rest of the body to sustain balance. The vestibular system is composed of the peripheral vestibular system and the central vestibular system. Paradoxical vestibular disease involves the central vestibular system.
Signs
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Signs of paradoxical vestibular disease include falling, loss of balance, rolling, tilting of the head, circling, nystagmus (eyes involuntarily move in different directions because of loss of ocular muscle control) and one-sided ataxia (instability and clumsy movements). The dog may be nauseated and may vomit. The dog’s head tilts away from the side of the head with the lesion or tumor, in the case of a single lesion.
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Causes
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Paradoxical vestibular disease is typically triggered by a tumor. Other causes include loss of the covering of some nerves, a genetic inability to store certain nutrients, stroke, hydrocephalus (water on the brain), thiamine deficiency, inflammation, head trauma and infection with a virus, fungus, bacteria, parasite or other infectious organisms.
Diagnosis
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Urine, biochemical and blood test results are usually normal. X-rays may not reveal a lesion, but MRI and CT scans are useful in identifying a tumor. Analysis of cerebrospinal fluid and a bone biopsy can pinpoint central vestibular disease, but both of these procedures are risky.
Treatment
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The dog’s movements should be curtailed if it has severe balance and equilibrium problems. The dog should avoid slippery areas and stairs. While the dog will not need a special diet, food intake must be monitored if there is frequent vomiting or the potential for food aspiration (breathing in food particles) because of a severe head tilt or balance issues. Surgery may be necessary if the tumor can be removed.
Special Considerations
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Dogs may need fluid replacement in case of frequent vomiting. Any drug that causes dizziness or balance problems should be stopped. Infections and inflammation must be treated, and fractures should be repaired.
Follow-up
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The dog should have periodic neurologic re-examinations. His mental status may decline. Fatal brain herniation, pressing aside blood vessels in the brain, may occur due to tumor growth or fluid build-up. Dogs with central vestibular problems generally do worse than dogs with peripheral vestibular problems.
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References
- Photo Credit Dog Head image by Vincent Duprez from Fotolia.com
