There are a few things that can cause a dog to have dizziness including ear infections, vestibular disease, organ dysfunction, seizure and heart issues.
It’s possible your dog is suffering from vestibular disease. Symptoms include standing with legs spread out, swaying, head tilt, abnormal eye movement, walking sideways, falling over and may include vomiting. There are a few things that can cause this condition such as an ear infection, some medications and old age. Have your Vet check your dog for this condition especially if your dog has other symptoms. Here are some great sites on this condition:
The good news is that if this is the problem and it is due to old age, the condition normally resolves itself over a few weeks. Your vet will most likely prescribe dramamine or bonine to help with the symptoms. You can read about dramamine and bonine usage, precautions and dosage here:
Organ dysfunction such as liver and kidney failure might also lead to disorientation and even seizures. Usually there will be other symptoms such as vomiting and diarrhea associated with kidney and liver failure.
Your dog may be experiencing seizures even though there was no drooling or shaking. Seizures can manifest in many different ways. You can read about seizures and the different kinds here:
A dog may also "faint" in which they fall to the ground usually on their side, stare straight ahead and seem paralyzed which indicates a heart problem.. This is called syncopy and can be read about here:
I would have your dog seen by your vet as soon as possible and limit your dog's activity until she can be seen in case it is heart related and not seizure related. If you have a video camera, and this happens again, taping the behavior will help your vet determine the cause.
I wished I could tell you definitely which was the cause, but your vet will need to do a physical exam to determine the most likely cause.
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