I am sorry to hear that Miss Kitty may be experiencing seizures. I understand that at her age you are most concerned with keeping her comfortable and happy rather than putting her through lots of extensive testing and treatment, which is very reasonable.
Seizures are not something we treat surgically, so rest assured that would be anything that would be recommended.
Cats are very sensitive to drugs in the benzodiazepine family (like valium or xanax), some may have an idiosyncratic reaction, developing severe liver disease and necrosis with their use, especially if given at higher doses or chronically. Some cats seem to tolerate them fine, whereas others cannot handle even a small dose, and there is no way to tell before giving the drug which cat will react and which one won't. So in general they are not the drug of choice with seizures in cats, especially if we aren't sure why the seizures are happening.
There can be several reasons for seizures.
The most common reason for seizures in young cats 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 young animals, and Miss Kitty is older, so it is not likely that she is epileptic.
We do believe that there is a genetic basis for epilepsy as certain breeds are more commonly afflicted and siblings will often have them as well.
Other cause for seizures in cats include are viral, bacterial, parasitic or fungal infections, metabolic diseases (liver or kidney disease, diabetes) 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 cats are sick or abnormal other than during the seizure.
Most cats do behave normally after they gather themselves after a seizure, though they will often be hungry and thirsty and may feel anxious because they do not remember what happened during the episode.
Some cats 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 Feliway or pheromone impregnated collars to keep her calm. Was there any stressful event that you know of that led to this episode?
Exercise should be kept at normal levels. Exercise is a great way to naturally relieve stress and increase positive endorphin levels in the brain.
Ideally she should see her veterinarian for an examination and bloodwork to look for underlying organ disease, feline leukemia or feline immunodeficiency virus as well as toxoplasmosis. We do want to make sure there are no underlying problems that need to be addressed. I understand that you may not want to stress her with a veterinary visit and blood tests, but if she has poor organ function that is something we need to know before prescribing medication to help control her seizures. So perhaps limiting blood tests done to the bare minimum could be done, that way a small amount of blood should be sufficient for testing.
If she has more seizures today, or if she is not eating and drinking or is behaving abnormally then an emergency visit today is best.
If a cat has more than one seizure in a month or more than one in a day, even if it has been months since the last one I recommend medical therapy to prevent seizures.
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.
Phenobarbital is very effective in most cats at preventing seizures and if used at appropriate levels it rarely causes any organ damage. If you aren't comfortable with that drug there are others such as Keppra (levetiracetam) or Zonegran (zonisamide) that your veterinarian can prescribe. These newer drugs are reported to be less stressful on the organs but even they are not totally without problems. About 1/2 of the cats on zonisamide do have side effects, including diarrhea, lack of appetite, vomiting and incoordination. I find most cats handle phenobarbital better long term after the first few weeks of adjusting to the drug.
As with any medical condition we must weigh the positives and negatives of using a particular medication. Minimally if you choose nit to have her examined and blood tests run I would try and decrease her stress levels as well as using a diet without glutens, dyes or lots of chemical preservatives.
In many cases we never completely stop the seizures, but they should be much fewer and much less severe.
Please let me know if you have any further questions.