I am sorry that you have been waiting for a response. I recently just logged onto the site and noted that your question hasn't yet been answered. I am a licensed veterinarian with over 25 years’ experience and would be happy work with you if you are still needing assistance.
It is not uncommon to see signs of senility in older cats displayed by a variety of symptoms including wandering aimlessly, staring off in space, seeming unaware of surroundings, night howling or hypervocalizing, having changes in sleep wake cycles, seeming slightly disoriented at time and urinating and defecating outside the litter box intermittently. This is referred to as cognitive dysfunction syndrome (CDS).
Cognitive dysfunction syndrome is a well recognized disorder in aging dogs and cats, however so many other health issues that occur as pets age sometimes interfere with our recognizing it especially in it's early stages. If she hasn't had a physical exam recently, I would recommend one just to make sure your vet cannot identify any other underlying problems. In particular, hypertension and an overactive thyroid can produce symptoms much like CDS. There are supplements and other practices that can be helpful to improve these signs and slow the progression of decline, but it is necessary to rule out any underlying health issues first. Below are a few things that might help:
Feeding a high protein meal before bedtime (this replaces the dinnertime meal)
Nightlight and put near the litter box and food,
feliway diffusers - Feliway is a synthetic pheromone that mimics the natural chemicals that a cat secretes. It creates a comforting, reassuring feeling that has a calming effect to cats in stressful situations such as transport, hospitalization, veterinarian visits, boarding, new environments, pets or people. Feliway® is a product that can be sprayed or used as a room diffuser. It can be purchased through veterinarians and pet stores. LINK HERE
Omega 3 fish oils - (in higher concentrations) - The active ingredient of fish oil is EPA (Eicosapentaenoic Acid) and DHA (Docosahexaenoic Acid). You just want to make sure you are seeing those on the label as an ingredient and not just the words "fish oil" as these are the important part of the fish oil and not all fish oil capsules have them in it, especially the cheaper ones. Aim for 150 mg of EPA and 100 mg of DHA. There is a large range of safety and it doesn't have to be that amount exactly but this gives you some guidelines.
- Melatonin: 1-2 mg at night
- Nu Cat Senior or Senilife for cats - antioxidant support for the brain.
As far as drug therapy, there is an approved medication for use in dogs, but as of yet is not approved in cats although it has been used with fairly good results and no side effects. It is called L-Deprenyl or Anipryl® and works by increasing the important brain chemicals that decline with age. It also helps to helps reduce amounts of free radicals in the brain which can be damaging to the remaining tissue. This is an option if the supplements are not helping.
I would work with your vet to try incorporating the above mentioned ideas, maybe incorporating one at a time.
Finally, you can help stimulate her brain by simply providing the daily enrichment and stimulation at a level that an older cat can handle. Play with her and keep her senses sharp. Her brain needs the same type of support as the rest of her aging body.
Here are a few links with more ideas to help with environmental stimulation and enrichment:
Indoor Pet Initiative: http://indoorpet.osu.edu/
I hope this is helpful. Please let me know if you have ANY other questions. My goal is to give you 100% satisfaction and if you are not yet satisfied, please reply so I can clarify for you.