Hello, I'm Dr. Kara. I have over 20 years of experience as a veterinarian and I'd like to help with your concerns about Margot.
Your description sounds very much like seizure activity given that she was not aware of anything around her, her hind legs had some repetitive motions and she was trembling as well as her now normal behavior.
Seizures are rhythmic, repetitive, muscle movements which the dog is unable to control and often loses consciousness during. Many dogs will repeatedly have chewing motions and/or leg motions and can lose urine and stool control. But not all dogs lose stool or urine continence, and not all dogs will have chewing motions either. The key is repetitive muscle movements and loss of awareness with a fairly quick recovery.
There can be several reasons for seizures.
The most common is idiopathic epilepsy. That means that we don't know why but a
circuit of sensitive neurons in the brain gets stuck repeatedly firing. Epilepsy occurs most frequently for the first time in dogs 6 months to 6 years of age so she is in the right age range for this to be the cause of her seizures. We do believe that there is a genetic basis for dogs to have epilepsy as certain breeds are more commonly afflicted and siblings will often have them as well. If mom carried some of the genetics for epilepsy she may not be affected. But if she bred with a male that also carried some of the genetics for epilepsy (and he may not have been affected either) then together if the wrong combination of genes resulted we could get puppies with epilepsy.
Other causes of seizures are viral, bacterial, parasitic or fungal infections, metabolic
diseases leading to waste products building up and affecting brain chemistry,
low blood sugar, or even granulomas or masses in the brain.
Most of the other disease processes that cause seizures cause other symptoms, those dogs are sick or abnormal other than during the seizure.
Some dogs with lower than normal seizure thresholds will seizure in response to
being exposed to artificial colors, preservatives or gluten. So you might wish to feed her a diet without artificial dyes or flavors and one that is wheat free. Blue Buffalo purports to produce these sorts of foods.
Decreasing stress is also a way to avoid seizures so if you know an event will be stressful for her avoid it if possible. You can also use calming sprays such as DAP (dog appeasing pheromone) or pheromone impregnated collars to keep her calm.
Exercise should be kept at normal levels. Exercise is a great way to naturally relieve stress and increase positive endorphin levels in the brain.
In a patient that has had a possible seizure episode I would have your veterinarian examine her, check a biochemistry profile to look at organ health and a complete blood count. We do want to make sure there are no underlying problems. It is possible for a dog to have a seizure and never have another one so if she seems perfectly normal and back to herself you can take a watch and see approach and if she has another one then pursue an examination and blood tests.
If her seizures become more frequent than once a month or more than one happens in a day, even if it has been several months since the last one, I would discuss medication to prevent them. The reason for that is the likelihood of status epilepticus (one seizure after another) and possible brain damage is higher with those scenarios and we wish to avoid that.
Please let me know if you have any further questions