What anxiety meds help my senior dog with dementia and pacing?

I am so sorry you are having to go through this with little Chili. Neurologic disease in elderly pets can be difficult to treat, understand, and very hard to watch, just like with people. It sounds like her seizures are well-controlled with the Keppra, but she is displaying additional neurological symptoms: pacing, circling, confusion. I am not entirely convinced these are all due to anxiety though.

Usually neurologic disease in elderly dogs is due to only a few things: metabolic disease (liver, kidney, or diabetic issues), vascular events (strokes), or a brain tumor. If you have ruled out metabolic disease, which I'm sure your vet has, the other two diagnoses carry a very guarded prognosis. My concern is that the symptoms you are seeing are likely the result of progressive disease due to one of those two possible causes. While anxiety medication might help some, I fear that it's not going to give you or Chili the results for which you're hoping.

In this case, it's important to think about quality of life for Chili: what's fair to her? If adding in an anti-anxiety medication helps her resume normal activities where she goes back to being Chili and doing the things that make her "Chili," fantastic. If not, it may be time to make some difficult decisions about what's best for her.

If you do decide to pursue an anti-anxiety medication, your vet might consider Selegiline (specifically for cognitive dysfunction in people, not a lot of reported success in animals), Clonazepam (in the valium and Xanax family, but slightly different), or Clonidine (a blood pressure medication, also used to treat anxiety) in combination with an anti-depressant, such as Prozac. All of these would require careful monitoring and consideration in combination with the Keppra. Whatever you decide, best of luck to you and Chili!